By Lisa Johnston
New products on display at the American International Toy Fair, held in N
The first nationwide cancer incidence study of cellphone users found no relationship between cellular telephone use and increased cancer rates.
In fact, the results showed that cellphone users in the study population suffered from cancer at rates slightly lower than the incidence rates in the general population.
The study was conducted by the Danish Cancer Society and the International Epidemiology Institute, Rockville, Md., and was reported in the Feb. 7 issue of the Journalof the National Cancer Institute.
The study covered more than 400,000 Danish users of cellphones from 1982 through 1995. The re-searchers compared the number of cancers observed in the group with the expected numbers of cancers calculated for cancer incidence rates in the entire Danish population.
The risk for leukemia and cancers of the brain, nervous system and salivary gland did not vary by duration of cellphone use, time since first subscription, age at first subscription, or whether the phone was analog or digital, the Journal said in a statement. There was also no association found between cellphone use and brain tumors near the ear, where cell phones are typically held.
Based on national cancer rates, 3,825 of the surveyed users should have had cancer, but only 3,391 did, the study found. Of those with cancer, 161 should have had brain or nervous-system cancer, but only 154 did.
The researchers identified Danish cellular users from the records of the country's two carriers, yielding a final study population of 420,095 individuals. Researchers matched the personal identification number assigned to all Danish citizens at birth to the Danish Cancer Registry to determine who had cancer.
Although they cited limited laboratory evidence in rats of a potential link between cell phone use and cancer, the researchers pointed out that phones don't emit enough thermal or ionizing energy to cause cancer. Cellular phones transmit and receive RF signals in the microwave region of the electromagnetic spectrum.
A typical cellphone operates at a power output of 0.25 watts, which the researchers said is associated with a maximum rise in brain temperature of only 0.1 degrees Centigrade. As a result, they rule out biological effects caused by heat. They also said RF radiation does not possess enough energy to break a chemical bond-that is, remove electrons from atoms or molecules. That process, called ionization, is how cancer is produced.
In a Journal editorial, Dr. Robert Park, the director of the Washington office of the American Physical Society, contended the large number of people involved in the study and the use of a "rock solid" database would make it difficult to argue that cellphones cause cancer.
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