Effects of fine particulate matter and its components on emergency room visits for pediatric pneumonia: A time-stratified case-crossover study

Pneumonia, one of the important causes of death in children, may be induced or aggra-vated by particulate matter (PM). Limited research has examined the association between PM and its constituents and pediatric pneumonia-related emergency department (ED) visits. Measurements of PM2.5, PM10, and four PM2.5 constituents, including elemental carbon (EC), organic carbon (OC), nitrate, and sulfate, were extracted from 2007 to 2010 from one core station and two satellite stations in Kaohsiung City, Taiwan. Furthermore, the medical records of patients under 17 years old who had visited the ED in a medical center and had a diagnosis of pneumonia were collected. We used a time-stratified, case-crossover study design to estimate the effect of PM. The single-pollutant model demonstrated interquartile range increase in PM2.5, PM10, nitrate, OC, and EC on lag 3, which increased the risk of pediatric pneumonia by 18.2% (95% confidence interval (Cl), 8.8‒28.4%), 13.1% (95% CI, 5.1‒21.7%), 29.7% (95% CI, 16.4‒44.5%), 16.8% (95% CI, 4.6‒30.4%), and 14.4% (95% Cl, 6.5‒ 22.9%), respectively. After PM2.5, PM10, and OC were adjusted for, nitrate and EC remained signifi-cant in two-pollutant models. Subgroup analyses revealed that nitrate had a greater effect on children during the warm season (April to September, interaction p = 0.035). In conclusion, pediatric pneumonia ED visit was related to PM2.5 and its constituents. Moreover, PM2.5 constituents, nitrate and EC, were more closely associated with ED visits for pediatric pneumonia, and children seemed to be more susceptible to nitrate during the warm season.