Impact of Covid-19 transport restrictions on ambient air pollutant concentrations and asthma-related hospital admissions

Objectives: Exposure to air pollution is a known risk factor for asthma exacerbations and hospitalisations. This study aimed to identify if COVID-19 transport restrictions led to improvements in air quality in Dublin and if this had an impact on asthma-related hospital admissions. Study Design: This was a population-based retrospective cohort study. Methods: Daily concentration levels of particulate matter (PM2.5 and PM10) and nitrogen dioxide (NO2) were obtained from the Environmental Protection Agency (EPA). The Hospital In-Patient Enquiry (HIPE) system provided the daily number of asthma-related hospital admissions in Dublin. The figures for 2018-2019 were compared with the period of transport restrictions (from March 2020). Results: During the period of transport restrictions there was a significant decrease in mean daily concentrations in both PM2.5 (8.9 v 7.8μg/m3 p=0.002) and NO2 (24.0 v 16.7μg/m3 p<0.001). There was also a significant reduction in the mean number of daily asthma admissions (4.5 v 2.8 admissions p<0.001). Only NO2 showed a statistically significant correlation with asthma admissions (r=0.132 p