Cellphone users may be at increased risk for two types of rare cancers and should try to reduce exposure to energy emitted by the phones, according to a panel of 31 international scientists convened by an agency within the World Health Organization (WHO).
LOS ANGELES — Cellphone users may be at increased risk for two types of rare cancers and should try to reduce exposure to energy emitted by the phones, according to a panel of 31 international scientists convened by an agency within the World Health Organization (WHO).
Studies have not shown definitively that cellphone use increases cancer risk, said the authors of the consensus statement issued Tuesday by the WHO. However, “limited” scientific evidence exists, they said, to suggest the radio-frequency energy released by cellphones may increase the risk of two types of cancers: glioma, a type of brain cancer, and acoustic neuroma, a tumor of the nerve that runs from the ear to the brain.
Both cancers are rare: In the United States, about 10,000 to 12,000 people develop a glioma each year and about 3,000 develop acoustic tumors. The elevated risk roughly doubles that risk after a decade of cellphone use, according to some studies. But the number of cellphone users worldwide — about 5 billion — means a potential cancer link should be taken seriously, said Dr. Jonathan Samet, chairman of the department of preventive medicine at the University of Southern California’s Keck School of Medicine and chairman of the panel that issued the report.
“What we have here is a warning from a public health point of view,” Samet said. “We have half the world’s population already using cellphones, and people are using them younger and longer. We clearly need to keep track of this.”
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Other scientists said that they remained skeptical of the link, which is mired in contradictory science, and that they found the decision by the WHO perplexing.
“I find the conclusions surprising given that there is increasingly strong evidence that cellphone use has no association with brain-cancer occurrence,” said David Savitz, a professor in the departments of epidemiology and obstetrics and gynecology at Brown University and a researcher on environmental exposures and health. “With few exceptions, the studies directly addressing the issue indicate the lack of association.”
Cellphones were placed in a “possibly carcinogenic to humans” category by the International Agency for Research on Cancer (IARC), which develops scientific cancer-prevention strategies for the WHO. The agency’s four other categories for substances or agents are: carcinogenic to humans; probably carcinogenic to humans; not classifiable; and probably not carcinogenic to humans.
Scientists long have debated the potential cancer risk linked to cellphone use, but this statement marks the first time an independent group of scientists has taken anything other than a neutral stand.
“I think it’s a very fair conclusion,” said Henry Lai, a University of Washington bioengineering professor who was the first to show cellphone radiation can damage DNA in brain cells.
Lai and his colleagues also found memory loss and other learning problems in rats exposed to moderate levels of cellphone radiation.
“At this point,” he said, “I think the best thing for people to do is limit their exposure to this radiation.”
The report, to be published in the July 1 issue of the journal Lancet Oncology, listed measures for consumers, such as using headsets, speaker phones or text messaging to reduce the amount of radiation reaching the brain.
“Texting actually helps,” Lai said. “You’re holding the phone away from your head.”
The panel based its conclusions primarily on data from the multicountry Interphone studies coordinated by IARC as well as research by Swedish cancer researcher Lennart Hardell. The Interphone data showed people who used a cellphone 10 or more years had a doubled risk of glioma, a brain cancer that arises in the tissue surrounding and insulating brain cells. One study showed a 40 percent increased risk of gliomas for people who used cellphone an average of 30 minutes a day over a 10-year period.
A 2004 study put the increased risk of acoustic neuromas at twice the normal risk after 10 years of cellphone use and higher for tumors on the side of the head where the phone typically is placed.
Evidence is too scant to draw conclusions about other types of cancer, the report stated, including a 2009 study by Israeli researchers that linked cellphone use and cancer of the salivary gland.
But Savitz said the data are not compelling even for gliomas and acoustic neuromas. The more studies that are published on cellphones and health, he said, the more evidence accumulates that there is no increased cancer risk.
Many scientific questions remain, such as the lifetime risk of people who begin using wireless phones as children and how cancer cells might arise from radio-frequency energy.
Groups representing the wireless industry also downplayed the significance of the report, noting the WHO placed radio-frequency electromagnetic fields in the “possibly carcinogenic” category, along with about 266 other agents, including gasoline and occupational exposure to dry cleaning. Even coffee and pickled vegetables are listed in that category, John Walls, vice president for CTIA-The Wireless Association, noted in a statement.
Still, Lai believes cellphone radiation can be so damaging that he is exploring its use as a way to kill cancer cells. In healthy cells, exposure can lead to production of toxic chemicals called free radicals that can cause the DNA damage and mutations that sometimes trigger malignancy. The effect is even stronger in cancer cells.
“If you can get cells to form a lot of free radicals, they will die,” he said.
The studies are preliminary, but cellphone-type radiation selectively kills cancer cells in test-tube experiments with breast-cancer and leukemia cells, Lai said.
Lai’s comments were reported by Seattle Times science reporter Sandi Doughton.