Background: The relationship between air quality and risk of SARS-CoV-2 infection is poorly understood. We explored this association in a UK population-based cohort (COVIDENCE UK).

Methods: We investigated associations between long-term (2015-2019) nitrogen dioxide (NO₂) and fine particulate matter [PM with an aerodynamic diameter of ?2.5 µm (PM_2.5)] exposures with SARS-CoV-2 infection and level of antibody response among those infected. We used serological data from 10,489 participants, and assigned them air pollution exposure by their home postcode using a land use regression (LUR) model.

Results: After controlling for sociodemographic, occupational, and lifestyle covariates, we found a positive non-linear association between air pollution exposure and the risk of sero-positivity: the odds ratio (OR) of the top NO₂ quintile (25.9-87.8 ?g/m³) was 1.27 (95% CI, 1.05-1.53), compared to the bottom quintile (1.8-12.0 ?g/m³). For PM_2.5, the OR was 1.30 (95% CI, 1.07-1.57) comparing the top (10.3-15.7 ?g/m³) versus the bottom quintile (3.10-8.58 ?g/m³). In addition, we found that NO₂ was positively associated with higher antibody titres among seropositive participants (geometric mean ratio comparing the top versus bottom quintile, 1.08; 95% CI, 1.01-1.16; p-for-trend, 0.01), but there was no evidence of an association for PM_2.5.

Conclusion: Our findings show that the prior burden of air pollution exposure is associated with an increased risk of SARS-CoV-2 infection. This evidence strengthens the case for reducing long-term air pollution exposures, not only to reduce the risk of non-communicable diseases, but also to reduce the vulnerability of individuals to respiratory viruses.