An analysis of the effect of lockdown on air pollution-related health in two London boroughs

People around the world have spent parts of 2020 in lockdown. The Covid-19 pandemic has caused thousands of tragic deaths and damaged many peoples health directly and indirectly, but new research has shed light on a much-needed positive health development in these difficult times. The decreases in air pollution seen during lockdown, helped thousands of people to breathe easier, and could support action that may prevent thousands more from developing ill-health in future years.

Air pollution has a damaging effect on people’s health and is the top environmental risk to human health in the UK.1 Links with diseases such as heart disease, stroke, lung cancer and childhood asthma are well established and evidence is accumulating that a wide range of other conditions, including chronic obstructive pulmonary disease (COPD), type 2 diabetes (T2D), low birth weight and dementia are also linked to air pollution.2 Between them, these conditions are responsible for a huge burden to healthcare systems; although there are other risk factors for developing these conditions, (for example obesity, poor diet and genetic factors) in the UK alone, air pollution is specifically linked to around 40,000 deaths every year.1 Because of this, many organisations, including the World Health Organisation (WHO), and the European Union have set global targets to reduce air pollution. The UK’s central government and local councils and have been implementing policies for decades to improve air quality to an acceptable standard, but despite improvements over recent years, air pollution in many urban areas of the UK, still remains unacceptably high.3 For example, in London, despite improvements over the previous decade brought about by implementing low and ultra-low emission zones, and other policies designed to improve air quality, levels of toxic nitrogen dioxide (NO2), predominantly released from vehicle exhausts, still regularly breach the European Union and WHO recommended limits.3

Until the spring of 2020, that is.

As people across the country stayed at home, the amount of traffic on the nation’s roads plummeted. At its lowest point, the number of vehicles on the roads reduced by 70% of normal levels.4 Across the country, researchers measured an average 30% drop in the concentration of NO2.5 In London, road traffic reduced by 66% and average NO2 levels fell rapidly and substantially below the recommended limit.6 In one fell swoop, the nation’s exposure to these emissions fell dramatically5 proving that previously elusive targets could be reached!  

These findings begged the question, what health benefits could be seen in future years if these reductions in emissions could be maintained over the longer-term?

To answer this question, HealthLumen were commissioned* to predict the number of people in two boroughs of London, who may develop illnesses as a result of air pollution, in future years.7 To do this they created a ‘virtual’ population that represented the populations of these boroughs, including their age, sex and the incidence of the diseases of interest, and used this information to simulate the future burden of disease. Results showed that residents of Lambeth and Southwark, can expect to develop over 3700 illnesses between 2020 and 2024, assuming levels of NO2 stay the same as before lockdown. The study then simulated how many fewer people would become ill if pollution levels could have been maintained at lockdown levels throughout the rest of 2020. NO2 levels fell by 34% in Lambeth and 18% in Southwark during the national lockdown. Lowering air pollution by this amount through the rest of 2020 was predicted to avoid 1,106 new diseases by 2024, in these two boroughs alone. This included 155 cases of childhood asthma, 261 cases of COPD and 349 cases of dementia. The study went on to calculate the total healthcare saving in Lambeth and Southwark of avoiding these illnesses. The cost savings to the NHS, totalled over £4.5 million by 2024.

You can explore these data using the interactive graph below.

Successive additions of annual cases of a disease. For example, the cumulative incidence between 2020 and 2024 would be the sum of all new disease cases in each of those years.


These results are a call to action. Clearly, a national lockdown is not a long-term solution to address the high levels of air pollution that the UK experiences in its major urban centres. But as the nation emerges from the COVID-19 pandemic and successive lockdowns come to an end, the country might embrace a “new normal”. Many employees have worked successfully from home and many people have realised the benefits of walking or cycling as a valid means of transport. The impact and longevity of these shifts in transportation patterns, and the impact of other pollution reducing interventions remain to be seen, but if they persist, and translate into a sustained reduction in air pollution, then we may see future benefits in the improved health of the capital and the UK as a whole.


1. Department for Environment, Food and Rural Affairs (DEFRA). Clean Air Strategy 2019. Published 2019. Accessed 15 Feb 2021.

2. Royal College Paediatrics and Child Health (RCPCH). Every breath we take: report of a working party. Published February 2016. Accessed 15 February 2021.

3. Font A, Guiseppin L, Blangiardo M, Ghersi V, Fuller GW. A tale of two cities: is air pollution improving in Paris and London? Environ Pollut. 2019 Jun;249:1-12. doi: 10.1016/j.envpol.2019.01.040. Epub 2019 Jan 14. PMID: 30875529.

4. Slides to accompany coronavirus press conference: 30 March 2020. Prime Minister’s Office. Published 30 March 2020. Accessed 15 February 2021.

5. Air Quality Expert Group. Estimation of changes in air pollution emissions, concentrations and exposure during the COVID-19 outbreak in the UK. Published 30 March 2020. Accessed 15 Feb 2021.

6. Collivignarelli MC, De Rose C, Abbà A, Baldi M, Bertanza G, Pedrazzani R, Sorlini S, Carnevale Miino M. Analysis of lockdown for CoViD-19 impact on NO2 in London, Milan and Paris: What lesson can be learnt? Process Saf Environ Prot. 2021 Feb;146:952-960.

7. Retat L, Graff H, Xu M, Coker T, Webber L. 2020. Modelling the epidemiological and economic impacts of COVID-19 ‘lockdown’ on air pollution in the London local authorities of Lambeth and Southwark. Session 4 at the International Microsimulation Association congress 2020.

* This research was part of a project commissioned by Impact on Urban Health:

Impact on Urban Health commissioned this work to inform their Health Effects of Air Pollution programme approach and to test key assumptions of how the programme could create impact, specifically, to understand the attributable cost and morbidity of air pollution levels on Lambeth and Southwark, to inform the understanding of a safe level of air pollution, and additionally, to understand what cost being above those levels may have on the community over the next 5 years.

As well as the COVID-19 lockdown scenario described in the article above, the study also investigated some other scenarios. These included:

  • Meeting the WHO targets for PM2.5 , by 2024
  • Lowering air pollution levels to those measured in the London borough with the lowest levels of NO2 and PM2.5 (Havering).

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Editorial support provided by Jenny Smith

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