Association between annual mean levels of air pollutants and COVID-19 incidence rate by cumulative infection waves in single-pollutant models
| Air pollutant | First wave | Second wave | Third wave | |||
| RR | 95% CI | RR | 95% CI | RR | 95% CI | |
| PM2.5 | 1.074 | 0.978 to 1.179 | 1.029 | 1.002 to 1.056 | 1.051 | 1.027 to 1.075 |
| PM10 | 1.064 | 0.985 to 1.149 | 1.023 | 1.001 to 1.045 | 1.040 | 1.020 to 1.060 |
| NO2 | 1.034 | 0.991 to 1.080 | 1.010 | 0.999 to 1.022 | 1.020 | 1.009 to 1.030 |
| NO | 1.094 | 0.980 to 1.221 | 1.022 | 0.991 to 1.053 | 1.040 | 1.013 to 1.068 |
| O3 | 0.974 | 0.935 to 1.016 | 0.990 | 0.978 to 1.001 | 0.980 | 0.970 to 0.990 |
Rate ratios (RR) per 1 µg/m3 increase in the annual average exposure to each pollutant estimated from Poisson regression model. Covariates in the model are: age, sex, living in a residential care home, positive history of stroke, treatment for diabetes, antihypertensive treatment and treatment for obstructive airway diseases.
First wave from COVID-19 outbreak to 11 June 2020; second wave from COVID-19 outbreak to 31 December 2020; third wave from COVID-19 outbreak to 13 March 2021 (end of observational period).