Just taking a walk down the street, it is obvious that more and more people are now using cell phones.
In fact 233 million people - more than two-thirds of all Americans - use them.
Right now there is no proof that they cause cancer, but it remains a concern.
Cell phones emit radiofrequency energy. Researchers want to know if that energy can be harmful. And if so, how much is too much?
Today's study can't answer that question yet, but it does give us a look at how RF energy affects brain activity.
Researchers followed 47 healthy adults over one year. They were given PET scans several times - an activated cell phone was placed over one ear, while an inactivated phone was placed over the other.
After 50 minutes, brain imaging showed an increase in brain activity on the side with the activated cell phone.
"This right area of the brain that was very close to the antenna shows the largest increase in metabolism as compared when the telephones were off," says Dr. Nora Volkow, of the National Institute on Drug Abuse. She was the lead researcher on the study.
But this research, like others, falls short.
We don't know if increased brain activity due to radiofrequency energy from cell phones causes any long-term health consequences.
So this is something that will continue to be studied.
