AIR POLLUTION AND ACUTE CARDIO-RESPIRATORY VISITS IN AN AMBULATORY CARE SETTING: TWO YEAR AND PRELIMINARY FOUR YEAR RESULTS

Introduction: There is a lack of published research concerning the possible associations between air pollution components and acute visits to outpatient clinics. We investigated associations between various components of air pollution and acute visits to clinics of a health plan in a large urban area. Methods: We used a time series analysis to determine the associations between daily levels of suspended particulate matter and ambulatory care acute visit rates during the 25-month period 8/1/98 to 8/31/00 and for the four year period of 8/1/98 to 12/31/02. Acute visits of health plan members to clinics with a respiratory diagnosis of asthma, COPD, upper and lower respiratory infections (URI and LRI) and cardiovascular disease were identified through electronic patient visit data. Pollutant data included 24-hour measurements of PM2.5, coarse PM (2.5-10 um), PM10, PM2.5 components (acidity, sulfates, OC, water-soluble transition metals and elemental carbon), 10-100 nm PM area (ultra-fines), polar VOCs (OHC); 8 hour maximum ozone; and 1 hour maximum NO2, CO and SO2. Visit counts for each diagnosis group were modeled by air quality metrics using general linear modeling, controlling for temporal trends and meteorologic variables. Moving averages of the a priori 0 to 2 day lagged air quality variables were investigated, as well as the 3 to 5 day average. Results: For the 25-month data set, we found significant positive associations for the 0 to 2 day lag for child asthma with OHC, URI with ultrafine PM, and LRI with PM2.5 acidity and SO2. In comparison, we found 14 significant positive associations for the 3 to 5 day lag: adult asthma with ultrafine PM; child asthma with coarse PM, PM10, EC and OC; URI with coarse PM; LRI with coarse PM, PM10, EC, OC and PM2.5; and cardiovascular disease with NO2, CO and O3. There were also a few significant negative associations. The magnitudes of the significant risk ratios were less than 1.15. In addition to these findings, preliminary results of the analysis of a four-year time-period of air quality data will be presented. Discussion: LRI and child asthma had the greatest number of significant associations with air pollution, mainly for the 3 to 5 day lag structure, in the 25-month data set. This study provides a unique evaluation of air quality and health effects by investigating the relationships of air pollution to uncommonly reported but readily measurable health effects.