Spontaneous and Nitrosourea-Induced Primary Tumors of the Central Nervous System in Fischer 344 Rats Chronically Exposed to 836 MHz Modulated Microwaves

Abstract

We have tested an 836.55 MHz field with North American Digital Cellular (NADC) modulation in a 2-year animal bioassay that included fetal exposure. In offspring of pregnant Fischer 344 rats, we tested both spontaneous tumorigenicity and the incidence of induced central nervous system (CNS) tumors after a single dose of the carcinogen ethylnitrosourea (ENU) in utero, followed by intermittent digital-phone field exposure for 24 months. Far-field exposures began on gestational day 19 and continued until weaning at age 21 days. Near-field exposures began at 35 days and continued for the next 22 months, 4 consecutive days weekly, 2 h/day. SAR levels simulated localized peak brain exposures of a cell phone user. Of the 236 original rats, 182 (77%) survived to the termination of the whole experiment and were sacrificed at age 709-712 days. The 54 rats (23%) that died during the study ("preterm rats") formed a separate group for some statistical analyses. There was no evidence of tumorigenic effects in the CNS from exposure to the TDMA field. However, some evidence of tumor-inhibiting effects of TDMA exposure was apparent. Overall, the TDMA field-exposed animals exhibited trends toward a reduced incidence of spontaneous CNS tumors (P < 0. 16, two-tailed) and ENU-induced CNS tumors (P < 0.16, two-tailed). In preterm rats, where primary neural tumors were determined to be the cause of death, fields decreased the incidence of ENU-induced tumors (P < 0.03, two-tailed). We discuss a possible approach to evaluating with greater certainty the possible inhibitory effects of TDMA-field exposure on tumorigenesis in the CNS.

Survival and cancer in laboratory mammals exposed to radiofrequency energy

“…Results reviewed here also show that long term, low level exposure ( 4 W/kg) to RF energy did not affect survival adversely [Chou et al, 1992;Liddle et al, 1994;Toler et al, 1997;Frei et al, 1998a,b;Adey et al, 1999Adey et al, , 2000Heikkinen et al, 2001;Zook and Simmens, …”

“…This finding of a beneficial effect, therefore, has not been accepted because of major experimental deficiencies. Many of the other studies [Spalding et al, 1971;Preskorn et al, 1978;Chou et al, 1992;Frei et al, 1998a,b;Adey et al, 1999Adey et al, , 2000, including the results of Liddle et al [1994] at 2 W/kg, show a nonsignificant increase in survival with RF exposure. While this trend is interesting, the overall weight-of-evidence in these animal studies does not support an effect on survival, either detrimental or beneficial, due to long term, low level RF exposure.…”

“…There are a number of recent, well designed studies that show that RF exposure at SARs 4 W/kg for long periods (18-25 months) did not decrease survival [Chou et al, 1992;Toler et al, 1997;Frei et al, 1998a,b;Adey et al, 1999Adey et al, , 2000Heikkinen et al, 2001;Zook and Simmens, 2001;Utteridge et al, 2002]. For example, RF exposure (1 h/day, 5 days/week) of mice up to 2 years at 0.25, 1, 2, and 4 W/kg has been recently reported to have no affect on survival [Utteridge et al, 2002].…”

Radiofrequency exposure and mammalian cell toxicity, genotoxicity, and transformation

“…No mention was made of any observation of tissue necrosis. In a second study, performed independently, Adey et al [2000] exposed Fischer 344 rats to an 836.66 FM signal, modulated by recorded speech. The SARs are not certain, since the Table 1 data for this exposure is exactly the same as the Table 1 SAR data in the 1999 article, unless the SARs were exactly the same.…”

“…After histopathpological examination of all of the tissues mentioned above, there again was no mention made of any observation of RF induced tissue necrosis. Adey et al [1999] exposed Fischer 344 rats to a 836.55 MHz, NADC RF signal. The ''slot'' average SARs reported at the brain were 1.0-1.6 W/kg.…”