The influence of long-term exposure of mice to randomly varied power frequency magnetic fields on their nocturnal melatonin secretion patterns

Disruption of the normal melatonin rhythm has many implications in health a nd disease. Exposure to magnetic fields is alleged to suppress nocturnal me latonin production, which could implicate magnetic fields in the developmen t of, for example, breast cancer. Magnetic fields of overhead powerlines al legedly pose a risk in the development of childhood leukemia, and the quest ion arises whether changed pineal function could play a role here. In this study two strains of mice were exposed to a rms 50-Hz magnetic field which varied randomly between 0.5 and 77 muT with an average of 2.75 muT and comp ared to sham-exposed groups. The male mice were exposed for 24 h per day fr om conception until adult age. Nighttime plasma melatonin values were deter mined using radioimmunoassay (n = 9 for each time point). Statistical compa rison was done by nonparametric 95% confidence intervals for median differe nces to determine nocturnal elevated melatonin values. Although a shortcomi ng of the study was the small sample size, no statistically significant dif ference in the nocturnal median elevated melatonin values between exposed a nd sham-exposed groups could be demonstrated. Long-term and continuous expo sure to simulated powerline magnetic fields did not result in a decreased n octurnal melatonin secretion in mice. (C) 2001 Academic Press.