Prenatal developmental toxicity studies on fumes from bitumen in the rat

The prenatal developmental toxicity of bitumen fume was tested by nose-only inhalation in the rat. The fumes for exposure were collected from the headspace of a storage tank filled with a bitumen corresponding in composition to an anticipated worst-case occupational exposure. The composition of these fumes was compared to actual paving site fumes to ensure its representativeness for workplace exposures. In a dose-range-finding study male and female rats were exposed to 0, 103, 480 or 1043 mg/m³ of fume (as total organic mass), for 6 h/day during 20 days post conception (p.c.). Dose-related effects on body weight and lungs were observed in the mid- and high-dose groups. In the main study, dams were exposed to 0, 52, 151 and 482 mg/m³ of fume, for 6 h/day during 19 days p.c. The maternal NOAEL was 52 mg/m³. In the high-dose group treatment-related effects on body weight (gain), food consumption, lung weights, and histopathological changes in lungs and larynx were observed. In the mid-dose group only histopathological changes in the larynx and lungs were found. The NOAEL for prenatal developmental toxicity was 151 mg/m³ based on reduced fetal weight in the high-dose group (482 mg/m³). However, these changes are most likely a consequence of the maternal toxicity, in particular the reduction of maternal body weight gain by 26 % as compared to control. Nose-only exposure to bitumen fumes in concentrations up to 482 mg/m³ from days 1-19 p.c. did not induce any significant fetal anomalies.