Associations between air pollution and outpatient visits for allergic rhinitis in Xinxiang, China

Several epidemiological studies have investigated the adverse health effects of air pollution, but studies reporting its effects on allergic rhinitis (AR) are limited, especially in developing countries having the most severe pollution. Limited studies have been conducted in China, but their results were inconsistent. So, we conducted a time-series study to evaluate the acute effect of six air pollutants (fine particulate matter [PM2.5], particulate matter with diameter less than 10 mu m [PM10], sulfur dioxide [SO2], nitrogen dioxide [NO2], ozone [O-3], and carbon monoxide [CO]) on hospital outpatient visits for AR in Xinxiang, China from January 1, 2015, to December 31, 2018. An over-dispersed Poisson generalized additive model adjusting for weather conditions, long-term trends, and day of the week was used. In total, 14,965 AR outpatient records were collected during the study period. Results found that each 10 mu g/m(3) increase in PM2.5, PM10, SO2, NO2, O-3, and CO corresponded to 0.70% (95% confidence interval 0.00-1.41%), 0.79% (0.35-1.23%), 3.43% (1.47-5.39%), 4.54% (3.01-6.08%), 0.97% (- 0.11-2.05%), and 0.07% (0.02-0.12%) increments in AR outpatients on the current day, respectively. In the stratification analyses, statistically stronger associations were observed with PM2.5, PM10, SO2, NO2, and CO for AR outpatients < 15 years of age than in those 15-65 and >= 65 years of age, whereas the opposite result was found with O-3. Associations between PM10, SO2, NO2, O-3, and AR outpatients were higher in the warm season than those in the cool season. This study suggests that exposure to PM2.5, PM10, SO2, NO2, and CO was associated with increased AR risk and children younger than 15 years might be more vulnerable.