Mutagenic nitroaromatic compounds have recently been found in photocopies, urban atmosphere, automobile exhaust and wastewater. 1-Nitropyrene (I-NP) is readily formed when pyrene, ubiquitous in the environment, is exposed to nitrogen dioxide in the urban atmosphere or in automobile exhaust, and is highly mutagenic, inducing 449 hisr revertants/plate/nmol from Salmonella typhimurium strain T A98 in the absence of 89 fraction in the Salmonella-microsome test. It is possible to swallow sputum or some food containing I-NP and it would come into contact with the normal bacterial flora. We determined the I-NP nitroreductase activity in environmental and laboratory bacterial strains. We found that the mutagenicity of I-NP mixed with the feces of a healthy man or a culture of anaerobic bacteria was decreased. The product proved to be I-aminopyrene (I-AP), based on its fluorescence spectrum, its mass spectrum, and its characteristic thin layer chromatographic and high performance liquid chromatographic patterns. The I-NP nitroreductase activity of aerobic bacteria was low, but crude extracts from the anaerobic bacteria, i.e., Bacteroidesfragilis, B. thetaiotaomicron, B. oulgatus, Fusobacterium mortiferum, F. nucleatum, Clostridium perfringens, C. sporogenes, Bifidobacterium adolescentis, B. bifidum, Eubacterium lentum, E. limosum, andPeptostreptococcus anaerobius, all easily converted I-NP to I-AP and proportionally decreased the mutagenic activity of I-NP.A simple method for identifying chemical mutagens has been developed: the Ames test (I) measures back mutation in several specially constructed mutants of Salmonella typhimurium his-strains. A homogenate of rat liver 89 fraction is added to the Ames test to approximate mammalian metabolism.I-Nitropyrene (l-NP) is a nitroaromatic compound that is highly mutagenic in the Ames test. One nanomol of I-NP induces 484 hisr revertants/plate from S. typhimurium tester strain T A98 in the absence of 89 mix (21). Moreover, 1,8-dinitropyrene induces 72,900 hisr revertants/plate/nmol from strain TA98 (21). I-NP is more mutagenic than representative carcinogens and mutagens; for example, 2-nitronaphthalene and benzo(a)pyrene induce 8.7 and 121 hist revertants/plate/ nmol, respectively (20). I-NP is also carcinogenic in rats (26).I-NP has recently been detected in photocopies, airborne particles, automobile 993
Wastewater collected from oil-water separating tanks of ten gasoline stations for a year was fractionated into diethyl ether-soluble neutral, acidic, and basic fractions. Mutagenicity of these fractions was measured with Salmonella typhimurium strains TA98 and TA100 in the presence or absence of S9 mix. The neutral fractions showed high mutagenicity in the absence of S9 mix. Each neutral fraction was subjected to high-performance liquid chromatography (HPLC) and fractionated. A 1-nitropyrene(1-NP)-corresponding fraction was collected and analyzed by gas chromatography-mass spectrometry (GC-MS) and HPLC to prove that wastewater contains 1-NP and to quantitate 1-NP in wastewater. GC-MS patterns showed the following molecular and fragment ion peaks of 1-NP: 247, 217, 201, and 189. The amount of 1-NP in 36 samples of wastewater was 4.2-25,600 ng per liter of wastewater, and 1-NP accounted for 0.3-58.5% of the total mutagenicity of the neutral fractions. The other 19 samples of wastewater did not contain any detectable 1-NP. The mutagenicity of wastewater may be due to water from car washing and contamination by used crankcase oil. A Soxhlet extract of crankcase oil used in a gasoline was fractionated into three fractions as above. Mutagenicity was measured with strains TA98, TA100, TA98NR, and TA98/1,8-DNP6 in the absence or presence of S9 mix. The neutral fraction showed the highest mutagenicity with strain TA98 in the absence of S9 mix, and its mutagenicity was decreased in strains TA98NR and TA98/1,8-DNP6. The latter result indicates that the used engine-oil contained 1-NP and dinitropyrenes. Actually, the amounts of 1-NP and 1,6-diNP in used crankcase oil were 138 and 2.0 ng per ml of oil, respectively, and these concentrations accounted for 0.45 and 2.7%, respectively, of the total mutagenicity of the neutral fraction with strain TA98 in the absence of S9 mix. Moreover, the concentrations of 1-NP and 1,6-diNP in used crankcase oil of a diesel engine were 349 and 31 ng per ml of oil, respectively, accounting for 0.9 and 12%, respectively, of the total mutagenicity of the neutral fraction in the same assay system.
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