Secondhand smoke affects nonsmokers in vehicles

A new study has revealed that secondhand smoke in motor vehicles poses a potentially major threat especially to nonsmokers sitting in an automobile with a smoker.

The study led by UC San Francisco researchers examined that the nonsmoking passengers showed elevated levels of butadiene, acrylonitrile, benzene, methylating agents and ethylene oxide.

Senior investigator Neal L. Benowitz, MD, a UCSF professor of medicine and bioengineering and therapeutic sciences, said that this group of toxic chemicals was thought to be the most important among the thousands in tobacco smoke that cause smoking-related disease.

For the study, 14 nonsmokers each sat for one hour in the right rear passenger seat of a parked sport utility vehicle behind a smoker in the driver's seat. During that time, the smoker smoked three cigarettes. The front and rear windows were opened 10 centimeters, or almost four inches.

Before being exposed to the smoke and then eight hours afterward, the nonsmokers' urine was analyzed for biomarkers of nine chemical compounds found in cigarette smoke that are associated with cancer, cardiovascular disease and respiratory diseases. Seven biomarkers showed a significant increase following exposure to secondhand smoke.

Lead author Gideon St. Helen, PhD, a postdoctoral researcher in the UCSF Department of Medicine, said that this revealed that people, especially children and adults with preexisting health conditions such as asthma or a history of heart disease should be protected from secondhand smoke exposure in cars.

The study is published in the journal Cancer, Epidemiology, Biomarkers and Prevention.