Abstract
Heterocyclic aromatic hydrocarbons are, together with their un-substituted analogues, widely distributed throughout all environmental compartments. While fate and effects of homocyclic PAHs are well-understood, there are still data gaps concerning the ecotoxicology of heterocyclic PAHs: Only few publications are available investigating these substances using in vitro bioassays. Here, we present a study focusing on the identification and quantification of clastogenic and aneugenic effects in the micronucleus assay with the fish liver cell line RTL-W1 that was originally derived from rainbow trout (Oncorhynchus mykiss). Real concentrations of the test items after incubation without cells were determined to assess chemical losses due to, e.g., sorption or volatilization, by means of gas chromatography-mass spectrometry. We were able to show genotoxic effects for six compounds that have not been reported in vertebrate systems before. Out of the tested substances, 2,3-dimethylbenzofuran, benzothiophene, quinoline and 6-methylquinoline did not cause substantial induction of micronuclei in the cell line. Acridine caused the highest absolute induction. Carbazole, acridine and dibenzothiophene were the most potent substances compared with 4-nitroquinoline oxide, a well characterized genotoxicant with high potency used as standard. Dibenzofuran was positive in our investigation and tested negative before in a mammalian system. Chemical losses during incubation ranged from 29.3% (acridine) to 91.7% (benzofuran) and may be a confounding factor in studies without chemical analyses, leading to an underestimation of the real potency. The relative potency of the investigated substances was high compared with their un-substituted PAH analogues, only the latter being typically monitored as priority or indicator pollutants. Hetero-PAHs are widely distributed in the environment and even more mobile, e.g. in ground water, than homocyclic PAHs due to the higher water solubility. We conclude that this substance class poses a high risk to water quality and should be included in international monitoring programs.
Highlights
One of the key processes that built the foundation of the organic chemical industry in Germany and many other European countries in the 19th century was the distillation of coal tar-oil, by which common building-blocks for numerous syntheses were derived, e.g. for textile dyes [1]
While polycyclic aromatic hydrocarbons (PAHs) were already extensively investigated with regard to fate, biodegradation, toxicology and ecotoxicology [7,8,9], only limited knowledge exists for the hetero-PAHs
Many studies focused on few individual compounds and toxicological effects, e.g. mutagenicity of carbazoles [10] or chromosome aberrations induced by quinolines [11]
Summary
One of the key processes that built the foundation of the organic chemical industry in Germany and many other European countries in the 19th century was the distillation of coal tar-oil, by which common building-blocks for numerous syntheses were derived, e.g. for textile dyes [1]. To further fill the data gap mentioned above, we report on the first comparative study in which the clastogenic and aneugenic effects of heterocyclic PAHs typically found at tar-oil contaminated sites were investigated using the micronucleus assay with the permanent rainbow trout liver cell line RTL-W1 [19].
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