Mutagenicity of products from coal gasification and liquefaction in the Salmonella/microsome assay

Mutagenicity of mild gasification products in Salmonella typhimurium

Mild gasification is a coal-conversion technology that is currently under development in order to help meet future energy needs. 7 products from this process were assayed for mutagenic activity in the pre-incubation variant of the Salmonella assay (Ames test) using both DMSO and Tween 80 as sample solvents. Significant mutagenic activity was detected only in the wide-boiling-point composite materials, and the amount of this activity was found to be dependent on the solvent utilized. The highest number of revertants detected were on TA98 and its O-acetyltransferase over-producing derivative, YG1024, in the presence of the S9 microsomal fraction. Aromatic amines were suggested as a possible source of the mutagenic activity elicited. An examination of the liquid and tar phases of one composite material (MG-120) indicated that the mutagenic activity was restricted to the tar phase.

Mutagenicity of algal metabolites of benzo(a)pyrene for Salmonella typhimurium

The metabolism and growth effects of benzo(a)pyrene (BaP) were studied using a freshwater green alga, Selenastrum capricornutum. Algal cultures were incubated under gold light with BaP added at concentrations of 40, 160, 400, and 1,200 micrograms/liter for the periods of 1-4 days. The metabolites and BaP were identified and quantified from ethyl acetate extracts of both algal cells and incubation medium. The ethyl acetate extracts were evaluated for genotoxicity using a micro-volume Salmonella typhimurium forward mutation assay with resistance to 8-azaguanine for selection. This assay detected the presence of small quantities of BaP and was particularly sensitive to the mutagenicity of BaP diols. Of those extracts prepared from algae and medium from cultures exposed to 400 micrograms BaP/liter (10 micrograms/25 ml culture), only algal cell extracts from one day's growth were mutagenic. In cultures exposed to 1,200 micrograms BaP/liter (30 micrograms/25 ml culture), mutagenic materials were produced or persisted in both algae and media throughout the 4-day incubation. The observed mutagenic response can be attributed in part to the presence of unmetabolized BaP or to BaP diols.

Mutagenic and cytogenetic analyses of organic extracts of simulated runoffs from model coal piles

The use of coal as a fuel in utility and other industries in the United States is increasing. Typically, these utilities store their coal outdoors in large piles, and rainfall on the piles produces a runoff containing hazardous inorganic and organic materials. Four coals of varying sulfur contents, all used for fuel in the United States, were tested. Organic materials were extracted from simulated runoffs of model coal piles and were tested for mutagenicity with a Salmonella/microsomal assay and for clastogenicity and cytotoxicity in Chinese hamster ovary cells. The extracts of the high-sulfur coals and the lignite were more mutagenic and clastogenic than extracts from the low-sulfur coal.

Detection of photomutagens in natural and synthetic fuels

The contribution of non-ionizing radiation to synfuel-related skin carcinogenesis is largely unknown. We have employed a modification of the Salmonella histidine reversion test system to detect photomutation by various fuel substances. For photomutation testing we washed and resuspended cells in buffer, irradiated with 'visible' light in the presence of test substance, and removed aliquots after various light exposures for assay by the plate incorporation method. We have assayed photomutagenicity and microsome-mediated mutagenicity of a crude petroleum, a shale oil, and coal hydrogenation process intermediates. Photomutagenicity was studied using one concentration of each oil; peak revertants per plate for most oils tested were relatively similar to revertants per plate with microsomal activation of the same oil at the corresponding concentration. The shale oil was an exception to this pattern: with light activation, peak revertant numbers per plate were approximately 10 times the value observed with microsomal activation. The samples tested are not assumed to be representative of all petroleums, shale oils or coal oils. Our results do suggest that environmental radiation may be a significant factor in synfuel-related skin carcinogenesis and that photomutagens may be different from enzyme-activatable promutagens.

Mutagenic and toxic activity of environmental effluents from underground coal gasification experiments

Using bacterial bioassays, we have screened for the presence of mutagens and toxins in extracts from groundwater, and in tar from product gas, at the sites of two Lawrence Livermore National Laboratory (LLNL) in situ experiments: Hoe Creek II and Hoe Creek III. The sites exhibited different potential biological hazards, suggesting that different gasification processes may represent different human health concerns. We found that mutagens are present in groundwater, persist for at least 2 yr after gasification has been terminated, and show a change in activity with time-possibly in parallel with changes in chemical composition. Preliminary evidence suggests that the mutagens in groundwater are quinoline and aniline derivatives, while the toxins in groundwater may be phenolic compounds. In tar from the product gas, the organic bases and neutrals were found to be genotoxic in both bacterial and mammalian cells; the neutral compounds appear to be the major mutagenic health hazards. Neutral compounds constitute most of the tar (85-97 wt%) and were mutagenic in both the bacterial and mammalian cell assays. Tar in the gas stream may be a problem for the aboveground environment if gas escapes through fractures in the overburden. Because it is mutagenic and induces chromosomal damage to mammalian cells, the tar may represent a disposal problem as well. However, it is difficult to assess tar quantitatively as a health hazard because its mutagenic activity is low, possibly due to contaminants in the neutral fraction that act to suppress mutagenicity.