| New Evidence on Dangers of Secondhand Smoke |
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By Lee Bowman
Scripps Howard News Service An international team of cancer experts working for the World Health Organization has fingered secondhand smoke for the first time as contributing to cancer in people who don't smoke. The experts also greatly expanded an official list of organs and body systems where research shows smoking contributes to cancer. "As we continue to examine the cancer risk caused by smoking, we are learning that it is even greater than previously thought," said a working group for the International Agency for Research on Cancer, a branch of the World Health Organization. The team, made up of 29 experts from 12 countries, issued a summary of its report on Wednesday after six months of analyzing more than 3,000 studies that involved millions of people in six continents. The complete report will be published later this year. The experts said their review, the first such effort since 1986, allowed them to consider how smoking affects people over a lifetime, and to begin to consider the effects of passive smoking. "Only now are we beginning to see the full picture of what happens when a generation begins to smoke at an early age, as youth do, and then smoke across their whole lifetime. Before, we had only snapshots,'' said Dr. Jonathan Samet, the head of the panel and chairman of epidemiology at Johns Hopkins School of Public Health. The United Nations estimates that there are 1.2 billion smokers worldwide. The agency said tobacco-caused disease would eventually kill half of all persistent cigarette smokers with cancer, heart disease, emphysema or other smoking-related illnesses. The report also concludes that non-smokers who spend a lot of time around smokers are exposed to the same carcinogens as active smokers. "Secondhand smoke is carcinogenic to humans,'' the scientists said, the first time the agency has formally reached this conclusion. "This issue of involuntary smoking is really important in public health, because it lends support to efforts under way in many places to make bars, restaurants and other public places smoke-free,'' said Stephen Hecht, a researcher at the University of Minnesota's Cancer Center who specializes in the chemistry and toxicology of tobacco smoke and is a member of the committee. "To the extent this ostracizes tobacco use and encourages people to stop smoking, that's all to the good,'' he added. While research has found that typical levels of passive exposure to smoke has been shown to cause lung cancer among "never smokers," the scientists said they don't have enough evidence to show that cigarette smoke can cause other types of cancer. "It's unambiguous that secondhand smoke is causing lung cancer, but there's just not enough evidence to associate it with anything else,'' Hecht said. The scientists also said that it's uncertain how much cancer risk is faced later in life among children exposed to parental smoking and tobacco smoke in other settings as they grow up. The International Agency for Research on Cancer monitors and reviews cancer studies about materials that may contribute to cancer around the world. The agency has assessed the carcinogenic potential to humans of more than 880 agents since it was established 30 years ago. The agency had already said that smoking causes lung, head and neck cancers and also affects the pancreas and bladder. Now it has added stomach, liver, cervix, kidney, nasal sinuses and myeloid leukemia to the list. The experts noted that tobacco smoke does not cause all cancers, in particular that smoking "causes little or no risk of breast cancer or endometrial (lining of the uterus) cancer.'' The report noted that prostate cancer does not seem to be caused by smoking. The panel stressed that not only cigarettes, but also other forms of tobacco, including pipes, cigars and bidis, contribute to the burden of disease from tobacco, even though smokers don't inhale the smoke from those products deeply, if at all. "Our point about these things, and some of the new cancers, is that many of the carcinogens in tobacco are systemic, they don't have to get to organs just through the lungs to do their damage,'' Hecht said. On the Net: www.iarc.fr. (Contact Lee Bowman at bowmanl@shns.com or online at http://www.shns.com.)
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