Outdoor air pollution and the lungs

The average adult breathes over 15 cubic metres of air every day. Although pollutants in the air are often invisible, they can have serious effects on our health, including the lungs, the heart and other organ systems, and the developing foetus. This factsheet aims to provide you with answers to the many questions you may have about outdoor air pollution and your lungs.

Last Update 24/01/2024
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What are the main air pollutants?

An air pollutant is “any substance in air that could, in high enough concentrations, harm humans, animals, vegetation or material”. There are many pollutants in the air and the different items that make up air pollution vary from one area to another. However, some pollutants are more closely monitored than others as they are known to cause damage to the environment or health. The main pollutants include ozone, nitrogen dioxide, particulate matter and sulphur dioxide. Read the next page for a table describing all of these pollutants.

What are the health effects of air pollution on your lungs?

The respiratory effects of air pollution depend on the type and mix of pollutants, the concentration in the air, the amount of time that you are exposed to the pollutant, how much of the pollutant you breathe in and how much of the pollutant penetrates your lungs. Lung health symptoms that can be seen straight after exposure to high pollution levels include irritation of the airways, dyspnoea (difficulty breathing) and an increased chance of having an asthma attack. Being exposed to air pollutants for a long period of time has been shown to increase the occurrence of lung diseases, including cancer, and deaths from these diseases. Read the next page for details on how each pollutant can affect your lungs.

Who is most at risk from air pollution exposure and how might it affect them?

Air pollution is especially harmful to people who already suffer from lung diseases such as asthma and chronic obstructive pulmonary disease (COPD). However, the elderly, children and developing babies are also at an increased risk of experiencing harmful effects from exposure to air pollution. If you have a chronic respiratory condition or are elderly, then you are most at risk of air pollution’s harmful effects such as premature death from lung or heart disease. If you have sensitive airways, exposure to air pollution can trigger asthma attacks and cause wheezing, coughing and respiratory irritation. Healthy people who work or exercise outdoors are also vulnerable to the adverse effects of air pollution, particularly during high concentrations of ground-level ozone.

What can I do to reduce pollution levels?

As well as industrial processes, one of the major sources of air pollution is cars and other vehicles. Therefore, as an individual there are many things you can do to reduce pollution levels.

  • Think seriously before using your car for a journey. Consider the benefits offered by other modes of transport, like cycling, walking or using public transport (for example: increased safety, particularly for children; reduced congestion; better health by ensuring you meet the World Health Organization (WHO) recommended 20 minutes of exercise every day; saved time, it can be much quicker to travel by other forms of transport than by car; saved money).
  • When doing the school run, shopping or going to work, think about car sharing, turn off your engine while stationary, maintain your car properly and reduce your speed.
  • Buy ‘green’ and ‘efficient’ (for example, when buying your next car look at the vehicle that uses the least fuel and is the least polluting).
  • Look at reducing your energy consumption at home or switching to clean renewable energy sources, don’t breathe in hazardous materials (read hazard labels) and stop burning solid fuels, particularly rubbish or treated woods.

How can I interpret air pollution levels?

Many countries and international agencies have developed systems to show the different levels of air pollution in different areas each day and this alerts the population when levels are excessive. One of these, from the UK Department of Health, is shown below. This system works by grading each concentration of pollutant, and ranking it at a level between 1 and 10. These levels are then split into four categories: low; moderate; high; and very high.

Who is controlling our air pollution levels?

Air quality standards are set by the European Union to protect our health. For more information, please go to They vary from country to country, depending on risks to health, how easy the levels are to achieve, cost and other considerations. The WHO regularly reviews the evidence on health effects of air pollutants, and then writes guidelines. These guidelines help support actions worldwide to get air quality to the best level to protect health. The table below shows the air quality levels that are recommended by the WHO and that all countries should aim for.

For particulate matter, average levels are recommended over 1 year and for 24 hours, because both short- and long-term effects occur. It is thought that no guideline will ever provide complete protection, but health effects can be reduced. For ozone, a level is given that should not be exceeded in 8 hours, as the effects of ozone can be seen very quickly. Ozone may have longterm effects, but there is not, at present, enough evidence to suggest a guideline. Evidence has shown that nitrogen dioxide has long-term health effects and that its levels match with other pollutants. Therefore, the long-term levels given for nitrogen dioxide will offer protection to the public. A 10-minute sulphur dioxide level has been proposed, as its effects on exercising asthmatics can be seen in this time. The 24-hour levels of sulphur dioxide have been proposed because studies have shown that lowering levels reduces health effects, although it is difficult to separate these effects from other pollutants.

How can you reduce your exposure to air pollution?

Exposure to air pollutants can be avoided in several ways according to the kind of air pollutant and the setting. Read the next page for details of how you should deal with each air pollutant. In general, you should, first of all, check the air pollution alert for the day. In winter, avoid walking along busy streets with lots of traffic fumes. In summer, air pollution levels are generally higher on hot, sunny days. So try to avoid energetic outdoor activities or do them in the morning when pollution levels are usually lower.

Other pollutants

Volatile organic compounds

Volatile organic compounds or VOCs are any compounds that are made from carbon and are involved in chemical reactions with the sun’s rays in the air. As it says in the name, these compounds are volatile (gaseous) and they can also be called organic gases. Outdoors, the main sources of VOCs are road traffic and industrial use of paint, varnish or glue. It has already been shown that VOCs irritate the nose and throat, cause allergic skin reactions and dyspnoea (difficulty breathing), and aggravate asthma.

Carbon monoxide

Carbon monoxide or CO is a colourless and odourless gas, which comes from incomplete combustion of carbon in fuel. Outdoors, carbon monoxide emissions are generated by road traffic, manufacturing industries and housing. Heating our houses produces the main part of this pollutant in towns and cities. CO reduces the amount of oxygen the blood can carry around the body, causing temporary or permanent damage to different parts of the body.

Further reading

The Health and Environment Alliance (HEAL):

This material was compiled by the ERS Environment and Health Commitee, and reviewed by the Health and Environment Alliance (HEAL).
Other sources include the WHO Air Quality Guidelines – Global Update 2005 ( phe/health_topics/outdoorair/outdoorair_aqg) and the UK National Air Quality Information Archive (
Co-funding, and production and content support for this publication has been provided by HEAL (, through DG Environment, European Commission. ELF was founded by ERS, with the aim of bringing together patients and the public with respiratory professionals to positively influence respiratory medicine.
ELF is dedicated to lung health throughout Europe, and draws together the leading European medical experts to provide patient information and raise public awareness about respiratory disease.
HEAL is an international non-governmental organisation which aims to improve health through public policy that promotes a cleaner and safer environment. HEAL represents a diverse network of more than 50 citizens’, women’s, patients’, health professionals’ and environmental organisations across Europe.