Do Cellular Phones Cause Brain Cancer?

Because widespread cellular phone use is little more than a decade old, there has been limited opportunity to examine its long-term health effects. However, 3 recently published, large case-control studies and one large cohort study have compared cell phone use among brain cancer patients and people without brain cancer. In each of the 3 case-control studies, patients with brain cancer were compared to people free of brain cancer, in terms of their past use of cellular phones. If the patients reported more cellular phone use than those in the study who did not have brain cancer, and if no other differences between the 2 groups could account for the brain cancers, these observations would provide evidence of a possible link between cellular phones and brain cancer.

The first study compared 233 brain cancer patients diagnosed between 1994 and 1996 in the Stockholm and Uppsala regions of Sweden with 466 controls. The second study, conducted by the American Health Foundation, compared 469 brain cancer patients diagnosed between 1994 and 1998 in New York, Providence, and Boston with 422 controls. The third and largest study, conducted by the U.S. National Cancer Institute, compared 782 brain cancer patients diagnosed in Phoenix, Boston, and Pittsburgh between 1994 and 1998 with 799 controls.

All 3 case-control studies had similar results:

• First, the patients with brain cancer did not report more cellular phone use overall than the controls. This finding was true when all brain cancers were considered as a group, when individual types of brain cancer were considered, and when specific locations within the brain were considered. In fact, most of the studies showed a tendency toward a lower risk of brain cancer among cellular phone uses, for unclear reasons.
  
  
• Second, none of the studies showed a "dose-response relationship" -- a tendency for the risk of brain cancer to increase with increasing cellular phone use, which would be expected if cellular phone use caused brain cancer.
  
  
• Third, the studies did not show a clear link between the side of the head on which the brain cancer occurred and the side on which the cellular phone was used (with the possible exception of the Swedish study).

Recent results from the Swedish Interphone study of long-term cell phone use, using a population-based case control design indicate the same conclusions. There was no association with risk of any of the brain tumor types studied (glioma or meningioma), or with duration of use, side of use, or amount of use.

Results of the long-term cohort study, which linked data on all of the 420,095 cellular telephone users in Denmark between 1982 and 1995 to the Danish Cancer Registry, agree with the findings of the case-control studies. Cellular phone use, even for more than 10 years, was not associated with an increased risk of developing brain tumors or cancer overall, nor was there an association with any brain tumor subtypes or with tumors in any location within the brain. As in the case-control studies, no link was found between brain tumor risk and RF dose, as assessed by length of cellular phone use, date since first subscription, age at first subscription, or type of cellular phone used.

However, these published studies have only limited ability to examine the association between cell phone use and specific subtypes of brain cancer. One subtype that has been studied is acoustic neuroma, a relatively rare, slow-growing tumor of the acoustic nerve (which transmits the sensation of hearing from the ear to the brain) that occurs in less than one adult per 100,000 people per year. At least 9 epidemiological studies have looked for an association between the use of cellular telephones and acoustic neuroma. Results of these studies have been inconsistent, due largely to variations in study design and statistical challenges posed by the rarity of these tumors. One of the largest and most recent studies analyzed data from the 5 northern European countries, and found no relation of acoustic neuroma risk with cell phone use, duration of use, or number of calls made. According to the researchers, “The study suggested there is no substantial risk of acoustic neuroma in the first decade after starting mobile phone use. However, an increase in risk after longer term us or after a longer lag period could not be ruled out.”

In summary, there is now considerable epidemiologic evidence that shows no consistent association between cellular phone use and overall risk of brain cancer. Some uncertainty remains regarding a possible association with acoustic neuromas. Several large studies now in progress will add markedly to the evidence within a few years.

What the Animal and Laboratory Evidence Suggests

Most but not all laboratory studies have reported a lack of RF-induced DNA damage. No increase in spontaneous brain tumors was observed in 2 studies of rats exposed to RF. The risk of lymphoma after radiation in rodents genetically altered to be especially sensitive to cancer-causing influences was increased following whole-body RF exposure.

What Expert Agencies Say

Based on animal and human evidence like the examples above, expert agencies have evaluated the cancer-causing potential of cell phone use.

In October 1999, the Center for Devices and Radiological Health (CDRH), part of the U.S. Food and Drug Administration (FDA), responded to increased media focus on cell phones and brain cancer by issuing a Consumer Update on Mobile Phones (including cellular phones). In its statement, the CDRH stated, "The available science does not allow us to conclude that mobile phones are absolutely safe, or that they are unsafe. However, the available scientific evidence does not demonstrate any adverse health effects associated with the use of mobile phones."

The FCC issued a statement in October 1999 in response to media assertions that some mobile phones exceed the maximum level of emitted radiation permitted. Claiming support from the Food and Drug Administration, the Environmental Protection Agency, the National Institute for Occupational Safety and Health, and the Occupational Safety and Health Administration, the FCC stated that its guidelines "already incorporate a large margin of safety between allowed levels of exposure and exposure thresholds that have been identified with known adverse health effects." The excess levels of exposure reported by the media were "well within that safety margin, and, therefore, there is no indication of any immediate threat to human health from these phones." The FCC is currently undertaking new research to verify the safety of RF levels emitted from mobile phones.

A recent consumer information document issued jointly by the FDA and FCC reaches the same conclusions:

"The available scientific evidence does not show that any health problems are associated with using wireless phones. There is no proof, however, that wireless phones are absolutely safe. Wireless phones emit low levels of radiofrequency energy (RF) in the microwave range while being used. They also emit very low levels of RF when in the stand-by mode. Whereas high levels of RF can produce health effects (by heating tissue), exposure to low level RF that does not produce heating effects causes no known adverse health effects. Many studies of low-level RF exposures have not found any biological effects. Some studies have suggested that some biological effects may occur, but such findings have not been confirmed by additional research. In some cases, other researchers have had difficulty in reproducing those studies, or in determining the reasons for inconsistent results."

The United States Environmental Protection Agency (EPA), National Toxicology Program (NTP), and the International Agency for Research on Cancer (IARC), 3 of the main exposure classifying agencies, have not evaluated the carcinogenicity (cancer-causing potential) of cell phone use.