Cell phones are currently used by 95% of American adults. The U.S. Food and Drug Administration (FDA) nominated radio frequency radiation (RFR) used by cell phones for an NTP [National Toxicology Program] study because of widespread public use of cell phones and limited knowledge about potential health effects from long-term exposure. NTP conducted two-year toxicology studies in rats and mice to help clarify potential health hazards, including cancer risk, from exposure to RFR like that used in 2G and 3G cell phones. The NTP studies found that high exposure to RFR (900 MHz) used by cell phones was associated with: Clear evidence of an association with tumors in the hearts of male rats (malignant schwannomas); some evidence of an association with tumors in the brains of male rats (malignant gliomas); some evidence of an association with tumors in the adrenal glands of male rats (benign, malignant, or complex combined pheochromocytoma). As a follow-up, NTP published an article in October 2019 that evaluated DNA damage in three regions of the brain, the liver, and in blood cells in rats and mice that were removed at an earlier timepoint from the ongoing 2-year toxicology study. NTP scientists found that RFR exposure was associated with an increase in DNA damage ... in the frontal cortex of the brain in male mice, the blood cells of female mice, and the hippocampus of male rats.