Short-term exposure to ambient air pollution and hospital visits for IgE-mediated allergy: A time-stratified case-crossover study in southern China from 2012 to 2019

Background: Because of the limited epidemiological evidence on the association between acute air pollutants and allergy, there is a need to investigate this association, especially between the short-term exposure to air pollution and the serum Immunoglobulin E (IgE)-mediated allergy. Methods: A total of 39,569 IgE test results and demographic characteristics were obtained in the First Affiliated Hospital of Guangzhou Medical University between August 2012 and September 2019. Ninety-nine specific allergens were tested according to clinical diagnosis. The logistic regression was used to assess the effects of CO, NO2 and PM2.5 exposure on the risk of sensitization to specific inhalant/food allergens. Generalized additive models with multivariate adjustments were utilized to model the exposure-response relationship. Stratified analyses were performed to estimate the reliability of correlations in various subgroups. Findings: Single-pollutant models indicate that the 3-day moving average (lag(2) (4)) of CO, PM2.5 or NO2 is associated with the increased risk for allergic diseases related to specific inhaled allergens. In multi-pollutant models, the adjusted Odds Ratio (OR) 95% (Confidence Interval, CI) increases by 8% (95% CI, 2%-15%) for per increment of 0.2 mg/m(3) in CO levels, and rises by 8% (95% CI, 2%-13%) for each increase of 16.3 mu g/m(3) in PM2.5 concentration. The associations are stronger in youngsters (<18, years) but not significantly different by gender. Particularly, a significantly stronger association between PM2.5 exposure and hospital visits for inhaled allergy is observed in patients who are exposed to lower concentration of SO2 (<10.333 mu g/m(3)) and higher levels of NO2 (>= 42.0 mu g/m(3)), as well as patients enrolled after 2017. Interpretation: The short-term exposure to CO/PM2.5 increases the number of hospital visits for IgE-mediated allergy, especially for the sensitization to specific inhalant allergens. Therefore, to prevent inhaled allergies, the public policy for controlling air pollution needs to be considered seriously. (C) 2021 The Author(s). Published by Elsevier Ltd.