8-WEEK TOXICITY STUDY OF 60 HZ MAGNETIC-FIELDS IN F344 RATS AND B6C3F1 MICE

Toxicity studies were performed by exposing F344/N rats and B6C3F1 mic e (10 animals per sex per species per group) to transient-free, linear ly polarized 60 Hz magnetic fields for 8 weeks. Targeted magnetic fiel ds strengths used were 0 gauss (G; sham control fields did not exceed 0.001 G), 0.02 G, 2 G, and 10 G. Exposure was whole-body and continuou s for 18.5 hr per day, 7 days per week. An additional group of rats an d mice was exposed intermittently (1 hr on/1 hr off) to 10 G fields fo r the same period of time. Endpoints evaluated included morbidity, mor tality, gross pathology, histopathology, body/organ weights, clinical chemistry (rats only), and hematology (rats only). All mice and all ma le rats survived until the end of the study. One female rat (2-G expos ure group) died during Week 7 of the study; the death was not attribut ed to magnetic field exposure. In both studies, the mean body weight g ains of exposed animals were similar to those of the respective contro ls. There were no gross, histological, hematological, or biochemical l esions attributed to magnetic held exposure. Statistically significant increases in liver weight and liver to body weight ratio occurred in female rats of all exposure groups but only at the termination. These data suggest that, for the variables evaluated in these studies, an g- week exposure to linear-polarized, transient-free 60 Hz magnetic field s at field intensities of up to 10 G is not associated with significan t toxicity in F344/N rats and B6C3F1 mice. Furthermore, there was no t oxicity observed in animals receiving intermittent (1 hr on/1 hr off) exposures to 10-G fields. A 2-year study in F344/N rats and B6C3F1 mic e is nearing completion of the in-life phase without overt toxicity in any exposed group. It is premature, however, to make any prediction c oncerning the possible influence of exposure to 60 Hz magnetic fields on cancer rates. (C) 1997 Society of Toxicology.