Air pollution exposure, SARS-CoV-2 infection, and immune response in a cohort of 3,700 healthcare workers

ABSTRACT

Introduction: The role of air pollution on SARS-CoV-2 infection is still unclear. We aimed to verify this association in a cohort of healthcare workers (HCWs), a group identified as at high risk since the beginning of the pandemic. Material and Methods: We included HCWs who performed a nasopharyngeal swab (NS) for detection of SARS-CoV-2 at the Policlinico Hospital (Milan, Italy) in February-December 2020. Daily average concentrations of particulate matter ≤2.5 μm (PM2.5) and nitrogen dioxide (NO2) were assigned to each worker’s residential address and treated as time-dependent variables. We generated person-days at risk and applied multivariable Poisson regression models adjusted for age, sex, BMI, smoke, job title and province to evaluate incidence rate ratios (IRR) and 95% confidence interval (CI) of positive NS. The association between air pollution and anti-nucleocapside antibodies was assessed among swab-positive workers through multivariable linear regression models. The study was approved by the hospital Ethics Committee (828_2021bis). Results: 635 (17%) positive swabs were recorded among 3,712 included HCWs. A 10 μg/m3 increase in PM2.5 and NO2 average concentrations in the five days preceding NS was associated with a higher risk of testing positive [IRR 1.11 (CI 1.02;1.21) and 1.10 (1.03;1.18), respectively]. Among swab-positive HCWs, we observed a 49% decrease in antibody titer (CI -60;-36) associated with a 10 μg/m3 increase in PM2.5 mean levels in the month preceding NS. Conclusions: Our study suggests a potential role of air pollution exposure in influencing the immune response to SARS-CoV-2 infection.