Effects of environmental tobacco smoke exposure on pulmonary function and respiratory health in adults: Update 1997

Eighteen epidemiology studies have examined the relationship between chronic environmental tobacco smoke (ETS) exposure and pulmonary function. A statistically significant relationship between chronic ETS exposure and a specific spirometric endpoint was reported in 5 of 17 studies that measured forced expiratory volume in 1 s (FEV1), 2 of 9 studies that measured forced vital capacity (FVC) and 3 of 5 studies that measured mean forced expiratory flow during the middle half of the FVC. Fourteen of 24 epidemiological studies report a statistically significant association between chronic ETS exposure and a clinical endpoint, although there is little consistency from one report to the next when a specific endpoint is considered. A statistically significant association was reported in 2 of 9 studies for cough, 3 of 9 studies for phlegm and expectoration, 6 of 10 studies for dyspnea and shortness of breath, 3 of 6 studies for bronchitis, and 8 of 18 studies dealing with asthma incidence, exacerbation, or symptoms. The inconsistency of association in the foregoing functional and clinical epidemiology studies could either reflect absence of such an association or methodology problems such as reliability of spirometric measurement, lack of verification of clinical endpoint, errors in classification of smoking and ETS exposure status and inappropriate control of confounding variables. The effects of acute ETS exposure (at levels equivalent to or exceeding real-life smoke-polluted environments) have been examined in experimental studies in which spirometric measures were obtained prior to, during, and after exposure of subjects to machine-generated tobacco smoke. Six of seven studies suggest that acute ETS exposure, while serving as an irritant to the upper respiratory tract, fails adversely to affect pulmonary function of normal adults. The effect of acute ETS exposure in asthmatic subjects has been examined in 15 studies. These studies suggest that acute exposure to ETS does not consistently evoke adverse pulmonary effects in most asthmatics. Several studies from a single research group suggest that a small sub-set of asthmatics may respond to acute ETS exposure with a greater than or equal to 20% decrement in FEV1 as well as an increased responsiveness to bronchoconstrictors. The mechanism for this responsiveness does not appear to be allergic in nature and is subject to speculation.