ScienceDaily (Nov. 22, 2006) — Over time, inhaling environmental tobacco smoke (ETS)--a process often called "passive smoking"--can cause otherwise healthy adults to develop chronic respiratory symptoms.

The findings appear in the second issue for November 2006 of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.

Margaret W. Gerbase, Ph.D., of the Division of Pulmonary Medicine at the University Hospitals of Geneva in Switzerland, and 11 associates assessed the respiratory symptoms in 1,661 never-smokers over an 11-year period. All individuals in the study cohort participated in the Swiss Study on Air Pollution and Lung Diseases in Adults in 1991 and again in 2002. The two-part study was the first large-scale investigation of the long-term health effects of moderate ambient air pollution in Switzerland.

"The results of our longitudinal assessment of ETS effects in asymptomatic never-smokers showed that exposure to ETS was associated with the development of respiratory symptoms," said Dr. Gerbase. "A particularly strong effect of continued exposure to ETS was observed among previously asymptomatic individuals with bronchial hyper-reactivity."

The researchers found ETS exposure to be strongly associated with the development of cough. In subjects with bronchial hyper-reactivity, they observed a link between ETS and symptoms like wheeze, cough, dyspnea (shortness of breath) and chronic bronchitis. However, only the association between dyspnea and ETS reached statistical significance.

According to the authors, individuals with bronchial hyper-reactivity who are persistently exposed to ETS are at particular risk of developing early-onset chronic respiratory disease. "Symptom development in our subjects was accompanied by decrements in spirometric indices reflecting peripheral airway narrowing, notably in subjects with bronchial hyper-responsiveness," said Dr. Gerbase.

Of the 1,661 participants, 1,202 individuals (72.4 percent) reported never being exposed to ETS, 309 persons (18.6 percent) reported exposure only during the 1991 survey, and 150 subjects (9 percent) reported exposure both in 1991 and 2002.

"Indirect evidence derived from smokers shows that airway responsiveness increases the risk to develop cough, phlegm, dyspnea and chronic bronchitis," said Dr. Gerbase. "Cessation of smoking leads to remission of symptoms and improvement in airway hyper-reactivity."

Excluded from participation in the study at baseline (1991) were all potential participants who reported such symptoms as wheeze, cough, phlegm, dyspnea and chronic bronchitis, or who were taking a medication for asthma at the time.

The researchers concluded that their findings support the need for policies protecting all nonsmokers from the "detrimental effects" of ETS.

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