Effects of meteorological factors and air pollution on the number of allergic rhinitis outpatient visits in Changchun city, China.

The effects of environmental and climatic factors on the prevalence of allergic rhinitis (AR) in Changchun, China, have not been reported. This study aimed to investigate the relationship between meteorological factors, air pollution, and the number of AR outpatient visits in Changchun, and determine whether different temperature and humidity conditions would influence the effect of air pollution on the number of AR outpatient visits. Generalized additive and distributional lag non-linear models were used to assess the relationship between meteorological factors, air pollution, and the number of AR outpatient visits. Using different temperatures and relative humidities, we determined whether the effects of air pollution on the number of AR outpatients would change under different meteorological conditions. In total, 15,338 AR outpatient records were collected during the study period. Except for O3, other pollutants were positively correlated with AR outpatient visits overall. Results found that each 10 µg/m3 increase in PM2.5, PM10 and NO2, and per 1 µg/m3 increase in the daily average concentration of SO2, the number of AR outpatient visits increased by 1.45% (95% CI: 0.23%-2.70%), 1.03% (95% CI: 0.06%-2.00%), 3.98% (95% CI: 1.25%-6.78%), and 1.68% (95% CI: 0.78%-2.59%), respectively. Air pollution has immediate and cumulative lagged effects on these visits. There was a non-linear correlation between meteorological factors and the number of AR outpatient visits. Low and high temperatures, low RH and low barometric pressure may affect the number of AR outpatient visits. Compared with the minimum risk of each respective meteorological factor, their Relative Risk (RR) values are 1.65(95%CI: 0.80-3.40), 1.05(95%CI: 1.03-1.08), 1.53(95%CI: 1.21-1.93), and 1.75(95%CI: 1.25-2.43), respectively. The impact of low temperature is more pronounced. The hazardous effect of extreme meteorological factors was stronger in the < 15 years age group. In addition, The effect of air pollution on the number of AR outpatient visits increased at low temperature (< 33.3% percentile) and low relative humidity (< 33.3% percentile). Increased air pollution and changes in meteorological factors are associated with an increased risk of AR outpatient visits. Children < 15 years old are the most vulnerable to extreme weather factors. Low temperature and low RH could positively modify the effects of air pollution on AR outpatient visits.