MINNEAPOLIS (WCCO) -- As many as 95 percent of American adults use a cellphone.
Over the past few decades, several studies have been conducted to determine whether those phones are associated with an increased risk of cancer.
Scientists have been split on their opinions on the significance of the risks.
So, who can we believe? Do cell phones cause cancer? Good Question.
"That's actually a pretty difficult question to answer," said Dr. Matthew Hunt, a neurosurgeon with University of Minnesota Health. "It's a really hard thing to study because you're looking at something everyone uses and they use a lot."
There have been a number of research studies on the topic over the past three decades, including several dozen studies conducted on humans that have focused mostly on the brain. Three of the largest ones were conducted in Europe.
The Danish study linked 358,000 cellphone subscribers with brain tumor data and found no association.
The Million Women study asked participants to self-report how much they use their phone and also found no association.
The Interphone study, which used data from questionnaires, found no overall increased risk, but a modest increase in risk for brain tumors among people with the highest exposure.
Experts say there are drawbacks to these human studies including recall bias, where people have a hard time correctly remembering their cellphone usage at a particular time.
"When you look at the amount smoking raises your risk for lung cancer, you're talking about 20, 30, 40 times the risk," Hunt said. "Most of the studies that have looked at brain tumors and cellphone use, if they find anything at all, are finding that, you know, one-and-half times the risk, or even less than that."
So researchers are looking at animals, including a 10-year study just completed by the National Toxicology Program (NTP), a division of the National Institutes of Health.
That huge study subjected 3,000 rats and mice to extremely-high levels of cellphone radiation for nine hours a day over two years. Researchers say they could link tumors in the hearts of male rats to the radiation, but could not in the female rats or mice.
"The levels and duration of exposure to RFR were much greater than what people experience with even the highest level of cellphone use, and exposed the rodents' whole bodies. So, these findings should not be directly extrapolated to human cellphone usage," said Dr. John Bucher, an NTP senior scientist.
With all of this information, Dr. Hunt says he understands it is hard for people to know how to interpret the results because even scientists have different opinions.
"That being said, we still have a good idea that the risk, if there is a risk, still seems to be quite small," Hunt said.
But if someone is still concerned, he recommends following guidance put out by the California's Department of Health.
They suggest keeping your phone away from your body, not sleeping with your phone, using a headset, texting rather than talking and avoiding using the phone when it's signal is low, because that sends out higher radiofrequency energy.
for more features.