Genotoxicity of syrian hamster lung cells treated in vivo with diesel exhaust particulates

Polycyclic aromatic hydrocarbons extracted and concentrated from diesel exhaust particulates have been shown to be mutagenic and carcinogenic, but attempts to induce pulmonary tumors through chronic inhalation of diesel exhaust by experimental animals have failed. We have attempted to resolve this incongruity by measuring chromosomal damage in lung tissue of chronically exposed hamsters, using the highly sensitive test for genotoxic chemical agents, sister chromatid exchange (SCE) analysis. To determine the degree of responsiveness of the test system to both diesel exhaust particulates and benzo(a)pyrene (BaP), these agents were instilled intratracheally into anesthetized hamsters as suspensions in 0.25 ml volumes of Hank's balanced salt solution (HBSS). Lung tissues from these animals were subsequently cultured in vitro and chromosomes from the resulting cell divisions were scored for exchanges of chromatin between sister chromatids. Control animals, treated weekly with 0.25 ml of BSS for 10 weeks, showed an average value of 12 SCE's per cell, while animals treated weekly with 200 ng BaP over a 10-week period showed an average of 17 SCE's per cell. HBSS, given as a single treatment, also produced an average of 12 SCE's per cell in control animals, but animals treated with a single instillation of 12.5 μg BaP showed an average SCE value of 19. These data confirmed that the procarcinogen BaP can be metabolically activated by lung cells in vivo and also demonstrated the efficacy of using this technical approach to study the effect of chemical mutagens that enter the lungs. Diesel exhaust particulates, administered in a range from 0 to 20 mg per hamster over a 24 h exposure period, produced a linear SCE dose-response ranging from 12 to 26 SCE's per metaphase. This curve suggested that a concentration of 3 mg of diesel particulates per hamster would not produce a statistically significant increase in SCE's above control values. One group of 8 hamsters, chronically exposed to diesel exhaust particulates for 3 months showed an average of 12 SCE's per cell. This was equivalent to a set of 5 control animals which also showed an average of 12 SCE's per cell. Although the scope of this study was limited, the data demonstrated that diesel exhaust particulates can induce genotoxic damage but a 3-month exposure to 6 mg/m³ of diesel exhaust particulates was insufficient to produce measurable mutagenic changes in lung cells. This negative response is consistent with the results from other studies in which similar exposures failed to produce pulmonary tumors.     

Mutagenic and carcinogenic potency of extracts of diesel and related environmental emissions: Study design, sample generation, collection, and preparation

A major diesel emissions research program has been initiated by the U.S. Environmental Protection Agency to assess the human health risk associated with increased use of diesel automobiles. This program is intended to establish the mutagenic and carcinogenic potency of complex organics associated with diesel particles as well as comparative particle-bound organics from other environmental emissions for which human epidemiological data are available. The mobile source samples selected for this study were collected from a heavy-duty diesel engine, a series of light-duty diesel passenger cars, and a gasoline catalyst automobile. The comparative source samples incorporated into the study were cigarette smoke condensate, coke oven emissions, roofing tar emissions, and benzo(a)pyrene. The samples were tested using three mutagenic assays and four carcinogenic assays as prescribed by a test matrix. This report describes the study design, particle generation, and sample collection and preparation. A brief summary of the bioassays is also included.     

Salmonella/microsome mutagenicity assays of exhaust from diesel and gasoline powered motor vehicles

Motor vehicle exhaust from prechamber injection diesel and gasoline powered passenger cars, sampled during US FTP 1973 test cycles and comprising both particulate matter and compounds condensable at ambient temperature, has been assayed for mutagenicity in the Salmonella/microsome test. Mutagenic components were to a large extent active in the absence of the mammalian microsomal preparation. The mutagenicity of both particulate matter and condensate from diesel exhaust and condensate from gasoline exhaust was decreased in the presence of the microsomal preparation whereas the mutagenicity of particulate matter from gasoline exhaust was enhanced by microsomal activation. A comparison between the investigated diesel and gasoline exhaust samples shows that the mutagenic effect in the Salmonella test of the diesel exhaust is more than ten times higher than that of the gasoline exhaust. Fractionation with respect to polarity indicates that the mutagenic components mainly are distributed in neutral aliphatic, aromatic, and oxygenated fractions. Tests for mutagenic monofunctional nitroarenes by an anaerobic assay indicate that such compounds at most are marginally present in the exhaust samples as compared with their presence in airborne particulate matter collected in an urban environment.     

The mutagenic activity of thirty polycyclic aromatic hydrocarbons (PAH) and oxides in urban airborne particulates

Data are presented on the mutagenicity of an organic extract of a composite sample of urban air particulates and of thirty PAH compounds in such samples, including four quinone derivatives, isolated quantitatively by thin-layer chromatography and identified by fluorescence or other spectral techniques. Mutagenic activity was determined by the Ames assay, using histidine auxotrophs of Salmonella typhimurium strains TA98, TA100, TA1537 and TA1538. All compounds were dissolved in dimethyl sulfoxide (DMSO) which was the least toxic of eight organic solvents tested.The mutagenic activity of a benzene extract of suspended particulates from the air of Hamilton, Ontario was significantly greater with strain TA98 than with strain TA100, suggesting the presence of more frame-shift acting mutagens. The mutagenic response of this extract was similar with and without S-9 activation.Mutagenic tests on the 30 PAH compounds indicated that only the benzo(a)pyrene quinones were direct acting mutagens. All of the chemical compounds were tested with and without S-9 activation. The following PAH showed unequivocal mutagenic activity, with S-9 activation: benz(a)anthracene, benzo-(a)pyrene, benzo(ghi)perylene, benzo(rst)pentaphene, benzophenanthrene, chrysene, 1, 2, 3, 4-dibenzanthracene, 2, 3, 6, 7-dibenzanthracene, and 3-methyl cholanthrene. The quinones of 1, 6-; 3, 6-; and 6, 12-benzo(a)pyrenes showed weak mutagenic activity but 3, 6-benzo(a)pyrene elicited also a photodynamic response.     

Benzo[a]pyrene metabolism in mice exposed to diesel exhaust: I. Uptake and distribution

In this study we examined the effect of diesel exhaust (DE) exposure on the disposition of a typical polycyclic aromatic hydrocarbon. DE-exposed and nonexposed A/Jax mice were divided into three groups and each mouse instilled intratracheally with benzo[a]pyrene (BaP). One group (A) received ¹⁴C-BaP, and at intervals of 2, 24, and 168 h, three mice from the group were killed and quick frozen for whole body autoradiography. Sagittal sections were cut at 0.5 mm intervals and autoradiograms prepared. Adjacent sections were studied so that radioactive areas were matched to specific organs. The second group (B) received ³H-BaP and at 2, 24, and 168 h these mice were killed. Livers, lungs, and testes were weighed and frozen. From these tissues metabolites were analyzed; these data are reported in the next paper. Histofluorescent examination of tissues from mice instilled with nonradioactive BaP (group C) confirmed that BaP was present in the lung. The autoradiography data are the basis for elucidating the BaP distribution in the mouse. Within 2 h after instillation radioactivity was detected in the entire animal, with most in lungs, liver, and GI tract. By 24 h after instillation considerable radioactivity had redistributed to the GI tract. At 168 h after instillation only a trace of label was found in the GI mucosa.     

Deposition and biological availability of diesel particles and their associated mutagenic chemicals

To estimate the human health risk of inhaled diesel particles, it is necessary to know their deposition and retention in the respiratory tract and the rate of dissociation of mutagenic compounds associated with the particles. The deposition of a chain aggregate aerosol of ⁶⁷Ga₂O₃ with size and shape characteristics similar to diesel exhaust particles has been evaluated using Beagle dogs. Approximately one-third of the inhaled activity is deposited in the respiratory tract with most of the particles deposited in the lung. The mutagenic activity present in dichloromethane, dog serum, dog lung lavage fluid, saline, dipalmitoyl lecithin (DPL) and albumin following incubation of these fluids with diesel exhaust particles was determined in the Ames Salmonella system. As observed by other investigators, large quantities of mutagenic activity were removed by dichloromethane. A very small amount of mutagenic activity was removed by the serum and lavage fluid over a 3-day incubation period. No activity was detected following elution with the other solvents. The finding that minimal mutagenic activity could be demonstrated in the biological media following incubation with diesel exhaust particles may be due to a lack of removal of mutagens from the particles or an inactivation of removed mutagens by protein binding or other processes.     

Metaphase analysis, micronuclei assay, and urinary mutagenicity assay of mice exposed to diesel emissions

Female Swiss mice were exposed 8 h/day to diesel exhaust for 1, 3, and 7 weeks. Urine was collected overnight for 4 days prior to sacrifice while the mice continued to be exposed for eight hours during the day. The presence of mutagens was determined by the Ames Salmonella test. One hour prior to sacrifice each mouse received 1 mg/kg colcemide. After sacrifice, the marrow from each femur was obtained. The marrow from one femur was used to prepare slides for metaphase analysis and the other for micronuclei assay. Other mice received IP 50 mg/kg cyclophosphamide 24 h prior to sacrifice or 1 μmole/kg benzo(a)pyrene in each of four daily doses prior to sacrifice and served as positive controls. The Ames Salmonella assay of the unconcentrated urine after 1, 3, and 7 weeks and concentrated urine after 7 weeks exposure to diesel exhaust did not significantly vary from clean air controls. In the micronucleus test, and metaphase analysis, cyclophosphamide produced a strong positive response and the 7 week diesel exposure was not different from clean air controls.     

Benzo[a]pyrene metabolism in mice exposed to diesel exhaust: II. Metabolism and excretion

In this study we examined the effect of diesel exhaust (DE) exposure on in vivo metabolism of benzo[a]pyrene (BaP). DE-exposed and unexposed A/Jax mice of group B were instilled intratracheally with ³H-BaP. At each time point of 2, 24, and 168 h after instillation five mice were killed and the liver, lungs, and testes were removed and frozen. Aliquots of the organs were homogenized in 2 ml water and each received 3 volumes of cold ethanol. Radioactivity in supernatant and precipitate was measured. The supernatant extracts were subjected to HPLC analysis on ALOX-T and on Zorbax ODS. The ALOX-T method was a modification of Autrup's procedure for conjugate assay (Biochem. Pharmacol.28, 1727, 1979). Fractions were (a) free BaP; (b) nonconjugated primary metabolites; (c) sulfate conjugates; (d) glucuronides, glutathiones, and other conjugates. By 2 h after instillation primary metabolites were found in liver and lung, but very little was conjugated. The unconjugated BaP was mainly in the form of free BaP and phenolic metabolite(s). The lungs of DE-exposed mice had less capacity to dispose of “bound” BaP 1 week after instillation.     

Detection and average content levels of carcinogenic and mutagenic compounds from the particulates on diesel and gasoline engine mufflers

Carcinogenic and mutagenic compounds, which were extracted from the particulates that adhered to inner surfaces of diesel and gasoline engine mufflers, were quantified by the series method of Soxhlet extraction, liquid-liquid partition, thin-layer chromatography, and spectrofluorometry. Mutagenic activity of their neutral and acidic fractions was tested in the improved Ames assay by the preincubation method with Salmonella typhimurium TA98 in the presence and absence of metabolic activation system (S-9 mix). The average content levels (μg/g tar) of polycyclic aromatic hydrocarbons from gasoline engine cars were greater than those from diesel engine vehicles. However, the levels of nitro derivatives of PAHs and polycyclic quinones from the diesel engines were greater than from the gasoline engines. Mutagenic activity of the diesel acidic fraction was the highest among the diesel and gasoline fractions, and was significantly higher in the absence of the S-9 mix. Furthermore, the relative value (R_{c = 0}) of infrared absorption of carbonyl stretching vibration to that of methylene asymmetric stretching vibration of the diesel acidic fraction was the highest among the diesel and gasoline fractions. These results strongly suggest that highly direct-acting mutagens in the acidic fraction are at higher levels in diesel emission particulates than those from gasoline, and that these mutagens are carboxylic acid, aldehyde, and alcohol derivatives of PAHs and NPAHs.     

Mutagenic and carcinogenic potency of extracts of diesel and related environmental emissions: Two-stage carcinogenesis in skin tumor sensitive mice (SENCAR)

Skin tumors can be induced by the sequential application of a subthreshold dose of a carcinogen (initiation phase), followed by repetitive treatment with a noncarcinogenic tumor promoter. There is a very good dose-response relationship between the induction of the number of papillomas per mouse at early times (10 to 20 weeks) by either tumor initiators and promoters and the final carcinoma incidence after a longer latency (20 to 50 weeks) in SENCAR mice. This system not only can be used to determine the tumor initiating and promoting activities of a compound but if the agent is given repeatedly by itself one can also determine if it is a complete carcinogen, i.e., if it has both tumor initiating and promoting activity. In addition, if the agent is given concurrently with a known complete carcinogen or a tumor initiator one can also determine if the agent has cocarcinogenic or cotumor initiating activity or even possibly anticarcinogenic activity. Likewise, if the agent is given concurrently with a known tumor promoter one can determine if the agent has copromoting or antipromoting activity. Using the SENCAR skin carcinogenesis system we have undertaken the determination of the skin carcinogenic, cocarcinogenic, tumor initiating and promoting activities of various diesel emission particle extracts as well as for comparative purposes, standards such as benzo(a)pyrene and 12-0-tetradecanoylphorbol-13-acetate and extracts of emissions from a gasoline engine, roofing tar, coke oven and cigarette smoke condensate. Most of the studies are still in progress but some preliminary data is available on the comparative tumor initiating activities of the various samples at 14 weeks. Caterpillar diesel and cigarette smoke condensate were essentially without activity, whereas the Mustang gasoline catalyst and Olds diesel gave extremely low values although they were slightly above background. Roofing tar, coke oven and Nissan Diesel all gave moderate activity at high doses (1 to 10 mg) but when compared to benzo(a)pyrene were relatively low values.     

Diesel particulate extracts in bacterial test systems

The Ames bacterial mutagenicity test system was used to evaluate parameters which may affect the mutagenic activity of diesel particulate extracts. The optimal extraction conditions, extractability of mutagens by simulated biological fluids and the effect of collection method were investigated. The role of solvent was examined by extracting diesel particles with methanol, acetone, cyclohexane, ethyl acetate, n-hexane, dichloromethane, benzene and a benzene-ethanol mixture. Of these, the dichloromethane extract exhibited the highest activity in the Ames test, although methanol yielded the largest extractable mass. Diesel particles were also extracted by dimethyl sulfoxide (DMSO) and four other simulated biological fluids for 48 h at 25, 37, and 45°C to study the effects of temperature. The mutagenic activity of the DMSO extract began to decline at temperatures higher than 37°C after 8 h of incubation. Fetal calf serum was the only simulated biological fluid which eluted mutagenic activity from the particles. No activity was detected in the 0.5% bovine serum albumin, simulated lung surfactant and saline extracts. Diesel particles collected by electrostatic precipitation (ESP) and filtration were studied. The mutagenic activities of both extracts were comparable when expressed as revertants per mg of particle. After the extracts were separated into nine fractions by a solvent partitioning scheme, the majority of the activity was found in the neutral-nonpolar II, neutral polar, strong acid and weak acid fractions. The acid salt fraction from the ESP sample was inactive. These results demonstrate that differences in the extraction conditions can result in differences in the mutagenic activity of diesel particulate extract. Since the mutagens in the extracts are not readily extractable by simulated biological fluids, the question of bioavailability of mutagens in diesel particles must be considered in the final assessment of their potential effects in biological systems and organisms.     

In vivo detection of mutagenic effects of diesel exhaust by short-term mammalian bioassays

Male Chinese hamsters were exposed to diesel exhaust and clean air for six months at the Center Hill Facility of the U.S. Environmental Protection Agency in Cincinnati, Ohio. The animals were kept in specially constructed inhalation chambers and exposed to clean air or diesel exhaust for eight hours daily. The animals were sacrificed and slides prepared to study the mutagenic effects of diesel exhaust by four in vivo short term mammalian bioassays. Sperm morphology bioassay revealed a 2.67-fold increase in sperm abnormalities in the animals exposed to diesel exhaust as compared to those exposed to fresh air. Micronucleus bioassay revealed a 50% increase in the number of micronuclei in polychromatic erythrocytes obtained from animals exposed to diesel exhuast. However, no increase in sister chromatid exchange or chromosomal abnormalities was observed in bone marrow cells of animals treated with diesel exhaust. During these studies a decrease in mitotic index was observed in animals treated with diesel exhaust.     

Mutagenic and carcinogenic potency of extracts of diesel and related environmental emissions: In vitro mutagenesis and oncogenic transformation

Extracts from emissions of four diesel engines, a gasoline engine and three related environmental samples were tested in four in vitro assay systems designed to detect carcinogenic or mutagenic activity of chemicals. Samples from three of four diesel extracts, the gasoline engine, and all three related samples were positive in an enhancement of viral transformation assay. Two diesel samples, the gasoline engine extract and extract from coke oven emissions were positive for mutation induction in Chinese hamster ovary cells. Only the gasoline engine extract and the coke oven sample were positive in a DNA fragmentation assay using alkaline sucrose gradients. Experiments using chemical transformation of Syrian hamster embryo cells as an assay method have not been completed.     

Human dietary exposure to polycyclic aromatic hydrocarbons: Results of the second French Total Diet Study

In the frame of the second French Total Diet Study (TDS), the 15 + 1 EU priority polycyclic aromatics hydrocarbons (PAHs) were analyzed in 725 foodstuffs habitually consumed by the French population, using gas chromatography coupled to tandem mass spectrometry, after pressurized liquid extraction and purification on PS-DVB stationary phase. The highest PAH concentrations recovered in foodstuffs corresponded to the following contributors: chrysene (25.7%), benzo[b]fluoranthene (15.0%) and benz[a]anthracene (9.0%) whereas the lowest concentrations were those of dibenz[a,h]anthracene, 5 methylchrysene and dibenzo[a,h]pyrene (below 2.0%). By food groups, the current highest levels of total PAH were detected in mollusks and crustaceans, followed by the different oil based products. To estimate French population's exposure, contamination data were combined with national individual food consumption data. Mean daily exposure to the sum of benzo[a]pyrene, benz[a]anthracene, chrysene and benzo[b]fluoranthene (PAH4) was estimated to be 1.48 ng/kg bw/day in adults and 2.26 ng/kg bw/day in children. The main contributors to PAH exposure for adults are fats, bread and dried bread products followed by crustaceans and mollusks. The margin of exposure (MOE) approach indicates that exposure to PAHs through food is not a major health problem for French consumers.     

A ranking index to characterize polynuclear aromatic pollutants in environmental samples

This study investigated the use of a screening procedure to provide a ranking index (RI) for characterizing polynuclear aromatic (PNA) species in atmospheric samples. The ranking procedure employs a cost-effective and rapid screening technique based on synchronous luminescence spectroscopy. The efficacy and usefulness of the ranking procedure are demonstrated by comparing the RI values with data expressed in terms of the benzene-soluble standard, benzo[a]pyrene values, and the total content of fourteen PNA compounds.     

Diesel soot: Mutation measurements in bacterial and human cells

Both hot pipe and dilution chamber samples of the exhaust from a diesel (Oldsmobile 350) engine have been collected, extracted with methylene chloride and those extracts have been tested for mutagenicity in forward mutation assays in human lymphoblasts and S. typhimurium. In the absence of a metabolic activation system, the extract was significantly mutagenic to the bacteria in the range of 0 to 30 μg/ml, but introduced no mutations in human cells at concentrations up to 200 μg/ml under the same conditions of assay medium. However, when assayed in the presence of a postmitochondrial supernatant derived from rat liver, the the soot extracts were significantly mutagenic to both bacteria and human cells in the range of 50–100 μg/ml. Fractionation of the soot extract on the basis of polarity by sequential elution from a silicic acid column permitted concentration of the mutagenic activity in the alkane/toluene eluate, as determined by bacterial assays. Preliminary characterization of this fraction and preliminary studies of pure compounds leads us to suspect the alkyl substituted phenanthrenes as representing at least a significant fraction of the mutagenic activity of this alkane/toluene eluate.     

Evaluation of techniques used in the preparation of diesel extract samples for mutagenicity studies

Diesel exhaust particles were used to compare methods and techniques used in the preparation of particulate matter for microbial mutagenesis testing. Investigated in this study were extraction, concentration, and solvent exchange methodologies as they affected recovery of mutagenic material from diesel samples using a Salmonella typhimurium plate incorporation assay. Solvent removal methods applicable for use in determining the mass concentration of extracts were also evaluated. Results indicated that particle samples Soxhlet extracted with dichloromethane yielded higher levels of mutagenic activity than did comparative samples utilizing sonication. No difference was seen between rotary evaporation or Kuderna-Danish macro concentration of extracts to volumes > 50 mL. In comparison of micro concentration techniques to volumes < 10 mL, vortex evaporation was found to be more efficient than a modified micro Kuderna-Danish method in recovery of mass and mutagenicity. Solvent exchanged samples were found to yield higher recoveries of mutagenic activity than samples taken to dryness and then reconstituted in the bioassay solvent. A dry mass weighing procedure utilizing desiccation was found to be more acceptable than either the use of an infrared heat lamp or nitrogen blowdown for solvent removal.     

Enhanced susceptibility to infection in mice after exposure to dilute exhaust from light duty diesel engines

A series of experiments was conducted in which groups of mice were first exposed for various durations to diluted exhaust from light duty diesel engines and then briefly to an infectious aerosol generated by nebulizing cultures of a bacterial pathogen (Streptococcus). Typically, postinfection mortality was significantly greater in groups exposed to exhaust than in their corresponding control groups exposed to purified air only. Data of recent diesel and of past diesel- and catalyst-treated gasoline engine exhaust experiments suggest a somewhat greater excess mortality from (enhanced susceptibility to) bacterial infection in mice exposed to diesel exhaust than in those exposed to catalytic gasoline exhaust. Limited data on acute tests of NO₂ and acrolein vapor alone suggest that the infectivity-enhancing effect of diesel exhaust could be accounted for in large part by these components. Exposures to diesel exhaust, NO₂, or acrolein did not enhance the mortality response to a viral pathogen (A/PR8-34).     

Shorter sperm telomere length in association with exposure to polycyclic aromatic hydrocarbons: Results from the MARHCS cohort study in Chongqing,China and in vivo animal experiments

It has been well demonstrated that polycyclic aromatic hydrocarbons (PAHs) can cause reproductive toxicity, and shorter telomere length in sperm may be one of the factors causing male infertility. However, whether exposure to PAHs is associated with sperm telomere length (STL) has never been evaluated. The present study aimed to assess the potential association between PAHs exposure and STL, and to explore potential biomarkers that may predict the effects of low-level exposure to PAHs on human sperm. Questionnaires and biological samples were collected from 666 volunteers participating in the Male Reproductive Health in Chongqing College Students (MARHCS) cohort study in 2014. Semen parameters were measured for 656 participants, while urinary PAH metabolites, STL and sperm apoptosis were successfully measured for 492, 444 and 628 participants, respectively. The linear regression analysis revealed that increased levels of urinary 1-hydroxypyrene (1-OHPyr) and 1-hydroxynapthalene (1-OHNap) were associated with decreased STL (− 0.385; 95% CI, − 0.749, − 0.021 for 1-OHPyr; and − 0.079; 95% CI, − 0.146, − 0.011 for 1-OHNap). The significant negative associations remained after adjusting for potential confounders. However, no significant associations were observed between urinary PAH metabolites and semen quality or sperm apoptosis. We also administrated rats with benzo[a]pyrene (B[a]P; 0, 1, 5, and 10 mg/kg) for 4 weeks and found shorter STL and decreased telomerase expression in germ cells in a dose-dependent manner. In conclusion, environmental exposure to some PAHs may be associated with decreased human STL, and the in vivo animal results also demonstrate the adverse effects of B[a]P on telomere of male germ cells.     

红枫湖地表水中多环芳烃的分布及来源

将固相微萃取与气相色谱联用，对贵阳红枫湖水样中16种美国环境保护署优控的多环芳烃进行分析。结果表明：红枫湖水中16种多环芳烃总量为0167 1~0336 4 μg/L，与国内其它水系相比，湖中存在多环芳烃轻度污染。7种（萘、荧蒽、苯并(b)荧蒽、苯并(k)荧蒽、苯并(a)芘、茚并(1,2,3-cd)芘和苯并(ghi)苝）多环芳烃的总量未超出中国城市供水行业对多环芳烃规定的限值，但作为饮用水源，红枫湖水中的苯并(a)芘含量已超出我国标准GB3838-2002中生活饮用水地表水源地的苯并(a)芘限值，并且苯并(a)蒽、〖JX-*9〗〖SX（B-25x〗〖HT7，5”〗艹〖〗〖HT6”，5”〗屈〖HT5”〗〖SX）〗〖JX*9〗、苯并(b)荧蒽、苯并(k)荧蒽、苯并(a)芘、茚并(1,2,3-cd)芘的含量也超过了美国环境保护署地表水水质标准限值。通过多环芳烃特征参数的比值，分析了红枫湖水中多环芳烃的污染来源。污染源分析表明，湖中多环芳烃的主要来源为燃烧源，包括木材、煤以及化石燃料的燃烧，同时也有一部分多环芳烃是来源石油类物质的输入.