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OAR Box 1112 

Prepped by Ryan Dugan 

Document Number: 

5) ll-B-2b 

Docket Number: 

A-83-22 

Printed 4/16/2008 9:12:05 AM Sheet 5 of 97 
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ARCON'NE NATIONAL LABORATORY 

9700 SOUTIH CASS AVENUE. ARQONNE. llliNois 60459 TEIEPIIONE 512/972- 84 30 

February 15, 1985 

Dr. William Yule 

Department of Psychology 

Institute of Psychiatry 

DeCrespigny Park 

London, SE5 8AF 

England 

Dear Dr. Yule: 

I have been asked by the people in the U.S. Environmental Protection 

Agency's (EPA) Office of Air Quality Planning and Standards to talk to you 

about an important matter. 

As you may know, the EPA is charged by the Clean Air Act with setting 

and revising National Ambient Air Quality Standards (NAAQS) for selected 

pollutants, at levels sufficient to protect the public health with an adequate 

margin of safety. The scientific bases for these standards are presented and 

reviewed in criteria documents. As one aspect of the review process, EPA 

assesses health risks by identifying the most sensitive populations for each 

pollutant and estimating probabilistically the numbers of people in the populations who may suffer each of various well-defined adverse health effects 

attributable to the pollutant. It is believed that information about the 

health risks associated with various potential standards will aid the EPA 

administrator in selecting a standard that, in his judgment, protects the 

public health with an adequate margin of safety. 

Because the risk estimates that EPA seeks are often based in part on 

dose-response relationships and lead exposure estimates which are uncertain, 

it is necessary to make probability judgments about relevant dose-response 

functions based on the available evidence and to probabilistically estimate 

lead exposure under alternative NAAQS. Obtaining the health risk estimates 

then involves combining dose-response and exposure probability estimates. 

The EPA believes that it is important and necessary to use the scientific judgments of the best and most knowledgeable people to extrapolate from 

the available data to the needed dose/response functions. The extrapolation 

is not certain and it depends on one's interpretation of the literature. 

Thus, different people will have different judgments. For each health effect 

we intend to obtain the probabilistic judgments of five people to sample the 

range of respected opinions. The model for estimating risks will not merge 

these judgments into a single average judgment, but rather will estimate the 

range of risks based on the range of judgments. This will show the EPA 

administrator a range of risk estimates based on a range of judgments. We . 

will also be able to show some of the sources of tlie disagreements. Indeed, a 

side benefit that we expect from this exercise Is to help identify sources of 

greatest disagreement. 

U.SDI|AKMMI M ol rMivV Hi, LKKiusiivol ( ]lli< A((() 
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Dr. W. Yule 2 February 15, 1985 

Based on the evidence in the lead criteria document, two populations 

have been identified as being most susceptible to the effects of lead intoxication. One is children from birth through the seventh birthday and the other 

is pregnant women or, more precisely, the fetuses being carried by the 

pregnant women. A number of adverse health effects have been identified for 

which we would like to estimate dose-response functions. 

Because of your experience and knowledge of lead and its possible 

neurological effects, we would like to invite you to work with us on this 

matter and serve, if you will, as an anonymous expert specifically on leadinduced IQ decrements among children. 

The committment on your part would be to •* 'end approximately 1-1/2 days 

with myself and Dr. Tom Wallsten from the University of North Carolina. We 

would, of course, do the traveling and would like to meet with you on two 

occasions in a 3-day period. On the first day we would familiarize you with 

the process of judgmental probability encoding, discuss the relevant literature on lead health effects, obtain your initial judgments, and explain how 

your judgments would be used in the risk assessment process. On the second 

day, we would refine your judgments. The first meeting would require about 6-

7 hours of your time, and the second meeting would require about 2-3 hours. 

After returning to the U.S., we would put together a packet of information about your judgments and send it to you for your review (and revision, 

as needed) as part of the process of finalizing your probabilistic judgments. 

To help you plan, it is our hope to be able to visit you some time in 

May. It would probably be best if we could meet with you on Monday, May 6 and 

Wednesday, May 7. This would fit nicely with our plan to visit with Dr. 

Winneke of the F.R.G. on May 1 and 3. However, all of this depends on your 

and his availability. (Incidently, we also plan to include Drs. Dietrich, 

Ernhart, and Needleman of the U.S. in the study. We hope to obtain their 

judgments before traveling to Europe.) 

If you agree to participate in this very important and ground-breaking 

study, I will send you more information about the study, including the protocol that we intend to use to facilitate the process of obtaining your probabilistic judgments. 

I would like to arrange a phone call with you soon to discuss these 

matters. Perhaps you could let me know (via TELEX?) of some good days and 

times of the day to call you. My TELEX number is TWX 910-258-3285 US DOE-CH 

ARGN. 
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Dr. W. Yule February 15, 1985 

All of us sincerely hope that you can take part in the 6tudy. Your 

judgments are important to Che U.S. EPA, and your participation will be 

greatly appreciated. 

Sincerely, 

foulb 

Ronald G. WhitfielH, Ph.D. 

Decision and System Sciences Section 

Energy and Environmental Systems Division 

RGW:bf 

bcc: T. D. Wolsko 

T. Surles 

J. Peerenboom 

T. Wallsten