Study objectives: To identify characteristics associated with respiratory symptoms due to an episode of air pollution.
Design: Mail survey.
Setting: In October 1992, the population of the city of Winnipeg was exposed to elevated levels of particulate matter (total and <10 microm size), carbon monoxide, nitrogen dioxide, and volatile organic compounds due to smoke from adjacent fields where farmers were burning agricultural residue (straw and stubble).
Participants: We surveyed 428 participants in the ongoing Lung Health Study (35 to 64 years old, both sexes) with mild to moderate airways obstruction (mean FEV1 percent predicted 73+/-12%), and a high level of airways hyperreactivity (23% of men and 37% of women).
Results: While 37% of subjects were not bothered by smoke at all, 42% reported that symptoms (cough, wheezing, chest tightness, shortness of breath) developed or became worse due to the air pollution episode and 20% reported that they had breathing trouble. Those with symptoms were more likely to be female than male and were more likely to be ex-smokers than smokers. Subjects with asthma and chronic bronchitis were also more likely affected. The degree of airways obstruction and the level of bronchial hyperresponsiveness were not associated with increased susceptibility.
Conclusions: Gender, smoking habit, and respiratory symptoms but not bronchial hyperresponsiveness or the degree of airways obstruction are factors influencing susceptibility to symptoms due to air pollution in adult smokers and former smokers.