Pre-admission ambient air pollution and blood soot particles predict hospitalisation outcomes in COVID-19 patients

Abstract

BackgroundAir pollutant exposure is one of the major risk factors for aggravation of respiratory diseases. We investigated whether exposure to air pollution and accumulated black carbon particles in blood were associated with COVID-19 disease severity, including the risk for intensive care and duration of hospitalisation.MethodsFrom May 2020 until March 2021, 328 hospitalised COVID-19 patients (29% at intensive care) were recruited from 2 hospitals in Belgium. Daily exposure levels (from 2016 to 2019) for particulate matter (PM2.5and PM10), nitrogen dioxide (NO2) and black carbon were modelled using a high-resolution spatiotemporal model. Blood black carbon particles (internal exposure to nano-sized particles) were quantified using pulsed laser illumination. Primary clinical parameters and outcomes included duration of hospitalisation, and risk of intensive care.ResultsIndependent of potential confounders, an interquartile range (IQR) increase in exposure in the week before admission was associated with increased duration of hospitalisation (PM2.5:+4.22 (95%CI:0.74-7.69) days;,NO2:+4.33 (1.30-7.37) days); Similar effects were observed for long-term NO2and BC exposure on hospitalisation duration. These effect-sizes for an IQR increase in air pollution on hospitalisation duration were equivalent to the effect of a 10-year increase in age on duration of hospitalisation. Furthermore, for an IQR higher blood black carbon load, the odds ratios for intensive care hospitalisation was 1.36 (1.11-1.70).ConclusionsIn hospitalised COVID-19 patients, higher pre-admission ambient air pollution and blood black carbon levels predicted adverse outcomes. Our findings imply that air pollution exposure influences on COVID-19 severity and therefor the burden on medical care systems during the COVID-19 pandemic.