Potentially Damaging Surface Ozone Levels Rose in COVID Lockdown

Street Lights Empty Road

Less traffic in first lockdown reduced air pollution but caused potentially damaging surface ozone levels to rise.

Less traffic on the roads during the first lockdown led to a reduction in air pollution but may have caused potentially damaging surface ozone levels to rise, a new study has revealed.

The study — led by the University of York — shows levels of nitrogen dioxide (NO2) down on average across the UK by 42 percent, but surface ozone (O3) increased by 11 percent on average.

Surface, or ground-level ozone, can trigger a variety of health problems, particularly for children, the elderly, and people of all ages who have lung diseases such as asthma.

Scientists believe our warm and sunny spring weather may have been a contributing factor.

The report concludes that if the Covid-19 lockdown is taken as an example of how air quality will respond to future reductions in vehicle emissions — with more electric vehicles being introduced — it serves as a warning that the problem of O3 must also be considered.

Professor James Lee from the Department of Chemistry and the National Centre for Atmospheric Science said during the first lockdown levels of O3 were the worst in the South of England.

Professor Lee added: “The problem is being created by the change in chemistry between NOx (nitrogen oxide) and O3. The main reason is the change in the nitrogen dioxide levels but the warm sunny weather in April and May also increased the ozone level. As a result we found UV radiation across the UK was higher in 2020 compared to previous years, with the largest increases in southern England.

“London, Chilton in Oxfordshire and Camborne in Cambridgeshire saw increases of around 50% compared to previous years, with Glasgow and Inverness showing smaller increases of around 30%.

“These results are a cautionary tale. As well as looking at how we reduce levels of nitrogen dioxide by cutting diesel and petrol emissions, we also need to keep an eye on what is happening with ozone so we don’t create other forms of pollution dangerous to human health.”

The report says in China nitrogen oxide reductions have also led to increases in O3 and air quality abatement strategies are being developed in order to offset the problem. This can be achieved by controlling volatile organic compounds (VOCs) — which are gases emitted into the air from products or processes of industry and other man-made activity.

Professor Lee added: “Our research shows it will be vital to control man-made VOCs to avoid any health gains made by the reduction of NO2 being offset by O3 increases.”

Reference: “UK surface NO2 levels dropped by 42?% during the COVID-19 lockdown: impact on surface O3” by James D. Lee, Will S. Drysdale, Doug P. Finch, Shona E. Wilde and Paul I. Palmer, 18 December 2020, Atmospheric Chemistry and Physics.
DOI: 10.5194/acp-20-15743-2020

Data was collected from 175 Automatic Urban and Rural Network (AURN) traffic monitoring sites across the UK between 23rd March and 31st May 2020 and compared with figures from the previous five years.

3 Comments on "Potentially Damaging Surface Ozone Levels Rose in COVID Lockdown"

  1. quote:
    Less traffic on the roads during the first lockdown led to a reduction in air pollution but may have caused potentially damaging surface ozone levels to rise, a new study has revealed.

    Professor Lee added: “The problem is being created by the change in chemistry between NOx (nitrogen oxide) and O3. The main reason is the change in the nitrogen dioxide levels but the warm sunny weather in April and May also increased the ozone level. As a result we found UV radiation across the UK was higher in 2020 compared to previous years, with the largest increases in southern England.

    It would be nice if this article explained at least a little bit as to WHY O3 levels rose. Where they that high before industrialization? What does NO2 have to do with it – how does lowering NO2 raise O3, as one paragraph seems to begin to imply? And I thought that the UV radiation was blocked by the ozone layer, high in the atmosphere, not trace amounts (of I assume O3 that he is talking about) near the ground.

    poorly written article explains nothing to me.

    • con-fu-zed
      I agree with your assessment. Ground-level ozone can be problematic with respect to human health. People living in Los Angeles have known this for decades, where ozone levels have been so high that tires degrade prematurely. However, whether ozone is in the stratosphere or lower-troposphere, it has the same radiation absorption features, particularly for UV-C. Therefore, I’m surprised by the claim of increased UV being measured. Something doesn’t seem right here!

      The above summary article states, “As a result we found UV radiation across the UK was higher in 2020 compared to previous years, …” That initially left me with the impression that the authors were claiming that the decrease in NO2 was responsible for increased UV,

      A quick read of the linked article, and global search for “UV” within, finds the following speculation: “Therefore we conclude that in the cities in the southern UK some of the O3 increase is attributable not solely to reduced NOx but also to an increase in photochemistry related to the hot, sunny weather experienced in 2020.” That is, they are observing annual variations in UV-A associated with cloudless skies, and perhaps reduced particulates.

  2. … Without people, we still have a lot of lights, no need for it, after all…
    … I bet that is not a light powered by wind or solar power, either…

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