Developmental toxicity study in rats exposed dermally to clarified slurry oil for a limited period of gestation.

Clarified slurry oil (CSO, CAS number 64741-62-4), a refinery stream produced by processing crude oil, is a developmental toxicant when administered dermally throughout gestation to pregnant rats. The manifestations of developmental toxicity observed included embryolethality and growth retardation; evidence of teratogenicity was limited, and not conclusive. The present study was undertaken to further explore the teratogenic potential of CSO. In an attempt to limit embryolethality and thereby promote detection of terata, CSO was administered once daily for a limited period of gestation [gestation days (GD) 9-12], via dermal application, to pregnant Sprague-Dawley rats at doses of 0, 10, 100, and 1000 mg/kg. All animals were sacrificed on GD 20. Detailed examination of the dams was performed. Due to the screening nature of this investigation, fetal evaluations were limited to body weight measurements, external examinations, and evaluation of select visceral endpoints. In the dams exposed to CSO, significant decreases in body weight [absolute and gain (GD 9-13, GD 0-20)] and in the amount of food consumed were observed at 100 and 1000 mg/kg. Additional evidence of maternal toxicity observed at 1000 mg/kg included decreased absolute and relative thymus weights, increased absolute and relative liver weights, and aberrant serum chemistry. Ingestion of the test material was evident at the high dose. Developmental toxicity was observed at 1000 mg/kg and included increased embryolethality, decreased body weight, and anomalous development (cleft palate, brachydactyly, edema). Although a low incidence of abnormal fetal development was observed at 100 mg/kg, it was not conclusive that the alterations were due to CSO exposure. It is likely that three to seven-ring polycyclic aromatic compounds present in CSO were responsible for the toxic effects observed.