Developmental Toxicity of Inhaled trans-1,2-Dichloroethylene in the Rat

The developmental toxicity of trans-1,2-dichloroethylene (t-DCE),a component of certain Freon cleaning agents, was examined inpregnant rats. t-DCE was administered by inhalation 6 hr dailyon Days 7–16 of gestation (the day copulation was confirmedwas termed Day 1 of gestation) at exposure levels of 0, 2000,6000, or 12,000 ppm. The offspring were then examined on Day22 of gestation. Overt maternal toxicity was expressed as asignificant reduction in weight gain at 12,000 ppm and in feedconsumption at 6000 and 12,000 ppm. During the exposure period,lacrimation and stained periocular hair, and signs of occularirritation, were observed in all groups. In addition, increasedincidences of alopecia, lethargy, and salivation were observedin the high-dose dams. Significant increases in the mean numberof resorptions per litter were seen in the litters of dams exposedto 6000 and 12,000 ppm of t-DCE; however, these values are withinthe range of historical controls and not considered to be treatmentrelated. The mean combined and female fetal weights were significantlyreduced in the litters of dams exposed to the highest concentration(12,000 ppm) of t-DCE. Marginal effects on feed consumption,unaccompanied by other changes and reflective of the patternseen at higher doses, were seen at 2000 ppm. Thus, marginalmaternal toxicity was seen at 2000 ppm and exposures to 6000ppm t-DCE or higher caused frank maternal toxicity while thefetus was affected only at 12,000 ppm. Therefore, t-DCE is notconsidered to be uniquely toxic to the rat conceptus.