Cell phones and risk of brain tumors: What's the real science?

Story highlights

  • A Berkeley, California, law require cell phone stores to warn about radiation exposure
  • Most research found no association between brain tumors and cell phone
  • Several studies suggest there could be risk associated with heavy or long-term use

(CNN)The city of Berkeley, California, passed a law that goes into effect next month requiring cell phone stores to inform customers about safety recommendations. The move reopened a decades-old debate about whether mobile phones cause brain tumors.

The ordinance, called the Right to Know law, will start to require retailers to give customers a handout, or display a sign in the store, telling them about federal guidelines on the amount of radiation that cell phones can emit and the instructions on safe phone use.
    Lawyers and clinicians involved in creating the new law said that it is meant to make consumers aware of the already existing regulations. However, the information will also go beyond the current regulations by stating that children and anyone carrying their phone in a pocket or bra could be at increased risk of radiation exposure, said Joel M. Moskowitz, director of the Center for Family and Community Health at University of California, Berkeley School of Public Health. Moskowitz was involved in creating the law.
    What the law does not require is that consumers be provided information about the specific health risks of being exposed to radiation. Although Moskowitz said that it is "highly probable" that long-term cell phone use causes brain tumors, many experts think that the evidence is far from definitive, or that it shows there is no risk.
    In 2011, the World Health Organization classified the kind of low-energy radiation that cell phones emit as "possibly carcinogenic" because of a link between cell phone use and a type of malignant brain tumor called glioma and a benign brain tumor called acoustic neuroma.
    Both types of brain tumors are rare. About 5 in 10,000 adults are diagnosed with glioma in the United States every year, whereas about 10 in a million people develop acoustic neuromas every year.
    Although the WHO classification sounds ominous, it puts cell phones on the same level of cancer risk as caffeine and pickled vegetables. The position of numerous health organizations, including the American Cancer Society and the Centers for Disease Control and Prevention, is even more measured, stating that current evidence is not conclusive and more research is needed.

    'A very gray zone'

    "(Since 2011), I don't think any evidence has come along that would necessarily move from this uncertain designation to something on one side or the other. ... In reality we are in a very gray zone with the evidence," said Jonathan M. Samet, chairman of preventive medicine at University of Southern California who led the WHO panel that determined the classification.
    Many large studies have failed to detect an association between cell phone use and brain tumors. One study of nearly 360,000 adults in Denmark did not find an increase in the number of brain tumors even among those who had been using a cell phone for at least 13 years.
    However, as Samet said, the WHO panel took into account studies that suggested that those who used cell phones did have higher rates of certain brain tumors.
    The Interphone study is the largest study to date looking at cell phones and brain tumors. It involves 13 countries, including Canada, the United Kingdom, Denmark and Japan. Researchers asked more than 7,000 people who had been diagnosed with a brain tumor and 14,000 healthy people about their previous cell phone use.
    The study found no association between cell phone use and glioma rates except in the group of participants who reported using their cell phone for at least 1,640 hours in their lifetime without a head-set. Those participants were 40% more likely than those who never use