WHO宣布手机可能致癌(Cell Phones Possibly Carcinogenic, WHO Says)

May 31, 2011 ? The World Health Organization (WHO) announced today that radiation from cell phones can possibly cause cancer. According to the WHO"s International Agency for Research on Cancer (IARC), radiofrequency electromagnetic fields have been classified as possibly carcinogenic to humans (group 2B) on the basis of an increased risk for glioma that some studies have associated with the use of wireless phones.丽水市人民医院血液科曲志刚

This announcement was based on an extensive review of studies on cell phone safety by a working group of 31 scientists from 14 countries, who have been meeting regularly to evaluate the potential carcinogenic hazards from exposure to radiofrequency electromagnetic fields. They reviewed exposure data, studies of cancer in humans and experimental animal models, and other relevant data.

More specifically, the IARC Monograph Working Group discussed and evaluated literature that included several exposure categories involving radiofrequency electromagnetic fields:

• Occupational exposures to radar and to microwaves;
• Environmental exposures associated with transmission of signals for radio, television, and wireless telecommunication; and
• Personal exposures associated with the use of wireless telephones.

"Given the potential consequences for public health of this classification and findings," said IARC Director Christopher Wild, PhD, in a news release, "it is important that additional research be conducted into the long-term, heavy use of mobile phones. Pending the availability of such information, it is important to take pragmatic measures to reduce exposure such as hands-free devices or texting."

Inconsistent Data and Opinions

Cellular telephones have become an integral part of everyday life, and the number of users is estimated at 5 billion globally. However, as previously reported by Medscape Medical News, there has been growing concern over possible health risks associated with the use of cell phones. In particular, some data have suggested that their use, especially over the long term, represent a "significant" risk for brain tumors.

But study results have been inconsistent, although some European countries have taken precautionary measures aimed specifically at children.

Some of the strongest evidence supporting a link between brain tumors and cell phone use comes from a series of Swedish studies, led by Lennart Hardell, MD, PhD, from the Department of Oncology, Orebro Medical Center. These studies showed that risk increased with the number of cumulative hours of use, higher radiated power, and length of cell phone use. They also reported that younger users had a higher risk. (Int J Oncol. 2006;28:509-518; Int Arch Occup Environ Health. 2006;79:630-639; Arch Environ Health. 2004;59:132-137; Pathophysiology. 2009;16:113-122).

The issue of cell phone safety was to have been settled once and for all by the huge 13-nation industry-funded Interphone study. But to date, the industry-funded Interphone studies found no increased risk for brain tumors from cell phone use, with only 4 exceptions. The findings contradicted the Swedish studies, which were independent of industry funding.

Consistent with the literature, there is no consensus among physicians and scientists about the severity of risk, or if one even exists. One issue in attempting to evaluate the potential connection between brain tumors and cell phone use is the relatively short period of time that these devices have been heavily used in a large population and the long latency period for many tumors.

The National Cancer Institute, for example, has stated that although a consistent link has not been established between cell phone use and cancer, "scientists feel that additional research is needed before firm conclusions can be drawn." In a similar fashion, the American Cancer Society points out that even though the weight of the evidence has shown no association between cell phone use and brain cancer, information on the potential health effects of very long-term use, or use in children, is simply not available.

Evidence Strong Enough

The WHO established the International Electromagnetic Fields (EMF) Project in 1996, in response to public and governmental concern, with the goal of evaluating the possibility of adverse health effects from electromagnetic fields. In a press release issued last year, the WHO stated that it would conduct a formal health risk assessment of radiofrequency fields exposure by 2012, but in the interim, the IARC would review the carcinogenic potential of mobile phones this year.

Jonathan Samet, MD, chairman of the working group, notes that "the evidence, while still accumulating, is strong enough to support a conclusion and the 2B classification.

"The conclusion means that there could be some risk, and therefore we need to keep a close watch for a link between cell phones and cancer risk," he said in a news release.

A full report summarizing the main conclusions and evaluations of the IARC Working Group is slated to be published online soon in The Lancet Oncology and in print in its July 1 issue.