Environ. Sci. Technol. lQQ4,28, 136-141
Mutagenicity and Chemical Analysis of Emissions from the Open Burning of Scrap Rubber Tires David M. DeMarini'
Genetic Toxicology Dlvision, MD-68A, Health Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 2771 1 Paul M. Lemieux Combustion Research Branch, MD-65, Air and Energy Engineering Research Laboratory, US. Environmental Protection Agency, Research Triangle Park, North Carolina 2771 1 Jeffrey V. Ryan
Acurex Environmental Corporation, P.O. Box 13109, Research Triangle Park, North Carolina 27709 Lance R. Brooks and Ron W. Wlillams Environmental Health Research and Testing, Inc., P.O. Box 12199, Research Triangle Park, North Carolina 27709
Approximately240 million scrap rubber tires (2.2million t) are discarded annually in the United States (I). Of these, - 2 0 % are recycled, either as fuel for cement kilns and utility boilers or as a supplement to asphalt (I, 2). Despite these reclamation efforts, the vast majority (-80%) of scrap rubber tires are discarded in stockpiles or landfills, many of which are illegal. The current stockpile inventory in the United States is estimated to be - 2 billion scrap rubber tires (18 million t) ( I , 2). Many landfills no longer accept scrap tires because of the disposal and health-related problems posed by used tires. After burial, tires often float to the surface and become partially filled with water, which serves as an ideal breeding habitat for many insects, especially mosquitos
(3). In fact, the introduction and spread of several mosquito species in the United Stateshave been attributed directly to the formation of breeding habitats by waterfilled tires in tire stockpiles (3). Although cutting tires in half or shredding them into pieces can reduce the tendency of scrap tires to accumulate water, such processes are costly, and many landfills lack the necessary equipment. Another problem associated with scrap rubber tires is the frequent occurrenceof tire fires at tire stockpiles. These fires, some of which may be started intentionally,generate large amounts of heat and smoke and are difficult to extinguish. This is partly due to the fact that tires, in general, have more heat energy by weight than does coal (37 600 vs 27 200 kJ/kg) (4). Some tire fires have burned continuously for months, such as the 9-month Rhinehart tire fire in Winchester, VA (4). The emissions from such fires affect not only the atmosphere but also the land and groundwater due to the liquifaction of the rubber during the combustion process. Considerable research has been performed on the mutagenic and carcinogenic properties of chemicals associated with the rubber industry (5, 6). These studies have shown that a wide variety of mutagens and carcinogens are present in the rubber industry and that carcinogenic and other types of health effects have been associated with rubber workers (5). Many chemicals, some of which are mutagens and carcinogens, have been identified in the emissions from both the controlled and uncontrolled burning of rubber tires (7,8);however, we are unaware of any studies on the mutagenicity of the emissions produced by the open burning of tires. The organic products of incomplete combustion (PICs) are present in emissions from all combustion processes and, in general, have been found to be carcinogenic in humans and rodents and to be mutagenic in bacteria and mammalian cells (9). Mutagenicity bioassays, especially the Salmonella mutagenicity assay, have been shown to be useful for evaluating the health effects of airborne mutagens and potential carcinogens present in the PICs from a variety of combustion emissions (IO). Such bioassays have been used to characterize PIC-impacted urban air as well as emissions from the combustion of municipal and hazardous waste, polyethyleneplastic, wood smoke, and automotive and diesel exhaust (10-14).
138 Envlron. Scl. Technoi., Vol. 28, No. 1, 1994
0013-936X/94/0928-0136$04.50/0
The Salmonella mutagenicity assay and chemicalanalyses were used to evaluate the emissions from the open burning of scrap rubber tires that had been cut into either of two sizes, CHUNK or SHRED. The mutagenic potencies in strain TA98 of the dichloromethane-extractable particulate organics (2-12 revertants/pg) were generally greater than that of the semivolatiles (- 1-9 revertants/pg). In addition, the open burning of CHUNK tires produced a higher burn rate (-4-9 vs -1 kg/h) and more potent organics in the presence of S9 than did SHRED tires. This may have reflected the greater production of S9-dependent mutagens, such as polycyclic aromatic hydrocarbons (PAHs), under the combustion conditions generated by the CHUNK tires. Bioassays using selected strains of Salmonella indicated that dinitroarenes or aromatic amines (but not mononitroaromatics)accounted for much of the mutagenic activity measured in the absence of S9. A wide variety of PAHs was detected in the particulate organics. The mutagenic emission factor for the open burning of scrap rubber tires (-8 X lo7 revertantdkg of tire burned) was 3-4 orders of magnitude greater than the values for the combustion of oil, coal, or wood in utility boilers; it was most similar to values for the open burning of wood or plastic. These results demonstrate for the first time that the open burning of scrap rubber tires produces a high mutagenic emission factor, posing potential environmental and health effects.
Introduction
0 1993 American Chemical Society
We have used the Salmonella mutagenicity assay to perform bioassay-directed chemical analysis of the emissions from the open burning of scrap rubber tires. We have determined the mutagenic potencies, mutagenic emission factors, and partial chemical composition of the organic PICs emitted from such fires, and we have examined the effect on these parameters of burning tires that have been cut into different sizes and shapes. Materials and Methods
Combustion Conditions. Two independent tire burns were conducted on each of two different sizes of tire material as described previously (8,151. Representative tires from both trucks and cars were obtained from local tire dealers. Because of the difficulty in cutting steelbelted radials, bias ply tires were used for this study. The tires were cut into pieces that were either one-fourth to one-sixth of a tire (CHUNK condition) or 5 X 5 X 3 cm in size (SHRED condition). Small quantities (4.5-9.0 kg) of the tire pieces were then placed in a stainless-steel burn pit (0.4 x 0.4 X 0.4 m) that was insulated with fire brick and mounted on a weigh scale located in a specially designed burn hut (2.4 X 2.4 X 2.4 m). A deflector shield was located 1.2 m over the pit to deflect flames, protect the ceiling of the burn hut, and enhance ambient mixing. Cooled air was delivered continuously to the burn hut at the rate of 34 m3/min. The tire material was ignited with a propane torch, and when combustion became selfsustaining (-5 min), the torch was removed, and the hut door was closed. Sample Collection, Extraction, and Chemical Analysis. The tire fire samples were collected as described (8, 15) by a PMlo ambient sampler containing Teflonimpregnated glass fiber (TIGF) filters (Pallflex, No. T60A20,20.3 X 25.4 cm) that was located in the burn hut. A gaseous sample duct opening was located directly over the deflector shield; it exited the burn hut and entered an adjacent building called the sample shed. Most of the sampling equipment was in the sample shed, including a VOST system, a semivolatile organic collection system containing XAD-2, an airborne metals particulate collection system, and a digital readout for the weigh scale. A heated sample line was connected to the particulate conditioning filter, exited the sample shed, and entered a mobile laboratory that contained equipment that permitted the continuous monitoring of SOZ,0 2 , CO2, CO, and total hydrocarbons. Organicswere recovered from filters and XAD-2by 24-h Soxhlet extractions using dichloromethane (DCM), and the DCM-extractablemass was determined gravimetrically (15). The error in these measurements was 0.95. A composite sample of all of the tire burns was evaluated in strains TA98 (+/-S9), TA98NR (-S9), and TA98/1,8-DNPs ( 4 9 ) . These strains were used to estimate the contribution made by nitroaromatics to the total mutagenic activity observed in the emissions in strain TA98 (-S9). Strains TA98NR and TA98/1,8-DNP6 were used in conjunction with the standard tester strain TA98 because reduced mutagenic activity in the first two strains relative to TA98 indicates the presence of nitroaromatics. This reduced mutagenic activity occurs because strains TA98NR and TA98/1,8-DNP6 are deficient in the nitroreductase and transacetylase enzymes, respectively, which are necessary for the conversion of mono- and dinitroaromatics, respectively, to mutagenic electrophilic arylhydroxylamines (18). Because most nitroaromatics are activated to mutagens by bacterial enzymes, no exogenous metabolic activation in the form of rat liver S9 is required for these strains. In addition, S9 partially inactivates nitroaromatic compounds, complicating the interpretation of the data obtained in the presence of S9 (19). Regressions over the linear part of the dose-response curves were calculated to determine mutagenic potencies (revertants/pg) or mutagenic concentrations (revertants/m3). A microsuspension assay was used as described previously (20)to evaluate the mutagenicity of the HPLC fractions (13, 15, 16). Results and Discussion
Burn Rates. Both CHUNK and SHRED tires produced high initial burn rates; however, CHUNK tires produced a higher burn rate than did the SHRED tires (Figure 1). Thus, nearly twice as much CHUNK tires, compared to SHRED tires, were combusted during the same time period. For both of the SHRED tire burns, the burn pit had to be agitated approximately midway through the test period in order to sustain combustion. This may account for the elevated burn rates that occurred at that Environ. Sci. Technol.. Vol. 28, No. 1. 1994
137
Table 1. Mutagenic Potencies and Mutagenic Emission Factors for Tire Fire in TA98 exp. mndition
1
CHUNK
XAD (revertants per) kgoffuel X I@ MJ ofheat
burnrate tLg/h)
EOM ( % )
S9
~g
9.4
4.5
2.2 1536 1.9 1326
1.I
22.fi
+ +
filter
Natural Gas (kiln) Cardbmrd & %?bent (kiln) Polyethylene(kiln) Toluene (kiln) Polvethvlene/PVC (kiln)
StageDinoseb(boiler) Stage & Reburn h o s e b (boder)
I
n.7
m3
fi22
14.88 12.85
42690 36866
n.17
4R7
ug
filter (revertants per) k o f fuel X I@ MJofheat
m3
12.0 403608 2.3 77358 4.3
29325
873.61 167.44
2 506 381 480 385 1 RR9 255
--
__
.-,
Rev/kg of Fuel x IO5
Rev/M]
Flguro 2. Mutagenic emisabn f a W s of combustion emisalons in strain TA98 (+S9). Data for emissions other man lire burning are from refs 10-14.
point. The levels of emission of CO, SO*,and total hydrocarbons were associated with the bum rates (8.15). Mutagenic Potencies. Table 1shows the mutagenic potencies (revertantalpg) of the DCM-extractable organica based on the slopes of the mutagenicity doseresponse curves (15). The mutagenic potency (revertantdpg) of the semivolatile organics (XAD) was similar for CHUNK and SHRED tires; Le., 1-2 revertantdwg. Theexception was experiment 2 of the SHRED XAD sample, which was considerably more potent, perhaps due to the agitation of the burn pit during this burn in order to sustain combustion. The mutagenic potency (revertantslpg) of the particulateorganica (filter)was generally greater than that of the semivolatile organics, ranging from -2 to 12 revertants/pg. In the presence of S9, the particulate organics from the CHUNK tires exhibited greater mutagenic potency than those from the SHRED tires; whereas, in the absence of S9, the reverse was observed (Table 1). The mutagenicpotenciesoftheparticulateorganica were similar to those obtained from a variety of combustion emissions, although the potencies of the particulate organics from the CHUNK tires in the presence of S9 (-1&12revertanta/pg) were in the upper end of the range of values typically found for combustion emissions (1014,16). The greater mutagenic potencies in the presence of S9 of the particulate organics from CHUNK tires may have heen due to the greater initial burn rate that was achieved with CHUNK tires. A greater burn rate might .have produced more polycyclic aromatic hydrocarbons (PAHs), which are mutagenic, relative to nonmutagenic organics. Many PAHs are mutagenic in the presence of S9; whereas, other components of soot are generally not mutagenic or not as mutagenic as PAHs (9).
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I S 8 Envton. €el.Techol.. Vol. 28.
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Mutagenic Emission Factors. Mutagenic emission factors are a convenient way to characterize mutagenic potency in terms of fuel consumed or heat produced by a combustion process. Mutagenic emission factors of the DCM-extractable organics of tire bum effluent can be expressed as the mutagenic activity per unit weight of tires (revertants/kg of fuel) or per unit heating value of tires during combustion (revertants/MJ of heat). These expressions are a function of the mutagenic potency of the organics (revertants/&, the burn rate (kg/h), the flow rate (m3/h), and the percentage of DCM-extractable organics collected on the XAD or the filters. Table 1shows the mutagenic emission factors expressed by weight consumed and heat produced from effluent of burning CHUNK or SHRED tires. The mutagenic emission factors calculated for the semivolatile organics (XAD) from CHUNK tires in the presence of S9 were greater than those for SHRED tires in experiment 1; however, this effect was reversed in experiment 2 (Table 1). This discrepancy was likely due to the different burn rates that occurred during the two experiments as well as to other factors. For a single condition withinanexperiment (e.g., CHUNK, experiment l),the addition of S9 did not greatly alter the mutagenic emission factors. Thus, the mutagenicity of the semivolatiles was due to a mixture of S9-dependent (e.&,PAH) and S9-independent (e&, substituted-PAH) mutagenic activity. The mutagenic emission factors for the particulate (filter)organicsfromCHUNKtiresweregreaterthanthose from SHRED tires in the presence of S9. In the absence of S9, SHRED tires produced higher mutagenic emission factors than did CHUNK tires. This suggests that the open burning of CHUNK tires likely produced more PAH-
type mutagens (S9-requiring) compared to SHRED, and the open burning of SHRED tires likely produced more substituted PAH-type mutagens (S9-independent) than did CHUNK tires. Two facts emerge from the data in Table 1: (a) the DCM-extractable particulate organics exhibited greater mutagenic potency (revertants/pg) as compared to the semivolatile organics and (b) the vast majority of the mutagenic activity (based on the mutagenic emission factors) is derived from the DCM-extractable particulate organics as opposed to the semivolatile organics. Comparison of Mutagenic Emission Factors. We calculated the arithmetic average of the four mutagenic emission factors in the presence of S9 (Table 1) and compared this value to those of other combustion emissions (both of closed systems, such as combustors, and open systems, such as residential fireplaces or open burning) evaluated in strain TA98 in the presence of S9 (Figure 2). The various combustion emissions ranked the same, regardless of which way the mutagenic emission factors were expressed. The mutagenic emission factor for open tire burning was the greatest of any other combustion emission studied previously (Figure 2). For example, it was 3-4 orders of magnitude greater than the mutagenic emission factors for the combustion of oil, coal, or wood in utility boilers. The data labeled “kiln” in Figure 2 were from small-scale experiments that examined emissionsfrom the combustion of the listed compounds in a laboratory-scale rotary kiln incinerator simulator that was operated under suboptimal conditions (13). The data labeled “Dinoseb” were from pilot-scale studies that examined the effect of nitrogen oxide (NO,)-reducing combustion modifications on the emissions from a boiler burning a highly nitrated waste (11). The data labeled “Open Ag. Plastic Burning” were from a controlled experiment examining emissions from the open burning of agricultural plastic (12). All other data were from field samples (10, 14). The mutagenic emission factors for the residential combustion of wood and for the open burning of agricultural plastic were closest to that of the open burning of tires (Figure 2). Both of these combustion conditions represent a type of open burning similar to that of the tire burns in the present study. All three conditions have poor combustion characteristics, and this was reflected in their high mutagenic emission factors. Thus, poor combustion conditions result in elevated levels of PICs, which result in elevated mutagenic emission factors. It is clear from the comparison in Figure 2 that the open burning of tires (as well as that of wood or plastic) resulted in high mutagenic emission factors. Thus, open burning, regardless of the feed stock or fuel, results in greater mutagenic emission factorsthan does controlled combustion provided by various types of incinerators or boilers. Role of Nitroarenes. Much of the mutagenic activity of the particulate organics, especially from the burns of SHRED tires, did not require S9 (Table 11,which is typical of many nitroaromatics (18,19). The particulate organics were evaluated for the presence of nitroaromatics by determining the mutagenic potency of the organics in strains TA98NR and TA98/1,8-DNP6 of Salmonella (see Materials and Methods above). Due to limited amounts of each sample and the similar mutagenic potency profile exhibited by the samples from the two experiments, a composite sample was prepared composed of the partic-
300
i Composite of Laboratory Tire Fire Samples
rn
5 150
U
t:
g 100 Q)
a
50 n
0
20
40
60
80
100
Dose (Uglplate) Flgure 3. Mutagenicity dose-response curves of composite sample of particulate organics in three strains of Salmonelks. 1 234
”oooli
-
Bm 800
Q c u) w
Composite of Laboratory Tire Fire Samples -so
600
e
400
5
pe 200 ‘1
5
10 15 20 25 30 35 40 45 50 55 60
Fraction number Flgure 4. Mutagram of composite sample of particulate organics in strain TA98 using a microsuspension assay. The arrows represent the locationsin which the following standards eluted: naphthalene(l), benzo[a]pyrene (2), pyrene (3), l-nltropyrene (41, and acridine (5).
d a t e organics. Figure 3 shows the mutagenicity dose-response curves of the composite particulate organics in the three strains. The mutagenic potency of the organics was similar in strains TA98 (-S9) and TA98NR (-S9), 0.93 and 0.86 revertantdpg, respectively. Thus, little of the mutagenic activity of the organics was due to the presence of mononitroaromatics. However, the mutagenic potency of the organics was reduced by 65% in strain TA98/1,8DNP6 relative to TA98, 0.36 vs 0.93 revertants/pg, respectively. This suggests that as much as 65% of the mutagenic activity as measured in the absence of S9 is due to the presence of dinitroaromatics or other nitroarenes or aromatic amines that require metabolic conversion to arylhydroxylamines and then esterification in order to be mutagenic. Bioassay-Directed Chemical Analysis. Chemical classes and individual chemicals that are responsible for the mutagenic activity of the tire burn effluent can be determined by characterizingthe organics using bioassaydirected fractionation and chemical analysis (IO). The resulting chromatograms and mutagrams of the four particulate samples were similar, and the average mass and mutagenic activity recoveries from the HPLC column were 91 and 78’36, respectively (15). Because of the similarity of the mutagrams and the limited amount of each sample, the unfractionated DCM extracts from the four particulate samples were then fractionated by HPLC as described previously. Figure 4 shows the mutagram of the composite sample of the DCM-extractable particulate organicsfrom the open Envlron. Sci. Technol., Vol. 28, No. 1, 1994
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Table 2. Chemicals Identified in HPLC Fractions of Composite of Tire Fire Samples fractiona
chemicals
A
naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, anthracene, benz[alanthracene, chrysene, benzo[bl fluoranthene, benzo[k]fluoranthene, benzo[alpyrene, dibenz[a,hlanthracene, benzo[g,h,ilperylene, indeno[l,2,3-cd]pyrene nonadecane, eicosane, anthraquinone, xanthone, benzanthrone dioctyl phthalate e-caprolactam, cyclododecane, acridine, naphthalic anhydride, benzanthrone, benzoisoquinoline, perinaphthenone, methylbenzocinnoline
B C D a
Fractions A-D were composed of the following fractions from the mutagram in Figure 4: A, 2 and 3; B, 21-25; C, 43; and D, 47-49.
Table 3. Concentration of Selected PAHs in Tire Emissions pg/g of extract" mg/kg of tire CHUNK SHRED CHUNK SHRED
PAH phenanthrene anthracene fluoranthene pyrene benz[a]anthracene chrysene benzo[b]fluoranthene benzo[a]pyrene benz [a,h]anthracene indeno [1,2,3-cdlpyrene benzo[g,h ,i]perylene benzo[k] fluoranthene naphthalene acenaphthylene acenaphthene fluorene
5 256 1825 25 052 2 676 7 764 7 414 6 721 8 554 81 5 210 5 843 7 117 81 3 678 23 181 1324
2 314 766 21 376 10 663 7 177 6 802 6 688 7 511 0 6 468 12 089 7 511 0 0 17 808 318
238 56 339 34 82 71 70 85 1 52 66 74 816 861 290 261
253 50 458 152 102 92 88 114 0 86 159 99 486 562 2 446 187
* Extracts from filters; values are the average of two experiments. ~~
~~~
~
~
~~~~
burning of scrap rubber tires. The mutagram shows four main areas of mutagenic activity, and more of the mutagenic activity is direct-acting (-S9) than S9-dependent. The first area of activity coincides with the elution of four of the standards (naphthalene, benzo[alpyrene, pyrene, and 1-nitropyrene);the fifth standard is acridine. Because some of the PAH standards eluted in the region covered by fraction A (composed of fractions 2 and 3), fraction A was analyzed for the presence of various PAHs. Table 2 shows that 14 PAHs were identified in fraction A, confirming the presence of this class of mutagen/ carcinogen in the tire effluent. PAHs require S9 in order to be mutagenic in Salmonella and, thus, could account for some of the mutagenic activity seen in the presence of S9 in fractions 2 and 3 of the mutagram. However, there is also a considerable amount of S9-independent (-S9) mutagenic activity in these two fractions that must be due to other classes of compounds, possibly requiring acetylation as suggested above (Figure 3). Fraction B, which was composed of subfractions 21-25 from the mutagram, contained several oxygenated PAHs, such as anthraquinoneand xanthone, which are mutagenic in strain TA98 (21,22). Fraction C, which was composed of subfraction 43, contained phthalate. However, phthalates are ubiquitous in environmental samples and are not mutagenic in Salmonella. Thus, another class or classes of compounds is responsible for the S9-independent mutagenic activity in subfraction C. Fraction D, which was composed of subfractions 47-49, contained various polycyclic compounds with ring nitrogens, such as acridine, which is also mutagenic in Salmonella. Thus, a variety of aromatic, multi-ringed mutagens were present in the particulate organics from the open burning of tires. 140 Envlron. Scl. Technol., Vol. 28, No. 1, 1994
PAH Concentrations. Because the results above showed that PAHs contributed substantially to the mutagenic activity of the particulate organics emitted from the open burning of tires, we determined the concentrations of selected PAHs in unfractionated, whole particulate organic extracts (Table 3). Because the burn rate was known, the concentrations of selected PAHs emitted per killogram of tire were estimated (Table 3). With few exceptions, the condition of the tire material (CHUNK VI SHRED) had little influence on the concentrations of selected PAHs emitted in the particulate organics. Summary and Conclusions In general, the semivolatile organics emitted from the open burning of CHUNK or SHRED tires exhibited similar mutagenic potencies. However, the mutagenic potencies of the particulate organics were greater than that of the semivolatiles. The open burning of CHUNK tires produced more potent organics as assayed in the presence of S9, but SHRED tires produced more potent organics as assayed in the absence of S9. Dinitroarenes or aromatic amines appear to account for much of the direct-acting (-S9) mutagenic activity of these organics, and PAHs appear to account for much of the indirect-acting (+S9) mutagenic activity of the samples. The mutagenic emission factor for the open burning of tires was 3-4 orders of magnitude greater than that for the combustion of oil, coal, or wood in utility boilers; it was most similar to values for the open burning of wood and plastic. Open burning, regardless of feed stock or fuel, appears to result in greater mutagenic emission factors than does controlled combustion as provided by various types of incinerators or boilers. Caution must be exercised in extrapolating these bioassay results in bacteria to potential health risks in humans. Further bioassaystudies in mammalian cells and rodents would be necessary to provide a clearer understanding of the biological effects of these emissions to higher organisms, including humans. Our results suggestthat the open burning of scrap rubber tires poses potential environmental and health effects. Because of the frequent occurrence of unwanted combustion at tire disposal sites and the potential environment and health risks posed by such combustion, prudence would suggest that such sites be reduced or eliminated in size and number. Instead of being discarded in stockpiles or landfills, used tires may be recycled, used in asphalt for roads, or incinerated under controlled conditions in combustion devices for cogeneration of power ( 1 , 2 , 4 ,7). Acknowledgments The research described in this paper has been reviewed by the Air and Energy Engineering Research Laboratory and the Health Effects Research Laboratory, US.Envi-
ronmental Protection Agency, and approved for publication. This does not signifythat the contents necessarily reflect the views and policies of the Agency nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Literature Cited US.EPA Office of Solid Waste. EPA/530-SW-90-074B, Sept 1991. Kearney, A. T. Scrap Tire Use/Disposal Study; Prepared for the Scrap Tire Management Council: Washington, DC, Sept 1990. Livdahl, T. P.; Willey, M. S. Science 1991,253, 189-191. Pirnie,M. AirEmksions Associations with the Combustion of Scrap Tires for Energy Recovery; Prepared for the Ohio Air Quality Development authority: May 1991. International Agency for Research on Cancer (IARC). Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. The Rubber Industry; IARC: Lyon, France, 1982; Vol. 28. Shibamoto, T.; Wei, C.-I. Agric. Biol. Chem. 1986,50,513514.
Clark, C.; Meardon, K.; Russell, D. EPA-450/3-91-024, Dec 1991.
Ryan, J. V. EPA-600/2-89-054 (NTIS PB 90-126004), Oct 1989.
International Agency for Research on Cancer (IARC) Monograph. Programme on the Evaluationof Carcinogenic Risk of Chemicals to Humans. Polynuclear Aromatic Compounds, Part 4 , Bitumens, Coal-tar and Derived Products, Shale Oils and Soots; IARC: Lyon, France, 1985; VOl. 35. Lewtas, J. Fundam. Appl. Toxicol. 1988,10,571-589.
(11) DeMarini, D. M.; Houk, V. S.; Lewtas, J.; Williams, R. W.;
Nishioka, M. G.; Srivastava, R. K.; Ryan, J. V.; McSorley, J. A.; Hall,R. E.; Linak, W. P. Environ. Sci. Technol. 1991, 25, 910-913. (12) Linak, W. P.; Ryan, J. V.; Perry, E.; Williams, R. W.; DeMarini, D. M. J. Air Pollut. Control Assoc. 1989, 39, 836-846. 113) . ~DeMarini. ~ , D. M.: Williams. R. W.: Perry, E.: Lemieux, P. M.; Linak; W. P. Combust. Sci. Technol.-1992,85,437-463. (14) Watts, R. R.; Lemieux,P. M.; Grote, R. A.; Lowane, R. W.; ~
Williams, R. W.; Brooks, L. R.; Warren, S. H.; DeMarini, D. M.; Bell, D. A.; Lewtas, J. Environ. Health Perspect.
1992,98,227-234. (15) Lemieux,P. M.; DeMarini, D. M. EPA-600/R-92-127, July 1992. (16) DeMarini, D. M.; Williams, R. W.; Taylor, M. S. Int. J. Enuiron. Anal. Chem. 1992,48, 187-199. (17) Maron, D. B.; Ames, B. N. Mutat. Res. 1983,113,173-216. (18) McCoy, E. C.; Anders, M.; Rosenkranz, H. S. Mutat. Res. 1983,121, 17-23. (19) Kohan, M.; Claxton, L. Mutat. Res. 1983, 124, 191-200. (20) DeMarini, D. M.; Dallas, M. M.; Lewtas, J. Teratogen. Carcinogen. Mutagen. 1989,9,287-295. (21) Zeiger, E.; Anderson, B.; Haworth, S.; Lawlor, T.; Mortelmans, K.Environ. Mol. Mutagen. 1988, 11 (Suppl. 12), 1-158. (22) Muramatsu, M.; Matsushima, T. Mutat. Res. 1986, 164, 274-275.
Received for review May 21,1993. Revised manuscript received September 28,1993. Accepted October 7, 1993.0 a Abstract published
in Advance ACS Abstracts, November 15,
1993.
Envlron. Scl. Technol., Vol. 28, No. 1, 1994 141
