Teratogenicity following inhalation exposure of rats to a high-boiling coal liquid

On days 12-16 of gestation pregnant rats were exposed to heavy distillate (HD), the highest-boiling material derived from the solvent refined coal-II (SRC-II) process, and the litters were examined at day 21. Adverse biological effects were observed in the group of animals exposed to an aerosol concentration of 0.66 mg 1-1 [1.8 microgram, mass medium aerodynamic diameter (MMAD)]; groups of animals exposed to lower aerosol concentrations (0.084 and 0.017 mg 1-1) were largely unaffected. Embryo lethality during mid- and late gestation appeared attributable to the coal liquid exposure. Fetuses from pregnant rats in the high exposure group were smaller in weight and length than fetuses from control animals, and skeletal ossification was reduced. Increased incidences of small lungs and cleft palate were observed in fetuses from the high exposure group. Pregnant rats in the high-exposure group gained less weight than controls during gestation; the reduced weight gain was accounted for by the reduced size of the fetuses and placentas. Even though maternal body weight (exclusive of the products of conception) was unaffected by the exposure, the weights of the maternal thymus, lung and spleen were altered in the high exposure group.