With 3 billion cell phone users worldwide and more than 260 million in the United States alone—among them 46% of U.S. children aged 8–12, according to Nielsen Mobile figures released 10 September 2008—human exposure to low-energy radiation in the 800- to 2,000-megahertz range is at an all-time high. The most recent attempt to systematically review the epidemiologic evidence for increased risk of brain tumors related to cell phone use indicates that repercussions from this global experiment are coming to light. In a meta-analysis published in the May 2008 issue of the International Journal of Oncology, Swedish researchers found significant associations between long-term cell phone use and brain tumor risk. In July 2008 market research firm MultiMedia Intelligence reported that more than 16 million U.S. teens use cell phones.
“We found that cell phone use is linked to gliomas [malignant brain tumors] and acoustic neuromas [benign tumors of the brain's auditory nerve] and are showing up after only ten years,” says lead author Lennart Hardell, an oncologist and cancer epidemiologist at University Hospital in Örebro, Sweden. Specifically, for studies that included at least 10 years of exposure, there was a doubling in the risk of gliomas for ipsilateral (same-side) but not contralateral (opposite-side) exposures to the head (as reflected by which hand the subject typically used to hold his/her cell phone). A 2.4-fold increase in risk was seen for acoustic neuromas due to ipsilateral exposures, whereas no increased risk occurred for meningiomas (tumors that occur in the membranes covering the brain and spinal cord).