Elevated ambient air zinc increases pediatric asthma morbidity

BACKGROUND: Recent studies indicate that the composition of fine particulate matter [PM <= 2.5 mu m in aerodynamic diameter (PM2.5)] is associated with increased hospitalizations for cardiovascular and respiratory diseases. The metal composition of PM2.5 influences allergic and/or inflammatory reactions, and ambient zinc contributes to worsening pulmonary function in susceptible adults. However, information is limited concerning associations between ambient air zinc levels and health care utilization for asthma, especially among children. OBJECTIVE: We aimed to investigate the relationship between outdoor ambient air PM2.5 zinc levels and urgent health care utilization for children living in an urban area. METHODS: We used a time-series study to estimate the association of ambient air PM2.5 zinc levels with hospital admissions and emergency department (ED) utilization by children in Baltimore, Maryland, controlling for time trends. We used data from daily discharge administrative claims of ED and hospital utilization for asthma in children, 0-17 years of age for Greater Baltimore from June 2002 through November 2002. We collected ambient air PM2.5 Metal concentration data, determined by X-ray fluorescence spectroscopy, during the U.S. Environmental Protection Agency-sponsored Baltimore Supersite project. RESULTS: Previous-day medium levels of zinc (8.63-20.76 ng/m(3)) are associated with risks of pediatric asthma exacerbations that are 1.23 (95% confidence interval, 1.07-1.41) times higher than those with previous-day low levels of zinc (< 8.63 ng/m(3)) after accounting for time-varying potential confounders. CONCLUSION: Results suggest that high ambient air PM2.5 zinc levels are associated with an increase in ED visits/hospital admissions for asthma on the following day among children living in an urban area.