Researchers from the Yale School of Medicine found that exposing pregnant mice to radiation from a cell phone affected the behavior of their offspring later. They found that the mice exposed to radiation as fetuses were more hyperactive, had more anxiety and poorer memory -- symptoms associated with attention deficit hyperactivity disorder (ADHD) -- than mice who were not exposed to radiation.
Neurological tests revealed that the radiation exposure led to abnormal development of neurons in the part of the brain linked to ADHD, leading the authors to suggest that cell phone radiation exposure may play a role in the disorder.
"During critical windows in neurogenesis, the brain is susceptible to numerous environmental insults; common medically relevant exposures include ionizing radiation, alcohol, tobacco, drugs and stress," wrote the authors, led by Dr. Hugh Taylor, professor and chief of the Division of Reproductive Endocrinology and Infertility.
They added that while their study provides "the first experimental evidence of neuropathology due to in-utero cellular telephone radiation," the data are not conclusive, and more research is needed to determine the effects of radiation on humans or non-human primates.
Dr. F. Sessions Cole, professor of pediatrics and chief of newborn medicine at Washington University School of Medicine, in St. Louis, said that while the research is "provocative," the data are a long way from being applicable to humans.
"Mice are very different than humans," he said. "The distance the phone was placed away from the mice in the study was between 4 and 20 centimeters, which is a very short distance compared to the distance from the ear to the womb in humans. It's likely the dose of radiation the mice received is much greater than what a human fetus would receive."
Cole added that mice also have a much shorter gestation period, only 19 or 20 days, which can also mean a very different type of exposure than humans.
There have been a number of studies that looked at how cell phone radiation can possibly affect humans in different ways, from the development of cancer to behavior problems. Data have been inconclusive so far, and there has been no evidence of causation.
A 2010 study of more than 28,000 Danish children found that exposure to cell phones both before and after birth increased the risk for behavior problems.
Similar research back in 2008 sounded alarms in the media when news outlets reported that a particular study found that using mobile phones can cause serious harm to babies.
That study did find that Danish mothers who used cell phones during pregnancy reported more behavioral problems in their children, but the author said it was merely an association.
"That's clearly not what we wanted to suggest, and we think that there is no reason that pregnant women should be very alarmed at the findings we have," the lead author, Dr. Jorn Olsen of UCLA, told ABC News at the time the study was published.
There have also been several studies that examined the link between cell phones and cancer in children and adults, which also yielded inconsistent findings.
"There's been a lot of work on this subect, and it's been pretty exhaustively demonstrated that cell phone radiation does not affect human health," said Cole.
A European study published in October found that cell phone users were not at higher risk for cancer, although the research couldn't definitively rule that risk out. This research came just months after the World Health Organization said cell phones were a possible cause for cancer.
The American Cancer Society's position is that there could be some cancer risk, but supporting evidence is not very strong. The agency urges people who are concerned to limit cell phone use, especially among children.
But the Environmental Health Trust, a charitable organization whose mission is to educate the public about health risks in the environment, says the evidence from multiple studies shows there is reason to be concerned about the effects of cell phones.
They urge people to keep phones away from their head and their body when they are in standby mode and to avoid using them when the signal is weak. The group is also calling for more long-term research exploring the issue further.
And almost every phone manufacturer includes warnings in packaging urging users to take precautions.
The authors of the current study hope their findings will contribute to the understanding of how childhood behavior problems develop.
"The rise in behavioral disorders in developed countries may be, at least in part, due to a contribution from fetal cellular telephone radiation exposure," they wrote. "Further testing is warranted in humans and non-human primates to determine if the risks are similar and to establish safe exposure limits during pregnancy."
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