An Analysis of the Association Between Respiratory Symptoms in Subjects with Asthma and Daily Air Pollution in Spokane, Washington

Abstract

The association between respiratory symptoms and ambient levels of particulate matter (PM) air pollution has been the focus of several panel studies. The majority of studies focused only on PM₁₀, were conducted for relatively short periods, reported peak flow data, and involved children with asthma. The goal of our study was to evaluate the effect of particulate matter of various size fractions (PM₁₀, PM_2.5, PM_1.0, and PM coarse fraction) on respiratory symptoms in both adults and children with asthma monitored over many months. Daily diary data on respiratory symptoms and medication use were collected. Air pollution data were collected by the local air agency and Washington State University. Data were collected in Spokane, WA, a semiarid city with diverse sources of particulate matter, including motor vehicles, woodstoves, agricultural burning, resuspended road dust, and dust storms. Sixteen adults and nine children living in Spokane participated in the study. The majority of adult subjects participated for over 1 yr and the children were studied for over 8 mo. In the children, we found a strong association between cough and PM₁₀, PM_2.5, PM coarse fraction, and PM_1.0 (p <. 05). Sputum production and runny nose were associated with PM₁₀ and coarse fraction. However, no association was found between the presence of any respiratory symptom any PM metric in the adult subjects. These positive associations between various metrics of PM and respiratory symptoms in children suggest that children are more sensitive than adults to the effects of increased levels of PM air pollution or that the central site monitor was more representative for children who spend more time outdoors than adults. These findings also suggest that both larger and smaller particles can aggravate asthma symptoms.

This research was supported in part by the Washington State Department of Ecology, the American Lung Association of Washington, NIH grant 5T32 ES07262, NIEHS Center Grant P30 ES07033, and EPA Center Grant R827355. We thank the Spokane County Air Pollution Control Agency for air pollution data. We thank Gary A. Norris for his assistance with the air quality data. We thank Bill O'Brien for assistance with data management and Chris Slaughter for his assistance with Stata. We also thank the subjects who participated in our study.