UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

 WASHINGTON D.C. 20460 

OFFICE OF THE ADMINISTRATOR 

SCIENCE ADVISORY BOARD 

July 18, 2008 

EPA-CASAC-08-016 

The Honorable Stephen L. Johnson 

Administrator 

U.S. Environmental Protection Agency 

1200 Pennsylvania Avenue, NW 

Washington, D.C. 20460 

Subject: Clean Air Scientific Advisory Committee (CASAC) Comments and 

Recommendations Concerning the Proposed Rule for the Revision of the 

National Ambient Air Quality Standards (NAAQS) for Lead 

Dear Administrator Johnson: 

The Clean Air Scientific Advisory Committee (CASAC), augmented by subject-matterexpert Panelists — collectively referred to as the CASAC Lead Review Panel (CASAC Panel) 

— met via a public teleconference on June 9, 2008. The purpose of this conference call meeting 

was to hold discussions and provide comments concerning the Environmental Protection 

Agency’s (EPA) Proposed Rule for the Revision of the National Ambient Air Quality Standards 

(NAAQS) for Lead (40 CFR Parts 50, 51, 53 & 58), which the Agency released on May 1, 2008, 

and which was published in the Federal Register on May 20, 2008 (73 FR 29184–29291). The 

CASAC Panel held a subsequent public teleconference meeting on July 8, 2008 to discuss, and 

for the chartered CASAC to approve, the draft letter (dated June 30, 2008) containing our 

comments and recommendations. The CASAC Panel roster is enclosed.

While the CASAC is pleased that the Agency has recommended substantially lowering

the allowable air concentration (i.e., the level of the NAAQS) for lead in ambient air — which 

has not been revised since 1978 — the CASAC has several critical concerns vis-à-vis the Notice 

of Proposed Rulemaking (NPR), including: 

• ongoing problems with respect to the implementation of EPA’s revised NAAQS review 

process; 

• the last-minute introduction of a new analytical framework — i.e., the “Air-related IQ 

Loss Evidence-based Framework” — as the basis for setting the primary (human-health

based) Lead NAAQS — a framework that was not previously presented for review by the 

CASAC or the public and also apparently excludes other analyses that had been produced 

to date by the Agency and subject to such external review; 
• the Agency’s consideration of values for certain critical parameters (e.g., the air-to-blood 

ratio and the slope of the concentration-response function curve) in this analytical 

framework that are contrary to those recommended by the CASAC, and that would 

justify a significantly-higher level for the primary Lead NAAQS than the CASAC 

recommended — at the expense of the values for those selfsame parameters that the 

CASAC documented as being most relevant for the low levels of blood lead (Pb) found 

in U.S. children today; 

• the misrepresentation of the CASAC’s statement that “the primary lead standard should 

be set so as to protect 99.5 % of the population from exceeding an IQ loss of 1-2 points” 

to wrongfully suggest that CASAC declared that an average loss of one to two IQ points 

in the population was an acceptable public-health endpoint; and 

• the Agency’s proposal of a range for the level of the primary standard that includes an 

upper bound (i.e., 0.3 μg/m3

) which is higher — and therefore less health-protective — 

than that recommended in the final EPA Staff Paper and by the CASAC in any of its 

previous letters to you on this subject. 

The following paragraphs describe in detail these and other concerns that the CASAC 

identified in the Agency’s proposed rule for the revision of Lead NAAQS and, where applicable, 

reiterate the scientific basis for the CASAC’s previous recommendations. 

Implementation of Agency’s Revised NAAQS Review Process 

Before commenting on the substance of the NPR, the members of the chartered 

(statutory) CASAC wish to note that they are extremely, and increasingly, concerned about the 

lack of a reliable, standard “roadmap” for the implementation of the new NAAQS review 

process, as starkly illustrated by the content of this NPR. With the introduction of any new 

process, of course, it is essential that such a “path forward” be clearly delineated and followed 

from the outset. However, CASAC members cannot overstate how dissatisfying it has been to 

observe the introduction of the Agency’s revised process for reviewing the NAAQS — 

especially in the middle of the current review of the Lead NAAQS — without any discernible, 

well-organized plan. 

As a significant example of the root cause of the CASAC’s frustration, we noted in our 

January 23, 2008 letter on this subject (EPA-CASAC-08-008) that, in the memorandum from

EPA Deputy Administrator Marcus Peacock dated December 7, 2006, the Agency stated the new 

process would include a true policy assessment that reflects the views of EPA management — to 

be published in the Federal Register as an advance notice of proposed rulemaking (ANPR) — 

that would “describe a range of options for standard setting, in terms of indicators, averaging 

times, [statistical] form, and ranges of levels for any alternative standards,” along with the 

underlying scientific justification and supporting data and analyses for each of these.” The 

Deputy Administrator’s memo goes on to state that such a policy assessment would “help ... 

‘bridge the gap’ between the Agency’s scientific assessment and the judgments required of the 

Administrator in determining whether it is appropriate to retain or revise the standards.” 

Therefore, the CASAC was surprised to read in the NPR that, “in analyses subsequent to the 

Staff Paper and ANPR, the Agency has primarily considered the evidence in the context of an 

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alternative evidence-based framework’’ (73 FR 29238, italics not in original) — that is, the 

aforementioned “air-related IQ loss framework.” While it is entirely reasonable to expect that 

the policy assessment contemplated by the Deputy Administrator’s December 2006 memo would 

include such an “evidence-based” analytical framework, the CASAC notes with dismay that this 

alternative framework is not found in the Lead Staff Paper, the Lead Risk Assessment or the 

ANPR for the Lead NAAQS. 

Therefore, the CASAC is led to conclude that the ostensible scientific basis for standardsetting that had been previously presented for rigorous review by the CASAC and the public was 

substituted at the last minute for an “alternative” analytical framework that EPA plainly notes 

was their primary consideration as the basis for the proposed rule for the Lead NAAQS. At a 

minimum, the manner in which this process is being implemented suggests that the Agency is 

“winging it” in an ad hoc, rather than a systematic, manner. This is not what the public expects 

of their EPA. 

Finally, the CASAC notes with disappointment that, to date, there has been no response 

from the Agency to our January 23, 2008 letter. In that letter, the CASAC complimented certain 

features of the new NAAQS process (e.g., the “kick-off” science workshop and the integrated 

science assessment. However, the CASAC also requested a modification of other aspects of the 

revised process (such as the absence of a meaningful policy assessment discussed above) that 

appear to be ever-shifting and that tend to conceal the Agency’s underlying scientific analyses 

from its own, statutorily-mandated scientific advisory body. 

Introduction of New Air-Related IQ Loss Evidence-based Framework 

By the Agency’s own acknowledgment, as noted above, the analyses that led to the 

proposed range for the standard, especially the upper bound of 0.3 μg/m3 (and possibly extending 

as high as 0.5 μg/m3

), are based primarily on consideration of the evidence found “in the context 

of an alternative evidence-based framework” resulting from analyses conducted subsequent to 

the release of the Final Lead Staff Paper (November 1, 2007) and the ANPR for the Lead 

NAAQS (December 17, 2007) — that is, the evidence in a single new meta-analysis, entitled the 

“Air-related IQ Loss Evidence-based Framework.” The following comments are focused 

primarily on this new analytical framework: 

1. Timing: In the professional judgment of the CASAC, the issuance of the NPR is far too late 

a point in the regulatory process to introduce a set of new and apparently determinative risk 

calculations. The CASAC notes that the Agency’s stated intent is that this evidence-based 

framework “builds on a recommendation by the CASAC Pb Panel” (73 FR 29237). The 

CASAC infers that this recommendation stems from the information contained in Appendix 

D of the CASAC’s letter of March 27, 2007 (EPA-CASAC-07-003) concerning its review of 

the 1st Draft Lead Staff Paper (December 2006) and the Draft Lead Exposure and Risk 

Assessments (December 2006). The CASAC included Appendix D in its letter in order to 

provide the Agency with several population-based risk assessment analyses for the primary 

Lead NAAQS. However, the CASAC questions why EPA’s analyses reflected in this “Airrelated IQ Loss Evidence-based Framework” were not explicitly presented to the CASAC 

much sooner, either as part of the Agency’s 2nd Draft Lead Human Exposure and Health Risk 

Assessments (July 2007), the Final Lead Risk Assessment (November 2007), or the Final 

3
Lead Staff Paper (November 2007) — or, at the very least, aired for open review by the 

CASAC and the public in the ANPR (December 2007). Instead, at this very late stage in the 

rulemaking process, we are presented with a set of heretofore unseen quantitative analyses — 

an unfortunate scenario that, by definition, precludes an in-depth, thoughtful deliberation by 

the CASAC. Our objections to these analyses are noted in detail below. Moreover, there is 

considerable concern that this might be an example of EPA’s “standard operating 

procedures” under the new NAAQS review process. 

2. Exclusivity: All other previous analyses, risk/exposure assessments, staff, CASAC and 

public recommendations appear to have been set aside, with this single new meta-analysis 

used as the exclusive basis for the proposed NAAQS level. The range of proposed standards 

appears to be predominantly driven by alternative — and, in the CASAC’s judgment, 

unwarranted — assumptions of the appropriate concentration-response (C-R) functions to 

relate IQ score point reductions to blood Pb concentrations, combined with a policy judgment 

that a mean population loss of up to two IQ points is the desired health outcome of a revised 

Lead NAAQS. Significantly, the CASAC notes that, aside from this new “air-related IQ loss 

evidence-based framework,” no other analyses are presented that support a level as high as 

0.3 (or 0.5) μg/m3

.

3. Air Pb-to-blood Pb ratios: The analytical results are constrained to an assumed range of 

air-to-blood ratios of 1:3 to 1:7, which is described as being consistent “with the results and 

observations drawn from the exposure assessment, including related uncertainties” (73 FR 

29197). But this is only true if one: (1) discards the many estimated ratios that fall above this 

range; (2) ignores the clear indications that the air Pb to blood Pb ratio increases as both air 

Pb and blood Pb decrease; and (3) assumes that the related “uncertainties” are directionallybiased and somehow justify the use of lower ratios that are more representative of the much 

higher air Pb and blood Pb levels found in the U.S. in the 1970s and 80s. By contrast, EPA’s 

Final Lead Staff Paper noted that, while “there is uncertainty and variability in the absolute 

value of an air-to-blood relationship, the current evidence indicates a notably greater ratio... 

e.g., on the order of 1:3 to 1:10” (p. 5-17) — that is, not 1:3 to 1:7.

Even from EPA’s 1986 Air Quality Criteria Document (AQCD) for Lead, the 

analysis cited as Brunekreef et al. (J. Air Pollut. Control Assoc. 1983; 33: 872-876) indicated 

an air-to-blood ratio of 1:8.5. The Schwartz and Pitcher analyses (Schwartz, J., Pitcher, H., 

J. Official Stat. 1989; 5(4): 421-431) suggest a ratio of 1:9 or 1:10. Additionally, results 

from Hayes et al. (Pediatrics 1994; 93:195–200) suggested a range from about 1:6 (at high 

air Pb levels near 1 μg/m3

) to 1:16 (at ambient air Pb of about 0.25 μg/m3 — which are within 

the range currently being considered for the Lead NAAQS). In EPA’s Final Lead Risk 

Assessment, estimated ratios ranged from 1:2 to 1:9 across the range of alternative standards 

considered for the urban case study and from 1:10 to 1:19 across the range of alternative 

standards considered for the primary smelter. The NPR discredits these risk assessment 

calculations by noting (without attribution of authorship) that “some have suggested, 

however, that the regression modeling ... could produce air-to-blood Pb ratios that are biased 

high” (73 FR 29197), although it later notes (73 FR 29215) that the ratios used in the risk 

assessment “reflect a subset of air-related pathways related to inhalation and ingestion of 

indoor dust [and that] inclusion of the remaining pathways would be expected to yield higher 

ratios.” The lower end of the proposed range (1:3) reflects the much higher air and blood 

levels encountered decades ago, while the upper end of the range (1:7) fails to account for the 

4
higher ratios expected at lower current and future air and blood Pb levels, especially when 

multiple air-related lead exposure pathways are considered. 

The NPR states (73 FR 29197), “For the general urban case study, air-to-blood ratios 

ranged from 1:2 to 1:9.... [and] this pattern of model-derived ratios generally support the 

range of ratios obtained from the literature and also supports the observation that lower 

ambient air Pb levels are associated with [a] higher air-to-blood ratio.” As several CASAC 

Panel members noted in their individual written comments attached to the CASAC’s March 

27, 2007 letter (EPA-CASAC-07-003), the best documented evidence for the blood-to-air 

ratio under current conditions is based on actual epidemiology data showing that declines in 

U.S. national blood Pb levels from the National Health and Nutrition Examination Survey 

(NHANES) surveys tracked declines in EPA- and state-monitored air Pb levels over the same

time period and the air-to-blood ratio was 1:10. Given that there is agreement that the lower

the current air Pb levels the higher the air-to-blood ratio, the CASAC recommends that the 

Agency use an air-to-blood ratio closer to 1:9 or 1:10 as being most reflective of current 

conditions.

4. C-R Functions: The critical concentration-response functions used in this meta-analysis 

represent the estimated slope of the relationship between IQ point decrements and blood Pb 

concentration. As summarized in Table 1 of the NPR (73 FR 29203), the analysis identifies 

two groups of C-R functions — one with steeper slopes (ranging from -1.71 to -2.94 IQ 

points per μg/dl blood Pb) and one with shallower slopes (ranging from -0.4 to -1.79 IQ 

points per μg/dl blood Pb). The median value of the shallow-sloped group (-0.90) is 

subsequently used (as the “2nd group of C-R functions”) in the summary Table 7 “Estimates 

of Air-Related Population Mean IQ Loss for Children Exposed at the Level of the Standard” 

(73 FR 29239). Like the lowest air-to-blood Pb ratio (1:3), the shallow-slope C-R function 

(-0.9) is based on analyses of populations exposed to much higher air Pb concentrations and 

exhibiting much higher blood Pb levels than is appropriate for current U.S. populations and 

the levels under consideration for a revised Lead NAAQS. 

For example, the median blood Pb level for children one to five (1-5) years of age 

from the NHANES survey dropped from 3.5 μg/dl in 1988–91 to 1.9 μg/dl in 2003–04 (at 

which time the 90th percentile blood Pb level was 3.5 μg/dl. However, all eight of the 

“shallow slope” C-R functions presented in Table 1 had geometric mean blood Pb levels 

(indicated as “BLL” in Table 1) greater than 3.3 μg/dl, and the four studies with slopes below 

the median value of -0.9 IQ points/μg/dl BLL had geometric mean blood levels ranging 

between 4.3 and 9.7 μg/dl. Within the shallow-slope group, the only studies with geometric 

mean BLLs less than 4 μg/dl (which were the only studies in that group based entirely on 

U.S. population groups) had slopes of -1.6 and -1.8 respectively. It is only the combination 

of the lowest C-R slopes and lowest air Pb to blood Pb ratios — both representative of much 

higher exposure conditions of 30 years ago — that provides any basis for considering a 

standard as high as 0.3 μg/m3

. 

In questioning the validity of the higher slope C-R functions (typically based on 

lower blood Pb level population subsets of larger population studies), the NPR (73 FR 

29209) first notes that “these analyses are quite suitable for the purpose of investigating 

whether the slope at lower concentration levels is greater compared to higher concentration 

levels” — but then cautions that the “use of such coefficients as the primary C-R function in 

5
a risk analysis such as this may be inappropriate.” The NPR further notes that, while a subset 

of children with maximal blood Pb levels below 7.5 μg/dl “may better represent current 

blood Pb levels, not fitting a single model using all available data may lead to bias” (73 FR 

29209). Therefore, the NPR admits that the slope of the C-R functions steepens at lower 

concentration and also concedes that this is more reflective of the current blood Pb levels. 

However, the NPR then concludes that limiting the C-R analysis to this range of blood Pb 

levels would introduce “bias.” This vague statement is not only completely unscientific 

(since any assertion of “bias” should be accompanied by a demonstration of why that is the 

case and include appropriate references), it is also at best a specious argument, since we are 

indeed concerned with current blood Pb levels in the setting of a health-protective NAAQS, 

not with blood Pb levels of the past.

Furthermore, the CASAC rejects the suggestion that the existence of “a larger set of 

studies” (73 FR 29238) indicating C-R functions with shallower slopes is scientificallyrelevant for choosing the most appropriate C-R functions for risk analyses. Rather, the 

selection of C-R function should be based on determining which studies indicate slopes that 

best reflect the current, lower blood Pb levels for children in the U.S. — which, in this 

instance, are those studies from which steeper slopes are drawn. 

In turn, the CASAC notes that three additional studies have recently been published 

that confirm the steep slope at the lowest blood lead concentrations (Surkan et al., 

NeuroToxicology 2007; 28:1170–1177; Solon et al., J Pediatr 2008; 152:237–43; and Jusko 

et al., Environ Health Perspect 2008; 116:243–248, the last of which is a follow-up of the 

cohort first described in Canfield et al., New Engl J Med 2003; 348:1517–26).

5. Target IQ Decrements: The air-related IQ loss framework proposes a target mean IQ 

decrement of roughly one to two (1-2) points in the population as a level of damage that the 

proposed standard is intended to protect against. This target level has been erroneously 

attributed as being the CASAC’s recommendation. The use of this target level is 

inappropriate for several reasons. First, in the CASAC’s letter dated March 27, 2007 (EPACASAC-07-003) from its review of the Agency’s 1st Draft Lead Staff Paper and Draft Lead 

Exposure and Risk Assessments, the CASAC wrote that “the CASAC Lead Review Panel 

considers that a population loss of 1-2 IQ points is highly significant from a public health 

perspective. Therefore, the primary lead standard should be set so as to protect 99.5% of the 

population from exceeding that IQ loss” (italics in original).

The CASAC wishes to emphasize that this comment refers to 1-2 IQ points as being a 

“highly significant” loss to be prevented — not as a desired national damage level goal that a 

standard should be set to assure. The CASAC also notes that the recommendation is that IQ 

decrements as large as this should be prevented in all but a small percentile of the population 

— and certainly not accepted as a reasonable change in mean IQ scores across the entire 

population. Indeed, if a loss of one IQ point (rather than losses of up to 3.9 points) in mean 

IQ levels were considered a significant loss to be prevented, this analysis would point to a 

range of proposed standards between 0.05 and 0.2 μg/m3

, with the lower end of that range 

being more consistent with the higher C-R slopes and higher air-to-blood ratios 

representative of current U.S. ambient air and blood lead concentrations. However, by 

combining the lowest air-to-blood Pb ratios (1:3), the shallowest C-R slope (-0.9) and a 

higher-than-acceptable IQ decrement endpoint (>1 IQ point), the NPR subsequently, even 

6
shockingly, goes on to suggest (73 FR 29244) that a standard as high as 0.5 μg/m3

 would 

somehow be adequate to protect public health — while failing to point-out that, at the higher 

air-to-blood ratios and steeper C-R slopes more representative of current U.S. exposures, 

this contemplated level of the standard would allow mean losses of five (5) IQ points or 

more. 

Level of the Primary Lead Standard 

As noted above, the proposed upper-bound level of 0.3 μg/m3 for the revised Lead 

NAAQS lies above the upper bound of levels recommended by both EPA Staff and by the 

CASAC Panel. The NPR indicates (73 FR 29190) that three general sets of recommendations 

were taken into account in developing this proposal: “(1) staff assessments ...upon which staff 

recommendations for revisions to the primary Pb standard are based, (2) CASAC advice and 

recommendations...and (3) public comments...”; and further states that “among the many public 

comments the Agency has received in this review regarding the level of the standard, the 

overwhelming majority recommended appreciable reductions in the level, e.g., setting it at 0.2 

μg/m3

 or less...” (73 FR 29241). (For the CASAC’s previous advice to the Agency concerning 

this CASAC-recommended level of the Lead NAAQS, see our letters dated March 27, 2007 

[EPA-CASAC-07-003, p. 6 & Appendix D]; September 27, 2007 [EPA-CASAC-07-007, p. 2]; 

and January 22, 2008 [EPA-CASAC-08-007, pp. 2, 5].) Accordingly, since the overwhelming 

majority of public comments, the recommendations in the EPA Staff Paper and underlying risk 

and exposure analyses, and the CASAC Panel’s unanimous recommendations advocated a 

maximum level of 0.2 μg/m3 or less, it is not clear either where this proposal for a higher (that is, 

less stringent) level of 0.3 μg/m3 level for the primary Lead NAAQS originated (i.e., on what 

scientific basis) or why it is necessary at this late stage in the rulemaking process to seek 

additional public comment on levels for the Lead NAAQS ranging as high as 0.5 μg/m3

. 

Lead NAAQS Indicator 

In several rounds of previous comments, the CASAC Panel recommended that a revised 

(and substantially-lowered) Lead NAAQS should be accompanied by a transition of the sampling 

indicator from total suspended particulates (TSP) to a low-volume ambient air monitor for lead 

in particulate matter (PM) less than 10 micrometers in diameter (PM10) in ambient air. In the 

CASAC’s advice dated January 22, 2008 (EPA-CASAC-08-007), the CASAC noted that the 

CASAC Panel “unanimously supported the selection of an [PM10] indicator that can be more 

robustly measured and thus would be more representative of actual population exposures,” 

adding that “a more accurate and precise Pb-PM10 indicator would provide a more stable 

determination of compliance with the new lower Lead NAAQS.” With regard to concerns over a 

potential loss of ultra-coarse lead particles by PM10 samplers, the CASAC Panel further noted 

that “it would be well within EPA’s range of discretionary options to accept a slight loss of ultracoarse lead at some monitoring sites by selecting an appropriately conservative level for the 

revised Lead NAAQS.” In a subsequent teleconference consultation by the CASAC Ambient 

Air Monitoring and Methods (AAMM) Subcommittee held on March 25, 2008, a majority of the 

subcommittee members also supported a transition from TSP to low-volume PM10 sampling for 

lead (see EPA-CASAC-08-010 dated April 14, 2008). 

7
The CASAC needs to call attention to the fact that these recommendations were based, in 

part, on an assumption that the level of the primary Lead NAAQS would be “substantially” 

lowered to the EPA Staff-recommended range (with an TSP indicator) of between 0.1 to 0.2 

μg/m3

 as an upper bound and 0.02 to 0.05 μg/m3 as a lower bound (with the added consideration 

that the selection be made somewhat “conservatively” within this range to accommodate the 

potential loss of ultra-coarse lead with a PM10 Pb indicator). For example, at most populationorientated monitoring sites, levels of PM10 Pb are essentially the same as TSP Pb, but at sourceoriented monitoring sites with high coarse mode particulate lead emissions, TSP Pb was roughly 

twice as high as PM10 Pb. This factor-of-two difference is small compared to the factor of 10 to 

100 of the recommended lowering in the level of the standard, and could be readily 

accommodated by considering a slightly more conservative upper bound of 0.1 μg/m3

 rather than 

0.2 μg/m3

. 

However, since with the publication of this proposed rule for the revision of the Lead 

NAAQS the Agency now appears to disagree with previous staff recommendations — as well as 

those of the CASAC and the “overwhelming majority” of the public — and is considering an 

upper bound of 0.3 μg/m3 and possibly as high as 0.5 μg/m3

, a transition from TSP to PM10 at 

these much less protective upper levels of the proposed range could represent a critical 

weakening of the health protection afforded at the level of the standard that the CASAC 

proposed. Significantly, a particulate (PM10) Lead standard at 0.5 μg/m3

 could potentially allow 

TSP Pb levels as high as 1 μg/m3 at sites near large sources with coarse-mode particulate lead 

emissions. Therefore, if the level of the standard is set toward the upper end of the range the 

Agency is now considering, the CASAC is unanimous in its recommendation that the current 

TSP indicator should not be changed. As previously recommended, a transition to a PM10

indicator would be preferable, but only at a level conservatively below an upper bound of 0.2 

μg/m3

 or lower. 

Lead NAAQS Averaging Time and Form

The NPR proposes consideration of a monthly averaging time with a “second highest 

month in three years” form, but also seeks comment on retaining the current “calendar” quarter 

“not to be exceeded” form. The CASAC wishes to emphasize that there is no logic for averaging 

only by “calendar” quarter, as there is nothing unique about effects that may occur exclusively 

during the four calendar seasons. A “rolling” three-month (or 90-day) average would be more 

logical than a “calendar” quarter. The CASAC’s previous recommendations — both in the 

current review cycle and during the prior review of the Lead NAAQS conducted in the 1980s — 

advocated reducing the averaging time of the Lead NAAQS from “calendar” quarter to monthly, 

with the rationale that adverse effects could result from exposures over as few as 30 days’ 

duration. A monthly or “rolling” 30-day averaging time with a “not to be exceeded” form would 

be more protective against adverse short-term effects than a form (such as a “second-highest 

month in three years”) that periodically allows a month of exposures to much higher 

concentrations. 

Zero Level for the Lead NAAQS 

 The NPR has raised the question of the feasibility of a Lead NAAQS of “zero.” While it 

would not be practical to set an enforceable primary Lead NAAQS of zero, it is both entirely 

8
appropriate and indeed very important that we as a Nation have the goal of reducing exposure of 

our children to lead to as close to zero as feasible. The reasons for this are numerous, and 

include: (1) lead is an apparent non-threshold neurotoxicant that reduces cognitive abilities in 

children (that is, by directly affecting children’s IQ loss) so that the smaller the amount of Pb in 

air and from other sources of lead, the smaller the blood Pb and associated IQ loss; (2) such 

neurotoxic effects of lead as IQ loss appear to be persistent and may be irreversible; and (3) the 

environmental reality for childhood lead exposures is that these exposures often occur 

concurrently with exposures to mixtures of other neurotoxicants, with these multiple exposures 

producing an additive neurotoxicity over that for lead alone. Nonetheless, consistent with the 

CASAC’s previous advice in this current review cycle for the Lead NAAQS, the CASAC 

continues to believe that the level of the primary Lead standard unanimously recommended by 

the CASAC — i.e., an upper bound for the primary Lead NAAQS of no higher than 0.2 μg/m3

— is necessary to provide an adequate margin of safety for the protection of human health, 

including susceptible subpopulations such as children, as explicitly required by the Clean Air Act 

for primary NAAQS. 

The CASAC stands ready to assist you by advising the Agency concerning the scientific 

basis on which to base your scientific policy judgments, as EPA Administrator, in setting the 

NAAQS. It is our sincere desire and goal to work more closely and effectively with the Agency 

in the future. As always, the members of the CASAC wish EPA well in our vital — and, as 

previously stated, our mutual — efforts to protect both human health and the environment. 

 Sincerely, 

 /Signed/ 

Dr. Rogene F. Henderson, Chair 

Clean Air Scientific Advisory Committee 

Enclosure 

9
NOTICE 

This report has been written as part of the activities of the U.S. Environmental 

Protection Agency’s (EPA) Clean Air Scientific Advisory Committee (CASAC), an 

independent Federal advisory committee administratively-located under the EPA Science 

Advisory Board (SAB) Staff Office that is chartered to provide extramural scientific 

information and advice to the Administrator and other officials of the EPA. The CASAC 

is structured to provide balanced, expert assessment of scientific matters related to issue 

and problems facing the Agency. This report has not been reviewed for approval by the 

Agency and, hence, the contents of this report do not necessarily represent the views and 

policies of the EPA, nor of other agencies in the Executive Branch of the Federal 

government, nor does mention of trade names or commercial products constitute a 

recommendation for use. CASAC reports are posted on the EPA Web site at: 

http://www.epa.gov/casac. 

10
U.S. Environmental Protection Agency 

Clean Air Scientific Advisory Committee (CASAC) 

CASAC Lead Review Panel

CASAC MEMBERS 

Dr. Rogene F. Henderson (Chair), Scientist Emeritus, Lovelace Respiratory Research Institute, 

Albuquerque, NM 

Dr. Ellis Cowling, University Distinguished Professor At-Large, Emeritus, Colleges of Natural 

Resources and Agriculture and Life Sciences, North Carolina State University, Raleigh, NC 

Dr. James D. Crapo [M.D.], Professor, Department of Medicine, National Jewish Medical and Research 

Center, Denver, CO 

Dr. Douglas Crawford-Brown, Director, Carolina Environmental Program; Professor, Environmental 

Sciences and Engineering; and Professor, Public Policy, Department of Environmental Sciences and 

Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 

Dr. Donna Kenski, Director of Data Analysis, Lake Michigan Air Directors Consortium (LADCO), 

Rosemont, IL 

Dr. Armistead (Ted) Russell, Georgia Power Distinguished Professor of Environmental Engineering, 

Environmental Engineering Group, School of Civil and Environmental Engineering, Georgia Institute of 

Technology, Atlanta, GA 

Dr. Jonathan Samet [M.D.], Professor and Chairman, Department of Epidemiology, Bloomberg School 

of Public Health, Johns Hopkins University, Baltimore, MD 

PANEL MEMBERS 

Dr. Joshua Cohen, Research Associate Professor of Medicine, Tufts University School of Medicine, 

Institute for Clinical Research and Health Policy Studies, Center for the Evaluation of Value and Risk, 

Tufts New England Medical Center, Boston, MA 

Dr. Deborah Cory-Slechta, Professor, Department of Environmental Medicine, University of Rochester 

School of Medicine and Dentistry, Rochester, NY 

Dr. Bruce Fowler, Assistant Director for Science, Division of Toxicology and Environmental Medicine, 

Office of the Director, Agency for Toxic Substances and Disease Registry, U.S. Centers for Disease 

Control and Prevention (ATSDR/CDC), Chamblee, GA 

Dr. Andrew Friedland, Professor and Chair, Environmental Studies Program, Dartmouth College, 

Hanover, NH 

Mr. Sean Hays, President, Summit Toxicology, Allenspark, CO 

Dr. Bruce Lanphear [M.D.], Sloan Professor of Children’s Environmental Health, and the Director of 

the Cincinnati Children’s Environmental Health Center at Cincinnati Children’s Hospital Medical Center 

and the University of Cincinnati, Cincinnati, OH 

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Dr. Samuel Luoma,* Senior Research Hydrologist, Emeritus, U.S. Geological Survey (USGS), Menlo 

Park, CA 

Dr. Frederick J. Miller, Consultant, Cary, NC 

Dr. Paul Mushak, Principal, PB Associates, and Visiting Professor, Albert Einstein College of Medicine 

(New York, NY), Durham, NC 

Dr. Michael Newman, Professor of Marine Science, School of Marine Sciences, Virginia 

Institute of Marine Science, College of William & Mary, Gloucester Point, VA 

Mr. Richard L. Poirot, Environmental Analyst, Air Pollution Control Division, Department of 

Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT 

Dr. Michael Rabinowitz, Geochemist, Marine Biological Laboratory, Woods Hole, MA 

Dr. Joel Schwartz, Professor, Environmental Health, Harvard University School of Public Health, 

Boston, MA 

Dr. Frank Speizer [M.D.], Edward Kass Professor of Medicine, Channing Laboratory, Harvard Medical 

School, Boston, MA 

Dr. Ian von Lindern, Senior Scientist, TerraGraphics Environmental Engineering, Inc., Moscow, ID 

Dr. Barbara Zielinska, Research Professor, Division of Atmospheric Science, Desert Research Institute, 

Reno, NV

SCIENCE ADVISORY BOARD STAFF 

Mr. Fred Butterfield, CASAC Designated Federal Officer, 1200 Pennsylvania Avenue, N.W., 

Washington, DC, 20460, Phone: 202-343-9994, Fax: 202-233-0643 (butterfield.fred@epa.gov) 

*Dr. Luoma did not participate in the June 9, 2008 or the July 8, 2008 public teleconferences or the CASAC’s 

advisory activity to provide comments on the NPR.

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