Effects of 50-or 60-hertz, 100 mu T magnetic field exposure in the DMBA mammary cancer model in Sprague-Dawley rats: Possible explanations for different results from two laboratories

In line with the possible relationship between electric power and breast ca ncer risk and the underlying melatonin hypothesis, 50-Hz magnetic field (MF ) exposure at microtesla flux densities for either 13 or 27 weeks significa ntly increased the development and growth of mammary tumors in a series of experiments from Loscher's group in Germany. Loscher's group used the 7,12- dimethylbenz[a]anthracene (DMBA) model of breast cancer in Sprague-Dawley r ats. The finding could not be replicated when a similar experimental protoc ol was used in a study conducted by Battelle in the United States. In the p resent paper, investigators from the two groups discuss differences between their studies that might explain the apparent discrepancies between the re sults. These differences include the use of different substrains of Sprague -Dawley rats (the U.S. rats were more susceptible to DMBA than the European rats), different sources for diet and DMBA, differences in environmental c onditions, and differences in MF exposure metrics. Furthermore, the effects of MF exposure reported by Loscher's group, albeit significant, were weak. We also discuss the general problem of replicating such weak effects. powe r, electromagnetic fields, melatonin.