Impact of PM2.5 on daily outpatient numbers for respiratory diseases in Shenzhen, China

Abstract

Objective: To assess the association between the concentration of the air pollutant PM2.5 and daily outpatient visits for respiratory disease. Methods: All records of daily outpatient visits to three hospitals in Shenzhen from January 1 to December 31, 2013 were collected. Daily air pollution monitoring and meteorology data from the same period were also collected in Shenzhen. The data were analyzed using a semiparametric generalized additive model with Poisson distribution of time series analysis controlling for long-term and seasonal trends, flu, DOW, public holidays, and meteorological factors. The excess risk(ER)of respiratory disease and its 95% CI value were calculated, along with the incremental increase of 10 μg/m3 in PM2.5 concentration. Results: Number of outpatient visits for respiratory diseases totaled 1 428 672(daily range: 1 790-5 228). The annual average PM2.5 concentration was 40.2 μg/m3(daily range: 7.2-137.1 μg/m3). The lag1 factor had the most significant impact on the lag effect. We estimated that a 10 μ g/m3 increase in day-before PM2.5 concentration was associated with a 1.809%(95% CI: 1.709%-1.909%)ER of visits for respiratory disease. After controlling for other pollutants(NO2, CO, and O3), the effect remained stable. When NO2, CO, and O3 were introduced separately, for every 10 μg/m3 rise in PM2.5 concentration, the excess risk of daily outpatient visits for respiratory disease was 1.814%(95% CI: 1.706%-1.923%), 2.780%(95% CI: 2.668%-2.892%), and 1.513%(95% CI: 1.403%-1.624%), respectively. With simultaneous control of NO2 and O3, NO2 and CO, and CO and O3, for every 10 μg/m3 rise in PM2.5 concentration, the excess risk of respiratory disease was 1.369%(95% CI: 1.242%-1.497%), 2.709%(95% CI: 2.590%-2.828%), and 2.577%(95% CI: 2.452%-2.702%), respectively. With simultaneous control of NO2, CO, and O3, for every 10 μg/m3 rise in PM2.5 concentration, the excess risk of respiratory disease was 2.370%(95% CI: 2.231%-2.509%). Conclusions: PM2.5 can increase the risk of outpatient visits for respiratory disease in Shenzhen.