Document 10jpnemXxwMzGkVjNpEwd0aqj

Environmental Exposureto Benzene: ~n Update ,awe Wallace 3 . S . Environmental Protection Agency, Reston, Virginia In of bat ems tgoc :nobio& ds). Saa the morq t e s fi4harmad hence of :patocgm ate Chcm .- - -g the 199Os, several large-scale studies of benzene concentrations in air, food, and blood % , 5 added to our knowledge of its environmental occurrence. In general, the new studies have :.-- :med the earlier findings of the U.S. Environmental Protection Agency Total Exposure -.::----sment Methodology (TEAM) studies and other large-scale studies in Germany and the .I- .!andsconcerning the levels of exposure and major sources. For example, the new studies ... - :hat personal exposures exceeded indoor concentrations of benzene, which in turn ~I ; r z ~ e doutdoor concentrations. The new studies of food concentrations have confirmed earlier 3 z a o n s that food is not an important pathway for benzene exposure. The results of the .z: ;rial Health and Nutrition Examination Survey on blood levels in a nationwide sample of 883 --;.-sms are in good agreement with the concentrations in exhaled breath measured in about 800 :yscns a decade earlier in the TEAM studies. Major sources of exposure continue to be active 5 - 2 cassive smoking, auto exhaust, and driving or riding in automobiles. New methods in breath :-3 ziood sampling and analysis offer opportunities to investigate short-term peak exposures and +s. :ng body burden under almost any conceivable field conditions.- Environ Health Perspect 11 S.ppl6):1129-1136(1996) ' e . xds: benzene, exposure, indoor air, outdoor air, personal monitors, TEAM study, body :--zsn, breath, blood f chemid (1994). c mesen- i with dif1):29-32 )n of bentmmatoty ylation d eroxib e-induad 1991). benzene ryn*nre"T= yl-s-(25f be- Bioi F a nith m: crow& L60 a% *atov I failu- Aolecu[a oimmur* j (1991) ,poun& Ndulrio ]dent e 178-1M Introduction '.:uc h of our knowledge of nonoccupational ':-( \ure to benzene was supplied through- - ie 1980s by the U.S. Environmental ction Agency (U.S. EPA) Total ~ 1. m e Assessment Methodology (TEAM) .-ifies of volatile organic compounds . ( K s ) (I).These studies employed per- ml air quality monitors to measure direct -;.:Tonal exposures of approximately 800 --:Tons in about eight areas in the United ' ~ - 2 jbetween 1980 and 1987 (2-13).The ---- :pants were selected on a strict proba- sampling basis to represent about I Saper was presented at Benzene '95: :-llernational Conference on the Toxicity, : -agenesis, and Epidemiology of Benzene held -:3 June 1995 in Piscataway, N e w Jersey. = ^ .script received 16 January 1996; manuscript -:.- 'Ed 14 June 1996. research described in this article has been in part by the U.S. Environmental Protection I. under contract 6&024544 to the Research Institute. It has been subjected to US. EPA ~ '. and approved for publication. Mention of trade 3 or commercial products does not constitute -ement or recommendationfor use - -3ress correspondence to L Wallace, U S EPA. - 3 Woodhollow Court. Reston VA 20191 - - "one (703) 341-7509 Fax (703) 341-7575 . Jemvliaatcioenslanucsee@d eNpHaAmNaEileSp,aNgaotivonal Health and Jn Examination Survey. TEAM. Total Exposure Tent Methodology 800,000 persons in these areas. Measurements of indoor and outdoor air, drinking water, and exhaled breath were made to supplement the personal air measurements. In a pilot study (2,14),measurements were also made in food and beverages; since few VOCs and no benzene was detected, those measurements were not repeated in the main study. The basic results of the TEAM study as they apply to benzene may be summarized as follows (15-20): Benzene was not found, or was found in insignificant amounts, in water, food, and beverages. More than 99% of the total personal exposure was through air. Mean personal air exposures exceeded indoor air concentrations, which in turn exceeded outdoor air concentrations. A global average personal exposure was about 15 pg/m3 (range 7-29 pg/m3). Indoor concentrations were measured only in the 1987 TEhM studies in Los Angeles, CA, Baltimore, MD, and Bayonne, NJ, and appeared to be on the order of 10 pg/m3. Outdoor concentra- tions had a global average of 6 pg/m3 (range 3-19 pg/m3). No effect on personal exposure of living close to major fixed sources of benzene (oil refineries, storage tanks, chemical plants) could be detected in Beaumont. TX (2,3);Bayonne and Elizabeth, NJ (5-8);or Los Angeles, Antioch, and Pittsburg, CA (9-11). The overwhelming source of benzene exposure for smokers was mainstream cigarette smoke (15).Smokers had an average benzene body burden about 6 to 10 times that of nonsmokers, and received about 90% of their benzene exposure from smoking (Figure 1). Roughly half the total benzene exposure in the United States was borne by smokers. For nonsmokers, most benzene exposure ultimately is derived from auto exhaust or gasoline vapor emissions. This includes most of the benzene exposure due to outdoor air, indoor exposures due to intrusion of evaporative gasoline fumes from attached garages (21),and personal activities such as driving (Figure 2). A ponion of the exposure is due to environmental tobacco smoke (15).A small portion (about 6%) of the exposure is due to major point sources of benzene, such as petrochemical plants or refineries. Two large-scale European studies (22,23)confirmed the TEAM study results for indoor and outdoor benzene concentrations. The study in Germany (23) also confirmed the effect of environmental tobacco smoke, finding an increase of 4.5 pg/m3 in homes with smokers compared to the TEAM study finding of an increase of 3.5 pg/m3. Both results were based on about 200 homes with smokers and 300 homes without smokers. Recent Studies About half-a-dozen large-scale studies of personal or indoor air levels of benzene Smoking Figure 1. Sources of benzene exposure: smokers. A typical smoker takes in roughly 2 mg benzeneiday; about 1.8 mg is delivered by mainstream smoke 155 vg/cigarette x 32 cigarettes per day). Source:U.S. EPA TEAM studies. Environmental Health Perrpectives Vol 104, Supplement6 = December I996 I129 L. WALLACE Drivin-grac ETS Figure 2. Sources of benzene exposure: nonsmokers. A typical nonsmoker inhales about 0.2 mg benzene/day. assuming an average exposure of 15 pg/m3 and an alveolar respiration rate of 14 m3/day. Outdoor air contributes about 40% of that amount, assuming an average outdoor level of 6 pg/m3. The remaining 9 pg/m3 are split between driving (100 min at 30-40 pg/m3). indoor sources such as automobile vapor emissions in attached garages or storage of gasoline or kerosene in the garage or the basement, and environmental tobacco-smoke exposures at home or at work. Source: US. EPA TEAM studies. have been conducted since 1990. They are briefly described below. Persona lkposure studies A 1991 study (24)took place in 128 homes in Woodland, California, a community in a largely agricultural region. Personal, indoor, and outdoor benzene concentrations were measured using both Tenax (EnkaResearch Institute, Arnhem, the Netherlands) and evacuated canister samplers. Good agreement was noted between the side-by-side Tenax and canisters. Mean concentrations were 5.0, 4.0, and 1.2 pg/m3 for the personal, indoor, and outdoor samples. Day and night 12-hr average concentrations of benzene were measured for 58 residents of Valdez, Alaska (25).The mean benzene Concentrations in the personal, indoor, and outdoor samples were 20, 16, and 5 pg/m3 during the summer, and 28, 25, and 11 pg/m3 during the winter, respectively. Personal exposures to benzene were measured over a 3-hr period in the evening for 49 nonsmoking females in Columbus, Ohio (26).The median value in 25 homes wi-th a smoker was 4.0 pg/m3 compared to 2.4 pg/m3 in 24 homes without smokers. The difference was statistically significant. Personal exposures to benzene as measured in the TEAM studies and in the Valdez and Woodland studies are summarized in Table 1. Outdoor and indoor benzene values in the TEAM, Valdez, and Woodland studies are summarized in Tables 2 and 3. IndoorAir Studies A nationwide Canadian study (27)measured 24-hr indoor air concentrations of benzene in 754 randomly selected homes. Benzene mean indoor concenrratii :\ were 6.39, 5.60, 2.72, and 6.98 pg/m- .:, the winter, spring, summer, and ti:. seasons, respectively. Indoor and outdoor 48-hr average CC~;.. centrations of benzene were measurel' 2: 161 homes throughout much of Calif[ :::- (28).The Pro-Tek charcoal badges :. merly manufactured by E.I. d u I :,. (Newark, DE) were used. Indoor n-.L:: concentrations were 8.3 pg/m3 cornpd;rL ro 6.1 pg/m3 ourdoors. Seventeen volunteers in Windj >- Canada, wore 3-stage adsorbent tubes pumps in three microenvironments: home, at work, and during commt!:.-(29).Benzene concentrations were 3.5 ?.-. and 15.7 pg/m3 in these three locz .I:.. during summer 1991 and 2.7, 2.7. 2 : ~ 15.1 pg/m3 during winter 1992. Ourdoir levels near homes were 3.8 and 2.0 ug ;r during summer and winter, respectivciy. .L later study (summer 1992) considered \A:,. ous microenvironments. Benzene IC\ :. averaged 2.2 pg/m3 in homes of 36 2~::: matics, 4.6 pg/m3 in 13 samples from :'<:'- rooms, 6.0 pg/m3 in 17 samples co' -::: during commuting, 20.8 pg/m3 in 3 ples from four bingo halls, and 34.5 p ; 7 in two taverns. Brown and Crump (30)reported or. study of 173 homes in Avon, En+:: Passive Tenax tubes (Perkin-Elmer)c011:z: Table 1. Personal air concentrations (pg/m3)of benzene measured in the TEAM, Valdez. and Woodland studies. Household, Site estimated no. Year, season Time n Geom Mean SE mean 25 Percentile 50 75 go 95*.'! NJ1 130,000 1981, fall Day Night 340 347 NJ3 Unweighted data 1983, winter Day -Night 47 49 GNC 130,000 1982, spring Day Night 24 24 A-P 91.000 1984, spring Day 67 Night 69 LA1 360,000 1984, winter Day 112 LA2 330,000 1984, summer Night Day 112 50 Night 50 LA3 Unweighted data 1987, winter Day 33 Night 32 LA4 Unweighted data 1987, summer Day 40 26.2 2 29.7 5 21.o 2 16.6 1 7.9 2 10.2 2 8.5 1 6.5 1 19.1 2 16.5 1 10.5 2 7.8 1 21.6 6 13.6 2 13.7 3 11 7 17 32 65 87 I- 13 7 15 32 54 73 i 16 9 16 26 46 62 f- 13 8 12 -9 14 24 8 13 29 32 - -- - 12 16 - - - 7 5 6 11 17 2' ; 5 2 4 -8 16 :: 15 10 15 23 35 E. 14 11 15 21 30 3- 7 3 7 12 25 3: .- 5 2 4 9 25 zF 13 7 13 221 40 135 ' . 10 6 12 19 22 32 1 9 5 7 13 26 81 . BAL 70.000 VAL Unweighted data VAL Unweighteddata WDL 30,000 1987, spring 1990, summer 1991, winter 1990, spring Night Day Night Day Night Day Night 24 hr 40 70 70 55 58 56 58 93 7.1 1 16.4 2 20.0 3 25.4 5 15.5 3 34.4 6 23.6 4 5.0 1 5 9 -4 58 11 22 16 2: 32 SF 12 14 - 7 14 24 13 23 42 2 : 70 .: 9 5 9 20 30 21 13 20 37 90 ... - . 13 3 7 2 12 26 35 65 I:! 9 - / Abbreviations: n, number; SE, standard error; geom mean, geometric mean. NJ1, Bayonne-Elizabeth, NJ; NJ3, Bayonne-Elizabeth. NJ; GNC, Greensbor: .'*: Antioch-Pittsburg, CA; LA1, Los Angeles. CA; LA2. Los Angeles. CA; LA3, Los Angeles, CA; LA4, Los Angeles. CA; BAL, Baltimore, MD (Dundalk); VAL, Valdez -' " Woodland, CA. 1130 Environmental Health Perspectives = Vol 104. Supplement 6 9 December 1996 ENVIRONMENTAL EXPOSURE TO BENZENE: AN UPDATE Table2. dousehold-weightedoutdoor air concentrations(vg/m3) Geom Mean SE mean 25 _ _ I'twuntile 50 15 90 3 IASX Unweighted data 1983, winter Night 84 8 1. 1' , :- ,:- ,,,LcL Unweighted data Unweighted data Unweighted data Unweighted data 10,000 1984. winter 1984, summer 1987,winter 1987, summer 1990. summer 1991, winter 1990, spnng Night Day Night Day Night Day Night Day Night Day Night 24 hr 24 24 24 23 41 46 38 40 30 28 29 28 48 9 5 0 9 3 8 1 2 7 8 IG 20 86 1 4 1 2 2 6 7 11 15 39 08 - 43 07 - 2 4 54 73 26 45 55 79 0 9 13 16 63 18 03 16 14 17 19 32 13 1 3 11 8 1 14 18 21 19 1 9 16 11 19 25 32 42 08 32 2 31 48 87 31 04 26 17 25 44 58 47 05 38 26 38 62 87 96 1 6.7 3.6 7 8 15 19 34 04 28 19 2G 48 66 4 05 32 2 33 45 9 4.8 0 4 4 1 3 57 8 5 1 3 6 2 5 7 10 15 3 4 10 7 11 15 27 84 09 12 09 75 11 . 08 8 12 15 11 14 19 -'-,","'"'cilations 0.number. SE. standard enor: geom mean. geometric mean. NJ1, Bayonne-Elizabeth. NJ, NJ3, Bayonne-Elizabeth, N.1 A 1'. Antioch-Pittsburg, 3 LA1 '-0s :"Ws. CA. w.Los Angeles. CA. M3.Los Angeles, CA, LA4. Los Angeles, CA, VAL, Valdez, AK. WDL. Woodland, CA T-able 3. Indoor air concentrations(vg/m3). ;';? Households, no. -X Unweighteddata -A: Unweighted data !J- i i ,VEL Unweighted data Unweighteddata 10.000 Year, season 1987, winter 1987, summer 1990, summer 1991,winter 1990, spring Time Day Day Night Day Day Night Day Night Day Night 24 hr Room LR Kit Kit LR Kit Kit LR LR LR LR LA n 36 38 36 40 38 37 30 30 29 27 104 Mean 9.9 11 15 6.5 5.5 6.5 13 18 26 24 4.7 SE 1.4 2.6 2.2 0.9 0.8 1.2 4 5.2 4.4 4.fi 1.1 Geom mean 7.3 6.5 9.7 4.9 4.4 4.4 8.1 7.6 17 14 2.5 l'.ercentile 25 50 75 90 5 ' h x 4.2 7.1 13 19 3 3.7 7!1 12 21 32 37 5 11 18 40 43 53 -2.8 1 fi 9.4 15 -77- 23 2.5 1.1 6.7 9.9 - 4 23 2.3 a ! r 7.4 13 -: 3 4 f1 14 19 -I ^ 36 4 IJ 22 29 -23 '23 7 1fi 34 62 ? 36 -7 16 28 74 '2 1.3 2.2 5.1 8.3 - 33 30 WevlatiOnS: 0, number; SE.standard error; geom mean, geometric mean; LR, living room; kit, kitchen. LA, LOSAngeles, CA; VAL, Valiloz, AK; WDL. Woodland. 2 i JS-day samples in the living room and m i n bedroom of the home for 1 year. TI- -teen sets of 12-month outdoor sam- pi, were also collected over the course of [hi btudy (November 1990-February 1')')3). T h e mean indoor concentration \\as 8 pg/m3 (n=3000 samples) compared 10 .in outdoor mean of 5 pg/m3 ( n =125). Ambient Concentrations k z e n e concentrations were reported for 5 ) 1 ambient air samples collected from 10 ( iddian cities (T Dann, unpublished IJ T h e overall mean was 4.4 pg/m3, \I 1 11 Ottawa and Montreal ranging between 5 1 and 7.6 pg/m3. A more recent survey tt Dann and D Wang, unpublished data) found similar levels, with three rural sites r.1nging from 0.6 to 1.2 pg/m3. Twen ty-four- hour average benzene L .Is have been measured every 12th day at about 20 sites throughout California since 1986 (31).Statewide average annual values fluctuated between 5 and 7 pg/m3 until 1993 and 1994, when they dropped to about 4 pg/m3 (Figure 3). This decline appears to be red and may be due to one or more of several factors: a) the 50% reduction in hydrocarbon emissions man- dated for new cars; b ) the Stage I1 vapor recovery controls recently in effect; c) a reduction in benzene content in gasoline down to the 1% mandated in the 1990 Clean Air Act Amendments. The California database also allows analysis of seasonal variation. A clear sinusoidal curve is apparent, with winter values about twice summer values (Figure 4).This may be due to changes in the blend of the gasoline toward greater volatility in the winter or to increased likelihood of inversions during the winter. The m c : ; ~pe~rsonal, indoor, S ourdoor values of bcnzene measured in 3 e s e more recent studies are compared in T s i e 'i. In-Vehide studies T h e largest study of in-vehicle iYenzene exposure continues to be the ZOO-T~F s x d y (32)of Los Angeles in the sunliner and cwominmteurtesress..;=Itilsi.ied--.a2u1.st study found an average benzene q o s u = e of 13 ppb (40 pg/m3) for commuET durrng rush hour, on che order of 5 time: ;?e con- centration measured at a fixed o&oor s% A small study in North C a r r l k a 33) also showed in-vehicle concenmxzhns 3 70 8 times background ambient l e e i s . -4 sscond small study in Boston (34)rcsdre;l in passenger levels 1.5 times roac%a!- :e..-& on an interstate highway. More recently, a study (351 k''2e-?;r-?e ievels in two-passenger vehiclrs i . ~ z i 3 ~ I Environmental Health Perspectives = Vol 104, Supplement 6 = December I996 L. WALLACE .- 1lo 8 .6 0 E 2 4 2 n 1986 1987 1988 1989 1990 1991 1992 1993 1994 Annual California benzene averages across all sites Figure 3. Ambient benzene in California, annual averages across all sites 19861994, Annual average outdoor benzene concentrations at about 20 sites in California. At each site. a 24-hr average is raken every 12 days. The decline in 1993 to 1994 may be due to reduced emissions from automobiles. Source: California Air Resources Board, data from 2Ot cities. 14 1 i l 12 1986-1991 10 .0 8 E 26 4 2 0 Jan Feb Mar Apr May June July Aug Sept OCI Nav Dec California benzene monthly averages Figure 4. California benzene monthly averages. Seasonal variation in outdoor benzene at about 20 sites in California. Higher values in winter may be due :o seasonally varying gasoline formulations, and perhaps to increased frequency of atmospheric inversions. The decline in benzene concentrations over the past few years is consistent over all seasons. Source: California Air Resources Board, data from all (about 20) sites. Table 4. Mean benzene concentrations (pg/m3) reported in recent studies. Reference Goldstein et al , 1992 (25) Sheldon et al , 1991 (24) Heavner et a1 , 1994 (26) Brown and Crump 1996 (30) Wilson et at, 1993 (28) Fellin and Otson. 1993 (27) Dann (unpublished data) CARB 1989-1992(37) CARB 1993-1994 (37) Location Alaska California Ohio England California Canada Canada California California n Personal 112 24 120 5 0 49 3 2 173 161 154 586 3000 1000 Indoor 20 40 8 83 54 Outdoor 8 1 5 6 4 7 4 typical commutes in the New Jerse!-York area resulted in measured e x p , of 9 to 12 pg/m3 in suburban and tuii conditions, and 26 pg1m3 in the I in,, . Tunnel. The author stated that rhe cor trations during the commutes to Sr\: .. City were about 10 times thc .&n:. background concencration meclct!:, same day in suburban New Jerse! . Unfortunately, none of the >:,. . measured the benzene concentration I: ::,. gasoline used, so it is not possible ro i::::. mine whether the lower concentratio?. the later studies might be due to ' amounts of benzene in gasoline. Gasoline Spill Study A study of exposure to benzrni . showering with gasoline-contan;. . .. groundwater ( 3 6 )was carried O C : . ., home in North Carolina. T h e FrC,..: water had a measured benzene coni tion of 292 pglliter, well above t h c : EPA's Maximum Contaminanr Lr\<': . ..pg/liter. Three 20-min showers on .. utive days resulted in peak shov .. concentrations of 800 to 16-( Bathroom concentrations reachci . 500 pg/m3, and concentration, , . . . remainder of the house peaked ((1. :-. . later) at 40 to 140 pg/m3. The i n h ' dose during the 20-min shouer 7 from 80 to 100 pg. A dermal dose of 0' -_ was also calculated, using measuret 5:. concenrrations. The combine; - .. about 250 pg from the 20-mir. . . roughly equal to the mean :.; i n h a h i o n dose of about 200 L nonsmokers in the TEAM study I 15 pg/m3 x 14 m3/day alveolar insp . Body Burden Benzene in the blood of 883 per.cr- '.',measured (37)as part of the c' I - Health and Nutrition Examinari' ...- - .(NHANES 111).These blood . .. .. tions were compared with rhr (1. centrations measured in about - - - . in the TEAM studies of the 19h". ' ' the TEAM study measurements \\ c y . .. using mixed breath, the breath multiplied by 1017 to accounr f space estimated at 30%) of thc \ an inhaled breath. Theoreticall>. expect that if the two popularici. parable, the ratio of blood r o . ... .' .- concentrations for corrrspr I . centiles should remain con\:.-: . magnitude of the blood/air parti:!,,' - cient for benzene, for which st' mares ranging between 7 and 1 t i :' . - I132 Environmental Health Perspectives 9 Vol 104. Supplement 6 = December I996 EWRONMENTAL EXPOSURETO BENZENE: AN UPDATE 5ey-N- XPOSU~ turnpk Lincob !Con- kw Yo& ambient wed the studim Jn in & to deter- ations in to lower ie while minated out in a ground incentra- he U.S. eve1 of 5 I consecMer-stall pg/m3. 1 3 7 0 to s in the 3.5-1 hr ihalation . ranged )f 160 pg .d breath dose of hower is a1 daily g for all muming iiration). sons was Jational n Surv~y ncentraath conI persons 1s. Since :re made ues were r a dead llume of le might are comeolar air ng pert a t the In coeffi:raI estiave been Table 5. Breath and blood concentrations and --.--_------.' r:eath ;;udy ratios at selected percentiles from all sites ( n= 800) and from the NHANES Ill -;:.:: 311 In= 883). -c -~..-.---. -e ..--.--.- Breath. ng/liter 0.63 1.1 15.6 Blood. ng/liter 15 38 166 Blood/breath ratio 24 35 10.6 .-. 33.7 324 .I... 58.4 477 _-.- 101 807 9.6 8.2 8.0 . r.. I . _ . ^^ 3. _ -. .-. I _ . _ , t. 5.6 13.1 330 61 131 1880 11 10 5.7 :,xx. However, the actual observed ratio of ,bod to alveolar air concentrations appears :a decrease with increasing concentrations, +om 24 and 33 at the 16th and 25th per;stiles through a range of 11 to 8 at profressively higher percentiles (Table 5). This js similar to the observation (38) of a +od/breath ratio of about 20138 for an xczposed population of nonsmoking .~rsc's,while the ratio for an occupationAil.- csposed cohort of smokers was about Both these findings may be explained r'p [he possibility suggested by Travis mi Bowers (39) that at low concentra-ions, a saturable blood component (e.g., :rereins) binds a limited amount of benx-c'. making it unavailable for distribution YP-jughout the body or elimination in brL.ich.Travis and Bowers estimated the apJcity of the blood proteins to be 90 I:liter, based o n the observations of Perbellini et al. (38). They also estimated +e plasma partition coefficient to be 9.0. idding the NHANES/TEAM data to those of Perbellini et al. and adjusting the Txvis/Bowers model to fit a l l the data, one .ir ves at a lower estimate of blood capacity of 10 ngjliter, and a slightly lower plasma p x m o n coefficient of 8 (Figure 5). Concentrations in Food There were reports in the 1970s of benzene h n g found at ppm levels in some foods \ush as eggs (40). However, in a special 1CJdv that was part of the TEAM pilot ' 7id? in 1980, breath measurements before :;1After eating eggs showed no increase in rizene. Also. no effect on benzene levels 1- breath from eating eggs or any other rood item could be discerned from regres,ions on all participants in the main TEAM w d y , using the participants' responses to a Axailed auestionnaire on food intake. It is ussible that minor levels of benzene in I&tuffs could still have been present and H 340 0 20 40 60 80 100 Alveolar air, ng/liter Figure 5. The upper curve is a model by Travis and Bowers (39)f i t t e d t o venous blood/alveolar air (C,,,,/C,,,] ratios observed by Perbellini et al. (38).The model assumes that some benzene is bound by proteins in the blood, w i t h a maximum capacity of 90 ng/liter. The lower curve is an adjusted model to fit both Perbellini's observations (*a)nd the bloodlbreath ratios (m)calculated from corresponding percentiles of the NHANES blood measurements on 883 persons.and the TEAM study breath measurements on about 800 persons. The adjusted model employs a somewhat smaller maximum capacity of 30 ng/liter and a slightly lower estimate of the plasma partition coefficient [8 compared to the value of 9 estimated by Travis and Bowers (3711. not detected in breath due to efficient metabolization by the liver, which receives materials from the gut directly before they enter the blood stream. However, it was thought that major concentrations in food would be detectable in breath; since they were nor, it was concluded that food and beverages were an unimportant pathway for benzene exposure. Two recent studies of benzene levels in foods have confirmed that conclusion by finding negligible quantities in nearly all foods measured. In one study by the U.S. Food and Drug Administration (FDA), more than 50 foods were analyzed for benzene (41).Most of these were under 2 ng/g ppbw (parts per billion by weight) benzene. Exceptions included strawberry preserves (38 nglg), taco sauce (9 and 22 ng/g), duck sauce (7 nglg), and barbecue sauce ( 5 ng/g). The authors speculated that the added benzoates and ascorbates in these foods might react to form benzene; thus, if either one or the other were removed, the benzene might no longer be formed. In a second study (42),57 foods were measured, with only shelled peanuts and fried eggs giving positive results, each at 30 ng/g, again far below the parts per million (ppm) levels previously reported. A recent Canadian review of benzene exposures (43) concluded that food and drinking water each contributed only about 0.02 pg/kg benzene per day compared to a total intake of 2.4 pg/kg per day from airborne exposures (3.3 pg/kg/day if exposed to cigarette smoke). Thus, airborne exposure accounts for 98 to 99% of total benzene intake for Canadian nonsmokers. Discussion The general finding from previous studies that personal exposures to benzene exceed indoor air concentrations, which in turn exceed outdoor air concentrations, has been confirmed by the more recent studies. Two of the three personal monitoring studies mentioned above had somewhat lower mean personal exposures to benzene than had previously been reported. One such study (24)was in a small rural com- munity in California, which also had a lower mean outdoor benzene value (1.2 pg/m3) than has been previously reported. The second study (26)included only 3-hr exposures in the evening at home; to the extent that all other personal exposure studies included time spent in vehicles, where benzene exposures have been shown to range up to 40 pg/m3, such a study limited to the home microenvironment might be expected to produce smaller personal exposures. Therefore, both of these studies would be expected to be at the low end of benzene exposures. O n the other hand, the outdoor concentrations of about 5 pg/m3 in Valdez were similar KO outdoor concentrations in the various TEAM study sites, but the indoor and personal concentrations (20 and 24 pg/m3) were considerably greater than in all TEAM study sites except for Los Angeles in the winter. It may be speculated that persons in frontier-type situations make more use of gasoline-powered instruments such as chain saws, snow blowers, and .snowmobilesthan persons in urban communities. It may also be that the requirements for warming up automobiles for extended periods, and the larger amounts of benzene that are found in Alaskan and Canadian gasoline blends, led to higher exposures from attached garages and driving. Considering that the TEAM Studies showed a range of benzene exposures from 7 to 29 pg/m3 (16),the range observed since 1990 of 3.2 to 24 pglm3 provides no firm evidence as yet for a downward trend in benzene exposures. A second finding from previous studies, chat benzene levels were increased in homes with smokers, was also replicated. The new study (26) found a significant increase of 1.6 pg/m3, which is less than Environmental Health Perspectives 9 Vol 104, Supplement 6 December I996 I133 L. WALLACE the increases of 3.5 and 4.5 pg/m3 found in the TEAM and West German studies (1523) but represents about the same percentage increase of 50 to 67%compared to nonsmoking homes. The Windsor study (29)that found increased benzene concentrations in bingo halls and taverns, where smoking is prevalent, might also be viewed as confirming the effect of smoking on indoor benzene concentrations. Several small studies replicated the findings of an earlier major study in Los ' Angeles that showed increased benzene exposures while driving. The later studies appeared to involve much smaller exposures but also had much smaller outdoor concentrations, so the ratio of personal exposure to outdoor concentration continued to be in the neighborhood of 5 to 10. The smaller concentrations could be due to differences in location (Los Angeles vs North Carolina and New Jersey-New York) but could also reflect reductions in the amount of benzene in the gasoline. The results of the national fuel survey carried out by the American Automobile Manufacturers Association (44)indicate that the goal of 1% benzene in gasoline set by the 1990 Clean Air Act Amendments has been very nearly met, with the average for premium, intermediate, and regular gasoline for the winter of 1994 to 1995 being 0.9, 0.9, and 1.1% by volume, respectively. This is a considerable reduction compared to the 2 to 3% levels that were probably common during the large California in-vehicle study. However, it should also be noted that the amount of benzene in the exhaust may be related only weakly to the amount of benzene in the gasoline. O n e study (45)indicated that exhaust benzene remained unchanged at about 5% of total hydrocarbon emissions whether the gasoline burned contained 1 or 3% benzene by volume. A large number of food groups were tested but found to contain negligible amounts of benzene. This corroborated the conclusions of the TEAM studies, which found no evidence of food contributions to body burden of participants. Although nearly all the studies reviewed here have been more in the nature of confirmatory studies rather than breaking new ground, the study of benzene exposures while showering in gasoline-contaminated water presented new data of considerable value. The 20-min exposure from this source was the same order of magnitude as a full day's exposure to benzene for a typical nonsmoker. However, a smoker (of more than five cigarettes a day) using the same gasoline-contaminated water would still get most of his or her exposure through smoking-an indication of the extensive exposure encountered by some 43 million U.S. citizens. Since the number of persons affected by such spills is very small, the effect on the national exposure budget for benzene is also very small. Apart from these presumably very rare gasoline spill situations, there may be a larger number of cases where well water is contaminated by benzene at low concentrations. A number of studies have reported finding benzene at levels on the order of 5 ng/liter (ppb) in surface and well waters. However, these levels correspond to a daily intake of < 10 ng benzene, assuming 2 liters of water drunk daily. This amount is only 0.5% of the average daily intake for nonsmokers of 200 ng from air. Thus, it is concluded that the effect of contaminated water on total benzene intake is negligible. It may fairly be asked whether any of the differences observed in various studies at different locations and times are dependent on the differenr methods employed. The TEAM studies employed Tenax-GC with active pumping, as did the later Woodland and Valdez studies; thus, all the studies using personal monitors used very similar or identical methods. The indoor air studies in England and Canada employed passive (diffusive) samplers with extended monitoring periods. The English investigators performed a number of tests on the effect of extended sampling on the net uptake of different VOCs by the Perkin-Elmer sorbent tubes containing Tenax-TA. They found that the more volatile VOCs such as benzene and toluene had net diffusive uptakes that declined over time, probably because of back diffusion off the tubes. For sorbent tubes exposed to a concentration of 2500 pg/m3 toluene, the diffusive uptake rate declined to 71% of the ideal after 7 days and 54% after 28 days. For benzene, the net diffusive uptake was 30% after 2 8 days. For the less volatile compounds such as xylenes, decane, and trimethylbenzenes, the sampling rate stayed nearly constant over the 28-day period. Therefore, given a month-long sampling period, an average uptake rare can be chosen for any given chemical; however, for chemicals more volatile than the xylenes, this rate will only be an average value from a declining curve. This means that the early ~ the sampling period for these ~ o ! ~ : , , : compounds may be underreprescn:lL because of back diffusion losses iron: ::,: substrate. However, if the average ,.:.:.. pling rate is correctly chosen, chis \, not cause a bias, only greater vari*;, than exists in fact. The Canadian investigators used , . mercial samplers with a charcoal so (the 3M organic vapor badge), follo\\,L :% solvent desorption using carbon disui!:,.l (CS2). Carbon disulfide is well kno\\!: I have a contamination problem n i r h ,:.j zene; however, the Canadian invesri:;: . developed their own methods for iii- the CS2, and report no serious prc .: with contamination. It is not clear 1'.. :. they used the ideal sampling rare fLl: zene or determined an effective sanii rate for the 1-week sampling period. Both Tenax and charcoal havr pr{,: lems with nonzero background hen. concentrations. The Tenax musr hr \..:_ fully cleaned to avoid such problem. . '.. early TEAM studies had high and T., , . backgrounds of benzene equi;-.i about 5 i 3 pg/m3 on the Tenax cz;:. .... This would lead to decreased prcL:. . although since average background. V.:.. subtracted from each raw datum. it i>.. . clear whether any bias remained. Th TEAM studies reduced backgrounds I( equivalent of about 1i0.5 pg/m3. rcci::: 7 - the uncertainry in the estimated es: considerably. T h e charcoal bac; .. .- . have high backgrounds of benzcr . .. ., ever, the extended sampling perioi :.' have provided sufficient benzene r o :c the background effect. Therefor: .: unlikely that a significant bias or 1~:. precision has affected the personal. i n i , ' . or outdoor air concentrations of b r f i ~ - : The initial breath measuremen:. ... :-. TEAM New Jersey study of 1981 :-. '... Tedlar (Nutech Corp., Durham. ' ....-. stored in a van. Because of rhs ' ' ' that exhaust vapors had pencrr.::;..: ' Tedlar bags, future studies pas\L.k: :. ' helium over the bags at positive prc remove this possible source of cion. Both higher exposures c o n. r an:. :..'r<' - ' 'breath concentrations were noli.: ' period, but about 45% of thc -- participants were smokers io:' -. 22% of the California parricip. . .- the higher breath concenrracion. in the New Jersey participanr> have been due to the higher smok I134 Environmental Health Perspectives Vol 104, Supplement 6 December I996 ENVIRONMENTALEXPOSURE TO BENZENE: AN UPDATE 4 art of latile :nted m the Sam-' would ibility . corn)rbent led by ulfidc wn to 1 ben- gators :aning blems hether r bennpling i probmene cares. The ariable ent to ridges. :ision, s were is not ie later to the ducing iosures :s also ; howshould reduce .e i t is ack of ndoor, zene. in the lployed 3 bags sibility ed the d pure sure to amina- higher in this Jersey ,red to s; thus served 1y well ;rate. ' , ' * I - REFERENCES 1 Wallace LA. The TEAM Study: Summary and Analysis. Vol 1. EPA 600/6-87/002a. NTIS PB 88-100060. Washington:U.S. Environmental Protection Agency, 1987. 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