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Improvements in PM₁₀ Exposure and Reduced Rates of Respiratory Symptoms in a Cohort of Swiss Adults (SAPALDIA)

¹ Institute of Social and Preventive Medicine, University of Basel, Basel; ² Division of Pulmonary Medicine, University Hospitals of Geneva, Geneva; ³ Hirslanden Klinik, Aarau; ⁴ Zürcher Höhenklinik, Wald; ⁵ Division of Pulmonary Medicine, Cantonal Hospital, Aarau; ⁶ Hôpital Intercantonal de la Broye, Payerne; ⁷ Luzerner Höhenklinik, Montana; ⁸ Alpine Kinderklinik, Davos; ⁹ Division of Pulmonary Medicine, Regional Hospital Lugano, Switzerland; ¹⁰ Centre for Research in Environmental Epidemiology (CREAL), Catalan Institution for Research and Advanced Studies, ICREA, Municipal Institute of Medical Research (IMIM-Hospital del Mar), and CIBER Epidemiologia y Salud Pública (CIBERESP), Barcelona, Spain; ¹¹ Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts; and ¹² Department of Environmental & Occupational Health Sciences, University of Washington, Seattle, Washington

Correspondence and requests for reprints should be addressed to Christian Schindler, Ph.D., Institute of Social and Preventive Medicine, University of Basel, Steinengraben 49, CH 4051 Basel, Switzerland. E-mail: christian.schindler{at}unibas.ch

Rationale: Reductions in mortality following improvements in air quality were documented by several studies, and our group found, in an earlier analysis, that decreasing particulate levels attenuate lung function decline in adults.

Objectives: We investigated whether decreases in particulates with an aerodynamic diameter of less than 10 µm (PM₁₀) were associated with lower rates of reporting respiratory symptoms (i.e., decreased morbidity) on follow-up.

Methods: The present analysis includes 7,019 subjects who underwent detailed baseline examinations in 1991 and a follow-up interview in 2002. Each subject was assigned model-based estimates of average PM₁₀ during the 12 months preceding each health assessment and the difference was used as the exposure variable of interest (PM₁₀). Analyses were stratified by symptom status at baseline and associations between PM₁₀ and change in symptom status during follow-up were adjusted for important baseline characteristics, smoking status at follow-up, and season. We then estimated adjusted odds ratios for symptoms at follow-up and numbers of symptomatic cases prevented due to the observed reductions in PM₁₀.

Measurements and Main Results: Residential exposure to PM₁₀ was lower in 2002 than in 1991 (mean decline 6.2 µg/m³; SD = 3.9 µg/m³). Estimated benefits (per 10,000 persons) attributable to the observed changes in PM₁₀-levels were: 259 (95% confidence interval [CI]: 102–416) fewer subjects with regular cough, 179 (95% CI, 30–328) fewer subjects with chronic cough or phlegm and 137 (95% CI, 9–266) fewer subjects with wheezing and breathlessness.

Conclusions: Reductions in particle levels in Switzerland over the 11-year follow-up period had a beneficial effect on respiratory symptoms among adults.

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Major reductions in air pollutant levels have beneficial effects on adult mortality and on respiratory morbidity in children. Moreover, decreasing particulate levels is associated with a slowed age-related lung function decline in adults. What This Study Adds to the Field The results of the present study suggest that, in addition to being beneficial for lung function, reductions in particulate levels also lead to a decrease in respiratory symptoms among adults.