Microwave exposure and oxidative stress
Few studies have
explored the effect of microwave radiation on oxidative stress i.e.
the changes that take place when cells are subjected to increased levels
of oxygen. In a recent paper, Zmyslony and colleagues found that exposure
to a 930 MHz continuous wave field at a SAR of 1.5 W/kg increased the
free oxygen radicals in
rat lymphocytes that had been treated with iron ions. Free radicals
have been implicated in a number of harmful outcomes, including DNA
damage. For more, see "Research - Laboratory
experiments - Others".
There have been a number of studies suggesting that radiofrequency radiation (RFR) can induce the production of heat shock proteins, which are part of a cell's response to various kinds of stress. Similarly, a recent study (Markkanen, 2004) showed that RFR could induce an increased tendency to cell death. Now another study by Capri and colleagues fails to confirm these findings. Human blood cells exposed to 1800 MHz intermittently for 44 hours did not show any increase in cell death or in heat shock protein production. For more, see "Research - Laboratory - Others - Heat shock proteins".
Capri M, Scarcella E, Bianchi E, Fumelli C, et al. (2004): 1800 MHz
radiofrequency (mobile phones, different Global System for Mobile Communication
modulations) does not affect apoptosis and heat shock protein 70 level
in peripheral blood mononuclear cells from young and old donors. Int
J Radiat Biol 80:389-397.
In the March '01 and March '02 "What's New" we discussed papers published by Johansen and colleagues. He has now summarized this research, and also other studies on extremely low frequency electromagnetic fields, in a recent publication. The body of work was part of a doctoral dissertation.
Johansen C (2004): Electromagnetic fields and health effects - epidemiologic
studies of cancer, diseases of the central nervous system, and arrhythmia-related
heart disease. Scand J Work Environ Health 30:Suppl 1:1-30.
A Swedish study
has compared the output power of mobile phones in different geographical
areas during a one-week period in September 2001. Four areas were used
- rural, small urban, suburban, and city. The base station density per
km² was highest (27.37) in the city area, and lowest (0.01) in
the rural area. The highest output power
The authors conclude that these findings are probably related to the lower density of base stations in rural areas. The density of base stations is not the only factor that influences power output. This can be seen from the fact that the small urban area, where the base station density was lower than the city, had lower median power output levels and a smaller proportion of call time at the highest power level. Clearly other factors, such as the distance from the base station, the presence of physical obstacles, etc., also affect the findings. Nevertheless, as the authors point out, in epidemiological studies the degree of urbanization may be an important consideration in assessment of exposure to radiofrequency radiation from mobile phones. For a discussion of factors influencing the results of epidemiological studies, see "Research - Epidemiology".
Reference: Lonn S, Forssen U, Vecchia P, Ahlbom A, Feychting M (2004): Output power levels from mobile phones in different geographical areas; implications for exposure assessment. Occupational and Environmental Medicine 61:769-772.