Systemic toxicity of the heavy fraction of a coal coprocessing product in male rats following subchronic dermal exposure

Abstract

The systemic toxicity of a coal coprocessing product [heavy gas oil II (HGOII)] following subchronic, dermal exposure in male Sprague-Dawley rats was investigated. HGOII was applied to the dorsal skin daily at doses of 8.7, 20.8, 50.0, or 120.0 mg/kg body weight (bw) for 13 weeks. Another group of rats treated with a medium boiling coal liquefaction product (CLP) served as positive controls. Growth suppression and decreased food consumption were noted in the groups exposed to HGOII at 20.8 mg/kg and higher, and to CLP starting at the third week of treatment. Relative liver, kidney, and brain weights in the 20.8 mg/kg HGOII group and up were higher than those of the control. Increased spleen weight was observed in all HGOII-treated groups. CLP treatment also caused increased relative kidney and brain weights. Serum cholesterol was elevated in the HGOII-treated groups starting at 8.7 mg/kg while increased uric acid and lactate dehydrogenase were observed at 20.8 mg/kg and up. Decreased erythrocyte, hemoglobin, and platelet counts were observed at 20.8 mg/kg and higher. All HGOII-treated groups had elevated reticulocytes. These biochemical and hematological changes were not observed in the CLP-treated group. Mild to marked histological changes were observed in the thyroid, thymus, liver, spleen, and bone marrow of HGOII groups. In contrast, morphological changes were relatively mild in CLP-treated animals. Data from the present study demonstrated that the hematological endpoints were sensitive to the liquid fuels and that HGOII was more toxic than CLP. Based on the growth rate and biochemical, hematological, and morphological changes, the no observable adverse effect level for HGOII is judged to be below 8.7 mg/kg bw in the rat.