Drivers who use hands-free cellular devices while driving may be doing themselves a favor in the long run. That’s because scientists still can’t say with certainty that placing a cellphone against the head is completely safe, especially for heavy users and people who began using the devices as children.

They point to lingering questions over potential health effects from the energy emitted by the phones, specifically the long-debated risk of developing brain cancer. “It’s fair to say that the data aren’t all in yet,” says Dr David L McCormick, a biologist and director of the Illinois Institute of Technology Research Institute in Chicago, who has studied the issue. “There are a small number of epidemiological studies that have suggested a possible increase in cancer risk. But comparable studies in other populations haven’t confirmed these findings.”

That’s not to say anyone should panic. Cellphones do produce a type of radiation, but it’s of the type called nonionising radio frequency — a form of energy located on the electromagnetic spectrum.

At the high end of the spectrum, ionising radiation, such as that emitted by X-ray machines, has well-known dangers. But the weak signals released by nonionising radio frequencies do not cause DNA damage, and there is no explanation for how such energy could cause cancer, McCormick says.

Most studies have not consistently demonstrated a link between cellphone use and cancer, including two studies conducted by the National Cancer Institute. Several other studies coordinated through the International Agency for Research on Cancer, called the Interphone studies, have also failed to show an association. Numerous studies on animals have also found no evidence that DNA is damaged by low levels of radio frequency, McCormick says.

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