Ozone Alerts and Asthma Exacerbations: A Case Study of Dallas-Fort Worth 2000-2008.

Abstract

The objective of this study was to evaluate the role of public information about air quality (ozone alerts) in modifying the effects of air pollution on asthma exacerbations, using a range of measures that encompass varying degrees morbidity. A time series dataset was constructed that related the daily number of medical care services utilized for asthma with ozone, fine particulates, ozone alert, and other control variables. The study included subjects enrolled in health plans offered by employers in Dallas-Fort Worth during the ozone seasons May 2000 – September 2008. Count models of asthma hospitalizations underestimated the harmful association with ozone by 40% when ozone alerts were not included as a control variable. A 20 ppb increase in 8-hr maximum ozone levels on the previous day was associated with a 11.6% increase in asthma hospitalizations (95% CI: 2.5%, 20.6%). The lowest ozone alert level (orange) on the previous day was associated with 14.1% fewer asthma hospitalizations (95% CI: -27.9%, -0.3%) and a red or higher ozone alert was associated with 19.9% fewer asthma hospitalizations (95% CI: -42.5%, 2.6%). Weaker relationships were found for asthma ER visits, possibly due to that fact that ER visits for asthma may be due to an inability to see a doctor in an outpatient setting (i.e. evenings and weekends) and thus these visits may less strongly related to environmental triggers. Most studies of the effects of air pollution do not account for behavioral responses to public health information about air quality, such as ozone alerts, and may underestimate the harmful effects of poor air quality.