The Hazards to Health in the Hydrogenation of Coal

Studies on the mutagenicity of mild gasification products of coal and their subfractions by the Salmonella/microsomal assay

Mild gasification of coal is a technology being developed in the United States in order to upgrade lower rank coals and facilitate their use in coal-burning electric generation plants. Thirteen coal-derived mild gasification products from different coal sources and processing conditions have been examined for their potential biohazards. The mutagenicity of these samples was tested with the Ames Salmonella/microsomal assay. Two solvents, dimethyl sulfoxide (DMSO) and polyoxyethylene-sorbitan monooleate (Tween 80), were used to dissolve samples in a manner to facilitate their interaction with the test organisms. The results showed that 9 of the 13 samples displayed mutagenic activity in test strains TA98 and/or TA100 with or without metabolic activation, whether dissolved in Tween 80 or DMSO. Five mutagenic and two nonmutagenic samples were class-fractionated into basic, acidic, nonpolar, and polar neutral subfractions to examine their class-related mutagenic activities. Results of the testing of subfractions of the five mutagenic and one nonmutagenic samples showed mutagenic activity in at least the nonpolar neutral fraction. The subfractions of the another nonmutagenic sample did not display any mutagenic activity. Chemical characterization of the subfractions revealed the existence of aromatic hydrocarbons in certain subfractions, which may be responsible for the mutagenic activity of the coal-derived mild gasification products.

Epidermal carcinogenesis studies of EDS liquids

A series of liquids representing different potential design options or operating configurations for the EDS direct coal liquefaction process* were evaluated for skin cancer potential. All of the samples that contained substantial amounts of material boiling above 370 degrees C were active dermal carcinogens; tumor yields were near 100% and median times to tumor development generally ranged from 30 to 40 weeks. Two liquids that boiled below ca. 200 degrees C were tested and each produced one squamous cell tumor. These data suggested that high-boiling-point, coal-derived liquids are likely to be relatively potent dermal carcinogens; whereas low-boiling-point liquids do not possess significant carcinogenic potential. Based on a comparison of the carcinogenic potency data, liquids produced by the EDS process apparently do not present a significantly greater dermal carcinogenic hazard than other coal-derived materials of similar boiling range.

Developmental toxicity of EDS recycle solvent and fuel oil

Direct coal liquefaction is one of several technologies currently under development as alternative means to produce liquid fuels. Relatively high levels of polycyclic aromatic hydrocarbons are present in distillate fractions boiling above approximately 370 degrees C. Coal-derived liquids containing substantial amounts of material from this boiling range were genotoxic in in vitro tests and carcinogenic in mouse skin. Some of the liquids were also teratogenic in rodents. The present report describes studies which assessed the potential effects of 2 coal-derived liquids, recycle solvent (nominal boiling range 200-427 degrees C) and an experimental industrial fuel oil (nominal boiling range 204-538 degrees C) on prenatal development in the rat. The test materials were produced by the EDS direct coal liquefaction process and contained substantial amounts of material boiling above 370 degrees C. Test materials were administered by gavage to pregnant female Sprague-Dawley rats from days 6 to 19 of gestation (G). Animals were sacrificed on day 20G and the uterine contents were removed and examined. Results of both studies were similar. The number of live fetuses declined in a dose-related manner, and there was evidence of intrauterine growth retardation in fetuses which survived to day 20G. Statistically significant effects were noted at doses which did not appear to be maternally toxic. The frequency of malformation was not significantly elevated in either study; however, a thorough evaluation of this endpoint was precluded by embryo lethality at the high doses. It was apparent that both of the EDS liquids examined affected prenatal survival and growth. However, in contrast to studies of other coal-derived liquids, there was no evidence of teratogenic effects at non-toxic doses.

Epidermal carcinogenesis studies of synthetic fossil fuel materials in mice

Skin tumor response in mice to solvent fractions of heavy distillate (HD) from a solvent-refined coal (SRC-II) process indicated that the basic tar and neutral tar were the most carcinogenically potent fractions. Assays of another SRC-II coal liquid that had been fractionally distilled indicated that the carcinogenicity of this material for mouse skin is due to that portion boiling above 371 degrees C (700 degrees F), and that the carcinogenic potency of the material increased with boiling point. Samples of the 399-427 degrees C (750-800 degrees F) distillate were nitrosated to destroy primary aromatic amines and were chemically fractionated to assess the carcinogenicity of chemical class fractions of these complex mixtures. Data from these assays indicated that neutral polycyclic aromatic hydrocarbons (PAH) and nitrogen-containing polycyclic aromatic compounds (NPAC) both contribute to the carcinogenicity of this distillate.

Evaluation of the teratogenic potential and reproductive toxicity of coal-derived naphtha

Liquids which are derived from coal liquefaction processes and boil above approximately 250 degrees C have induced terata in rats. However, few studies have addressed the teratogenic potential of coal liquids which boil below 250 degrees C. The present studies evaluated the reproductive and teratogenic potential of EDS hydrotreated naphtha, a refined coal liquid boiling below 177 degrees C. These studies were conducted by inhalation exposures with Sprague-Dawley rats at target vapor concentrations of 0.2, 1.0, and 5.0 g/m3. The first study assessed teratogenesis. There was no evidence that inhalation exposures for 6 hr per day between Days 6 and 19 of gestation induced maternal toxicity, fetal toxicity, or malformation. In a second study, rats were exposed for 6 hr per day, 5 days per week for 13 weeks, and then mated to assess reproductive toxicity. There was little evidence that inhalation exposure to EDS hydrotreated naphtha adversely affected reproductive performance or fetal development in Sprague-Dawley rats. A low incidence of malformations was observed in treated groups, but these malformations were probably not treatment related.

The phototoxic and allergenic potential of EDS liquids

Liquid fuels derived by direct coal liquefaction may be similar in boiling range and chemical composition to coal tar products. In the past, phototoxicity, an occupational skin disorder, has been associated with coal distillation. Consequently, the phototoxic properties of 5 materials representing the full boiling range of liquids derived from the EDS process were characterized utilizing a guinea pig model. Results with low boiling, coal derived liquids (less than 200 degrees C) were not different from unirradiated controls; however, liquids boiling above 200 degrees C induced phototoxic effects. These results suggest that high boiling EDS liquids may possess phototoxic potential. Differences in the phototoxic activities of liquids of similar boiling range may be related to chemical composition. A study of the allergenic potential of the EDS liquids described above was conducted utilizing the guinea pig maximization test. None of the test materials produced positive responses, suggesting that EDS liquids are low in allergenic potential.

Chemical and toxicological aspects of coal liquefaction and other complex mixtures

Chemists, biologists, and ecologists at Battelle's Pacific Northwest Laboratories are developing a data base to aid engineers in the safe design of coal liquefaction process options. Objectives of this effort have been to identify and evaluate long-term health and environmental issues, evaluate options to permit environmentally acceptable design, and assess risk to man and the environment from deployment of a large-scale coal liquefaction industry. Chemically complex materials produced by various coal liquefaction processes, and under various stages of process design and operating conditions, have been screened for potential health and environmental effects. Biologically active materials have been fractionated and rescreened. Chemical constituents of biologically active fractions have been identified, and the environmental fate of problematic agents is currently being determined. This approach, linking engineering and life sciences research, is also relevant to the development of other energy technologies and industries that produce chemically complex materials. Results indicate that full-boiling-range coal-derived liquids are generally more active than shale oil and petroleum crudes in biological and ecological test systems. Several biologically active agents have been identified, including primary aromatic amines (PAA), polynuclear aromatic hydrocarbons (PAH), and phenols. Some components of coal-derived materials are taken up by biota and metabolized. Hydrotreating, a refining or upgrading process, reduces PAA, PAH, and phenol content, as well as mutagenicity, carcinogenicity, and toxicity of coal liquids. Selective distillation restricts PAA and PAH content, as well as mutagenicity and carcinogenicity to high-boiling-range coal liquids. Other process conditions (i.e., extraction severity, catalyst age, etc.) and environmental factors influence chemical characteristics and biological activity of coal-derived materials. Eliminating toxic input of coal liquids to ecological test systems results in partial system recovery. Recent findings indicate that biological responses to a particular chemical agent vary, depending on whether that material is presented to the organism or environment as a pure compound or in a complex mixture. Thus, results of studies with pure compounds cannot be used alone to predict effects of complex mixtures. The research approach described here provides guidance to solve environmental problems before regulatory agencies require limitations or facility construction is completed, and costs of process changes are higher.(ABSTRACT TRUNCATED AT 400 WORDS)

Skin-tumor initiation activity of coal liquids with different boiling-point ranges

High-boiling coal liquids from the solvent-refined coal-I and -II (SRC-I, -II) processes, respectively, were fractionally distilled. In the case of SRC-I process solvent (PS), 50 degrees F distillation cuts were obtained between 550 and 850 degrees F, while for the SRC-II material, the 50 degrees F cuts were only obtained between 700 and 850 degrees F. These cuts, as well as the parent material, were tested for their ability to initiate skin tumors by applying a single dose (25 mg) to the shaved backs of Charles River female CD-1 mice. After 2 weeks, the mice received twice weekly applications of 5 micrograms of the promoter, phorbol myristate acetate. Only a few tumors were found for SRC-I fractions boiling below 700 degrees F; tumor-initiating activity increased as the boiling point increased. A similar increase in response with increasing boiling point was seen for the SRC-II cuts. The initiating activities for the parent materials were similar to those observed for their respective 800 to 850 degrees F cuts.

Transformation of Syrian hamster embryo cells by synfuel mixtures

Existing Syrian hamster embryo (SHE) cell-transformation assay methods were modified to allow the assay of complex synfuel mixtures. A shale oil, high-molecular-weight, high-boiling distillates from two different solvent-refined coal (SRC) processes, and two crude petroleum samples caused transformation of SHE cells. Chemical fractionation of SRC-II heavy distillate and assay of resultant fractions allowed detection of significant transforming activity in chemical fractions, where such activity had not previously been observed. The polyaromatic-hydrocarbon-enriched fraction, neutral aliphatic hydrocarbon fraction, and neutral tar fraction all showed a positive response in the SHE assay. In addition, we confirmed earlier data showing that both the tar fractions (basic and neutral) and the soluble basic fractions from both SRC processes and shale oil contained genetically active materials.

Initiation/promotion studies with coal-derived liquids

Fractions derived from solvent-refined coal-II (SRC-II) heavy distillate (HD) were tested for their skin tumor initiating activity. Basic (BF), basic tar (BTF), neutral tar (NTF) and polynuclear aromatic (PNA) fractions were prepared from HD by solvent extraction. These fractions were tested for their initiating activities by applying a single dose to the shaved back of male, CD-1 mice (Charles River, Portage, MI). Positive control groups were initiated with either dimethylbenz[a]anthracene (DMBA) or benzo[a]pyrene (BaP). Two weeks after initiation, all mice received twice weekly applications of 5 micrograms of phorbol myristate acetate (PMA) for a period of 24 weeks. Papillomas were noted and recorded for each animal at the time of PMA application. Heavy distillate and its fractions all showed initiating activity. However, the incidence of mice with tumors, the rate of tumor appearance and the total number of tumors varied with the test material. The tumor responses after initiation with HD,NTF and BTF were similar to that found with BaP, but lower than that with DMBA. Somewhat lower activity was found for BF and PNA. Even lower activity was found with a distillate boiling from 800 to 850 degrees F and no activity was found with a 300 to 700 degrees F distillate. These data are in general agreement with the results of long-term, skin painting assays, suggesting that initiation/promotion (I/P) may be useful for studying the tumorigenicity of coal-derived materials.

Evaluation of coal liquefaction technologies by Salmonella mutagenesis

Coal liquefaction materials made by two processes were found to be mutagenic in the Salmonella/microsome assay. Data from this type of in vitro assay can be used in the toxicological assessment of these processes. Such evaluations of the health and environmental impacts of technologies would aid in the development of alternate energy sources.