ULEZ Asthma Impact

The following is an article written by Michael Simons on the likely impact of the ULEZ expansion on the incidence of asthma. It is a very good summary of the causes of asthma and the negligible impact that the ULEZ will have on it.

What Impact Would ULEZ Expansion Have on Asthma and COPD Cases?

The Mayor of London does not justify his plan to extend the Ultra Low Emission Zone to outer London by referring to the official Integrated Impact Assessment1 projections – the Impact Assessment forecasts only very small health benefits – instead, the Mayor relies on rhetoric and anecdotal stories, mainly centred around asthma, and childhood asthma in particular.

So what is known about asthma in London in the context of air pollution, and particularly pollution by nitrogen dioxide, NO2, the main target of ULEZ?

Asthma Mortality:

The Office of National Statistics, responding to a freedom of information request, gave the following numbers for total child asthma deaths in London2:

  YearAged under 1  1 to 4  5 to 9  10-14  15-19Total 0-19
2013 0 0 2 204
2014011204
2015002114
2016010012
2017002226
20180125311
2019001203
2020001001

There are multiple known causes and triggers for asthma, so most of this tiny number of cases may not have resulted from air pollution anyway. For instance, hot weather is a recognised aggravating factor, and 2018 had a particularly hot summer, which might account for the higher number that year. While every child’s death is an individual tragedy, in the administrative context of a population of over 9 million, these numbers are vanishingly small, and so would be any marginal improvement from ULEZ expansion.

Asthma Hospital Admissions:

A 2022 report from the Imperial College Environmental Research Group3 presents estimates of the number of hospital admissions for asthma. It states that:

“ Exacerbation of asthma by air pollution is estimated to lead to around 700 asthma admissions from  2017 – 2019 in children in London, 7% of all asthma admissions in children in London. (Asthma admissions may have more than one cause e.g. air pollution may worsen response to an allergen.)”

This was over 3 years, so the average annual number was 233. Note that, as stated, this number accounts for just 7% of child asthma admissions. Note also that the headline announcement by City Hall of 3600 child asthma admissions in 2021/22 referred to all-cause admissions, not pollution-exacerbated admissions. (Asthma has many causes and triggers, including indoor pollution, mould, dust mite, household chemicals, outdoor pollution, pollen, cold weather, hot weather, and hereditary factors – see the Appendix). This is an important distinction to bear in mind.

The Imperial College report also gives an estimate of the percentage change in admissions per 10 µg m-3 change of pollutant concentration. For nitrogen dioxide, NO2, and children aged 0-14, this value is 3.9% per 10 µg m-3 (p11 of the report).

The likely reduction in NO2 levels from expansion of ULEZ into outer London is not clear. The Integrated Impact Assessment gives a reduction of 6.9% in emissions, and a 1.4% reduction in NO2 level when population-weighted. For simplicity and transparency in the arithmetic, we will illustrate the reduction in admissions expected from a 10% decrease in NO2 levels in outer London, well above those estimates.

Roadside levels4 (within 5 metres of a busy main road) of NO2 in October 2022 were 28 µg m-3, and background levels (away from busy traffic) levels were 19 µg m-3. Most residents in outer London live well away from busy main roads, so we will adopt an effective value of 22 µg m-3.

A 10% notional ULEZ reduction is a reduction of 2.2 µg m-3. Since a 10 µg m-3 reduction in NO2 level is estimated to reduce child asthma emissions by 3.9%, the ULEZ reduction in NO2 level will bring about a proportionate reduction in admissions of 2.2/10×3.9 = 0.86%.

0.86% of 233 gives a reduction of just TWO hospital admissions per year across the whole of London.

And note we are talking about hospital admissions, not deaths.

Asthma/COPD Admissions for over-64’s

The numbers associated with the 15 – 64 year age group in the report are lower all round and give a much smaller result, so we will not report further on these.

For the over 65 age group asthma was combined with COPD (chronic obstructive pulmonary disease) because it is difficult to clinically distinguish between the two conditions. In this case, the report estimates 900 admissions over the 3 years, or 300 cases per year. For COPD/asthma in the over-64’s the percentage change in admissions per 10 µg m-3 change of pollutant concentration was estimated at 1.42%. The same NO2 levels apply as before.

Applying the same process as above, the % reduction in admissions will be 2.2/10×1.42 = 0.31%. 0.31% of 300 = 0.94, or rounding up, ONE less admission per year across the whole of London.

Comparison with the Integrated Impact Assessment

The Jacobs Integrated Impact Assessment1 considered the decrease in health burden expected from expanding the ULEZ zone. It did not give estimates for asthma hospital admissions, only “incidences” (undefined). However it did give estimates for Respiratory Hospital Admissions, a term which includes asthma, and in Table 6-2, p73, it estimates that the extended ULEZ scheme would reduce annual London- wide hospital admissions from 2122 to 2086, a decrease of 26 cases or 1.2%.

A decrease of 26 cases across a city of over 9 million people is still a very small number. There are 33 boroughs in Greater London, so that averages out at less than one hospital admission fewer per borough per year. Again, a negligible benefit.

Conclusions

There appears to be no credible evidence that the expansion of the ULEZ into outer London would produce anything more than insignificant health benefits in asthma – or other respiratory diseases for that matter. We identify in this report three separate and credible sources which point to the negligible benefits which might be expected.

Vague statements and political histrionics about suffering children are a misleading way to inform public policy in this area. Proper analysis is required, especially when the policy carries heavy costs for society, as ULEZ certainly does. And these analyses point to ULEZ expansion doing effectively nothing for asthma.

Appendix

The NHS information sheet on asthma states:

The exact cause of asthma is unknown.

People with asthma have swollen (inflamed) and “sensitive” airways that become narrow and clogged with sticky mucus in response to certain triggers.

Genetics, pollution and modern hygiene standards have been suggested as causes, but there’s not currently enough evidence to know if any of these do cause asthma.

Who’s at risk

A number of things can increase your chances of getting asthma. These include:

  • having an allergy-related condition, such as eczema, a food allergy or hay fever – these are known as atopic conditions
  • having a family history of asthma or atopic conditions
  • having had bronchiolitis – a common childhood lung infection
  • exposure to tobacco smoke as a child
  • your mother smoking during pregnancy
  • being born prematurely (before 37 weeks) or with a low birth weight Some people may also be at risk of developing asthma through their job.
  • Asthma triggers

Asthma symptoms often occur in response to a trigger. Common triggers include:

  • infections like colds and flu
  • allergies – such as to pollen, dust mites, animal fur or feathers
  • smoke, fumes and pollution
  • medicines such as anti-inflammatory painkillers like ibuprofen and aspirin
  • emotions including stress, or laughter
  • weather – such as sudden changes in temperature, cold air, wind, thunderstorms, heat and humidity
  • Mould or damp
  • Exercise

References

  1. downloadable at https://haveyoursay.tfl.gov.uk/1561 9/widgets/44946/documents/27025
  2. https://www.ons.gov.uk/aboutus/transparencyandgovernance/freedomofinformationfoi/childhoo  dasthmainlondon2006to2020
  3. https://www.imperial.ac.uk/school-public-health/environmental-research-group/research/air-  pollution-epidemiology/air-pollution-and-asthma-in-london-2016-2019/
  4. https://www.london.gov.uk/programmes-strategies/environment-and-climate-  change/environment-and-climate-change-publications/inner-london-ultra-low-emission-zone-  expansion-one-year-report
  5. https://www.nhs.uk/conditions/asthma/causes/

Michael Simons, March 2023     (Dr Michael Simons PhD, MRSC)

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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://freedomfordrivers.blog/2017/11/18/does-air-pollution-in-london-cause-asthma/ ).

Roger Lawson

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Does Air Pollution Cause Asthma?

One response to our 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 we do 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). Our 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 our 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

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