Developmental toxicities of ethylbenzene, ortho-, meta-, para-xylene and technical xylene in rats following inhalation exposure.

The developmental toxicities of ethylbenzene, o-, m-, p-xylene and technical xylene were studied in Sprague-Dawley rats after inhalation exposure. Animals were exposed to either of these agents at 100, 500, 1000 or 2000 ppm, for 6 h/day, during days 6-20 of gestation. All the agents tested caused maternal toxicity expressed as a reduction in maternal body weight gain at 1000 and 2000 ppm. Decreased corrected weight gain and food consumption were observed at 1000 and 2000 ppm ethylbenzene, o-, m- or p-xylene, and at 2000 ppm technical xylene. No evidence of teratogenic effects was found after exposure to any of these agents up to 2000 ppm. Fetal toxicity evidenced by significant decreases in fetal body weights occurred at concentrations of 500 ppm or greater of o-xylene or technical xylene, and 1000 ppm or greater of ethylbenzene, m- or p-xylene. A significant increase in the mean percentage of fetuses per litter with skeletal variations was also noted at 2000 ppm ethylbenzene, o- and p-xylene. In summary, all tested agents produced developmental toxicity at 1000 and 2000 ppm, concentrations that also produced significant maternal toxicity. With o-xylene and technical xylene, developmental toxicity also occurred at 500 ppm, in the absence of maternal toxic effects. However, the only indication of a treatment-related effect was a slight decrease in fetal weight.