© 2001 by Oxford University Press
Journal of the National Cancer Institute, Vol. 93, No. 9, 669-670,
May 2, 2001
© 2001 Oxford University Press
NEWS |
Drop in Cotinine Levels Signals Less Smoke Exposure, Experts Say
In what public health officials are hailing as a victory for indoor smoking bans, average blood levels of a nicotine byproduct plummeted by 75% in nonsmokers over the last decade. According to the authors of a recent Centers for Disease Control and Prevention report, the drop documents tangible results for ever tighter smoking rules.
"Our nationwide efforts to reduce indoor smoking are working," said Terry Pechacek, Ph.D., from the CDC’s Office on Smoking and Health. "But there are still too many people exposed to smoke, and this should encourage us to do more."
The study measured the amount of cotinine, a nicotine metabolite, in the blood of 2,200 Americans representing a cross-section of the country. In recent years, cotinine has been established as the most reliable marker of exposure to environmental tobacco smoke. It survives in the blood much longer than nicotine, making it an efficient measure of cumulative exposure.
The CDC first measured cotinine in a nationwide sample during the period 1988 to 1991, as part of the long-running National Health and Nutrition Examination Survey. At that time, the median level of cotinine in nonsmoking Americans was 0.20 nanograms per milliliter. In the most recent sample, from 1999, the median level was 0.05 nanograms per milliliter. Active smokers typically carry cotinine loads tens or hundreds of times higher.
"To see a fourfold drop in any environmental exposure is unheard of," said Richard J. Jackson, M.D., director of the CDC’s National Center for Environmental Health. "I’ve never seen it before."
While the sample was too small to break out by region, the authors did offer a breakdown by age and race. Children and adolescents ages 3 through 19 carried higher average cotinine levels than adults. The most exposed youngsters—the 10% with the most cotinine—had levels more than twice as high as those found in the most exposed adults. Blacks, on average, had levels more than double that seen in whites. And men had higher levels than women.
Experts attribute the drop in cotinine levels to 3 decades of public health efforts to cut exposure to secondhand smoke and ever more stringent local, state, and federal smoking restrictions. By the 1990s, a plethora of laws and regulations reinforced a trend begun in the 1970s to squeeze smokers into fewer and fewer public spaces. Now, off-limits areas include most domestic airline flights; virtually all workplaces in California, Maryland, and Vermont; restaurants; and workplaces and public spaces in much of the country.
Pechacek said that future data will more precisely track secondhand smoke exposure, helping the CDC and other agencies to direct anti-smoking resources.
The cotinine data come from the CDC’s first ever report on 27 toxins found in a cross-section of Americans. While three of the chemicals—cotinine and the metals lead and cadmium—had previously been measured in large population studies, the new report marks the first such tracking of 24 other chemicals, including mercury and other heavy metals.
Also included are the breakdown products of common pesticides and metabolites of newer varieties of plastics called phthalates. CDC will continue tracking the levels of these new toxins in addition to adding 25 or so more per year to its analysis.
Advances in chemical analysis, specifically high-tech spectroscopy, made feasible the direct measurement of these toxins in blood and urine, said Jackson, an author on the report. Previous environmental research relied on estimates of exposures obtained from air, water, and soil samples.
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