Comparison of in-vitro and in-vivo studies with coal liquids from the SRC-II process

Coal liquids obtained from the SRC-II process and fractions prepared from these liquids have been assayed in a number of in vivo and in vitro systems for biological activity. The in vitro systems includes: (1) the standard Ames Salmonella typhimurium reverse mutation assay, (2) the S. typhimurium fluctuation test; (3) forward mutation assay in S. typhimurium (8-Ag) test; (4) prophage induction (INDUCTEST); (5) Syrian hamster ovary (SHE) cell transformation assay; and (6) Chinese hamster ovary (CHO) cell mutation assay. In addition, both initiation/promotion (I/P) and chronic skin-painting assays were used as measures of tumorigenesis. In general, materials shown to be carcinogenic in the chronic skin-painting assay were also positive in the other assays. The failure of the Ames assay to respond to the neutral polycyclic aromatic hydrocarbon (PAH) fraction of SRC-II heavy distillate (HD) was a notable exception. Quantitatively, the Ames assay was more sensitive to nitrogen-containing compounds (particularly primary aromatic amines) and less sensitive to mixtures of PAH. The mammalian systems, both in vitro and in vivo, showed greater responses to the neutral PAH than to the nitrogen-containing compounds. Activity in all biological systems increased with increasing boiling point of the material tested. The I/P assay ranked the materials studied in the same order as did the chronic skin-painting assay; however, the results of the two assays diverged quantitatively, particularly for certain distillate cuts. Despite the lack of quantitative agreement between the in vitro microbial and in vivo skin-painting assays, the in vitro assays remain valuable screening tools for complex mixtures. Sufficient information now exists to qualify the use of the in vitro assays for complex mixtures and to increase their reliability

Chemical characterization and genotoxic potential related to boiling point for fractionally distilled SRC-I coal liquids

This report summarizes selected research efforts oriented toward ameliorating the genotoxic potential of direct coal liquefaction materials through modification or optimization of process conditions. The studies described were conducted to evaluate the utility of optimized distillation for coal liquids from the SRC-I process. SRC-I process solvent was distilled into 50/sup 0/F-range boiling point (bp) cuts. Analysis of amino-PAH (APAH) showed that mutagenic APAHs containing 3 or more rings were found primarily in fractions boiling above 750/sup 0/F. Three microbial tester strains were used to screen for genetically active agents in the SRC-I distillate bp cuts. Reverse mutation with the Ames tester strain TA98 demonstrated that mutagens were concentrated in the bp cuts boiling above 700/sup 0/F. For this tester strain most of the genetic activity in these distillates was attributable to chemical fractions enriched in APAH having 3 or more rings. Mutagenicity data obtained with TA98 was in good agreement with sk in carcinogenesis results from the mouse-skin initiation/promotion (in vivo) test system. The strongest response in the forward mutation assay did not occur in the most carcinogenically active fractions. Results of initiation/promotion experiments used to measure the relative potency of bp cuts as initiators of mouse skin carcinogenesis again showed that fractions boiling above 750/sup 0/F. Compounds reaching their highest concentrations in the highest boiling and most carcinogenically active cut included known carcinogens such as benzo(a)pyrene and dimethyl benzanthracene. Thus, all biomedical test results indicate that consideration should be given to conducting distillation so as to minimize, in the distillate product, the concentrations of those biologically active compounds found in cuts boiling above 700/sup 0/C

Chemical and biological effects of heavy distillate recycle in the SRC-II process

Recent work from the Merriam Laboratory continuous coal liquefaction units shows that heavy distillate from the SRC-II process can be recycled to extinction, and hence a distillate product boiling entirely below 310/sup 0/C (590/sup 0/F) (or other selected boiling points) is feasible. In these runs distillate yield was not reduced; gas make was unaffected; and hydrogen consumption was increased only slightly, in keeping with the generally higher hydrogen content of lighter end products. Total distillate yield (C/sub 5/-590/sup 0/F) was 56 wt %, MAF coal in runs with subbituminous coal from the Amax Belle Ayr mine. Product endpoint is well below 371/sup 0/C (700/sup 0/F), the temperature above which coal distillates appear to become genotoxic; and the product was shown to be free of mutagenic activity in the Ames test. Chemical analyses showed both the < 270/sup 0/C (< 518/sup 0/F) and the < 310/sup 0/C (< 590/sup 0/F) distillates to be essentially devoid of several reference polycyclic compounds known to be carcinogenic in laboratory animals. Tests for tumorigenic or carcinogenic activity were not carried out on these materials. However, a comparison of chemical data from the Merriam heavy distillate samples with data on the other SRC-II distillates where carcinogenesis or tumorigenesis data is available leads to the expectation that < 371/sup 0/C (< 700/sup 0/F) materials from the Merriam Laboratory will have greatly reduced tumorigenic and carcinogenic activity in skin painting tests. Other studies suggest the product should be more readily upgraded than full-range (C/sub 5/-900/sup 0/F) distillate

Photodegradation of mutagens in solvent-refined coal liquids

The purpose of this investigation was to evaluate any changes in the chemical composition and microbial mutagenicities of two representative solvent-refined coal (SRC) liquids as a function of exposure time to sunlight and air. This information was desired to assess potential health hazards arising from ground spills of these liquids during production, transport and use. Results of microbial mutagenicity assays using Salmonella typhimurium TA98, conducted after exposure, showed that the mutagenicities of both an SRC-II fuel oil blend and an SRC-I process solvent decreased continuously with exposure time to air and that the decrease was accelerated by simultaneous exposure to simulated sunlight. The liquids were exposed as thin layers supported on surfaces of glass, paper, clay or aluminum; but the type of support had little effect on the results. The contrast between these results and the reported increases of mutagenesis in organisms exposed simultaneously to coal liquids and near-ultraviolet light suggested that short-lived mutagenic intermediates, e.g., organic free radicals, were formed in the liquids during exposure to light. The highest activities of microbial mutagenicity in the SRC liquids were found in fractions rich in amino polycyclic aromatic hydrocarbons (amino PAH). After a 36-hour exposure of the fuel oil blend to air in the dark, the mutagenicity of its amine-rich fraction was reduced by 65%; whereas a 36-hour exposure in the light reduced the mutagenicity of this fraction by 92%. Similar rates of reduction in mutagenicity were achieved in exposures of the process solvent. The mutagenicities of other chemical fractions remained low during exposure