29th April 2019

Allergy and air quality:
what's the connection?

It’s UK Allergy Awareness week (29 April-3 May) and this year the campaign is focused on air quality and its impact on allergy.

Air quality concerns in London date back over seven centuries 

London, as a major city, has huge challenges managing its infrastructure and how it impacts on the environment and health of Londoners. While many may know about the London smogs of the 50s and 60s, caused by coal smoke, the history of air quality and health goes back much further.

In 1273, coal was prohibited from being used in London due to its potential health implications, followed by a Royal Decree in 1306 prohibiting its use in all workshops.

SO2 down. NO2 up. Ozone

Some air pollutants have been greatly reduced – the switch away from coal, together with cleaner petrol and diesel fuels has meant that sulphur dioxide (SO2) levels have plummeted in London.  However, nitrogen dioxide (NO2) levels (and those of other nitrogen oxides) remain high – possibly a direct result of increased road traffic, and diesel cars in particular - and they have a direct impact on allergy sufferers in a number of ways.

As summer approaches, NO2 can react with other  compounds in the presence of sunlight to form ozone at ground level – interestingly, this is even more common outside city centres where other pollutants prevent this process.

So what does this all mean for allergy sufferers?

Those of us with chronic lung issues, such as asthma, tend to feel  an immediate effect on high pollution days – while that may just be a slight wheeze, there’s a proven correlation between these days and an increased rate of heart attacks and acute lung issues.

There’s also a mortality figure attached to this: particulate matter has led to around 29,000 deaths a year, with exacerbation of asthma and COPD (chronic obstructive pulmonary disease) a major contributing factor to these figures.

The rapid increase in air pollution in developing countries is also indicated in the increase in overall allergy prevalence.

The impact of air pollution on allergy goes deeper

Birth cohort studies have reported a link between transport-related air pollution and an increase in asthma in children.

Air pollution can impact on epigenetic alteration of genes via the process of methylation. Several studies have looked at polymorphisms in genes that are involved in antioxidant stress and inflammation and further studies have been mooted or initiated to look at candidate genes to reverse the deleterious oxidizing effect of air pollution.

What can we do now?

Simple things will help to reduce pollution levels

  • - More travel by public transport, car sharing, cycling, and walking more
  • - Eating more local produce to reduce food miles
  • - Supporting local and national environmental projects
  • - Social media engagement on these important issues 

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