Relationship between visits to emergency departments for asthma and ozone exposure in greater Seattle, Washington.

BACKGROUND

Air pollution is known to affect asthma symptoms in controlled and epidemiologic studies.

OBJECTIVE

To determine whether ozone exposure in Seattle is associated with increased use of hospital emergency departments.

METHODS

Hospital data on daily asthma cases for all ages were obtained for 1998 through 2002. Ozone and fine particulate matter (< or = 2.5 microm in diameter) (PM2.5) data were obtained from local air agencies. Poisson regression models were used to assess the association between asthma visits to emergency departments and air pollutants. Maximum daily 1- and 8-hour average ozone concentrations and the daily PM2.5 concentration were used.

RESULTS

We observed associations between both ozone metrics and emergency department visits in children. For the maximum daily 1- and 8-hour average ozone concentrations, the relative risks (RRs) were 1.08 (95% confidence interval [CI], 1.00-1.18) and 1.11 (95% CI, 1.02-1.21), respectively, at 3 days' lag. Weaker but significant associations were also observed for adults. For the maximum daily 1-hour average ozone concentration, the RR was 1.06 (95% CI, 1.01-1.11) at 4 days' lag, and for the maximum daily 8-hour average ozone concentration, the RR was 1.06 (95% CI, 1.01-1.12) at 2 days' lag and 1.08 (95% CI, 1.02-1.14) at 4 days' lag.

CONCLUSION

Ozone exposure exacerbates asthma in people in the Seattle area, especially in children.