Developmental toxicity of carbon black oil in mice

Background: Carbon black oil (CBO) is a refinery side-stream product used t o produce asphalt and other commercial products. CBO contains several class es of hydrocarbons, several of which are known to exhibit systemic and gest ational toxicities, making this mixture a candidate for causing reproductiv e toxicity. Methods: Swiss-Webster mice were administered CBO (300, 350, 400 mg/kg/day) via oral gavage in a dosage volume of 10 mu l/g body weight on gestation d ays (GD) 6-15. Uterine contents were evaluated on GD 18. Results: Treatment with CBO at all dosage levels resulted in a high frequen cy of maternal clinical symptoms and a decrease in maternal weight gain. De creased fetal viability was observed, manifested as a decrease in viable im plants and, in a high percentage of treated dams, as early resorption of th e entire litter. A significant reduction in fetal weight was also observed. However, neither structural malformations nor developmental delays in ossi fication 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 wa s 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 lethalit y effects observed previously were reduced substantially. Nevertheless, the frequency of resorption among all treatment groups was higher statisticall y than in controls. Conclusions: These data support the hypothesis that CBO is reproductively t oxic in Swiss-Webster mice at oral doses of greater than or equal to 100 mg /kg/day. (C) 2000 Wiley-Liss, Inc.