Moderate levels of secondhand smoke deliver nicotine to the brain
NIH-funded study shows how secondhand smoke may increase vulnerability to nicotine addiction
Exposure to secondhand smoke, such as a person can get by riding in an enclosed car while someone else smokes, has a direct, measurable impact on the brain — and the effect is similar to what happens in the brain of the person doing the smoking. In fact, exposure to this secondhand smoke evokes cravings among smokers, according to a study funded by the National Institute on Drug Abuse (NIDA), part of the National Institutes of Health.
The study, published today in Archives of General Psychiatry, used positron emission tomography (PET) to demonstrate that one hour of secondhand smoke in an enclosed space results in enough nicotine reaching the brain to bind receptors that are normally targeted by direct exposure to tobacco smoke. This happens in the brain of both smokers and non-smokers.
Previous research has shown that exposure to secondhand smoke increases the likelihood that children will become teenage smokers and makes it more difficult for adult smokers to quit. Such associations suggest that secondhand smoke acts on the brain to promote smoking behavior.
"These results show that even limited secondhand smoke exposure delivers enough nicotine to the brain to alter its function," said NIDA Director Nora D. Volkow, M.D. “Chronic or severe exposure could result in even higher brain nicotine levels, which may explain why secondhand smoke exposure increases vulnerability to nicotine addiction."
"This study gives concrete evidence to support policies that ban smoking in public places, particularly enclosed spaces and around children," said Arthur Brody, M.D., of the UCLA Department of Psychiatry & Biobehavioral Sciences and corresponding author for the article.
The Surgeon General's Report concluded in 2006 that secondhand smoke causes heart disease and lung cancer in nonsmoking adults and many serious health conditions in children, including sudden infant death syndrome, respiratory infections, and more severe asthma. According to the CDC, almost 50,000 deaths per year can be attributed to secondhand smoke. For more information or for resources to help quit smoking, go tohttp://www.nida.nih.gov/DrugPages/Nicotine.html.
The study can be found online at: http://archpsyc.ama-assn.org/ 
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How much exposure to tobacco smoke can the lungs endure before damage ensues? The answer appears to be none, based on gene activity measured by researchers at Cornell University.1 “No level of smoking or exposure to secondhand smoke [SHS] is safe. Even at the lowest detectable levels of exposure, we could detect changes in gene expression within the cells lining the airways,” says coauthor Ronald Crystal, head of pulmonary and critical care medicine at New York-Presbyterian/Weill Cornell Medical Center.
