The first study, "Association between number of cell phone contracts and brain tumor incidence in nineteen U.S. States," authored by Steven Lehrer, Sheryl Green, and Richard G. Stock from Mount Sinai School Of Medicine, looked at the number of cell phone subscriptions and the number of brain tumors in 19 states. The authors found an independent correlation between cell phone subscriptions and brain tumor incidence and concluded, "The very linear relationship between cell phone usage and brain tumor incidence is disturbing and certainly needs further epidemiological evaluation. In the meantime, it would be prudent to limit exposure to all sources of electro-magnetic radiation."
The second study, "Brain cancer incidence trends in relation to cellular telephone use in the United States," authored by Peter D. Inskip, Robert N. Hoover, and Susan S. Devesa from the National Institutes of Health, looked at brain tumor incidence rates from 1992 to 2006. Overall, there was a slightly downward trend except for 20-29 year old females. In this group of patients, there was a statistically significant increase in frontal lobe tumors--a region of the brain not felt to be at risk from cell phone use. The authors concluded, "Overall,
these incidence data do not provide support to the view that cellular phone use causes brain cancer."
It is difficult to explain the opposing conclusions in these two studies. One issue in both studies is that if there is a causal relationship between cell phone use and brain tumors, it would take many years of cell phone use to yield a tumor. Because the remarkable increase in cell phone use is fairly recent, we may not know for another 10 or more years if there is a relationship between cell phones and brain tumors.
In the meantime, it would be reasonable to use hands free technology and limit cell phone use in children and teens.