Cigarette smoking and ozone-associated emergency department use for asthma by adults in New York City

The association between ambient ozone (O-3) and hospital use for asthma in children and adults is well documented. The question remains of whether there are susceptible subpopulations of asthmatic individuals who are particularly vulnerable to high O-3 levels. Because tobacco use was prevalent in our cohort of inner-city adult asthmatic individuals (n = 1,216) in New York City (NYC), we investigated whether cigarette smoking was an effect modifier for asthma morbidity. We examined the relationship between personal tobacco use and O-3-associated emergency department (ED) use for asthma in public hospitals in NYC. Three subpopulations were defined: never smokers (0 pack-yr), heavy smokers (greater than or equal to 13 pack-yr) and light smokers (<13 pack-yr). Time-series regression analysis of ED use for asthma and daily O-3 levels was done while controlling for temperature, seasonal/long-term trends, and day-of-week effects. Heavy smokers displayed an increased relative risk (RR) of ED visits for asthma in response to increases in 2-d lagged O-3 levels (RR per 50 ppb O-3 = 1.72; 95% confidence interval: 1.13 to 2.62). Logistic regression analysis confirmed that heavy cigarette use was a predictor of ED use for asthma following days with high O-3 levels. Although adverse health effects of ambient O-3 have also been documented in asthma populations not using cigarettes (e.g., children), our results suggest that in adult asthmatic individuals, heavy personal tobacco use may be an effect modifier for (O)(3)-associated morbidity.