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Lockdown air quality boost helped 41% reduction in adult asthma hospital stays

Reductions in Nitrogen Dioxide and Particular Matter combined with fine weather during 2020 led to cleaner air conditions compared to previous five year average

Man uses asthma inhaler

Oxford residents with asthma had fewer hospital stays during 2020 compared to the previous five-year average largely due to reductions in air pollution, new research has found.

The study, published in BMJ Open, investigated the link between acute asthma hospital admissions and specific air pollutant levels in Oxford in the UK during 2020, which saw two national COVID-19 lockdowns between March-June and November-December.

In 2020, levels of air pollution fell significantly, with different pollutants dropping by between 18-33%.

  • Nitrogen Dioxide – reduction of 26.7% from 14.6 μg m-3 (2015-2019 average) to 10.7 μg m-3 in 2020
  • Particulate Matter 2.5 – reduction of 33.5% from 10.1 μg m-3 (2015-19) to 6.7 μg m-3 (2020)
  • Particular Matter 10 - reduction of 18.6% from 13.2 μg m-3 (2015-19) to 10.8 μg m-3 (2020)

The OxAria study team, led by the University of Birmingham working with Professor Felix Leach at the University of Oxford, Oxfordshire County and City Councils and Oxfordshire Clinical Commissioning Group*, found that the falling pollution levels strongly correlated with lower rates of acute asthma care provision for adult residents in the four postcodes in Oxford city, falling from 78 per 100k residents in 2015-19, to 46 per 100k residents, a reduction of 41%.

Professor Leach says, “Air Quality is a complex phenomenon with complex impacts. By collaborating with colleagues in academia, the NHS, industry, and local authorities, we have shown a real link between asthma and air pollution measured in Oxford thanks to the unfortunate opportunity offered by the lockdowns associated with the COVID-19 pandemic. The air quality work we do in Oxford focuses around spatially resolved detailed measurements and this offers a great piece of evidence towards helping improve everyone’s health going forwards”.

Dr Suzanne Bartington, Clinical Associate Professor of Environmental Health at the University of Birmingham and author of the study says, “The impact of lockdowns on reductions in traffic and industry led to a unique situation where air quality significantly improved for a temporary period during the COVID-19 pandemic. This study shows that for Oxford, levels of major air pollutants including nitrogen dioxide and particulate matter fell sharply on a background of ongoing improvements in recent years."

“The results of air pollution levels falling may have had an impact on the number of severe asthma cases that need acute hospital care, with 41% fewer hospital stays compared to the previous five-year average. Furthermore, we also identified a 4% increase in risk of asthma hospital admissions for every 1 μg m-3 increase in mean monthly NO2, and an approximately 3% increase in risk for every 1 μg m-3 increase in mean monthly PM2.5 levels."

“This is an important study to help us better understand how demand for NHS inpatient care may change when air quality is improved. Whereas previous studies on lockdown air pollution have focused on major cities in the UK such as London or Birmingham, Oxford is more typical of a smaller city or large town where many residents live.”


*now called the Buckinghamshire, Oxfordshire and Berkshire West Integrated Care System