Nonsmokers living with a smoker have an elevated risk of lung cancer. In efforts to pinpoint the reason, researchers have now found evidence of a potent tobacco-specific carcinogen in nonsmokers exposed to smoke at home.
In the past, researchers have linked cigarette smoke to lung cancer in nonsmokers by finding noncarcinogenic cigarette compounds, including nicotine, in nonsmokers’ blood or urine. These compounds confirmed home exposure to smoke, but not necessarily to smoke’s carcinogens.
So, Kristin E. Anderson and her colleagues at the University of Minnesota’s Comprehensive Cancer Center in Minneapolis focused on a nitrosamine known as NNK, which scientists believe plays a major role in smoking-induced lung cancers. Not only do smokers possess high concentrations of NNK in their bodies, but animals treated with this compound develop the lung tumor that typifies smoking-related cancer in people.
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The Minnesota researchers collected urine from 45 nonsmoking women and their husbands. Twenty-three of the men smoked; the rest didn’t.
Concentrations of NNK’s breakdown products in the urine of women married to smokers were only 20 percent as high as their husbands’–but between five and six times as high as concentrations excreted by the women married to nonsmokers. Anderson’s group reports its findings in the March 7 Journal of the National Cancer Institute.
“There have been at least 30 epidemiological studies showing that there is an increased risk of lung cancer in nonsmoking women whose spouses smoked,” Anderson notes. The new data point to one agent behind passive smoke’s link to cancer, she says. However, “my suspicion is that if we looked, we would find other [smoking-related] carcinogens in the women.”