UNITED ST ATES E N VI RON M E N T A L PR OTE C TION AGE NCY WASHING T O N D. C. 2046 0

OFFI CE OF THE A D M I N ISTR A T OR SCI E NCE A D VI SORY BO A RD
July 18, 2008

EPA-CASAC-08-016

The Honorable Stephen L. Johnson Adm i nistra tor U.S. Environm ental Protection Agency 1200 Pennsylvania Avenue, NW Washington, D

. C

. 20460

Subject: Clean Air S c ientific Adviso ry Comm ittee (CASAC) Comments and Recommendations Concerning the P r opos ed Rule for the Revision of the National A mbient Air Quality Standards (NAAQS) for Lead

Dear Adm i nistrator Johnson:

The Clean Air Scientific Advisory Comm ittee (C ASAC), augm ented by subject-m atterexpert Panelists — collectively referred to as the CASAC Lea dReview Panel (CASAC Panel)

— m e t via a public teleconference on June 9, 2008. The purpose of this conference call m eeting was to hold discussions and provide comments concerning th e Environmental P r otection Agency’s (E PA) Proposed Rule for the Revision of the National Am bient 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 subsequentpublic teleconference m eeting on July 8, 2008 to discuss, and for the chartered CASAC to approve, the draf t letter (dated June 30, 2008) containing our comments and recomm e ndations. T h e CASAC Panel ros t er is enclosed.

W h ile the C A SAC is pleased tha tthe Agency has recomm ended substan t ially lowerin g 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 Rulem a king (NPR), including:

• ongoing problem s with respect to the impl e m entation of EPA’s revised NAAQS review
process;

• the last-m inute introduction of a new analytical fram e w ork — i.e. , the “Air-re la ted IQ Loss Evidence-based Fram e w ork” — as the basis f o r setting th e prim ary (h um an-health based) Lead NAAQS — a fram ework that was not previously presented for review by the CASAC or the public and also a pparently excludes other analyses that had been produced to date by the Agency and subjec t to such exte rna l rev i ew;• the Agency’s consideration of values f o r certa in c r itica l param e ters ( e.g. , the air-to-blood ratio and the slope of the concentration-re sponse function curve) in this analytical fra m ework that are contrary to those r ecomm ended by the C A SAC, and that would justif y a s i g n if icantly-higher lev e l f o r the pr im ary Lead NAAQS than the CASAC

recomm ended — at th e expense of the values f o r those s e lf s a m e param e ters that the CASAC doc um ented as being m o st relevant fo r the low levels of blood lead (Pb) found in U.S. children today;

• the m i srepresentation of the CASAC’s statem en t that “the prim ary lead standard should be set so as to protect 99. 5 % of the population from exceedin g 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 popu lation was an acceptable public-health endpoint; and

• the Agency’s proposal of a range for the leve l of the prim ary standard that includes an upper bound ( i.e. , 0.3 μg/m 3 ) which is higher — and theref ore less he alth -prote ctive — than that recomm ended in the final E P A St aff 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, reitera t e th e scien tif ic ba sis f o r the C A SAC’s previous recom m e ndations.

Implementation of Agency’s Revised NAAQ S Review P r ocess

Before comm enting on the substance of the NPR, the m e m b er s of the chartered (statutory) C A SAC wish to note that they are extrem ely, and in creasingly, concerned about the lack of a reliable, standard “roadm ap” for the implem entation of the new NAAQS review process, as starkly illustrated by the content of this NPR. W i t h the introduction of any new process, of course, it is essent ial that such a “pathforward” be clearly delineated and f o llowed from the outset. However, CASAC m e mbers cannot overstate how dissatisfying it has been to observe the introduction of the Agency’s revised process for reviewing the NAAQS — especially in the m i ddle of the current review of the Lead NAAQS — wit hout any discernible, well-organized plan.

As a significant example of the root cause of the CASAC’s frustration, w e noted in our January 23, 2008 letter on this subject (EPA-C ASAC-08-008) that, in the m e morandum from EPA Deputy Adm i nistrator Marcu s Peacock date d Decem ber 7, 2006, the Agency stated the new process would include a true po licy a ssessment th at ref l e c ts th e views of EPA m a nage m e nt — to be published in the Federal Register as an advance notice of pr oposed rulem a king (ANPR) — that would “describe a range of options for sta ndard setting, in term s of indicators, averaging tim es, [statistical] for m , and ranges of levels for any alternative sta ndards,” along with the underlying scientific justificati on and supporting data and analyses for each of these.” The Deputy Adm i nistrator’s m e m o goes on to state th at such a policy assessm e nt would “help ... ‘bridge the g ap’ between the Agency’s scien tif ic assessm ent and the judgm e nts required of the Adm i nistrator in determ ining whether it is appr o p ria t e to reta in or rev i se 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 consideredthe evid ence in the context of an

2alterna tiv e evidence-based fram ewor k’’ (73 FR 29238, italics not in original) — that is, the aforem entioned “air-related IQ loss f r am ework.” W h ile it is e n tir ely r easo n able to exp ect th at the policy assessm ent contemplated by the Deput y Adm i nistrator’s December 2006 m e mo woul d include suchan “eviden ce-based ” an alytical fram ework, the CASAC notes with dism ay that this alternative framework is not f ound in the Lead Staff Paper, th e Lead Risk Assessment or the ANPR for the Lead NAAQS

.
Therefore, the CASAC is led to conclude that the ostensib le s c ientif ic bas i s f o r standardsetting that had been previously presented for rigorous review by the CASAC and the public was substituted a tthe last m i nute f o r an “ a lte rnativ e” analytical fram ework that EPA plainly notes was their primary consideration as the basis for the proposed ru le for the Lead NAAQS. At a

m i ni mu m, the m a nner in which this process is being implemented suggests that the Agency is “winging it” in an ad hoc , rather than a system atic, m a nner. This is no t what the pu blic exp ects of their EPA.

Finally, the CASAC notes with disappointm e nt that, to date, there has been no response from the Agency to our January 23, 2008 letter. In that letter, the CASAC comp lim e n ted certain features of the new NAAQS process ( e.g. , the “kick-off” science workshop and the integrated science assessm ent. However, the C A SAC also re quested a modification of other aspects of the revised process (such as the ab sence of a m eaningful policy a ssessm ent discussed abo v e) that appear to be ever-shifting and that tend to conceal the Agency’s underlying scientific analyses from its own, statutorily-m andated scientific advisory body.

Introduction of New Air-Related IQ Loss Evidence-based Framew ork
By the Agency’s own acknowledgment, as no ted above, the analyses that led to the proposed range for the standard, es pecially the u pper bound of 0.3 μg/ m 3 (and possibly extending as high as 0.5 μg/m 3 ), are based primarily on consideration of the evidence found “in the context of an alternative evidence-based fram e w ork” resulting from analyses conducted subsequent to the release of the Final L ead Staff Paper (November 1, 2007) and the ANPR for the Lead NAAQS (Decem ber 17, 2007) — th at is, the ev idence in a single new m e ta-an a lysis, entitled the “Air-related IQ Loss Evidence-basedFram ew ork.” The follo wing comments are focused prim arily on this new analytical fram ework:

1. Timing: In the professional judgm ent of the CASAC, the issuance of th e 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 sta t edintent is that th is evid ence- based fra m ework “builds on a recomm endat i on by th e C A SAC Pb Panel” (73 FR 29237). The CASAC infers tha tth is recomm endation s t em s from the inform ation contained in Appendix D of the CASAC’s letter of March 27, 2007 (EPA -CASAC-07-003) concer ning its review of the 1 st Draft Lead Staff Paper (December 2006) and the Draf t Lead Exposure and Risk Assessm ents (Decem ber 2006). The CASAC include d Appendix D in its letter in o r der to provide the Agency with severa l population-based risk assessm e nt analyses for the prim ary Lead NAAQS. However, the CASAC questions w hy EPA’ s analyses reflected in this “Airrelated IQ L o ss Evidence-based Fram e w ork” we re not explicitly presented to the CA SAC much sooner, either as part of the Agency’s 2 ndDraft Lead Hum a n Exposure and Health Risk Assessm ents (July 2007), the Final Lead Risk Assessm ent (Novem b er 2007), or the F i nal

3Lead Staff Paper (November 2007) — or, at th e very least, aired for open review by the CASAC and the public in the ANPR (Decem ber 2007). Instead, at th is very late stage in the rulem a king 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 thes e analyses ar e noted in detail below. Moreover, there is considerable concern that this m i ght be an example of EPA’s “standard op erating procedures” under the new NAAQS r e view process.

2. Exclusivity: All other previous analyses, risk/e xposure assessm e nts, staff, CASAC and public recommendations appear to have been set aside, with this single new m e ta-analysis used as the exclusive basis for the proposed NAAQS level. The range of proposed standards appears to be predom inantly driven by alternative — and, in the CASAC’s judgm ent, unwarranted — assump tions of the appropriate concentration-respons e (C -R) functions to relate IQ score point reductions to blood Pb concentrations, co mbined witha policy jud g m e nt that a m ean population loss of up to two IQ point s is the desired health outcom e of a r e vised Lead NAAQS. Signific antly, the CASAC notes that, asid e fr om this new “air-re l ated IQ loss evidence-based framework,” no other analyses ar e presented that support a level as high as 0.3 (or 0.5) μg/m 3

. 3. Air Pb-to-b lood Pb ratios: The analytical results are cons tr ained to an assum e d range of air-to-blood ratios of 1:3 to 1: 7, which is described as being c onsistent “w ith the results and observations drawn from the exposure assessm en t, including related unc ertainties” (73 FR 29197). But this is only true if one: (1) discards the m a ny estim ated 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 decrea se ; and (3 ) assum e s that the related “uncertainties ” are d i rectionally

biased and som e how justify the use of lower ratio s that are more repres entative of the mu ch higher air P b and blood Pb levels found in the U

. S. in the 1970s and 80s. By contrast, EPA’s Final Lead S t aff Paper noted that, while “there is uncertainty and variability in th e abs o lute value of an air-to-bl ood 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 Crite ria Docum e nt (AQCD) for Lead, the analysis cited as Brunekreef et al. ( J. Air Pollu t. Control Ass o c. 1983; 33: 872-876) indicated an air-to-blood ratio of 1:8.5. The Schwartz and Pitcher analyses (Schwartz, J., Pitcher, H., J. Offic ial S t at. 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 ra nge from a bout 1:6 (at high air Pb levels near 1 μg/m 3 ) to 1:16 (at am bient air Pb of about 0.25 μg/m 3 — which ar e within the range currently bein g considered for the Lead NAAQS). In EPA’s Final Lead Risk Assessm ent, estim ated 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 standard s co nsidered for the prim ary sm elter. The NPR discredits these risk assessm ent calculations by noting (w ithout attribution of authorship) that “som e have suggested, however, that the regression m ode ling ... could produce air-to-blood Pb ratios that are biased high” (73 F R29197), although it late r notes (73 FR 29215) that the ratios used in the risk

assessm ent “reflect a su bset of air-related p a thwa ys rela ted to inha lation and ingestion of indoor dust [ a nd that] inclusion of the rem a ining pathways would be expected to yield higher ratios.” The lower end of the proposed range (1:3) reflects the mu ch higher air and blood levels encou n tered d ecad es ago, while the upper e nd of the range (1:7) fails to account for the

4higher ratios expected at lower curren t and futu re air and blood Pb levels, especially w h en multiple air-related lead expos ure pathways are considered.
The NPR states (73 FR 29197), “For the general urban case st udy, air-to-blood ratios ranged from 1:2 to 1:9.... [and] this pattern of m o del-derived ratios generally support the range of ratios obtain e d from the literature and also supports the observation that lower

am bient air Pb levels are asso ciated with [a] higher air-to-b lood ratio.” As several C A SAC Panel m e m b ers noted in their i ndividual written comm ents at tached to the CASAC’s March 27, 2007 letter (EPA-CASAC-07-003), the best docum e nted evidence for the blood-to-air ratio under current conditions is based on actual epidem iology data showing that declines in U.S. national blood Pb levels from the Nationa l Health and Nutrition Exam ination Survey (NHANE S) surveys tracked declines in EPA- and state-m onitored air Pb levels over the sam e tim e period and the air-to-blood ratio was 1:10. Given that there is agreem ent that the lower the curr ent a i r Pb lev e ls the higher th e air

- to -bloo dratio, 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 cr itical con cen tra tion- respo n se f unction s used in th is m e ta-analy sis represent the estim a ted slope of the relationship between IQ point decrem ents and blood Pb concentration. As summarized in Table 1 of the NPR (73 FR 29203), the analysis identifies two groups of C-R f unctions — one with steeper slopes (ranging from -1.71 to -2.94 IQ points per μg/dl blood P b ) and one with shallower slopes (ranging from -0.4 to -1.79 IQ points per μg/dl blood P b ). The m e dian va lue of the shallow-sl oped group (-0.90) is subsequently used (as the “2 ndgroup of C-R functions”) in th e summ ary Table 7 “Estim ates of Air-Related Population Mean IQ Loss for Children Exposed atthe 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 m u ch higher blood Pb levels than is appropria te for current U.S. populations and the levels under considerati on for a revised Lead NAAQS.

For example, the m e dian 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 tim e the 90 thpercentile blood Pb level was 3.5 μg /dl. However, all eight of the “shallow slope” C-R functions presented in Table 1 had geom etric m ean blood Pb levels (indicated as “BLL” in Table 1) greater than 3.3 μ g /dl, and the four studies with slopes below the m e dian value of -0.9 IQ points/μ g /dl BLL had geom etric m ean blood levels ranging between 4.3 and 9.7 μg/dl. W ithin the shallo w-slope group, the only studies with geom etric

m ean 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 combin ation of the lowest C-R slopes and lowest air Pb to blood Pb ratios — both re presentative of much higher exposure conditions of 30 years ago — t hat provides any basis for considering a standard as high as 0.3 μg/m 3

. In questioning the validity of the higher slope C-R functions (typically based on lower blood Pb level populati on subsets of larger populati on studies), the NPR (73 FR 29209) first notes that “these analyses are qui te suitable for the purpose of investigating whether the slope at low e r concentration levels is greater comp ared to h i g h er concen tration levels” — but then cautions that the “use of such coefficients as the primary C-R function in

5a risk analysis such as this m a y be inappropria te.” The NPR further notes that, while a subset of children with m a xi mal blood Pb levels be low 7.5 μg/dl “may better represent current blood Pb lev e ls, not fittin g a single model using al l available d a ta m a y lead to bias ” (73 FR 29209). Therefore, the NPR adm its that the sl ope of the C-R functions steepens at lower concentration and also concedes that this is m o re reflective of the current blood Pb levels. However, the NPR then concludes that lim iting the C-R analysis to this range of blood Pb levels would introduce “bias.” This vague st atem ent is not only comp letely unscientific (since any assertion of “bias” shou ldbe accomp anied by a demonstration of why that is the case and include appropriate referenc es), it is also at best a specious argument, since we are indeed conc erned with c u rrent blood Pb level s in the se tting of a health-p rotec tive NA AQS, not with blo od Pb levels of the pas t.

Furtherm ore, the CASAC rejects the suggesti on that the existence of “a larger set of studies” (73 FR 29238) indicating C-R functions with shallowe r slopes is scientificallyrelevant for choosing the m o st appropriate C-R functions for ri sk analyses. Rather, the selection of C-R function should be based on determ ining which st udies indicate slopes that best reflect the current, lower blood Pb levels for children in the U.S.

— which, in this instan ce, are those stud ies from which steeper slo p es are dr awn.
In turn, the CASAC notes that three addi tional studies have recently been published that confirm the steep slope at the lo west blood lead concentrations (Surkan et al.

, NeuroToxicology 2007; 28:1170–1177; Solon et al.

, J Pedia t r 2008; 152:237–43; and Jusko et al.

, Environ Health P e rspect 2008; 116:243–248, the last of wh ich 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 fra m ew ork proposes a target m ean IQ decrem ent of roughly one to two (1-2) points in the population as a level of da m a ge that the proposed standard is intended to protect agains t. This target level has been erroneously attributed as being the C A SAC’s recomm enda tion. The use of this target level is inappropriate for several reasons. First, in the C A SAC’s letter dated March 27, 2007 (EPACASAC-07-003) from its review of the Agency’s 1 st Draft Lead Staff Paper and Draft Lead Exposure and Risk Assessm ents, the CASAC wr ote that “ the CASAC Lead Review Panel considers that a population loss of 1-2 IQ point s 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 ” (ita lics in orig inal).

The CASAC wishes to emphasize that th is co mm ent refers to 1-2 IQ points as being a “highly significant” loss to be preven ted — not as a desired national da m a ge level goal that a standard should be set to assure. The CASAC also notes th at the reco mmendation is that IQ decrem ents as large as this should be prevented in all but a sm all percentile of the population

— and certainly not accepted as a reasonable change in mean IQ scores a c ross th e 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 significa nt loss to be prevented, this analysis would point to a range of proposed standards between 0.05 and 0.2 μg/m 3 , with the lower end of that range being more consistent w ith the higher C-R slopes and higher air-to-blood ratios representative of current U.S. ambien t air and blood lead concentrations. However, by

com b ining the lowest air-to-blood Pb ratios (1:3), the shallowest C-R slope (-0.9) and a higher-than-acceptab l e IQ decrem ent endpoint (>1 IQ point), the NPR subsequently, even

6shockingly, goes on to suggest (73 FR 29244) that a standard as high as 0.5 μg/m 3 would somehow be adequate to protect public health — while fa iling 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 woul d allow mean losses of five (5) IQ points or

more.
Level of the Primary L e ad Standard
As noted above, the proposed upper-bound level of 0.3 μg/ m 3 for the rev i sed Lead NAAQS lies above the upper bound of levels recomm ended by both EP A Staff and by the CASAC Panel. The NPR indicates (73 FR 29190) that three general sets of recomme ndations were taken into account in developing this proposal: “(1) staf f assessm ents ...upon which staff

recomm endations for revisions to the prim ary Pb standard are base d, (2) CASAC advice and

recomm endations...and (3) public comments...”; and further states that “among the many public comments the Agency has received in this revi ew regarding the level of the standard, the overwhelm ing m a jority recomm ended appr ec iab l e redu ction s in the leve l, e.g. , setting it at 0.2 μg/m 3 or less...” (73 FR 29241). (F or the CASAC’s previous advice to the Agency concerning this CASAC-recomm end e d level of the L ead NAAQS, see our letters dated March 27, 2007 [EPA-CASAC-07-003, p. 6 & Appendix D]; Se ptem ber 27, 2007 [EPA-CASAC-07-007, p. 2]; and January 22, 2008 [EPA-CASAC- 08-007, pp. 2, 5].) Accordi ngly, since the overwhelm ing

m a jority of public com m e nts, the recomm endat i ons in th e E P A Staf f Pape r and underlying risk and exposure analyses, and the CASAC Panel’ s unanim ous recomm endat i ons advocated a

m a xi mu m level of 0.2 μg/m 3 or less, it is not clear eith er where this proposal for a higher (that is, less stringent) level of 0.3 μg/m 3 level f o r the pr im ary Lead NAAQS originated ( i.e. , on what scientific basis) or why it is ne cessary at th is la te stage in the rulem a king process to se ek additional public comment on levels for the Lead NAAQS r a nging as high as 0.5 μg/m 3

. Lead NAAQS Indicator
In several rounds of previous comm e n ts, the CASAC Panel recommended that a revised (and substantially-lowered) Lead NAAQS should be accomp anied by a transition of the samp ling indicator from total suspended partic ulate s (TSP) to a low-vo lum e am bient air m onitor f o r lead in particu l ate m a tter (P M) les s th an 10 m i crom eters in diam eter (PM 10 ) in am bient air. In the CASAC’s advice dated January 22, 2008 (EPA-C ASAC-08-007), the C A SAC note dthat the CASAC Panel “unanim o usly supported the selection of an [PM 10 ] indicator that can be m o re robustly m easured and thus would be m o re representative of actua l population exposures,” adding that “a m o re accurate and precise Pb-PM 10 indicator would provide a m o re stable determ inatio n of comp liance with th e new lower L ead NAAQS.” W ith regard to concerns over a potential loss of ultra-co arse lead particles by PM 10 samp lers, the CASAC Panel further noted that “it would be well within EPA’s range of disc retionary op tions to accepta slight lo ss of ultracoarse lead at som e m o nitoring sites by selec ting an appropr ia tely con s erv a tive leve l f o r the revised L e ad NAAQS.” In a subsequent te lecon f erence cons ultation by the CASAC Am bient Air Monito ring and Methods (AAMM) Subcomm itt ee held on March 25 , 2008, a m a jority of the subcomm ittee m e m b ers also supported a transition from TSP to low-volum e PM 10 samp ling for lead (see EP A-CASAC-08-010 dated April 14, 2008).

7The CASAC needs to c a ll a tten tion to the f act th at the s e re co mmendations were based

, in part, on an a ssumption that the level of th e prim ary Lead NAAQS would be “substantially” lowered to the EPA Staff-reco mm ended range (with an TSP i ndicator) of between 0.1 to 0.2 μg/m 3 as an upper bound and 0.02 to 0.05 μg/m 3 as a lower bound (with the added consideration that the selection be m a de som e what “conserva tively” with in this range to accomm odate th e potential los s of ultra-co arse lead with a PM 10 Pb indicator). For example, at m o st populationorientated m onitoring sites, levels of PM 10 Pb are essentially the sam e as TSP Pb, but at sourceoriented m o nitoring sites with high coarse m ode particulate lead em i ssions, TSP Pb was roughly twice as h i g h as PM 10 Pb. This factor-of-two difference is sm all comp ared to the factor of 10 to 100 of the recommended lowering in the level of the standard, and could be readily

accomm odat e d by consid ering a sligh tly m o re conservative up per bound of 0.1 μg/m 3 rather than 0.2 μg/m 3

. However, since with the public ation of this proposed rule for the revision of the Lead NAAQS the Agency now appears to disagree with previous staff recomm e ndations — as well as those of the CASAC and the “ove rwhelm ing m a jority” of the pub lic — and is considering an upper bound of 0.3 μg/ m 3 and possibly as high as 0.5 μg/m 3 , atransition from TSP to PM 10 at these mu ch less protective upper levels of the proposed range could represent a critical weakening o f the health protection af forded at the level of the standard tha tthe CASAC proposed. Significantly, a particulate (PM 10 ) Le ad standard at 0.5 μg/m 3 could potentially allow TSP Pb levels as high as 1 μg/m 3 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 unani m ous in its recomm endation that the current TSP indicator should not be changed. As previously recom m e nded, a transition to a PM 10 indicator would be preferable, but only at a level conservati vely below an upper bound of 0.2 μg/m 3 or lower.

Lead NAAQS Averaging Time and Form
The NPR pr oposes consideration of a m onthly averaging tim e with a “second highest month in three years” form, but also seeks co mm e n t on retaining the current “calendar” quarter “not to be exceeded” fo rm . The CASAC wishes to emphasize that there is no logic fo r averaging only by “calendar” quarter, as ther e is nothing unique about effect s that may occur exclusively during the four calendar seasons. A “rolling” three-m onth (or 90- day) average would be m o re logical than a “calendar” quarter. Th e CASA C’s previous recomm e ndations — both in the current review cycle and during the prior review of the LeadNAAQS conducted in the 1980s — advocated reducing the averaging tim e of the Le ad NAAQS from “calendar” quarter to m onthly, with the rationale that adverse effects could result from exposures over as few as 30 days’ duration. A monthly or “rolling” 30-day averaging tim e with a “not to be exceeded” f o rm would be m o re protective against adverse short-term e ffe cts than a form (such as a “second-highest month in three years” ) that periodically allows a month of exposures to mu ch higher concentrations.

Z ero Level for the Lea d NAAQS
The NPR has raised the question of the feasib ility of a Lead NAAQS of “zero.” W h ile it would not be practical to set an enfo rceab le pr imary Lead N AAQS of ze ro, it is both entirely

8appropriate and indeed very impor tant that we as a Nation have the goal of reducing exposure of our children to lead to as cl ose to zero as feasible. The r easons for this are num e rous, and include: (1) lead is an apparent non-threshold neurotoxicant that reduces cognitive abilities in children (that is, by directly affec ting children’s IQ loss) so that the sm aller the am ount of Pb in air and from other sources of lead, the sm aller the blood Pb and associated IQ loss; (2) such neurotoxic effects of lead as IQ loss appear to be persistent a nd m a y be irreversible; and (3) the environm ental reality for childhood lead exposur es is that these exposures often occur concurrently with exposu r es to m i xtures of other n e urotox icants, with thes e mu ltiple ex posures producing an additive neurotoxicit y over that for lead alone. None theless, consistent with the CASAC’s previous adv i ce in th is cu rrent rev i ew cycle for th e Lead NAAQS, the CASAC continue s to believ e tha tthe lev e l of the pr im ary Lead standard unanim ously recommended by the CASAC — i.e. , an upper bound for the prim ary Lead NAAQS o f no higher than 0.2 μg/m 3 — is necessary to provide an adequate m argin of safety for the protection of hum a n health, includ ing su sceptible su bpopulation s such as ch il dren, as exp licitly requi red by the Clean Air Act for prim ary NAAQS.

The CASAC stands ready to assist you by advi sing the Agency concerning the scientific basis on which to base your scientific policy ju dgm e nts, as E P A Adm i ni stra tor, in setting the NAAQS. It is our sincere desire and goal to work m o re closely and effectively with th e Agency in the future. As always, the m e m b e r s of the CASAC wish EPA well in our vital — and, as previously stated, our mutual — efforts to pr otect both hum an health and the environm ent.

Sincerely,

/Signed/

Dr. Rogene F. Henderson, Chair Clean Air S c ientif ic Advisory Comm ittee

Enclosure

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### NOTICE

This report has been written as part of the activ ities of the U.S. Environmental Protection A g ency’s (EP A ) Clean Air Scie n tif ic Advisory Comm ittee (C ASAC), an independent Federal advisory comm ittee adm i nistratively-located under the EPA Science Advisory Board (SAB) Staff Office that is ch artered to provide ex tr amural sc ientif ic inform ation and advice to the Adm i nistrator a nd other officials of the EPA. The CASAC is structured to provide balan ced, exp e rt as sessm ent of scientif ic m a tters r e lated to is su e and problem s facing the Agency. This report has not been reviewed for approval by the Agency and, hence, the contents of th is repo rt do not necessarily represent the views and policies of the EPA, nor of other agencies in the Executive B r anch of the Federal
governm e nt, nor does mention of trade nam e s or commercial products co nstitu te a

recomm endation for use. CASAC reports are posted on the E P A W e b site at: http://www.epa.gov/casac

.

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### U.S. Environmental Protection Agency Clean Air Scientific Advi sory Committee ( CASAC) CASAC Lead Review Panel

CASA C MEMBERS Dr. Rogene F. Henderson (Chair) , Scientist E m erit us, Lovelace Respiratory R esear ch Institute, Albuquerque, NM

Dr. Ellis Co wling , University Distinguished Profess or At -Large, E m eritus, Colleges of Natural Resources and Agriculture and Life Sciences, No rth Carolina State University , Raleigh, NC

Dr. Jam es D. Crapo [M.D.] , Professor, Depart ment of Medicine, National Jewis h Medical and Resear ch Center, Denver, CO

Dr. Douglas Crawford-B rown , Direct or, Carolina Environm ental Program ; P r ofessor, Environm ental Sciences and Engineering; and Professor, Public Po lic y, Depart m e n t of Environmental Scien ces and Engineering, University of North Caro lina at Chapel Hill, Chapel Hill, NC

Dr. Donna Kenski , Direct or of Data Analy s is, Lake Michigan Air Directors Co nsortium (LA D CO), Rosem ont, IL

Dr. Ar mist e a d (Ted) Rus sell , Georgia Power Distinguished Profe ssor of Envir onm ental Engineering, Environm ental Engineering Group, School of Civil a nd Environm ental Engineering, Georgia Institute of Technolog y, Atlanta, GA

Dr. Jonathan Samet [M.D.] , Professor and Chairman, Depart m e n t of Epidem iology , Bl oom berg School of Public Health, Johns Hopki ns Univer sity , Baltim ore, MD

PANEL MEMBERS
Dr. Joshua Cohen , Research Associ at e Professor of Medicine , Tufts University School of Medicine, Institute for Clinical Research and Heal th Polic y St udies, Center for the Evaluation of Value and Risk, Tufts New England Medic a l Center, Boston, MA

Dr. Deborah Cory-Slecht a , Professor, Depart ment of Environm en tal Medicine, University of Rochester School of Me dicine and Dentistry, Roch ester, NY

Dr. Bruce Fowler , Assistant Director for Science, Division of T o x i colog y an d E nvironm ental Medicine, Office of the Director, Age n cy for Toxic Substa nces a nd Disease R e gistry , U.S. Centers for D i seas e Control and P r evention (ATSDR/CDC), Cham blee, GA

Dr. Andrew Friedland , Professor and Chair, Environmental Studies Progra m , Dart m outh College, Hanover, NH

Mr. Sean Hays , President, Summit Toxicolog y , Allen s park, CO

Dr. Bruce Lanphear [M.D.] , Sloan Professor of Childre n’ s Environm ental H e a lth, and the Director of the Cincinnati Children’s Environm ental Health Cen t erat Cincinnati Children’s Hospital Medical Center and the University of Cinc innati, Cincinnati, OH

1Dr. Samuel Luoma

, * Senior Resear ch Hy drologist, E m eritus, U. S. Geological Surve y (USGS), Menlo Park, CA

Dr. Frederick J. Miller

, Consultant, C ary , NC

Dr. Paul Mushak , Principal, PB Associ ates, and Visi ting Prof essor, Albert Einstein College of Medicine (New York, NY), Durha m , NC

Dr. Michael New m an , Professor of Marine Science, School of Marine Sciences, Virginia Institute of Marine Science, College of William & M ary , Gloucester Point, VA

Mr. Richard L. Poirot , E nvironm ental Analy s t, Air Pollutio n Co ntrol Divisio n , Departm e n t of Environm ental Conservation, Verm ont Agency of Natural Resour ces, Waterbur y, VT

Dr. Michael Rabinowitz

, Geochem i st, Marine Biological Laboratory , Wo ods Hole, MA

Dr. Joel Schwartz , Profes sor, Environmental He alt h , Harvar d University School of P ublic Health, Boston, MA

Dr. Frank Spei z er [M. D .] , Edward Kass Professor of Medicine, Ch anning Laboratory , Harvard Medical School, Bost on, MA

Dr. Ian von Lindern , Senior Scientist, TerraGraphics Envir onm ental Engineering, Inc., M o scow, ID

Dr. Barbara Zi elinska , Research Professor, Division of Atm o sphe r i c Science, Desert R esearch Institute, Reno, NV

SCIEN C E A DVIS O RY B O AR D STA FF
Mr. Fred Bu tterfield , CASAC Designated Federal Officer , 1200 P e nnsy l vania Avenue, N.W., Washington, DC, 20460 , P hone: 2 02-3 4 3 -999 4, Fax: 202-2 33-0 6 4 3 ( butterfield. fred@epa.gov )

*D r. Lu om a di d not part i c i p at e i n th e J une 9

, 2 0 0 8 o rth e Ju l y 8, 20 0 8 pu bl i c t e l econfe r e n ces o rth e C A S A C ’ s ad v i so ry acti v ity to prov id e co mmen t s on the NPR.

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