Secondhand smoke increases the risk of breast cancer in young women, although many experts still refuse to accept the research, published by the California Environmental Protection Agency in 2006, because no study has conclusively linked direct smoke inhalation to breast cancer, Dr. Stan Glantz, director of the Center for Tobacco Control Research and Education at the University of California, San Francisco, claimed in his Thursday lecture at the Dartmouth-Hitchcock Medical Center.
Glantz likened the breast cancer researchers who doggedly oppose the California EPA's findings to "religious fanatics," referring to their unwillingness to accept the findings.
The link between smoke inhalation and breast cancer, which Glantz called "the most important scientific development in the last 10 years," follows logically, according to Glantz, because cigarettes contain many known mammary carcinogens, such as benzene.
"If you're a breast cell minding your own business and some benzene from smoke goes floating by, it doesn't have a sign on it saying, 'I'm a cigarette, never mind,'" Glantz said. "If benzene is a mammary carcinogen in diesel exhaust, why isn't it a carcinogen for cigarettes?"
Previous studies on smoke inhalation and breast cancer compared active smokers to a control group of both people who inhale only secondhand smoke and those with little or no exposure to cigarette smoke, according to Glantz. The negative effects of smoking were not revealed by the study because secondhand smoke inhalation in the control group also increased the rates of breast cancer. If studies compared smokers only to people who inhale little secondhand smoke, a strong correlation between smoking and breast cancer would be evident, Glantz said.
Despite the EPA's findings, the Surgeon General has not recognized the correlation between smoke inhalation and breast cancer, a double standard, Glantz believes, since former Surgeon General C. Everett Koop '37, who was present at the lecture, announced in 1986 that seconhand smoke increased rates of lung cancer based on even less evidence, Glantz said.
"The evidence is suggestive but not sufficient to infer a causal relationship between secondhand smoke and breast cancer," former Surgeon General Vice Admiral Richard H. Carmona wrote in his 2006 report, "The Health Consequences of Involuntary Exposure to Tobacco Smoke."
The EPA's study found no link between secondhand smoke and breast cancer in post-menopausal women, possibly because carcinogens have a greater effect on pre-menopausal breasts that have not lactated, Glantz said.
"Breast cancer in young and old women are two different diseases," he said. "They present in clinics differently and require different treatments."
Secondhand smoke inhalation is the fourth leading preventable cause of death, killing 50,000 people each year, according to Glantz. It trails only active smoking, alcohol and obesity, he said. Second hand smoke is even more toxic than direct smoke, with three to four times as many toxic chemicals because the smoke diffuses through the air.
A 1978 study by tobacco companies indicated that the industry viewed the dangers of secondhand smoke as the greatest threat to sales, Glantz said. Companies said they believed public attitude towards smoking would remain positive as long as smoking only harmed the smokers, but the companies were unsure how to counter the fact that smoking also endangered the lives of non-smokers.
"Companies sell cigarettes because they're important for social standing; to be sexy, hip and cool. All the messages embodied in the movies," Glantz said. "If you feel guilty about smoking next to people, if you have to leave the party to smoke, it becomes a social negative. Tobacco companies just don't know how to deal with that."
