OBJECTIVETo investigate whether exposure to 900 MHz GSM wireless communication signals enhances mammary tumor development and growth induced by low dose dimethylbenz (a) anthracene (DMBA).

METHODSFive hundred female Sprague Dawley (SD) rats were treated with a single dose of 35 mg/kg. DMBA and then divided into 5 groups: one control group without exposure, and 4 groups with exposure in blinded fashion. The specific absorption rates (SAR) were 0, 0.44, 1.33 and 4.00 W/kg for the 4 exposure groups, respectively. Exposure started on the next day after DMBA administration and lasted 4 hours/day, 5 days/week for 26 weeks. Rats were weighted and palpated weekly for the presence of tumors, and killed at the end of 26-week exposure period. All mammary glands were examined histopathologically.

RESULTSThe incidence of mammary carcinoma in sham-exposure group was 37% (37/100). And mammary carcinoma incidences in the other groups of the exposure dose (0.44, 1.33 and 4.00 W/kg) were 25% (25/100), 34% (34/99) and 38% (38/100) respectively. There were no statistically significant differences between sham- and mobile phone microwave-exposed groups. In addition, the histopathological morphology of mammary tumor model in SD rats was observed. By microscopical examination two types of mammary tumor in this model were found, that was malignant or benign one. The former included adenocarcinoma and squamous cell carcinoma, and the latter included adenoma, fibroadenoma and cyst. Sometimes the histopathological morphology of mammary tumor appeared various since several kinds of histopathological features existed in the same individual.

CONCLUSIONThis study does not provide the evidence that 900 MHz GSM microwave exposure might promote DMBA-induced mammary tumor development in rats.