||Health Effects Research Lab., Research Triangle Park, NC. Developmental Toxicology Div. ;National Inst. of Standards and Technology, Boulder, CO. ;ManTech Environmental Technology, Inc., Research Triangle Park, NC.
Virtually continual exposure to970-MHz microwaves in circularly-polarized waveguides was used to elicit fetal responses in Sprague-Dawley rats during gestation. Two hundred fifty rats were exposed to microwave radiation at whole-body averaged specific absorption rates (SAR) of 0.07, 2.4, or 4.8 W/kg, or concurrently shamirradiated for 22 h/day from the 1st through the 19th day of gestation. At SAR of 4.8 W/kg, only fetal body weight was significantly altered (-12%, P=.012). Two of twelve rats died during the exposure at SAR of 4.8 W/kg. Bred, but non-pregnant, rats that were exposed at SAR of 4.8 W/kg had significantly lower body weight gain than sham-irradiated rats; similar lower gain is assumed to have occurred in the pregnant rats exposed at SAR of 4.8 W/kg, and whose fetuses were significantly smaller. The authors conclude that continual gestational exposure at SAR of 4.8 (but not 2.4 or lower) W/kg induces fetal alterations. Apparently, deleterious maternal effects are associated with these fetal changes. Although colonic temperature was not measured in these rats, it is expected that exposure at 4.8 W/kg was hyperthermal.