Developmental toxicology investigation of tellurium.

The developmental toxicity of tellurium was evaluated in Crl Sprague-Dawley rats and New Zealand white rabbits by means of standard segment II-type studies. Groups of pregnant rats were fed a diet containing 0, 30, 300, 3000, or 15,000 ppm of tellurium on Days 6 through 15 of gestation (microscopic detection of sperm in a smear of vaginal contents considered as Day 0), and artificially inseminated rabbits were fed a diet containing 0, 17.5, 175, 1750, and 5250 ppm of tellurium during Days 6 through 18 of gestation (day of insemination considered as Day 0). Signs of maternal toxicity were observed during the treatment period in a statistically significant and dose-related manner at dietary concentrations of 300 ppm and greater in rats and 1750 ppm and greater in rabbits. Exposure of these pregnant rats and rabbits to tellurium had no effect upon reproduction as measured by pregnancy rate, litter size, dead or resorbed implantations, or fetal sex ratio. Both skeletal (primarily skeletal maturational delays) and soft tissue malformations (primarily hydrocephalus) were noted in the offspring of pregnant rats exposed to the highest levels (3000 and 15,000 ppm) of tellurium. Rabbit fetuses of the highest dosage group (5250 ppm) had a slightly elevated evidence of skeletal delays and nonspecific abnormalities. Since maternal toxicity was observed at dosages that did not affect the developing conceptus, there were no indications of unique developmental susceptibility upon exposure of pregnant rats or rabbits to tellurium.