Researchers from the National Toxicology Program found that radiation from phones using 2G and 3G caused male rats to develop cancerous tumours in the heart and brain.
Dr John Bucher, who led the study, said: “We believe that the link between radio frequency radiation and tumours in male rats is real.”
In the study, the researchers housed rats in special chambers, where they exposed the animals to phone radiation from the womb and through their lifetime.
The radiation exposure was intermittent – 10 minutes on and 10 minutes off, for 9 hours a day.
The researchers found that male rats developed tumours in the heart and brain.
But bizarrely, these rats tended to live for longer than those who hadn’t been exposed to radiation.
Dr Michael Wyde, who worked on the study, said: “This may be explained by an observed decrease in chronic kidney problems that are often the cause of death in older rats.”
Fortunately, the researchers say that the results don’t necessarily mean that phone radiation has the same effect on humans.
Dr Bucher added: “The exposures used in the studies cannot be compared directly to the exposure that humans experience when using a cell phone.
“In our studies, rats and mice received radio frequency radiation across their whole bodies. By contrast, people are mostly exposed in specific local tissues close to where they hold the phone.
“In addition, the exposure levels and durations in our studies were greater than what people experience.”