Lagroye, I, Hook GJ, Wettring BA, Baty JD, et al. (2004 a):
Lai and Singh are the only authors who have reported strand breaks in DNA after RF exposure at non-thermal levels. The present authors suggest that the failure of others to replicate the results of Lai and Singh may have been due to the fact that the latter used a protocol that included a proteinase K digestion step. Some types of alkali-labile DNA damage could be undetected in the alkaline comet assay used in these studies. The present study was designed to explore this possibility.
C3H 10T1/2 cells were exposed for 2 hours to either 2450 MHz continuous-wave (CW) microwaves at an SAR of 1.9 W/kg or 1mM cisplatinum (CDDP, a positive control for DNA crosslinks), and were then irradiated with 4 Gy of gamma rays. Immediately after the irradiation, the single-cell gel electrophoresis assay was performed to detect DNA damage. For each exposure condition, one set of samples was treated with proteinase K to remove any possible DNA-protein crosslinks.
No DNA damage could be detected after exposure to 2450 MHz microwaves alone. The CDDP significantly reduced both the comet length and the normalized comet moment in the cells irradiated with gamma irradiation. In contrast, 2450 MHz microwaves did not impede the DNA migration induced by the gamma rays. When control cells were treated with proteinase K, both parameters increased in the absence of any DNA damage. However, no additional effect of proteinase K was seen in samples exposed to 2450 MHz microwaves or in samples treated with the combination of microwaves and radiation. On the other hand, proteinase K treatment was ineffective in restoring any migration of the DNA in cells pretreated with CDDP and irradiated with gamma rays. Specific measurement of DNA-protein crosslinks or of protein associated with DNA failed to reveal any effect of the microwave exposure.
Hence, the authors were unable to confirm the hypothesis that the changes seen by Lai and Singh were due to the proteinase K step in their protocol. The authors conclude that CW 2450 MHz microwaves cannot produce genotoxic effects by directly causing DNA damage.