Seeking the answer to this question is notoriously difficult, not least of all because mobile phones are still relatively new. Today, 95 percent of Americans use cellphones, according to the Pew Research Center. That’s a huge jump since 2000, when about 28 percent of Americans used cellphones, according to a separate survey.
Cellphones have been in mainstream usage for under two decades, and yet “radiation-induced brain tumors normally take about 10 to 15 years to develop,” wrote M. Nathaniel Mead in a 2008 essay for the journal Environmental Health Perspectives. Yet an astronomical spike in incidences of malignant brain tumors—the kind you might look for if cellphones really do cause cancer—hasn’t been recorded.
Because cellphones don’t emit enough radiation to mutate a person’s DNA the way a nuclear bomb or a trip to outer space might, scientists have focused on other radiation-related concerns in their research. Early work in the field focused on the possibility that phone emissions could damage a person’s cells by heating up the surrounding tissue—the idea being that radio-frequency waves can raise the temperature of water, and most human tissue is made of water molecules. More recently, however, researchers examined whether cellphone radiation can harm humans even without heating up their cells.
Plenty of scientists, regulators, and—no surprise here—leaders of wireless tech firms say there’s no reason to worry about cellphones causing cancer. Evidence of a causal link just isn’t there, they say. That’s not for lack of trying to find one. Several of the biggest studies that have sought a connection between cellphone use and cancer found no correlation. (Two of the most notable recent examples of large prospective studies that found no link are here and here.) The U.K. Imperial College London is still working on one highly anticipated study, which is investigating the possible health effects of long-term cellphone use across five European countries.
But this hasn’t quieted those who are concerned. In 2015, nearly 200 scientists from across the world signed an open letter urging the United Nations and the World Health Organization to develop stricter rules around wireless technology and public health. Their concerns weren’t limited to cellphones, but included a slew of devices like baby monitors, WiFi, cordless phones, and so on.
In May, a group of researchers published in PLOS ONE the results of a meta-analysis that found a “significant” association between long-term mobile phone use and the risk of glioma, the class of tumors that includes glioblastoma. But the actual significance of the link is questionable. The data they used spanned 11 studies between 1980 and 2016, but the researchers themselves acknowledged the evidence is limited and much of the data is “poor quality.” The biggest takeaway, then, may be their conclusion that more study is needed.