Every summer it’s becoming more and more important to follow news from #pollutionwatch, the Guardian’s column especially dedicated to air pollution and smog related news. This comes from that time on 26 July 1943 when, at the height of the second world war, people in Los Angeles thought they were under chemical gas attack as they experienced stinging eyes and rasping throats in what is now recognised as the first summer smogs (we talked about it here). Once synonymous with Los Angeles, this is now known to be a serious problem in much cooler climates, including the UK. These smogs come from chemical reactions between a cocktail of pollutants over several days, driven by sunlight. One of the main pollutants is ozone.

Ozone and summer smogs

In the upper atmosphere ozone shields us from harmful ultraviolet light, but when breathed it is very harmful. Moreover, it is very chemically reactive. Early measurement methods in Los Angeles included placing stretched rubber tubes outside every hour and waiting until cracks appeared. Sometimes it took as little as six minutes.

Data from the UK government shows that less traffic during the 2020 lockdowns made the problem worse in our urban areas. Although traffic contributes to these smogs, very fresh vehicle exhaust also consumes ozone. The 80% of us that live in urban areas experienced the worse ozone since the hot summers of 2006 and 2003, when summer smog was estimated to have caused up to 769 of the 2,000 heatwave deaths.

Health impact analysis in London suggests that these smogs result in hundreds of hospital admissions each year, especially for asthma. Ozone normally peaks in the afternoon, so simply shifting outdoor exercise to the mornings could reduce the impacts. This is especially important for school sports and endurance events. Los Angeles set up a system of smog warnings in the 1950s but air pollution is rarely mentioned in UK weather forecasts.

Ozone damages our crops too, including estimated global losses of 4-15% in wheat yields – amounting to $4bn to $16bn each year. This is especially problematic in India, Pakistan and Bangladesh where summer smog is worsening rapidly, and some locally grown crops might be especially vulnerable.

It’s time to protect air quality indoors

The UK government is also under pressure to adopt World Health Organization guidelines for air pollution. This is a debate about the air outdoors. Step off the pavement into a train station, shop or football stadium and the limits do not apply. Should the same levels of protection apply to indoor public spaces?

Diesel trains mean nitrogen dioxide in King’s Cross and Paddington stations in London, and Waverley station in Edinburgh are about twice the annual limits for outdoor air. In Birmingham New Street it is about eight times more.

Particle pollution on London Underground depends on which line you take. Averaged over 22 journeys, researchers found PM2.5 particle concentrations that were about 30 times the annual WHO guidelines. A brief investigation in Glasgow’s subway showed similar figures but data is lacking for the systems in Liverpool and Tyne and Wear.

Measurements from high streets in Dublin show air pollution in shops depends a lot on the ventilation system, while a study from France shows merchandise can affect air in shops – the worst being a car equipment store, followed by clothing, shoes, and leather, and DIY stores.

In football stadiums smoke from cigarettes, flares and fireworks, along with the cooking of match-time food, can cause air pollution problems.

Where to look for a solution?

Pollution control starts at source. In the developed world the sources of summertime smog are changing. With better controls on industry, the products used in our homes such as solvents and the renewed growth in aerosol propellants are now having a greater impact. Globally, increases in methane, from fracking, agriculture and gas production, are adding to summer smog as well as our climate emergency. International action is needed to control these sources. This needs to be on the table when global leaders meet at the forthcoming G20 and Cop26.


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Read the full articles and more here:

  1. Gary Fuller, The Guardian, Pollutionwatch: how sources of summertime smog are changing, June 18, 2021 (https://www.theguardian.com/environment/2021/jun/18/pollutionwatch-how-sources-of-summertime-smog-are-changing)
  2. Gary Fuller, The Guardian, Pollutionwatch: is it time to protect air quality indoors?, July 2, 2021 (https://www.theguardian.com/environment/2021/jul/02/pollutionwatch-protect-air-quality-indoors-tube-rail)
  3. Gary Fuller, The Guardian, Pollutionwatch: Pollutionwatch: time to rethink London’s red routes, June 4, 2021 (https://www.theguardian.com/environment/2021/jun/04/pollutionwatch-time-to-rethink-londons-red-routes)
  4. Confédération Suisse, Federal Office for the Environment FOEN, Ozone – Summer smog (https://www.bafu.admin.ch/bafu/en/home/topics/air/info-specialists/air-quality-in-switzerland/ozone—summer-smog.html)