Tritium: Some Effects of Continuous Exposure In Utero on Mammalian Development

Pregnant rats were maintained at constant body activities of tritiated water ranging through 1-100 μCi/ml of body water throughout pregnancy. These activities provided total-body doses to the embryo and fetus of approximately 0.3-30.0 rads/day. Regardless of the activity level of progeny were grossly normal with respect to external and internal morphology. Statistically significant findings at various HTO levels included: micrencephally, sterility, stunting, litter size reduction, and increased resorption. Decreases in the absolute and relative weights of a number of term fetus organs were closely proportional to dose. Histologically all organs were normal except the gonads. Tritium incorporation into fetal organs was directly proportional to, and 20-30 percent of, the average maternal body water HTO activity prevailing during gestation. Postnatal observations showed that by 180 days stunting was no longer evident in irradiated females but persisted in males irradiated at 50-100 μCi/ml. Within 270 days 5 tumors had arisen in irradiated animals compared to 1 in a control animal. Continuous exposure to an HTO activity of 1 μCi/ml during pregnancy was found to be consistent with the production of offspring in which the only deviations from the controls noted were an increased length and a slight increase in weight of the liver and heart evident only in neonates.