Acute effects of ambient air pollution on clinic visits of college students for upper respiratory tract infection in Wuhan, China

Ambient air pollutants have been linked to adverse health outcomes, but evidence is still relatively rare in college students. Upper respiratory tract infection (URTI) is a common disease of respiratory system among college students. In this study, we assess the acute effect of air pollution on clinic visits of college students for URTI in Wuhan, China. Data on clinic visits due to URTI were collected from Wuhan University Hospital, meteorological factors (including daily temperature and relative humidity) provided by Wuhan Meteorological Bureau, and air pollutants by Wuhan Environmental Protection Bureau. In the present study, generalized additive model with a quasi-Poisson distribution link function was used to examine the association between ambient air pollutants (fine particulate matter (PM₂.₅), particulate matter (PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and ozone (O₃)) and the daily number of clinic visits of college students for URTI at Wuhan University Hospital in Wuhan, China. In the meantime, the model was adjusted for the confounding effects of long-term trends, seasonality, day of the week, public holidays, vacation, and meteorological factors. The best degrees of free in model were selected based on AIC (Akaike Information Criteria). The effect modification by gender was also examined. A total of 44,499 cases with principal diagnosis of URTI were included from January 1, 2016, to December 31, 2018. In single-pollutant models, the largest increment of URTI visits were found at lag 0 day in single-day lags, and the effect values in cumulative lags were greater than those in single-day lags. PM₂.₅ (0.74% (95%CI: 0.05, 1.44)) at lag 0 day, PM₁₀ (0.61% (95%CI: 0.12, 1.11)) and O₃ (1.01% (95%CI: 0.24, 1.79)) at lag 0–1 days, and SO₂ (9.18% (95%CI: 3.27, 15.42)) and NO₂ (3.40% (95% CI:1.64, 5.19)) at lag 0–3 days were observed to be strongly and significantly associated with clinic visits for URTI. PM₁₀ and NO₂ were almost still significantly associated with URTI after controlling for the other pollutants in our two-pollutant models, where the effect value of SO₂ after inclusion of O₃ appeared to be the largest and the effects of NO₂ were also obvious compared with the other pollutants. Subgroups analysis demonstrated that males were more vulnerable to PM₁₀ and O₃, while females seemed more vulnerable to exposure to SO₂ and NO₂. This study implied that short-term exposure to ambient air pollution was associated with increased risk of URTI among college students at Wuhan University Hospital in Wuhan, China. And gaseous pollutants had more negative health impact than solid pollutants. SO₂ and NO₂ were the major air pollutants affecting the daily number of clinic visits on URTI, to which females seemed more vulnerable than males.