Accelerated development of spontaneous and benzopyrene‐induced skin cancer in mice exposed to 2450‐MHz microwave radiation

Abstract

(S.S., A.S., A.P., M.B., M.J., J.K. W.)C3H/HeA mice with high incidence of spontaneous breast cancer and Balb1c mice treated with 3,4-benzopyrene (BP) (by painting of the skin resulting in the development of skin cancer) were irradiated with 2,450-MHz microwaves (MW) in an anechoic chamber at 5 or 15 mW/cm2 (2 h daily, 6 sessions per week). C3WHeA mice were irradiated from the 6th week of life, up to the 12th month of life. Balb1c mice treated with BP were irradiated either prior to (over 1 or 3 months) or simultaneously with BP treatment (over 5 months). The appearance of palpable tumors in C,H/HeA mice and of skin cancer in BP-treated Balbic mice was checked every 2 weeks for 12 months. Two additional groups of mice were exposed to chronic stress caused by confinement or to sham-irradiation in an anechoic chamber; these served as controls. Irradiation with M W s at either 5 or 15 mW1cmZ for 3 months resulted in a significant lowering of natural antineoplastic resistance (mean number of lung neoplastic colonies was 2.8 f 1.6 (SD) in controls, 6.1 t 1.8 in mice exposed at 5 mW/cmz and 10.8 2 2.1 in those irradiated at 15 mW1 cm2) and acceleration of development of BP-induced skin cancer (285 days in controls, 230 days for 5 mW/cm* and 160 days for 15 mW/cm2). Microwave-exposed C&I/HeA mice developed breast tumors earlier than controls (322 days in controls, 261 days for 5 mW/cmz and 219 days for 15 mWicm'). A similar acceleration was observed in the development of BP-induced skin cancer in mice exposed simultaneously to BP and MWs (285 days in controls, 220 day for 5 mWicmZ and 121 days for 15 mW1cm'). The acceleration of cancer development in all tested systems and lowering of natural antineoplastic resistance was similar in mice exposed to MW at 5 mW/cm' or to chronic stress caused by confinement but differed significantly from the data obtained on animals exposed at 15 mWicm2, where local thermal effects ("hot" spots) were possible.

Survival and cancer in laboratory mammals exposed to radiofrequency energy

“…Liddle et al [1994], on the other hand, found an effect on lifespan at 6.8 W/kg only and not at 2 W/kg. Szmigielski et al [1982] exposed mice for 2 h/day and stated that neither dose rate range (2-3 and 6-8 W/kg) caused an increase in rectal temperature, but this information does not agree with the experience of other investigators. Liddle et al [1994], for example, estimated a rectal temperature increase of about 0.8 8C in mice exposed individually at 6.8 W/kg for 1 h/day, one-half the exposure time used by Szmigielski et al No significant rise in body temperature of the mouse would be expected at the lower dose rate of 2 W/kg under the experimental conditions described by Liddle et al [1994], but this may not have been true for mice that could huddle together when exposed in groups of 10 per cage [Szmigielski et al, 1982].…”

“…Szmigielski et al [1982] exposed mice for 2 h/day and stated that neither dose rate range (2-3 and 6-8 W/kg) caused an increase in rectal temperature, but this information does not agree with the experience of other investigators. Liddle et al [1994], for example, estimated a rectal temperature increase of about 0.8 8C in mice exposed individually at 6.8 W/kg for 1 h/day, one-half the exposure time used by Szmigielski et al No significant rise in body temperature of the mouse would be expected at the lower dose rate of 2 W/kg under the experimental conditions described by Liddle et al [1994], but this may not have been true for mice that could huddle together when exposed in groups of 10 per cage [Szmigielski et al, 1982]. Concerns about temperature levels in exposed mice, uncertainty in dosimetry data due to exposure of 10 mice per cage, and effects at RF exposure levels that reportedly did not increase body temperature have contributed to the controversy surrounding the Szmigielski et al study since it was published over 20 years ago.…”

“…Two of the 18 studies in Table 1 observed a significant decrease in survival with RF exposure [Szmigielski et al, 1982;Liddle et al, 1994]. Both of these studies exposed mice to 2450 MHz (CW) at similar dose rates but there were important differences in experimental protocols, including duration of daily exposure (2 h vs. 1 h) and the number of animals per cage during exposure (10 vs. 1).…”

“…Both of these studies exposed mice to 2450 MHz (CW) at similar dose rates but there were important differences in experimental protocols, including duration of daily exposure (2 h vs. 1 h) and the number of animals per cage during exposure (10 vs. 1). Szmigielski et al [1982] reported that both dose rate ranges (2-3 and 6-8 W/kg) used in their study caused a significant decrease in survival of mice that developed spontaneous mammary tumors and skin cancer induced by 3,4-benzopyrene (BP), e.g., the mean survival time of mice exposed for 5 months to 6-8 W/kg and treated every second day with BP was 165 days compared to 331 days for controls. Liddle et al [1994], on the other hand, found an effect on lifespan at 6.8 W/kg only and not at 2 W/kg.…”

“…(Note: The study by Repacholi et al [1997] is not included in the data set of 18 studies or in the table because no survival data were reported.) Szmigielski et al [1982] found that RF exposure caused accelerated development of three different types of tumors. Exposure of mice to 2450 MHz microwaves at 2-3 or 6-8 W/kg for 2 h/day, 6 days/week for varying periods of up to about 10 months, was reported to (1) accelerate the appearance of spontaneous mammary cancer, (2) decrease the time to occurrence of skin tumors induced by a carcinogen (3,4-benzopyrene), and (3) increase the number of neoplastic nodules developing in the lungs of mice injected with cancer cells.…”