A major U.S. government study on rats has found a link between cellphones and cancer, an explosive finding in the long-running debate about whether mobile phones cause health effects.

The multiyear, peer-reviewed study, by the National Toxicology Program, found “low incidences” of two types of tumors in male rats that were exposed to the type of radio frequencies that are commonly emitted by cellphones. The tumors were gliomas, which are in the glial cells of the brain, and schwannomas of the heart.

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