Assessing the potential carcinogenic activity of magnetic fields using animal models

We update our 1997 publication by reviewing 29 new reports of tests of magn etic fields (MFs) in six different in vivo animal models of carcinogenesis: 2-year, lifetime, or multigeneration exposure studies in rats or mice; and promotion/progression models (rat mammary carcinoma, rat liver focus, mous e skin, several models of human leukemia/lymphoma in rats and mice, and bra in cancer in rats). Individual experiments are evaluated using a set of dat a quality criteria, and summary judgments are made across multiple experime nts by applying a criterion of rough reproducibility. The potential for car cinogenicity of MFs is discussed in light of the significant body of carcin ogenesis data from animal bioassays that now exists. Excluding abstracts, a pproximately 80% of the 41 completed studies identified in this and our Pre vious review roughly satisfy data quality criteria. Among these studies, th e criterion for independent reproducibility is not satisfied for any positi ve results but is satisfied for negative results in chronic bioassays in ra ts and mice and for negative results in both promotion and co;promotion ass ays using the SENCAR mouse skin model. Results of independent replication s tudies using the rat mammary carcinoma model were conflicting. We conclude that long-term exposure to continuous 50- or 60-Hz MFs in the range of 0.00 2-5 mT is unlikely to result in carcinogenesis in rats or mice. Though resu lts of most promotion/progression assays are negative, a weak promoting eff ect of MFs under certain exposure conditions cannot be ruled out based on a vailable data.