Enlarge / A man is seen calling on an iPhone on October 30, 2017. (credit: Jaap Arriens/NurPhoto via Getty Images) The California Department of Public Health officially issued a guidance Friday on how to reduce exposure to radio-frequency energy released by cell phones—despite a lack of solid scientific data suggesting that such exposure poses any harm. The guidance follows the Department’s legal defeat earlier this year surrounding the release of such a guidance. In 2014, public health researcher Joel Moskowitz of the University of California, Berkeley, sued the department after it refused to release the guidance to him.