Air pollution exposure and daily clinical visits for allergic rhinitis in a subtropical city: Taipei, Taiwan.

This study was undertaken to determine whether there was an association between air pollutant level exposure and daily clinic visits for allergic rhinitis (AR) in Taipei, Taiwan. Daily clinic visits for AR and ambient air pollution data for Taipei were obtained for the period of 2006-2011. The relative risk for clinic visits for AR was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. In the single-pollutant models, on warm days (>23ºC) significant positive associations were found for increased rate of AR occurrence and ambient levels of particulate matter (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3). On cool days (<23ºC), all air pollutants were significantly associated with elevated number of AR visits except SO2. For the two-pollutant models, PM10, O3, and NO2 were significantly associated with higher rate of AR visits in combination with each of the other four pollutants on cool days. On warm days, CO levels remained significantly related with increased AR visits in all two-pollutant models. This study provides evidence that higher levels of ambient air contaminants enhance the risk of elevated frequency of clinic visits for AR.