Whether cellphone use causes cancer is an ongoing question with, as yet, incomplete answers. But a new study may shed light on the subject with the finding of "oxidative stress" in the saliva of cellphone users.
The experiment, led by Yaniv Hamzany, an ear, nose and throat specialist with Tel Aviv University's Sackler Faculty of Medicine, compared the saliva of 20 heavy cellphone users (those who spoke on their cellphones an average of 30 hours per month) with the saliva of 20 individuals, most of whom are deaf and either don't use a cellphone or use it for non-verbal functions like texting. The results: The heavy cellphone users showed more signs of oxidative stress.
What does that term mean? Essentially, cell damage. More specifically, it's a molecular imbalance between antioxidants and pro-oxidants, or free radicals. Free radicals are a natural byproduct of metabolism but are also linked with aging and, when they outnumber the antioxidants, cell damage occurs.
Hamzany concludes that exposure to cellphones causes oxidative stress, which harms human cells and DNA and contributes to a "carcinogenic effect." He adds that his study corroborates the results of so many others, which find correlation, not causation, between cellphones and cancer risk. "It does give us an idea of the harmful effect of the telephone," he says, advocating caution rather than discontinuing cellphone use. "Maybe use it less often, maybe not expose children to it," he tells U.S. News. "Maybe there is a kind of additive effect, and in the long run it could cause tumors."
In May 2011, the International Agency for Research on Cancer convened a group of 30 scientists in Lyon, France to review wide-ranging studies on radiofrequency electromagnetic fields, the radiation associated with cellphones. Their conclusion: Cellphones are "possibly carcinogenic to humans," but there is "limited evidence in humans and in experimental animals."
The conclusion took into account an international study, which assessed thousands of people over the course of a decade and found a slightly increased cancer risk among the group with the greatest exposure to cellphones but did not prove a causal connection.
Robert Baan , a toxicologist and biochemist who organized the 2011 researchers, told U.S. News that Hamzany's study would not be a reason to rethink their conclusion. He critiqued the small size and scope of the data, noting, for example, that he would have liked details on the extent of correlation between oxidative stress levels and the most frequent cellphone users, and he expressed concern about the control group. "I don't know if being deaf has other affects on the saliva or on the physiology of the ear in general," he says. Still, Baan says Hamzany's research "raises questions, and it asks for more studies in this direction."
The cancerous threat of cellphones, experts say, may take decades still to determine.
"If there has been exposure to the brain tissue, it may take very, very long before a cancer appears, and it may be there as a tiny little clump of malignant cells [and] 10, 20 or 30 years later, it becomes a tumor that can be very painful," Baan says. Until then, he says people can reduce their exposure by keeping the phone away from the body and using earphones. "Some people say we are too early to really establish the cancer consequences of this type of exposure, so we should be prudent now."
The kind of radiation that causes cancer and is used in radiation therapy is called ionizing, according to the National Institutes of Health's National Cancer Institute. But a link between cancer and non-ionizing radiation, or radiofrequency energy, remains unproven, according to the NCI. And yet, Hamzany's study appears to undercut part of the National Cancer Institute's stance. "It is generally accepted that damage to DNA is necessary for cancer to develop," the institute states on its website."However, radiofrequency energy, unlike ionizing radiation, does not cause DNA damage in cells."
[See: A Guide to Cancer Prevention.]
Meanwhile, the U.S. Federal Communications Commission is in the midst of reviewing its safety guidelines for radiofrequency exposure. The current guidelines, based on recommendations from federal health and safety groups like the Environmental Protection Agency and Food and Drug Administration, were adopted in 1996.
"The U.S. has among the most conservative standards in the world," says Neil Grace, FCC senior communication adviser. "As part of our routine review of these standards, which we began last year, we will solicit input from multiple stakeholder experts, including federal health agencies and others, to guide our assessment."
Lori Wirth, medical director of the Center for Head and Neck Cancers at Massachusetts General Hospital, calls Hamzany's data "very interesting and intriguing," but adds that it merits a "healthy amount of caution." "We don't know if there is a direct link between markers of oxidative stress in saliva and the risk of cancer," she says. "We do know that oxidative stress can lead to DNA damage, free radical damage of DNA, and that is one potential mechanism of carcinogenesis."
But the more immediate threat from cellphones, she argues, has nothing to do with cancer, and points instead to the more mundane hazards of distracted driving.
"There's very good data that shows that talking on the phone and texting on the cellphone while driving leads to real death on the road, and that's something that we have direct evidence and direct data on," Wirth says. "Honestly, that's where the real harm from cellphones in our society is coming from."
- oxidative stress
- National Cancer Institute