Symptoms in pediatric asthmatics and air pollution: Differences in effects by symptom severity, anti-inflammatory medication use and particulate averaging time

Experimental research in humans and animals points to the importance of adverse respiratory effects from short-term particle exposures and to the importance of proinflammatory effects of air pollutants, particularly O-3. However, particle averaging time has not been subjected to direct scientific evaluation, and there is a lack of epidemiological research examining both this issue and whether modification of air pollutant effects occurs with differences in asthma severity and anti-inflammatory medication use. The present study examined the relationship of adverse asthma symptoms (bothersome or interfered with daily activities or sleep) to O-3 and particles <10 pm (PM10) in a Southern California community in the air inversion zone (1200-2100 ft) with high O-3 and low PM (R = 0.3). A panel of 25 asthmatics 9-17 years of age were followed daily, August through October 1995 (n = 1,759 person-days excluding one subject without symptoms). Exposures included stationary outdoor hourly PM10 (highest 24-hr mean, 54 mu g/m(3), versus median of 1-hr maximums, 56 mu g/m(3)) and O-3 (mean of 1-hr maximums, 90 ppb, 5 days >120 ppb). Longitudinal regression analyses utilized the generalized estimating equations (GEE) model controlling for autocorrelation, day of week, outdoor fungi, and weather. Asthma symptoms were significantly associated with both outdoor O-3 and PM10 in single pollutant- and coregressions, with 1-hr and 8-hr maximum PM10 having larger effects than the 24-hr mean. Subgroup analyses showed effects of current day PM10 maximums were strongest in 10 more frequently symptomatic (MS) children: the odds ratios (ORs) for adverse symptoms from 90th percentile increases were 2.24 [95% confidence interval (CI), 1.46-3.46] for 1-hr PM10 (47 mu g/m(3)); 1.82 (CI, 1.18-2.81) for 8-hr PM10 (36 mu g/m(3)); and 1.50 (CI, 0.80-2.80) for 24-hr PM10 (25 mu g/m(3)). Subgroup analyses also showed the effect of current day O-3 was strongest in 14 less frequently symptomatic (LS) children: the ORs were 2.15 (CI, 1.04-4.44) for 1-hr O-3 (58 ppb) and 1.92 (CI, 0.97-3.80) for 8-hr O-3 (46 ppb). Effects of 24-hr PM10 were seen in both groups, particularly with 5-day moving averages (ORs were 1.95 for MS and 4.03 for LS; p<0.05). The largest effects were in 7 LS children not on anti-inflammatory medications [5-day, 8-hr PM10, 9.66 (CI, 2.80-33.21); current day, 1-hr O-3, 4.14 (CI, 1.71-11.85)]. Results suggest that examination of short-term particle excursions, medication use, and symptom severity in longitudinal studies of asthma yields sensitive measures of adverse respiratory effects of air pollution.