the study group did acknowledge that “heavy users” of cell phones had an approximately 80 percent increased risk of glioma, a life-threatening and often-fatal brain tumor, after 10 years of cell phone use. What was the definition of a heavy user? About two hours—per month! When this study was conducted (1999–2004), cell phone use had not yet exploded to the extent it has today. Now, after two decades have passed since the study began, the average American uses their cell phone more than three and a half hours per day.
