Objective To assess the effect of fine particulate matter (PM2.5) concentration on respiratory tract infections in children.
Methods We collected daily average concentration of PM2.5 in Jiaozuo City and the daily outpatient visit volume to the general pediatrics department of The Second Affiliated Hospital of Henan Polytechnic University from November 2015 to April 2016. The correlation between the two time-series data after denoising were identified by wavelet coherence analysis based on MATLAB.
Results The days with average concentrations of PM2.5 below the national air quality standard category I (35 μg/m3) accounted for 17% of the studied period in Jiaozuo City, and the days with concentrations more than 1 fold higher than the national standard accounted for 62%. The correlation coefficient between the respiratory tract infections in children and the daily average concentration of PM2.5 was close to 1 at 5% confidence level in the time domain. The first peak of PM2.5 daily average concentration appeared on the 60th day (maximum concentration), the first peak of outpatient visits for upper respiratory tract infections appeared on the 63rd day, and the first peak of outpatient visits for lower respiratory tract infections appeared on the 64th day. The second peak of PM2.5 daily average concentration appeared on the 131st day (which was far lower than the first peak), the second peak of outpatient visits for upper respiratory tract infections appeared on the 151st day, and the second peak of outpatient visits for lower respiratory tract in fections appeared on the 156th day.
Conclusion Serious PM2.5 pollution is identified in Jiaozuo in winter heating period. PM2.5 has an obvious effect on children's respiratory tract infections. The threshold value of PM2.5 significantly affecting upper respiratory tract of children is higher than that on lower respiratory tract. The higher PM2.5 concentration is, the sooner upper and lower respiratory infections in children occur, and the occurrence of upper respiratory tract infection is faster than that of lower respiratory tract infection.
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