Particulate matter (PM2.5 and PM10) exposure: health effects and how to reduce it

Particulate matter, or PM, is a generic term for a complex mixture of solid and liquid particles of varying size, shape and composition. Public Health England explains that some particles are emitted directly (primary PM) while others form in the atmosphere through chemical reactions (secondary PM), and that composition varies with location, sources and weather.

Particles are usually described by size. PM10 are coarse particles under 10 microns in diameter, PM2.5 are fine particles under 2.5 microns, and PM0.1 are ultrafine particles under 0.1 microns. The same source says there is some experimental evidence that ultrafine particles may even pass through the lungs into the bloodstream.

This is not a diagnosis but an exposure. People are not diagnosed with particulate matter in the way they are with a disease, and the effects are seen across populations and over time. Individual risk depends on dose, duration, age, existing health and lifestyle, as the All Our Health guide notes.

Public Health England says the main sources of man-made PM are the burning of fuels by vehicles, industry and homes, as well as physical processes such as tyre and brake wear. Natural sources include wind-blown soil and dust, sea spray and fires involving vegetation. The All Our Health guide lists transport, industrial processes, farming, energy generation and domestic heating as sources of outdoor air pollution, with concentrations generally higher close to the source and particularly high in urban areas.

Indoor air matters as well, because the average person spends around 80% of their time indoors. The same guide names particulates from domestic appliances such as boilers, heaters, fires, stoves and ovens that burn carbon-containing fuels, and tobacco smoke including second-hand smoke, as indoor sources.

Ammonia from agriculture also plays a part. Public Health England explains that ammonia reacts with other gases to form secondary PM2.5, and that agricultural emissions have been a key contributor to some short-term episodes of high particle pollution in recent years.

The All Our Health guide says air pollution can affect the eyes, nose and throat, the heart and blood vessels, and the lungs. Short-term exposure over hours or days can lead to effects on lung function, coughing, wheezing and shortness of breath, exacerbation of asthma and increases in respiratory and cardiovascular hospital admissions. Over years it can reduce life expectancy through cardiovascular disease, respiratory disease and lung cancer.

Public Health England adds that there is an extensive body of evidence that long-term exposure to PM increases deaths and illness from cardiovascular and respiratory diseases, and that outdoor air pollution, particularly PM, has been classified by the International Agency for Research on Cancer as carcinogenic to humans and as causing lung cancer. More recent research has associated air pollution with dementia and cognitive decline and with diabetes, though the guide describes some of this as emerging evidence.

Effects begin early. Pregnancy and early childhood are critical times for development, and the Health Matters report says air pollution exposure is associated with low birth weight and premature birth, and that the normal growth of lung function in children is suppressed by long-term exposure.

There is no single illness called particulate exposure, and no test that measures your personal exposure in routine care. The All Our Health guide lists sore eyes, throat or a cough as signs that you may be reacting to a high pollution episode, and recommends limiting strenuous activity at those times, particularly if you are affected. People with asthma or other lung conditions may notice more cough, wheeze or breathlessness on high pollution days.

If you have breathing problems that are getting worse, ask your GP or asthma nurse to review your asthma or other lung condition. The guide advises people with asthma to use their reliever as necessary during high pollution episodes. If breathing difficulty is severe or your reliever is not helping, call 999 or go to A&E.

The All Our Health guide suggests the following for people during high pollution episodes: limit or avoid strenuous activity in highly polluted areas, particularly if you have symptoms; use asthma relievers as necessary; and reduce exposure to polluted outdoor air by closing external doors and windows that face a busy street during congested periods. It also points people to Defra's UK air service for current and forecast levels and health advice, and to text alert services in some areas aimed at people with conditions that could be made worse.

Individual choices matter too. The same guide says walking and cycling improve your own health as well as air quality, and lists indoor measures such as avoiding second-hand smoke and being careful with burning fuels at home. Smoking is itself a major source of particles for the smoker and those nearby. Because some of the biggest sources are outside personal control, much of the benefit comes from local and national policy, which is why public health bodies stress action by councils, planners and government as well as individuals.

The sources used here do not set out evidence that face masks or home air purifiers give a proven health benefit for the general public, so no recommendation is made on them.

• Check the forecast on the UK air quality service before planned vigorous exercise if you have asthma, COPD or heart disease.

• If you have asthma, keep your reliever inhaler to hand and use it as needed on high pollution days.

• Avoid smoking indoors and avoid second-hand smoke, which the All Our Health guide lists as an indoor source of exposure.

• Where possible choose quieter, less congested routes for walking, cycling or the school run.

• Remember that fires, stoves and boilers that burn fuel are indoor sources of particles, and that burning fuel can also produce carbon monoxide.

Air pollution can affect anyone, but the Health Matters report lists older people, children, individuals with existing cardiovascular or respiratory disease, pregnant women, communities close to busy roads and low-income communities as more susceptible. It explains that people on low incomes are more likely to have existing medical conditions and to live in areas with poorer outdoor and indoor environments, such as near industry or busy roads, so the disadvantages add up.

Modelling by the UK Health Forum and Imperial College London, funded by Public Health England, estimated that a 1 microgram per cubic metre reduction in fine particulate pollution in England could prevent around 50,900 cases of coronary heart disease, 16,500 strokes, 9,300 cases of asthma and 4,200 lung cancers over 18 years. These are population estimates rather than predictions for any one person.

Particulate pollution is not treated as a condition in its own right on the NHS. Care is directed at the diseases it can cause or worsen, such as asthma, COPD, heart disease and lung cancer, through the GP, practice nurse and specialist services. Asthma + Lung UK has a section on air pollution for people with lung conditions, covering how pollutants affect the lungs, when and where air quality is likely to be worse and how to lower your risk.

Private respiratory or cardiology review is available for the conditions that pollution can worsen. Be cautious about paid tests or products that claim to measure or remove your personal particulate burden, as the sources reviewed do not endorse them.