Assessment of the potential reproductive and subchronic toxicity of EDS coal liquids in Sprague-Dawley rats

Comparison of PAC and MOAH for understanding the carcinogenic and developmental toxicity potential of mineral oils

The carcinogenicity and developmental toxicity of unrefined mineral oil is related to its 3-7 ring polycyclic aromatic compounds (PAC) content. Therefore, refining operations focus on the targeted removal PAC from mineral oil that may contain aromatics of low toxicological concern. There are thus, two types of aromatic substances in mineral oil: hazardous and non-hazardous. The first type consists of 3-7 ring PAC which may be naked (unsubstituted) or lowly alkylated. The second type or non-hazardous consists of 1-7 ring aromatics with high degree of alkylation or lack of bay or fjord regions. Although these are toxicologically different, they may both elute in the same fraction when using chromatography. To understand how these two aromatic types are related we have assessed the entire mineral oil refinement process by measuring total mineral oil aromatic hydrocarbons (MOAH) content by chromatography next to regulatory hazard tests which focus on 3-7 ring PAC. MOAH content is positively correlated to its molecular weight resulting in aromatic content bias for high viscosity substances. Hazard to 3-7 ring PAC is best controlled by the validated IP346 or modified Ames test. We explain the concept of high vs low alkylation by shortly reviewing new data on alkylated PAC.

Results of Chronic Dietary Toxicity Studies of High Viscosity (P70H and P100H) White Mineral Oils in Fischer 344 Rats

Two-year dietary studies were conducted to determine the chronic toxicity and its reversibility, and the carcinogenicity of P70(H) and P100(H) white mineral oils in Fischer-344 rats (F-344). The studies were identical in design and followed the Organization for Economic Cooperation and Development, Guidelines for Testing Chemicals, Guideline 453, 1981. Additional endpoints evaluated were: (1) extent of mineral hydrocarbon deposition in liver, kidneys, mesenteric lymph nodes, and spleen of female rats at 3, 6, 12, 18 and 24 months, and (2) reversibility of effects following cessation of exposure. Dietary concentration were 60, 120, 240, and 1, 200 mg/kg/day, adjusted periodically to account for bodyweight changes. Study results were consistent with preceding subchronic studies. No treatment-related mortality, neoplastic lesions, or changes in clinical health, hematology, serum chemistry, or urine chemistry were evident in any group administered either white oil. Statistically significant higher food consumption was noted in the 1, 200 mg/kg group males and females exposed to either white oil and statistically significant higher body weights were noted in the 1, 200-mg/kg males during the latter portion of the P100(H) study. Higher mesenteric lymph node weights were accompanied by increased severity of infiltrating histiocytes. This occurred to a greater extent with the P70(H) than the P100(H) oil. No other histopathology of significance was observed. Mineral hydrocarbons were detected in the liver following exposure to either oil. Maximal concentrations of mineral hydrocarbons in the liver were similar with both oils but occurred more rapidly with the P70(H) oil. Liver mineral hydrocarbon content returned to near-background levels during the reversibility phase. In conclusion, lifetime exposer of F344 rats to P70(H) and P100(H) white oils resulted in only minimal findings and with no consequence to clinical health. Thus, under the conditions of these studies, the No Observable Adverse Effect Level (NOAEL) for these studies was considered to be 1, 200 mg/kg/day.

Oral and Dermal Administration of Clarified Slurry Oil to Male C3H Mice

Clarified slurry oil (CSO) is the heavy residual material produced in the fluidized catalytic cracking unit of a petroleum refinery. CSO was adm in istered via gavage or dermal application to male C3H mice (10/ group) at a dose of 1000 mg/ kg/ d, 5 d/ wk, for up to 10 weeks. Interim sacrifices were performed after 2, 4, 8, and 10 weeks of treatment for orally exposed and control mice; dermally exposed mice were sacrificed after 10 weeks. Fifty percent of the “dermal” mice died prior to scheduled sacrifice. Deaths observed in the “oral” group were attributed to apparent misintubations, not to CSO exposure. Mice exposed orally for 2, 4, or 8 weeks (but not 10 weeks) exhibited significantly increased absolute (A) and relative (R) liver weights, while all “oral” mice (including those sacrificed after 10 weeks) had significantly decreased A and R thymus weights when compared to controls. “Dermal” mice had significantly increased R liver weights and significantly decreased A and R thymus weights. After 2 weeks most “oral” mice showed hepatocyte hypertrophy. A few mice showed liver necrosis. Liver findings increased in incidence and severity until 8 weeks of exposure. After 10 weeks, the liver of most “oral” mice showed the same or less discern ible morphologic pathology than was observed after 2 weeks. At 10 weeks, “dermal” mice showed the previously described liver effects, except that liver necrosis was severe, and evidence of fibrosis was observed. In summary, although CSO was hepatotoxic, “oral” mice showed signs of liver recovery after 10 weeks of exposure despite continued treatment. Thus, CSO appears to be more toxic to mice when administered dermally than orally. Humans are more likely to come into contact with these lipids by dermal rather than by oral exposure.

Comparative pharmacokinetic and disposition studies of [1-14C]1-eicosanylcyclohexane, a surrogate mineral hydrocarbon, in female Fischer-344 and Sprague-Dawley rats

White oils or waxes [mineral hydrocarbons (MHCs)] with substantial levels of saturated hydrocarbons in the range of C18 to C32 have produced hepatic microgranulomas and lymph node microgranulomas (also referred to as histiocytosis) after repeated administration to female Fischer-344 (F-344) rats. Female Sprague-Dawley (S-D) rats are less sensitive to these MHC-induced hepatic and lymph node effects. Studies reported herein characterized the pharmacokinetics and disposition of a representative C-26 MHC, [1-(14)C]1-eicosanylcyclohexane ([(14)C]EICO), in these two rat strains. Female F-344 and S-D rats were administered by oral gavage either a high (1.80 g/kg) or a low (0.18 g/kg) dose of MHC in olive oil (1:4, v/v) containing [(14)C]EICO as a tracer. Blood, urine, feces, liver, and mesenteric lymph nodes (MLNs) were analyzed for [(14)C]EICO and (14)C-metabolites. After the high dose, F-344 rats had a higher blood C(max) of [(14)C]EICO, a longer time to C(max), and a greater area under the systemic blood concentration-time curve from zero to time infinity compared with S-D rats. After the low dose, F-344 rats displayed a unique triphasic blood concentration-time profile, meaning two distinct C(max) values were observed. Fecal excretion was the major route of [(14)C]EICO elimination for both rat strains (70-92% of the dose). S-D rats eliminated the majority of [(14)C]EICO metabolites recovered in the urine by 16 h (8-17% of the dose), whereas F-344 rats did not excrete the same amount until 72 to 96 h. Beyond 24 h, a greater level of [(14)C]EICO was recovered in livers of F-344 rats; at 96 h, 3 and 0.1% of the dose was retained in livers of F-344 and S-D rats, respectively. The major urinary metabolites of EICO in both rat strains were identified as 12-cyclohexyldodecanoic acid and 10-cyclohexyldecanoic acid. Based on the pharmacokinetic parameters and disposition profiles, the data indicate inherent strain differences in the total systemic exposure, rate of metabolism, and hepatic and lymph node retention of [(14)C]EICO, which may be associated with the different strain sensitivities to the formation of liver granulomas and MLN histiocytosis.

Developmental toxicity of carbon black oil in mice

BACKGROUND

Carbon black oil (CBO) is a refinery side-stream product used to produce asphalt and other commercial products. CBO contains several classes of hydrocarbons, several of which are known to exhibit systemic and gestational toxicities, making this mixture a candidate for causing reproductive toxicity.

METHODS

Swiss-Webster mice were administered CBO (300, 350, 400 mg/kg/day) via oral gavage in a dosage volume of 10 microl/g body weight on gestation days (GD) 6-15. Uterine contents were evaluated on GD 18.

RESULTS

Treatment with CBO at all dosage levels resulted in a high frequency of maternal clinical symptoms and a decrease in maternal weight gain. Decreased fetal viability was observed, manifested as a decrease in viable implants and, in a high percentage of treated dams, as early resorption of the entire litter. A significant reduction in fetal weight was also observed. However, neither structural malformations nor developmental delays in ossification were observed in any of the living offspring. To minimize maternal toxicity, the dosage range was lowered (100, 200, 300 mg/kg/day), and the concentration was adjusted such that the volume administered to each dam was decreased by 20%. In this trial, the only maternal effect observed was an increase in maternal liver weight at 200 and 300 mg/kg. The fetal lethality effects observed previously were reduced substantially. Nevertheless, the frequency of resorption among all treatment groups was higher statistically than in controls.

CONCLUSIONS

These data support the hypothesis that CBO is reproductively toxic in Swiss-Webster mice at oral doses of >/=100 mg/kg/day.

Granulomas in the livers of humans and fischer rats associated with the ingestion of mineral hydrocarbons: A comparison

Ninety-day feeding studies were conducted in Fischer 344 rats using a series of highly refined mineral hydrocarbons which included mineral oils and waxes representative of those used in consumer products and food applications. The series included materials which had been refined by oleum or hydrogenation. The materials tested were representative of the range of carbon chain lengths, molecular weights, and viscosities which are currently in use. Findings revealed the presence of granulomatous lesions in the liver and histiocytosis in the lymph nodes. Some mineral hydrocarbons did not induce any lesions; others induced relatively minor effects; and a low melting point wax induced the largest lesions in both liver and mesenteric lymph nodes, with inflammation and areas of focal necrosis in the livers. The majority of lesions reported were associated with the highest dose levels used. These studies are in contrast to studies in Sprague-Dawley rats in which comparable doses did not induce similar lesions, indicating marked strain variability. Lipogranulomas associated with the ingestion of mineral oil have been reported in humans. The comparative morphology of the lesions seen in the Fischer rat study and those observed in the human are discussed and differences are highlighted. The lesions in the human are not believed to progress to lesions of clinical significance. The pathogenesis of the lesions induced in Fischer rats and in humans is discussed and it is concluded that the majority, if not all of the lesions, in the rats are of no significance for humans. The possibility that a small proportion of cases of granulomatous hepatitis in humans may represent an atypical response to mineral hydrocarbons may need further investigation. Copyright 1998 Academic Press.

Lack of carcinogenicity of medium-viscosity liquid paraffin given in the diet to F344 rats

The carcinogenicity of medium-viscosity liquid paraffin was examined in Fischer 344 rats. Groups of 50 males and 50 females were given the material at dietary doses of 0 (control), 2.5 or 5% for 104 wk. Slight increases in food consumption and body weight were observed in both sexes of the 5% group. However, no significant differences between the control and treated groups were noted with regard to clinical signs, mortality and haematology findings. A variety of tumours developed in all groups, including the control group, but all the neoplastic lesions were histologically similar to those known to occur spontaneously in F344 rats, and no statistically significant increase in the incidence of any tumour type was found for either sex in the treated groups. Granulomatous inflammation in the mesenteric lymph nodes, considered to be a reaction to paraffin absorption, was observed with similar incidence and severity in both sexes of the 2.5 and 5% groups. Thus, it is concluded that under the present experimental conditions, the high dose, about 2000-200,000 times higher than the current temporary acceptable daily intake, does not have any carcinogenic potential in F344 rats. Furthermore, granulomatous inflammation observed in mesenteric lymph nodes were not associated with any development of neoplastic lesions.

Ninety-day feeding study in Fischer-344 rats of highly refined petroleum-derived food-grade white oils and waxes

Subchronic 90-day feeding studies were conducted in male and female Fischer-344 (F-344) rats on highly refined white mineral oils and waxes representative of those used for food applications. The goal was to help clarify the mixed results found in other toxicity studies with laboratory animals. Seven white oils and 5 waxes were fed at dietary doses of 20,000, 2,000, 200, and 20 ppm and compared with control groups on untreated diet; toxicity was assessed at 90 days and also after a reversal period of 28 days and/or 85 days. Higher molecular-sized hydrocarbons (microcrystalline waxes and the higher viscosity oils) were without biological effects. Paraffin waxes and low- to midviscosity oils produced biological effects that were inversely related to molecular weight, viscosity, and melting point; oil type and processing did not appear to be determinants. Biological effects were more pronounced in females than in males. Effects occurred mainly in the liver and mesenteric lymph nodes and included increased organ weights, microscopic inflammatory changes, and evidence for the presence of saturated mineral hydrocarbons in affected tissues. Inflammation of the cardiac mitral valve was also observed at high doses in rats treated with paraffin waxes. Further studies are required to elucidate the mechanism for the responses observed and the relevance of these inflammatory responses in the F-344 rat to other species, including humans.

A toxicological review of topical exposure to white mineral oils

White mineral oils have a long history of safe use by humans in orally ingested and topically applied products. A re-evaluation of the use of certain mineral hydrocarbons in the preparation of food items by regulators in the UK, however, has prompted additional safety studies and a critical assessment of the toxicological effects of white mineral oils. As white mineral oils are present in many topically applied drug and non-drug products, it is of interest to review the toxicological effects of mineral oil produced by this route of exposure. Specifically, the concern regarding the safety of white mineral oils has arisen, in part, from results of subchronic (e.g 90 day) feeding studies that reported the presence of granulomas in liver and histiocytosis in mesenteric lymph nodes of Fischer 344 rats after oral ingestion of select white mineral oils. In contrast to these subchronic oral studies, repeated topical exposure to white mineral oils has not been found to produce liver granulomas, histiocytosis in the mesenteric or other lymph nodes, or any local or systemic toxicity including tumour formation in Fischer 344 rates, C3H mice, New Zealand White rabbits or beagle dogs at similar or higher exposures (mg/kg/day). On the basis of these findings and reports on negligible epidermal penetration of topically applied white mineral oils, there is no evidence of any hazard identified for topical exposure to white mineral oils at any dose in multiple species. This conclusion is supported by the long and uneventful human use of white mineral oils in drug and non-drug topically applied products.

Subchronic feeding study of four white mineral oils in dogs and rats

Subchronic 90-day feeding studies were conducted on four highly refined white mineral oils to determine any potential for toxicity in Long-Evans rats (20 per sex per dose level) and beagle dogs (4 per sex per dose level). Each oil was fed at dietary dose levels of 300 ppm and 1500 ppm (w/w). No treatment-related effects of toxicological importance were detected in daily observations of general health or in periodic assessments of food consumption and body weight, hematology, serum clinical chemistry, and urinalysis. Observations in dogs suggested that the white oils produced mild laxative effects. Gross and histopathologic examinations, as well as measurements of organ weights, did not reveal any macroscopic or microscopic changes which could be due to treatment. In addition, special staining by Oil Red O of liver, mesenteric lymph nodes, spleen, gastrointestinal tract, stomach, and kidneys indicated no evidence of oil or lipid deposition. A special re-examination of tissues from female and male rats, in response to more recent conflicting data from the Fischer 344 strain, found no histopathologic signs of macrophage accumulation and/or microgranuloma formation in liver, spleen, or mesenteric lymph nodes. These data indicate that repeated exposure to relatively high levels of white mineral oils in the diets does not produce significant subchronic toxicity in Long-Evans rats or beagle dogs.

Comparative 90-day feeding study with low-viscosity white mineral oil in Fischer-344 and Sprague-Dawley-derived CRL:CD rats

A 90-day study was conducted to compare the effects of dietary administration of a food-grade white oil in female Fischer-344 (F-344) and Sprague-Dawley-derived (CRL:CD) rats. Animals were fed a low viscosity (15 mm2/sec at 40 degrees C) paraffinic white oil (designated as P 15[H]) at 0, 0.2, or 2.0% of the diet for 30, 61, or 92 days. There were no significant adverse clinical observations or unscheduled deaths. In the F-344 rats, occasional treatment-related changes were seen in hematology and clinical chemistry parameters. At necropsy, mesenteric lymph nodes were enlarged, and there was an increase in absolute and relative liver, mesenteric lymph node, and spleen weights as compared to controls. Histopathologic effects included hepatic and mesenteric lymph node microgranulomas and mesenteric lymph node histiocytosis. In CRL:CD rats, the only effects noted were accumulations of chronic inflammatory cells in the liver at the high dose only, without the formation of discrete microgranulomas. A dose-related increase in mineral hydrocarbon (MCH) material in the liver and mesenteric lymph nodes was observed in both F-344 and CRL:CD rats. Although increased, liver MhC content was significantly less (approximately 50%) in CRL:CD rats than the levels detected in the F-344 rats. Mesenteric lymph node MHC levels did not differ significantly between the strains. This study demonstrated strain differences among rats in histopathologic effects of white oil, with the CRL:CD rat essentially showing no response compared to the F-344 rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicology of coal liquefaction products: an overview

Repeated exposure to coal liquefaction products produces a broad range of systemic effects. Among these, growth suppression, anaemia, leucocytosis and other haematological disorders are most prominent. Bone marrow, liver and kidney are the target organs affected by treatment. The effects are more severe with heavy distillates and male rats are more sensitive than females. Other changes included increased serum transaminases, alkaline phosphatase and cholesterol. Depending on the route of administration, the skin or lung may also be affected. Inhalation exposure produces the most severe changes, and oral exposure the least. Distillates containing N-PAHs and sulphur-containing PAHs are also more biologically active. Teratological effects were only observed if animals were exposed to the heavy distillate. Similarly, heavy distillates have mutagenic or carcinogenic properties. Teratological effects, as well as mutagenicity and carcinogenicity, of the coal liquefaction distillates seem to be linked to their PAH content, especially the N-PAHs. From the data presented in this review, it should become evident that the potential effects of coal liquefaction products on human health could be severe, especially with long-term exposure. Limited information exists on the occupational effects to coal liquefaction materials because most of the work to date has been with pilot plants. Careful and good judgement is required in order to extrapolate data from pilot plants to commercial-scale production. Experience in health effects of workers in the petroleum industry and coke-oven operations can serve as a guide for the implementation of industrial hygiene programmes for coal liquefaction operations. These programmes include engineering controls, health education, personal monitoring and hygienic practices, medical surveillance and long-term epidemiology studies, and they should be implemented to make coal liquefaction a healthy and environmentally sustainable industry.

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.