Evaluating changes in ambient ozone and respiratory-related healthcare utilization in the Washington, DC metropolitan area.

Ozone pollution is a known respiratory irritant, yet we do not fully understand the magnitude or timing of respiratory effects based on short-term exposure. We investigated the associations between ambient ozone concentrations and respiratory symptoms as measured by healthcare utilization events. We used comprehensive electronic health records to identify respiratory responses to changes in ambient ozone levels. We constructed a dataset from Kaiser Permanente Mid-Atlantic States (KPMAS) that included information on 2013 and 2014 daily utilization rates for a broad range of healthcare utilization - nurse calls/emails, provider visits, emergency department and urgent care visits (ED/UC) and hospital admissions - by census block. We used 8-h average ozone concentrations collected from 48 air monitoring stations in the region via the Air Data database of the USEPA. We estimated the association between changes in ambient ozone (exposure windows of current day, 1-day lag and 3-day moving average) and changes in healthcare utilization using linear regression controlling for census tract-level socioeconomic indicators and temperature. Increases in ozone were associated with increases in three of the four utilization event types. A 10 ppb increase in 1-day ozone was associated with a 2.95% (95% CI: 1.93%, 3.96%) increase in calls/emails, a 1.56% (95% CI: 0.38%, 2.74%) increase in ED/UC visits and a 1.10% (95% CI: 0.48%, 1.73%) increase in provider visits. We did not find associations between ozone and hospital admissions. Proportionally, highest effects were found for nurse calls/emails possibly indicating a high number of mild effects that may be underreported in studies that examine only ED visits or hospital admissions.