Volume 105

Number 3

Fall 2019

Journal of the

WASHINGTON

FEB 05 2020

ACADEMY OF SCIENCES

Editor’s Comments S. Howard

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Volume 105

Number 3

Fall 2019

Journal of the

WASHINGTON

ACADEMY OF SCIENCES

Editor's Comments S. Howard

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ISSN 0043-0439 Issued Quarterly at Washington DC

Fall 2019

EDITOR’S COMMENTS

Presenting the 2019 Fall issue of the Journal of the Washington Academy

of Sciences.

This issue of the Journal presents three papers. We have a slightly

new format. The general information pages have moved to the front of the

issue followed by the research papers. At the end is our first SciBite

contribution. First up is an astronomy paper on NGC 4622, a galaxy. The

characters NGC stand for New General Catalog, an astronomical catalog

that contains a numbering method for celestial objects. The galaxy

discussed in the paper is number 4622 in the Catalog.

Next is another astronomy paper on the possibility of living in lava

tubes on Mars.

The last paper has two parts: a background article that precedes the

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discovered in the Milky Way. We end with an AstroBite on this topic.

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NGC 4622: Unusual Spiral Density Waves and

Calculated Disk Surface Density

Gene Byrd*, Sethanne Howard**

*University of Alabama (emeritus)

**US Naval Observatory (retired)

Abstract

NGC4622 was initially known to have a beautiful spiral pattern composed

of two trailing spiral arms. The arms are outlined by stellar associations,

a prototypical two-armed density wave pattern. Later Byrd et al (2008 and

references) discovered that the outer pair leads (the opposite of what was

previously thought) along with a new single trailing inner arm. It is shown

here that NGC4622 has an unusual pattern with a textbook density wave

arrangement of stellar associations relative to stellar arms. Also,

NGC4622’s unusual flat then rising rotation curve, its co-rotation radii,

and arm inclinations can be used to calculate the surface mass density of

the disk in both arm regions. The surface density is comparable to that in

our Milky Way out to ~5 kpc then it rises to much larger values at 8 kpc

radius. So, NGC 4622 is an even more exceptional galaxy with a flattened

dense outer disk deduced from its beautiful outer leading arm pair and

rising rotation curve.

Introduction

IN HIS EXCELLENT TEXT, Zhe Physical Universe, Frank Shu (1982) included

a photo of NGC4622 describing it as “a beautiful spiral pattern composed of

two trailing spiral arms.” The arms are outlined by “brilliant associations”

like “beads on a string” 7.e., it is a prototypical example of a two-armed

density wave pattern. Previous work (Byrd ef a/ 2008 and references)

discovered that the outer pair leads (the opposite of what was previously

thought) along with a new single trailing inner arm (not mentioned by Shu).

As discussed here, NGC4622 is a clear example of an unusual density wave

patterns with two kinds of arms. We use NGC4622’s unusual rising rotation

curve, its co-rotation radii, and its arm inclinations to calculate the surface

density of the disk in the two arm regions.

Fall 2019

Arm sense from positions of associations relative to stellar arms

In Figure 1 an outer pair of arms (1 and 2) winds outward clockwise

(CW). There is an inner single arm (3 in right hand frame) which winds

outward counterclockwise (CCW). According to conventional density wave

descriptions, the outer pair should trail outward CW, opposite a CCW sense

of disk orbital motion.

NGC 4622

HST e WFPC2

* ~ 5000 parsecs

20,000 light-years ”

Ene Sa aes ad aes Ps

Figure 1. HST images of NGC4622: Left, color. Image with compass points on sky. And

scale 5000 pe =29.7 arc sec (”). Right, a sharper view of associations (blue white) and

stellar arms (tan).

Examining the right image of Figure 1, dark gas/dust cloud

silhouettes are much clearer on the SE side. That edge is thus thought to be

turned toward us and the NW away at an angle of ~19°. Radial velocity

observations indicate that the NE upper end of node line recedes and the SW

end approaches, so orbits are clockwise (CW) on the sky. As discussed in

our earlier papers, the outer pair of arms leads outward CW and the single

inner arm trails, contrary to the usual theoretical expectations.

Leading and trailing arms and their co-rotation radii

Arm inclinations and co-rotation radii CR (which occur where the

orbital Q! equals the arm pattern speed, Qp) can be determined from the IVB

Fourier components. The boundary between leading and trailing arms is

observed to be near radius, r = 25 to 30 arc sec (”). In Figure 2 NGC4622’s

rotation curve (v in km/sec) 1s fairly flat with increasing radius out to ~30”.

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In this region, the orbital angular rate (Q = V/r) declines with r. At larger r,

an unusual rising rotation curve appears so that Q rises with increasing

radius. (Byrd et al 2008 and references therein). A trailing arm would be

created inside ~30” where the Q declines with radius and a leading arm pair

outside ~30” where the Q rises.

Figure 2—Measured NGC 4622 orbital rotation curve (speed, V, in km/sec) versus radius

(r in ”) (See Byrd et al 2008 and references therein).

Stellar association locations relative to the older stellar arms provide

additional support for the unexpected arm winding. In Figure 1, (right frame)

the “beads on a string” NE arm 1 winds outward CW in the HST image. Gas

clouds enter the more slowly turning stellar arm 1 on the convex side outside

the outer co-rotation radius, CR2, at 36.4” (5.94 kpc) marked as the solid

circle in Figure 3. These clouds later become short-lived associations as seen

on the concave side of arm | in the image. At immediately smaller radii than

36.4”, the associations of arm | are on the convex side as the arm catches up

to the slower gas clouds which light up on the other side. The solid CR2

circle and orbital motion arrows outside and inside relative to CR2 are

shown in Figure 3. The stellar arm motion arrows are light colored and the

gas cloud motion arrows are dark colored.

Fall 2019

In Figure 3, the inner single arm 3 trails outward CCW from the

center through an inner co-rotation radius (CR1) at 21.3” (3.53 kpc) marked

with a dashed circle. The orbital motion arrows are shown inside and outside

the inner CR1 are included in Figure 3. Unfortunately, in arm 3 of Figure |

the individual associations are not so clear relative to the stellar arm as those

in outer pair of arms. However, position angles of the different [VB color

Fourier arm components also show the cloud/association formation

sequence and permit accurate determination of both the outer CR2 and the

inner CR1 radii.

Arm

ang.

Rate’

Clouds’

orbital: + / Apne.

angual “1 Ji

rate, Be A

V/R

‘

Figure 3. Relative gas cloud and stellar arm positions and motions in NGC 4622 inside

and outside CR1 (dashed circle) and CR2 (solid circle).

Figure 4 shows the peak position angles for the single inner arm one-

fold m = | color component (Byrd ef a/ 2008). The sequence BVI indicates

the position angles of the color components. Going outward, the arm

position angle increases upward, CCW. This arm thus trails. Note that the

Fourier component of the m = 1 IVB sequence does a 180° angle jump at the

inner CR1 radius (21.4”). This matches the theoretically expected behavior

for interior to exterior crossing the inner CR1 for the single arm. Note the

CW IVB downward sequence interior to CR1 as the orbiting disk material

passes the slower inner CR1. The reverse (BVI) sequence downward is seen

where the CW disk orbital motion is slower exterior to the CR1 angular rate.

As shown in Byrd ef al (2008), there is a similar (but inverted)

Fourier component m = 2 IVB order switch at the outer CR2 (1=36.4”) like

the individual associations relative to the stellar arm we discussed in Figure

1. The © must increase outward with radius at the outer CR2, confirming

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the leading outer pair of arms. There is no 180° jump in this case since there

are two symmetrically placed arms.

200

100

@, (degrees)

-100

rie

Figure 4. Position angle, @, of inner single arm shown as Fourier components versus r.

The inner single arm m = | component is shown. Orbital motion is downward (CW),

opposite to the CCW position angle that increases upward.

A smoothed orbital velocity versus radius fit through the Figure 2

data is shown in Figure Sa. The fit requires that the observed derivative of

the angular rate versus radius is zero in neighborhood of 30” between the

single trailing arm and the pair radius, outside this neighborhood it rises.

Hence the trailing and leading senses.

Also used in the fitting are the co-rotation radii and their angular rates

marked in Figure 5b with vertical dashed lines. The extended horizontal

dashed lines from these two indicate the two pattern speeds, 5.87 km/s /” for

CR1 =21.3” and 4.81 km/s/” for CR2=36.4”. With 5 kpc =29.7 ”, these

values correspond to 3.6 kpe and 6.13 kpc.

Fall 2019

v = -1.834E-04r4 + 2.245E-02r3 - 7.328E-O1r? + 7.081E+00r + 1.274E+02

ie)

Orbital Velo

wn (=)

S (S)

° > a0 distatice from Ceriter in 3?c sec” a 28 22

Figure Sa--Plot of v (km/s) versus r (”) of a smoothed Excel 4" order polynomial. The fit

requires that dQ/dr = 0 near r = 30” and v=138 km/s and also includes the co-rotation

radii, angular rates, CR1, (Q = 125 km/s/21.3”) and CR2 (Q = 175 km/s/36.4”). Finally,

extreme Qs (130 km/s/17.5”) and (330 km/s/52”) are also used. Compare Figure Sa to

Figure 2 to see the fit to the data.

7.5 —— y=5,94954E-06x! - 1.19018E-03x? + 7.924465, 02x? - 2.39224E+00x +

7.0 | 3.04699E+01

0 5 10 5 20 25 30 35 40 45 50 59

Figure 5b--Plot angular rate of (km/s) /r (”) of a smoothed Excel 4" order polynomial.

The fit requires that dQ/dr = 0 near r = 30” and v=138 km/s and also includes the co-

rotation radii, angular rates, CR1, (Q = 125 km/s/21.3”) and CR2 (Q = 175 km/s/36.4”).

Finally, extreme Qs (130 km/s/17.5”) and (330 km/s/52”) are also used.

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Inclination of Arms

Arm inclinations (7) are defined either for the single m = 1 arm or the

m = 2 arm pair. These are the acute angles where the arms cross the two co-

rotation circles shown in Figure 3 and at other radii circles also. For

pedagogy we use the notation and refer to some of Shu’s (1982) formulas.

The arm radius of the one-fold arm increases with counter clockwise

position angle, opposite the two-fold arm. The arm inclination definitions

(prob. 12.11 and Eq. 4 Shu) are given by Equations (1) and (2):

kj =——_, (1)

r tani

and

EAN. A275

‘l — Ses Z

anil Aah aA (2)

where A is the wavelength. In typical spiral galaxies the inclination is nearly

constant over the arms (Kennicutt 1981).

Disk Surface Density Calculation Application to NGC 4622

We now calculate the disk surface density of NGC4622. The

dispersion relation provides a condition for stability determined by the

competing self-gravity of surface density 1, velocity dispersion, and orbital

angular rate, Q = V/r, and the shear. The dispersion relation is given by

Equation (3):

(@—mQ) = + ka? -270G|k| (3)

where m is arm multiplicity (See Prob. 12.11 and Eq. 1 in Shu 1982). It turns

out that this relation is valid for winding arms as well as for circularly

symmetric perturbations (Byrd 1995).

Here the epicycle frequency squared is given by Equation (4):

sgl d (4c? 2 dQ

K r —(r rQ \= AQ? + 27rQ— (4)

(Prob. 12.8. Shu 1982). The wave frequency is given by Equation (5):

o=mQQ, (5)

and the arm pattern speed is Qp.

Fall 2019

Equation (3)’s left hand side can be described as the spring constant

for oscillation of stars relative to the arm. If there is no surface density or

velocity dispersion, pure epicycle oscillation is left. For harmonic oscillation

the right side of equation (3) must be greater than zero. Assuming zero, the

minimum disk velocity dispersion parameter for stability is Equation (6):

Qnin ~~. ? (6)

(prior to Shu’s Eq. 3), again also valid for winding arms (Byrd 1995,

equation 12b).

The observed values of arm multiplicity, m, inclination, i, angular

rates, Q(r) and pattern speed, Q,, permit calculation of disk surface density,

uu from the dispersion relation (3). We assume stability over the disk and

substitute equation (6) into equation (3) giving a quadratic equation for disk

surface density. However, since the equation is quadratic, there are two

possible values for surface density for a given (Q - Qp)* . Consequently, we

use Equation (7):

Bieler ear aoa! cure Y

1G m

where, inside the square bracket, for a declining Q with respect to radius, the

second term in the square bracket is positive for radii inside co-rotation and

negative outside. The reverse is true for a rising Q with radius.

As discussed, NGC4622 has two co-rotation radii which are marked

in Figure 5 with vertical dashed lines. From the intersection of these with

the rotation curve, the horizontal dashed lines indicate the two pattern

speeds, Qip = 5.869 km/s /” for CR1 at 21.3” and Q2» = 4.808 km/s/” for

CR2 at 36.4”. These pattern speeds are used in Equation (7) for their

neighborhoods inside and outside the neutral zone respectively.

We use the two-fold arms in the calculation of the disk surface

density in Equation (7). This pair is strong and leads outside the neutral zone.

Inside the neutral zone, the pair is weaker but clearly visible in a two-fold

Fourier I band plot as a trailing pair (Figure 6). The inclination of m= 2 from

23.1” (3.9 kpc) to 48.9” (8.23 kpc), is remarkably constant at i = 7.6° even

crossing the neutral zone at ~3.4 in Figure 7.

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The surface density equations above use the angular rates; inside and

outside the neutral zone radius where r = 30” and v = 138 km/s. Also used

are the inner and outer co-rotation radii along with their pattern speed

angular rates, CR1, (Qp = 125 km/s/21.3”) and CR2 (Qp = 175 km/s/36.4”)

in their neighborhoods. Finally, two extreme orbital angular rates (Q = 130

km/s/17.5” and 330 km/s/52”) are used.

As shown in Figure 8, a declining inner disk surface density is

calculated using the Figure 5b curve and the CRI radius and angular rate.

The surface densities are normal, comparable to those in the Milky Way

Solar neighborhood. However, using the Figure 5b curve and CR2 radius

and angular rate, the outer surface density appears to rise sharply to

unusually large values outward through the leading arm region. The arms

are smooth over the whole region as seen in Figure 6.

eer

rh aan :

‘ wy

Figure 6. — m=2 Fourier component of WFPC2 I band image of NGC 4622. North is

upper right, and East is upper left. The frame covers 1'.50 x 1’.43 stretched to a square to

correct for tilt. Outside the neutral zone, one of the leading CW arm pairs is marked with

white dots. Inside the neutral zone, one of a clear but weaker pair of trailing CCW arms is

marked with black dots. (Byrd et al 2008)

Fall 2019

400

300

200

100

3 32 a! BG 3.8 4

. In r()

Figure 7 Arm pair position angle in degrees versus In radius (”) .

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200

180

160

140

innaE

nia

wEnaE

rca

i Neutral Zone aad

Surface density in solar masses/pc?

[aod

ie nee Rees

4 are CR1 fF a

4 Se et | lee

a ae a eee 16 hag iia

ie bets |e ple tes edt or]

Radius in kpc (1 kpc =6")

Figure 8 Surface density (solar masses/pc’) versus r (”) obtained using: (i) the neutral zone

dQ jdr= 0 and © = 138 km/s /307Gi)| CRI, at O, = 125 kim/s/21.3" and CRZ at Q, = 175

km/s/36.4”; (ii1) Extreme angular rates (130 km/s/17.5”) and (330 km/s/52”); and, finally,

(iv) inclination angle 7.6° from 3.9 kpc to 8.23 kpc where 5 kpc = 29.7 “.

Conclusions

At first examination NGC4622 has a beautiful spiral pattern

composed of two trailing spiral arms outlined by brilliant associations, a

prototypical example of a two-armed density wave pattern. As described in

Byrd et al (2008 and references), a strong outer pair actually leads relative

to the orbit sense and a newly found inner strong single arm trails. It appears

that NGC4622 has an unusual density wave pattern with two kinds of arms

with each having its co-rotation radius. Both the two kinds of arms wind

outward as a smooth log function of radius even across the neutral zone

between leading and trailing arms from 3.9 kpc to 8.23 kpc.

As a consequence of NGC 4622’s unusual rotation curve, the inner

arm trails where the inner angular rate declines with radius. The outer arms

lead where the rate rises. Here it is shown the surface density of the disk

over both arm regions can be calculated using: (7) the “neutral zone” radius

and flat angular rate between leading and trailing arms NGC4622’s; (i7) the

two co-rotation radii and their associated pattern speeds, (ii7) close-in and

distant angular rates and radii and finally, (iv) the arms’ constant inclination.

Fall 2019

The co-rotation radii are accurately determined from color and

association switching relative to the stellar arms. Also note that the

minimum velocity dispersion for stability is assumed. Hidden arms in the

inner and outer disk support the conclusions. No assumption is made about

disk mass-to-light ratio. The major uncertainty is the scatter in the rotation

V versus radius.

The declining inner disk surface density has normal values

comparable to the Milky Way Solar neighborhood. However, the outer

surface density appears to rise sharply to unusually large values outward

through the leading arm region. Besides its leading and trailing arms,

NGC4622’s different pattern speeds and anomalously high outer disk

surface densities, offer even more puzzles for astronomers. Does NGC4622

have an outer flattened disk of dark matter rather than a halo?

References

G. G. Byrd; T. Freeman; S. Howard; R. J. Buta (2008). Astron. J., 135, p.

408413 and references for observations and hypotheses expanded here.

NGC 4622 HST images are at

http://heritage.stsci.edu/2002/03/index.html

http://heritage.stsci.edu/2002/03/ngc4622/10203 w.jpg

Byrd, G. G. (1995) Proceedings of the Waves in Astrophysics conference.

Editors J. H. Hunter and R. E. Wilson. Annals of the New York Academy

of Sciences, Vol. 773, p. 302-319. Invited Review. See this link:

https://www.researchgate.net/publication/229817541 Tidal Perturbation

s Gravitational Amplification and Galaxy Spiral Arms

Kennicutt, R. C. Jr. (1981). Astron. J, 86, 1847.

Shu, F. H. (1982) The Physical Universe, University Science Books.

' (is the symbol for the orbital angular speed of objects revolving about the galaxy

center.

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PROSPECTIVE LAVA TUBES AT HELLAS PLANITIA

LEVERAGING VOLCANIC FEATURES ON MARS TO

PROVIDE CREWED MISSIONS PROTECTION FROM

RADIATION

Antonio J. Paris, Evan T. Davies, Laurence Tognetti, & Carly Zahniser

Center for Planetary Science

ABSTRACT

Mars is currently at the center of intense scientific study aimed at

potential human colonization. Consequently, there has been increased

curiosity in the identification and study of lava tubes for information on

the paleohydrological, geomorphological, geological, and potential

biological history of Mars, including the prospect of present microbial

life on the planet. Lava tubes, furthermore, could serve as in-situ

habitats for upcoming crewed missions to Mars by providing protection

from solar energetic particles, unpredictable high-energy cosmic

radiation (i.e., gamma-ray bursts), bombardment of micrometeorites,

exposure to dangerous perchlorates due to long-term dust storms, and

extreme temperature fluctuations. The purpose of this investigation is

to identify and study prospective lava tubes at Hellas Planitia, a plain

located inside the large impact basin Hellas in the southern hemisphere

of Mars, through the use of Earth analogue structures. The search for

lava tubes at Hellas Planitia is primarily due to the low radiation

environment at this particular location. Several studies by NASA

spacecraft have measured radiation levels in this region at ~342

uSv/day, which is considerably less than other regions on the surface of

Mars (~547 uSv/day). Notwithstanding, a radiation exposure of ~342

uSv/day is still sizably higher than what human beings in developed

nations are annually exposed to on Earth. By analyzing orbital imagery

from two cameras onboard NASA’s Mars Reconnaissance Orbiter

(MRO) — the High-Resolution Imaging Science Experiment (HiRISE)

and the Context Camera (CTX) — the search for lava tubes was refined

by identifying pit crater chains in the vicinity of Hadriacus Mons, an

ancient low-relief volcanic mountain along the northeastern edge of

Hellas Planitia. After surveying 1,500 images from MRO, this

investigation has identified three candidate lava tubes in the vicinity of

Hadriacus Mons as prospective sites for manned exploration. To

complement this investigation, moreover, 30 in-situ radiation

monitoring experiments have been conducted at analog lava tubes

located at Mojave, CA, El Malpais, NM, and Flagstaff, AZ. On average,

the total amount of solar radiation detected outside the analog lava tubes

was approximately ~0.470 wSv/hr, while the average inside the analog

lava tubes decreased by 82% to ~0.083 Sv/hr. We infer, therefore, that

the candidate lava tubes identified southwest of Hadriacus Mons could

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be leveraged to decrease the radiation and to reduce the crew’s exposure

from ~342 pSv/day to ~61.64 wSv/day (a decrease of ~82%). This

investigation, therefore, concluded that terrestrial lava tubes can be

leveraged for radiation shielding and, accordingly, that the candidate

lava tubes on Mars (as well as known lava tubes on the lunar surface)

can serve as natural radiation shelters and habitats for a prospective

crewed mission to the planet.

THE RADIATION ENVIRONMENT ON MARS

EARTH’S MAGNETIC FIELD PROTECTS US from harmful solar and Galactic

cosmic radiation. Though astronauts in low-earth orbit are more exposed to

radiation than humans on the ground, they are still protected by Earth’s

magnetosphere. Outside our magnetosphere, however, radiation is more

problematic. Research studies of exposure to various strengths and doses of

radiation provide strong evidence that degenerative diseases and/or cancer

are to be expected from too much exposure to solar energetic particles

and/or galactic cosmic rays.! Galactic cosmic radiation contains highly

ionizing heavy ions that have large penetration power in tissue and that may

produce extremely large doses, leading to early radiation sickness or death

if adequate shelter is not provided.2 During the Apollo program, for

illustration, astronauts on the moon reported headaches, reported seeing

flashes of light, and experienced painful cataracts. These symptoms,

known as Cosmic Ray Visual Phenomena, were due to radiation from

cosmic rays interacting with matter and deposing its energy directly in the

eyes of the astronaut.* The Apollo missions, however, were comparatively

short, and they cannot be likened to a multi-year presence on the surface of

Mars.

Approximately 4.2 billion years ago, due to either rapid cooling in

its central core or a massive impact from an asteroid or comet, the magnetic

dynamo effect on Mars stopped, and its magnetosphere weakened

dramatically.’ As a result, over the course of the next 500 million years, the

Martian atmosphere was gradually stripped away by the solar wind.

Between the loss of its magnetic field and its atmosphere, the surface of

Mars is now exposed to much higher levels of solar and cosmic radiation

than Earth. In addition to regular exposure to solar energetic particles and

galactic cosmic rays, the planet receives intermittent harmful blasts that

occur from strong solar flares, as well as the bombardment of meteors.* A

crewed mission to the surface of Mars, consequently, will introduce the

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crew and its critical life-support equipment to an environment outside a

much-needed magnetosphere. They will be at risk of absorbing sudden fatal

radiation doses, as well as assuredly suffering cellular and DNA damage

from chronic high background radiation, which will lead to cancer.

Additionally, there is a risk of an unpredictable cosmic ray burst or a meteor

shower capable of critically damaging the crew’s life-support equipment.!

Numerous investigations by NASA have established that the surface

of Mars receives a varying amount of radiation. The difference is largely

due to where the solar wind interacts with electrically charged particles in

the Martian upper atmosphere and the particular topographic elevation on

the planet. The Mars Atmosphere and Volatile Evolution (MAVEN)

spacecraft, for illustration, detected the interaction of the solar wind with

electrically charged particles of the Martian atmosphere.° Atoms in the

upper atmosphere became electrically charged ions after being energized by

solar and cosmic radiation. Because they are electrically charged, these ions

interact with the magnetic and electric forces of the solar wind, a thin stream

of electrically conducting gas ejected from the surface of the Sun.* As

explained in Figure 1, the lines represent the paths of individual ions, and

the colors represent their energy, E, measured in electron volts (eV). The

MAVEN investigation concluded that the northernmost polar plume

contains the most energetic ions, ranging as high as ~20,000 E (eV) — with

the surface of the planet’s northern polar region receiving approximately

~10,000 to ~1,000 E (eV), the southern polar region receiving ~1,000 to

~100 E (eV), and the mid-latitudes receiving the lowest at ~300 to ~10 E

(eV).’

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+———————____ DIRECTION OF SOLAR WIND

E (eV)

= 20000

11875.7

7051.64

4187.16

2486.28

1476.32

876.617

520.523

=} 309.079

| 183.527

@—— 10,000- 1,000 E (eV) | [=] 108.976

=| 64.7083

38.4229

i 22.815

Bg @——— 300-10 E (eV) 13.5472

pi: 8.04415

aay” 4.7765

ae e—— 1,000-100E (ev) 2.83622

— a 1 1.68411

\ te apy 1

Figure 1: MAVEN Investigation of the Solar Wind on

Mars. (Source: NASA)

Similarly, the NASA Mars Odyssey spacecraft was equipped with a

special instrument called the Martian Radiation Experiment (MARIE),

which was also designed to measure the radiation environment on Mars.*®

Over the course of 18 months, MARIE detected ongoing levels of radiation

that were considerably higher than what astronauts experience on the

International Space Station (~200 pSv/day).° At high topographic

elevations, MARIE detected radiation levels at ~547 wuSv/day, which

equates to ~200,000 uSv/year (Figure 2). Although there are no immediate

symptoms while being exposed to ~547 uSv/day, exposure to these levels

of radiation for one year is four times the maximum annual allowable

exposure for U.S. radiation workers (50,000 uSv/year), which can cause

radiation sickness.’ In contrast, the radiation levels at lower elevations were

measure at ~273 uSv/day, because those areas have more atmosphere above

them to block out a considerable amount of the radiation.'° For comparison,

humans in developed nations are exposed to, on average, ~6,200 uSv/year.!!

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Cosmic Ray Environment

Dose Equivalent Values (uSv/year)

1 x 105 1.5 x 10° N 2 x 105

Figure 2: MARIE Investigation of the Cosmic Radiation Environment on Mars.

(Source: NASA)

In September 2017, strong energetic particles from a coronal mass

ejection were detected both in Mars orbit and on the surface (Figure 3).!? In

orbit, MAVEN detected energetic particles as high as 220 million E (eV),

which produced radiation levels on the surface more than double any

previously measured by Curiosity’s Radiation Assessment Detector

(RAD).'? RAD is an energetic particle detector capable of measuring all

charged particles that contribute to the radiation health risks that future

crewed missions to Mars will face.‘ At the time of the coronal mass

ejection, Curiosity was positioned inside Gale Crater at an elevation of

~4,500 m. As cited previously, a lower elevation on Mars allows for

additional atmosphere above the rover, which aids in blocking out a

considerable amount of radiation. At Gale Crater, the normal background

radiation measured by RAD prior to the coronal mass ejection was ~220-

270 wSv/day, which is similar to what MARIE detected (~273 wSv/day).

However, during the coronal mass ejection, RAD detected radiation levels

at ~600 pSv/day — over twice the normal background radiation at Gale

Crater (Figure 3).' While studies have shown that the human body can

withstand a single dose of up to 2,000,000 Sv without permanent damage,"

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prolonged exposure to strong energetic particles will lead to health

complications — including acute radiation sickness (nausea, vomiting,

weakness, headaches, purpura, hemorrhage, infections, diarrhea,

leukopenia), genetic damage, and possibly death. Moreover, exposure to

more than 5,000,000 uSv would kill half of those exposed within a month,

and 10,000,000 Sv would be fatal within days.’

The data from MAVEN, MARIE, and RAD show that the solar wind

and other violent solar activity, such as solar flares and coronal mass

ejections, continue to strip away the Martian atmosphere — but more

importantly, they make the northern latitudes less desirable for human

exploration. The data indicate, moreover, that a crewed mission should

more prudently be placed along the mid-to-southern latitude range — where

there 1s minimized ionic activity from the solar wind (i.e., Hellas Planitia).

Furthermore, the data suggest that the crew should be placed at lower

elevations along the surface of Mars (again, Hellas Planitia), with its thicker

atmosphere, which will help to block out the radiation by a factor of two.

Additionally, a crewed mission on Mars should be effectuated during a solar

minimum (the period of least solar activity in the 11-year solar cycle of the

Sun) to ensure that exposure to radiation due to a solar flare and/or coronal

mass ejection is minimized.!°

15-100 MeV protons

80-220 MeV protons

Energetic Particles

in Mars Orbit

(arbitrary units)

Radiation Dose Rate

at Mars Surface

(u1G/day)

Date (2017)

Figure 3: Radiation data collected by MAVEN and RAD during the September

2017 solar storm. (Source: NASA)

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ANCIENT VOLCANISM ON MARS

Volcanic activity has played an extensive role in the geologic

development of Mars. Planetary scientists have acknowledged since the

Mariner 9 mission in 1972 that volcanic topographies cover great portions

of the Martian surface. These geological features include widespread lava

flows, lava plains, and the largest known volcanic peaks in the solar system,

including the highest, Olympus Mons."’ Volcanic features on Mars range in

age from the Noachian (> 3.7 billion years) to the late Amazonian (< 500

million years) eras, demonstrating that Mars was volcanically active early

in its history.'’ Mars, moreover, is a differentiated terrestrial planet that

formed from analogous chondritic materials.!? Many of the same magmatic

processes that occurred on Earth, for comparison, also took place on Mars.

The two planets are sufficiently comparable compositionally that similar

names can be applied to their igneous rocks and minerals.”” The shape and

size of volcanoes on Mars, though, were largely dependent on a set of

environmental conditions and properties dissimilar to Earth. Lesser

atmospheric pressure altered the scattering of ejected material, a higher

eruption rate allowed for the lava on the surface to pile up higher, and lower

gravity facilitated wider dispersion.?! Consequently, volcanoes and lava

tubes on Mars are more than twice as large as their terrestrial analogues.

THE FORMATION OF LAVA TUBES

Lava is molten rock that is ejected by a volcano during an eruption.

The molten rock on Mars was formed in the interior of the planet in high

temperatures produced by geothermal energy. When the lava first erupts

from a volcanic vent, it is in a liquid state, typically at temperatures ranging

from 1,292° to 2,192°F.” A lava flow, in contrast, is an outburst of lava that

moves during a non-explosive effusive eruption. When the lava flow stops

moving, it cools and hardens to form igneous rock. While lava can be up to

100,000 times more viscous than water, it can flow for a large distance

before abating and solidifying“? Lava flows can occasionally form lava

tubes — natural subsurface caves or caverns — which appear to form because

of rapid lava flow. Lava tubes, which are usually made from extremely fluid

pahoehoe lava, typically form when the exterior surface of lava channels

cools more rapidly and forms a strong crust over the subsurface lava. The

lava flow ultimately stops and drains out of the tube, leaving a conduit-

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shaped void located several feet underneath the surface (Figure 4). As we

discussed above, as gravity on Mars is 37% of that on Earth, lava flow, and

subsequently lava tubes on Mars, are generally much larger than those

found on Earth.”>

eke : 7 y' “ : 4

a w> a * ; Pi she . jee 3

aR ain SMR E ae IES AER en ce iy mages seat :

en aay ac ly Sma a, Pace ana cla OE b oF

te eee MEET pe psi ints 5 Lava Tube ih

2 Ee es ee oe ae " t

Pratl Sp eee “fe Entrance

: . F (A ; \ ee eee al "

~F y - . J > —

- ‘ “Fe = ee Fe re : ;

ae bal _ ee eee 7

— . .

“ |

“ety

Figure 4: Prof. Antonio Paris, the Principal Investigator, conducting

research at the El Calderon lava tubes in El Mapais, New Mexico.

IDENTIFYNG PIT CRATER CHAINS AND LAVA TUBES

Lava tubes below the surface of Mars, as well as those below the

lunar surface, can be identified by locating pit craters in the vicinity of

known ancient lava flows. A pit crater 1s a circular or elliptical depression

shaped by the collapsing or sinking of the surface lying above a void or

hollow cavity, rather than by the eruption of a lava vent or volcano. Pit

craters generally lack a raised rim, uplifting, ejecta blankets associated with

impact craters, or radial patterns of lava flows discharging downslope from

volcanic calderas.*° There are generally two types of pit craters — atypical

and bowl-shaped. Atypical pit craters exhibit a distinctive set of

morphologies and characteristics that set them apart from the commonly

observed bowl-shaped pit craters. Instead of bowls, the interior of atypical

pit craters is cylindrical or bell-shaped with vertical to overhanging walls

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that extend down to their floors without forming talus slopes.?’ In some

instances, atypical pit craters show evidence of vents, fissures, and

caverns/caves that could be intact.

Pit craters have been discovered on Earth, Mars, as well as on the

various moons in our solar system (including our Moon).*® They are

generally located in a series of ranged or offset chains; and in these

instances, they are referred to as pit crater chains (Figure 5). When adjacent

walls between pits in a pit crater chain collapse, they become troughs.”? A

commonly invoked hypothesis to explain these troughs is that they are

collapsed lava tubes, essentially tunnels formed underground by rivers of

lava.*?

Through the use of spacecraft imagery, lava tubes on Earth, Mars

and the Moon can be visually detected in two ways. The first method is by

recognizing troughs or rilles, which, as mentioned previously, are believed

to be the remains of collapsed lava tubes. The second method is by

pinpointing “skylights” -— dark, nearly rounded features that are

hypothesized as entrances to lava tubes.*! At this point, light from the Sun

enters into the permanent darkness of the lava tube from above, forming a

skylight.*? Many lava tubes on Earth, for instance, have been identified

through the discovery of skylights (Figure 5). As is the case on Earth, access

to uncollapsed sections of lava tubes on Mars is available by entering

through a skylight, at the end of the trough or rille where a cave/cavern

could lead into the lava tube, or by drilling or blasting through the roof of a

lava tube.** The Lunar Reconnaissance Orbiter, moreover, has imaged over

200 pits craters on the lunar surface. Many of these lunar pits craters show

skylights into subsurface voids or caverns, ranging in diameter from about

5m to more than 900m, although some of these are likely to be post-flow

features rather than volcanic skylights.*? Moreover, there is observational

evidence from orbiting spacecraft to infer there are lava tubes along the

Marius Hills, Hadley Rille and Mare Serenitatis regions of the Moon. *4

While the lunar surface varies in temperature from -180 C to +100 C, the

interior of these lunar lava tubes could remain at a constant -20 C.

Therefore, lava tubes on the Moon (as well as on Mars), once sealed off,

could be warmed up and pressurized with a breathable atmosphere.*°

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pp)

| Partially Collapsed

| PitCrater Chain }

ce | Skylight |y

. eae

me te ee ee qeeenen=

| Partially Collapsed |

| Pit Crater Chain ;

25 Meters

Figure 5: Similarities between a pit crater chain and pit crater “skylight” at El

Mapais, NM (top image) and South of Arsia Mons on Mars (bottom image).

(Source: NASA, Processing: Center for Planetary Science)

HELLAS PLANITIA:

PROSPECTIVE SITE FOR MANNED EXPLORATION

Hellas Planitia is a large meteorite impact basin located at 42° 42’

S and 70° 00’ E, in the southern hemisphere of Mars, in the Hellas and

Noachis quadrangle.*° The impact basin is thought to have been formed

during the Late Heavy Bombardment period of the Solar System,

approximately 4.1 to 3.8 billion years ago, when a large asteroid hit the

surface. It is 2,300 km in diameter, and it is one of the largest known impact

craters in the solar system (Figure 6).*7 Measurements made by the Mars

Orbiter Laser Altimeter (MOLA) instrument onboard the Mars Global

Surveyor spacecraft indicate that the basin floor is ~7,152 m deep — making

Hellas Planitia one of the bottom-most geographic elevations on the

planet.*® At this depth, consequently, Hellas Planitia has one the lowest

ongoing radiation levels on Mars.

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According to data from NASA’s MARIE experiment, radiation

levels at Hellas Planitia have been measured at ~1 x 10° Sv/year, as

opposed to the higher topographic elevations on Mars, which were

measured at ~2 x 10° uSv/year (Figure 6).8 The depth of the basin,

moreover, is below the standard topographic datum of Mars, which explains

the atmospheric pressure at the bottom of the basin: 12.4 mbar during the

northern summer. This is 103% higher than the pressure at the topographical

datum (6.1 mbar) and above the triple point of water, indicating that a liquid

phase might be present under certain conditions of temperature, pressure,

and dissolved salt content.*? These conditions could provide the crew on

Mars the opportunity to identify and study lava tubes in this region for

information on the — geological, paleohydrological, overall

geomorphological, and potential biological history of the planet. While

there is as of yet no evidence for this, an exciting notion is that, as with

extremophile environments on Earth, these locations may serve as habitats

for possible microbial life on Mars.”

Cosmic Ray Environment

Dose Equivalent Values (uSv/year)

1x 105 1.5 x 10° 2x 105

aE Es

1.25 X 10° uSv/yr

1 oar

Hellas Planitia /

~~ ©

y ae

» E

Pare

Figure 6: An expanded view of the radiation environment at Hellas Planitia.

(Source: Center for Planetary Science)

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HADRIACUS MONS REGION:

PROSPECTIVE LAVA TUBES FOR MANNED EXPLORATION

Hadriacus Mons is an ancient, low-relief volcanic mountain located

along the northeastern edge of Hellas (Figure 7). The volcano has a diameter

of 450 kilometers, and its features differ from other volcanos such as

Olympus Mons and the others in Tharsis and Elysium. Hadriacus’s low

slopes, wide structure, and heavily scored flanks suggest that it is made of

eroded materials.*! Planetary scientists classify this volcanic debris as

pyroclastic, from the Greek meaning “fire-broken.” The large extent of

volcanic deposits and the caldera size, moreover, leads some planetary

scientists to infer that these geological topographies were the result of an

explosive event caused by a contact between erupting magma and

groundwater.”

Daytime Infrared Image of Hadriacus Mons

[ixi0sssvir

Figure 7: An expanded view of Hadriacus Mons along the edge of Hellas

Planitia

(Source: NASA and Center for Planetary Science)

The low radiation levels along the lava flows in this region that

extends from Hadriacus Mons into Hellas Planitia make the location a

prime candidate for human exploration. According to data from NASA’s

MARIE experiment, radiation levels in this region have been measured at

~1.25 x 10° wSv/year (~342.46 uSv/day), which, as previously mentioned,

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is considerably lower than the higher topographic elevations on Mars,

which were measured at ~2 x 10° uSv/year. Notwithstanding, a radiation

exposure of 1.25 x 10° wSv/year is still sizably higher than what human

beings in developed nations are annually exposed to on Earth. The lava

tubes near Hadriacus Mons, consequently, could be used as natural

radiation shelters and habitats for a crewed mission to the planet. These

natural caverns have roofs estimated to be tens of meters thick, which would

provide the crew protection from not only exposure to too much radiation,

but also the bombardment of micrometeorites, exposure to dangerous soil

perchlorates due to long-term dust storms, and extreme temperature

fluctuations.“ Moreover, although the exact conditions of the interior of

Martian lava tubes will remain unknown until they are actually explored,

planetary scientist are of the consensus that they represent prime locations

for direct observation of pristine Martian bedrock, where keys critical to

understanding the natural history of this planet will be found.*”

The NASA HiRISE and CTX data used in this study were available

through NASA’s Planetary Data System (PDS). MRO CTX observes

Mars’s surface at ~6 m/pixel in swaths of 30 km across and up to ~160 km

in length. MRO also observes the Martian surface earlier in the day; thus,

more pit craters can be observed with partially sunlit floors.*? A partially

sunlit floor allows planetary scientists to identify specific pit crater

characteristics such as skylights, individual boulders, dusty, or rocky

surface textures, overhanging rims, wall and floor morphologies, and

bedrock stratification.°?

An analysis of 1,500 HiRISE and CTX images of the Hellas Planitia

basin uncovered several volcanic features southwest of Hadriacus Mons,

which were subsequently identified as candidate lava tubes (Figure 8). The

first candidate lava tube identified in this study is located southwest of

Hadriacus Mons in the Dao Vallis region at latitude -36.961° and longitude

87.841°E (MRO CTX Catalog: J11_049132 1423 XN_37S272W). The

~4,500-meter collapsed lava pit (Figure 8a), which is positioned between

two partially collapsed sinuous pit crater chains, depicts two surface areas

that have not collapsed (Figure 8a and 8b). Imagery analysis indicates the

area of the northern uncollapsed surface is ~600 meters long and ~300

meters wide (Figure 8a), and that the area of the southern uncollapsed

surface is ~900 meters long and ~600 meters wide (Figure 8b). Further

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analysis of the ~4,500-meter collapsed lava pit with its contrast range

limited to low-end radiance values indicate that the pit crater walls

encompassing both uncollapsed areas are structurally intact — ruling out a

lava bridge — indicating that a lava tube below the surface is plausible, since

these parts of the pit crater chain have not collapsed.

Planetarv Science)

The second candidate lava tube identified in this study is located

south of Hadriacus Mons in the Dao and Niger valleys region at latitude -

33,250 and) longitude: “9398072 (MIRO Cx VCaialos, “CILX:

P13_006237_1475 XN _ 32S266W). An analysis of the CTX imagery

depicts an atypical pit crater with a diameter of ~700 meters positioned

between two sinuous chains of partially collapsed elliptical bowl-shaped pit

craters (Figure 9a). The same atypical pit crater with its contrast range

limited to low-end radiance values depicts the presence of a possible

overhanging rim or shoulder along the northern section, which could be the

entrance to a lava tube (Figure 9b). As mentioned previously, the leading

accepted hypothesis is that since the pit crater chains East and West of this

atypical pit crater have not fully collapsed, then a lava tube could exist

below the surface.

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Dao and Niger Vallis

S i *

~ é

; [canst Caelcave |

Sao ntiig Vat Daataat te we okt Aa,

Figure 9: Candidate lava tubes south of Hadriacus Mons. (Credit: Center for

Planetary Science)

The third candidate lava tube identified in this study is located

southwest of Hadriacus Mons in the Dao Vallis region at latitude -36.870°

and longitude 89.498°E (MRO CTX Catalog:

F0O3_036987_ 1432 XN_ 36S270W). The ~25-meter collapsed pit, which

appears to indicate the entrance to a candidate cavern and/or cave, is

preceded by a partially collapsed trough (Figure 10a). The collapsed trough

is sinuous, and, as previously cited, it could be associated with the presence

of a lava tube below the surface. The same collapsed pit with its contrast

range limited to low-end radiance values depicts the presence of boulders

that more than likely arose from the collapse of the western wall section,

which could be the entrance to a lava tube (Figure 10b). The region of the

candidate lava tube, moreover, is characterized by numerous sinuous

collapsed pit crater chains ranging in size — providing further evidence that

one or more lava tubes could exist below the surface. Interestingly, this

proposed lava tube is analogous to Giant Ice Cave in E] Mapais, NM (Figure

11), which is also characterized by a partially collapsed sinuous trough that

leads into the entrance of a lava tube.

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4 | | Candidate Cave

Dao Vallis

Figure 10: Candidate lava tubes south of Hadriacus Mons. (Credit: Center for

Planetary Science)

RADIATION EXPERIMENTS AT TERRESTRIAL ANALOG

LAVA TUBES

To ascertain whether lava tubes on Mars (or correspondingly the

lunar surface) could be used by surface crews to reduce exposure from solar

or cosmic radiation, we conducted 30 analog radiation experiments. The

experiments were conducted during solar noon at terrestrial lava tubes

(Figure 11) located at Mojave, CA (Aiken), El] Mapais, NM (Big Skylight,

Giant Ice Cave, and Junction Cave) and Flagstaff, AZ. (Lava River Cave).

Because radiation from the sun strikes the surface of Earth at different

angles, conducting the experiments at solar noon (when the sun is directly

overhead) allowed the surface area where the experiments were conducted

to receive the most electromagnetic energy from the sun possible.”4

Furthermore, a sun at 90° above the surface of each lava tube prevented the

radiation from becoming too scattered and diffused.

~The Geiger counter for this experiment was equipped with a

halogen-quenched, long thin cylindrical Geiger-Mueller tube capable of

detecting Gamma and X-rays (ionizing radiation) down to 10 keV thru the

window, 40 keV minimum through the case, and with a Gamma sensitivity

of 10,000 pSv/hr. Although Earth’s atmosphere and magnetic field protect

us from most ionizing radiation from the Sun, streams of ionizing radiation

still reach the surface of Earth. Occasionally, during a solar particle event,

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larger amounts of ionizing radiation strike the surface of the Earth, which

can also be detected by the Geiger counter.

Giant ice Cave, NM

ice columns To Big Skylight &

Parking Area

\. perennial

ice floor

Figure 11: Lava tube maps and the interior locations (black triangle) where

each radiation experiment was conducted.

(Map Sources: Mojave lava tube sketched by Prof. Antonio Paris, others

National Park Service)

Preceding each experiment, the device was turned on for a minimum

of one hour to establish a baseline reading. The experiment was then

conducted in two parts — measuring the amount of solar radiation outside

the lava tube and then comparing it with the amount of solar radiation

measured inside the lava tube. In total, six one-hour readings were

completed for each lava tube (three exterior and three interior) for a total of

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30 observation hours (Table 1). On average, the total amount of radiation

detected during solar noon on the exterior of all five lava tubes was ~0.471

uSv/hr (V7) while the average radiation detected inside the lava tubes was

~0.083 pSv/hr (V2). Furthermore, during the experiments, we observed a

significant drop in temperature (Table 1) inside the terrestrial lava tubes,

which likewise would be the case for lavas tubes on Mars.

Analog Site Avg Surface Reading uSv/hr Average Interior Reading uSv/hr Avg Surface Temperature -C Average Interior Temperature - <

Mojave Aiken - California O46 0.088 12 9

El Malpais - Big Skylight - New Mexico 0.501 0.062 20 13

El Malpais - Giant Ice Cave - New Mexico 0.434 0,098 18 10

El Malpais - Junction Cave - New Mexico 0.458 0,078 17 11

Lava River Cave - Arizona 0.492 0.089 25 12

Average 0.4706 0,083 12.4 ai

Table 1: Average amount of radiation (uSv/hr) measured at five terrestrial lava tubes.

(Source: The Center for Planetary Science)

When we applied the percentage change equation (Figure 12), the

results of the radiation experiment showed that, on average, the amount of

radiation (A/) in the interior of the analog lava tubes decreased by an average

of 82%. We can infer, therefore, that the candidate lava tubes identified

southwest of Hadriacus Mons could be leveraged to decrease the radiation

by ~82% and, accordingly, to reduce the crew’s exposure from ~342.46

uSv/day to ~61.64 uSv/day.

Ay sit gl SA 0 = ree cea

IY: | Iv |

ra. | 0.083 pSv/hr - 0.470 uSv/hr | hee

. |0.470 uSv/hr |

= 82.34% (decrease in radiation)

Figure 12: Percentage change equation for radiation reduction inside analog lava tubes.

Washington Academy of Sciences

CONCLUSION

An analysis of HiRISE and CTX imagery of the Hellas Planitia

basin, specifically southwest of Hadriacus Mons, identified pit crater chains

consistent with known lava tube morphology. Although the internal

structural conditions of the candidate lava tubes remain largely unknown, a

close examination of the satellite surface imagery suggests that sections of

the pit crater chains have not collapsed, and therefore that lava tubes below

the surface could be internally intact. Furthermore, the candidate lava tubes

identified in this investigation are positioned in a region of Mars that

regularly has lower radiation exposure than other regions on the planet.

Though a background radiation environment of ~342.46 uSv/day is still

significantly high, the terrestrial analog experiments conducted at Mojave,

CA, El Malpais, NM, and Flagstaff, AZ concluded the lava tubes southwest

of Hadriacus Mons could reduce the crew’s exposure to radiation to ~61.64

uSv/day. The results of this investigation, therefore, indicate that the

proposed lava tubes southwest of Hadriacus Mons can and should be

utilized to serve as natural shelters for a crewed mission to the planet. These

natural caverns would provide the crew protection from excessive radiation

exposure, shelter them from the bombardment of micrometeorites, reduce

their exposure to hazardous perchlorates in the Martian regolith, and

provide them a degree of protection from extreme temperature fluctuations.

The candidate lava tubes, moreover, can serve as important locations for

direct observation and study of Martian geology and geomorphology, as

well as potentially uncovering any evidence for the development of

microbial life early in the natural history of Mars.

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BIOS

Antonio Paris, PhD is the Chief Scientist at the Center for Planetary

Science, an Assistant Professor of Astronomy and Astrophysics at St.

Petersburg College, FL, and a graduate of the NASA Mars Education

Program at the Mars Space Flight Center, Arizona State University. He is

the author of Mars: Your Personal 3D Journey to the Red Planet, and his

latest peer-reviewed publications include “El Bahr: A Prospective Impact

Crater in Egypt” — an investigation addressing the discovery of an

unidentified crater located south of the Sahara Desert between Qaret Had E]

Bahr and Qaret El Allafa, Egypt. Prof. Paris is a professional member of the

Washington Academy of Sciences and the American Astronomical Society,

and he has appeared on the Science Channel, the Discovery Channel, and

the National Geographic Channel.

FIELD RESEARCH CONTRIBUTERS

Evan Davies, PhD is an anthropologist, science writer and a practicing

physician assistant in emergency medicine. He is the author of Emigrating

Beyond Earth: Human Adaptation and Space Exploration, and he is a

fellow of both the Royal Geographical Society and the Explorers Club.

Laurence Tognetti recently graduated from Arizona State University with

a Master’s Degree in Geological Sciences, with thesis research focusing on

geomorphological processes of the Martian surface. As a Field Researcher

for the Center for Planetary Science, he collected and analyzed ionizing

radiation data and geological specimens in situ for the analog experiments

of this investigation.

Carly E. Zahniser recently graduated from Eckerd College with a Bachelor

of Science in Environmental Science. As a Field Researcher for the Center

for Planetary Science, she collected and analyzed ionizing radiation data

and geological specimens in situ for the analog experiments of this

investigation.

Washington Academy of Sciences

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(available at https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA 20368).

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Astrobiological Targets on Earth and Mars: A Review.” Planetary and Space

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a Future Moon Colony?", i09/ Gizmodo.com, retrieved 24 January 2016.

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tubes on the Moon: Possible lunar base habitats", In NASA. Johnson Space

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Tubes. Universe Today. (available at

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h/map/Docs/Globes/i2782_sh1).

37 Schultz, Richard A.; Frey, Herbert V. (1990). “A New Survey of Multi-Ring Impact

Basins on Mars.” Journal of Geophysical Research. 95: 14175

38 National Aeronautics and Space Administration. Hellas Planitia (available at

https://mars.nasa.gov/resources/7648/topographic-map-of-hellas-

planitia/?site=insight).

39 Haberle, Robert M. et al. (October 25, 2001). “On the Possibility of Liquid Water on

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David; Schulze-Makuch, Dirk; Amils, Ricardo. “Prime Candidate Sites for

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of Hadriacus Patera in Mars. 46th Lunar and Planetary Science Conference, 2014.

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Hidden in Lava Tubes.” Spaceflight Insider (available at

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Physiology (4th Edition) (available at

https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-

biology/solar-radiation).

Washington Academy of Sciences

Background Material

Lead in Drinking Water in the District of Columbia,

2000 - 2004:

A Case Study of Public Health Risk and

Abatement

Tee L. Guidotti, MD

Abstract

In 2001 following a change in disinfection agent in anticipation of the EPA

Disinfection Byproduct Rule, average lead levels began rising in drinking

water in Washington, DC, initially at a slow rate. By 2002 the DC Water and

Sewer Authority (WASA) was found to have exceeded the EPA lead action

level, requiring compliance with a series of measures under the Lead and

Copper Rule. In 2004, the issue became a public concern as articles in the

Washington, DC, press appeared. The water chemistry problem was resolved

in late 2004 through the application of orthophosphate. The risk management

options utilized by WASA included public education, provision of water

filters, flushing, support for monitoring blood lead levels, monitoring of lead

in water, replacement of lead service lines, and obtaining access to public

health and risk management services. The experience from the incident

cannot be used to assess the contribution of lead in drinking water to blood

lead levels, because there were numerous interventions likely to have

mitigated any effect. This case study describes several lessons learned in risk

communication applied to water issues.

Introduction

IN 2004 NEWS ABOUT ELEVATED LEVELS of lead in the drinking water in

some homes caused considerable concern to residents of the District of

Columbia (DC). (Guidotti et al. 2008) The responsible utility, the DC

Water and Sewer Authority (WASA), was suddenly faced with a practical

environmental risk management problem of enormous proportions,

notwithstanding the limited public health significance of the event. The

unintended consequences of these interventions played out over several

years and continue today, in 2009.

This case study documents the origins of the problem and

describes the sequence of events that followed, providing an accurate

Fall 2019

chronology and insights into policy issues as they arose. Fundamental

issues relating to the regulation and management of drinking water quality

came to light during this experience. Most of these issues were national in

scope but were first and most acutely felt in Washington, DC, as a result

of the incident. These key issues will be highlighted throughout the case

study. Supplementing these essential or key issues are numerous

secondary issues, which will be noted as they arise. This case study covers

2004.

Background

The drinking water distribution system of Washington is similar

to that of other major cities such as Philadelphia and New York City.

Water is essentially free of lead when collected, disinfected, finished,

supplied to the distribution system and delivered to the water mains

serving a street or neighborhood. Lead enters drinking water by migrating

from lead-containing surfaces distal to the water main. The most

important source, where it is present, is dissolved lead from the lumen of

lead service lines, which deliver water from the main to the tap. Until

approximately 1950, but with many exceptions, lead was the material of

choice for service lines to single-family houses because it is malleable and

repaired easily. Subsequently, lead service lines were replaced in new

construction and for rehabilitated houses by copper or polyvinyl chloride.

A further complication in the District of Columbia not present in other

cities is that the service line to the house is divided at the property line:

the proximal part is the public portion of the service line, owned by the

water utility, and the distal part belongs to the property and therefore the

responsibility of the homeowner. (Figure 1) In New York and

Philadelphia the entire service line 1s deemed to be private property.

At the time events unfolded in 2000 and 2001, there were

approximately 100,000 metered customers in the District of Columbia, of

which an estimated 23,000 had service lines connecting the main line to

the house that were made of lead (Nakamura 2004b). Lead was a standard

material for service lines in the early twentieth century, though modern

home construction uses copper or plastic piping. Single-family homes

built before about 1950 often, but not invariably, originally had lead

service lines. Some homes have had their lines replaced and some were

originally installed using other materials, even in the pre-World War II

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era. The qualities of malleability and easy joining which made lead

attractive for single houses made it unsuitable for apartment buildings

because over a certain diameter the lead pipes collapsed too easily. In

Washington, DC, lead service lines were and are most common in older

neighborhoods but can still be found throughout the city, in affluent as

well as in disadvantaged blocks.

In circumstances where a service line needs to be replaced, a utility

does not normally (without special legislation) have the authority to

replace the private portion of the service line without the homeowner’s

permission. Other sources of lead in the distribution system might include

lead-containing solder used to join copper pipes, leaded brass components

of meters (even some models billed as “lead free’’), and faucet valve seats,

all of which are inside or attached to the houses and are therefore

considered responsibility of the homeowner.

WASA is a relatively young agency, created in 1996 as an

independent agency of DC with a regional governing board. It replaced

the Water and Sewer Utility Administration, a utilities agency of the

Government of the District of Columbia that had experienced a long

history of fiscal and management problems.

Owing to its unique status as seat of national government and its

status as a Semi-autonomous jurisdiction rather than a state, the District of

Columbia’s water supply is under federal authority. Unusual among

metropolitan water utilities in the United States, WASA operates the

drinking water distribution system for its customers but does not collect

or treat its own water (DC WASA 2008). Water is drawn from the

Potomac River, filtered, and disinfected by the Washington Aqueduct, a

division of the US Army Corps of Engineers, in an arrangement which

dates to the Civil War when the water supply of the capital required

military protection. The Washington Aqueduct supplies finished water to

WASA, Arlington County and the City of Falls Church. WASA is

regulated directly by Region 3 of the US EPA, instead of an autonomous

state regulatory agency subjected to EPA oversight, which is the standard

practice in the United States (Holder 2004). (EPA is divided for

operational purposes into nine regions, which have a high degree of

autonomy in their regulatory oversight; Region 3 covers the District of

Columbia, Pennsylvania, Maryland, Delaware, and West Virginia from a

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regional office in Philadelphia.) This unique arrangement is shared with

the state of Wyoming and will continue until the new DC Department of

Environment has the capacity to assume oversight and regulatory

authority.

WASA’s Water Quality Division is responsible for monitoring

lead and copper levels. One of the responsibilities of this unit is to

coordinate WASA’s reporting to the Water Quality Division of Region 3

EPA under the Lead and Copper Rule (LCR) (US Environmental

Protection Agency 1991), a regulation promulgated as part of the Federal

Safe Drinking Water Act (United States Congress 1974).

Under the LCR, EPA requires that lead in tap water not exceed the

designated Lead Action Level (LAL) of 15 parts per billion (ppb) on the

specified “first draw” from the tap in more than 10% (i.e., the sample

representing the 90" percentile cannot exceed 15 ppb) of tap water

samples from homes, after 6 hours of stagnation (i.e. the tap cannot have

been used for at least that long). This rather arcane standard for water

quality, which was designed as a corrosion control measure, has been the

source of much confusion. It is important to recognize that 15 ppb is a

“lead action level” (LAL), not a “maximum contaminant level” for lead

in drinking water, which is an enforceable allowable upper limit and

which is the usual way of regulating water contaminants in the United

States and elsewhere. The LAL and the method of determining the LAL

are therefore not comparable to the standards of the World Health

Organization (10 ppb at any time) or the European Union.

The annual year for sampling and notifying lead levels runs from

July 1 to June 30 of the next year (US Environmental Protection Agency

1991). Water is normally tested every six months. WASA qualified for a

four month monitoring period under a provision in the LCR for “reduced

monitoring” since EPA Region 3 designated optimal corrosion control

treatment (OCCT) and WASA consistently met the water quality

parameters under the LCR. Under this sampling regime, monitoring

occurs during the warmest months of the year between June and

September, when lead levels are likely to be highest. The one-litre water

samples are to be "first draws" from residents' taps after no less than six

hours since last use (this is in practice usually first draw in the morning).

The presumption of the LCR is that water collected in this way will reflect

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lead levels at the tap derived from either service lines running from

WASA’s main lines to the house or from the houses’ own pipes, meters,

and fixtures. (Figure 1) The LCR lead service line sampling requirements

do not apply to apartment buildings or schools as these buildings require

larger service lines made from a material stronger than lead, such as

ductile iron.

An exceedance is not considered to be a violation of the drinking

water standard because the LAL is not a maximum contaminant level

(MCL). Instead it is a trigger for a set of mandated actions under the LCR,

which are described in greater detail below.

Chronology of Events

Water samples had been well below the LAL during the 1999-

2000 monitoring period and for a number of years before that. As a result,

WASA had qualified for “reduced monitoring” under the provisions of

the LCR. Under “reduced monitoring” status, the frequency of monitoring

was reduced from every six months to every twelve months and the

number of sites required to be monitored was reduced from 100 to 50

collected between June and September. Thus, WASA entered the critical

period with no expectation of future exceedance and a reduced monitoring

schedule (Holder 2004). The subsequent events have been documented

through interviews and discussions with key personnel at WASA, by

newspaper accounts, and by reference to several authoritative reviews by

both government and private agencies which resulted in detailed reports.

(Holder 2004; US Environmental Protection Agency 2004a; DC Office of

the Inspector General 2005; US Government Accountability 2004, 2005;

DC Appleseed Center 2004; discussions with WASA senior management

2004)

Change in Disinfection Agent

The Washington Aqueduct used chlorine as its disinfection agent

until 1 November 2000. It then changed to chloramines, a mixture of

chlorine and ammonia, in order to reduce the levels of free chlorine in

anticipation of the requirements of the Disinfection Byproduct Rule (US

Environmental Protection Agency 1998), which was about to go into

effect. The use of chloramines has become standard at many utilities,

where it has been effective and generally free of problems. WASA was

Fall 2019

consulted on this decision and agreed, as did the responsible oversight

authority, the Water Protection Division of Region 3 EPA.

The Washington Aqueduct continued to moderate pH with lime

(calcium carbonate) and no other changes in water chemistry were made.

The decision to manage pH with lime, rather than the common alternative

phosphate, had been made by the Aqueduct in 1994, with the agreement

of WASA’s predecessor agency.

The US EPA had issued the Disinfection Byproduct Rule as part

of a complicated set of regulations to be phased in from 1998 to 2003.

These regulations were intended to ensure adequate disinfection of

bacterial contamination (as indicated by coliform count, which is used as

a surrogate) and to reduce levels of trihalomethane compounds (US

Environmental Protection Agency 1998).

2000-2001 Monitoring Period

In the 2000-2001 sampling period (ending 30 June 2001), the

Washington Aqueduct received 118 samples (from 62 locations) from

WASA to measure for lead levels, but almost half of these were second-

draw samples and there were discrepancies because of resident non-

compliance, duplication, and reported mistakes in drawing water from the

tap. There were 55 acceptable, first-draw, single-site samples, taken

during the warm weather months of 2000 and June of 2001, a time when

lead levels were likely to be highest because of temperature and when

more water is consumed. The 40 samples taken in summer 2000 showed

no elevation in lead. Unexpectedly, however, 7 out of 15 of the June 2001

samples exceeded the LAL of 15 ppb.

An administrative decision was made at WASA at a middle-level

management position to invalidate some of the samples. Whether or not

this was done with prior knowledge and approval of EPA is disputed,

(Holder 2004). Consequently, senior management at WASA have stated

that they were not alerted and so were unaware of the implications of this

deviation from guideline values. The relatively small excursion above

historical levels was dismissed initially by the chief operating officer as

too small to be significant. In retrospect, the intense focus on regulatory

compliance, in which achieving the standard absorbed the attention of

management, may have interfered with interpretation of this important

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signal that levels were rising and that the system was behaving

unpredictably.

2001-2002 Lead Monitoring Data

WASA entered the 2001-2002 monitoring period essentially

unaware of the magnitude of the impending problem and committed to a

monitoring schedule that may have been inadequate to define the

emerging problem.

Continuing on from the trends indentified in June 2001, initial

results from July and September 2001 showed that among the first 25

samples, 8 homes had levels above 40 ppb, indicating that individual LAL

exceedances were being detected more frequently and at higher values in

a steady but not dramatic rise. With 8 positive findings out of 50 projected

samples, the LAL had already been exceeded for the stipulated 90% of

samples for the year under the LCR. Region 3 EPA was therefore notified

directly by the Manager of WASA’s Division of Water Quality in August

2001 that an annual exceedance was likely. There is a dispute over

whether there was timely notification of WASA management. Ultimately,

among the 36 samples in July and August 2001, 20 homes exceeded the

LAL of 15 ppb (as documented in a communication dated 12 October

2001 between the Washington Aqueduct and WASA). By the end of the

monitoring period at the end of June 2002, 26 of 53 samples were above

the LAL. The Board of Directors of WASA was informed of the annual

exceedance in September 2002 (Holder 2004). At this point, the senior

management of WASA had lost a full year of response time. No cause for

the exceedance had been found and there was still a strong suspicion that

the elevated levels only represented a statistical anomaly. The annual

exceedance would trigger a series of requirements under the LCR for

which WASA was ill-prepared, but in September 2002 the LCR had yet

to be invoked. In September 2002, representatives of WASA and Region

3 EPA met to discuss appropriate customer notification of the elevated

lead levels. At this time, WASA’s efforts were apparently still oriented

toward identifying the problem and ruling out measurement error.

October 2002 and Triggering the LCR

By October 2002, four months into the 2002-2003 monitoring

period, it was obvious that the exceedance would continue through

Fall 2019

another year and would require concerted action. WASA was now treating

the situation as an urgent operational matter but not as a public health

crisis and was expecting at that time to receive an exemption from the

LCR during the search for a system-wide solution. WASA therefore was

caught off guard when Region 3 EPA declared that the provisions of the

LCR would be enforced, as of the end of the 2001-2002 monitoring period

(Holder 2004).

The LCR is an unusual regulation (US Environmental Protection

Agency 1991). Although an exceedance is not technically a violation, it

immediately requires five stringent actions from the utility:

e Additional water system monitoring, returning to the more

intensive 6-month, 100-sample schedule.

e Water treatment to reduce the source of lead contamination,

which usually implies more aggressive treatment of corrosion

and pH that leaches lead from lead water pipes.

° Public education, using bill inserts and flyers, using prescribed

language that is specified in the regulation.

e Replacement of lead service lines on a specified schedule

requiring at least 7% or more to be replaced per year.

2 The LCR allows utilities to test houses with lead service lines for

lead concentration at the tap and to consider them as having been

replaced, for purposes of the LCR, if the concentration is below

the lead action level of 50 ppb. These lines then do not have to be

physically removed and replaced. (US Environmental Protection

Agency 1991)

The US EPA has since completed a review of the LCR, in part

because the experience in DC and experiences elsewhere have led to

unintended consequences (Cohn 2004a; Leonnig 2004).

WASA duly notified and requested consultation and assistance

from the District of Columbia Department of Health and released an

announcement of the exceedance to the public (Nakamura 2004a). The

first news item appeared on 18 October 2002 in The City Paper, a free

community publication with a wide local readership. The story indicated

that WASA would conduct a public education lead-awareness program,

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targeting children and pregnant women. The story attracted no visible

public attention.

Public Education 2002-2003

The LCR requires an extensive public education program. It

dictates prescribed language to be used in public communications but

allows additional material to be added in lay language. The statements

mandated in the LCR require a moderately high degree of reading ability

in standard English.

As required by the LCR, WASA initially produced public

communication materials in late 2002, as listed in Table 1.

“Living Lead Free in DC” was the most comprehensive consumer

health publication distributed at that time. WASA sent "Living Lead-Free

in DC" to the two major local newspapers, public schools, libraries, and

health facilities during Lead Poisoning Awareness Week (20-26 October

2002). The text was based on content provided by the DC Department of

Health and used language drawn from, but not precisely following, the

LCR. The text was approved by Region 3 EPA. It was criticized much

later for being insufficiently explicit about the exceedance because it did

not highlight the problem of lead in drinking water, give statistics on lead

levels in DC drinking water or convey recommendations for protection of

vulnerable consumers. It also had a high English literacy requirement.

In retrospect it became apparent after the public’s reaction in 2004

that the messages disseminated in 2002 were not successful but that may

not have been apparent in 2002.

Lead Service Line Replacement 2002 - 2003

Within one year of the initial exceedance, the LCR requires that a

plan be submitted to replace all lead services lines in the distribution

system on a schedule of at least 7% per year. The replacement of lead

service lines is very capital-intensive, costing on average $5,000 per line.

It is also highly disruptive, requiring streets to be torn up and blocked off

and trenches to be dug through sidewalks, gardens, and lawns.

WASA had no lead line replacement program in place in 2002

because it had not been needed. As a consequence, the organization was

unprepared. A contractor had previously conducted an inventory of lead

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service lines known to be in place, estimating 20,000 to 22,000 lines

(Nakamura, 2004b). This turned out to be an underestimate and the true

number was probably around 35,000. It was already known from the

utility’s experience that the database had many inaccuracies in recording

(informal estimates placed it around 15%) which homes had lead service

lines because it had been constructed from work order records which were

both incomplete and often in error.

It was physically impossible to replace the required 1,600 lines in

the first year. The more known lead service lines that tested with favorable

results and were so “deemed” to have been replaced, as described above,

the fewer that would have to be replaced, which carried a cost of $7.5

million per year.

The Board of Directors decided to accelerate the lead service line

replacement program on July 1, 2004, in order to complete replacement

by 2010. (This was later revised to 2014 and then 2016 when the number

of service lines was found to be greater than expected.) This accelerated

schedule committed WASA to replacing 10% of lines per year, at a cost

of $100 million over ten years (Nakamura 2004d). WASA prioritized

replacement of lead lines serving the homes with the highest lead levels

and homes where children lived, in order to protect vulnerable populations

first (Holder 2004).

The LCR requires the replacement of the “public” service line, the

portion running from the main distribution pipe to the property line of the

homeowner. (Figure 1). However, achieving a reliable reduction in lead

levels at the tap depends on replacement of both public and private

sections. Replacement of the “private” portion, running from the property

line into the house, is the responsibility of the homeowner but there is no

mandate under the LCR requiring the homeowner to replace the private

portion. WASA offered to replace the private part of the line at the same

time as the public line at cost (as required by LCR), averaging about

$2,000, but few homeowners complied. Without replacement of the

private part of the line, however, replacement of the public portion had a

much-reduced effect. WASA therefore arranged for low-interest loans

through Wachovia Bank and the DC Council eventually approved a grants

program for low-income families (Nakamura 2004c). Even so, fewer than

Washington Academy of Sciences

15% of homeowners took advantage of the arrangements by the end of

2004.

The Public Health Response, 2003—2004

WASA initially turned to the DC DOH for assistance in preparing

the document “Living Lead-Free in DC” in September 2002, at a time

when the DC DOH was able to provide such technical support. Shortly

thereafter, DC DOH entered a period of instability during which it lacked

the capacity to provide stable, consistent support. Subsequently, in mid-

to late 2004, the Department responded with the enhanced screening

program and joined WASA, the Washington Aqueduct, and Region 3

EPA in a series of community meetings to show consensus on the health

message WASA contracted with our academic unit to provide public

health and risk management expertise directly, as consultants to the utility,

which led to the present work.

Following the LCR and guidance from Region 3 EPA, WASA

instituted a series of recommendations and advisories for families living

in homes with lead lines or those that returned elevated levels of lead in

tap water: Specifically, WASA:

° Recommended that water lines be flushed for 10 minutes before

consuming drinking water. (Initially the recommendation was for

90 seconds, which is sufficient to deliver lead-free water from

the main. Water filters were distributed to all homes where the

LAL was exceeded and later to all homes with suspected lead

service lines. Replacement filter cartridges were sent to the same

homes at six-month intervals.

° Homeowners continued to be offered the services of WASA’s

contractors to replace private lead service lines at cost at the

same time that public lines were replaced.

° WASA continued its public outreach, offering testing to any

property owner and resident who wished it.

Visibility and Risk Perception, 2003—2004

Although the first newspaper report on the lead elevation did not

draw much public interest, a front page article of The Washington Post

(January 31, 2004), received national attention and elicited considerable

local concern, as indicated by the frequency of telephone calls and

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attendance at community meetings. The media coverage that followed

declared this issue as a “public health crisis’ (Nakamura 2004e).

Numerous articles in the Washington Post and other media criticized

WASA for changing its recommendations over time in the face of new

evidence. The Post also identified tap water lead levels by individual

home addresses obtained from a web-accessible database. (WASA policy

is not to release such data.) (Nakamura 2004f)

Adding the perception of a public health risk during the period of

peak interest was a series of stories on water fountain lead testing in

schools (Paley 2004). The EPA guidance on testing schools is different

from that applied to homes under the LCR. Testing is voluntary on the

part of school districts and standards are based on a maximum allowable

level, not the corrosion-derived method for examining behavior of the

distribution system that is used in the LCR. Several samples taken in

school drinking fountains and faucets exceeded the guidance of 20 ppb

and a few showed markedly excessive levels (one exceeded 4000 ppb in

taps that were, however, seldom used or flushed. Although presented in

the media as part of the same story, the issue of lead in drinking water in

schools is distinct and relates specifically to the maintenance of school

property. At the time, there was also a similar but unrelated issue playing

out in the media with WASA’s sister utility in suburban Maryland. To the

casual reader, therefore, it appeared that drinking water throughout

metropolitan Washington was unsafe and even dangerous.

Risk Management in 2004

While these other events were occurring, WASA attempted to

determine the actual cause of the elevation and to identify ways to mitigate

the problem. It was assisted by a Technical Expert Working Group, an ad

hoc group of advisors convened jointly by WASA and Region 3 EPA (US

Environmental Protection Agency 2004b). WASA also began doing pipe-

loop corrosion experiments (Cohn 2005). These experiments involve

circulating water through removed sections of water pipe to determine the

effect of chloramines on water lines, in the context of its own system and

water chemistry.

In 2004, an opportunity arose for a natural experiment on the

system. An annual system-wide pipe flushing was scheduled for April and

May to remove sediment. During this flushing, the Aqueduct returned to

Washington Academy of Sciences

chlorine on a temporary basis. Lead levels fell throughout the system,

strongly suggesting that the problem arose with the change in disinfection

agent (US Environmental Protection Agency 2004c; American Water

Works Association 2005). The working theory was that rather than

increasing corrosion directly, the switch to chloramine had reduced the

tendency of metals and residue on the surface of the pipe (scale) to form

reversible complexes, which had the effect of enhancing the leaching of

lead. A permanent return to chlorine was not possible, however, because

of the Disinfection Byproduct Rule.

The Washington Aqueduct and WASA, with approval from

Region 3 EPA, then determined that addition of phosphate, in the form of

orthophosphate (phosphoric acid), would act to stabilize these surface

complexes over time, although the effect would take many months. This

was tried on a pilot basis in one segment of the distribution system and

caused no untoward effects. On August 23, 2004, phosphate was

introduced system-wide. Subsequently, the lead level in tap water slowly

fell and has been compliant with the LCR since 2005.

Analysis

The response to the lead issue and the requirements of the LCR

severely strained the operational capacity of the organization. WASA

faced a crisis of credibility during a period when the organization was still

relatively new and while the position of public affairs director was vacant.

By the end of 2004, WASA had expanded its public relations and legal

staffs (Nakamura 2004), hired a team of academic consultants on risk

management from The George Washington University (Nakamura

2004h), staffed fully its research and development laboratory, assembled

its own team of experts and consultants, and pulled together a network of

contractors capable of replacing 1,615 service lines per year.

Early Events

None of the parties involved initially seems to have considered

lead levels in DC drinking water to be a warning of a deeper problem

because it had never been a problem since the creation of WASA. The

elevations in July 2001 were considered an anomaly that did not reflect a

true change in water chemistry. WASA’s orientation at the time was

toward compliance, not risk management; if a final result was in

Fall 2019

compliance with the LCR, there was no mechanism in place to identify

trends or to anticipate the risk of future problems. Since management and

accountability systems were not set up to assess anomalies in the

performance of the system in 2001 and because the organization had

focused narrowly on compliance, WASA was caught off-guard and a year

later had to scramble to meet the requirements of the LCR.

The risk communication challenge was as severe as any faced by

a water utility in modern times. Key lessons learned from this experience

include that risk communication, crisis communication, and corporate

communication are separate and distinct. They have different dynamics

and methods. Risk communication is about what a potential hazard means

for individual people and families. Crisis communication guides people

through a period of perceived danger or a dislocation in their lives.

Corporate communication informs people of the purpose, responsibility,

and assistance provided to them by the organization. The one factor all

three communication types have in common is that both are most effective

when they focus on what people want to know and not on what the

organization thinks they should know.

Education on the context of an issue, in this instance the water

distribution system, is difficult in the middle of a crisis when one message,

in this case the health risk, dominates other messages. We recommend

that water utilities use the period between crises to lay the foundation for

understanding the issues. In this case, WASA’s risk communication

message would have been easier for the public to accept had there been a

better understanding of the water distribution system as a whole. On the

other hand, it is hard to imagine the pubic taking an interest unless there

is a problem.

It is essential to build partnerships in advance of a crisis. Had

WASA and DC DOH had an effective working relationship before the

incident, the initial response might have been more appropriately focused

on water. Such coordination is admittedly difficult where there is

discontinuity in leadership, as occurred with the DC DOH. By

coordinating their messages and press releases, the Washington Aqueduct,

WASA, Region 3 EPA and the DC DOH were ultimately able to achieve

a harmonized message at community meetings and avoided the

appearance of conflict and contradiction.

Washington Academy of Sciences

Acknowledgement:

This study was supported by a contract from 2004 through 2008

between the DC Water and Sewer Authority and the George Washington

University, which was retained to provide assistance to WASA in risk

management. We thank WASA for technical information and figures and

for providing documentation to confirm the accuracy of the chronology.

WASA has been renamed “DC Water’.

This paper was originally accepted by the Journal of Water and

Health in 2008. The paper was withdrawn by the authors before

publication to avoid entanglement in a highly visible legal action

(Parkhurst v. DC Water and Sewer Authority). The authors felt that

because the same evidence was expected to be presented in court,

publication before trial would inevitably be construed as an attempt to

influence the decision. Four coauthors withdrew from authorship in 2008

in response to a climate of intimidation that prevailed at the time. The

legal action was dismissed in 2016.

Aside from this acknowledgement, which was added in 2018, this

paper was written in stages from 2004 through 2008 and is unchanged

from the original submission. It therefore represents a preserved

contemporary record.

References

Agency for Toxic Substances and Disease Registry (ATSDR). 2007 Toxicological

profile for lead. Atlanta, Georgia: US Department of Health and Human Services,

Agency for Toxic Substances and Disease Registry.

Available at http://www.atsdr.cdc.gov/toxprofiles/tp13.html

American Water Works Association. 2005 Managing change and unintended

consequences: Lead and Copper Rule corrosion control treatment. American Water

Works Association.

Bellinger, DC & Needleman, H.L. 2003 Intellectual impairment and blood lead levels.

New Engl J Med. 349, 500-502.

Canfield, R.L., Henderson, C.R., Cory-Slechta, D.A., Cox, C., Jusko, T.A. & Lanphear,

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below 10 pg/dL. New Engl J Med. 348, 1517-1526.

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with elevated lead in tap water- District of Columbia, 2004. Morb Mort Week Rep.

53, 268-270.

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Cohn, D. 2004a Lead scare prompts EPA review of rules. The Washington Post. 23

July 2004. B, BOL.

Cohn, D. 2004b Water a minor source of lead, WASA is told. The Washington Post. 7

May 2004. B, BO1.

Cohn, D. 2005 DC tests show drop in levels of lead: New chemical credited; EPA plan

disparaged. The Washington Post. 12 March 2005. B, BO1.

DC Appleseed Center. 2004 Lead in the District of Columbia drinking water. Available

at: http://www.dcappleseed.org/projects/publications/leadreport.pdf.

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District of Columbia Office of the Inspector General. 2005 Audit of elevated levels of

lead in the District's drinking water. OIG No. 04-2-17LA. 5 January 2005.

Franko, E.M., Palome, J.M., Brown, M.J., Kennedy, C.M., Moore, L.V. 2009. Children

with elevated blood lead levels related to home renovation, repair, and painting

activities — New York State, 2006, 2007. Morbidity Mortality Weekly Reports, 58,

55 — 58.

Gilbert, S.G. and Weiss, B. 2006. A rationale for lowering the blood lead action level

from 10 to 2 ug/dL. Neurotoxicology, 27, 693-701.

Goldstein, A. 2004 An immeasurable threat in DC: High lead levels hurt developing

children, but scientists say danger is hard to gauge. The Washington Post. 20

February 2004.

Guidotti, T.L., Calhoun, T., Davies-Cole, J.O., Knuckles, M.E., Stokes, L., Glymph,

C., Lum, G., Moses, M.S., Goldsmith, D.F. & Ragain, L. 2007 Elevated lead in

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Guidotti, T.L., Moses, M.S., Goldsmith, D.F. & Ragain, L. 2008 DC Water and Sewer

Authority and lead in drinking water: a case study in environmental health risk

management. J Public Health Manag Pract. 14(1), 33-41.

Holder, E.H. Jr. 2004 The Holder Report: Summary of Investigation Reported to the

Board of Directors of the District of Columbia Water and Sewer Authority. 16 July

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Jusko, T.A., Henderson, C.R., Lanphear, B.P., Cory-Slechta, D.A., Parson, P.J. and

Canfield, R.L. 2008. Blood lead concentration < 10 g/dL and child intelligence at

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Canfield, R.L., Dietrich, K.N., Bornschein, R., Greene, T., Rothenberg, S.J.,

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level environmental lead exposure and children’s intellectual functioning: an

international pooled analysis. Environmental Health Perspectives, 113, 894-899.

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Leonnig, C. & Cohn, D. 2004 DC lead tests cast doubt on EPA standards. The

Washington Post. 5 March 2004. A, AOI.

Mendelsohn, A.L., Dreyer, B.P., Fierman, A.H., et al. 1998 Low level lead exposure

and behaviour in early childhood. Pediatrics. 101, E10.

Nakamura, D. & Goldstein, A. 2004a Agencies finishing warnings on lead: Notices to

be sent to thousands with suspect water lines. The Washington Post. 27 February

2004. B, BOI.

Nakamura, D. 2004b Location of much lead pipe unclear: With records missing on

thousands of lines, city uses guesswork. The Washington Post. 15 February 2004.

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Nakamura, D. 2004c WASA to replace 2,800 lead pipes over next year. The

Washington Post. 13 November 2004. B, B01.

Nakamura, D. 2004d WASA to speed removal of pipes: Some DC officials question

lead plan. The Washington Post. 2 July 2004. A, AO1.

Nakamura, D. 2004e Water in DC Exceeds EPA Lead Limit. The Washington Post. 31

January 2004. A, A01.

Nakamura, D. 2004f WASA Urges Judge to Reject Lead Lawsuit. The Washington

Post. 14 May 2004. B, BO1.

Nakamura, D. 2004g WASA spends $100,000 for advice on communications. The

Washington Post. 29 June 2004. B, B02.

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The Washington Post. 3 April 3 2004. B, B08.

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Role and Responsibility of Government and Nongovernment Organizations, pp.

45-49 (New York, Plenum).

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et al. 2004 Blood lead levels in residents of homes with elevated lead in tap water

— District of Columbia. Morb Mort Week Rep. 53(12), 268-270.

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Title 42, Section 300. 42 USC. § 300f, et seq.

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Regulations Part 141. 40 C.F.R §§ 141.80-91.

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Byproduct Rule. Code of Federal Regulations Parts 141 and 142. 40 C.F.R. §§

9,141, and 142.

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guidance for public water systems. EPA-816-R-02-009. Available at:

http://www.epa.gov/safewater/Icrmr/pdfs/guidance_lcmr_pws_monitoring.pdf.

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Compliance on Consent. Docket # SDWA-03-2004-0259DS. 14 June 2004.

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Simultaneous compliance summary. | 1-12 May 2004.

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9TAT. 22 July 2004.

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public from elevated lead levels. GAO-05-344. March 2005.

Washington Academy of Sciences

Figure 1. Schematic drawing of the water distribution system from the

water main to inside the house.

Street

Underground

Public service line SRaRhaRNsR “—“HiewP rivate service line Se

Shutoff valve

Water main

Table 1. Public Communications by WASA in 2002 and 2003.

Mailings, initially special mailings and later inserts with bills

mailed to customers.

A section on the exceedance in the annual Consumer Confidence

Report, a federally required report on water quality and service

designed for customers.

Public service announcements on local media, primarily radio.

When these were perceived to be ineffective, largely because

they were broadcast infrequently and during late hours, WASA

purchased advertisement slots to run on local broadcast channels

during peak hours.

A special Water Quality Report, “Your Drinking Water is Safe,”

reinforced by media appearances by the WASA General

Manager.

“Living Lead-Free in DC”, a glossy 12-page booklet, was

released in October 2002 for Lead Awareness Week in

collaboration with the DC Department of Health.

A telephone hotline was established in January 2003 to collect

citizen complaints and to provide information.

Public meetings were convened beginning in May 2003. Initial

turnout was low.

A message was placed on the water bill itself in August 2003, as

required by the LCR.

Fall 2019

Washington Academy of Sciences

Fifteen Years Later:

Notes on Lead in Drinking Water, Washington DC,

2004

Tee L. Guidotti, MD

George Washington University (retired)

Abstract

In 2004 Washington DC (“the District”) experienced an environmental health

crisis involving elevated lead levels in drinking water. Fifteen years on it is

time for a reassessment. The impact on Washington was nothing like that of

the appalling situation in 2014 in Flint, Michigan, other than that lead was

involved in both. The situation in Washington arose as an unintended and

unexpected consequence of measures to reduce the levels of halomethane

compounds in drinking water to reduce the potential for cancer risk. The

problem ended with a simple and very conventional solution, the judicious

application of a nontoxic chemical treatment already commonly used to

correct water chemistry (zinc orthophosphate). DC public school students who

were at a susceptible age in 2004 have achieved major gains, not losses, on

national standardized education tests.

Introduction

IN 2004 WASHINGTON DC experienced an environmental health crisis

involving elevated lead levels in drinking water, leading to fears of lead

poisoning and learning disabilities among District children. There were two

levels of potential risk: an increased frequency of lead poisoning in the short

term, which was effectively ruled out, and a subtle and difficult to

characterize prevalence of neurotoxicity in the long-term that probably

could not be documented. In the end the risk was mitigated first by a public

notification campaign (as required under the relevant regulation) and

provision of free water filters to residents, and second by passivation of the

water system with a safe and widely used water additive.

At a point where the worst of the risks did seem to have been ruled

out, a massive class-action lawsuit (Parkhurst v. DC Water and Sewer

Authority) was filed in 2009 for alleged damages, demanding $200 million

from the water utility, which would have added roughly $1300 to the water

bill for every household. Worse, thousands of infants and young children

who were growing up in the District could easily have been labeled as at

Fall 2019

risk, mentally and in learning ability, by those who did not understand the

science but read the headlines, including parents who had diminished

expectations for their children, school admissions officers outside the area

who may have doubted their potential, and future employers who would

have new grounds for discrimination.

Fifteen years on, it is time for a reassessment to determine the actual

lessons learned. Since 2004 DC public school students who were at a

susceptible age have achieved major gains, not losses, on national

standardized education tests. (Tuque, 2011, Brown 2013) The number of

cases of children with diagnosed lead poisoning (by the definition current

at the time) did not spike. The problem ended with a simple solution, the

judicious application of a nontoxic chemical treatment commonly used to

correct water chemistry (zinc orthophosphate). (While no chemical is

entirely free of toxicity, orthophosphate comes close.) The class

certification and eventually the whole legal action were dismissed. In the

end the impact on Washington was nothing like that of the horrendous lead

issue that erupted in 2014 in Flint, Michigan, which it in no way resembles

other than that lead was involved in both. The situation in Washington arose

as an unintended and unexpected consequence of measures to reduce the

levels of halomethane compounds in drinking water in keeping with

existing procedures, regulations, and water treatment processes. Flint, on

the other hand, was a predictable and avoidable crisis created by

malfeasance, mismanagement, and political interference with an essential

public health function. It was also one of several closely interrelated public

health problems related to water at the time. (Clark, 2018)

Lead exposure is always a legitimate public health concern

regardless of source, because the neurotoxicity of lead shows no threshold

for children. The incident in the District was the first national experience

with a technological innovation in water disinfection that backfired. It was

a wake-up call to the legacy risks associated with the lead-dependent water

distribution system in older cities. It was important locally as the first trial

under fire of the newly reformed DC Department of Health (DOH), which

in 2003 had been in a near meltdown and in 2004 was under new, untested

leadership. In the end the incident had the positive effect of drawing

attention to the most important source of exposure, which is peeling leaded

interior paint in houses, and resulted indirectly in a much improved lead

Washington Academy of Sciences

law, the DC Lead Hazard Prevention and Elimination Act of 2008 (amended

in 2010).

The present paper is intended to lay out the issues as they were seen

at the time, from the point of view of a university-based consultant in public

health to the water utility, then called the DC Water and Sewer Authority

(WASA), who also worked closely with the DC Department of Health

(DOH) at the time.

Background

Water from the Potomac River watershed is essentially free of lead.

Lead in drinking water does not come from the source or from surface

pollution but from soluble lead migrating into the water flow from the

components of the water distribution system. These include the interior

surface of lead “service lines”, lead-containing brass fittings, older water

meters, solder joints, and faucets. Service lines are lead pipes that carry

water the last few meters from the water main (running under the street) to

the house. Service lines carrying water to houses, but not to larger buildings,

were almost always made of lead until the 1930’s, when they began to be

replaced in new construction by copper. The transition was largely complete

by the 1950’s. (Rabin, 2008) The result has been a legacy of buried lead

pipes in older neighborhoods and cities. These “lead service lines” are

expensive to replace (usually with copper for single-family houses) and

when this is done the old lead lines are usually left in the ground,

unconnected.

For many years, until the turn of the last century, drinking water was

among the most important sources of lead intake in the United States, other

than occupational exposure. (Troesken, 2006) Improvements in the drinking

water distribution system led to a gradual reduction of waterborne lead

exposure, despite the presence of lead service lines. At the same time

exposure to other sources from lead was considerably reduced or, in the case

of lead in gasoline eliminated altogether beginning in the 1970°s. The mean

blood lead levels of children declined dramatically, in parallel with airborne

lead levels. (Pirkle, 1994) This decline was also seen in Washington and

was sustained until 2001, when there was a small rise (to be discussed

below) followed a year later by a return to the declining trend.

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In 2000 Washington DC, for reasons of federal prerogatives and

jurisdiction, had something of a test case for changes in drinking water

chemistry. The US Environmental Protection Agency (EPA) had mandated

a national conversion in disinfection agents, critical for the prevention of

waterborne disease, from chlorine to chloramines, in order to reduce the

formation of potentially carcinogenic organic compounds in water

(trihalomethanes). This was initiated in Washington in January 2000.

Unexpectedly, because chloramines had not had this effect in other settings,

in Washington lead levels rose inexorably in tap water but for a long time

still remained below the regulatory standard (to be explained below). The

change in water chemistry that resulted had eluted soluble lead by

converting insoluble tetravalent Pb(IV) to soluble Pb(II), a reaction

discovered by the EPA’s Michael Shock, but not understood in 2004.

(Renner, 2006)

Exactly when this slow increase in water lead levels was noticed for

what it was and whether it was properly reported to senior management has

been a matter of contention and litigation, complicated by a confusing legal

action over removal of the compliance officer. However, in retrospect it is

abundantly clear that had the rise in water lead levels over 2001 and 2002

been appreciated and assumed to be real, and not thought to be a statistical

fluke of sampling, the response would have been more robust and timely.

By mid-2002, the provisions of the Lead and Copper Rule (LCR)

were triggered. [Note: The EPA announced on 10 October 2019 that the

LCR will be revised.] The [current] LCR prescribes monitoring for lead in

water at the tap, mandates measures to be taken in the event of an elevation

over the allowable level of lead at the 90" percentile of samples, and

requires scheduled replacement of lead service lines, which is a very

expensive proposition. The issue had generated its first news story (in the

City Paper) (Levin, 2002) and a public information campaign was in

progress. The DOH had been called in but was not providing WASA needed

support and advice because of its internal issues.

This incident was widely presumed at the time to be a classic issue

of environmental justice, but it was not. At that time, there was not a strong

association between housing quality and price and the presence or absence

of a lead service line, although there probably is now. They could be found

in every ward, in houses in all price ranges, including the most expensive,

Washington Academy of Sciences

and were not concentrated in poor or disadvantaged neighborhoods.

Washington has gone through an extensive period of housing rehabbing,

renovation, and restoration, which means that homeowners with resources

are much more likely to have largely replaced lead services lines and

remediated lead paint, while disadvantaged owners may have not and so

housing quality is becoming a better marker for the presence of a lead

service line than it was in 2004.

Fifteen years later Washington DC still has many lead service lines

that have not been replaced because of the cost ($5000 per house).

Replacement is legally the responsibility of the homeowner because the

District does not own the service line. (This is not true for other cities, such

as New York.) In practice, part of the line does run through city property

but partial line replacement is only partially effective and may create a new

opportunity for spiking lead levels at the tap. From about 2005 to 2008,

there was some interest in a comprehensive lead service line replacement

program but this diminished because appropriate water treatment had

brought lead levels under control by then. (We proposed at a hearing in 2008

that there be mandatory total replacement funded as a deduction from

money transfers for real estate sales at the time of closing, but that proposal

did not get any traction, presumably because of the added expense in a less

robust real estate market.) Ultimately, enthusiasm for a permanent solution

gave way to acknowledgement of the exorbitant cost and reliance on current

water treatment practices to forestall a recurrence.

Exposure Assessment

Since well before the creation of the EPA, the primary strategy for

control of lead in drinking water has been to ensure that water flowing

through the service line is rendered chemically unreactive (passivated) with

the interior surface of the lead pipe. This is normally accomplished by

controlling the pH, by adding orthophosphate (a nontoxic chemical that

passivates the line), or not overtreating the water so that it becomes too

“soft” (reduced in calcium and magnesium ion content, which promotes

leaching of lead).

Exposure assessment for lead intake can be difficult, especially

quantifying intake from water. Methods that quantify daily intake require

accurate measurement of both the concentration of lead in the water

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consumed and water consumption habits. Children, in general, consume

more tap water than adults. Most people in modern society tend to consume

more processed water than tap water, in the form of commercial beverages,

and consume much of their water intake outside the home, for example at

work, in restaurants, and at school. The major exception is infants whose

sole or main source of nutrition is formula made from tap water. Formula

might be made once or twice a day and would therefore reflect the lead

content at the time it was made, which is disproportionately likely to be in

the morning, after overnight stagnation.

Water distribution systems are highly variable, both within any one

system and among different systems. The LCR protocol was designed as a

measurement to track system-specific corrosion performance, not as a

health standard, although the ultimate purpose in driving a reduction in lead

content in drinking water is of course to protect health. The key to that is

control of the “corrosivity” of water throughout the system. Corrosion

control monitoring in the United States, uniquely, monitors lead and copper

concentrations in “stagnated” water (water that has been allowed to rest in

the distribution system for a time) with a statistical target for the 90th

percentile of samples rather than a maximum allowable or permissible

concentration. The protocol used for measuring lead in tap water under the

Lead and Copper Rule (LCR) is a compliance measure, designed to ensure

that the distribution system as a whole is not experiencing aberrant swings

in lead concentration. It has been appropriated for use as a surrogate group

measurement for lead exposure but it was not designed for that purpose.

This concept is key to understanding what follows.

The selection of houses is made from a predetermined panel of

participating households with geographic dispersal within the water system.

In Washington participation on the part of homeowners in testing has been

a problem for many years. Samples are taken at the tap within thirty seconds

or one minute from “stagnated” water that has not run for at least six hours.

The LCR has a provision for a reduction in sampling when a water utility

has been compliant for a long period and no problem is anticipated. In 2000

and 2001, WASA was on an EPA-approved reduced-frequency sampling

program because a lead exceedance had not occurred for many years. (With

the benefit of hindsight, it is clear that the sampling schedule should have

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been returned to normal frequency during the transition period, in

preparation for unanticipated consequences.)

The water samples taken in a particular period are tested for lead

and ranked. Most will be very low and some even close to zero. However,

the measurement of the sample at the 90" percentile (“ile) is compared to

a standard called the “lead action level” (LAL), which under the LCR is 15

ppb. The LAL does not apply to levels > 15 ppb in any individual sample,

only to the 90%ile in the set of samples. Statistically, this protocol operates

as if one were tracking the overall academic performance of a school by

following the test scores of D students (above failing but doing worse than

other students when graded on a curve), assuming that majority of students

were getting passing grades and did not require close attention. Such a

system would be good at identifying schools that were producing more

students who were at or close to failing but would say very little about the

performance of the average or well-performing members of the class.

Similarly, the LCR protocol is designed to flag water distribution systems

that are at or coming close to elevated lead levels in water in some of the

taps in their distribution system but it does not provide a measurement or

even a reliable indication of how much lead is in water actually consumed

from the tap. The methodology for determining how much tap water is

actually consumed and calculating the lead content is highly dependent on

recall or direct subject monitoring at the point of consumption. There is no

reliable methodology for estimating this from population-level data.

The LAL was created to benchmark the behavior of the water

distribution system, not a cutoff for an individual sample of water, a

maximum allowable level for the water supply, or a health risk-based

standard. In most countries, and in the US for other contaminants, the usual

approach to setting standards to regulate water contaminants is to compare

water concentrations against a “maximum contaminant level” (MCL),

which is an enforceable allowable upper limit that applies to all drinking

water, all the time. (World Health Organization, 2006) Lead is the exception

precisely because lead comes from the distribution system, not from the

source or external contamination, and so most samples test close to zero and

only the higher measurements matter in the distribution. For that reason, the

shape of the curve is hyper-exponential or J-shaped, not normally or linearly

distributed, and the 90%ile is a benchmark for the position of the curve, not

Fall 2019

a cutoff for allowable concentration for any one sample. An MCL for lead

could, in theory, allow lead at a concentration just below that level for all

water consumed, which would lead to much greater intake of lead from

water than the LAL, which defines the distribution of a curve in which most

values are close to zero and sends a warning when the curve has shifted that

the system is has changed its performance characteristics.

A secondary issue that emerged during the controversy is the

chemical form of lead and the implications for bioavailability. Most

bioavailable lead in drinking water is solubilized lead present as a

dissociated lead salt. Measurements of “total lead” in water may include

poorly soluble particulate lead that is solubilized by the analytical procedure

but is not in a form readily absorbed by the body. The “approved

methodology” for preparing water for lead determination is EPA Method

6020, which involves adding nitric acid to dissolve lead in the sample at pH

2 before it is tested. Nitric acid was chosen specifically because it is capable

of dissolving lead completely. However, the acid produced in the stomach

is hydrochloric acid, not nitric acid. Almost uniquely, hydrochloric acid

does not readily dissolve lead because it forms chloride complexes. Gastric

peristalsis then carries lead particles into the gut, where the pH is high and

absorption is low.

EPA Method 6020 is designed to increase the sensitivity of lead

detection and to ensure that small particles of lead are accounted for as well

as dissolved lead, not to reproduce physiological conditions after ingestion

of a lead particle. When nitric acid is used in lead determination, it dissolves

particulate lead and lead-containing flakes of scale prior to water analysis.

This does not reflect effective exposure and absorption from stomach

contents.

By comparison most lead used in leaded paints were in the form of

lead salts, principally lead carbonate (PbCOs3). The solubility and

bioavailability of lead carbonate, together with its sweet taste, is precisely

why leaded paint chips are so toxic and dangerous to children.

Correcting the Record on the 2007 Paper

In 2007, we published a study of 6,834 subjects who had received

blood lead level (BLL) determinations in a six-month period in 2004 during

which the DOH ran a supplemental lead screening program for District

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residents. (Guidotti, 2007) This expanded lead screening program was a

public health intervention, in which the objective was to identify children

with elevated blood lead levels. At the time, as now, the threshold for

considering the level to be elevated was a blood lead in children above the

CDC’s “level of concern” by the definition at the time, which is universally

considered too high today (10 ug/dl). DOH kept the data confidential and

did the analysis in house but our team evaluated the findings at the request

of the DOH. 65 children were found to have “elevated” blood lead levels,

about as expected.

There were four indicators of public health impact derived from the

data presented in the study. The first was the median blood lead level for

children in the screening program, which was slightly less than the median

for US children in urban areas. The second was the distribution of blood

lead levels, which if there were an affected subgroup might be expected to

show a bimodal distribution or at least a fat tail of the curve; no such second

mode was present. The third would have been the identification of cases in

which no obvious source of lead exposure was found; only two such cases

were identified and in neither was lead in drinking water found by the DOH

to have been a plausible source. The fourth was the lack of a correlation

between elevated lead in drinking water in homes and elevated blood lead

levels in children from those homes, when paired data were examined in

two convenience samples. At the time, we were also aware that there had

been no spike in lead poisoning cases reported for evaluation and treatment

in the District, but did not publish this as a fifth indicator because we did

not have the actual number. The number of children with elevated blood

lead levels at that time usually numbered between 150 and 200 per year in

Washington DC at the time and 2004 was not exceptional. We did not do a

longitudinal analysis of lead levels because we had been warned that the

DOH data from 2003 were incomplete.

An important subgroup finding in our paper, discussed at length,

was the demonstration that children living in homes with lead service lines

showed higher blood lead levels than children living in homes without such

lines. This finding had been seized upon as prima facie evidence for a

waterborne lead risk. However, houses that had lead service lines in 2004

were also much more likely to retain interior leaded paint because they had

not undergone rehabbing, whereas houses without lead service lines were

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either of more recent construction or if older were more likely to have been

rehabbed. This is because of the provision of the DC Plumbing Code

mentioned earlier. Therefore children living in houses with lead service

lines were almost certainly also at greater risk for background lead exposure

from dust and the opportunity for catastrophic exposure to paint chips and

consequent lead poisoning, simply because the presence of the lead service

line was a marker for a house that was older but had not been rehabbed.

In 2004 we approached the EPA Office of Water and asked for

clarification on predictions of the pharmacologically-based toxicokinetic

(PBTK) model in the version then in use by the agency, the so-called

IEUBK. This model is known routinely to overestimate the contribution of

water intake to blood lead because of its default assumptions. Despite its

limitations we wanted to quantify the sensitivity of blood lead to intake from

water in young children. In response, the National Center for Environmental

Assessment did a set of simulations to determine the concentration of lead

in water that would be required to change blood lead levels under three

conditions, in the presence of standard default conditions of intake from

food and other sources: 1) change by a detectable amount, 2) contribution

sufficient to reach a significant level potentially associated with subclinical

toxicity (5.0 ug/dl) from water alone, and 3) contribution sufficient to reach

the CDC “level of concern” (10.0 ug/dl) from water alone. (EPA, 2004) The

Office of Water graciously did so and informed us that the threshold level

for a detectable change (defined as 0.1 wug/dl) was estimated to be

approximately 7.1 ppb (= ug/l) for 1 to 2 year olds and 6.7 ppb for 2 to 3

year olds. The level associated with a blood lead level of 5 and of 10 ug/dl

(the “level of concern” at the time) was approximately 21 and 24 ug/l,

respectively. The level required to reach a blood lead level of 10 ug/dl was

approximately 93 and 96, respectively, for regular, sustained intake

throughout the day. These are figures for continuous intake, however, not

peaks. (EPA, 2004; memorandum from Robert W. Elias to Edward V.

Ohanian, 30 August 2004) Since the background level in water is zero most

of the time, it seems clear that by the IEUBK, drinking water is unlikely to

be the major contributor to blood lead levels.

There were other studies. Their authors will have to speak for

themselves if they care to but none has received, and withstood, the same

scrutiny as the 2007 paper. Shared limitations in other studies were over-

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reliance on modeled or incomplete rather than actual outcome data,

limitations in exposure assessment, neglect of obvious confounding factors

(and a striking incuriosity to resolve spatial anomalies despite the

availability of data to do it), and lack of appreciation for exposure-response

relationships in drawing conclusions. Because of the prominence of the

issue in the Nation’s Capital and the significance of the event as a portent

for future unwelcome surprises, we advocated at the time for a thorough

review of all available studies by an authoritative neutral party (we preferred

the National Academies). That did not happen and as a result numerous

incomplete and uninformative summaries of greater or lesser detachment

(distinct from objectivity) circulated, most of which betrayed a lack of

appreciation for the technical aspects of the problem and so tended by

default to look for evidence of malfeasance or environmental injustice.

Conclusion

Controversy over the relationship between lead in drinking water

and risk of elevation in blood lead is missing the point. Whether formally

defined as “elevated blood lead level” by the CDC level of concern or the

population distribution, there is no compelling evidence at present that

drinking water at levels commonly encountered in the community and in

compliance with the LCR contribute more than marginally compared to

historical risk in children. Elevations not far above the LCR are unlikely to

be drivers of blood lead levels except perhaps in infants, who may be at risk

under special circumstances if formula is prepared from first-draw water

and boiled down. That does not negate the general principle that sound

environmental and public health management oblige us to reduce exposure

to lead from all sources to as low as feasible, as we made clear in the 2006

article. It is also clear that as historically more significant sources of lead

exposure decline, the contribution from sources of lesser magnitude

becomes more visible and proportionately more important. Regardless, we

should be clear that lead paint and lead-containing dust continue to be the

major driver for lead exposure in young children and the debate over water

should not distract us from addressing this priority.

What happened in Washington DC in 2004 and in the years just prior

is a case study in the public health management of an unanticipated

environmental hazard. It is also a cautionary tale of how environmental

epidemiology can be mismanaged. Studies in the real world of public health

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are not clean, controlled trials. It is not appropriate to treat a population-

level case study on the same terms as a toxicokinetic study. It is also not

appropriate to dismiss basic issues of confounding or temporality as

irrelevant because they do not fit a preconceived narrative. The rancor on

display was also totally uncalled for.

Most authors commenting on the events miss the essence of the

problem in Washington, DC, which has been that Washington has

historically experienced a high frequency of individual cases of elevated

blood lead level but not a high mean blood lead level, and continued to show

this pattern throughout the period of concern.

The frequency of elevated blood lead levels are driven by the

probability of encountering a critical exposure source but because this

involves a relatively small number of children, rare elevated levels do not

affect the mean for a large population. The exposure source of significance

for individual cases of elevated blood lead is overwhelmingly lead paint in

older housing units. Once a child encounters a single leaded paint chip, the

contingent probability of an elevation in blood lead level is very high and

the result may be catastrophic. Since relatively few children encounter lead

paint chips compared to the entire population of children and fewer still

encounter other concentrated sources, the exposure sources for the

population as a whole are predominantly food and dust, with water playing

a secondary role.

All sources of lead should be controlled to the extent possible

because they all contribute to body burden and cumulative effect. That, and

the historical fact that in the past water was associated with high exposure

in some situations (Troesken, 2006), makes it necessary to remain vigilant

and to continue to regulate lead in drinking water. Indeed, this is precisely

the reason we studied this topic in the first place.

Washington Academy of Sciences

References

Brown E. DC posts significant gains in national test, outpacing nearly

every state. Washington Post, 7 November 2013.

https://www.washingtonpost.com/local/education/de-posts-significant-

gains-on-national-test-outpacing-nearly-every-

state/2013/11/07/decc08c0-475c-1 1e3-b6f8-

3782ff6cb769_story.html?utm_term=.78d7bec62440

Clark A. The Poisoned City: Flint’s Water and the American Urban

Tragedy. New York, Metropolitan Boos, 2018.

Environmental Protection Agency, National Center for Environmental

Assessment, Office of Research and Development. Memorandum from

Robert W. Elias to Edward V. Ohanian, Director, Office of Science and

Technology of the Office of Water, entitled “Request for IEUBK

modeling of Pb in drinking water. 30 August 2004.

Levin J. Plumbing the depths. (Washington) City Paper, 18 October 2002.

http://www. washingtoncitypaper.com/news/article/13025198/plumbing-

the-depths

Neighborhood Info DC. Ward Profile: Ward 4.

http://www.neighborhoodinfodc.org/wards/nbr_prof_wrd4.html#sec_hsn

Pirkle JL. The decline in blood lead levels in the United States. The

National Health and Nutrition Examination Surveys. JAMA

1994;272(4):284 — 291.

Rabin R. The lead industry and lead water pipes. “A Modest Campaign”.

Am J Pub Health 2008;98(9):1584 — 1592.

Renner R. Experiment confirms chloramine’s effect on lead in drinking

water. Science News (American Chemical Society),

http://www.vce.org/Experimentconfirmschloramine.html

Troesken W. The Great Lead Water Pipe Disaster. Cambridge MA, MIT

Press, 2006.

Turque B. D.C. schools test scores a mixed bag. Washington Post, 8 July

2011. https://www.washingtonpost.com/local/education/de-schools-test-

scores-a-mixed-

bag/2011/07/08/gIQAHn4h4H_story.html?utm_term=.a368c2a29839

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World Health Organization. Guidelines for Drinking Water Quality: First

Addendum to the Third Edition. Geneva, WHO, p. 152 of text, p. 17 of

addendum, 2006.

Bio

Dr. Guidotti MD, MPH, DABT, is the Former Director, retired, of the

Center for Risk Science and Public Health at the School of Public Health

and Health Services (now the Milken Institute School of Public Health) of

the George Washington University, Washington, DC. He is currently a

consultant operating as a sole proprietorship, Occupational +

Environmental Health & Medicine, in Silver Spring MD.

(www.teeguidotti.com)

Acknowledgement:

The initial study was supported by a contract from 2004 through

2008 between the DC Water and Sewer Authority (WASA) and the George

Washington University, which was retained to provide assistance to WASA

in risk management. We thank WASA for technical information and figures

and for providing documentation to confirm the accuracy of the chronology.

WASA has been renamed “DC Water”.

Washington Academy of Sciences

AstroBite — An Impossible Black Hole

The latest science news mentions the discovery of an impossible black hole.

Black holes are strange celestial objects that apparently litter out Universe.

They result from Einstien’s General Theory of Relativity, but were

mentioned in theory much earlier (see Howard, JWAS, 97, 1 (2011)).

Astronomers think that stellar sized black holes result from the end process

of a massive star — one that is originally many times the mass of our Sun.

The star implodes after scattering stellar remnants back into space, leaving

behind a singularity. Mathematically this becomes a one divided by zero

spot. One divided by zero is undefined. It is not zero; it is not infinte; it is

undefined. The laws of physics do not apply and cannot be used. This

undefined spot is called a singularity in spacetime. That singularity is a

black hole. We cannot see it; we cannot touch it; we cannot escape it if we

get too close. We can describe its environment, at least up to a point. Black

holes were considered a mathematical curiosity until the 1950s. By the

1960s black holes were shown to result from the General Theory of

Relativity.

In addition to stellar sized black holes (ones that are the result of star’s

implosion process) there are supermassive black holes that have masses

many millions of solar masses. These supermassive black holes tend to lurk

in the centers of galaxies. There is one in the center of our own Milky Way.

Black holes do not zoom around the Universe gobbling up stars. They tend

to sit quietly where they were formed. However they compress a lot of mass

into an extremely small point. A lot of mass in a teeny space means that the

gradient of its gravitational field is quite steep. If a star gets close enough

(and that is pretty close), it will inexorably be drawn into the black hole.

The same amount of mass in a large space (like our Sun) does not have a

steep gravitational gradient. It does, however, have the same gravity as a

one solar mass black hole. If the Sun were to become a black hole, the Earth

would continue to orbit as it had been orbiting. It is not close enough to get

drawn in. In the case of a one solar mass black hole, close enough means

within three kilometers.

So what is an impossible black hole? Well a group of Chinese astronomers

have discovered a black hole 70 times the mass of the Sun. This is about

twice what current stellar evolution models can predict. In other words a

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12:

massive star can implode to produce a black hole of about 30 solar masses.

But current models do not predict any larger stellar black holes.

In 1783 English philosopher John Michell (the first person to propose the

existence of black holes) suggested that black holes may be detectable if

they were orbited by something that does emit light - such as a companion

star - which would be tugged around the resulting binary system’s mutual

center of gravity.

This is now known as the radial velocity method, and it is one of the main

ways astronomers search for and confirm the existence of hard-to-see

exoplanets as they exert a small gravitational influence on their stars. If it

works for the almost invisible exoplanets, it might work for an invisible

black hole. So Jifeng Liu of the National Astronomical Observatory of

China and his colleagues used the Large Sky Area Multi-Object Fiber

Spectroscopic Telescope in China to search for these wobbling stars, and

found one — a main-sequence blue giant star. The result is published in

Nature.

Follow-up observations using the Gran Telescopio Canarias in Spain and

the Keck Observatory in the US revealed the nature of what they had found.

The blue giant star, around 35 million years old and about eight times the

mass of the Sun, is orbiting the black hole every 79 days on what the

researchers called a “surprisingly circular” orbit. “Black holes of such mass

should not even exist in our galaxy, according to most of the current models

of stellar evolution”, said astronomer Jifeng Liu.

So here is our impossible black hole. It will drive a host of follow up

observations and theoretical work. It is too big to be a typical stellar mass

black hole and far too small to be a supermassive black hole. It is a classic

case of neither big enough nor small enough to exist. Maybe we will find

that a new class of middle sized black holes exists. We shall wait and see.

Washington Academy of Sciences

Delegates to the Washington Academy of Sciences

Representing Affiliated Scientific Societies

Acoustical Society of America

American/International Association of Dental Research

American Assoc. of Physics Teachers, Chesapeake

Section

American Astronomical Society

American Fisheries Society

American Institute of Aeronautics and Astronautics

American Institute of Mining, Metallurgy & Exploration

American Meteorological Society

American Nuclear Society

American Phytopathological Society

American Society for Cybernetics

American Society for Microbiology

American Society of Civil Engineers

American Society of Mechanical Engineers

American Society of Plant Physiology

Anthropological Society of Washington

ASM International

Association for Women in Science

Association for Computing Machinery

Association for Science, Technology, and Innovation

Association of Information Technology Professionals

Biological Society of Washington

Botanical Society of Washington

Capital Area Food Protection Association

Chemical Society of Washington

District of Columbia Institute of Chemists

Eastern Sociological Society

Electrochemical Society

Entomological Society of Washington

Geological Society of Washington

Historical Society of Washington DC

Human Factors and Ergonomics Society

(continued on next page)

Paul Arveson

J. Terrell Hoffeld

Frank R. Haig, S. J.

Sethanne Howard

Lee Benaka

David W. Brandt

E. Lee Bray

Vacant

Charles Martin

Vacant

Stuart Umpleby

Vacant

Daniel J. Vavrick

Mark Holland

Vacant

Toni Marechaux

Jodi Wesemann

Vacant

F. Douglas

Witherspoon

Vacant

Chris Puttock

Keith Lempel

Vacant

Ronald W.

Mandersheid

Vacant

Jurate Landwehr

Vacant

Gerald Krueger

Washington Academy of Sciences

Delegates to the Washington Academy of Sciences

Representing Affiliated Scientific Societies

(continued from previous page)

Institute of Electrical and Electronics Engineers, Washington

Section

Institute of Food Technologies, Washington DC Section

Institute of Industrial Engineers, National Capital Chapter

International Association for Dental Research, American

Section

International Society for the Systems Sciences

International Society of Automation, Baltimore Washington

Section

Instrument Society of America

Marine Technology Society

Maryland Native Plant Society

Mathematical Association of America, Maryland-District of

Columbia-Virginia Section

Medical Society of the District of Columbia

National Capital Area Skeptics

National Capital Astronomers

National Geographic Society

Optical Society of America, National Capital Section

Pest Science Society of America

Philosophical Society of Washington

Society for Experimental Biology and Medicine

Society of American Foresters, National Capital Society

Society of American Military Engineers, Washington DC

Post

Society of Manufacturing Engineers, Washington DC

Chapter

Society of Mining, Metallurgy, and Exploration, Inc.,

Washington DC Section

Soil and Water Conservation Society, National Capital

Chapter

Technology Transfer Society, Washington Area Chapter

Virginia Native Plant Society, Potowmack Chapter

Washington DC Chapter of the Institute for Operations

Research and the Management Sciences (WINFORMS)

Washington Evolutionary Systems Society

Washington History of Science Club

Washington Paint Technology Group

Washington Society of Engineers

Washington Society for the History of Medicine

Washington Statistical Society

World Future Society, National Capital Region Chapter

Richard Hill

Taylor Wallace

Neal F. Schmeidler

Christopher Fox

Vacant

Richard

Sommerfield

Hank Hegner

Jake Sobin

Vacant

John Hamman

Julian Craig

Vacant

Jay H. Miller

Vacant

Jim Heaney

Vacant

Larry S. Millstein

Vacant

Marilyn Buford

Vacant

E. Lee Bray

Erika Larsen

Richard Leshuk

Alan Ford

Meagan Pitluck-

Schmitt

Vacant

Albert G. Gluckman

Vacant

Alvin Reiner

Alain Touwaide

Michael P. Cohen

Jim Honig