A study on the short-term effect of particulate matter pollution on hospital visits for asthma in children in Shanghai, China.

Recently, particulate matter pollution has been worsening, which has been affecting the asthma visits in children. In this study, we assessed the short-term effects of PM and PM on asthma visits in children in Shanghai, China from January 1, 2009 and December 31, 2010, using a generalized additive model. We controlled the confounding factors, such as long-term trends, week day effect, and weather elements. The lag effects of different age subgroups (≤ 2 yr, 3-5 yr, and 6-18 yr subgroups) were performed. The results showed significant effects of PM and PM on asthma visits in children, though the seasonal lags varied for the three age subgroups. In general, the effect of PM on asthma visits in children was stronger and more acute than that of PM. PM showed the highest relative risk of 1.192 at lag 0 day in summer; and PM showed the highest relative risk of 1.073 at lag 3 day in autumn. Overall, particulate matter pollution showed a greater effect on relatively younger children. In particular, the ≤ 2 yr subgroup showed the highest seasonal relative risk of PM. Especially, seasonal relative risk of PM in autumn for the ≤ 2 yr subgroup was much higher than that for the other two subgroups. The 3-5 yr and 6-18 yr subgroups showed the highest seasonal relative risk of PM in summer and winter, respectively. But the pediatric visits data we obtained cannot reflect the true prevalence of asthma and multiple visits. Thus, selection bias may exist in our analysis.