Impact of Air Pollutants on Outpatient Visits for Acute Respiratory Outcomes

Abstract

The air pollution in China is a severe problem. The aim of our study was to investigate the impact of air pollutants on acute respiratory outcomes in outpatients. Outpatient data from 2 December 2013 to 1 December 2014 were collected, as well as air pollutant data including ozone (O₃), nitrogen dioxide (NO₂), carbon monoxide (CO), sulfur dioxide (SO₂), and particulate matter (PM_2.5 and PM₁₀). We screened six categories of acute respiratory outcomes and analyzed their associations with different air pollutant exposures, including upper respiratory tract infection (URTI), acute bronchitis (AB), community-acquired pneumonia (CAP), acute exacerbation of chronic obstructive pulmonary disease (AECOPD), acute exacerbation of asthma (AE-asthma), and acute exacerbation of bronchiectasis (AEBX). A case-crossover design with a bidirectional control sampling approach was used for statistical analysis. A total of 57,144 patients were enrolled for analysis. PM_2.5, PM₁₀, NO₂, SO₂, and CO exposures were positively associated with outpatient visits for URTI, AB, CAP, and AEBX. PM₁₀, SO₂, and CO exposures were positively associated with outpatient visits for AECOPD. Exposure to O₃ was positively associated with outpatient visits for AE-asthma, but negatively associated with outpatient visits for URTI, CAP, and AEBX. In conclusion, air pollutants had acute effects on outpatient visits for acute respiratory outcomes, with specific outcomes associated with specific pollutants.

Keywords: air pollutant; outpatient visit; respiratory outcome.

Figure 1

Variation of different air pollutants throughout the study year in panels A–F. (A) Variation of PM_2.5 in the study year; (B) Variation of PM₁₀ in the study year; (C) Variation of CO in the study year; (D) Variation of NO₂ in the study year; (E) Variation of SO₂ in the study year; (F) Variation of O₃ in the study year; (G) Variation of AQI in the study year. Maximal concentrations of air pollutants occurred during cold periods, except for O₃, which showed an inverse trend. Panel G shows the variation of the Chinese AQI, which is a composite measure of air pollutants.

Figure 1

Variation of different air pollutants throughout the study year in panels A–F. (A) Variation of PM_2.5 in the study year; (B) Variation of PM₁₀ in the study year; (C) Variation of CO in the study year; (D) Variation of NO₂ in the study year; (E) Variation of SO₂ in the study year; (F) Variation of O₃ in the study year; (G) Variation of AQI in the study year. Maximal concentrations of air pollutants occurred during cold periods, except for O₃, which showed an inverse trend. Panel G shows the variation of the Chinese AQI, which is a composite measure of air pollutants.

Figure 2

Association between CO and outpatient visits for different acute respiratory outcomes in panels A–E. (A) Association between CO and outpatient visits for URTI; (B) Association between CO and outpatient visits for AB; (C) Association between CO and outpatient visits for CAP; (D) Association between CO and outpatient visits for AECOPD; (E) Association between CO and outpatient visits for AEBX. Horizontal axis represents the days lagged from 0–5, and vertical axis represented the odds ratios. The highest odds ratios appeared in the association with AECOPD in lag 0 (odd ratio (OR) = 1.188, 95% confidence interval (CI) 1.056–1.335).