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OBJECTIVE: Because the use of hand held cellular telephone normally involves positioning the antenna close to the users' head questions have been raised about the risk associated with exposure to the microwave (MW) radiation emitted by the antenna of this device. Penafiel et al⁽¹⁾ have reported observing a 40% enhancement on Ornithine Decarboxylase (ODC) activity in L929 murine fibroblast cells after an eight-hour exposure to a digital cellular telephone signal. Because of the important role ODC plays in cell proliferation, a biological response to MW radiation that results in alteration of ODC activity levels has far reaching implications. We report here our findings on ODC activity levels after exposing L929 cells to MW signal from a Time Division Multiple Access (TDMA) cellular telephone.

METHOD: The FDA cellular phone frequency radiation exposure system consists of a model CC110 Crawford Cell and a sham exposure chamber of similar dimensions placed inside a water-jacketed incubator maintaining a constant temperature. A small fan draws air from the incubator through the Crawford Cell and sham chamber to maintain temperature equilibrium. Signal from a TDMA cellular telephone operating at 835 MHz frequency was amplified using an IFI model 40 amplifier and used to drive the Crawford Cell. For each experiment eight 25cm² flasks each containing three million L929 cells were used (four exposed and four control). Flasks were placed end to end on both sides of the center conductor of the Crawford Cell and exposed for eight hours. Specific absorption rate (SAR) was determined in one flask in each experiment by calorimetry using a Luxtron temperature probe. After exposure to the MW radiation cells were harvested and assayed for ODC activity.

RESULTS: ODC activity of MW radiation exposed cells was compared to ODC activity of sham-exposed cells. There was no statistically significant difference between MW radiation exposed cells and sham-exposed cells for non-thermal SAR levels (< 1W/Kg), mean exposed / control (E/C) activity ratio was 0.98 (±0.05 SEM). SAR levels between 1 - 5 W/Kg gave an E/C ratio of 0.88 (±0.03 SEM). SAR levels between 6 - 10 W/Kg gave an E/C ratio of 0.77 (±0.5 SEM), and SAR levels between 11 -15 W/Kg gave an E/C ratio of 0.77 (±0.06 SEM). Sham - sham experiments gave an ODC activity ratio (Crawford Cell / Control Chamber) of 0.96 (±0.06 SEM). Non-MW conventional heating comparable to thermal levels of SAR gave a similar suppression of ODC activity.

CONCLUSION: The data obtained does not demonstrate an enhancement of ODC activity doe to MW exposure. The temperature dependant suppression of ODC obtained with both MW and conventional heating underscores the need for constant temperature monitoring of in vitro MW exposures.

¹ Role of modulation on the effects of microwaves on Ornithine Decarboxylase activity in L929 cells.
Bioelectromagnetics. 1997; 18(2):132-41
Penafiel LM, Litovitz T, Krause D, Desta A, Mullins JM.

Updated 10/30/01