"Microwave Irradiation Microwave anechoic chamber was used for all irradiations; the animals were exposed in the far field of a standard-gain horn antenna, at 2,450 MHz. The radiation was produced by a Lucz 58 generator (USSR) of maximum power output 150 W, and fed to the antenna through a standard wave guide. Field distribution within the chamber was measured with a broadband isotropic radiation monitor (Narda Microwave Corp., Plainview, NY, USA). Temperature and humidity of the chamber were contolled during the expositions, and equaled to 22 _+ 1 ~ C and 65 + 5 ~, respectively. For irradiations, mice restrained in a plastic cage, 10 mice per cage, were placed at the fixed area of the chamber where the power levels of the incident microwave energy equaled to 5, 10 or 15 mW/cm 2, for different irradiation regiments. Exposures were carried out for 2 h daily, 6 days per week, for a total of 1, 2, 3 or 6 months. In additional experiments the specific absorption rate (SAR) of microwave energy in murine cadavers was tested by measuring the increase of body temperature in relation to field power density. By extrapolation it was established that under the conditions used SARs of 2, 4 and 6 mW/g were found for the respective power densities of 5, 10 and 15 mW/cm z. Experimental All mice were divided into six experimental groups of 100 animals each. Mice in groups 1 and 2 were exposed to benzopyrene treatment and were simultaneously irradiated with 5 mW/cm 2 (group 1) or 15 mW/cm 2 (group 2) of microwave radiation for a total of 6 months. Groups 3- 5 were composed of animals irradiated with 10 mW/cm 2 for 1 (group 3), 2 (group 4) or 3 months (group 5) prior to the beginning of benzopyrene treatment, as above. Control animals were exposed to benzopyrene treatment for 6 months and sham-irradiated with microwaves, i. e. mice were placed in anechoic chamber for 2 h daily for the respective periods of time (1, 2, 3, or 6 months), but the generator was turned off throughout the whole session of "irradiation". The process of the development of skin cancer was assessed in all groups of animals according to the 7-range macroscopical scale every 2 weeks, and the following indices were calculated: (a) mean cancer development time (MCDT), i. e. mean period of time in which all animals developed skin cancer to the step 4 on the scale; (b) cancer development time 50 (CDTso), i. e. the period of time in which 50 ~ of mice developed a 4th-step skin cancer; (c) mean survival time 50 (MSTs0), i.e. the period of time in which 50 of the animals in the group were killed by the tumour.

Statistical Analysis The experimental points recorded every 2 weeks during 12 months were approximated to the straight line (the least square method) and the Pearson's correlation coefficient was calculated for each group. MCDT, CDTs0 and MST~o were calculated from the above lines 9 Statistical significance of the differences (P< 0.01) between groups was tested by the g ~ test (number of animals with developed tumours or survival rate in all groups at time of CDT~o or MSTso, respectively) ."

BALB/c mice, male - RF-EMF 1 month - followed by 2,4-benzopyrene

HAWC