Tests funded by the cellular telephone industry have found a possible link between cell phone usage and cancer. The studies found both biological indications of cell changes and a statistical link correlating cell phone usage with certain types of brain cancer.

Readers report cell-phone-related health problems The tests were conducted at Stanford University and Integrated Laboratory Systems in Research Triangle Park, NC, and found chromosal changes in blood cells subjected to the same type of electromagnetic radiation emitted by hand-held cell phones.

Additionally, an epidemiological study showed nearly a tripling in the incidence of certain cancers -- neurocytomas, which grow inward from the periphery of the brain -- compared with people who do not use cell phones. Another study found that right-handed people who used cell phones and had brain tumors tended to have them on the right side of the brain.

Additional studies are being conducted and further analysis of the just-completed studies is underway.

Radio frequency emissions are generally regarded as dangerous and workers in broadcasting, aviation and similar fields generally try to avoid prolonged exposure to transmitting antennas.

Early cell phones, in which the antennas were mounted outside cars, were not thought to be dangerous. But the newer hand-held models place the transmitting antenna directly against the skull. Further, unlike earlier two-way radios, cell phones are "duplex," meaning that their transmitters remain on even when the user is listening rather than talking, thus increasing the total amount of time the user is exposed to radio waves.