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 in pregnant rats. t-DCE was administered by inhalation 6 hr daily on Days 7-16 of gestation (the day copulation was confirmed was termed Day 1 of gestation) at exposure levels of 0, 2000, 6000, or 12,000 ppm. The offspring were then examined on Day 22 of gestation. Overt maternal toxicity was expressed as a significant reduction in weight gain at 12,000 ppm and in feed consumption at 6000 and 12,000 ppm. During the exposure period, lacrimation and stained periocular hair, and signs of ocular irritation, were observed in all groups. In addition, increased incidences of alopecia, lethargy, and salivation were observed in the high-dose dams. Significant increases in the mean number of resorptions per litter were seen in the litters of dams exposed to 6000 and 12,000 ppm of t-DCE; however, these values are within the range of historical controls and not considered to be treatment related. The mean combined and female fetal weights were significantly reduced 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 pattern seen at higher doses, were seen at 2000 ppm. Thus, marginal maternal toxicity was seen at 2000 ppm and exposures to 6000 ppm t-DCE or higher caused frank maternal toxicity while the fetus was affected only at 12,000 ppm. Therefore, t-DCE is not considered to be uniquely toxic to the rat conceptus.