Environ. Sci. Technol. 2001, 35, 1943-1952
Polycyclic Aromatic Hydrocarbons Identified in Soot Extracts from Domestic Coal-Burning Stoves of Henan Province, China MARY J. WORNAT,* ELMER B. LEDESMA, AND ALYSSA K. SANDROWITZ Department of Mechanical & Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 MARK J. ROTH AND SANFORD M. DAWSEY National Institutes of Health, National Cancer Institute, Division of Clinical Sciences, Cancer Prevention Studies Branch, Bethesda, Maryland 20892 YOU-LIN QIAO AND WEN CHEN Department of Epidemiology, Cancer Institute, Chinese Academy of Medical Sciences, Beijing 10021, China
Using high-pressure liquid chromatography with ultraviolet-visible diode-array detection, we have analyzed polycyclic aromatic hydrocarbons (PAH) in the dichloromethane extracts of soot deposits from coal-burning stoves in several homes of Henan Province, Chinasincluding Linxian County, where esophageal cancer rates are some of the highest in the world. Thirty-two individual polycyclic aromatic compounds, ranging in size from three to eight fused aromatic rings, have been unequivocally identified among the soot extract componentssincluding 20 benzenoid PAH, 6 fluoranthene benzologues, 1 cyclopentafused PAH, 1 indene benzologue, 3 oxygenated PAH, and 1 ring-sulfur-containing aromatic. Most of the identified compounds have been observed before among the products of laboratory coal pyrolysis experiments, but two of the components, the six-ring C24H14 naphtho[1,2-b]fluoranthene and the eight-ring C30H16 tribenzo[e,ghi,k]perylene, have never before been documented as products of coal in any system. All of the Henan coal soot extracts are remarkably similar qualitatively in that they contain the same set of identified PAH, but absolute levels of individual species vary by up to 5 orders of magnitude, from sample to sample. The bulk of the identified component mass in all of these soot extracts lies in the five- and six-ring PAHsthe largest single class being the family of five-ring C20H12 isomers, to which the samples’ most abundant components, benzo[b]fluoranthene and benzo[e]pyrene, belong. The five- and six-ring PAH also account for the majority of the samples’ known mutagens. The three strong mutagens identified in these soot samples are the C20H12 benzo[a]pyrene and two C24H14 PAH, dibenzo[a,e]pyrene and naphtho[2,1-a]pyrene. Seven moderate mutagens are found among the C20H12, C22H12, C22H14, and C24H14 PAH. A major class of mutagens, the cyclopenta-fused PAH, appears to be absent from these samples, but our detection of an oxidation product of the major mutagen cyclopenta[cd]10.1021/es001664b CCC: $20.00 Published on Web 04/06/2001
2001 American Chemical Society
pyrene-itself mutagenic-suggests that these soot deposits may contain additional mutagenic cyclopentafused PAH oxidation products as well.
Introduction During the combustion of solid fuels such as coal and wood, polycyclic aromatic hydrocarbons (PAH) are generated by high-temperature pyrolytic reactions of fuel fragments that are produced from the thermal decomposition of the solid fuel (1-4). Further pyrolysis of PAH and fuel fragments can lead to the formation of soot (1, 2), which, along with PAH, is emitted from the combustor if temperature, residence time, and oxygen concentration are not sufficient for complete oxidation. PAH are gaseous at the high temperatures of combustion, but downstream of the combustion zone, during cooling, PAH condense onto the surfaces of soot particles (5), which then serve as the vehicles of PAH transport and deposition in the environment. Because many PAH are carcinogenic (6) or mutagenic (7, 8), PAH production during fuel combustion is of concern for both environmental and health reasons. Residential-scale combustors are of particular concern since PAH and soot emissions rates from these small-scale systems are 3-4 orders of magnitude greater than from large-scale utilities (9) and since residential combustors allow for significantly greater human exposure to the emissions. The opportunity for exposure to PAH-coated soot is especially high when the product stream of a residential combustor is not vented to the out-of-doors. In such cases, residents can be exposed either by inhalation of soot particles that remain air-borne or by ingestion of soot particles that deposit on food and food-preparation surfaces within the home. Unvented residential coal combustors are commonly used in the homes of Henan Province, China, which contains some of the highest rates of esophageal cancer in the world (10). Because ingestion of PAH-coated soot is a possible cause or contributing factor (11-13), we have subjected extracts of coal-combustor soot deposits, collected from Henan Province homes, to PAH compositional analysis by high-pressure liquid chromatography (HPLC) with diode-array ultraviolet-visible (UV) absorption detection. The isomer-specific nature of the HPLC/UV technique enables us to determine the identities and quantities of any mutagenic PAH that could potentially be contributing to the observed high cancer rates. In the following, we report the identification and quantification, in these soot samples, of 32 polycyclic aromatic compounds, ranging in size from three to eight fused aromatic rings. We compare the PAH found from these residential burners with PAH produced from coal under laboratory conditions, and we present the UV spectral evidence documenting the identification of two PAH which have never before been reported as products of coal. We also report the identified PAH components’ human-cell mutagenicities, as determined by Durant et al. (7, 8) and Lafleur et al. (14).
Experimental Procedures and Materials The eight soot deposit samples analyzed in this study come from the bottom surfaces of woks that sit atop coal-burning stoves in homes of Henan Province, China. The situation of these deposits permits them to have been exposed to the * Corresponding author phone: (609)258-5278; fax: (609)258-6109; e-mail:
[email protected]. Corresponding address: Princeton University, Department of Mechanical & Aerospace Engineering, Engineering Quadrangle, Room D328, Princeton, NJ 08544-5263. VOL. 35, NO. 10, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Three- and Four-Ring Polycyclic Aromatic Hydrocarbons Identified in Extracts of Henan Province Coal-Derived Soot Samples
a Class designations: B, benzenoid PAH; C, cyclopenta-fused PAH; F, fluoranthene benzologue; I, indene benzologue. b Human cell mutagenicity of species relative to that of benzo[a]pyrene, as determined by Durant et al. (7, 8). c Not mutagenic in human cell assays but weak mutagen in bacteria bioassay (14).
effluents of the coal-burning stoves for lengthy periods. For sample collection, the soot deposits are scraped into prewashed glass bottles, which are then wrapped in aluminum foil and sealed with Teflon-lined screw caps to prevent contamination of the deposits once collected. The eight samples are designated by the names Sun 1, Sun 3, Sun 5, Sun 7, Yang 1, Yang 3, Yang 5, and Yang 7scorresponding to the different homes in which the samples were collected. To extract the adsorbed organics from the collected deposits, a ∼1-g sample of each soot deposit is weighed out and placed in an amber glass jar containing 20 mL of dichloromethane. To promote dissolution of adsorbed organics, the mixture is sonicated for 20 min in the dichloromethane and then filtered. After the initial extraction, two more times the solid deposit is placed in a new volume of dichloromethane, sonicated, and filteredsto ensure thorough transfer of adsorbed PAH from the soot deposits to the dichloromethane. The three filtered dichloromethane solutions from each soot sample are then combined to make one solution for each soot deposit. In cases for which the resulting 60-mL dichloromethane solutions are sufficiently concentrated for analysis by HPLC, a 50-µL aliquot is withdrawn and exchanged into dimethyl sulfoxide for injection onto the HPLC. For cases in which the 60-mL dichloromethane solutions are not sufficiently strong, the solutions are concentrated in a Kuderna-Danish apparatus prior to exchange into dimethyl sulfoxide. The resulting soot deposit extracts are analyzed for PAH composition by HPLC with UV absorption detection. A 20µL aliquot of each dimethyl sulfoxide extract is injected onto a Hewlett-Packard Model 1050 chromatograph, equipped with a 190-600 nm UV diode-array detector. The HPLC method, detailed elsewhere (15, 16), utilizes a reverse-phase Vydac 201TP octadecylsilica column with time-programmed mobile phases of acetonitrile/water, acetonitrile, and dichloromethane. The diode-array detector is set to monitor UV absorbance over a broad band, 190-520 nm, so that the chromatographic signals closely approximate mass concentrations (17). UV absorbance spectra are taken every 0.64 s, at a resolution of 2 nm. 1944
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We identify the component PAH by matching HPLC elution volumes and UV absorbance spectra with those of our reference standards, which include a large number of commercially available as well as specially synthesized compounds. Quantification of the identified PAH comes from extensive calibration of the HPLC/UV instrument with the reference standards, taking into account nonlinearities in the response of diode-array detectors at high analyte concentrations (18). The various constraints imposed by the available sample size, the solvent extraction and exchange procedures, and the HPLC instrument’s sensitivitysall combine to give an overall minimum detection limit of ∼2 ng PAH/g soot and an overall minimum quantification limit of ∼10 ng PAH/g soot (or 10-5 mg PAH/g soot). Because the PAH associated with the Henan soot deposits are generated from pyrolysis reactions in fuel-rich regions of the coal-burning stoves, the PAH identified in these samples are compared with PAH previously reported (1925) as products of coal pyrolysis in laboratory settings. Identified by the same HPLC/UV method as used in the present study, the laboratory-generated PAH come from two coalssone, a low-rank (geologically young, compositionally high in oxygen) brown coal pyrolyzed in a fluidized-bed reactor; the other, a high-rank (geologically old, compositionally low in oxygen) bituminous coal pyrolyzed in a fluidized-bed/tubular flow reactor. Detailed descriptions of the coals, reactors, collection procedures, and analysis techniques employed in those laboratory experiments can be found in the publications on these low-rank (19-23) and high-rank (23-25) coals.
Results and Discussion Component Identities. Tables 1-6 list the 32 polycyclic aromatic compounds identified in the dichloromethane extracts of the soot samples collected from the coal-burning stoves in Henan homes. Ranging in size from three to eight fused aromatic rings, the 32 species include several classes of PAHs20 benzenoid PAH, denoted “B” in Tables 1-5; 6 fluoranthene benzologues, denoted “F”; 1 cyclopenta-fused PAH, denoted “C”; 1 indene benzologue, denoted “I”sas
TABLE 2. Five-Ring C22H14 Polycyclic Aromatic Hydrocarbons Identified in Extracts of Henan Province Coal-Derived Soot Samples
a Class designations: B, benzenoid PAH. al. (7, 8).
b
Human cell mutagenicity of species relative to that of benzo[a]pyrene, as determined by Durant et
TABLE 3. Five-Ring C20H12 Polycyclic Aromatic Hydrocarbons Identified in Extracts of Henan Province Coal-Derived Soot Samples
a Class designations: B, benzenoid PAH; F, fluoranthene benzologue. as determined by Durant et al. (7, 8).
well as 3 oxygenated PAH and 1 ring-sulfur-containing aromatic, denoted “O” and “S,” respectively, in Table 6. The notable scarcity, in Tables 1-6, of aromatics of e three fused aromatic rings indicates that the Henan soot samples were exposed to elevated temperatures (significantly higher than room temperature) when in the presence of PAHladen gases; consequently lighter aromatics stayed in the gas phase and did not condense onto the surfaces of the soot. This assertion is supported by gas-phase measurements from other residential coal burners, which show an abundance of one-, two-, and three-ring aromatics among the emissions (26-28). Our observation is also consistent with the fact that the soot from the Henan homes was collected from the bottom surfaces of woks, which indeed would have been kept hot by coal-burning fires below. Table 1 presents the three- and four-ring PAH identified in the Henan coal soot samples: phenanthrene, acephenanthrylene, fluoranthene, pyrene, benzo[a]fluorene, triphenylene, benz[a]anthracene, and chrysene. The species include 5 benzenoid PAH, 1 fluoranthene benzologue, 1 cyclopenta-fused PAH, and 1 indene benzologuesnone of which is particularly surprising to find in these soot samples. All of these three- and four-ring PAH have been observed in laboratory-generated coal pyrolysis products (21-24, 29, 30), in residential coal-burner emissions (28, 31), and in other fuel-derived samples analyzed by means capable of discerning isomer identity (15, 21, 32-34). The cyclopenta-fused PAH acephenanthrylene is the only compound in Table 1
b
Human cell mutagenicity of species relative to that of benzo[a]pyrene,
whose identification has required acquisition of a specially synthesized (14) reference standard. What is surprising in Table 1 is the notable absence of three- and four-ring PAH such as anthracene, fluorene, benz[f]indene, and benzo[c]phenanthrenesall of which we observe as coal products in the laboratory (21-24). We suspect that these PAH were formed in the coal fires of the Henan homes but that their levels would have been depleted by subsequent chemical reactions, since these four compounds are less stable than the three- and four-ring PAH in Table 1 (21, 35). In any case, these species, if present at all, are likely to have stayed in the gas phase, not condensing onto the soot, due to the elevated soot deposit temperatures, as asserted above. Additional corroboration for this hypothesis comes from the fact that the three-ring PAH phenanthrene, one of the highest-yield PAH produced from coal at high temperatures (2, 22, 23, 29, 30), is present in very small amounts in these soot samples, as demonstrated in Table 1. Another abundant coal product (23, 26, 29, 30), the even more volatile two-ring aromatic naphthalene, is not present at all. Tables 2 and 3 list the two sets of five-ring PAH identified in the soot extracts: the cataannellated (36) C22H14 PAH and the pericondensed (36) C20H12 PAH. All of the C22H14 PAH in Table 2 are also present in our laboratory-produced coal pyrolysis products (22, 24). Another C22H14 isomer, pentaphene, is detected neither in the soot samples nor in the laboratory products (22, 24); however, it has been observed as a component of residential coal-burner emissions (28) VOL. 35, NO. 10, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 4. Six-Ring Polycyclic Aromatic Hydrocarbons Identified in Extracts of Henan Province Coal-Derived Soot Samples
a Class designations: B, benzenoid PAH; F, fluoranthene benzologue. as determined by Durant et al. (7, 8).
b
Human cell mutagenicity of species relative to that of benzo[a]pyrene,
TABLE 5. Seven- and Eight-Ring Polycyclic Aromatic Hydrocarbons Identified in Extracts of Henan Province Coal-Derived Soot Samples
a Class designations: B, benzenoid PAH. al. (7, 8).
b
Human cell mutagenicity of species relative to that of benzo[a]pyrene, as determined by Durant et
and of coal tar extract (National Institute of Standards and Technology Standard Reference Material 1597) (37). More linearly annellated C22H14 such as pentacene and benz[a]naphthacene are not very stable (38-40) and would not be expected in appreciable amounts in either environmental or laboratory-generated fuel products. The four C20H12 Henan soot components of Table 3 have also been produced by our coal pyrolysis experiments (22, 24), but the pyrolysis experiments also yield three C20H12 PAH not detected in the Henan soot samples: the commonly observed benzo[j]fluoranthene and the less-commonly observed perylene and benzo[a]fluoranthene. Benzo[j]fluoranthene and perylene are known to coelute, respectively, with benzo[e]pyrene and benzo[b]fluoranthene, the two most abundant PAH in these soot samples. However, close inspection of the UV spectra associated with the benzo[e]pyrene and benzo[b]fluoranthene chromatographic peaks reveals no sign of the unique spectral features of benzo[j]fluoranthene or perylene. We therefore conclude that if these latter two C20H12 species are present at all, they are present 1946
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in levels at least 2 orders of magnitude lower than their respective coelutants. The other “absent” C20H12 PAH, benzo[a]fluoranthene, usually less abundant than its isomers (24, 28, 31), we know to elute just before benzo[e]pyrene. A chromatographic peak appears in the appropriate place in the HPLC chromatograms of the Henan soot samples; however, the UV spectrum of this peak does not match that of benzo[a]fluoranthene (41, 42), and the corresponding component remains unidentified. The six-ring PAH identified in the Henan soot samples are listed in Table 4sboth the C22H12 and the C24H14 families of isomers. Benzo[ghi]perylene and indeno[1,2,3-cd]pyrene, the two C22H12 PAH detected, are commonly observed pyrolysis and combustion products from coal and other fuels. We have identified two other isomers in this family, anthanthrene and indeno[1,2,3-cd]fluoranthene, in our laboratory-generated coal products (24). Grimmer et al. (28) have also observed these two C22H12 PAH in residential coal-burner emissions, but neither of these C22H12 species appears to be present in the Henan coal soot samples.
TABLE 6. Oxygen- and Sulfur-Containing Polycyclic Aromatic Compounds Identified in Extracts of Henan Province Coal-Derived Soot Samples
a Class designations: O, oxygen-containing polycyclic aromatic compound; S, sulfur-containing polycyclic aromatic compound. b Human cell mutagenicity of species relative to that of benzo[a]pyrene, as determined by Durant et al. (7, 8). c Compound not tested by Durant et al. (7, 8) but determined to be mutagenic in a bacterial bioassay (91). d Compound not tested by Durant et al. (7, 8) but determined to be a direct-acting mutagen in another bioassay (90).
(24, 43), in residential coal burner emissions (28, 31, 40), or in the NIST coal tar extract (44), are not detected among the Henan coal-derived soot samples examined here, but their lack of detection could be due to coelution with more abundant sample components. Sample fractionation, by an HPLC method prior to and complementary to the HPLC analytical method, may be necessary to effect optimal resolution and identification of all of the C24H14 isomers (37, 44, 47).
FIGURE 1. UV absorbance spectra of the reference standard of naphtho[1,2-b]fluoranthene and of a Sun 7 coal soot extract component. The other six-ring compounds listed in Table 4, the five C24H14 species, belong to a large PAH family of which there are 65 isomers theoretically possible (40). Reference standards for 20 of these C24H14 PAH are available to us (7, 8), and five of the 20 are present in the Henan soot extracts, as indicated in Table 4. Two of the five, dibenzo[e,l]pyrene and naphtho[2,1-a]pyrene, have been identified in our laboratorygenerated coal pyrolysis products (19, 24, 43), in the flue gas of a residential coal burner (28, 40), and in the NIST coal tar extract (44). Two others, dibenzo[a,e]pyrene and dibenzo[b,k]fluoranthene, are not detected in our laboratory experiments (19, 24, 43) but have been observed in residential coalburner emissions (28, 40) and in the NIST coal tar extract (44). The last of the five, naphtho[1,2-b]fluoranthene, has never before been reported as a product of coal in the literature. However, by private communication (45, 46) with the authors (40), we have learned that an initially undesignated (40) C24H14 component of residential coal-burner emissions has since been determined to be naphtho[1,2-b]fluoranthene. Because the identification of this compound as a coal product has never before been published, we present, in Figure 1, the UV spectra confirming its identity in the Henan coal soot samples. We have also just recently identified naphtho[1,2-b]fluoranthene among bituminous coal pyrolysis products generated in the laboratory (43). Nine other C24H14 isomers, identified in either the laboratory experiments
Listed in Table 5 are the seven- and eight-ring PAH identified in the Henan soot sample extracts. Reference standards of the seven-ring compound coronene are commercially available, and this compound is commonly observed among combustion and pyrolysis products. Two other products of Table 5, however, benzo[a]coronene and benzo[pqr]naphtho[8,1,2-bcd]perylene, are not available commercially as reference standards, so these two eight-ring PAH have only been identified by researchers in possession of the specially synthesized reference standards (19, 24, 48-50). Both of these eight-ring PAH have been identified as components of coal tar pitch (48). Also identified with a specially synthesized reference standard (36), tribenzo[e,ghi,k]perylene, the last eight-ring compound in Table 5, has, to our knowledge, never before been observed as a product of coal or any other fuel. (Tribenzo[e,ghi,k]perylene is likely a component among the products of o-terphenyl pyrolysis, and mass spectral data (51) are consistent with this notion. However, tribenzo[e,ghi,k]perylene has not been stated as an o-terphenyl product, nor has UV or other confirming spectral evidence been provided (51).) Confirmation of the identification of tribenzo[e,ghi,k]perylene as a Henan coal soot component is found in Figure 2, which portrays the matching UV spectra of the tribenzo[e,ghi,k]perylene reference standard and the coal soot sample component. Until now, tribenzo[e,ghi,k]perylene has not been reported as a component of environmental samples. Tribenzo[e,ghi,k]perylene, along with dibenzo[e,l]pyrene and triphenylene, illustrated in Figure 3, are distinguished from all of the other identified soot sample components, in that these three compounds all belong to a class of exceptionally stable PAH called “fully benzenoid PAH”. As defined by Clar (39), members of this class of PAH contain six n π electrons (n being an integer), so that all the π electrons of fully benzenoid PAH are present as aromatic sextets. As explained by Clar, this condition confers upon the fully VOL. 35, NO. 10, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 7. Cyclopenta-Fused PAH Identified in Laboratory-Generated Coal Pyrolysis Productsa
FIGURE 2. UV absorbance spectra of the reference standard of tribenzo[e,ghi,k]perylene and of a Sun 7 coal soot extract component.
FIGURE 3. Fully benzenoid PAH identified in the Henan coal soot extracts. The inscribed circles denote aromatic sextets, as formally defined by Clar (39). benzenoid PAH an exceptional thermodynamic stability and resistance to reaction. The presence and high abundance, in our soot samples, of the three fully benzenoid PAH (relative to the less thermodynamically stable isomers) reflects this stability and resistance to reaction. Except for two six-ring compounds in Table 4 (dibenzo[a,e]pyrene and dibenzo[b,k]fluoranthene) and two eightring compounds in Table 5 (benzo[pqr]naphtho[8,1,2-bcd]perylene and tribenzo[e,ghi,k]perylene), all of the PAH identified in the Henan coal-derived soot samples are also produced in laboratory coal pyrolysis experiments (2, 2124, 29, 30). Laboratory experiments (19, 20, 23, 25), however, also produce a major class of PAH that are virtually absent from the soot samples, the cyclopenta-fused PAH (CP-PAH). Table 7 lists the CP-PAH that we have measured in the products of our coal pyrolysis experiments (19, 20, 23, 25), only one of which (acephenanthrylene) is present in detectable quantities in the Henan soot sample extracts. Although the identification of CP-PAH requires isomer-specific detection capabilities and specially synthesized reference standards (14, 52-58), CP-PAH have been identified in pyrolysis (15, 20, 59, 60) and combustion (28, 31, 32, 57, 58, 61, 62) products of a wide range of fuelssincluding ethylene (14, 57, 61, 62), benzene (32, 58), anthracene (15, 59), catechol (60), and coal (20, 25, 26, 28, 31). It is also the case that CP-PAH are observed under the same high-temperature laboratory conditions that produce common PAH such as pyrene, fluoranthene, and benzo[ghi]perylene (15, 20, 23, 60). Therefore, in some ways it seems peculiar to find the common PAH among the Henan soot extracts but not the CP-PAH. We believe that the explanation for this observation is not that the CP-PAH were not produced but that after their formation they were transformed by reaction with oxygen. Our reasons for this assertion are severalfold: (1) The electrons associated with the two external carbons of the cyclopenta ring in a CP-PAH molecule are more localized (63) than those associated with the six-membered rings in PAH. Consequently CP-PAH are particularly vulnerable to oxidation at the site of the two external carbons (40), as observed in both atmospheric (64) and metabolic (63) 1948
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a
Results from refs 19, 20, 23, 25.
environments. (2) Cyclopenta[cd]pyrene, the second most abundant CP-PAH produced by low- and high-rank coals under laboratory pyrolysis conditions (20, 25), is not observed in the Henan soot sample extracts examined here, but one of its major oxidation products (65), 4-oxabenzo[cd]pyrene3,5-dione, is, as indicated in Table 6. (3) As the soot samples examined here come mostly from the outside surfaces of woks, the soot deposits and their adsorbed PAH would have had long-time exposure to heat, light, and oxygensall of which would be conducive to CP-PAH oxidation over time. (4) Further evidence of PAH oxidation taking place is demonstrated by the identification, in Table 6, of benzanthrone and cyclopenta[def]chrysene-4-one, two aromatic ketones which result from the oxidation of another group of PAH prone to oxidation, those with methylene carbons (6669). Other PAH oxidation products may be present in our soot sample extracts, but limitations in the availability of reference standards of documented oxidation products impair further identifications of such species at this time. In addition to the oxygenated PAH, Table 6 includes benzo[b]naphtho[2,1-d]thiophene, a four-ring sulfur-containing compound also found in the emissions of a residential coal burner (31). The presence of such a component in the Henan soot extracts signifies an appreciable level of fuelbound organic sulfur in the parent coal, a noted characteristic of several Chinese coals (70). In addition to the CP-PAH of Table 7, mentioned above, there are several other species of PAH produced in laboratory coal pyrolysis experiments (19-21, 23-25, 43) but not observed in the Henan coal soot extracts examined here. The first major class of these “missing” PAH is the ethynylsubstituted PAH, which we have recently identified as products of a number of fuels (20, 23, 25, 58-60), due to the acquisition of specially synthesized reference standards (58, 71, 72). The apparent absence of ethynyl-PAH among the Henan soot extracts is less surprising than the absence of the CP-PAH, since theoretical calculations (73) show that the formation of ethynyl-PAH is less energetically favored than that of their isomers, the CP-PAHsa result borne out by our experimental observations (20, 25, 58-60, 73). Our failure to
FIGURE 4. Reverse-phase HPLC chromatogram of Sun 7 coal soot extract. The rise in baseline at ∼43 min corresponds to a change in mobile-phase composition to UV-absorbing dichloromethane. Identified components in order of elution from left to right, are as follows: phenanthrene, benzanthrone, acephenanthrylene, fluoranthene, pyrene, triphenylene, benzo[a]fluorene, cyclopenta[def]chrysene-4-one, benz[a]anthracene, chrysene, benzo[b]naphtho[2,1-d]thiophene, benzo[e]pyrene, benzo[b]fluoranthene, dibenz[a,c]anthracene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,j]anthracene, dibenz[a,h]anthracene, benzo[ghi]perylene, indeno[1,2,3-cd]pyrene, naphtho[1,2-b]fluoranthene, dibenzo[a,e]pyrene, benzo[b]chrysene, dibenzo[e,l]pyrene, picene, dibenzo[b,k]fluoranthene, coronene, naphtho[2,1-a]pyrene, benzo[a]coronene, benzo[pqr]naphtho[8,1,2-bcd]perylene, and tribenzo[e,ghi,k]perylene. detect ethynyl-PAH in the soot extracts, however, could also be explained by the fact that the ethynyl-PAH that we have identified so far as fuel products are all ethynyl-substituted naphthalenes,acenaphthylenes,anthracenes,andphenanthreness all of which may be too volatile to have condensed on the soot deposits, if in fact the deposits were kept hot, as we asserted earlier. Another class of coal products apparently missing from the Henan soot extracts is the methylated PAH, which not only have been observed in laboratory experiments (19, 21, 23, 24) but have also been measured among the gas-phase emissions of residential coal burners (26, 28, 31, 74, 75). Like other groups of PAH of low ring number, methylated naphthalenes, anthracenes, and phenanthrenes might be too volatile to have condensed on the Henan soot deposits. However, it is also likely that methylated PAH, if formed, would have undergone dealkylation and other reactions (7678) in this high-temperature environment, as alkylated PAH are considerably less thermally stable than their unsubstituted counterparts (2, 79). The apparent absence of methylated PAH from these Henan soot deposits is an important observation since several methylated PAHse.g., 1-methylphenanthrene and 9-methylphenanthrene (80), 5-methylchrysene (81, 82), and 7,12-dimethylbenz[a]anthracene (38)sare noted carcinogens. Methylated PAH have been credited (74, 75) as the major contributors to the mutagenicity exhibited by samples collected from homes burning coal in a different region of China, but this class of PAH appears not to be present in the Henan soot extracts examined here. Other aromatic products from laboratory coal pyrolysis experiments (19, 21, 24, 43), but not found in the Henan coal soot extracts, include biaryls, ring-oxygen-containing aromatics, and members of PAH classes already discussed above.
Component Quantification. The component identifications and quantifications given in Tables 1-6 come from the HPLC/UV analyses of the Henan soot sample extracts, as manifested in the samples’ chromatograms. Figure 4 presents the HPLC chromatogram of the Sun 7 coal soot extract, the sample of highest PAH concentration. All of the Sun and Yang soot samples are qualitatively similar in that they contain the same set of identified components. The chromatograms thus all look very similar to Figure 4, except that the component peaks are less prominent in the chromatograms of the samples with very low PAH concentration (e.g., Yang 3 and Yang 5). Like many product samples from coal (22, 24, 28, 31) and residential burners (28, 31, 83), the Henan soot extracts are extremelycomplexmixtures,containingmultiplecomponentss not all of which are fully resolved and identified. Approximately 50% of the chromatographed PAH mass in these samples is accounted for by the compounds identified in Tables 1-6. The yields of these components are calculated from the integrated peak areas of the chromatograms, and special care has been taken in the peak integration process to ensure consistency between samples and to properly quantify components whose peaks are not fully resolved from one another. Due to limitations in sample size, the sample preparation procedure generally yields enough PAH/dimethyl sulfoxide solution for only two injections of a given extract onto the HPLC. However, duplicate injections of a given solution have proven to yield identical HPLC chromatograms, so single injections are sufficient. Therefore the values reported in Tables 1-6 correspond to single injections of each soot deposit extract. Tables 1-6 reveal that individual species’ yields vary enormously from sample to samplestypically over a range VOL. 35, NO. 10, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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of 4 orders of magnitude for a given component. As mentioned above, components in samples Yang 3 and Yang 5 are very low in yield, on the order of 10-5 to 10-4 mg/g soot. Levels in the Sun 3 and Sun 5 samples are also quite low but generally 2 orders of magnitude greater than those in Yang 3 and Yang 5. Component yields in Sun 1 and Yang 1 are generally comparable to one another and an order of magnitude higher than those in the Sun 3 and Sun 5. Sun 7 and Yang 7 contain the highest levels of PAH, with component yields on the order of 10-2-100 mg/g soot. For the sake of comparison, we note that PAH associated with urban particulate matter are generally present at levels of 10-4-10-2 mg PAH/g solid (37, 84-86). Even though the absolute amounts of the components vary from sample to sample, the Henan coal soot extracts are similar compositionally in several ways. For example, all of the samples contain families of isomers that generally adhere to the same orders of abundance:
C16H10: fluoranthene > pyrene C18H12: chrysene > triphenylene > benz[a]anthracene C20H12: benzo[b]fluoranthene > benzo[e]pyrene > benzo[a]pyrene > benzo[k]fluoranthene C22H12: benzo[ghi]perylene > indeno[1,2,3-cd]pyrene C22H14: picene > dibenz[a,j]anthracene > dibenz [a,h]anthracene > dibenz[a,c]anthracene > benzo [b]chrysene C24H14: dibenzo[e,l]pyrene > naphtho [1,2-b]fluoranthene > dibenzo[b,k]fluoranthene > dibenzo[a,e]pyrene g naphtho[2,1-a]pyrene C28H14: benzo[a]coronene > benzo[pqr]naphtho [8,1,2-bcd]perylene The above isomer-abundance orders are generally not exhibited by our laboratory-generated products (19, 24, 43), which may be more kinetically determined. There are similarities, however, between the orders listed above and those reported in the literature for urban particulate matter samples: C16H10 (84-87), C20H12 (85), C22H12 (84, 85), and C22H14 (37). Limitations of the analytical methods employed in the literature studies do not permit full comparison among the C18H12 and C28H14 isomer families. Durant et al. (85) report the same C24H14 species in urban particulate matter as the C24H14 species listed above, but their order of abundance is different. Another way in which the Henan soot extracts are similar to one another is that the bulk of their component mass (over three-fourths) lies in the five- and six-ring components. This observation, evident for the Sun 7 extract in Figure 4, is more quantitatively illustrated in Figure 5, which portrays the mass proportion of each group of identified PAH by ring number and distinguishes between the isomer families composing the four-, five-, six-, and eight-ring PAH. As Figure 5 demonstrates, the most abundant PAH family comprising the Henan soot extracts is the five-ring C20H12 isomers. In fact benzo[b]fluoranthene and benzo[e]pyrene, two isomers in this family, are the two most abundant species in all of the Henan coal soot extracts. The fact that the most prominent species in these soot extracts are unsubstituted, five- and six-ring pericondensed PAH suggests that these samples represent coal pyrolysis products that have seen extensive reaction (high temperature for perhaps a prolonged time) (1, 2). Such conditions effect preferential depletion of alkyl1950
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FIGURE 5. Mass proportions of each group of identified PAH by ring number. substituted, low-ring-number, and cataannellated PAH as well as any aromatics with ring S, O, or N (1, 2, 88). Component Mutagenicities. Although numerous tests for mutagenicity, tumorigenicity, and carcinogenicity have been conducted on PAH, we have chosen the results of Durant et al. (7, 8) and Lafleur et al. (14), from the human-cell bioassay of Crespi and Thilly (89), for the mutagenicity information provided in Tables 1-6. The reasons are as follows: (1) the use of a single type of bioassay facilitates comparisons between different species; (2) human cell mutagenicity results, though determined only on one type of human cell, may be more directly applicable to human health effects than those obtained from bacterial tests; and (3) the tests of Durant et al. (7, 8) and Lafleur et al. (14) cover a broad range of PAH and associated species produced by fuel combustion, including most of the species identified here in the soot samples. Durant et al. (7, 8) report each compound’s mutagenicity in terms of the minimum concentration of the compound needed to induce statistically significant mutation in human lymphoblastoid cells. Since this minimum concentration is an inverse measure of mutagenicity (i.e., more potent mutagens are mutagenic at lower concentrations), the relative mutagenicity (RM) we report for a given compound in Tables 1-6 is the ratio of benzo[a]pyrene’s minimum mutagenic molar concentration to that of the given compound. These computed RM values determine the classification of the compound as either a strong mutagen (RM g 1), a moderate mutagen (1 > RM > 0.1), a weak mutagen (0.1 > RM > 0.01), an extremely weak mutagen (0.01 > RM > 0.001), or not mutagenic. As indicated in Tables 1-6, the only identified soot sample components not tested by Durant et al. (7, 8) or Lafleur et al. (14) are dibenz[a,c]anthracene in Table 2, the three eight-ring PAH in Table 5, and two of the oxygenated species in Table 6, cyclopenta[def]chrysene-4-one and 4-oxabenzo[cd]pyrene-3,5-dione. Dibenz[a,c]anthracene is the subject of some dispute but appears to be inactive as a carcinogen (6). Although we do not know, we might speculate that the three eight-ring PAH could be too large to be mutagenic, as some researchers have noted that large molecular size hinders solubility and/or molecular transport (40). 4-Oxa-benzo[cd]pyrene-3,5-dione, on the other hand, we would expect to be a strong mutagen since its parent compound cyclopenta[cd]pyrene is a strong mutagen (RM ) 6.9) (7) and 4-oxa-benzo[cd]pyrene-3,5-dione would likely be an intermediate in cyclopenta[cd]pyrene’s metabolic
oxidation. Tests on this compound by another type of bioassay indicate that in fact 4-oxa-benzo[cd]pyrene-3,5dione is a direct-acting mutagen (90). Cyclopenta[def]chrysene-4-one, the other oxygenated PAH in Table 6 not tested by Durant et al., has also been shown to be mutagenic in a bacterial bioassay (91). Inspection of Tables 1-6 reveals that the mutagenic species in these coal-derived soot samples lie chiefly among the five- and six-ring PAH in Tables 3 and 4. Moderate mutagens are found among the C20H12 benzo[b]fluoranthene and benzo[k]fluoranthene, the C22H12 benzo[ghi]perylene and indeno[1,2,3-cd]pyrene, the C22H14 dibenz[a,j]anthracene and dibenz[a,h]anthracene, and the C24H14 dibenzo[b,k]fluoranthene. The three strong mutagens in these soot samples are the C20H12 benzo[a]pyrene and the two C24H14 PAH dibenzo[a,e]pyrene and naphtho[2,1-a]pyrene. Seven other C24H14 strong mutagens, including the exceptionally mutagenic naphtho[2,3-a]pyrene (RM ) 11) and dibenzo[a,l]pyrene (RM ) 24) (8), appear not to be present among the soot samples examined heresalthough, as stated earlier, sample fractionation prior to HPLC analysis may be necessary to eliminate all question of nondetection due to component coelution. The virtual absence of CP-PAH, a PAH class generally noted for its mutagenicity (14, 63, 92), in the Henan soot samples eliminates mutagenic CP-PAH from consideration as obvious contributors to mutagenicity in these samples. However, as stated earlier, it is our belief that CP-PAH would have been generated in the combustion zones of these coal stoves but then subsequently converted to oxygenated derivatives while adsorbed on the hot soot deposits downstream of the combustion process. Our detection of 4-oxabenzo[cd]pyrene-3,5-dione, an oxidation product of cyclopenta[cd]pyrene, provides some evidence for this hypothesis, but further substantiation is hard to come by at this time, since little work has been done on the speciation of CP-PAH oxidation products. Nevertheless, the importance of this CPPAH oxidation question should not be overlooked, since oxygenated derivatives of CP-PAH (representative of intermediates in CP-PAH metabolic oxidation) may very well exhibit mutagenicities comparable to or even higher than those of the CP-PAH themselves.
Acknowledgments The authors thank Dr. Arthur Lafleur and Ms. Elaine Plummer, of the Massachusetts Institute of Technology, and Dr. John Fetzer, of Chevron Research, for providing spectra of PAH reference standards.
Literature Cited (1) Wornat, M. J.; Sarofim, A. F.; Longwell, J. P. Proc. Combustion Institute 1988, 22, 135. (2) Wornat, M. J.; Sarofim, A. F.; Longwell, J. P. Energy Fuels 1987, 1, 431. (3) Serio, M. A.; Hamblen, D. G.; Markham, J. R.; Solomon, P. R. Energy Fuels 1987, 1, 138. (4) Fletcher, T. H.; Solum, M. S.; Grant, D. C.; Critchfield, S.; Pugmire, R. J. Proc. Combustion Institute 1990, 23, 1231. (5) Wornat, M. J.; Sarofim, A. F. Aerosol Sci. Technol. 1990, 12, 832. (6) Dipple, A.; Moschel, R. C.; Bigger, C. A. H. In Chemical Carcinogens, 2nd ed.; Searle, C. E., Ed.; ACS Monograph 182; American Chemical Society: Washington, DC, 1984; Vol. 1, pp 41-164. (7) Durant, J. L.; Busby, W. F., Jr.; Lafleur, A. L.; Penman, B. W.; Crespi, C. L. Mutation Res. 1996, 371, 123. (8) Durant, J. L.; Lafleur, A. L.; Busby, W. F., Jr.; Donhoffner, L. L.; Penman, B. W.; Crespi, C. L. Mutation Res. 1999, 446, 1. (9) Polycyclic Aromatic Hydrocarbons: Evaluation of Sources and Effects; National Research Council Report PB84-155233; National Academy Press: Washington, DC, 1983. (10) Li, J. Y. Natl. Cancer Inst. Monogr. 1982, 62, 113. (11) Roth, M. J.; Strickland, K. L.; Wang, G. Q.; Rothman, N.; Greenberg, A.; Dawsey, S. M. Eur. J. Cancer 1998, 34, 757.
(12) Roth, M. J.; Wang, G. Q.; Lewin, K. J.; Ning, L.; Dawsey, S. M.; Wesley, M. N.; Giffen, C.; Xie, Y. Q.; Maher, M. M.; Taylor, P. R. Human Pathology 1998, 29, 1294. (13) Roth, M. J.; Dawsey, S. M.; Wang, G.-Q.; Tangrea, J. A.; Zhou, B.; Ratnasinghe, D.; Woodsen, K. G.; Olivero, O. A.; Poirier, M. C.; Frye, B. L.; Taylor, P. R.; Weston, A. Cancer Lett. 2000, 156, 73. (14) Lafleur, A. L.; Longwell, J. P.; Marr, J. A.; Monchamp, P. A.; Plummer, E. F.; Thilly, W. G.; Mulder, P. P. Y.; Boere, B. B.; Cornelissse, J.; Lugtenburg, J. Environ. Health Perspect. 1993, 101, 146. (15) Wornat, M. J.; Sarofim, A. F.; Lafleur, A. L. Proc. Combustion Institute 1992, 24, 955. (16) Wornat, M. J.; Lafleur, A. L.; Sarofim, A. F. Polycyclic Aromat. Compd. 1993, 3, 149. (17) Lafleur, A. L.; Monchamp, P. A.; Plummer, E. F.; Wornat, M. J. Anal. Lett. 1987, 20, 1171. (18) Dose, E. V.; Guiochon, G. Anal. Chem. 1989, 61, 2571. (19) Vernaglia, B. A. M.S.E. Thesis, Princeton University, Princeton, NJ, 1997. (20) Wornat, M. J.; Vernaglia, B. A.; Lafleur, A. L.; Plummer, E. F.; Tagizadeh, K.; Necula, A.; Scott, L. T. Proc. Combustion Institute 1998, 27, 1677. (21) Wornat, M. J.; Mikolajczak, C. J.; Vernaglia, B. A.; Kalish, M. A. Energy Fuels 1999, 13, 1092. (22) Vernaglia, B. A.; Wornat, M. J.; Li, C.-Z.; Nelson, P. F. Proc. Combustion Institute 1996, 26, 3287. (23) Wornat, M. J.; Ledesma, E. B. Polycycl. Aromatic Compds. 2000, 18, 129. (24) Ledesma, E. B.; Kalish, M. A.; Nelson, P. F.; Wornat, M. J.; Mackie, J. C. Fuel 2000, 79, 1801. (25) Ledesma, E. B.; Kalish, M. A.; Nelson, P. F.; Wornat, M. J.; Mackie, J. C. Energy Fuels 1999, 13, 1168. (26) Knobloch, T.; Engewald, W. J. High-Resolution Chromatogr. 1993, 16, 239. (27) Sloss, L. L.; Smith, I. M. Organic Compounds from Coal Utilisation; International Energy Agency Report IEACR/63; IEA Coal Research: London, 1993. (28) Grimmer, G.; Jacob, J.; Dettbarn, G.; Naujack, K.-W. Fresnius’ Z. Anal. Chem. 1985, 322, 595. (29) Nelson, P. F.; Tyler, R. J. Proc. Combustion Institute 1986, 21, 427. (30) Bissett, L. A.; Lamey, S. C. Energy Fuels 1988, 2, 827. (31) Grimmer, G.; Jacob, J.; Naujack, K.-W.; Dettbarn, G. Anal. Chem. 1983, 55, 892. (32) Marsh, N. D.; Zhu, D.; Wornat, M. J. Proc. Combustion Institute 1998, 27, 1897. (33) Swallow, K. C.; Howard, J. B.; Grieco, W.; Benish, T. G.; Taghizadeh, K.; Plummer, E. F.; Lafleur, A. L. Polycyclic Aromat. Compd. 1999, 14-15, 201. (34) Lafleur, A. L.; Gagel, J. J.; Longwell, J. P.; Monchamp, P. A. Energy Fuels 1988, 2, 709. (35) Herndon, W. C.; Nowak, P. C.; Connor, D. A.; Lin, P. J. Am. Chem. Soc. 1992, 114, 41. (36) Clar, E. J. Polycyclic Hydrocarbons; Academic Press: New York, 1964. (37) Wise, S. A.; Deissler, A.; Sander, L. C. Polycyclic Aromat. Compd. 1993, 3, 169. (38) Zander, M. In Anthropogenic Compounds; Springer-Verlag: Berlin, 1980. (39) Clar, E. J. The Aromatic Sextet; John Wiley & Sons: London, 1972. (40) Schmidt, W.; Grimmer, G.; Jacob, J.; Dettbarn, G.; Naujack, K.W. Fresnius’ Z. Anal. Chem. 1987, 326, 401. (41) Lang, K. F.; Buffleb, H. Chem. Ber. 1961, 94, 1075. (42) Photoelectric Spectroscopy Group, London, and Institut fu¨r Spectrochemie und Angewandte Spektroskopie, Dortmund. UV Atlas of Organic Compounds; Plener Press: New York, 1966; Vol. II. (43) Ledesma, E. B.; Wornat, M. J. In preparation. (44) Wise, S. A.; Benner, B. A.; Liu, H.; Byrd, G. D.; Colmsjo¨, A. Anal. Chem. 1988, 60, 630. (45) Lafleur, A. L. Massachusetts Institute of Technology, personal communication, 1998. (46) Schmidt, W. Institut fu ¨ r PAH-Forschung; Lafleur, A. L. Massachusetts Institute of Technology, personal communication, 1997. (47) Plummer, E. F.; Lafleur, A. L.; Wornat, M. J. In preparation. (48) Fetzer, J. C.; Kershaw, J. R. Fuel 1995, 74, 1533. (49) Fetzer, J. C.; Biggs, W. R.; Jinno, K. Chromatographia 1986, 21, 439. VOL. 35, NO. 10, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
1951
(50) Lafleur, A. L.; Taghizadeh, K.; Howard, J. B.; Anacleto, J. F.; Quilliam, M. A. J. Am. Soc. Mass Spectrom. 1996, 7, 276. (51) Masonjones, M. C.; Mukherjee, J.; Sarofim, A. F.; Taghizadeh, K.; Lafleur, A. L. Polycyclic Aromat. Compd. 1996, 8, 229. (52) Olde-Boerrigter, J. C.; Mulder, P. P. J.; van der Gen, A.; Mohn, G. R.; Cornelisse, J.; Lugtenburg, J. J. R. Natl. Chem. Soc. 1989, 108, 79. (53) Boere, B. B.; Mulder, P. P. J.; Cornelisse, J.; Lugtenburg, J. J. R. Natl. Chem. Soc. 1990, 109, 463. (54) Tintel, C.; van der Brugge, M.; Lugtenburg, J.; Cornelisse, J. J. R. Natl. Chem. Soc. 1983, 102, 220. (55) Scott, L. T.; Necula, A. J. Org. Chem. 1996, 61, 386. (56) Necula, A. Ph.D. Thesis, Boston College, Chestnut Hill, MA, 1996. (57) Lafleur, A. L.; Howard, J. B.; Plummer, E. F.; Taghizadeh, K.; Necula, A.; Scott, L. T.; Swallow, K. C. Polycyclic Aromat. Compd. 1998, 12, 223. (58) Marsh, N. D.; Wornat, M. J.; Scott, L. T.; Necula, A.; Lafleur, A. L.; Plummer, E. F. Polycyclic Aromat. Compd. 2000, 13, 379. (59) Wornat, M. J.; Vriesendorp, F. J. J.; Lafleur, A. L.; Plummer, E. F.; Necula, A.; Scott, L. T. Polycyclic Aromat. Compd. 1999, 13, 221. (60) Wornat, M. J.; Ledesma, E. B.; Marsh, N. D. Fuel, in press. (61) Benish, T. G.; Lafleur, A. L.; Taghizadeh, K.; Howard, J. B. Proc. Combustion Institute 1996, 26, 2319. (62) Lafleur, A. L.; Howard, J. B.; Taghizadeh, K.; Plummer, E. F.; Scott, L. T.; Necula, A.; Swallow, K. C. J. Phys. Chem. 1996, 100, 17421. (63) Fu, P. P.; Beland, F. A.; Yang, S. K. Carcinogenesis 1980, 1, 725. (64) Hites, R. A. In Atmospheric Aerosols: Source/Air Quality Relationships; ACS Symposium Series 167; American Chemical Society: Washington, DC, 1981; pp 187-196. (65) Swallow, K. C.; Taghizadeh, K.; Weakland, S.; Plummer, E. F.; Busby, W. F., Jr.; Lafleur, A. L. Intern. J. Environ. Anal. Chem. 1995, 60, 113. (66) Allen, J. O.; Dookeran, N. M.; Taghizadeh, K.; Lafleur, A. L.; Smith, K. A.; Sarofim, A. F. Environ. Sci. Technol. 1997, 31, 2064. (67) Ramdahl, T. Environ. Sci. Technol. 1983, 17, 666. (68) Korfmacher, W. A.; Natusch, D. F. S.; Taylor, D. R.; Mamantov, G.; Wehry, E. L. Science 1980, 207, 763. (69) Strietwieser, A., Jr.; Word, J. M.; Guibe´, F.; Wright, J. S. J. Org. Chem. 1981, 46, 2588. (70) Speight, J. G. The Chemistry and Technology of Coal, 2nd ed.; Marcel Dekker: New York, 1994. (71) Hopkins, N. E.; Foroozesh, M. K.; Alworth, W. L. Biochemical Pharmacol. 1992, 44, 787. (72) Hall, M.; Parker, D. K.; Grover, P. L.; Lu, J.-Y. L.; Hopkins, N. E.; Alworth, W. L. Chem. Biol. Interact. 1990, 76, 181.
1952
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 35, NO. 10, 2001
(73) Marsh, N. D.; Wornat, M. J. Proc. Combustion Institute 2000, 28, 2585. (74) Mumford, J. L.; Li, X.; Hu, F.; Lu, X. B.; Chuang, J. C. Carcinogenesis 1995, 16, 3031. (75) Chuang, J. C.; Wise, S. A.; Cao, S.; Mumford, J. L. Environ. Sci. Technol. 1992, 26, 999. (76) Badger, G. M.; Spotswood, T. M. J. Chem. Soc. 1960, 1960, 4420. (77) Badger, G. M.; Kimber, R. W. K.; Novotny, J. Austr. J. Chem. 1964, 17, 778. (78) Badger, G. M.; Kimber, R. W. K. J. Chem. Soc. 1961, 1961, 3407. (79) Blumer, M. Sci. Am. 1976, 234, 35. (80) LaVoie, E.; Tulley, L.; Bedenko, V.; Hoffmann, D. In Polynuclear Aromatic Hydrocarbons: Chemistry and Biological Effects; Bjorseth, A., Dennis, A. J., Eds.; Battelle Press: Columbus, OH, 1985; pp 1041-1057. (81) Lee, M. L.; Wright, B. W. J. Chromatog. Sci. 1980, 18, 345. (82) Hecht, S. S.; Melikian, A. A.; Amin, S. Acc. Chem. Res. 1987, 114, 217. (83) Leary, J. A.; Biemann, K.; Lafleur, A. L.; Kruzel, E. L.; Prado, G. P.; Longwell, J. P.; Peters, W. A. Environ. Health Perspectives 1987, 73, 223. (84) Wise, S. A.; Benner, B. A.; Chesler, S. N.; Hilpert, L. R.; Vogt, C. R.; May, W. E. Anal. Chem. 1986, 58, 3067. (85) Durant, J. L.; Lafleur, A. L.; Plummer, E. F.; Taghizadeh, K.; Busby, W. F., Jr.; Thilly, W. G. Environ. Sci. Technol. 1998, 32, 1894. (86) Savard, S.; Otson, R.; Douglas, G. R. Mutat. Res. 1992, 276, 101. (87) Allen, J. O.; Dookeran, N. M.; Smith, K. A.; Sarofim, A. F.; Taghizadeh, K.; Lafleur, A. L. Environ. Sci. Technol. 1996, 30, 1023. (88) Wornat, M. J.; Sarofim, A. F.; Longwell, J. P.; Lafleur, A. L. Energy Fuels 1988, 2, 775. (89) Crespi, C. L.; Thilly, W. G. Mutat. Res. 1984, 128, 221. (90) Rappaport, S. M.; Wang, Y. Y.; Wei, E. T.; Sawyer, R.; Watkins, B. E.; Rapoport, H. Environ. Sci. Technol. 1980, 14, 1505. (91) Rice, J. E.; Makowski, G. S.; Hosted, T. J., Jr.; Lavoie, E. J. Cancer Lett. 1985, 27, 199. (92) Nesnow, S.; Leavitt, S.; Easterling, R.; Watts, R.; Toney, S. H.; Claxton, L.; Sangaiah, R.; Toney, G. E.; Wiley, J.; Fraher, P.; Gold, A. Cancer Res. 1984, 44, 4993.
Received for review September 12, 2000. Revised manuscript received February 20, 2001. Accepted February 26, 2001. ES001664B
