Air Pollutant Concentrations Linked to Decreased Hospital Admissions

Oxford air pollutant concentrations

New research finds that reductions in air pollutant concentrations during the Covid-19 pandemic led to a 42% reduction in asthma hospital admissions within Oxford.

The study analysed monthly hospital admissions for adults with a primary diagnosis of acute asthma, from the beginning of 2015 to the end of 2020. Hourly air pollutant concentrations of nitrogen dioxide (NO2) and particulate (PM2.5 and PM10) for the same period were obtained at the Automatic Urban and Rural Network (AURN) station at St Ebbe’s in the city. In addition, hourly meteorological data, including relative humidity (RH) and temperature (T) for the same period, were obtained from the Oxford Radcliffe Observatory.

Reduced Air Pollutant Concentrations

Air pollutant concentrations reduced significantly during 2020 compared to the 2015-2019 average:

  • NO2 reduced by 26.7% from 14.6µg/m3 to 10.7µg/m3;
  • PM5 reduced by 33.5% from 10.1µg/m3 to 6.7µg/m3; and,
  • PM10 reduced by 18.6% from 13.2µg/m3 to 6.7µg/m3.

Asthma admission rates reduced by 42% in 2020 when compared to the 2015-2019 average, from 78 per 100,000 to 46 per 100,000. The researchers found a strong correlation between air pollutant concentrations and asthma hospital admissions. The decrease, therefore, in 2020 asthma hospital admissions was likely the result of reduced transport and industrial emissions during the 2020 lockdowns.

Additionally, the researchers found asthma admissions increased significantly with higher concentrations of NO2 and PM2.5. A 1µg/m3 increase in mean monthly NO2 led to a 4% increase in asthma hospital admission risk, whilst a 1µg/m3 increase in PM2.5 led to a 3% increase.

Another hypothesis for the reduction in asthma admissions is that 2020 saw a reduction in all-cause emergency admissions in an effort to ‘protect the NHS’. However, the authors note that:

“acute asthma is a severe condition which requires urgent hospital management and therefore it is likely that most patients in this study accessed emergency care following an acute attack.”

The study provides important insights into the effects of changes in air quality and hospital asthma admissions. Hopefully it will help galvanise support and action to lower pollutant concentrations in Oxford and further afield, with the concomitant health benefits. For further analysis of the impact of the 2020 lockdowns on air quality, please see Redmore’s news story on the topic here.

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