Air pollution and temperature are associated with increased COVID-19 incidence: A time series study

OBJECTIVES: Although COVID-19 is known to be caused by human-to-human transmission, it remains largely unclear whether ambient air pollutants and meteorological parameters could promote its transmission. METHODS: A retrospective study was conducted to study whether air quality index (AQI), four ambient air pollutants (PM(2.5), PM(10), NO(2) and CO) and five meteorological variables (daily temperature, highest temperature, lowest temperature, temperature difference and sunshine duration) could increase COVID-19 incidence in Wuhan and XiaoGan between Jan 26th to Feb 29th in 2020. RESULTS: First, a significant correlation was found between COVID-19 incidence and AQI in both Wuhan (R(2) = 0.13, p < 0.05) and XiaoGan (R(2) = 0.223, p < 0.01). Specifically, among four pollutants, COVID-19 incidence was prominently correlated with PM(2.5) and NO(2) in both cities. In Wuhan, the tightest correlation was observed between NO(2) and COVID-19 incidence (R(2) = 0.329, p < 0.01). In XiaoGan, in addition to the PM(2.5) (R(2) = 0.117, p < 0.01) and NO(2) (R(2) = 0.015, p < 0.05), a notable correlation was also observed between the PM(10) and COVID-19 incidence (R(2) = 0.105, p < 0.05). Moreover, temperature is the only meteorological parameter that constantly correlated well with COVID-19 incidence in both Wuhan and XiaoGan, but in an inverse correlation (p < 0.05). CONCLUSIONS: AQI, PM(2.5), NO(2), and temperature are four variables that could promote the sustained transmission of COVID-19.