Air Pollution and Asthma

The Financial Times reported this morning (23/12/2017) that the Government is going to launch a consultation on tighter restrictions on wood burning stoves. Particulates (e.g. PM2.5) as well as NOX emissions are seen as one of the reasons to reduce diesel vehicle usage but according to the FT, forty percent of particulate emissions in the UK come from burning wood and coal in homes – more than double that from diesel cars. Sadiq Khan in London is particularly concerned about the growth in the numbers of wood-burning stoves. For some reason they don’t seem to be covered by the Clean Air Acts that stopped the burning of coal in most UK cities.

Comment: it would certainly seem wise to tackle this problem. One of my local pubs recently installed such a fire in their restaurant. It may feel good to have a roaring wood fire near you over dinner, but it’s not good for air pollution or public health.

Meanwhile Private Eye published this report following the revelation that a number of top racing cyclists are taking medication: “The NHS is urging parents to look for signs of asthma in their children, which could include heavy wheezing, shortness of breath and winning the Tour de France. Another tell-tale sign your child could be asthmatic is that they’ve just signed to ride with Team Sky”.

It seems “exercised induced asthma” (EIA) is now a well-known condition so you need to add that to the list of causes of asthma that I gave in a previous blog post (see: https://abdlondon.wordpress.com/2017/11/18/does-air-pollution-in-london-cause-asthma/ ).

Roger Lawson

Twitter: https://twitter.com/Drivers_London

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Does Air Pollution Cause Asthma?

One response to the ABD’s campaign against the Mayor’s Transport Strategy is that we should not oppose it because it might stop their kids getting asthma. Children have been widely used in Sadiq Khan’s publicity over his plans to reduce air pollution and there is a strong emphasis in the Transport Strategy on the potential environmental benefits. But unfortunately, a lot of the arguments put forward are simplistic and show little understanding of the causes and prevalence of asthma.

Like the Mayor, this writer has suffered from asthma, so I have a personal interest in this issue. Note also that the ABD does not oppose cleaning up London’s air because one does not need a scientist to tell you that air quality in central London, and in some outer London “hot spots”, is appalling bad and not just makes walking or cycling unpleasant but probably exacerbates some medical conditions (including pre-existing asthma of course). The ABD’s opposition to the Mayor’s Transport Strategy is based on other factors and the irrational, ineffective and uneconomic approach to the environmental issues.

Let’s cover some of the basics about asthma:

  • Does air pollution cause asthma (in children or others)? As far back as 1995, a Committee on the Medical Effects of Air Pollutants (COMEAP) looked at this issue and came to the conclusion that although air pollution may provoke asthma attacks or aggravate existing chronic disease, the effect is generally small with other factors such as viruses, cigarette smoke, diet and house dust-mite droppings more important. They also noted that there had been a general increase in asthma in the last 30 years so it was now a very common disease. Was this down to more urbanisation and are city dwellers more likely to suffer from it because of air pollution? The answer is no. Indeed, a study in the Isle of Skye, where air pollution was believed to be minimal, showed as high a prevalence of asthma as anywhere else. See this report in The Independent for more information: http://www.independent.co.uk/news/air-pollution-is-not-the-cause-of-asthma-epidemic-1578437.html . Very heavy air pollution may reduce lung function in children according to more recent studies, but it is not the cause of the asthma epidemic in the last 50 years.
  • Why are allergies, that drive asthma, more common? There have been many possible causes put forward for this. It seems to relate to the exposure of very young children, or their mothers, that condition the immune system to over-react. For example, it has been argued that excessively clean houses are one cause. Smoking by mothers, or in houses, may have been another cause. Or a general increase in pollutants in the home. As we reported in the ABD London newsletter in June 2017, the concentration of some air pollutants can be five times higher indoors than outdoors. This is due to gas stoves, food cooking, dog/cat hairs, dead skin, lint particles from tumble dryers, deodorant spays, scented candles and air fresheners. The desire to minimise heat loss from homes, and reduce drafts (and hence fresh air) along with smaller homes might have contributed to these problems. Obesity is also a factor in asthma risk and we all know that has been rising. 
  • Are diesel vehicles a cause of worse air pollution and asthma? Diesel vehicles became popular for cars, and always have been for HGVs and buses, because of reduced fuel consumption and a desire to minimise carbon emissions. However that did not take account of the large emissions of NOX and particulates from such vehicles. But removing all diesel vehicles would not likely have much impact on overall air pollution levels in London. The reason is that much of the air pollution is from other sources such as home/office heating, industrial activities, or simply blown in from the countryside around. Even with vehicles, much of the particulates come from tyre and brake wear so converting all vehicles to electric ones will only reduce the emissions, not eliminate them. And removing private cars will have minimal impact when taxis, PHVs, LGVs, and HGVs continue to increase in number and are much bigger sources, as are trains, planes, river traffic and other transport modes. To reduce air pollution needs a much more “holistic” approach rather than focussing on one or two perceived evils alone. It seems very unlikely that attacks on diesel vehicles will have much impact on the causes or prevalence of asthma in any sensible timescale and the latest diesel vehicles are now very clean.

The above is a simplification of a very complex topic, but I hope it explains some of the key points. Does Mayor Sadiq Khan believe he is doing good by his aggressive environmental policies that will get us all walking and cycling (other than the disabled presumably)? Is he simply ignorant of the real issues? Or is he promoting these policies for other reasons, such as the financial problems of Transport for London, his desire to raise more funds and his desire to be seen as “doing good” to help his re-election?

Lastly, it’s worth mentioning that although asthma has become a lot more prevalent, the medical treatments for the disease are now quite effective in other than the worse cases. Certainly, much better than when I was a child. The high prevalence of asthma in the UK has been given as one reason why the UK became a centre for the medical research into treatments. But it seems to be a worldwide phenomenon that asthma levels have increased.

My conclusion is that cleaning up London’s air might make it a more pleasant place to live and work, but it won’t have much impact on the prevalence of asthma.

Incidentally a great article on the scare-mongering associated with air pollution is present here: https://notalotofpeopleknowthat.wordpress.com/2017/08/15/claims-of-40000-deaths-from-air-pollution-debunked-by-death-statistics/

Roger Lawson

Twitter: https://twitter.com/Drivers_London

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