Cellphone radiation and cancer: More questions arise

As thousands of rats were exposed to greater intensities of RF radiation, more of them developed rare forms of brain and heart cancer that could not be easily explained away.

Federal scientists released partial findings from a $25-million animal study that tested the possibility of links between cancer and chronic exposure to the type of radiation emitted from cellphones and wireless devices.

The findings, which chronicle an unprecedented number of rodents subjected to a lifetime of electromagnetic radiation starting in utero, present some of the strongest evidence to date that such exposure is associated with the formation of rare cancers in at least two cell types in the brains and hearts of rats. The results, which were posted on a prepublication website run by Cold Spring Harbor Laboratory, are poised to reignite controversy about how such everyday exposure might affect human health.

Researchers at the National Toxicology Programme (NTP), chronically exposed rodents to carefully calibrated radio-frequency (RF) radiation levels designed to roughly emulate what humans with heavy cellphone use or exposure could theoretically experience in their daily lives. The animals were placed in specially built chambers that dosed their whole bodies with varying amounts and types of this radiation for approximately nine hours per day throughout their two-year life spans.

More than 90 percent of American adults use cellphones. Relatively little is known about their safety, however, because current exposure guidelines are based largely on knowledge about acute injury from thermal effects, not long-term, low-level exposure.

The International Agency for Research on Cancer in 2011 classified RF radiation as a possible human carcinogen. But data from human studies has been “inconsistent,” the NTP has said on its website. Such studies are also hampered by the realities of testing in humans, such as recall bias — meaning cancer patients have to try to remember their cellphone use from years before, and how they held their handsets. Those data gaps prompted the NTP to engage in planning these new animal studies back in 2009.

The researchers found that as the thousands of rats in the new study were exposed to greater intensities of RF radiation, more of them developed rare forms of brain and heart cancer that could not be easily explained away, exhibiting a direct dose — response relationship.

Overall, the incidence of these rare tumors was still relatively low, which would be expected with rare tumors in general, but the incidence grew with greater levels of exposure to the radiation. Some of the rats had glioma — a tumor of the glial cells in the brain—or schwannoma of the heart.

Furthering concern about the findings: In prior epidemiological studies of humans and cellphone exposure, both types of tumors have also cropped up as associations.

In contrast, none of the control rats — those not exposed to the radiation — developed such tumors. But complicating matters was the fact that the findings were mixed across sexes: More such lesions were found in male rats than in female rats. The tumors in the male rats “are considered likely the result of whole-body exposure” to this radiation, the study authors wrote. And the data suggests the relationship was strongest between the RF exposure and the lesions in the heart, rather than the brain: Cardiac schwannomas were observed in male rats at all exposed groups, the authors note. But no “biologically significant effects were observed in the brain or heart of female rats regardless of modulation.”

Based on these findings, researchers said that this is not just an associated finding — but that the relationship between radiation exposure and cancer is clear.