Cancer Link to Secondhand Smoke Tightened?

ScienceNow (September 9, 1997)


Hardly.

At the semi-annual meeting of the American Chemical Society, University of Minnesota researchers reportedly detected a tobacco-specific chemical in the urine of nine nonsmoking hospital workers caring for live-in patients in the smoking area of a Canadian veterans hospital. The chemical, NNAL-Gluc, is a metabolite of n-nitrosamine (NNK) and tobacco is supposedly one of the only sources of NNK. The researchers reported that study subjects had concentrations of NNAL-Gluc at levels 70 times lower than those found in smokers.

Based on this result, the researchers concluded the study "establishes a link between the epidemiology [of secondhand smoke] and the chemistry."

First, the epidemiology of secondhand smoke is a joke. More than 75 percent of the epidemiologic studies fail to link secondhand smoke with cancer. The remaining studies rely on weak statistical associations without reliable exposure data and almost no control of major confounding risk factors. So I'm not sure these researchers really want their study "linked" to the secondhand smoke epidemiology--unless they think their work is funny.

Second, exposure does not equal disease. Even assuming NNK is tobacco-specific and NNK-Gluc is a biomarker of exposure to secondhand smoke, finding NNK-Gluc in urine does not mean secondhand smoke causes lung cancer. At best, it means that the study subjects were exposed to secondhand smoke. Nothing more.

If these guys want to "tighten" something, it ought to be their grip on science.


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