OAR Box 1112 

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A-83-22 

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ENVIRONMENTAL PROTECTION AGENCY 

In the Matter of: 

SCIENCE ADVISORY BOARD 

CLEAN AIR SCIENTIFIC 

ADVISORY 30ARD (CASAC) 

SUBCOMMITTEE ON LEAD 

Wednesday, 

May 15, 1985 

Rosslyn Room A 

Rosslyn West Park Hotel 

19 00 N. Fort Myer Drive 

Rosslyn, Virginia 

The above-entitled matter came on for hearing, 

pursuant to notice, before: 

DR. MORTON LIPPMANN 

Chairman 

DR. JULIAN CHISOLM, JR. 

DR. ANITA S. CURRAN 

DR. BEN B. EWING 

MR.' ROBERT FLAAK 

DR. ROBERT FRANK 

DR. PAUL B. HAMMOND 

DR. LLOYD HUMPHREYS 

DR. PAUL KOTIN 

DR. TIMOTHY LARSON 

DR. KATHRYN MAHAFFEY 

DR. M. GRANGER MORGAN 

DR. D. WARNER NORTH 

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SUBCOMMITTEE MEMBERS (Cont.) 

DR. RICHARD ROYALL 

DR. ELLEN K. SILBERGELD 

DR. JAMES WARE 

- also -

DR. TERRY YOSIE 

Executive Director 

Science Advisory Board 

Environmental Protection Agency 

Also In Attendance: 

MR. COHEN 

MR. JORDAN 

MR. HAINES 

MS . SLEDGE 

MR. O'CONNOR 

MR. GLEASON 

DR. SCHWARTZ 

DR. WHITFIELD 

DR. WALLSTEN 

DR. ROSEN 

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PROCEEDING S 

2 CHAIRMAN LIPPMANN: We reviewed some of the critical 

3 issues that we need to help OAQPS resolve with their preparation of those drafts and the staff paper. And we will 

review others this morning 

I think we will ask the staff to recapitulate what 

7 they view as our consensus recommendations on the issues 

8 we've already discussed so I can make sure that we all have 

9 a clear understanding of it. And that if there is any confusion, we can resolve it now. 

n Jeff, are you going to do that, or John? 

12 MR. JORDAN: I think I've been elected to try. We 

13 ' will all try. 

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 _ CHAIRMAN LIPPMANN: The largest target — 

15 MR. JORDAN: We'll all try it 

16 I think we had a good exchance of information yes17 terday. I think we learned a lot-. And I think we can take 

18 what we learned and put it into perspective. 

19 I'd like to try to just summarize what I think we, 

20 as the staff, .heard yesterday from the Committee and then get 

2i" "you to feed me back. 

First of all I think, as we sort of anticipated, 

we need to do a bit more work on the averaging time. I don't 

think the information we presented was persuasive enough to 

make the Committee to say a month is the right time, or 

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1 something shorter than a month may be the right time. 

2 So in the next version of the staff paper, we will 

3 broaden our analysis on that and get more specific, and get 

4 much better defined. 

5 | Second of all, I think there was a lot of debate 

6 about who we were trying to protect with this standard. I 

7 think that Dr. Morgan talked about better studying the objec8 tive function. 

9 Deep in the bowels of the staff paper, when we talk 

10 about the exposure analysis, we do, in fact, identify that 

n we're not kids that are exposed to lead chip paint. We want 

12 to bring that up to the front of the paper. I think most 

13 ' people say, right off the bat, we ought to make that statement 

14 so that it's clear and concise right at the beginning of the 

15 staff paper. 

16 That we ought to identify better who we are trying 

17 to protect with the standard. So we will do that, and we will 

18 work with Jewell (ph) and Dr. Hossleblack to see if we •• 

19 can't come up with a distributional function that will repre20 sent the so-called homogeneous population that's out there. 

2i' * Is that a fair statement? Of removing that per22 centage of kids from it. 

23 Then, in terms of the critical health effects, we 

24 had quite an exchange of information on that. And I apolo25 gize. There seemed to be some confusion between what we were 

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talking about with the mean of the population and then fill 

in the distribution. 

So, in our presentation, we will try to improve 

and maybe more clearly state what we're trying to protect 

5 in terms of the distribution. 

6 But I think the couple of things that I heard from 

7 the discussions we had yesterday was that I believe it was 

8 pretty clear that most of the scientific community was 

9 saying, "When you get to 25, you're really in an area that 

10 there's a lot of concern." And that no kid should reach '2 5. 

n That would be an area of critical concern. 

I think I also heard it said that just as an upper 

13 bound of what you should be shooting for and, perhaps, the 

14' best "way I can put it into words is you ought to have a very, 

very low probability of having any kid who you can protect 

with an early extended (ph) from exceeding 20 micrograms 

per cubic deciliter of blood lead. 

18 As low a probability as you can reasonably achieve 

19 of keeping any kid from exceeding 20. That's a little dif20 ferent from saying there's,no probability that some kid would 

21' . "reach 20.* 

On the other hand, I did hear a lot of concern or 

23 expressions about kids getting blood lead levels much below 

24 15. It seemed like the range between 15 and 20 was where 

25 most people were focusing. 

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So I believe what I was hearing is you want to 

2 keep a very low probability that any kid would reach as 

3 high as 20. And I didn't hear a lot of concern about trying 

to set a standard that would keep kids from having a blood 

lead level below 15. 

So that's sort of the way we understood it. And 

I'll open it up for your feedback to me . 

CHAIRMAN LIPPMANN: Does anybody want to comment 

on that? 

D r. Chisolm. 

DR. CHISOLM: Thinking over the end of yesterday's 

12 -discussion, if we go — I think it's in the staff paper but 

13 it's also in Chapter 13 to the Punelli paper on blood FEP 

14 relationship. 

15 And if you accept that a normal range is the mean 

16 plus or minus 2 standard deviations, and you look at this 

17 thing, you would see that after you take into account the 

18 natural frequency, which is mainly effective iron deficiency 

on FEP, that that seems to intersect the line at about 25 

somewhere there. 

* In other words, the mean pius 2 standard deviations 

rises above this natural frequency. And at 10 percent, that's 

about the estimate, I think, of iron deficiency in the young 

24 child population. It's on page 1342 at the top. 

25 I think it's about the only thing, besides ALAD 

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where you really have dose population response data. And 

2 it's a bit of data that you can stand on. Whereas, the 

3 others — now, the mean has to be down somewhere around 12 , 

or so, I think, to achieve that, 

5 If you take the log normal distribution geometric 

6 mean would be somewhere down around 12. But I think that's 

7 a fairly solid piece of information that you have to go on. 

8 CHAIRMAN LIPPMANN: It would seem to be roughly 

9 consistent but your conclusion is stated somewhat differently. 

10 DR. CHISOLM: But you could pin it to something--

n j else. And that's been replicated too. There are a number 

12 of things that show when you get down the range, that the 

13 FEP is related poorly to the indices of — quite clearly to 

t he indices of iron deficiency. 

15 CHAIRMAN LIPPMANN: Dr. Curran? 

DR. CURRAN: Well , I looked at all of these num17 bers again very carefully last night too, plus: some of the 

18 information that Dr. Larson gave me . Also realizing that 

19 there is a minimum level or a very small number of children 

20 who are not ev.er going to get down regardless of what we 

2i -do to the air lead, for a variety of reasons, I think your 

22 statement that you just mad e really reflects what I feel. 

23 And I was looking at it from the point of view of 

24 the statistics that were presented to us in that 7-42 in the 

25 staff paper. And based-upon that, the mean that is between, 

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i say, 8.5 and 9 would bring this in a position where we would 

2 have a very, very small number of children. 

3 DR. KOTIN: 7-42? 

DR. CHISOLM: 7-42 in the staff paper. 

5 DR. CURRAN.: Page 7-42. There's no Table 7-12 — 

6 7-11. 

7 DR. KOTIN: Yes. It's on page 7-41. 

8 DR. CURRAN: Table 7-11 but it's page 7-42, 

9 VOICE: 7-41 

10 DR. CURRAN: 7-41? Well, my book says 7-42. I"'m 

11 sorry. I have a different book than the rest. No wonder 

12 I'm not with the rest of you. 

13 DR. CHISOLM: Is it Table 7-12 or 7-11? 

14 • DR. CURRAN: It's Table 7-11. And in my book it's 

15 on page 7-42. I mean, the other people have different books, 

16 apparently. 

17 Anyway, based upon that, the micrograms per meter 

18 cube of 0.50, giving you a predicted geometric mean of 8.51 

with a maximum blood lead of 18 to 19.9 depending on which 

standard deviation you use fits in the area that I feel most 

comfortable with knowing that this means that theoretically 

some children could get up to 20, not necessarily meaning 

that they do. 

And also knowing that from the point of view of 

reality, the child who gets up to 20 today may not necessarily 

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1 be the one that gets: up to 20 tomorrow. And, therefore, 

2 that level is something that I feel I could live with. And 

3 that reflects exactly what you have just said 

CHAIRMAN LIPPMANN: Okay. I think we can move on, 

then, to some other issues 

6 MR. JORDAN: I guess the next one would be exposure. 

7 MR. COHEN: Yes. The table that Anita just referred 

8 to is part of the next topic that we'd like you to address, 

9 and that is relating various air lead levels to blood lead — 

io hypothetical blood lead distributions. 

And we present three approaches to the staff paper 

in order to do that and we'd like your comment on their ultimate uses either selecting one model or should we use the 

the tiiree- different models? What parameters that we identify, 

should we be focusing in on, for instance, what blood lead/ 

air lead ratio seems to be the most appropriate? 

And on possible ways we can improve the use of 

18 those models 

19 CHAIRMAN LIPPMANN: There are some "differences, but 

20 not great differences in the three approaches, 

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22 should prefer one approach over the other? 

23 DR. MAHAFFEY: Is that page 1 of — 

24 MR. COHEN: Pardon me? 

25 DR. HAMMOND: 'Give the page number. 

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MR. JORDAN: Oh, pag e 7-12 , Tabl e 7-12 . 

VOICE: 7-41 ? 

MR. JORDAN: Or 7-42 depending on .which version 

has gotten the — 

(Simultaneous conversation) 

DR. MORGAN: Well, it strikes me that perhaps when 

you go back through and focus your argument about exactly the 

target population, you may be able to tighten somewhat your 

preferences or change or reproduce a model that's slightly 

more reflective of what you're after. 

But I personally found the strategy of several 

-alternative plausible models and using them to fulfill some 

confidence in the kind of answers you got. One of the more 

appealing aspects of this document, the explicit recognition 

that there are several alternative ways to approach such'a 

problem, and the explicit building of some alternative 

models and exploring the extent to which the answers depend 

upon the model you use, struck me as most appropriate. 

And rather than a move towards convergence on one, 

I would argue .that you persist in the direction you started 

"in, namely, of building an argument towards an answer and 

buttressing it with a variety of alternative analytical procedures which together, then, build you towards some defensible position. 

I think what you've done is appropriate. 

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CHAIRMAN LIPPMANN: I think it's interesting in 

2 that light that while the convergence of the predictions 

3 . is relatively good at the 1.5 air lead level, there's more 

relative difference between the predictions when you're down 

around .5 air lead level, which is where you're probably 

6 going to end up. 

7 So I don't know whether that presents any problems 

8 in giving you a greater range of prediction. But it's 

certainly something to note. The lower you go in air lead 

10 level, the more divergent the predictions become. 

n DR. MORGAN: Right. And it strikes me that the way 

12 one begins to get leverage on that is not so much by beating 

13 the daylights out of these models as it is working more on 

14 sharpening the focus of exactly what it is you're trying 

15 to model since most of the discussion we heard yesterday 

16 struck me, at least, as a discussion over exactly what it was 

17 I was trying to represent with these models. 

18 CHAIRMAN LIPPMANN: To what extent do you have 

19 data which tests these predictions? Because during the 

20 course of NHANES you had at least some of the population 

represented by ambient air monitors, and you had blood lead 

levels. 

And while both blood lead and air lead were changing 

at least during part of that data set you were in the half 

microgram per cubic meter air lead range. And where you could 

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1 identify the children whose blood was collected as being 

2 appropriately represented by a monitor, you could compare 

3 the air lead/blood lead that was actually observed. 

MR. COHEN: There are some limited opportunities 

5 to validate these predictions from NHANES. For example,' in 

6 the criteria document, the city survey — had an average 

7 air lead level of 1.2 during the period of the survey. 

8 And the children in those cities had an average 

9 blood lead of approximately 15.6 micrograms per deciliter, 

io And if you — 

n CHAIRMAN LIPPMANN: Well, that's pretty slippery. 

12 If you averaged two things which both may be curb or linear 

13 and looking at grand averages, I'd rather disaggregate that 

i4 part"and segregate either the air lead or the blood lead 

15 since they are narrower ranges and look for the corresponding 

16 other values to see how they test the model over the range. 

17 VOICE: You'd take the cities — 

18 CHAIRMAN LIPPMANN: Well , it's..their cities or 

19 times since the levels were changing. It may be picking the 

20 right year and the right city. But you would seem to have 

2i' . -available to you a relatively robust data set to test these r 

22 models 

23 And if you can test the models, that would be 

24 valuable for this criteria pollutant exercise and others as 

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DR. MORGAN: Could I put in a pitch also for at 

least considering a bit of graphical presentation of some of 

these results? 

Table 7-11, for example, could nicely be combined 

with some cumulative distributions which would give people 

who are not quite as versed in probability rather a more 

concrete notion of what it is that these numbers correspond 

to. 

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CHAIRMAN LIPPMANN: Tim, we're looking at Table 

7-12 in the staff paper, page 7-42 in my copy anyway. And 

the issue is whether to look for evidence of one of the three 

approaches, is it better than the other. Or, as Dr. Morgan 

"has suggested, continuing to use all three to look for the 

robustness of the predictions. 

, Did you have any specific opinion on that? 

DR. LARSON: I would agree that no one of them is 

overpowering or convincing. Therefore, I think it's good 

to contrast and compare all three approaches straight from 

the argument. 

CHAIRMAN LIPPMANN: Are there any'other -opinions 

on this topic? 

(No response) 

I think we will encourage you to keep an open mind, 

then, to use them as they best serve your purposes. 

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MR. JORDAN: I would just highlight that there is 

another effort that we have underway to sort of even broaden 

what we have here in terms of exposure. And that is actually 

developing and building an exposure model. We're trying to 

at least account for a little bit of movement of people 

from various microenvironments and see if we can get some 

idea of how that, itself, may .influence the blood lead level 

rather than putting it into an environment where the air 

lead is assumed to be constant. 

That is a much more diffcult problem. And, as you 

remember, we looked at that once before. We modified a lot 

based upon the last conversations we had. And that will 

hopefully be in the next version of the staff paper. 

CHAIRMAN LIPPMANN: I think that provides additional 

insights. I'm not sure how relevance it is to this discussion because you're taking a control activity on ambient air 

lead so as to influence blood lead. 

And, therefore, it may be most appropriate to look 

at central station air lead and it's influence on blood lead 

directly for this exercise, not negating the value of the 

other exercise fdr other reasons. 

MR. JORDAN: But as you control air lead, you begin 

to also reduce some of the other microenvironments. And 

that's what we were trying at least to be able to attempt 

at column 4 in the simulation model. 

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1 CHAIRMAN LIPPMANN: But let's discuss that in its 

2 own context. 

3 MR. JORDAN: Yes , fine. Yes . 

4 CHAIRMAN LIPPMANN: Dr. North? 

5 DR. NORTH: I think it's important not to lose sight 

6 of the importance of the indirect route. And that suggests 

7 to me that looking at the microenvironments may be extremely 

8 important to.try to get a better insight on perhaps what 

9 aspects of the indirect route are most important. 

io If we're worried, for example, primarily about 

n wind — dust, are we worried about situations where children 

12 are playing near busy city streets? A t this point we don't 

13 seem to have too much insight in these models as to what the 

14 leading term might be. 

15 I think that that can be obtained by looking at the 

16 more disaggregated approach and it will be extremely valuable 

17 in, among other things, understanding the strengths and weak18 nesses better of the three existing approaches. 

19 CHAIRMAN LIPPMANN: Okay. 

20 Do you want to go on to another topic? 

2i ' . MR. JORDAN: The only other one I think, if I recall 

22 the things we had on the list up there, was the form of the 

23 standard. And we said we preferred to move to a statistical 

24 form of it for reasons that we've discussed. 

25 Because all the rest of our standards, we just feel 

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1 that that's a more robust statistic, it's a better approach 

2 to dealing with the way things appear in nature. 

3 So we are structuring our analyses and building 

toward converting to a statistical form of this standard. 

5 I think Jeff laid out a couple of approaches to that for you 

6 that we will have under consideration. 

7 And any advice, any guidance that you might have, 

8 we certainly want to hear it. 

9 CHAIRMAN LIPPMANN: Dr. Morgan? 

DR. MORGAN: Yes. That's on my list also, some-*-

n thing I'm very anxious to see us talk a bit about. 

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I find this intellectually very appealing. I'm not 

sure that — I guess I don't know enough about lead to know 

how much importance it is in the specific context of lead. 

15 But in general, the strategy is clearly very appealing. 

However, on reading the document, I came away feeling quite uncomfortable because it wasn't clear to me what 

would constitute a demonstration of having met the standard. 

And it strikes me that you need to talk at somewhat greater 

length about issues of measurement and enforcement. 

* I mean, given that you've got a standard that's 

stated in this frequent — this fashion rather than as a 

single hard target, what do I have to do to demonstrate that 

I'm in compliance? 

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around it. If I'm consistently high but don't come outside 

of the range, am I in compliance? I mean, how do I know, 

until I've gone for quite a few years, what the statistics 

of the new time series look like? 

And so how can I persuade you that this one 

exceedance was, indeed, the 1 percent event that I'm allowed 

rather than the 20 percent event that you're telling me 

I'm not allowed? 

I'm not expecting answers from you now. But I'm 

saying that it strikes me these are issues that will arise 

and that clearly need to be talked through at greater length. 

MR. HAINES: Let me respond in this fashion. 

Typically, when we came down and proposed these, 

"we had developed fairly extensive appendices that go out as 

part of the proposal package doing exactly what you're saying, 

explaining to people what the attainment test is, how you 

calculate the data, et cetera. 

And so we set forth clearly in the proposed regulations what the requirements are. 

With the tolerance interval approach, frankly, we 

have to look at the data and we have — there's a series of 

issues we have to look at, how we specify a tolerance interval. More importantly, how would we derive one. Do we do 

it on a locality specific basis to derive that tolerance 

interval based on looking at ail the national data? 

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1 There are some hard questions we have to examine. 

2 And we plan to do that in the next several months and decide 

3 how viable that approach is vis-a-vis the expected exceedance 

4 for it. 

5 MR. JORDAN: I guess, Dr. Morgan, what John is 

6 saying is we always do that in the final emphasis. I mean, 

7 where we propose a'statistical form of the standard like 

8 the ozone standard, there are other forms of the standard 

9 where we do that. 

10 We actually, in the regulation, do write up and 

n are required to put into there how we would do it. We had.' 

12 thought of doing it in the staff paper, itself, but it could 

13 be done if that's what — 

14" ~ '"' DR. MORGAN: Well, maybe it's not necessary. The 

15 reason that I react that way is that given the earlier dis16 cussions about converting the shorter averaging times and 

17 the ambiguities about the data sets, and so on, it strikes me 

18 that it's tightly coupled with that other issue. 

19 It means if you're going to have a probabilistic 

20 standard, you've got to make sure that you've got the data 

21 in hand that are necessary to implement it.' And since that's 

22 also coupled to the first half of the argument, the two seem 

23 logically to fit together.in some ways. 

24 MR. JORDAN: Absolutely. They do fit together. 

25 In fact, the level of health protection that you ultimately 

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end up with is very strongly dependent upon both the form of 

the standard and — 

DR. MORGAN: I guess I could care less where it gets 

written down than it gets fairly thought through and written 

down before rather than after the Committee looks at it. 

MR. JORDAN: Right. 

DR. NORTH: I'd like to tie this to the point I was 

just raising to the importance of the indirect route. It 

seems to me that because lead is so unusual in terms of the 

importance of the indirect route, that makes it all the more 

important to layout clearly how this standard is going to be 

used as a yardstick in order to determine compliance. 

For example, some very careful treatment of wind 

'velocity, as it generates dust, might be in order. It seems 

to me what you should do is to explain that and give some 

examples. 

MR. JORDAN: Okay. 

CHAIRMAN LIPPMANN: Somewhat along the same line, 

the sampling, now, is done with the so-called high volume 

sampler which has a variable in the cut size depending on 

wind, speed and direction. A sample every Sixth day doesn't 

look into the observation that lead in the air is a bimodal 

in size distribution, and that the interpretation of things 

could be, perhaps, materially added by looking at fine lead 

and coarse lead separately which would relate in part to the 

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i secondary transmission of deposited material. 

2 Do you anticipate in the next graph laying out your 

3 thinking and options on the sampling? Because it seems to 

4 me that very little thought went into the standard sampling 

5 in the 1978 standard. Whether there's any justification- for 

6 a 24-hour sampling interval and the frequency of every sixth 

7 day, especially as you get to a statistical form. 

8 Obviously, when you have a relatively infrequent 

and a very rotating weak schedule, it gets sort of arbitrary 

as to whether you're going to catch an exceedence or not.-

Of course also, now, it's different from 1978 in 

terms of sampling in that we're dealing with very much lower 

levels of lead in the air already, let alone those that the 

standard may drive to lower levels. 

So the analytical sensitivity ma become more of 

an issue. So I think it's, in part, a policy issue and we 

have to steer clear of that. But I view it as a scientific 

18 issue. What is the scientifically defensible means of charac19 terizing ambient air levels? 

20 And-it depends, in part, on your definition of 

•averaging time that would drive the sampling somewhat.. But 

there should be consideration of, perhaps, contijious sampling 

over seven days at lower volumes as compared to a snapshot 

in time every sixth day that has an advantage of giving you 

more material to collect, perhaps, and, at the same time, 

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getting a more complete description of exposure since you're 

not losing any time without increasing the number of samples 

to be analyzed. 

These are all options that relate, I think at least 

• in part, in strong'part, to the scientific judgments we can 

help you with. And although they may effect policy decisions, 

I think we can look at them realistically in terms of their 

scientific credibility. 

DR. WARE: When you sample one day in six, is that 

always a particular day of the week? 

CHAIRMAN LIPPMANN: That was part of the design. 

It's alleged to, over a year, sample every weekday at equal 

. levels. So it has some advantages for some kinds of monitoring. I'm not sure it's appropriate to this pollutant. 

MR. HAINES: I ugess in response to your several 

questions here, we do have underway analysis, trying to 

examine what should be the best frequency of sampling, particularly in'light if'we went to a monthly or shorter averaging 

period. 

We appreciate your comments with regard to the 

instrument, itself. We have not given great thought, at this 

point in time, of moving away from the high volume sampler . 

is the device to either a low volume as you suggest. We will 

have to explore that. 

CHAIRMAN LIPPMANN: Well, we certainly have to 

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explore it, at least. Whether, in fact, you want to get 

2 stuck with a high volume sampler, if you want a PM-10 in it 

3 or not, I'm not saying one or the other. 

But you certainly would have to explicitly address 

5 j the reasons for not putting an inlet of any particular kind 

6 on the sampler. And you should certainly address the issue 

7 of whether to collect fine and coarse separately, whether 

8 at high volume or at lower volume 

9 Those are different issues from the sample duration 

DR. MORGAN: Yes. 

CHAIRMAN LIPPMANN: So I hope that in the next staff 

12 paper you will address those issues 

13 Tim, would you like to comment on those points? 

14 ~ DR. LARSON: I think they're definitely worth 

15 thinking about. And perhaps in some guide to that thinking, 

16 you might want to look at the relative amounts of total 

17 particulate matter on your filters relative to the amount of 

18 lead because that is some index of the variability of the 

composition of the fraction of lead within the particles 

which may spea#k to this frequency distribution issue 

* Because if they're a relatively constant fraction 

of lead and particulate matter, then you have an entirely 

additional data base on which to help guide your judgments 

But there's no sense in that. I mean, it may not be appro19 

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But I was interested when we were looking through 

the peak to mean ratios in urban areas as opposed to — 

sources whether or not those same peak to means were observed 

for TSP. 

CHAIRMAN LIPPMANN: That's certainly — Tim has 

been bringing us back repeatedly, and I think wisely, to the 

issue of the peak or — point sources, especially as the 

.phasedown reduces our concern about exposure in much of the 

rest of the country. 

And the issue Dr. North raised becomes so important. 

The typical distribution between fine and coarse may be quite 

different when you look at specific industrial — sources. 

It's just further reason, perhaps, for taking a good hard 

'look "at what you want to do in sampling. 

DR. MORGAN: I guess I might put in a plea too that 

in thinking about the sample or the measurement necessary 

for standard enforcement, that you also reflect on the fact 

that you will be back here, or your successors will be back 

here in a few years, talking about lead again. 

And it would be nice if the data set that you 

develop for enforcement purposes is also a data set that 

helps you to do a more:intelligent job next time you have to 

do an iteration on this. And I wouldn't lose track of that 

fact in the process of designing your measurement process. 

CHAIRMAN LIPPMANN: Any other comments? 

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DR. MORGAN: I have one on a different subject. 

MR. JORDAN: There's at least one more thing we 

needed to talk a little bit about, and that's the secondary 

standard. We haven't discussed that at all. 

CHAIRMAN LIPPMANN: So before leaving the primary 

standard, is Dr. Morgan's additional comment on the primary 

standard? 

DR. MORGAN: Yes. I wanted simply to put in a plea 

that if you have not, that you take off Frank's comment about 

the role of lead from smoking, seriously, because it has 

clear policy ramifications. I mean, it introduces a dimension of voluntary exposure which sort of mucks up additionally 

some of this. 

And it strikes me that a little bit of reflection 

on that whole issue might be in order. You may be able to 

simply demonstrate that it's a second order of fact to 

compare it with the things that you talk about. It strikes 

me that if you have thought it through, fine. 

It may would be appropriate to just say a little 

bit about your thoughts. 

MR. JORDAN: Okay. We've talked a little bit 

amongst ourselves. I think therels something we can do 

with NHAMES data to — 

DR. MORGAN: Well, we don't need to hear details 

at this point. Just a suggestion. 

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MR. JORDAN: Okay . 

CHAIRMAN LIPPMANN: Okay. Do you want to shift 

our focus, then,.to the secondary standard? And I guess, 

perhaps, if you weren't planning to already, you could introduce the reasons why you need a secondary standard at all 

if, in fact, you really have no convincing evidence that is 

a concern about welfare things. 

MR. JORDAN: Well, okay. I'm not quite sure we can 

conclude we can conclude we have no concern about secondary 

welfare things. I think it's much more difficult to pinpoint 

where those secondary effects are. Those concerns may be 

appearing at probably — are a lot more difficulty than it 

is for the primary. 

The attorneys are here. Maybe they can say something as to why we are concerned about a secondary standard, 

per se, in terms of legal requirements. 

There is one concern I have for having a secondary 

standard, even if you have a secondary standard that's equal 

to the primary standard. Without a secondary standard at 

all, it tends to deemphasize a lot of needed research. 

And if 'you don't have a standard out there it tends 

to turn the research community away from the welfare effects 

which may be occurring out there. So that's at least one 

reason I see for continuing to have one even though you said 

that equal to the primary, it, in effect, doesn't have a 

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i of impact. You meet the primary and you meet the secondary. 

2 So that's one of the reasons I personally push 

3 for having it. 

4 The other reason, I guess, is that the Act requires 

5 you to set one fcr welfare effects if you think that there 

6 are welfare effects appearing out there. 

7 CHAIRMAN LIPPMANN: That's understandable if you 

8 need it to protect the plants, like an ozone or S0_, you have 

9 to take a look at it because you know it can affect the plants 

10 or the materials, or whatever. 

n I'm just wondering where it appears that the effects,, 

12 if any, are much less sensitive than the health effects con13 cerned that are identified in the primary standard, and the 

14 primary standard drives the level to the lowest, why do you 

15 explicitly have a secondary standard? 

16 And you said you have a secondary reason and that 

17 is to help you in the management of the agency and in 

18 directing what may be necessary research for the future. 

19 MR. HAINES: I think we have a primary reason too. 

20 So I think that while the data is weak, et cetera, I think 

2i "they have a high enough concentration to clearly have effects 

22 of lead on many ecu system components. And we're concerned 

about the long term implications of lead in the eco system. 

Then our problem is defining what level of control 

you should have. And we've had to take a backwards approach 

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1 and say, "Will the level of primaries — a full or adequate 

2 protection." 

And our judgment at the staff level is yes, it 

will, following much the same rationale that was used in 

1978. And we also at this review have a situation. Clearly, 

6 from this evidence, there's no way the agency could say 

7 that there's no longer a need to retain a secondary standard 

8 since we've had one set 

9 And I think practically since our rationale in '.78 

10 with animals basically appear to be no more susceptible to 

n man, we ought to adjust the secondary standard at this review 

12 to be equivalent to the primary parallel in that rationale 

13 CHAIRMAN LIPPMANN: Well, one could look at it in 

u another way, that there is already an awful lot of lead out 

there in some soils. And it's fairly stable. It's going to 

be there a long time 

.-, And one could argue whether the increment which is 

18 going to be allowed under the new secondary standard is 

a third, fourth or fifth order effect to the ecological effect 

which may be resulting from past emissions. So, you know, 

can you justify controlling future emissions? 

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Don't you have to show that the incremental addition to the soil will affect plants or animals incrementally 

in order to justify doing that? 

MR. HAINES: I think — let me respond in this 

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fashion. I think there's a great deal of uncertainty oh what 

are the combining capacities of soils throughout the U.S. 

Granted, in certain high lead areas near roadways 

around major point sources, we've done a successful job of 

contaminating that soil where you induce the effects. We're 

at high enough levels. 

Many areas of the country were uncertain how much 

contamination has taken place. And they don't know for certain how much additional capacity for the soil to find this 

lead. So I think it's prudent policy to — prevent it, maintain a secondary standard, maintain it equivalent to the 

primary even though we're uncertain on — 

CHAIRMAN LIPPMANN: Well, operationally, I see no 

"problem, then. If you're not making the states do anything 

they wouldn't do anyway to meet the primary standard. It's 

not really hurting anybody to state that the secondary 

standard is the same as the primary. 

I'm just asking a basic semantic issue of does it 

really have a purpose. 

Jerry, do you want to give us a legal opinion as 

to whether we nee/d a secondary standard? 

MR. GLEASON: I don't know — 

CHAIRMAN LIPPMAN: This is Jerry Gleason from the 

General Counsel's Office. 

MR. GLEASON: I think when the Act was amended 

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in 197 0 the general assumption was that secondary standards 

would usually be more restrictive than primary standards. 

How ell that assumption was based, I don't know. 

But in 1977* the Act was amended again, as you know. 

And somewhere in the hundreds of pages that: resulted, there 

is some language that recognizes that a secondary standard 

might be less restrictive than the primary standard. 

Logically, you would have to ask yourself why do 

you need the secondary standard if the primary standard will 

do it, particularly when it is generally so that the primary standard woul have to be obtained faster than the 

secondary standard. 

It's a logical question. You could say that 

"assuming the primary standard is — that there is no public 

welfare problem left to address, but the Act doesn't clearly 

point in that direction. It says to set a standard based on 

such welfare facts that you perceive might occur. 

And it doesn't really answer the question about 

redundancy. And then when you add in the factor that you see 

possible welfare effects but you're not sure at what level 

they would occur,' then you're into a different problem which 

is doing the best you can in terms of picking a number. 

CHAIRMAN LIPPMANN: Well, or having a different 

kind of standard. One of the options raised in the staff 

paper was having some sort of a deposition standard rather 

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than an ambient air standard. 

2 And that might make sense if there's any basis for 

3 it because it might more directly get at the welfare issues. 

So I think perhaps you ought to lay out the options and 

let's look at them. 

Bob? 

7 DR. FRANK: I wonder, Jerry, is there any means i 

| • i 

6 j of implementing, enforcing a secondary standard at the present!? 

i 

9 MR. GLEASON: I guess I'm not sure quite what J 

io you're 

n DR. FRANK: It's my understanding that there are 

12 time constraints that go along with primary standards. They 

13 must be implemented by a certain period of time or EPA takes 

action. 

15 Is that true for secondary standards? 

M R. GLEASON: The secondary standard, according to 

the Act , has to be attained in a reasonable time. And my 

18 understanding is that the Agency is generally — whether 

there is a reasonable time. And as to what sanctions apply, 

2c I'll let somebody from OAQPS address that. 

2i . - * MR. JORDAN: Two things here. When you develop a 

22 stip, you do develop a stip that ultimately is supposed to 

23 meet the secondary standard 

24 The real claim of impact with the secondary standard 

25 is new sources. You know, when new sources are permitted, 

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they are modeled against the secondary standard. So it does 

have a direct, right now, type of impact. 

DR. MORGAN: Can we go back to the point about — 

or maybe you were going to say the same thing. That if one 

had a secondary standard that was deposition related, that 

basically applies to points — that has a major impact for 

large point sources. 

And it might be correlated with what you do at the 

primary level. 

DR. LARSON: I was going to say I think it raises 

a whole set of issues which may not be scientific in nature. 

But EPA probably through them through. It might be that 

around those areas, there's so much lead in the soil that 

if you have a deposition standard, what you're really doing 

to get appliances in a reasonable amount of time, you assume 

it's going to continue to be windy, you're talking about 

cleaning up the soil, a lot of contaminated soil. 

Because to try deposition monitoring is going to 

reflect previous — in soils and reentrainment. So it raises 

a whole separate set of points. 

MR. HAINES: I think when we laid out that proposition, we recognized we had a lot of shortcomings. And I 

think, exceptionally, though, I think it's appealing. I think 

hopefully we can generate information that some day we could 

set the proper standard-which I think is a deposition standarc 

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1 to get at econological effects. 

2 I think, in very terse fashion, we try to indicate, 

3 while we conceptually find this appealing, that we don't 

know enough now to pursue it with any great vigor with our 

current information basis. 

i j 

CHAIRMAN LIPPMANN: Well , it certainly would serve j 

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MR. HAINES: And that's part of, I think, our moti-j 

9 vation of putting it in is to get people thinking in these i 

I 

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n DR. MORGAN: But I guess I share some of the concerns 

12 that we've been hearing from the Chairman. 

13 It strikes me that if when you're through this and 

14 you think' you know what primary standard you're going to 

15 recommend, if you then take that and multiply it by a factor 

16 of two or three, you haven't got evidence that you find really 

17 persuasive that the resulting number wouldn't be any less 

18 bad as the secondary standard. 

19 Then it strikes me that you're in a somewhat scien20 tifically uncomfortable position. And that the substituting 

2i' -for each "other, while it may do no harm in the short run, 

22 sets sort of a continuing precedent of playing a little 

23 fast and loose in the science that you don't want to be uncom24 fortable about 

25 CHAIRMAN LIPPMANN: Dr. Weing? 

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DR. EWING: I'd like to raise a little bit of con2 cern here to the deposition rate standard. 

3 Conceptually, I have a little problem with it 

because it seems to be moving back away from the measure of 

5 exposure to the organism, whatever it is; concentration in 

6 the soil or concentration in the water. 

7 I In the case of soil, which is a major sync in the 

8 eco system, the deposition rate is really the rate of accumu9 lation or the rate of change of concentration. And it seems 

10 except for foliar deposition, which is a major exposure to 

11 that pathway, except for that, it really isn't the most 

12 direct measure of the dose to the organism. 

13 It would also seem to me that if you already have 

14 an area of high accumulated concentration, because of past 

15 deposition, then you may be approaching a toxic level such 

16 that you might want a lower cumulation rate, or deposition 

rate. So you might want to have to adjust that deposition 

rate as you get closer to some sort of a threshold. 

It just seems to me like it's an awkward way to 

try to get at.the problem. The more direct way is concentration. * 

MR. HAINES: You're talking now of soil concentration, not necessary air concentration. See, we're looking 

at it from the point of view of measuring concentration to 

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And I think you're suggesting ideally you would 

move to — 

DR. EWING: Move to soil concentration or water 

concentration. 

5 MR. HAINES: Right. Which, unfortunately, may 

6 cause us problems within our regulatory framework. 

7 DR. EWING: Yes. The immediate base legislation 

8 you deal that will make that very — 

MR. JORDAN: Maybe I can pass this on to the solid 

0 soil people. 

n (Laughter) 

12 DR. EWING: Maybe you should pass it on to the 

3 Congress. 

14 ~~ MR. HAINES: One other comment, vis-a-vis our data 

15 base, in many cases we have uncertain data and particularly 

16 with relating ambient concentration exposures to the — infor17 mation, we do have, for animals, you know, some reasonable 

data when we have qualitatively — our qualitative assessment 

of the animal toxicology data, et cetera. 

So X think — I don't want to imply too bleak a 

picture that we can't arrive at a rationale that animals are 

not, therefore, susceptible. And our primary health base 

standard should protect most wild and.domestic animals out 

there as a basis for a secondary standard. 

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except for kids who have — you're not talking about direct 

ingestion. 

For your livestock and many of your wild animal 

species, it's very likely that they're eating the lead that 

falls on the foliage with the forage (ph) that they eat much 

more extensively. 

So while they may not be any more or less sensitive 

to a certain blood lead level, they could easily have much 

higher doses from deposited material. We only are getting 

it from food where we don't fully wash the leaves that weconsume. They don't wash them at all. 

And they eat more of the plant material directly. 

We peel away some of the outer plant material. So it's a 

different situation. The sensitivity to the blood lead level 

may be similar but that doesn't mean that the air lead level 

has the same relationship to grazing animals. 

DR. EWING: It seems to me I recall having seen it 

or it was pointed out that horses are particularly sensitive. 

And, as I recall, a comment was made that horses have a 

tendency of grazing and pull the grass up by the roots. And 

•to ingest them, the soil, is attached to the roots with it. 

So they get lead from the soil as well. And that's 

in addition to the folliar deposition. 

DR. LARSON: It's hard to do. But, I mean, in the 

ideal world you would measure lead as a function of the 

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particle size. And you could have estimates of depositions 

2 as well as ambient concentration. 

3 DR. HAMMOND: I suppose I should comment as the only 

veterinarian in the group. 

5 (Laughter) 

6 This issue of poisoning of livestock has been one 

7 that has been identified and has been of concern for many 

years. And although I haven't had any dealings with the 

issue for at least 15 — well, at least 12 years, I do recall 

that the only episodes of clinical poisoning that were ever 

n identified were either in the vicinity of secondary smokers 

and only then when they had some sort of accident like a fire 

13 ' in the bag (ph) house which allowed all these fumes to go 

off into the air, or as a result of paint and battery casings, 

15 and things of that nature. 

But never any episodes reported that dealt with, 

for example, the problem of grazing near freeways. As a matte 

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fied some horses who happened to be passing along the freeway 

to try to get .some idea as to whether the blood level is 

.any different in those animals than it was in those that were <• 

grazing in more remote areas. 

There was no difference. So I think that the experi 

mental evidence, too, in terms of what it takes to — in 

livestock has been very - undefined. And I think that all of 

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1 this reveals that there really is no problem that would 

2 exist, with any kind of a reasonable particle exchange. 

3 In fact, I don't think there's a problem there 

really. And I think the documentation is in it. 

5 b CHAIRMAN LIPPMANN: Nobody's looked at the relai 

i 

6 j tionship of the stature of the animal to lead at lower levels 

7 and productivity to the welfare issue. 

i 

ii 

8 [! (Laughter) 

DR. HAMMOND: We did that back in 1970 when the 

10 air leads were considerable higher and the gasoline consumpn ' tion was considerably higher than it is today, 

2 ; CHAIRMAN LIPPMANN: Well, I don't know if this has 

13 i been very useful to you. Perhaps you ought to outline to us 

14 what ""your thinking is of this secondary standard, and we 

15 can react, then, to that. 

16 Y ou said you wanted to tell us something about 

17 the secondary standard? 

M R. HAINES: No. We've outlined our recommendation 

18 

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and that would be to make it equivalent in all respects. 

CHAIRMAN LIPPMANN: Well , do you feel you've gotten 

2i' "any advice from us in this general discussion which is of 

22 any use to you. 

23 (Laughter) 

24 And if you're only confused by it — 

25 (Simultaneous'conversation) 

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CHAIRMAN LIPPMANN: — and if you're only confused 

2 by it or if we've only confused you, maybe we could clarify 

3 these things. 

MR. JORDAN: No. I don't think I heard you say 

5 anything that we haven't discussed amongst ourselves. I 

6 think confusion, a lot of times, you' know, just states what 

the state of the art is. 

And the things that have been said here are things 

9 that we've sat around the table lots of times and discussed. 

10 And the fact that, as you chime in with these conversations, 

just basically confirm our own suspicions of the lack of 

data and the lack of information out there 

13 CHAIRMAN LIPPMANN: Well, you're not currently 

14 thinking about having any standard other than the reaffirma15 tion of the primary standard? 

16 MR. JORDAN: That's correct 

17 CHAIRMAN LIPPMANN: Although even in our discussion 

of the primary standard, we suggested consideration of something you weren't thinking of like fine and coarse separately 

And if you did. that, then you might want to look at the 

secondary" standard in terms of a different mixture or a different emphasis on fine versus coarse air lead for its 

23 different reasons 

24 I guess I would like to see you more explicitly 

25 address this secondary standard and talk about any other basis 

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1 than than the primary standard if it's possible to do so. 

2 (Pause) 

3 Have we finished our discussion of your presentation or do you want to emphasize anything else on that? 

MR. JORDAN: No. 

6 CHAIRMAN LIPPMANN: Does anybody else want to offer 

7 any opinions on the secondary standard? 

8 MR. JORDAN: I'd just like to have Dr. Ware to 

9 have an opportunity to make any comments. I'd appreciate 

anything that you might add to the staff paper. Would you — 

DR. WARE: Well, I'm sorry that I couldn't be here 

for the first part of it — of the discussion yesterday afternoon. But I'm going to say first that I was really impressed 

with "the thoroughness of the staff people. I thought it was 

15 an impressive document. 

And I'm really amazed at the amount of research 

and synthesis that goes into these documents. So my overall 

impression was a very positive one. 

I didn't even have an opportunity to hear the 

discussion about the statistical form of the standard. I'm 

assuming'that that was well received. That there wasn't any <" 

22 serious criticism of that concept although I felt the discus23 sion of the specifics in the staff paper was not satisfactory. 

I mean , there was — the ideas put forward were 

not put forward very clearly, I didn't think. And moreover, 

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it didn't seem to me that they were thoroughly worked up 

2 yet, 

3 So I think there is some room for improvement. And 

I recognize the need for a statistical form of the standard, 

5 I'm in favor of that, but I think obviously some work is 

6 needed to develop exactly what that would look like, 

7 MR. JORDAN: On this point, Dr. Morgan brought the 

8 same point up in a discussion. And I told him basically 

9 we normally do this type of discussion in the regulatory 

10 package when we actually promulgate or propose a standard: 

n We have not, in the past, brought that forth in the staff 

12 paper in a full discussion, but there's no reason we can't 

13 do it, 

14 " ' And your point is well taken, that in this year we 

15 just sort of mentioned the statistical form of the standard 

16 and, you know, it's sort of — that kind of thing. But I'd 

17 be glad to talk to you some more about it. 

DR. WARE: Okay. 

MR. JORDAN: Where's the appropriate place to 

18 

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20 put it? 

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DR. WARE: Well , I'd be'interested at the appropriate time to hear how that's coming. 

2 3 MR. JORDAN: Okay, 

24 DR. WARE: I didn't get a chance to hear the dis25 cussion about the quarterly versus the monthly averaging time 

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either. 

And my general inclination about these issues, first), 

I thought I would like to know more about whether there's 

good evidence for differences among sites and, say, the variability of the month-to-month variability, given that there's 

not really dramatic, severe, or not such dramatic difference.s, 

then I would be inclined to stay with the quarterly standard 

because of the convenience — because of the lack of problems 

with monitoring. 

But to set the quarterly standard in such a way" 

that month-to-month excursions would be adequately controlled.. 

I don't know what the discussion was like. I think the 

counter argument to that would be to point to sites which, 

in fact, are atypical and are more variable from month to 

month. 

And if that kind of problem arose, then it would 

give you concern. You would feel- uneasy about the quarterly 

standard. How did that discussion go? 

MR. JORDAN: I tried to summarize it up this morning with the one sort of center site. I think not too many 

people were very comfortable with the discussion that we 

had on the averaging time in the staff paper. And we just 

simply need to go back and beef that section up. 

We never really anticipated that we were at a point 

to really finalize up that discussion on the averaging time. 

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1 And so we feel that we'll have to go back and take right 

2 into consideration the things that you're talking about here. 

3 So we didn't expect or didn't get any clear consensus from the Committee in terms of what the averaging 

5 times would be. 

6 I would appreciate any recommendation and guidance 

that you might have on how to use what available data you've 

8 got. 

9 -DR . WARE: Okay. Well, I do think from my point 

of view, I think there are two key issues. First, there's 

i, the biological issue about what the sort of biological 

averaging time is. And you argue that you think that there's 

reason to suspect it may be shorter in children than in 

adults. 

And then the other issue, it would seem to me, would 

,again be — and I think the one you can get at from your 

air quality data, is the extent to which you give some data 

on the ratio of maximum monthly mean to the quarterly means. 

19 And you show that those are numbers around 1.4. 

20 Now .the question would be how heterogeneous are 

21' . -those when you take individual sites and average those ratios 

22 over time. How heterogeneous are those ratios for sites? 

Are there sites that, in fact, have very unstable month-tomonth values or a subject to particularly, I think — to tie 

in another point — since the lead phasedown is going to 

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1 reduce the problem of lead concentrations away from areas 

2 near point sources, it would seem to me that then the ques3 tion would become are point sources likely to be subject to 

these short term fluctuations, and they well may be, actually, 

5 When you put it that way, you may be able to make 

6 a good argument. But it seems to me that's the argument that 

has to be made, that the point sources that you're concerned 

8 about are subject to short term fluctuations. 

9 And so quarterly averages really wouldn't do it. 

MR. JORDAN: Okay. Point well taken. We will " 

beef this whole discussion of the averaging time. 

DR. WARE: The other thing I wish I could have 

heard was the discussion about what would be considered a 

14 concentration that would provide an adequate marketing — 

15 bill, I would have loved to have heard that conversation. 

,6 (Laughter) 

I thought that was quite a slippery slogan. 

(Laughter) 

MR. JORDAN: We'll fill you in. 

20 (Laughter) 

What I'd like to summarize up, and, again, 

Dr. Silbergeld came in after we had summarized up those things 

and it will provide an opportunity for Dr. Ware to hear 

what we said about that. 

We basically summarized up the discussionby saying 

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that the Committee just didn't think that we should allow 

kids blood lead levels to reach as high as 25. And that was 

pretty clear as we talked about it. 

In fact, we found that the Committee people seemed 

j to be saying, hey, when kids' blood lead levels reach 20, 

we ought to be concerned about the thing. And so we basically concluded that we ought to be setting a standard which 

would give us a very low probability of any kid, that we can 

protect with an air standard — and I differentiate that 

from kids whose blood lead level is coming from some other 

source that's not related to the air like paint chips — but 

when you can protect, you ought to be setting a standard that 

will give you a low probability of kids from air lead reaching 

a blood lead level of 20 micrograms per cubic meter. 

On the other hand, we didn't hear much of anyone 

saying we ought to be setting up an air standard to try to 

keep kids blood lead levels below 15. So we sort of isolated 

in on that we ought to be having that range somewhere between 

15 and 20. 

DR. .WARE: You can make an argument that we ought 

"to drive*the air lead as low as we can. I mean, that would 

be one way of pulling together all the information you have 

in the criteria document, that there's really no — given the 

background levels of lead, that there's really no extra 

burden of air lead that-we can feel comfortable about. 

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1 CHAIRMAN LIPPMANN: Okay. Do you have any further 

2 advice you're seeking from us on the staff paper? If not, 

3 I think I speak for the Committee in commending you again 

for the way it has been approached and the' high level of 

5 performance shown here, not that it's perfect. And we've 

6 certainly let you know what we think about ways to improve 

7 it, 

8 But we are particularly pleased, I think, with the 

9 way in which you've laid out the thinking and shown us tne 

10 options that are available to the staff paper. We trust that 

n the criticism that we've given you has been constructive and 

will enable you to produce substantially an improved second 

13 version, 

14 -"* • I think we look forward to reading and reviewing 

15 it for you, 

M R. JORDAN: On behalf of the invisible staff, 

these young people that did the work, let me say we appreciate the Committee taking the time to share their views and 

we value those views. 

And .1 assure you that the next version of it will 

•incorporate those views. 

22 CHAIRMAN LIPPMANN: Any further last words from 

23 members of the Committee to the staff? 

24 (No response) 

Well , it's time for our first break of the day, 

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1 Let's resume at 10:10. 

2 (A brief recess was taken) 

3 CHAIRMAN LIPPMANN: Bruce, do you plan to introduce 

this topic? 

MR. JORDAN: Sure. For sometime now we have been 

6 working toward developing a risk assessment capability. I 

7 suspect that a lot of people on CASAC are getting tired of 

8 hearing us say we're doing it. 

9 It's been a long and challenging task for us. And 

10 three members of the Committee have been instrumental in ' 

n helping us with it, Dr. North, Dr. Morgan and Dr. Curran. 

And we have at least completed a portion of the risk assess13 ment thing and that's what we want to share with you. 

-We have not completed it all yet. And, as I pointed 

out, these two gentlemen, Dr. Wallsten and Dr. Whitfield, I 

believe arrived from England when — yesterday or day before 

yesterday? 

DR'. WHITFIELD: Thursday. 

MR. JORDAN: Thursday. So they got back from 

England where .they have been going some other encoding sessions with people over there. 

They're going to come and give us a presentation 

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with. It is our intention to take what they present today, 

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1 and we'll route that into the staff paper when you see it the 

2 next time. 

3 So I ask that you listen very attentively to what 

they, give and what they say so that we can get some feedback 

5 as to what the Committee members think of this approach . 

6 and the techniques that we will be presented today. 

John, do you have anything further? 

MR. HAINES: Just in the form of introduction, 

9 Drs. Wallsten and Whitfield are going to present to you the 

basic methodology we have developed for encoding procedures 

and lay that out for you and give you the results of the 

encoding sessions — as indicated, we have proceeded, on our 

encoding on IQ, and we should hope to have that finished up 

in about another month, I guess. 

We have some followup sessions with some of the 

experts that we've encoded. Then we will hopefully this summe 

have our exposure model in shape where we'll be able to 

estimate exposures. And there's risk estimates. We want to 

indicate at the end of their presentation we do give some 

risk estimates, using the HANES distribution as — for 

2i' -exposures. 

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These are hypothetical ones. But we will give the 

Committee some indication of how ultimately we will present 

24 these estimates to the Administrator, 

Are there any-other points of clarification? 

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DR. WALLSTEN: No. I think the only other thing 

to say is that I imagine we'll be back at the next meeting 

with a more full discussion. 

MR. JORDAN: If he gets in the staff paper you 

will, by gosh — 

DR. WALLSTEN: Yes. 

MR. HAINES: ARe you ready? 

8 I; DR. WALLSTEN: Yes, we're ready. Should I start? 

I tj 

0 j MR. HAINES: Yes. 

ll 

10 j PRESENTATION BY DR. RONALD G. WHITFIELD AND 

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11 ! DR. THOMAS S. WALLSTEN 

12 DR. WALLSTEN: Actually, before I do start, let 

13 jj me say that we have now just available a technical report 

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that"describes some of the pilot work we did prior to 

beginning any of the encodings and some of the considerations 

in much more detail than we're going to present here. 

They were just bound and available yesterday. So 

we have a sheet, if anybody wishes to receive copies, we'll 

circulate the sheet and Ron will send out copies from Argonne 

Okay. Well, this is the introduction to methodology 

•for a probabilistic risk assessment associated with setting r 

a standard for lead. Now, the purpose of a risk assessment 

here is to specify or to develop probabilities under possible 

alternatives next, that various fractions of the population 

at risk would suffer certain well defined health effects. 

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So if, in fact, we've had full information for a 

2 particular health effect, we might end up with an output that 

3 looks something;like the following. We would have, for 

example, four possible alternative standards. And under 

5 each standard we would have developed the probability that 

6 the percentage of the population that suffers the health 

effect is no more than X. 

So, in this hypothetical situation, under alternative Standard 1, there's a .01 probability that a percentage 

of the population suffering a health effect is less than '.5, 

one-half a percent. There is a .05 probability that the 

fraction suffering the health effect is less than 1 percent, 

and so on. 

And, presumably, this kind of output would be of 

aid to the administrator in deciding which standard might 

protect the public at an adequate margin of safety. 

17 Now, in principle, the way such an output might be 

calculated would be, on the one hand, we have information 

about the dose response relationship for the health effect. 

And this information is based on data that is fallible, of 

course. * "• 

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associated with that. 

2 Then we are able to specify — this slide might 

3 be a little misleading — not necessarily specify precisely 

the air lead distribution if a particular standard were set, 

5 but at least we could specify probabilities over what the 

6 air lead distribution would be if the standard were set which 

7 would then give us further probabilities over what the blood 

6 lead distribution would be if the standard were set at that 

value. 

And these two sets of probabilities are then combined. So for each possible standard we would end up with 

a probability distribution of the sort we just showed you. 

This is assuming that we have full information. 

14 " As everybody is well aware, we say here, "Full 

15 information is generally not available." We could say full 

information is virtually always not available. The informaticjn 

or data that one has with respect to a particular health 

effect are generally sparse, incomplete or indirect, both with 

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20 air lead to blood lead relationship. 

2i • * Now, this additional uncertainty that is due to 

22 the incomplete data or to lack of knowledge, must always 

23 be estimated and incorporated into the output. 

Now, just to make perfectly clear, there are really 

two sources of uncertainty involved and two broad classes of 

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uncertainty involved in any risk assessment. 

One is the uncertainty that's actually associated 

with data, and this is the uncertainty that most empirical 

scientists are used to, associated with sampling air with 

measurement air, and it gives rise to all these statistics 

j that we normally think about. 

I But there's also uncertainty associated with lack 

j 

' of data. It's uncertainty associated with extrapolating from 

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| animal models to the population of interest. Frequently, 

there are data from human populations but they're not neces- , 

sarily the populations that we consider to be at risk. 

So we have to extrapolate, say, from data regarding 

j exposed workers to what those response relationships might 

be iff children. These extrapolations generally aren't straight 

line extrapolations. They involve certain theories. And 

there's uncertainty associated with which theory is correct. 

And then, of course, there's lots of other uncertainty. And so it's important to conceptually distinguish 

between these two kinds of uncertainty. 

Now* the first kind of uncertainty is, as I said, 

'the sort"that's usually handled with standard statistics. 

The second kind of uncertainty is much more judgmental in nature. And what we have been doing and what other 

decision and risk analysts do is try to list uncertainty 

in terms of subjective probabilities. They are matters of 

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1 judgment as to the nature and extent of this uncertainty. 

2 And different experts might have different judgments. 

3 So we have been looking at this in a manner that 

we will show you now. This uncertainty — there may even be 

5 disagreement among experts as to what this uncertainty is. 

6 And we believe it's important to represent to the Administrator 

not only the nature of this subjective uncertainty, subjective 

8 probability, but the extent of agreement among experts. 

9 And so we are going to do this. 

Now, a possible way to modify this ideal that we 

H started up with before in light of the incomplete information, 

would be to have either a range of probabilities or a bunch 

of different probability distributions associated with each 

14 alternative standard. 

15 And what we're doing is we are incorporating the 

16 subjective probability judgments from each expert separately 

so, based on each expert's judgment, we get a different probability distribution. And this is summarized here. 

Now, awhile ago, I read the talk that was given 

by Mr. Ruckleshaus when he was the Administrator of EPA. I 

think it*was given at Princeton University and published in 

the journal "Risk Analysis" in September of '84, and there 

are a few quotations there that I wanted to read because I 

think this kind of an output really is one way to get at 

what he was requesting at that time. 

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He says, "If I'm going to propose controls that may 

have serious economic and social effects, I need to have some 

idea of how much confidence should be placed in the estimates 

of risk that prompted those controls." 

So that's one point that this kind of an output is 

trying to provide, how much confidence there should be in any 

given risk estimate. 

Further on in the same talk, he says, "Let me now 

propose some principles from more reasonable discussions 

about risk. 

"First, we must insist on risk calculations being 

expressed as distributions of estimates and not as magic 

numbers that can be manipulated without regard to what they 

"really mean. 

"We must try to display more realistic estimates 

of risk to show a range of probabilities. To help do this, 

we need new tools for quantifying, ordering sources of 

uncertainty, and for putting them in perspective. 

"Second, we must expose to public scrutiny the 

assumptions that underly our analysis in management of risk." 

So, without even knowing he had m£de the- speech, 

we're trying to do this and it came together very nicely. 

So this is an attempt to serve those goals. 

Now, the question is how would we come upon — how 

would we go about calculations that would lead to the output 

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of the sort we just showed you? 

Well, in principle, it's quite similar to what we 

had indicated before. We have a dose response relationship 

for a particular health effect. And there may be some data 

and associated statistical distributions. But there's also 

uncertainty of the other sort that we talked about, and this 

would be quantified or we will get some handle on it by 

getting subjective probability distributions from suitable 

experts, 

On the other hand, there's the air lead/blood lead 

relationship, and we also must include some subjective probability judgments to handle those uncertainties. And, again, 

those were combined and there are many more possible combinations which give rise to the range of probability distributions. 

In this talk, we're only going to- focus on the work 

we've done with the dose response relationships and, indeed, 

only a small part of that right now. So we're only going 

to talk about the upper left-hand box in this slide. 

Now, there are three health effects that the whole 

project is concerned with. One is lead induced hemoglobin 

decrement, and the other is lead induced elevated EP and, 

finally, lead induced IQ decrement. 

Regarding EP levels, there's relative complete data. 

And so it was not necessary for us to do any subjective 

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probability encoding. People felt that the data base was 

sufficiently good and we could just work with that. And we 

have done so but we will not be presenting that here. 

The data regarding lead induced hemoglobin decrement 

is much more incomplete. And it did require that encoding 

experts subjected probabilities, and we're going to present 

a summary of what we did there. 

The data on IQ can also be called incomplete, and 

most generously, I guess. And *re are currently working on 

encoding experts subjective probabilities, on that. So we 

are only talking now about the left-hand column. 

There were three basic steps that we proceeded in 

to do this encoding. We first developed a protocol for the 

"probability encoding, and I will discuss that in a bit more 

detail in a moment. OAQPS selected a set of experts who 

span a range of respective judgments. And We visited them 

and carried out the encoding. 

Now, it was necessary to have a protocol, a written 

protocol. I believe copies of that were distributed. So 

you've seen the protocol that we eventually ended up with. 

It was necessary to develop that for three primary reasons. 

First, to provide a public record of how the 

encoding was accomplished. 

Second, to provide consistent methodology from 

coding the subjective probability of all the experts. 

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Now, it was very important that if we do find 

differences in judgments among the experts, that these differences reflect differences in their actual judgments and 

not differences in the methodology, how we carried out the 

judgments. 

So this is really quite important. 

And finally, we need to ensure that the judgments 

of the various experts are comparable so that when we 

present them it's clear. 

The protocol, itself, was developed to satisfy a 

number of requirements. First, it was important that the 

adverse health effect be precisely defined. The population 

under consideration and the exposure conditions should also 

"be precisely defined so that all experts would be judging or 

predicting the same events with the same parameters. 

Again, the point is if there are differences in 

judgments, we want to make sure they are truly differences 

in judgments, not differences in the particular parameters 

that are being talked about or how the pluses should be 

conceptualized. 

• It was -important to pose questions for subjective 

probability encoding that can be thought about simply and 

responded to with a minimum of motivational and judgmental 

bias. 

In going through this exercise , one wants t o ge t 

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as precise a question as possible that can be thought about 

as precisely as possible so that there's no confusion as to 

what is being discussed. Evidence can be brought to bear in 

some way. 

Not everybody views the literature the same way. 

Not everybody extrapolates from the available literature to 

the — in question in the same way. It was necessary that 

we be able to accommodate a variety of perspectives. And, 

finally, it was necessary that we be able to work with and 

present a range of judgments. 

So our protocol was intended to serve these purposes. 

A number of people aided in the development of the 

"protocol. They are mentioned here, Dr. Anita Curran, 

Dr. Julian Chisolm, Dr. Paul Hammond, Les Grant and his 

entire staff, Paul Mushak and the OAQPS staff. We went through 

a number of iterations in developing the protocol. And 

these people were consulted at a number of points along these 

iterations. 

The way in which we developed the protocol was 

first tio become familiar with the problem since ne'ither Ron 

nor I are lead experts. And so we did this by reading the 

available draft of the criteria document. We talked with the 

OAQPS staff. 

Following that, we talked with — discussed the 

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issues with a number of the people who were mentioned in the 

last .slide on the telephone, occasionally in person. In many 

different ways, we talked with people to determine how to 

structure the problem and to learn what are their relevant 

variables. 

Then the first draft of the first draft of the 

protocol was written. It was sent to everybody. We discussed 

it with each person. We got their feedback in what was good 

and what was bad about it, how they could respond to it, 

factors we had left off, and so on. 

We revised the draft and went through that a number 

of times until finally everybody was satisfied. We wanted 

to be specific wherever possible, but we did need to accommodate different perspectives, different perspectives, say, or 

the effect of iron deficiency on these things. And different 

perspectives on the effect of age, and so on. 

So we needed to be as specific as possible with a 

lot of freedom where necessary. And we think we finally . 

achieved that until we ended up with a protocol. 

Okay Ron. 

I believe the protocol was circulated to- everybody. 

But just to summarize quickly, we had an introduction that 

described why we were doing this business. The question of 

what hemoglobin level should be considered adverse, itself, 

is not precise, and we needed to work with a precise health 

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effect so we defined two different levels and got judgments 

separately regarding hemoglobin is less-, than or equal to 

9-1/2 grams per deciliter and less than or equal to 11. 

The population at risk was defined as children 

from conception to their seventh birthday. We spent a good 

deal of time discussing the exposure conditions which should 

be thought about and assume the range of physiological and 

environmental conditions that the population should be considered to be under. 

Then we spent a good deal of time with the expert 

actually discussing the evidence, the implications of the 

evidence; how to interpret it, what it means for the children 

under consideration. And this was to serve two purposes. 

"One Was to help people bring to mind as much uncertainty as 

possible prior to beginning, because frequently people aren't 

used to thinking about the uncertainty involved in the 

evidence, only the central tendency where they think it 

points and not how much uncertainty is associated with it. 

And secondly, it was so that if we do get different 

judgments from different experts, we might have something 

in this discussion that would help us to interpret these 

differences. So we spent a good deal of time on that. 

We discussed ways to minimize motivational and 

cognant advice. These are in the judgments. I won't go 

through that here. 

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And finally, we obtain the probability judgments. 

And Ron will talk about that more specifically. 

And I think this ends my portion. I was supposed 

to tell you how we worked up to the probability encoding. 

And Ron and I will change places now, and Ron will give you 

a summary of what we actually did unless somebody wishes to 

ask me a question at this point. 

Yes? 

DR. NORTH: Could you be a little more specific 

on what you did on the bias issue? Was that a general discussion or did you take some example questions? 

DR. WALLSTEN: It was a little more than general. 

I didn't bring with me the protocol, but we have a section 

"which" summarizes the psychological research on that regarding sequential effects of the so-called anchoring adjustment, 

various" memory problems and so on. 

We went through those specific effects. So it was . 

a little more than general. 

DR. NORTH: Did you take them through a questionnaire? 

DR. WALLSTEN: No, we did not. 

DR. NORTH: Did you demonstrate any of the biases 

with them or was this just a general discussion of psychological literature that's in the area? 

DR. WALLSTEN: That's right. And we tried to focus 

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it — we focussed the discussion on the — in terms of thinking about data, per se, of the sort here. But we did not 

focus on what you're asking about. 

DR. HAMMOND: Tom, as I recall, the ground rules 

were that the decrement in hemoglobin were exclusive of those 

that might be due to iron deficiency. In other words, it 

was strictly — 

DR. WALLSTEN: That's a good point. 

DR. HAMMOND: — as a result of the lead exposure. 

DR. WALLSTEN: That's right. That's a very important point to us. We're talking about lead induced hemoglobin 

that's over and above anything else. 

DR. SILBERGELD: Were people asked to consider 

"each effect in isolation? 

DR. WALLSTEN: You mean the 9-1/2 and the 11, or 

what do you mean? 

DR.. SILBERGELD: No. The hemoglobin effects, the 

EP effects and the IQ effects. 

DR. WALLSTEN: Oh, okay. We did not discuss — 

first of all, we did not discuss the IQ effects with the 

same people with'whom we discussed the hemoglobin effects. 

DR. SILBERGELD: No. I understand that. But when 

you asked them to focus on, say, the hemoglobin effect, you 

know, it comes to mind in thinking about .is that at dose 

ranges, whether I would consider effects on hemoglobin to 

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occur.. 

Other things would come to my mind at the same 

time of what's going on — 

DR. WALLSTEN: Right. 

DR. SILBERGELD: — inside the exposed person. Did 

you ask people not to think about those other things? 

DR. WALLSTEN: No. We didn't ask them not to think 

about that. In fact, we even had some general discussion 

about it. But the only quantitative discussions that we had 

focused on the hemoglobin. We didn't discuss specifically 

other effects except insofar as they might have come up in 

the discussion of the evidence that you mentioned. 

DR. SILBERGELD: And you were asking them to con-

"sider" each effect in its own terms, not necessarily as a 

marker? 

DR. WALLSTEN: That's correct. That's correct. 

That's right. 

Now, regarding the EP, there, we only had qualitative discussions with people regarding what levels of EP might 

be thought to be adverse and for what reasons, either because 

it's an indicator' of other things in its own right', or what 

have you. 

But we didn't do any actual probability encoding 

regarding EP levels because the data were sufficiently good, 

and it wasn't necessary to do that. 

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1 MR. SILBERGELD: No. I just seems that each of 

2 these end points has a slightly different status. 

3 DR. WALLSTEN: Oh, that's right. 

DR. SILBERGELD: — in terms of what it denotes and 

connotes in terms of human physiology. 

DR. WALLSTEN: Yes. 

DR. SILBERGELD: And I don't know how you would 

8 straighten that out. 

9 DR. WALLSTEN: Well, I'm not sure that I see why it 

10 was a problem. I mean, I certainly agree with you that they 

n have different -- each has its own status. But at a given 

12 point in time, we focused only on one of them and we didn't 

13 really consider the others. 

14" "~ We were working with separate health effects but 

15 working with them separately. 

16 DR. SILBERGELD: Well, that's what I was trying 

17 to ask, how separate they were. And I'm not sure that I 

18 understand from your answer how separated they were in terms 

19 of how you instructed people. But that's — 

20 DR. WALLSTEN: Okay. Let me say just one more 

21 thing, and if we 'don't get it now we can talk about it later. 

22 But we did focus uniquely on a single health effect at a 

23 time for all the probability judgments. 

24 DR. MAHAFFEY: This may be evident through your 

25 protocol. In the reduced hemoglobin level, there's less than 

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9.5 and less than 11. And in possibly each range of interest 

there's a lot of age related change in what's considered 

normal hemoglobin. 

How did you handle this, given that you have two 

levels in here? 

DR. WALLSTEN: One of the places that we built in 

freedom for the individual expert to respond was by allowing 

the expert to divide the age population so that we worked 

separately with children from age 0 to 3 and children age 

4 through 6. 

So it was at each expert's option whether he wanted 

to — he or she wanted to consider the dose response functions 

for the single population or for the two subpopulations 

"separately. 

DR. MAHAFFEY: And they would consider both the 

decrement under 9.5 and the decrement under 11 — 

DR. WALLSTEN: That's right. 

DR. MAHAFFEY: — for one or two populations depending on their choice. 

DR. WALLSTEN: That's right. In Ron's presentation, 

that will all be made more clear. 

DR. SCHWARTZ: I was curious as to how you dealt 

with the fact that there might be multiplicative rather than 

additive effects of different things except, for example, 

some people might or might not think that the ability of lead 

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to reduce hemoglobin might be the function of your iron 

status. 

DR. WALLSTEN: That's right. 

DR. SCHWARTZ: Has a — status that's not enough 

to cause anemia but it would be closer to your — may also 

have a greater decremental response to the dose of lead 

through someone who is farther away. And therefore, it's 

difficult to separate out those two things. 

DR. WALLSTEN: Yes. That was certainly the most 

difficult issue that we had to deal with. And as a first 

cut to dealing with that issue, we gave people the option of 

dividing up into the two age groups under the assumption that 

most of the iron deficiency would be in the lower age group 

"rather than in the older age group. 

So that was the first cut in dealing with it. 

The second cut was to discuss that issue more 

specifically as to whether people thought that was an interaction or, essentially, additive effects of the two. And 

different people had different reactions to that question. 

And I won't go into detail now only to say that was, 

far and away, the' hardest part of the protocol to handle. 

Maybe I should go change the slides and let Ron 

talk. 

DR. WHITFIELD: Just't o be a littl e more specific , 

thes e were the healt h effects tha t we dealt with again. The 

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The reduced hemoglobin levels that we defined as adverse 

health effects,or potentially adverse health effects, were 

the levels 9.5 grams per•deciliter and 11 grans per decileter. 

As far as elevated EP goes, we took the levels 

that Dr. Pionelli had in his paper and worked with those. 

And those were 33 micrograms per deciliter and 53 micrograms 

per deciliter. 

What we're going to be developing for intelligence 

quotient questions are two sorts of things. One is just 

the average decrement. And the second is a little more complicated. 

We'll be talking about probabilities, changes in 

probabilities that fractions of populations will have IQs 

"below critical values of any choice — 70, 80, 90, whatever. 

And the results that I will show you are going to 

deal only with hemoglobin again and only with hemoglobin 

levels less than or equal to 11 grams per deciliter. These 

were the e experts who participated in the study. 

In New York City, we found Drs. Davidow (ph), 

Piomelli and Rosen agreeable to talking with us, Dr. Chisholm 

at Johns Hopkins,' and Dr. Hammond. Three of those' people 

are here today. 

The judgments were obtained in a four-step process. 

We began with an initial encoding session where we obtained 

the judgments for the first time. When we left, we went 

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back and worked with those judgments, doing a number of 

things, one of which was just interpreting them in words 

so that they'd be more understandable to the expert. 

Second of all was fitting functions to the judgments. And you'll see why in a minute, why we had to do 

that more clearly. 

But one of the reasons was that we obvsiouly didn't 

have the time to measure a function at very small intervals 

over response rate. We had to take a limited number of 

points and assess a probability distribution to it. 

We need to interpolate between those points, 

obviously, to carry out the risk assessment.- And rather 

than do something simple like a straight line linear interpolation, which began to make sense in many cases, we fit 

smooth functions to these judgments. 

The original judgments, along with the fitted functions , were fed back to the experts prior to the second 

encoding session. So he had time to look at things in the 

privacy of his own office and cogitate and consider what it 

was — what the implications were. 

' We came" to the second session and "discussed the 

results that we had fed back to him. And our goal was to 

obtain from him concurrence that we had indeed captured his 

best considered judgments regarding the health effect. 

(Pause) 

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A variety of encoding techniques were used to 

obtain the probability judgments. We began by obtaining a 

large plausible response rate interval over which the probability of the health effect occurring would lie in his 

judgments. 

Various methods were used to quantify judgmental 

probabilities in that interval. We initially started by 

making extensive use of the famous SRI probability whell 

that Dr. North is very familiar with. 

And depending on the range of the probabilities 

that we were trying to estimate -- sometimes they were very 

low, close to zero; or very high, close to one — we returned 

to things like odds or just straight probabilities. We used 

"interval checks to ensure the consistency of the judgments. 

In short, we used what worked best with the expert, 

himself, after awhile. At times, we turned away from exclusive use of the wheel, and we went back and forth. It was 

an adaptive process. 

As I mentioned already, functions were used to 

represent the judgments. And they were being combined with 

the blood lead distribution to obtain what we call a derived 

risk distribution. 

Dr. Mahaffey, this slide addresses the question 

you asked earlier. 

(Laughter) 

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You now see the fact that we obtained judgments 

from'four of the five experts. One of the experts, not surprisingly, was uncomfortable with the whole idea of giving 

us probability judgments. He gave us a very good discussion 

of EP but nothing quantitative about reduced hemoglobin. 

From the other four experts, we obtained a total of 

twelve sets of judgments. 

Experts D and E provided us with four sets because 

they decided to break down the H group from zero to six into 

two subpopulations. And so that times the two health effect 

levels result in four sets of judgments. 

Expert C did not feel he needed to break down the 

population into two subpopulations. And so we assessed 

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levels and for the entire population. 

Expert A gave us judgments for only the higher 

hemoglobin level, that of 11 grams per deciliter, for ages 

zero to three and four to six. But as you'll see from the 

results that follow, his judgments implied, when combined 

with a blood lead distribution, virtually no risk to children 

at the 11 grams per deciliter level. 

And it was pointless to pursue the interrogation 

on the rack any further in getting numbers that were so near 

zero. So we terminated the elicitation process with the 

single health effect. 

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These are Expert C s probability judgments, about 

the fraction of U.S. children age zero to six that would 

have lead-induced hemoglobin levels at or below 11 grams 

per deciliter at each of the indicated blood lead levels. 

What the figure shows is six sets of probability distributions . 

.We assessed each of these independently of one 

another initially. We assessed them in a random order. We 

assessed points within each distribution in a random order. 

And please don't be confused by the fact that there are six 

sets of curves on here. Let's focus on one of them right 

at the moment. 

For example, the one to the far right which corresponds to a blood lead level of 55 micrograms per deciliter, 

the curve shows, for example, that if you follow up on the 

wide axis where it says, "Probability that the response rate 

is less than or equal to a specific number," and cut across 

at the .5 probability level over to where it intersects with 

the L = 55 curve, and then following it down to the X axis to 

the response rate axis, you see that there's a median estimate 

of about'— a response rate of about 28 percent. 

This means that amongst a group of children age 

zero to six having blood leads of 55 micrograms per deciliter, 

that the response rate will be less than or equal to about 

28 percent among that group. 

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The curve has a slope to it from left to right, 

increasing from left to right, and that indicates the degree 

of uncertainty about the judgments regarding the response 

rate. 

The slope of this curve indicates, for example, 

that if we talked about what we called "a credible interval," 

or an interval that with some probability contains the true 

response rate, we can see, for example, a 25 percent or a 

50 percent credible interval which would begin at probability 

.25 on the low end and go up to a probability of .75 on the 

high end. 

It would imply a response rate interval of about 

22 percent to about 33 percent. 

MR. JORDAN: I see a lot of blank faces. 

DR. CURRAN: Yes. You lost me too. And I thought 

I knew what was going on here. 

(Laughter) 

DR. WHITFIELD: I think it would be better if I 

were able to complete the thing — 

DR. CURRAN: No, no. I don't think that's the 

problem. 

(Pause) 

DR. SILBERGELD: I don't think that's the problem. 

I mean, the figures are .exactly what's on the board, you know, 

on the slide . I don't think we're having trouble with 

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following what you're doing except conceptually. 

One problem that strikes me is that you're treating 

these as if they are stochastic probabilistic events, and 

they're not. These are dose response events, not like, say, 

the probability of a cancer which is an either/or event. 

So I'm not really certain what this means when you 

say that a person has a blood lead of 55 but there's a 

50 percent chance that 28 percent of those people will have 

hemoglobin less than eleven. Is that what this is saying? 

DR. WHITFIELD: There's a ~ 

DR. SILBERGELD: But that's turning this into a 

stochastic response. 

DR. WHITFIELD: No, it's not. 

Roger, you've got something to say? 

DR. MORGAN: It's a statement about — the expert 

does not know exactly how the one corresponds with the other. 

This is a statement of his subjective odds as to what the one 

will be, given the other. He doesn't know exactly. So he's 

being asked, given that it's 55, give me your odds on what 

the response rate will be. 

' There's nothing stochastic about it. If. you could 

run the experiment and know it, there would be a number. But 

you haven't got the precise experimental results, and this 

is a substitute for that. This is the expert's subjective 

judgment. 

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DR. SILBERGELD: Then it isn't really a response 

rate .in terms of how I, as a biologist, would think of a 

population response. 

DR. MORGAN: It is the best professional judgment 

of this expert as to what the response rate would be if you 

could run the definitive experiment and measure. 

DR. SILBERGELD: But as a biologist, I would not 

expect to see a probabilistic response rate for something 

that I think is a.continuous effect. 

DR. MORGAN: No. But this is not a statement that 

it's a probabilistic response rate. 

DR. SILBERGELD: But it seems to me that this axis 

is. 

DR. MORGAN: No, no. It is a statement about the 

expert's judgment. I'm going to leave in 7 minutes for the 

airport. And if you ask me how long it's going to take to 

get there, I can't tell you. When I'm there I'll know. 

What I could give you right now would be a probability distribution, my subjective judgmental distribution, 

on how long it's going to take me to get to National Airport. 

When I'm' there, you can actually check and see where, in that 

distribution, the answer lay. 

But these are this expert's distributions in his 

judgment about what that response rate would be if he could-, 

run this definitive experiment which, unfortunately for the 

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moment, he can't run. 

DR. SILBERGELD: Well, I guess I'm hung up on this 

phrase "response," because it invokes, in my mind, the concept of dose response. But that's not really what you're 

talking about here. Is that right? This is some psychological disciplinary meaning of the word "response"? 

MR. MORGAN: No. It's the same as "time." It 

means how long is it going to take me to get to the airport. 

It's net going to take a probability distribution in time. 

It's going to take me 23 minutes. But at the moment, I don't 

know that. 

DR. SILBERGELD: I thought he was saying that this 

would indicate tha 28 percent of the population with 55 would 

-have less than 11. And that, to me, is like a biological 

response. 

DR. SCHWARTZ: But the distribution — I know what 

he's saying — that the expert — 

(Simultaneous conversation). 

DR. SILBERGELD: I mean, maybe this isn't worthwhile 

This is an exercise in — 

' DR. SCHWARTS: He's saying that the expert — are 

no more than 25 percent. That at 55 micrograms, fewer than 

22 percent of the children would have low hemoglobin levels. 

And the expert thinks that the odds are no more than 25 percent that more than 32, or whatever the number is, percent of 

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the children would have low hemoglobin levels. 

2 And he has a range of uncertainty as to what per3 cent of the children really will have low hemoglobin levels 

but this could — he thinks there's no more than a 25 percent 

chance there will be fewer than 22 percent of the children, 

and no more than a 25 percent chance that there will be 

32 percent of the children. And the number is probably somewhere in there. 

9. And that's the probability that's being approached 

10 here. 

n DR. SILBERGELD: That's not what I'm asking, sir. 

12 DR. WALLSTEN: And I think there's — 

13 DR. SILBERGELD: I'm asking about what this response 

14 '"is . That stills sounds to m e like treating this as a sto15 chastic event. 

16 DR. WALLSTEN: If, in fact, the experiment were done 

17 we could take all those children with lead levels of 55, for 

18 example, and determine what percentage of them did, indeed, 

19 have hemoglobins less or equal to 11 percent. We could sub20 tract out the base rate percentage so we could get what per21 centage of them have lead-induced hemoglobins less than or 

22 euqal to 11 grams per deciliter. 

23 And that, of course, would be some data from the 

24 experiment. And it would be a response rate. It would be 

25 a particular number that is along the X axis. Maybe.it would 

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here, maybe it would be here. It would be a particular number. 

Now, the experiment has not been done. And so 

there's uncertainty as to what the ultimate would be. And 

this is exactly the distinction between the two kinds of 

uncertainties I was referring to earlier, the stochastic 

uncertainty versus the judgmental uncertainty. 

(Pause) 

DR. NORTH: I'm wondering if we have a semantic 

difficulty about the word "response." 

DR. WALLSTEN: Yes. 

DR. SILBERGELD: .That's what the problem is. 

DR. NOBLE: If we were saying a fraction of the 

"population with this effect, would that be clearer? 

DR. SILBERGELD: No, because I think there really is 

a fundamental — I'll just say it one more time and quit 

because this is far beyond what I — this whole exercise. 

It seems to me there is a fundamental difference 

between effects which occur with a probabilistic distribution, 

leaving aside all these words like cancer which I — doesn't 

occur. ' ' " • 

And then there are effects which are gradated (ph) 

and continuous. And those have a very different fundamental 

biological distribution. And this seems to be turning a 

continuous effect into a probabilistic distribution if I 

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(Chorus .of no, noes) 

DR. SILBERGELD: Okay. I'll retreat and think about 

this some more. 

DR. MORGAN: Try relating in the horizontal axis 

percent with lead induced hemoglobin less than or equal to 

11 grams per deciliter. 

DR. WALLSTEN: See, if the experiment were done 

this would be — at street value, there would be some percent with hemoglobin less than 11. 

DR. SILBERGELD: That's right. 

DR. WALLSTEN: There would be some percent. What 

that percent is is uncertain. Different experts have dif-

|~ferent degrees of uncertainty. And so this represents the 

uncertainty associated with one particular expert's judgments. 

I think we can pursue this more later unless other 

people — 

DR. NOBLE: Okay. I think another thing that may 

help is we've made a rather arbitrary distinction of low hemoglobin as being less than 11. And then that's being asked 

again as'less tha'n 9-1/2. So whereas it's a continuous 

response, we've drawn a line and said above the line we're 

going to count the effect — or, rather, below the line we're 

going to count the effect, and above the line we're going to 

say the effect is not present. 

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And to the degree that we'reused to thinking about 

it as what's the range of hemoglobin in the population, this 

may make it difficult. 

DR. SILBERGELD: Well, so it is being turned into 

a stochastic event. It's either occurring or it isn't. 

DR. MORGAN: It's above or below 11. 

DR. SILBERGELD; Yes. And that is making it 

stochastic. 

DR. WARE: We are turning it into a discreet event, 

you're right about that. 

DR. LARSON: Well, it's discreet in the sense that 

you can — 

(Simultaneous conversation) 

DR. WARE: They're taking a continuous phenomenon 

and translating it into a discreet. It's like taking a 

blood pressure measurement and translating it into is the 

individual hypertensive or not. 

DR. SILBERGELD: Right. 

DR. WARE: I wouldn't call that stochastic. I would 

say they're translating it into a yes or no phenomena. 

• CHAIRMAN LIPPMANN: We had better-move on if we're 

going to continue to finish this. 

DR. WHITFIELD: Oky. Now if we look at the set of 

six curves, you can see that it was hard work for us to 

obtain this. But the curves do not overlap. The curves 

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indicate that with the increasing blood leads there is now 

increased probability of higher response rates or fraction 

of children having hemoglobins below the prescribed level. 

These are all desirable properties. 

(Pause) 

And as I've said before, we fit functionsl representations of his judgments. We showed these representations 

to the experts, there are 12 sets of graphs that look like 

this, and these are the things that we finally obtained his 

sign-off line with, if you will, his agreement that we had 

captured his best judgments. 

When functions like those shown in the previous 

slide were combined with a blood lead distribution, and the 

"blood" lead distribution that we used for illustrative purposes 

was the NHANES II blood lead distribution, we were able to 

calculate what we call a derived risk distribution. 

This is a probability distribution over response 

rate for a fraction of the population that would have hemoglobins less than or equal to 11 grams per decibel in this 

case. 

* And you read this curve, this single curve, much 

in the same fashion as you would read any of the curves we 

showed previously, the family of curves. 

This curve, again, shows, for example, that there's 

a .5 probability reading from the Y axis that about 10 percent 

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or less of the population will experience the adverse health 

effect as we defined it. 

And we can talk about credible intervals around [ 

that estimate, 50 percent credible intervals which would • 

correspond to probabilities of .25 on the low end and .75 

on the high end for 9 0 percent credible intervals, or 99 per—• 

cent credible interval?, or whatever. 

DR. FRANK: Excuse me. I'm just interested in the 

methodology here. 

To go back to the series of graphs about which 

Dr. Silbergeld was first asking questions, I think you concluded these are all graphs that were, in a sense, provided 

judgmentally by expert C. 

DR. WHITFIELD: That's correct. 

DR. FRANK: And you noted that there was no overlap, 

or anything like that. 

DR. WHITFIELD: That's correct. 

DR. FRANK: Which, you know, I expect that is not 

surprising to you. And — 

DR. WHITFIELD: If we were to obtain that. 

' DR. FRANK: Okay, let me ask you,'what was the 

sequence in which the expert provided these judgments? Did 

you first start with a given, that is, a blood level of 55? 

DR. WHITFIELD: We randomized the order in which 

we assessed these curves. 

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DR. FRANK: Was the expert — in a sense, did he or 

she have in front of them the previous answers given or was 

there some attempt to do these independently? 

DR. WHITFIELD: There was some attempt to do these 

independently. But, of course, the expert's making his own 

notes and, sure, we were not taking things away from him. 

And we did — you know, there were over — 

(Simultaneous conversation) 

DR. FRANK: -- on my own responses and have them 

down there. 

(Laughter) 

You know, attempted to avoid, in a sense, some 

inconsistent responses. 

DR. WHITFIELD: Right. And if this were an experimental problem where we were trying to determine how often 

that occurred, we would have stopped at that point. But it 

was not. Our intention here was to get the best considered 

judgments of the expert. 

And so we resolved the inconsistencies, like those 

that I've alluded to. The expert was able — was allowed, 

if you will, to take a systems view of the whole thing, and 

step back and look at the entire picture and make comments 

like, "Well, that doesn't make sense," and move things around, 

if you will. 

DR. NOBLE: And this may have been implicit or 

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explicit in some of the earlier discussions. But confronted, 

myself, with an exercise like this, I think I'd feel a little 

uncomfortable at first because it's something I'm not used 

to doing. 

DR. WHITFIELD: I think that was a common feeling. 

DR. NOBLE: And I wondered do they have practice 

sessions or, you know, do they try this more than once? 

DR. WHITFIELD: Well, we did do it twice. We had 

two face-to-face encoding sessions with them. 

DR. NOBLE: Is this the result of the second — 

DR. WHITFIELD: That's the result of the second. 

These are the final'judgments. 

MR. JORDAN: Ron, I think the question he's getting 

'to is'at the second encoding sessions, you did, in fact, 

show him the results of the first encoding session. 

DR. WHITFIELD: That's correct. We showed him the 

results of the first encoded session which he also — he saw 

curves like those that are shown right now which are not 

really curves. They're just assessed pooints joined by 

straight lines so that the points don't get messed up. 

' He saw that before we left. And then we fit 

functions to them after we left and fed those back to him 

like those. And it was those that we worked with hard the 

second time around. And if any revisions were needed, we 

turned back to the encoding steps once again. 

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i In some cases, that was necessary and we did it. 

2 DR. WARE: Just to get a little clarification about 

3 the details, so you selected a dose at random, and then you 

selected a probability, a subjective probability, at random? 

DR. WHITFIELD: What we did, after initially determining a broad — 

7 DR. WARE: Why don't you actually go through the 

8 process and say exactly what you chose and what question you 

9 asked the expert just so — 

10 DR. MORGAN: Would you mind if he finished? Because 

n I have to leave in an instant and I would like to hear the 

12 the rest. 

13 DR. WARE: Okay. 

14 ~ DR. MORGAN: I'm very sorry. 

15 DR. WHITFIELD: All right. What I've shown you 

16 is , so far, the results for Expert C. The whole process was 

17 repeated for each of the other responding experts. And the 

18 summary of those results, that is , the derived risk distribu19 tion, is shown on this slide. 

20 Now you can see the effect of Expert A's judgments 

21 where he'has told us that lead-induced hemoglobin effects 

22 do not begin to come into play until much higher blood leads, 

23 I believe it was around 4 5 micrograms per deciliter. 

24 And with that information, when those judgments 

25 are combined with the blood lead distribution, the result is 

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1 essentially no lead-induced — essentially no risk of a lead2 induced health effect at the 11 grams per decible curve per 

3 deciliter level among children aged 0 to 6. 

The results for Experts C, D and E are much closer 

5 to one another. I don't want to use the word "agreement." 

6 But there is this clustering that's obvious from this figure. 

7 (Pause) 

6 What the EPA, of course, is interested in from a 

9 regulatory perspective is the probabilities that selected 

10 percentages of U.S. children in the population of interest 

n will have hemoglobins at or below the defined level. 

12 And we are able to determine, from figures like 

13 those shown previously, probabilities that we have summarized 

14 ""here." If it were, for example, important to protect 99.5 

15 percent of the population, then we would want a response rate 

16 to be .5 percent. 

17 And based on the judgments of the four experts, 

18 we see that the probability is 1 in the case of Expert A 

19 that the response rate would be at or below this level. The 

20 other experts say that there's no probability that the 

21 response' rate will be less than or equal to* 1/2 of- a percent 

22 It's not until we get up around a response rate 

23 of around 10 percent where we begin to see probabilities 

24 other than zero coming into play for Experts C, D and E 

25 Let me point out, based on the judgments of Expert D 

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for example, there's a .98 for almost a certain probability 

that the response rate will be less than 10 percent. 

(Pause) 

My final slide is simply a statement of where we 

are, and that is that we are nearing completion. I've shown 

you the risk estimates for the hemoglobin levels being less 

than or equal to 11 grams per deciliter. I have not shown 

you the results for 9-1/2 grams per deciliter, but they have 

been estimated. 

And to do those, we, of course, needed to use a 

a blood lead distribution, and that was the NHANES II data. 

The second point is that we have also estimated 

the risks of elevated EP levels, again using the NHANES data. 

"IQ encodings are nearly complete. We have six experts participating, three in the United States and three in Europe. 

We have completed the first round of encodings with 

the U.S. experts. And just last Thursday, as was mentioned, 

Tom and I returned from Europe with the results of the three 

experts over there. 

We completed — while our method of operation for 

hemoglobin and fdr the American IQ experts is one -of having 

the two encoding sessions separated by, at times, one or two 

months, they were separated by a .day over in Europe for reasons of saving a lot of money. 

The exposure model encodings are currently underway, 

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And when they are complete and they are factored into an 

exposure model, and we are able to estimate or predict blood 

lead distributions based on that model, we will again be 

combining the health effects model here with the exposure 

model to form further risk estimates to these children. 

Are there any questions? 

CHAIRMAN LIPPMANN: Jim, do you want to ask a question? 

MR. WARE: Well, I did. I thought it might be 

helpful to just simply give the specific example of how you 

began the encoding session and what, having chosen a dose at 

random, was your next selection and then what did you ask the 

experts. 

DR. WHITFIELD: Okay. To simplify, exactly what 

we did was the following. We had our broad range over which 

the expert felt the true value might lie. And we were very — 

we intentionally got them to think about extremes, trying 

to overcome any central bias tendencies that he might have, 

you know, having a fixed number in mind that he thought . 

was most likely, to try to get him away from that mode.'of 

thinking' and thinking about rare events. 

We then broke that interval up into six sub-interval 

And, for example, if it were a response rate of 10 to 60 percent, we would break it up into 10, 20, 30, 40, 50, 60s. And 

then we, at random, chose one of those response rate levels 

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and attempted to determine the probability that the response 

rate would, indeed, be less than or equal to that level. 

And we hopped around the response rate interval 

at random, and we simply used a deck of cards to do that and 

proceeded. 

DR. WARE: So that was all for a given dose. 

DR. WHITFIELD: That was for a given dose. 

DR. WARE: You said what do you think is the range 

of possible response rates that could be conceivable? 

DR. WHITFIELD: That's correct. 

DR. WARE: And a person might say, well, I think 

it could be somewhere between 10 and 40. Then you would say, 

well, let's consider -- I see. Now, so then you tried to get 

"a probability assigned to each, one of the six response rates 

that are in your set. 

And then what did you do about the fact thatyou 

had reversals, and so on, at that point? 

DR. WHITFIELD: Reversals? 

DR. WARE: Yes. I mean, could it happen that there 

would be — that you ensure that the probabilities were consistent?" 

DR. WHITFIELD: Oh., yes. After getting these 

responses over the entire range, we would then plot the 

results on a graph. And then we would look at the implications of those responses. And if, for example, we had a 

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situation where the graph would go up and then come down, 

which is not a viable probability distribution, we would 

discuss it. Something had to be changed. What did you want 

to change? What did he consider when he made the first 

response versus the second response? 

How did he want to resolve it. 

DR. FRANK: And my question is what was the lowest 

probability you asked the question of? 

DR. WHITFIELD: I think, well, since we were going 

in the reverse direction, we were talking about response 

rates and probabilities that would be less than or equal to 

that response rate, we got, sometimes, very low probabilities 

like .001 or .0001. 

One chance in a thousand, one chance in ten thousand 

DR. WARE: You mean to say how likely, given that 

exposure of 55 micrograms per deciliter, do you think it is' 

that the response rate would be below 5 percent? 

DR. WHITFIELD: That's correct. 

DR. WARE: And a person might say, "I think that's 

almost certainly not going to happen. It's only .001. I'm 

almost certain it's above that." 

DR. WHITFIELD: That's correct. 

(Pause) 

DR. NOBLE: I think it would be useful if we could 

hear from the three experts in the room whose judgments were 

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were assessed with this process with regard to how they feel 

about it. In particular, their impression of how clearly 

the questions were posed. 

Were they, in fact, the right questions, well 

defined, easily understood? And, at the conclusion of the 

process, how do you feel about this as a summary of your judg-

| ment to be communicated to others in the EPA process? 

CHAIRMAN LIPPMANN: Any volunteers? 

(Laughter) 

DR. HAMMOND: Well, I must begin by admitting that 

I had a difficult time the first time around grasping precisely what each question required of me. And then I had to, 

in fact, repeat to myself precisely what was stated. 

And further, in the initial process, they used a 

wheel, a probability wheel. And would ask me, "Is the probability less than or greater than the probability that the 

color on the wheel will be more or less than what you see 

here?" 

And I never did feel comfortable with that thing 

and I basically rejected it the second time around. 

• Apart from that, I think that an adequate amount of 

time certainly was spent in exploring some of the restrictions 

that might bear on the judgments to be made. That was fine. 

I didn't have any problems with that. 

I think, too, that — I'm not sure if it was clearly 

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stated — whenever there were overlaps in the response rate, 

that .would be pointed out. I'd say, "Do you really mean 

that?" You know. And I'd say, "My god, no. I don't mean 

that." 

(Laughter) 

I guess basically that's my recollection of my 

response to the process. 

question, 

DR. WALLSTEN: Let's see if I can answer one more 

DR. NOBLE: How do you feel about the results of it? 

DR. WALLSTEN: Yes. That's what I was going to ask 

DR. HAMMOND: Well, I'd still like to see a dose 

respone curve. And, in fact, you can — for the 50 percent 

probability or confidence level or the 100 percent confidence 

level, and I think that would>be a nice thing for you fellows 

to draw. 

And each person would have a family of dose response 

curves reflecting the levels — 

DR. WALLSTEN: We do have those — 

(Simultaneous conversation) 

' DR. HAMMOND: The blood lead — 

presented. 

DR. WALLSTEN: We do have those and they've been 

DR. HAMMOND: — on the — whether on the abscissa (ph) 

and percent population on the — would be a nice display, I 

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think, of the result in terms that people understand or are 

more,comfortable with. 

DR. WALLSTEN: But when we finally showed you the 

final set of judgments, did you feel comfortable that they 

reflected your thinking? 

DR. HAMMOND: Yes. I felt it was as reasonable 

as possible given the absence of any hard data. 

DR. NOBLE: But you'd like to see a dose response 

display of your judgments to help you in ensuring that, in 

fact, that's what you meant? 

DR. HAMMOND: Exactly. I still would like to see 

the dose response in the conventional sense. But it would 

have to be a family. Right? 

DR. NOBLE: Yes. 

DR. WALLSTEN: That's no problem. 

DR. WHITFIELD: As much as I've tried to eliminate 

all of the details of identity, and everything, in my mind, 

I do recall I think we did draw such a graph with you. 

DR. HAMMOND: I didn't hear you. 

DR. WHITFIELD: I think we did draw such a graph 

in the room with 'you. 

DR. HAMMOND: You did? Yes. That may be. I don't 

recall. 

MR. JORDAN: I think what you're saying is in the 

final report, you'd like to see that. 

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MR. HAMMOND: Yes. 

MR. JORDAN: And we do plan to have that. 

CHAIRMAN LIPPMANN: Dr. Chisolm? 

DR. CHISOLM: Well, I recall, in addition to what 

he said about the wheel — it took a bit of time to learn the 

wheel; I'd never seen wheels before -- but we had a very 

long discussion as to the ground rules, what are we to considejr 

Are we to consider this purely as a lead effect? 

Are we to take the population as it is? What are we going 

to do about children that, say, have sickle cell disease'where 

their anemia, has got nothing whatsoever to do with .lead and 

other types of anemia? 

Are we to disregard that? And we had a long dis-

"cussion about what we should consider which I think made it 

a little bit difficult. 

CHAIRMAN LIPPMANN: Well, the second question is are 

you comfortable with the final expression of your judgments? 

DR. CHISOLM: Yes, given what I accepted as a ground 

rule, and that is a purely lead-induced effect. 

DR. LARSEN: Were you ever asked what the probability 

was that' the question was correct? 

(Laughter) 

DR. CHISOLM: It was a little fuzzy as to what the 

ground rules would be. 

CHAIRMAN LIPPMANN: Dr. Rosen? 

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DR. ROSEN: Well, like Dr. Chisolm, we spent a good 

deal of time figuring out ground rules. And I think it took. 

me a good deal of time to feel — knowing what the ground 

• rules were. And I also, like Dr. Hammond, had a great deal 

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; of difficulty with the wheel. 

I So that the way we wound up doing it was actually 

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In general, I was very surprised that it was relatively, I v.'ouldn't say easy -- but with a great deal of time 

and concentration, that I tended to have a good deal of confidence in the judgments that I made. And I think that confidence was further enhanced by the fact that at least three 

of us" really concurred in general, given so many unknown 

factors. 

CHAIRMAN LIPPMANN: I would like,,for my own 

curiosity, to know how'those response that you got compared 

with the ..responses of two "EPA experts" as reported in your 

September 24th, '84 report that we had in advance. 

DR. .WHITFIELD: I don't think that's fair. Do you? 

(Laughter) 

MR. WALLSTEN: No. But I think we have an even 

better answer than that, and that is that we didn't look at 

it. 

(Laughter) 

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Because, exactly for that reason, that we did — 

the pilot subjects who helped us to get this procedure set 

up were not experts in the same sense that the other people 

were. And we never felt that we should take their judgments 

with the same degree of seriousness. 

So, in fact, we didn't look at that. 

CHAIRMAN LIPPMANN: In terms of judging what to do 

with this now, we have a small sample size. In fact, we have 

the odd situation where you started with five. You've got 

one that couldn't participate, for whatever reason. You've 

got one who gave you no useful data unless the other three are 

wildly off and he's right. 

MR. WALLSTEN: Well, I wouldn't say it's not useful. 

u j I mean, those are his judgments. And I don't think we should 

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CHAIRMAN LIPPMAN: Yes, well, okay. I'm wondering 

what anybody can do with this exercise from this point on. 

And when you're dealing with such a small sample size, as we 

do with many other aspects of the criteria document, the 

data base, we .look at all relevant information. 

* Now, when you say in he^re that you looked at two 

people very knowedgeable in lead, I'm not saying they have to 

give an equal weight. But in order to judge this, I'd like 

to have as much information as possible. And I don't think 

it's unfair how two other people, familiar with the lead issue 

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how their results compared with these three or four, depending on how you look at it, from your full set. 

DR. WALLSTEN: Well, I think if it were the consensus that we should include them then we could easily. Our 

feeling up to this point was that it wasn't quite right. 

CHAIRMAN LIPPMANN: Well, I don't think you should 

have up to this point. 

DR. WALLSTEN: Yes. 

I CHAIRMAN LIPPMANN: I would have assumed that you 

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i had that on the tips of your fingers. 

DR. WALLSTEN: .No, we didn't. 

CHAIRMAN LIPPMANN: Maybe I was wrong in assuming 

that you would know that without having put it into the formal 

exercise. 

DR. WALLSTEN: I mean, I can take — I mean, we 

could actually look. We have it all here. But my guess is 

there would be one of these people who would fit very much 

in with the other three, and one whose curves would be far 

to the right. 

VOIQE: Far to the right. The opposite of "A"? 

* DR. WALLSTEN: The opposite of "A". Yes. 

DR. WHITFIELD: In fact, on page 23 of the report, 

we have summarized the results for subject 1 and subject 2. 

And, by no means — let me put the following caveat here. 

We didn't spend as much-time in the pilot subject mode with 

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each person as we did with the real thing. 

But, for example, as a result of all the caveats 

leading up to the diverse distributions that we showed you, 

and applied to the results of subjects 1 and 3, we see that 

5 subject 1 has a median response rate of around 10 percent, 

and subject 2 is about 20 percent. 

And we had showed about 7 to 9 percent, I suppose. 

| So one of the two could be added in with the group of three. 

And then the pilot subject 2 would be — 

CHAIRMAN LIPPMANN: That's what they looked like. 

| 

l 

j But further examination, I find it interesting that the case --

I and I just wonder what we do, what EPA does with it in terms 

i 

| of the variation and the experts' judgments as to using this 

and coming up with advice in a standard. 

DR. HUMPHREYS: We did arrive at a sort of consensus 

yesterday afternoon that was summarized for us this morning. 

But we did it much less systematically and there were differences of opinion expressed yesterday afternoon about what 

went into that final consensus. 

I think what this does is to make quite clear what 

the differences of opinion are,.the different variables in 

this case. 

CHAIRMAN LIPPMANN: Maybe staff can tell us. You 

indicated earlier that you hoped to bring this exercise into 

the next draft of the staff paper. And maybe you can indicate 

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how you think you could do that. 

2 MR. JORDAN: Well, personally, my view is that what 

3 we're trying to do is capture, in an informal, systemized 

sense, is what the respective experts feel about in the area 

5 of uncertain data. And we think it's a major step just to 

6 formally present these different views so the Administrator 

7 can see that there are different judgments about there about 

8 this uncertain data. 

9 And that's better than having us take this area 

10 of uncertainty and arrive at a staff valuation, and our 

n judgments. Or, alternatively, have these randomly commented 

12 -in the form of a consensus which I think Dr. Humphreys is 

3 ' trying to suggest, a formalized approach that allows you 

14 j to capture these differences of judgments. 

15 CHAIRMAN LIPPMANN: Dr. Silbergeld? 

16 DR. SILBERGELD: Well, I guess I would have to 

express some reservations if this is going to be the formal 

way in which you're going to seek to represent a specter 

of expert opinion for the Agency in terms of reaching deci17 

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sions 

I have grave reservations about about it. I think 

from listening just to Paul describing how, in a sense, his 

23 opinions were forced into nonoverlapping judgment curves, 

while that has a certain beauty to it statistically and 

methodilogically, I'm not sure that that is an accurate 

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1 representation of the way in which people discuss and reach 

2 consensus on issues where there is division and uncertainty. 

3 And I guess I'm a little bit concerned that you'd 

I don't know, since I've come into it at this point, whether 

this has become a CASAC procedure or whether this is an 

6 experiment 

7 I'm also struck that it looks like three out of 

8 a total of what, seven people seem to have come someplace 

9 or four out of seven if you count the EPA pilot project 

10 people — it doesn't seem terrifically well validated yet 

11 DR. WALLSTEN: Well, I'd like to respond to — well, 

12 unless you want to respond, Paul. I was going to respond 

13 to the word "forced." 

14 "" That is to say, I don't think "forced" is the right 

15 term. When we obtain judgments, and if there were sets of 

16 judgments that uncertain logical grounds appeared to be 

17 mutually inconsistent, then this was pointed out. And it 

18 wasn't a matter of forcing. 

It was matter of pointing out the implication of 

these judgments and having the person decide for himself 

-how he wa*nted to handle it. 

Now, I don't think it's the same thing as saying 

"force." It's simply showing the implications of judgments 

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25 I think there's a lo t of differenc e between tha t and "forced. " 

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Now, as I pointed out earlier, there are two kinds 

2 of uncertainty that one must work with. There's one kind of 

3 uncertainty that's grounded in data and the other kind of 

uncertainty that's grounded in lack of knowledge. And this 

5 is an intent to work with the second type of uncertainty. 

6 It's a very different ballgame than working the 

7 first type. That, kind of uncertainty due to lack of knowledge 

8 is always present. And the question is what is the way that 

9 this kind of uncertainty can be made most apparent and the 

range of agreement on the level of that uncertainty can be 

made apparent. 

So that's useful information. 

13 DR. SILBERGELD: Has this become the methodology? 

14 " CHAIRMAN LIPPMANN: As far as it's CASAC's role, 

15 CASAC has been asked to review the science behind this 

developing approach of OHUPS to risk assessment. 

We have agreed, in the past, to look at it and 

listen to it, and offer our judgment. Insofar as, I think, 

19 the understanding goes, we had about a year ago a meeting 

20 of a subcommitptee of CASAC which provided some input into 

the developing process at a much earlier stage. 

And several members, as individuals, have been 

called upon by EPA to help them to design stages. I don't 

24 know what else to say. 

25 Anita ? 

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DR. CURRAN: Well, the pages aren't numbered. But 

in this, and if you read the protocol, it indicated that one 

of the things they attempted to do was to select a set of 

experts who span a range of respective judgments. 

And I think, in essence, that's what they've done. 

And I think that the fact that they don't all agree is evidence of the fact that they tried to select a range. And 

I think, from that point of view in that it very explicitly 

indicates to people who are concerned about this what the 

range is, it's just an additional tool — 

MR. HAINES: Exactly. 

DR. CURRAN: — to add to and not a substitute for. 

And I don't think it was ever intended to be. 

MR. HAINES: No. This is not a decision role. 

It's a decision tool. 

DR. CURRAN: A tool. Right. You take your criteria 

document with all its uncertainties, and then you take your 

range of experts. And I think it just is an added tool to 

assist the decisionmaker who, in this case, is the 

Administrator.. 

* DR. NOBLE: I'd like to amplify that same point. 

It seems to me that it would be very useful to add in the 

presentation of this material a summary of the scientific 

reasoning from the experts. In other words, the output is 

not just the numbers as.shown in those tables, but a summary 

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1 of the judgment of Expert C, plus, perhaps, D and E if, in 

2 fact, they're close enough together so that's judged to be 

3 a consensus. 

How did their reason about the process compare to 

5 Expert A cr Expert 1 and 2 in the pilot far -to the right. 

6 It may be that there are three very different views on the 

7 science of this problem that led to the differences in the 

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numoers. 

And it seems to me it's really critical that that 

be set forth in terms of the scientific judgments, not 

simply built into the numbers. 

2 MR. HAINES: That's part of our overall presenta3 tion. Ron is starting to develop those. Once he has the 

14 write-up we will feed those back to the experts so they can 

15 review their narrative, the narrative summation, and us a 

16 feedback so we make sure we get agreement on their curves. 

17 And then we get agreement that we're fairly representing the narrative write-up in sessions. 

DR. NOBLE: I have three other comments that 

Dr. Morgan gave me just as he had to leave for the plane 

.with which I thoroughly concur. 

One is enthusiasm for this process. Dr. Curran, 

23 Dr. Morgan and I have been involved for seven years in the 

evolution of these methods. And I think that at least the 

two of us feel very encouraged with this demonstration of 

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them, of the care with which this exercise has been conducted, 

and the possibilities of it as a way of enhancing the communication on an extremely difficult, controversial and 

subtle set of issues. 

The second comment is that, really, a lot of work 

needs to be done on packaging, explaining it. This is 

extremely difficult material, especially for people who are 

unfamiliar with the concepts and the terminology being used. 

And whereas I feel you've done a very good job 

in presenting it to somebody like me at a meeting such as' 

the Society for Risk Analysis, or something of the sort, I'm 

not sure it's coming across clearly to the people that don't 

have a lot of background in this area. 

'And I think you really need to invest some time and 

effort in thinking through how do you present it very clearly 

to the kind of audience that you're going to need to present 

it to. 

The third point I'd like to make is the care that 

you're going to need in carrying this exercise further as 

we go toward the meeting next fall, especially in dealing 

-with the 'issues on the exposure side. 

I would hope that you are able to do as careful and 

as detailed a job on those uncertainties as you have done in 

dealing with some of the uncertainties in the dose response 

health effects area. 

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CHAIRMAN LIPPMANN: Can you indicate to us what 

thinking you have on exposure encoding? I'm not sure I 

understand what you're planning to do. 

MR. HAINES: Well, as we were discussing yesterday 

on the uncertainties is how much dust a child ingests. It's 

a very important parameter. Can we use subjective encoding 

to people knowledgeable or familiar with working with children and get better judgments than what appears to be a 

single data reference that we have and see if we can get --

CHAIRMAN LIPPMANN: I don't think you can have 

subjective judgments about the mass of dust that somebody 

ingests. 

MR. HAINES: I think you can take the process of 

"this "behavior, how often does a child typically at play, a 

normal child, and the dust in the environment. What kind of 

activity does he have? What's the frequency of doing this? 

And then range and judgment of how much dust we feel a child 

can get on his hands and put in his mouth. 

Granted, it's uncertain. But we're faced here with 

one very uncertain estimate. And what we're trying to do 

is get judgments that will give us a distribution of probabilities on important variables. 

DR. NOBLE: I think it would be much easier and 

more direct to do experimental work on that with children in 

controlled play situations and you'll find out. I can't 

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imagine how judgments can lead to milligrams or gram estimates 

of ingestion. 

MR. HAINES: We can't argue that it would be ideal 

to do controlled experiments on them. Then we get into 

are controlled situations typical. This is not to replace the 

data — you know, -we have the data. We want to use this. 

And we want to encourage the development of good data. 

And it's the absence of it — 

DR. NOBLE: Rather, if you can find the data, go 

get the data rather than depending on the encoding of subjective judgment. 

MR. HAINES: Exactly. 

DR. NOBLE: And this may be an area where, in fact, 

"one can go get reasonably good data. But if you can't, it 

seems to me you don't want to do an analysis where you've 

done a very careful job of assessing subjective judgment 

on health effects, but the analysis hinges on one number 

pegged to one data point in a critical issue on the exposure 

side. 

And the same kinds of care hasn't been exercised 

to ensure that the best information and judgment is brought 

to bear on that issue as well. The analysis ought to be 

balanced. And perhaps an exploration of alternatives through 

sensitivity analysis might be a good way of ensuring that, 

in fact, the analysis is balanced. 

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CHAIRMAN LIPPMANN: Tim? 

DR. LARSON: I was going to say that if we, the 

Committee, could emphasize that this is an uncertai-n area 

and that it needs to be researched, then perhaps measurements 

could be taken by EPA. If it comes down to that. I mean, I 

think that's a step forward. 

And it's, to my mind, more comfortable with that 

kind of a suggestion than rather, say, asking people expert 

in whatever you would — however you would classify that 

expert, in dust ingestion. 

(Laughter) 

As to what the numbers are.. I mean, I think that's 

sort of carrying it to the extreme. 

"" " "" CHAIRMAN LIPPMANN: I don't feel that you haven't 

done very useful things on this particular thing. And, 

clearly, it's been going on for many years. And, clearly, 

it costs a lot of money. And the implication I gather is 

that you feel that getting direct measurements would be too 

costly. 

I can't believe it. 

' MR. HAINES: No. We're not inferring —w e don't 

want to infer that this replaces it. We're saying at this 

point in time we don't have correct measurements. I mean, 

we could say, go out and conduct a study or not. 

CHAIRMAN LIPPMANN: Everybody wants to speak here. 

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DR. CURRAN: Having been - - could I just fo r one 

second? 

Having been involved in this from the very beginning 

as chairman of the initial Risk Assessment Subcommittee, one 

of the things that we laid down as a ground rule, and one of 

the concerns I heard raised over here and it hasn't been 

expressed here today, I think it should be very clearly stated^ 

that at every single meeting, and in every single paper that 

we drew up, we indicated that this methodology is in no way 

to be considered a substitute for the science, and in no way 

is to be considered a substitute for research. 

It is simply an added tool that is being presented 

until such time as the science of the research is available. 

"And I"think that was the concern that was raised over here. 

And I think you ought to very clearly indicate to these people 

here that in no way do you intend this to be a substitute 

for whatever research needs to be done or the science. 

MR. HAINES: 

DR. CURRAN: 

MR. HAINES: 

DR. CURRAN: 

No. We agreed wholeheartedly to that. 

But it hasn't been stated. 

Okay. 

And I think it should be. 

CHAIRMAN LIPPMAN: Julian? 

DR. CHISOLM: The frequency of hand to mouth activity 

24 jj under various circumstances has been done. And the behavioral 

25 . psychologists are great on counting behaviors. And they do 

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that sort of thing. 

CHAIRMAN LIPPMANN: But you have to convert that 

to a mass. 

DR. CHISOLM: Well, I don't — they probably could 

have but they weren't interested in that. 

MR. JORDAN: Let me just amplify what Dr. Curran 

was saying. 

We are in a decisionmaking mode based on the existing staLe of knowledge. And all this tool is doing is trying 

to say this is the existing state of knowledge that's out 

there, and this is how people interpret that knowledge. And 

that's simple is what it boils down to. 

It doesn't preclude or even begin to substitute 

"for doing good research. In fact, if done right, it should 

identify much better where the areas of research need to be 

focused on. 

CHAIRMAN LIPPMANN: Jim? 

DR. FRANK: Well, just a minor point of information. 

In the final report, would you include some sort of commentary 

which you may have taken from the transcript or you may have 

solicited independently from the experts, because I come 

back to what is to me sort of a range of responses among 

experts as to the ease or comfort, or, perhaps, discomfort, 

more accurately, that they feel when they have to deal with 

an odd way of expressing their expertness. 

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And it would help me very much if I could get some 

measure of what that expert felt as they were responding 

to your questions. You know, would you include this, some 

excerpt or some comment by each individual? 

DR. WALLSTEN: Yes. We do intend to include some 

summary of how each expert views the literature. I assume 

that's what you're talking about, not a measure of the — 

DR. FRANK: Not only how they view the literature. 

I think they might nave 'had a difficulty with that. But I 

think how they used their knowledge of the literature to 

answer your format of questions. 

DR. WALLSTEN: Well, as much as possible, we did 

have a very extensive discussion with each person beforehand 

-about"the literature and his interpretation. And we will 

provide a summary of that too. 

If you're referring to, somehow, how the expert — 

DR. FRANK: I noticed that Paul's feeling towards 

this evolved somewhat. 

MR. HAINES: Yes. 

DR. FRANK: Is it all right to say it improved? 

And that's fine if at the end they felt comfortable — 

DR. WALLSTEN: I see. Okay. 

DR. FRANK: — with this sort of thing. But if 

there was a degree of discomfort, that they were called in 

as experts and they were going to do their duty, I'd sort of 

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like to know that. 

DR. WALLSTEN: Okay. That's a good point. I didn't 

pick up on the perspective you were providing. 

Well, I think that what Paul described was very 

common, and it would be worthwhile to point that out. There 

wasn't very much different from one person to the next in 

terms of the initial discomfort and I think final — I don't 

know the best way to put this — but ultimately feeling more 

comfortable about it, I think that was quite common and would 

be worth our pointing that out. 

There weren't enormous differences. There are 

three people here and they can indicate whether they disagree 

with that. But that was a fairly common result. It made 

"it especially useful to go back a second time. But we should 

mention something about that. 

CHAIRMAN LIPPMANN: Jim, did you want to say something? 

DR. WARE: Well, I guess I'm trying to digest all 

this discussion. 

As a person who has had nothing directly to do with 

this area, I'm very keenly interested in this kind-of work. 

And I'm trying to think about and I'm very interested to 

hear the strong reservations that are being expressed about 

this kind of work. 

And I'm trying to connect those two "facts. From my 

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own point of view, part of what's involved here is that the 

information that people are more comfortable providing is 

oftentimes not the information that's really needed or 

directly relevant to the decision that has to be made. 

And I*can understand that people have difficulty 

organizing the information in a way that is more quantitative, 

let's say. And I think that is a very real part of the 

process. 

And yet it seems to me that the payoff for that 

is that we do, then, have a quantitative, even a visually 

quantitative, summary of that individual's point of view. 

And I think that that kind of information has a role to play 

in decisionmaking. 

I think, in fact, to take the extreme alternative, 

I think one alternative that we sometimes choose instead 

is to leave things sufficiently vague that there's a wide 

range of decisions that, in fact, would not be accepted that 

comfortably if the individuals who were really knowledgeable 

had an opportunity to be more interactive about the regulatory 

decisions. 

• So I really believe this is a way of articulating 

and communicating expert judgments about information in areas, 

as you've said, where we are not able to provide the empirical 

evidence. 

For example, you mentioned the problem of 

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extrapolation of the animal data. What did the animal data 

tell us? What's going to happen if we change the regulatory 

standards? 

That's a perfect example. If we changed the Air 

Ouality Standard of lead to 1 from 1.5, what's going to happer 

to the distribution of exposure? We can't gather data on that, 

question, at least directly. 

So I think I would have quizzed ycu closely about 

exactly how you're going to go about it. And maybe I would 

agree with you about the details. But personally, I feel 

that it remains to be seen whether this is going to work or 

not. 

Maybe people just won't ever come to be comfortable 

"with this approach. But I think there's potential for this 

approach, and it's great enough that we ought to continue 

pushing ahead. 

DR. WALLSTEN: In response to that. You've said 

some things that made me think about some of the other reactions we've had. And I would appreciate it if any people 

who took part would respond to what I'm going to say right 

now. ' • • 

And that is that although people initially felt 

somewhat uncomfortable expressing their uncertainties in 

this quantitative way, by the time we got finished I think 

most of the people with whom we interacted felt that they had 

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seen their own knowledge about the area in a. slightly different way that made them aware of aspects of uncertainty 

regarding implications that they hadn't thought about before 

or about interrelationships. 

And so rather than my saying this, I would like it 

if you could either agree or disagree with me in that regard. 

That would be useful. 

DR. ROSEN: Well, I very much agree with what you 

just said. In general, I've found it to be an extraordinarily 

revealing and challenging exercise. And during the first 

several hours, it was really difficult to feel comfortable 

with the type of questions that were being asked, and, in 

a sense, coming up with information that one is used to either 

""seeing in publications or generating in their own laboratories 

But, in general, I found it to be a remarkably 

revealing — about myself, about how I looked upon all of 

the lead children that I see on a weekly and daily basis. • 

So I came out of the whole experience feeling very positive 

about it. 

Some of this feeling was also passed on to colleague 

who are somewhat closer to the large numbers" of lead-burdened 

children that we followed. And I think it was a very constructive experience. 

DR. HAMMOND: I would like to raise a question. 

Wasn't there, in fact, a similar exercise conducted 

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in regard to carbon monoxide in the incidence of angina? 

I recall seeing a number of experts — the data, rather, from 

the encoding of a number of experts on what they felt the 

effect of various levels of CO in the blood implied in regard 

to the probability of increased angina frequency. 

Does anybody — 

MR. JORDAN: I would like to see that. 

(Laughter) 

DR. HAMMOND: You never saw that? 

(Simultaneous conversation) 

VOICE: That was experimental work. 

DR. CURRAN: Yes. That was one of the papers that 

was passed out at one of our meetings. 

DR. HAMMOND: How useful is that to the people who 

were involved in the decisionmaking about CO? 

DR. CURRAN: They didn*'t use it. They didn't use 

it for that. 

MR. HAINES: That was a development project where 

we had actually two different approaches demonstrating using 

CO as a model. And it was more of looking — a couple of 

different methodological approaches. 

And what we attempted to do is draw up both inputs 

to that, take it..-- and work it into our current methodology. 

MR. JORDAN: That was really a step in leading to 

where we're at today. It was never designed or never intended 

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to be used in decisionmaking at all. 

DR. CHISOLM: All I will add is that it wasn't 

purely guesswork because I had, I'd say, four sets of data 

that I knew about that I drew upon. 

DR. WARE: Actually, that reminds me of one other 

comment I'd like to make. 

You mentioned something about providing data. It 

seems to me in settings where there is a data base available, the natural thing to do is to present those data or 

at least make those data available to a common data base. 

And I wonder what your attitude is about the management of the empirical evidence. 

DR. WALLSTEN: Okay. What I said early on was that 

"with "regard to one of the health effects, namely, elevated EP, 

the data were so good that it was not necessary to get judgments at all. We could do all of the risk assessments just 

purely with the data base. 

As was mentioned earlier, if the data are available, 

then, of course, it's not necessary to get the judgments. 

And so --

• DR. WARE:: And what if there's a little'bit of 

data available? 

DR. WALLSTEN: Well, if there's a little bit of 

data available, then we discuss that. And, I mean, obviously, 

if they are experts then they're going to be aware of it. 

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DR. WARE: Well, that's yes and no. I mean, 

did you find that people are not aware — are not uniformly 

aware of the data base. And I'm interested — 

MR. JORDAN: The criteria document is the data 

base. 

DR. WALLSTEN: That's right. That's right. I mean, 

that's what's referred to. Correct. 

DR. CURRAN: But in the process of development, we 

also acknowledge the fact that sometimes there would be so 

little data available that this was not a useful tool either 

You know, it depends. There's that range in betweer 

Sometimes there's so little data available. I mean, I was 

acknowledging the process. 

CHAIRMAN LIPPMANN: Les? 

MR. GRANT: I just asked — you said you have the 

data. 

(Laughter) 

MR. GRANT: I — 

(Simultaneous conversation) 

DR. CHISOLM: Well, the Kellogg episode — hemoglobijns 

obtained'there but they never got much publi'city anywhere. 

That's, what, 1056 — I know there were hemoglobins. And 

I know that there were — I know Paul told me the level at 

which decrement — 

CHAIRMAN LIPPMANN: Well, I think if you have an 

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information request then you ought to — 

DR. CHISOLM: There's also information from El Paso 

too. 

DR. ROSEN: We also published a — 

CHAIRMAN LIPPMAN: John, come up to the microphone. 

DR. ROSEN: We also published a paper in the 

mid-'70s in which we included hematocrits (ph) in about 

100 children with various leads. 

CHAIRMAN LIPPMANN: Well, we're running out of 

our scheduled time. I don't begrudge staying somewhat longer 

if you want to discuss some of these issues further. It 

seems that the consensus that this is an exercise which has 

proved interesting and certainly deserves to be followed 

through further. 

And I think we're all anxious to see how well you 

can, if you can, include this in the second draft of the 

criteria document — I'm sorry, the staff paper. And for 

the sample we've seen and, perhaps, very likely also for 

the IQ encoding, there is this middle ground of having some 

data, certainly not enough, and using your expert judgment 

to do it: 

I suspect that the lead exposure, you're in that 

area — at least I think you are, where you don't have enough 

data to use experts' judgments properly. If you can convince 

us otherwise, more power to you. And we look forward to 

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seeing it . 

I mean, I don't know what else we could say in 

summation of this discussion. 

Does anybody else want a chance to have any final 

comment before we close the meeting? 

MR. JORDAN: I'd just add, Dr. Lippmann, that no 

one knows any better than this group that you see sitting 

around here, that's been working on the exposure end of it, 

the challenge that's out there in convincing people. 

And we are not coming here and waving a flag and 

saying that we are ultimately going to do it. But I'd say 

one thing, we are darned sure going to try. 

CHAIRMAN LIPPMANN: I wonder, considering the length 

"of time that it has taken to get one or two encoding operations done, how you could possibly do another one and report 

back to us by the fall. 

MR. JORDAN: It's already done. 

CHAIRMAN LIPPMANN: The IQ. 

MR. JORDAN: The IQ is already done. 

CHAIRMAN LIPPMANN: Yes. But I mean the third 

one. You're suggesting that you're doing ah encoding on 

exposure. 

MR. HAINES: We have work underway right now. And 

so we can hopefully be out talking to experts in the very 

near term and get some exposure parameters. 

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DR. LARSON: There is a large communicable CDC 

study- in — smelter with arsenic exposure pathways where 

they're looking into a lot of different exposure routes. 

CHAIRMAN LIPPMANN: Well, that's data. 

DR. LARSON: Yes, I know. 

CHAIRMAN LIPPMAN: And we-all applaud the use cf 

data, even if it's arsenic. It might be relevant to this. 

And there's lead in it too, obviously. 

But we've heard a teaser that there's an encoding 

exercise on lead exposure. We haven't been briefed on any 

protocols, on any selection procedures for picking people 

who know something about it. And, therefore, considering the 

history of all this, I just wonder personally how you could 

"possibly do this exercise in sufficient time to have it in 

the next draft. 

I just don't see how that's going * to happen unless 

you've all of a sudden learned how to move into high gear 

as compared to the progress in recent years. 

But that's my own observation of this. 

Dr. North? 

' DR. NORTH: I was about to make a 'comment earlier. 

And then Dr. Curran made a beautiful speech saying what I was 

just about to say. 

I don't want my comments earlier to be interpreted 

as urging you to do a subjective probability exercise on the 

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1 exposure side. 

2 I urged you to be careful and to use the best 

3 methods that you can develop. And maybe this will wind up 

4 being a very data intensive exercise using arsenic data as 

5 a surrogate in a Tacoma smelter, or maybe it will involve 

6 interviews with experts in child behavior who have studied 

.7 the frequency of mouthing behavior, and you can get a lot of 

8 data from that source. 

9 I am simply urging that a substantial effort be 

10 given to that side of the problem to balance the very careful 

n effort that you've just told us about. 

12 MR. JORDAN: And also we are looking at the possi13 bility of maybe even breaking the NHANES data down a little 

14" bit farther and then you could get some idea of what kids 

15 are exposed to with the air lead levels of dust, and so, in 

i6 this area as compared to what their blood lead levels are. 

!7 And that's another surrogate for using the direct 

18 expsoure model. Again, the challenge is tough and I don't 

19 back away from it that it is a tough challenge. But I repeat 

20 my statement, we're going to darned sure try. 

21 ' CHAIRMAN LIPPMAN: We've enjoyed t'he opportunity 

22 to comment to you on your staff paper and your emerging 

23 process of subjective probability encoding, and the use of 

24 that in the staff paper. 

25 I hope our comments have been constructive and 

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useful to you, and we look forward to seeing your next draft, 

MR. JORDAN: Thank you. 

CHAIRMAN LIPPMANN: Thank vou all. 

(Whereupon, at 12:02 p.m., the hearing was 

adjourned.) 

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REPORTER'S CERTIFICATE 

This is tc certify that ihe attached prcceedings 

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in the matter cf: 

SCIENCE ADVISORY BOARD, CLEAN AIR 

SCIENTIFIC ADVISORY BOARD -(CASAC) 

SUBCOMMITTEE ON LEAD. 

were held as herein appears and that this is the original 

itranscript thereof for the file of the Department 

I 

i or Carmiission. 

Official Reporter 

DATE: JUN E 3, 19 85 

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