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Ralph J. Delfino,¹ Robert S. Zeiger,^2,3 James M. Seltzer,^2,4 Donald H. Street,⁵ and Christine E. McLaren¹

¹Epidemiology Division, Department of Medicine, University of California, Irvine, Irvine, California, USA; ²Department of Pediatrics, University of California, San Diego, School of Medicine, La Jolla, California, USA; ³Department of Allergy, Southern California Permanente Medical Group, San Diego, California, USA; ⁴Indoor Hygienic Technologies Corporation, Rancho Santa Fe, California, USA; ⁵Hollistier-Stier Laboratories LLC, Allergy Products, Independence, Oregon, USA

Abstract

Maxima of hourly data from outdoor monitors may capture adverse effects of outdoor particulate matter (PM) exposures in asthmatic children better than do 24-hr PM averages, which form the basis of current regulations in the United States. Also, asthmatic children on anti-inflammatory medications may be protected against the proinflammatory effects of air pollutants and aeroallergens. We examined strengths of pollutant associations with asthma symptoms between subgroups of asthmatic children who were on versus not on regularly scheduled anti-inflammatory medications, and tested associations for different particle averaging times. This is a daily panel study of 22 asthmatic children (9-19 years of age) followed March through April 1996 (1,248 person-days) . They lived in nonsmoking households in a semirural area of Southern California within the air inversion mixing zone (range, 1,200-2,100 feet) with transported air pollution from urban areas of Southern California. The dependent variable derived from diary ordinal scores is episodes of asthma symptoms that interfered with daily activities. Minimum to 90th-percentile levels of exposures at the outdoor monitoring site were 12-63 µg/m³ for 1-hr PM < 10 µm in aerodynamic diameter (PM₁₀) ; 8-46 µg/m³ for 8-hr PM₁₀ ; 7-32 µg/m³ for 24-hr PM₁₀ ; 45-88 ppb for 1-hr O₃ ; 6-26 ppb for 8-hr NO₂ ; 70-4,714 particles/m³ for 12-hr daytime fungi ; and 12-744 particles/m³ for 24-hr pollen. Data were analyzed with generalized estimating equations controlling for autocorrelation. There was no confounding by weather, day of week, or linear time trend. Associations were notably stronger in 12 asthmatic children who were not taking anti-inflammatory medications versus 10 subjects who were. Odds ratios (95% confidence intervals) for asthma episodes in relation to lag 0 minimum to 90th-percentile pollutant changes were, respectively, 1-hr maximum PM₁₀, 1.92 (1.22-3.02) versus 0.96 (0.25-3.69) ; 8-hr maximum PM₁₀, 1.68 (0.91-3.09) versus 0.75 (0.18-3.04) ; 24-hr average PM₁₀, 1.35 (0.82-2.22) versus 0.80 (0.24-2.69) ; 1-hr maximum O₃, 1.28 (0.75-2.17) versus 0.76 (0.24-2.44) ; 8-hr maximum NO₂, 1.91 (1.07-3.39) versus 1.08 (0.30-3.93) ; 12-hr fungi, 1.89 (1.24-2.89) versus 0.90 (0.35-2.30) ; 24-hr pollen, 1.90 (0.99-3.67) versus 0.85 (0.18-3.91) . Pollutant associations were stronger during respiratory infections in subjects not on anti-inflammatory medications. Although lag 0 1-hr maximum PM₁₀ showed the strongest association, the most robust associations were for lag 0 and 3-day moving averages (lags 0-2) of 8-hr maximum and 24-hr mean PM₁₀ in sensitivity analyses testing for thresholds. Most pollutant effects were largely driven by concentrations in the upper quintile. The divergence of exposure-response relationships by anti-inflammatory medication use is consistent with experimental data on inflammatory mechanisms of airborne pollutants and allergens. Key words: asthma, epidemiology, longitudinal data analysis, ozone, panel study, particulate air pollution. Environ Health Perspect 110:A607-A617 (2002) . [Online 13 September 2002]

http://ehpnet1.niehs.nih.gov/docs/2002/110pA607-A617delfino/ abstract.html

Address correspondence to R.J. Delfino, Epidemiology Division, Department of Medicine, College of Medicine, 224 Irvine Hall, University of California, Irvine, Irvine, CA 92697-7550 USA. Telephone: (949) 824-1767. Fax: (949) 824-1343. E-mail: rdelfino@uci.edu

We appreciate the skilled efforts of our clinic coordinators K. Mostafa of the Southern California Permanente Medical Group and L. Skific of the Clinical Research Institute, and the assistance in recruitment by the Alpine School District. We thank our research assistants P. Anderson and L. Crane, and M. Hossain and staff at the San Diego Air Pollution Control District for providing stationary site data for air pollutant gases and weather and for their assistance in placement of the remaining monitors. Most of all, we thank the study participants for their diligent efforts.

This project was supported by grant ES06214 from the National Institute of Environmental Health Sciences (NIEHS) . Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS.

Received 5 November 2001 ; accepted 14 March 2002.