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         Cell Phone vs Cancer

Editor's note: Between late 1990's and early 2000's, almost all health 
experts' comments and warnings were pointing toward health hazard for use
of cell phones. Of course, long term exposure to radiation is dangerous. 
However, we all are exposed to environmental radiations such as sunlight, 
industrial radiations from manufacturers of radio active products, some 
household appliances, electronic devices, such as Tvs, computers, radios, 
microwave oven and so on in some degrees.  So we must use radio active 
devises carefully, wisely with our judgment and discretion. 
Here is another interesting health expert's report.  Read this with your 
discretion.  It is still very controversial.

Recent Studies Show Cell Phone Use Is Not Associated With Increased Cancer Risk

Nancy J. Nelson

Another reassuring piece of evidence that cellular phones do not cause cancer appears in this issue of the Journal. Researchers evaluated whether a cohort of nearly half a million cellular phone subscribers in Denmark had a higher incidence of cancer than the general population, with a particular interest in leukemia and cancers of the brain and salivary gland. The answer was a resounding no (see article, p. 203).

This article comes on the heels of two case–control studies reported in December by the American Health Foundation and the National Cancer Institute, both of which also found no association between cell phone use and the risk of brain tumors.

“We’re trying to do everything we can to be prudent and evaluate this brand new technology that humans have never experienced before in their history,” said David Savitz, Ph.D., an epidemiologist at the University of North Carolina at Chapel Hill, and member of NCI’s Board of Scientific Counselors. “I don’t see how you can see these studies as anything other than good news.”

Even though Savitz believes that most scientists do not consider cell phones to be a major health hazard or a major cause of brain cancer, he thinks that the high number of users makes it worth spending several million dollars to keep checking with the hope that the study will be negative. “It seems worth doing everything we can to verify that this new technology safe,” he said.

The underlying impetus for these latest three studies is the exponential rise in worldwide cellular phone use during the last decade. Not only has the number of people using cell phones increased dramatically during the past 10 years (see Stat Bite, next page), but this trend appears likely to continue. According to the Cellular Telecommunications Industry Association, there are about 108 million mobile phone subscribers in the United States, and this number is increasing at the rate of about 46,000 new subscribers every day, or about one every 2 seconds. And Christoffer Johansen, M.D., Ph.D., of the Institute of Cancer Epidemiology in Copenhagen, Denmark, and first author of the Journal study, said that the rates for the Scandinavian countries are even higher; about 50% of Denmark’s households own a cell phone, and an even larger percentage of Swedes and Finns are users.

Exposure Time

One of the problems, however, is that cellular phones are an evolving technology. “[The studies] are reflecting an historical period where use was less prevalent and a technology that is not used anymore,” said Savitz.

Dreyer agreed. “Not only has there has been an explosion in the number of cell phone users, but people are using cell phones a lot more now. We have a lot higher exposure levels now than when the studies were done, ” she said.

Some of these same concerns exist with the Danish study. Although the 420,000 cell phone subscribers were followed from 1982 to 1995, the average period of follow-up was short—3.1 years. More than two-thirds of the subscriptions began in 1994 and 1995.

“The real crux of the problem with all the cell phone studies that have been done so far, is there isn’t a very long period of time in which people have been exposed,” said Margaret Wrensch, Ph.D., an epidemiologist from the University of California at San Francisco. “If something is a very abrupt, acute effect, you might expect to see it. But if it’s something that you need to have the exposure over a fairly protracted period of time and at fairly high levels, you’re not going to have enough people who have been exposed at those key levels.”

One important advantage of the Danish cohort study compared to the case–control studies is that determining the level of exposure is not dependent on people, sometimes sick people, recalling their rates of phone use. The cellular companies’ files were used to determine exposures. However, how many people per cellular subscription used the phone cannot be determined.

“We need to get more precise information,” Johansen said. “It’s always a problem in a large cohort study to refine the exposures. I don’t think we can correct for that.”

Researchers in the Danish study were able to take advantage of the country’s high-quality cancer registry as well as its meticulous record keeping and data linkage. Not only were they able to evaluate several kinds of cancer, they will also be able to follow participants for many years as the technology changes and track the incidence of other diseases.

In 1968, Denmark established a Central Population Register, in which each citizen is assigned a unique 10-digit identification number. A nationwide cancer registry has operated there since 1942. Once the cell phone companies agreed to allow the Danish researchers access to their computerized files (which, according to Johansen, took a year and a half of negotiations), they were able to identify the subscribers and length of subscription. The Central Population Register provided them with the identification numbers of the subscribers that were then used to track cancer incidence rates from the Danish Cancer Registry.

For some scientists, such as Robert Park, Ph.D., a physicist at the University of Maryland, and the author of the editorial that accompanies the Danish study (see p. 166), the three most recent studies settle the safety issue of the phones. He is particularly impressed with the Danish report. “This is a really sound study. It’s a large cohort. The database is reliable. This ought to put the issue to rest.”