Age-related association of fine particles and ozone with severe acute asthma in New York City

Background: Ambient fine particles (particular matter <2.5 microm diameter [PM(2.5)]) and ozone exacerbate respiratory conditions including asthma. There is little documentation determining whether children are more vulnerable to the effects of ambient pollution than adults, or whether pollution causes life-threatening episodes requiring intensive care unit (ICU) admission.

Objective: We investigate the relationship between severe asthma morbidity and PM(2.5) and ozone in the warm season, and determine whether there is an age-related susceptibility to pollution.

Methods: Daily time-series analysis of 6008 asthma ICU admissions and 69,375 general (non-ICU) asthma admissions in 4 age groups (<6, 6-18, 19-49, and 50+ years) in 74 New York City hospitals for the months April to August from 1999 to 2006. The regression model adjusted for temporal trends, weather, and day of the week. Risks were estimated for interquartile range increases in the a priori exposure time window of the average of 0-day and 1-day lagged pollutants.

Results: Age was a significant effect modifier for hospitalizations, and children age 6 to 18 years consistently had the highest risk. Among children age 6 to 18 years, there was a 26% (95% CI, 10% to 44%) increased rate of ICU admissions and a 19% increased rate of general hospitalizations (95% CI, 12% to 27%) for each 12-microg/m(3) increase in PM(2.5). For each 22-ppb increase in ozone, there was a 19% (95% CI, 1% to 40%) increased risk for ICU admissions and a 20% (95% CI, 11% to 29%) increased risk for general hospitalizations.

Conclusion: Warm weather patterns of ozone and PM(2.5) disproportionately affect children with asthma and appear responsible for severe attacks that could have been avoided.