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Pollution

Worried about how higher pollution levels affect your asthma? Find out more about managing this common asthma trigger....

Air pollution plays a part in causing asthma in children and adults, as well as being a trigger that can make people's asthma symptoms worse. Two thirds of people with asthma have told us that traffic fumes make it worse and one third say a reduction in air pollution would make the most difference to their lives.

Why does pollution increase your risk of asthma symptoms or an asthma attack?

High levels of pollution affect everyone because when you breathe in air you breathe in the harmful substances too. People with asthma are more sensitive to pollution and experience the effects more quickly and severely. Children with asthma are particularly vulnerable to these effects because they play outdoors, have faster breathing rates, and their lungs are still developing. It's possible that people who are highly sensitive to pollution may find their asthma symptoms get worse even on low air pollution days.

Research has shown that high levels of air pollution can:

  • make people with asthma more sensitive to triggers (such as house dust mites, pollen, pets, moulds and fungus).
  • eventually cause your lungs to work less well (reduced lung function) because the linings in the airways become inflamed, which could lead to breathing problems.

When's the trigger most likely to affect you?


The two main air pollutants are 'ozone' and 'particulates'.

Ozone gas levels are often higher in sunnier climates and on hot summer days, especially in the afternoons and early evenings. It's produced when sunlight combines and reacts with chemicals produced by car, bus and lorry engines (particularly diesel vehicles), factories, chemical power plants and smoke from the burning of coal and oil.

Particulates are particles from dust, soot, ash, diesel fumes, wood smoke and sulphate aerosols in the air. This type of pollution happens all year round, even in winter - but levels can be especially high on a still day with not much breeze because the pollution can build up.

Smog - You can't see most air pollution, but on hot days when air pollution levels are high and there isn't much wind, a combination of particulates and ground level ozone can build up and create smog - a yellowish or blackish fog that's visible.

Smoke in the air from any type of fire can be a trigger for asthma and make asthma symptoms worse. In summer this could be from barbecues, and in autumn and winter you may notice more symptoms from bonfires or chimney smoke.

How do you know if air pollution is your trigger?

  • Noticing whether your's or your child's asthma symptoms get worse on days when the pollution forecast is high can help you work out if it's a trigger. DEFRA produces a UK-wide pollution forecast every day, and for the next 5 days, so you can check to see if your local area is likely to be affected in advance.
  • If you're physically active, you might find that your asthma symptoms get worse when air pollution levels are high.
  • If you notice your asthma symptoms getting worse up to a day after you have been outside in polluted air, or that you're more sensitive than usual to your other asthma triggers, this could also be a sign that air pollution is an asthma trigger for you.

What's the best way to reduce the risk of air pollution affecting you?

It's difficult to avoid air pollution, but there are a number of ways you can reduce the risk of it affecting you.

  • Have regular asthma reviews, and ask for advice from your GP or asthma nurse about what you or your child need to do when pollution levels are high, if you notice this has been affecting you. This can be included as part of your or your child's written asthma action plan.
  • Make sure you have your reliever inhaler with you at all times and take your preventer medication exactly as prescribed, even if you're feeling well. Your preventer inhaler can help build up resilience to triggers such as air pollution.
  • Be prepared - Use the DEFRA pollution forecast to see whether you need to be alert to make some changes to your plans.

When pollution levels are high:

  • carry your reliever inhaler with you
  • limit the amount of time you spend outside
  • when you're indoors, keep windows and doors closed
  • plan any outdoor activities including exercise for earlier in the day when air quality tends to be better
  • if possible, avoid areas where there's a lot of traffic, particularly in the afternoon, when air pollution levels are at their highest

Avoid smoky situations, or stand well back from the smoke where possible:

  • If you're having a barbecue or you're out on bonfire night
  • If you are being exposed to environmental smoke regularly (if your neighbour keeps lighting bonfires, for example), contact your local authority for advice.

Last reviewed March 2015