Researchers at the National Cancer Institute (NCI) found that people who used cellular phones did not have an increased risk of brain tumors compared to non-users.  The study, due to be published in the Jan. 11, 2001, issue of the New England Journal of Medicine (NEJM)*, was released on Dec. 19.   

The use of hand-held cellular phones involves placing a small transmitter that emits radio frequency radiation next to the head. There has been widespread public concern that this radiation might cause tumors of the brain and nervous system.  Because it is not known whether the radiation from cell phones poses a cancer risk, NCI scientists included cell phone use as part of a comprehensive study on the causes of brain tumors that began in 1994.  

The NCI adult brain tumor study involves about 800 adult brain tumor cases and 800 controls (people without brain tumors) from three medical institutions in Phoenix, Boston, and Pittsburgh.  Data collection was done by a structured personal interview in which participants were asked specific questions about when they first began using a hand-held cellular phone, date of last use, and the usual level of use.  Information about the specific make or model of the phone was not collected. Data collection was completed in 1998.  

The researchers found no evidence that a person's risk of developing a brain tumor increased with increasing years of use or average minutes of use per day, nor did brain tumors among cellular phone users tend to occur more often than expected on the side of the head on which the person reported using their phone.  Among high-level users were participants who used the phones for an average of 15 or more minutes per day for at least three years.  Very few people used their phone frequently for more than five years.   

"We don't see any evidence that cell phones cause brain tumors, said Peter D. Inskip, Sc.D., principal investigator for the study from NCI's Division of Cancer Epidemiology and Genetics in Bethesda, Md. But if an increased risk of brain tumors occurs only after five or more years, or only among very heavy users, this study probably would not detect it.

The NCI study began in 1994 and was completed in 1998, during a time when analogue phones were primarily used.  Digital phones, which operate at a higher frequency, are more commonly used today. However, there is no evidence at this time that cancer risk would differ for the two types of phones.
 

Similar results were seen in two other studies.  One published this month in the Journal of the American Medical Association by Muscatet al., involved 469 brain tumor cases and 422 controls.  The researchers did not find an association between use of hand-held cellular telephones and the risk of glioma, the most common form of brain cancer in adults. A 1999 Swedish study by Hardell et al., involving 233 brain tumor cases and 466 controls, also did not find an association between the amount of cell phone use and the risk of brain tumors.  The investigators reported an association between side of the head on which the tumor occurred and side of phone use, but this was based on a small number of brain tumor cases. 

There are three other types of wireless or mobile phones currently on the market car cellular phones, transportable cellular phones, and cordless phones.  All of these involve much lower radiation exposure to the brain.  With car cellular phones, the antenna is mounted on the outside of the car some distance from the user.  Transportable cellular phones, or bag phones, have a transmitter with the battery pack in a portable unit separate from the handset.  Cordless phones have a base unit wired to the land-line telephone service and typically operate at a lower frequency and much lower power than cellular phones.  If hand-held cellular phones do not cause brain tumors, it would be surprising if these other types of wireless phones do, because of the lower level of radiation exposures. 

The number of people using cell phones has increased dramatically during the past 10 years, and this trend appears likely to continue. According to the Cellular Telecommunications Industry Association, there are currently about 107 million cellular phone subscribers in the United States, increasing at a rate of about 2 million per month.     

Because of the large number of users worldwide, there are several other studies in progress involving cell phones and brain tumors. The largest of these is a multicenter, international case-control study involving about 3,000 cases and 3,000 controls, coordinated by the International Agency for Research on Cancer (IARC), based in Lyon, France.  Results are expected in several years.  A Danish study, which includes a cohort of 550,000 cellular phone subscribers from 1982 to 1995, is expected to be published soon. 

In addition, a $10 million program on cell phone research was recently announced in the United Kingdom.  In the United States, the Food and Drug Administration (FDA) and the Cellular Telecommunications Industry Association (CTIA) have recently signed a Cooperative Research and Development Agreement (CRADA), which stipulates that FDA will provide scientific and technical guidance for studies which evaluate the health effects of cellular phone use. 

Because the causes of brain tumors are largely unknown, NCI scientists conducting the adult brain tumor study are evaluating a wide range of environmental, lifestyle, and genetic factors as possible risk factors.  These include workplace exposures to chemical agents and electromagnetic fields, dietary factors, family history of tumors, genetic factors, home use of selected appliances, reproductive history and hormonal exposures, viruses, and medical and dental exposure to ionizing radiation.  Results from these studies will be reported in future publications.  Because of intense public interest, cellular phone use is the first report.

*The study is titled, "Cellular-telephone use and brain tumors." The authors are Peter D. Inskip, Robert E. Tarone, Elizabeth E. Hatch, Timothy C. Wilcosky, William R. Shapiro, Robert G. Selker, Howard A. Fine, Peter M. Black, Jay S. Loeffler, and Martha S. Linet. NEJM 2001: Vol. 344:79-86. A copy is available on the Web Site at http://content.nejm.org/

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