"Exposure chamber

Exposure system consisted of a rectangular transverse electromagnetic (TEM) cell. As described earlier [8], it is made up of metallic section containing a flat metal strip center conductor. The mice were placed in the center of the chamber. The field or power density in the plane midway between the center conducting strip and the chamber wall is fairly uniform [9].

Mice were housed in a rectangular cage made of PlexiglasÒ having the dimensions 32 9 10 9 9 cm. Two mice were exposed simultaneously for 2 h/day for 3 days a week for a period of 16 weeks at 112 MHz AM at 16 Hz. Small circular holes were drilled at equidistance in every cage to keep it aerated during the exposure. Plexiglas has a low dielectric constant so as to simulate the electric char- acteristics as close to those of free space. By proper sep- aration of animal cages, the non-uniformities in the exposure field are minimized [

10]."

"Experimental design

The animals were divided into different control and experimental groups (n = 18) [14].

Group A1 (n = 18): control (sham exposure), group A2: topical (dorsal) application of single dose of 100 lg 7,12-dimethylbenz(a)anthracene (DMBA) in 100 ll ace- tone and kept for 16 weeks. Dosage of DMBA was selected as per previous report with a slight modification [14], group A3: mice were treated with a single dose of 100 lg DMBA in 100 ll acetone and after 2 weeks of gap they were exposed to 2 h/day, 3 days a week for a period of 16 weeks at 112 MHz AM at 16 Hz with the power density of 1.0 mW/cm2. Group A4: mice were treated with a single dose of 100 lg DMBA in 100 ll acetone and 2weeks later they were exposed to 2.45 GHz radiation at power density of 0.34 mW/cm2, 2 h/day, 3 days a week for a period of 16 weeks. Group A5: mice were exposed to 112 MHz AM at 16 Hz with the power density of 1.0 mW/cm2 2 h/day, 3 days a week for a period of 16 weeks. Group A6: this group was exposed to 2.45 GHz pulsed wave radiation with the power density of 0.34 mW/cm2, 2 h/day, 3 days a week for a period of 16 weeks. Group A7: mice received a single dose of DMBA (100 lg/100 ll acetone per ani- mal) on the dorsal side of the animal. After 2 weeks gap croton oil (1% oil in 100 ll acetone/animal) was applied topically twice a week for 16 weeks. Tumor observation and body weight were conducted at weekly intervals in each group.

Croton oil is a known tumor promoter. The active principle of croton oil is 12-0-tetradecanoyl phorbol- 13-acetate. This treatment was given to find out whether a single dose of DMBA followed by croton oil treatment develops any tumor or not (a positive control).

The skin was examined under light to visualize the tumors. The size of the macroscopically visible skin tumors was measured by calipers."

Swiss albino mice, male - 112 MHz, DMBA

HAWC