Document QMq04kaXwqGVnEXQwE8RdwkbR

THE AIR TOXICS PROBLEM IN THE UNITEO STATES: AN ANALYSIS OF CANCER RISKS FOR SELECTED POLLUTANTS ;j.S. Environmental Protection Agency Office of Air and Radiation . Office of Policy, Planning and Evaluation May 1905 Eia'ne `iaemisec:er A i a n Jonas 3ern Steigerwa'G Vivian 7 rc ms on lam 003676 DPMC-09767 PREFACE Inis report on the air toxics problem in cue Uniced Scaces is a final version of a September 1 934 u.S. Environmenca 1 Proceccion Agency drafc aocumenc encicled "The Hagnicude and Nature of tne Air Toxics Problem in the United States." Simultaneously witn release of the draft report, EPA solicited comments on the analysis from a peer review panel made up of non-EPA experts in fields such as toxicology, air monitoring, and air pollution control. In response to tne panel's comments, as well as to unsolicited comments received from several organizations, the authors have substantially revised the Executive Summary and have mace changes in ether parts of the report. The revised version more clearly aelineates the limitations and caveats of the analysis. A "'so, tne title of the report has been revised to recognize the limited scope of tne analysis. In acciticn, certain of the risk estimates have been cr.angec as re,, information nas become available. In particular, the risk estimates for nicxel and ethylene dicnloride nave been revised s j o sc a r.t . all y cow n ward and metnyl chloroform has been droppeG x'cr tne analysis. The report nas not been altered where tne Agency is currently considering, but has made no final decis'"n regarcirc, changes ir. certain of the data used in tnis analysis (e.g., potency information) or in the regulatory status of certain Chemicals ex ami nee. Several additions were made to tne report. A new section "as been aoceo tnat delineates current activities-within E = A resulting from the report, including a orief discussion cf the national strategy for air toxics. Air quality data have been evaluated for 1970 and the estimated risks compared to those based on 1930 data to provide a more quantitative estimate cf precress under programs for criteria pollutants. Finally, catfrom personal exposure monitoring nave been converted to accreta national r i s < 'or several compounds to en.nance comparison cf t*e 1 *.:cc r/; jc cog r air toxics problem. LAM 003677 DPMC-09768 EXECUTIVE SUMMARY Go cl s This report summarizes the results of a study which will be used ay the U.S. Environmental Protection Agency (EPA) to previce a basis for consideration of strategies to deal with the ambient air toxics problem in the United States. The study attempted to assess the magnitude and nature of the air toxics problem by developing quantitative estimates of the cancer risks pcsec by selected air pollutants and their sources. Four basic questions were examined: V. What is the approximate magnitude of the air toxics problem, as measured ay the estimated cancer risks* associated with air pollution? 2. What is the nature of the air toxics problem, that is, wnat pollutants and sources appear to cause the proolem anc wnat is tneir relative importance? 2. Does the oroalem vary geographically, and if so, in what ways? t. Are current air toxics data bases adequate? If not, wnat are tne significant data gaps? Context and Limitations Readers of this report should fully understand the study' limitations so tnat its conclusions are interpreted correctly. The analysis was uncertaken to orient EPA to the problem of airoorne carcinogens, to stimulate policy discussions, ana to cu'ce further studies. Despite tne f-act that quantitative estimates c* ris< are presented in this report, the stucy was rt - tec to s-pp:rt s:ecif;c regulatory decisions. Instead, LAM 003678 DPMC-09769 its ^ c a 1 was to ootain a quick assessment of tne air toxics prctlem in the Unitea States, ana as such should be regarded as a "scoping" study only. Only readily available existing data were used regarding compound potencies, emissions, and ambient levels; no new data were collected. The only health effect examined quantitatively was cancer; health data on such effects as teratogenicity are not extensive enough to permit quantification. Also, acute health effects related to short-term exposures were not i r. c 1 u c e d . Consideration of the limited scope of the study, as well as of tne caveats and assumptions that are discussed in the text of tne report, is an important responsibility of those reading and usi'c tnis report. Some of tne important caveats to keep in mind are identified later in tne Executive Summary under "Sources of 'J re e rt a i nty . " In summary, tne risk estimates presentee in tnis report snsj'c ze regarded as only ruug.n approximations of total' incidence an: individual risk, an: should be used in a relative sense only. Estimates for individual compounds are hignly uncertain ana s n c u : used witn extreme caution. The reader is cautioned against applying tnese ris< estimates to specific geographic 1ccaticr% , since tne relative importance of particular pollutants anc so.-ces varies consiceraoly from one place to the next. As mere data become available, these ris < estimates will _^ c : . : t e c 1 y c n a n c e. a s s u c r , tne p o rt rait tne air toxics LAM 003679 DPMC-09770 -i i i problem cepict'eo i r. this study should be regarded as a snapsnct, the fern and substance of which will certainly change as new data become available. Analytical Methods Three major analyses were undertaken to estimate cancer incidence and individual lifetime risks: each analysts included a separate set of compounds, with considerable overlap. The Ambient Air Quality Study used ambient data for five metals, ten organic compounds, and benzo(a)pyrene (BaP) to assess these risks. Two otner analyses--tne NESHAP Study and the 35-County Study--usec emission estimates and exposure models to estimate incidence anc max*, mum inaivioual risxs associated with the pollutants selectee. I" aacitio-n, a "3a? surrogate" approach was used to estimate cance:rcidance associated with products of incomplete combustion (PIC!: a cose-response coefficient relating lung cancer incidence a... - ; C -as generated from epidemiological studies, and cancer incidence assoc'atec witn PIC exposure was estimated by applying tnis o c se res pons e coefficient to current ambient SaP levels. Finally, duantitative risk assessments available from other EPA activities for asoestos, radionuclides, and gasoline marketing were inccr;;-*tec into tne study. Four a d c i t i c '> a ' reports w e - e prepared to assist in f -1 e ' :'-etir.c tr.e results o* the study. One report reviewed nation*: emissions data 'or over ?0 ocmpourcs arc previoee summaries s c - - c a t : e , ccdcraoric location, c r o w t" trends. a - d oata LAM 003680 DPMC-09771 formation of air pollutants, indoor/outdoor relationships for air toxics, and risk estimates used by other program offices within EPA in regulating selected toxic substances. Further, statistics on annual cancer incidence, cancer deaths, and estimates of the cancer cases associated with other causes (e.g., diet, smoking, indoor exposures) were compiled. The study te.am also analyzed and summarized the Information available on several source categories for which current data are insufficient to perform a quantitative risk assessment. Finally, contacts mace witn all 50 state air pollution agencies, 33 local air pollution agencies, the Canadian government, and the Commission of European Communities reveale-d that virtually no other comprehen sive studies a^e available tnat quantify estimated cancer incidence related tc air toxics. Tne study examinee me magnitude and nature of the air toxics problem using existing data and, where possiole, stancarc techniques for quantitative risk assessment. `We did not attempt to evaluate tne valicity of those techniques; rather, we tried to apply mem as comprehensively as possible.- For example, we reliec cr. unit ris< estimates generatea by EP A ' s Carcircuen Assessment 3rou? (C A3; ana by Clement Associates, many of wn*c*. rep-eser.t plausible up^er-oounc estimates of unit risk. T.nese estimates a'so assume 70 years of continuous exposure to cutcocr a-.t'e't levels. However, wrsre appropriate, we point out me LAM 003681 DPMC-09772 possible effects of considering non-traditional approaches, such as examining the- ri sics associated with indoor exposures to air pollutants. Conclusions Given tne scope, limitations, methods, and assumptions dis cussed apove, the following conclusions may be drawn from this study: 1. Both point sources (major industrial sources) and area sources (smaller sources that may be widespread across a given area, such as solvent usage and motor vehicles) appear to contribute significantly to the air toxics problem. Large point sources are associated witn many hign individual risks, while area sources appear to be responsible for the majority of aggregate cancer incicence. 2. wn::e there is considerable uncertainty associated witn tne rise estimates for some substances, available data indicated tnat the following pollutants may be important contributors to aggregate cancer incidence from air toxics: metals, especially chromium and arsenic; asbestos; products of incomplete combustion; forma 1cehyo5; benzene; ethylene oxide; gasoline vapors: and cnlorinatec organic compounds, such as chloroform; carton tetrachloride; perchloroethylene;'tricnloroetnylene; and vinylidene chloride. 2. A wioe variety of sources contributes to incividual ris< ana aggregate incicence from air toxics. 7-nese include: road vehicles; combustion of coal anc oil; wooostoves; metallurgical industries; chemical produc tion anc na nufactur i ng ; gasoline ma r k et i ng ; ' s o 1 v e r.t usage; ano waste oil disposal. As a broad category cf activities, conbustion/incineration is probably tne largest single source of risk. For tnose cities with sufficient data for analysis, lance city- co-city and reicnbornooc-co-neigrtor"ccd va.-;at::n :n pollutant levels ar.c sources was 'curo. -twe.e*, ou" current air toxics cat a base is ir. aceo.ata c: act.race!y characterize most local air tex'ts p - :: ' e ~ s . "--ee a-a'yses cuanti':ec estimated cancer r : $ <: s c _ a t: ! z t : - : toxic a : r p c 1 : t a n c s ; t r. e n u m b e < 3 * p t ' ' - t a " t s LAM 003682 DPMC-09773 examinee varied with the different analyses). Tne estimates from these analyses showed a range of 5 to 7.4 cases of cancer per million people per year (1 ,3 0 C "to 1,700 cases annually nationwide) for the pollu tants examined. These are not actual predictions of incidence, Put are instead a statistical way to represent the potential health effects of human exposure to airborne carcinogens. The reader is reminded that these estimates are highly uncertain, and is cautioned that the conver gence of the various analyses on a seemingly narrow range (5 to 7.4 cases per million) is somewhat coinci dental, given that estimates for individua1compounds varied widely, among the different analyses. For perspective, estimated nationwide cancer cases and cancer deaths for 1983 were 850,000 and 440,000, respectively. Maximum lifetime individual risks of 1 0" 4 (1 in 10,000) or greater in tne vicinity of major point sources were estimated for 21 pollutants, about naif of these tnat we^e studiec. Maximum lifetime individual risks of 10-3 ; 1 in 1,000,' or greater were estimated for i3 pollutants. Accitive lifetime individual risks in uroan areas c : to simultaneous exposure to 10 to 15 pollutants ranges from 1u ~ 3 to 1 0*4 . These risks, which were calculates from monitoring data, die not appear to be relates to specific point sources. Instead, they represent a portion of tne total risks associated witn tne complex pollutant mixtures typical of urpan ambi'ent air. Some low-procuction organic cnemicals appeared to contribute little to aggregate incidence: Z1 organic chemicals were estimatec to account for a total of less tna.o 1.0 cancer cases per year nationwide, however, t-nis conclusion may be due in part to tne lac* of data concerning the emissions and toxicity of t" a s e "exotic" cnemicals. Some of tr.ese Iow-preducticn compouncs did as pea* to be associated with nigh incivid u a 1 r i s '< S . For exam:1e, t"e maximum ; f et ime i nc i / i cu a' rise for i ,4 ,-metr.>* =*e c i a r. i 1 i n e as estimatec at 1.5 X 1C* - . - ,, C j ~ C ; Cctec t r a t "nen-tracit ' 0 n a I " s c u r c e s c * c * " -Ca'CS'-S-C* S pu- ' Z / 3w igQ *C * S * ,, i": s:c"i^s imz c*s;csc* LAM 003683 DPMC-0977 4 -vi i- facilities (TSDF's)--may pose inportent risks in some locations. For instance, preliminary findings suggest tnat POTW's witn industrial indirect dis charges nay emit volatile organic compounds in excess of 100 k kg/y r. Individual lifetime risks for a single compound at one TSDF were estimated as high as 10*=. EPA's criteria pollutant programs appear to have done more to reduce air toxics levels than have regulatory actions aimed at specific toxic compounds. An analysis of 16 pollutants was completed using both monitoring and emission data in oraer to evaluate progress made on air toxics between 1970 and 1980. The estimated cancer inci dence rate for these air pollutants in 1980 was less than half that for 1970, i.e., 6.8 per million per year i 1980, compared to 17.5 per million in 1S70. This seems reasonable considering the diverse array of air toxics sources, the mu 11ipo11utant nature of the problem, ano tne relative intensity of EPA's criteria and air toxics prog rans. Ever, after regulations are implemented under Section 112 of tne Clean Air Act for benzene ano arsenic, these polljtants still appear to make significant contribution to aggregate incidence due to air toxics. Tnis seems to demonstrate tnat the base for tne air toxics reg ; sub programs neeas to be broadened to include emissions from small area sources, such as combustion, road vehicles, and s o 1 v e nt use. Ki-or weaknesses ano gaps characterize air.toxics cata oases at tne federal, state, and local levels. The few air toxics emission inventories available generally snow inconsistencies and anomalies, the air quality cata available are often inadequate to develop population exposure estimates, and few compounds have been tested aoeouately for nealtn effects. The cata limitations preclude performing specific comprehensive risk assess-:* for most urban areas, for many compounds, a'-*.o fc* man., potentially large sources of air toxics r(s'<s ;suc* as i ncineraticn, hazardous waste disposal, <nccor expos.*es. atmospheric :ransformation , and Superfunc sites). r * p r t c i rt v assumptions an: extrapolations are necessary tc t*a*s't*- ' nt o ex:os-*e e s: - a: a LAM 003684 DPMC-09775 line oner $ucn assumptions introduce a high or low Dias into the results i-s Difficult to assess. However, it is clear that the use of such assumptions injects a consideraole degree of uncertainty into tr.e analyses. Some of tne factors which may have led the analyses to under state the risx of cancer related to air toxics are as follows: 1. Urban ancient air is charact eri zed by the presence of cozens, pernaps hundreds of substances. Risk estimates for most of these could not be calculated due to data 1 imitations. 2. Indoor coneentrations of certain pollutants (e.g., radon, tooaccc s n o x e , formaldehyde, and other volatile organic compounds) are commonly several times nigher than out door concentrations. Tne estimated cancer incicence associated :: i indoor exposures to passive snoxing to 5,jUC annually'), raoon (1,000 to 20,000 annually), ano w :to 2--nou r personal exposures to 5 organic co.mpo--.ds ' 1 , = T- 3 anrjally) in.cicate tnat i ncoor sources make an imp O'tant contricutic" to a:r toxics risks. Aisxs cue to compounds formed in the atmosphere coulc not be quantified in tne analyses using exposure mode's, o-t tr.ere are indications that these r i s k s may De significant. "or example, formalaenyde .is formed in t'e a t m o s p r. ere sy the Dreakcown of other organic compounds, and some ccmpouncs (e.g., toluene) may be convertec i-:c toxic substances tnrougn protocnemical reactions. nltnoucn it nas been shown that certain combinations of exposures may nave synergistic effects (for insta-ce. smcxinc arc asbestos exposure), all risxs were assu~e: tc be accitive. 'cctcrs'wr-cn ny ^jve o a y s e c tne ana.ysis to overestimate :a-cer r : s x s associated witn air toxics are as fellows: w c r-- a. f* ^> * V r:s x v a lues were octal nec from * A' s Z c -Ci c c e r. Assessment Group (CAG( a r.c C1 erne nt Z c s:c; r.es . 5 A unit ris x values a r s general 1y - . c - C r C cS c l a u s : b 1 e , u p o s ' - bcunc a c inates. c - - c * : - s < s are -:: 1i< e 1 y z Z 2 e nicner, ' z - Z - c Z Z - s d e ' a o 1 y '*we-. In l r v casss LAM 003685 DPMC-09776 -i x- 2. The weignt of evidence of carcinogenicity for the compounds examined varies greatly, from very limited to very substantial. Furtner, the extent of evaluation and health review performed varies considerably among compounds. For this report, a conservative scenario (i.e., that all compounds included in the report are human carcinogens) was assumed. 3. The risk assessments assume that people living in an area are exposed to the estimated ambient levels for 70 years, 2i nours a day. This especially compromises estimates of maximum lifetime individual risk. Few plants operate for 70 years, most people change their homes s e v er a 1- t i me s during their lives, and they also leave their ne i ghborhoods during the day. -. The degree to which outdoor emissions of many pollutants (e.g., trace metals) penetrate indoors is largely unknown. If emissions of a pollutant from outdoor sources do not penetrate completely indoors and if there are no i ncoor sources of that pollutant, then we will na.-e over-stated risxs, since we have assumed constant exposure to levels equalling those of outdoor ai1". L. A:t r o ug n certain corpinations of exposures may have antagonistic effects, all risks were assumed to be a c o 11 i v e. Cur-ert .Activif.es T.nis study was completed a nc a draft was sent by tne Agent,. on rough peer review late in 1934. Simultaneously, based on one preliminary f i r,c i r.g s of one analyses, E ? A initiated a se-ies c f activities c a s ; c n e a to examine one need for a new national strata:,. 'or air toxics. 7 r e s e i n eluded: formation :* a" Agency-wide Air Toxics Group to fell,: up on t_e study anc to guide tne development of a-,, needed era- g e s ; r national stnatecy. y t : a ' studies to examine : ility of the most important r s < c f t'-e current or Gurams re c a:a ' LAM 003686 DFMC-09777 -X- 3. Discussions of the results of the study ana possible new national strategies with all interested groups, including industry, public interest organizations, '-state and local governments, and legislative staffs. Althougn these activities will not be completed until mid-1935, EPA is beginning to explore several changes to its program for air toxics. The focus of direct federal regulation is snifting from an empnasis on isolated large point sources to more complex situations, that nave greater potential for high national incidence of cancer. Generally, this will mean increased emphasis on area sources ana those point sources t.nat emit several potentially t : x - : ; : 1 u: a r t s. In addition, several new activities are being ct'i'.Cc'eo tnat -ill .rcr.ce for a more comprehensive nation a' : r ; . r a n. " r e s e i r c 1 u c e a federal p c r z n e r s h i p witn s t c Z e and `.oca': agencies tc av a i u at e and, if r.ec essary , regu ni --- C- a 1 arz e poi't sources witn emp nasi s on recu ct i on of ni gh i nc i V 1 dual ns< situations, a-.o an examination of problems caused by concer.trati cns of c.'ces i ; i i n cities or industrial regions. LAW 003687 DPMC -097 VP