Impact of livestock-related air pollution on public health: A nationwide population-based study on COVID-19 in the Netherlands.

Ambient air pollution has been associated with increased COVID-19 incidence and severity worldwide. In the Netherlands, evidence suggests that air pollution from livestock farming in particular could contribute significantly to these effects. This study examines whether residential exposure to endotoxin emissions from livestock farming contributes significantly to increased risk of COVID-19 incidence and severity. We estimated annual-average livestock-related endotoxin exposure (EU/m3) for all Dutch residential addresses using advanced Gaussian dispersion modelling on detailed farm emission data in 2020. Individual-level exposure estimates were linked to national census and health registry data. In cohort analyses (8.3 million persons), interval-censored survival models were used to estimate hazard ratios (HR) for SARS-CoV-2 infection and COVID-19 hospitalization risks. In a test-negative case-control analysis (1.7 million tests), we estimated odds ratios (OR) by comparing test-positive to test-negative individuals with respiratory symptoms using mixed-effects logistic regression. Analyses were adjusted for individual- and area-level covariates, including local SARS-CoV-2 circulation. Residential exposure to endotoxins was associated with increased SARS-CoV-2 infection risk; HR was 1.131 (1.076-1.188) and OR was 1.163 (1.015-1.332) per unit increase of endotoxin in PM10 fraction. Associations remained, though attenuated, after co-pollutant adjustment for overall PM10, PM2.5 and NO2. For COVID-19 hospitalization risk, associations with endotoxin (HR = 1.327, 95% CI: 1.154-1.527) diminished after adjustment for particulate matter from livestock (livestock-PM, HR = 1.052, 95% CI: 0.799-1.385). Livestock-related air pollution contributes significantly to COVID-19 risk, with livestock-PM showing stronger statistical associations, and microbial components like endotoxins providing additional independent effects. Given the large rural populations worldwide, the health impact of livestock emissions warrants greater attention. Future research should further characterize the chemical, microbial, and physical properties of livestock-PM and its associated health effects.