What exactly are the air pollution impacts on health?

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The impacts and dangers associated with air pollution are becoming increasingly recognised. Around 28,000 to 40,000 deaths per year are estimated to be attributable to air pollution in the UK, and while there are defined exposure limits, it is unknown whether these are entirely safe for the whole population. To accompany Global Action Plan’s ‘Clean Air Day’, this post summarises research to date on the impacts that air pollution can have on our health.

An image showing a tree canopy from beneath
Image by Jom and used under Creative Commons CC BY 2.0

Air pollution harm

Outdoor air pollution is estimated to cause around 4.2 million premature deaths worldwide, mainly through illnesses such as heart disease, stroke, lung cancer, and respiratory infections or disease. As it causes death indirectly and reduces life expectancy, precise cases of fatality due to air pollution are difficult to pin-point. As mentioned above, the figure is 28,000 to 40,000 in the UK, and the latest data for Northern Ireland (NI), from 2010, suggests a number of 553 deaths. Air pollution has also been a subject of considerable concern in Wales.

Poor air quality is the largest environmental risk to public health in the UK. Long term exposure can cause cardiovascular and respiratory diseases, and lung cancer, reducing life years. Short term exposure to higher levels of air pollution can impact lung function, asthma, and affect cardiovascular and respiratory systems. Air pollution can impact at every stage of life, and has been associated with low birth weight, hampered lung development in children, through to type 2 diabetes and dementia in the elderly. The health impacts of air pollution have been estimated to cost the NHS between £8.5 and £20.2 billion a year.

Air pollution can be harmful to everyone. However, according to the UK Clean Air Strategy 2019, certain groups are more at risk than others. Many of these are based on health or age status, with the more vulnerable being older people, children, those with pre-existing health conditions, and pregnant women. Poor air quality also has greater impact risk on low-income communities. The disadvantages associated with low income bring about higher chances of pre-existing medical conditions, living in areas with poorer outdoor and indoor air quality, and reduce the chances of access to decent housing, healthy food and green spaces.

 Air pollutants

There are a number of chemical pollutants that form ‘air pollution’. These pollutants are emitted from a variety of sources and have differing impacts, both on health and environment. Information on each pollutant, sources and impacts are summarised below from UK Health Matters, Clean Air Strategy, and World Health Organisation (WHO) material. The focus is on outdoor air pollution, but it is worth noting that indoor air pollution has also been highlighted as a health risk, with measures such as the Smoke Control Areas beginning to come into place in some NI council areas.

The following table summarises some of the key pollutants found in the air in the UK and their potential health impacts.

Pollutant Further Detail Health Impacts Sources
Particulate Matter (PM) Generic term to describe both solid and liquid particles of a small enough particle size to cause harm. They can be further categorised into PM10 and PM2.5, particles of diameter smaller than 10 or 2.5 microns (µm)¹ respectively. Above 10 µm particles tend to remain in the throat and neck, but below 10 µm, and especially fine particles below 2.5 µm, cause harm on drawing into the lungs and entering the bloodstream. The PM can then lodge in organs and can be toxic, or transport toxic substances, causing both short-term acute and long-term harm. Man-made PM comes primarily from domestic wood and coal burning, industrial combustion, road transport, and industrial processes. It can also come from material wear such as rubber tyres and plastics.
Nitrogen dioxide (NO2) and nitric oxide (NO), also known as nitrogen oxides (NOx) Produced during combustion processes, and contribute to the production of photochemical smog and ozone. In high concentrations (above 200 µg/m3) it is a toxic gas, and short-term exposure can cause inflammation of the airways and susceptibility to infection. Long-term exposure has been linked to reduced lung function growth and exacerbation of pre-existing lung and heart conditions. The main sources of NOx are from road transport, energy generation, domestic and industrial combustion, and rail and shipping transport.
Sulphur Dioxide (SO2) Produced during combustion of fossil fuels containing sulphur, it is acidic and can dissolve in water (acid rain) and react to produce sulphates which are PM particles. SO2 alone is a respiratory irritant, which can cause constriction of the airways and affect lung function, with symptoms appearing within 10 minutes at concentrations of 500 µg/m3. SO2 can be especially damaging to the environment and biodiversity. It is mostly produced from energy generation, industrial combustion and domestic combustion.
Ammonia (NH3) Gas is released to the atmosphere where it can react to form fine PM2.5. The gas and subsequent PM also deposit back to land, where they cause nitrogen enrichment (eutrophication) and acidification of soil and water. The direct health impacts are from the resulting PM matter, but ammonia deposited on land and water can cause long-term damage to ecosystems and habitats. The majority of ammonia is produced from agricultural activities, with a small proportion also from industrial processes, human waste, and transport.
Ozone (O3) This gas occurs both in the upper atmosphere (the ‘ozone layer’) and at ground level, where it is the main component of photochemical smog. It can cause breathing problems, inflammation of the respiratory tract, eyes, nose and throat, and can trigger asthma attacks, and damage crops. Ozone is not emitted directly, but forms as a result of interactions between other pollutants, such as reactions of NOx and volatile organic compounds (VOCs).
Carbon monoxide (CO) Gas produced from incomplete combustion of fuels (with a lack of oxygen), often in households. It is most dangerous and fatal in high indoor concentrations. Low exposure levels can cause symptoms resembling flu, viral infections and food poisoning. CO is generally emitted from charcoal burning, vehicles, and cigarette smoke.
Non-Methane Volatile Organic Compounds (NMVOCs) Covers a wide group of organic compounds, generally products of combustion or from other chemicals. They can react to form O3 and PM, which are the main sources of harm to health.

A specific NMVOC is formaldehyde, which can cause irritation to eyes and upper airways and is classified as a human carcinogen.

NMVOCs are produced from industrial processes, and are harmful indoors from domestic activities such as cooking and cleaning.

Formaldehyde can be released from furniture, finishes and building materials.

Table 1: A summary of air pollutants and their potential health impacts


An image showing Belfast, taken from an elevated position
Belfast has one of the three locations in Northern Ireland which exceeded annual NO2 limits set by the EU (a free public domain image from GoodFreePhotos)


Legislation and standards in Northern Ireland and across the UK

In Northern Ireland, the EU Air Quality Directives are transposed in the Air Quality Standards Regulations (Northern Ireland) 2010, placing a duty to monitor air pollutant levels and ensure compliance with the limits set. The Air Quality NI website has details of those monitoring stations and further information. Most recently, the UK Government ‘Clean Air Strategy’ (2019) sets out the strategy for tackling air pollution and halving the number of people in the UK living above WHO limits, which are more stringent than the current limits set within the EU. The impact of Brexit on air quality may see no change to the limits and international agreements set. The loss of EU monitoring and enforcement may, however, lead to the need for a new statutory independent watchdog to hold government to account.

The WHO has published guidelines for some limits on air pollutants, and whilst not currently statutory, they are mentioned as being taken up within the UK Clean Air Strategy 2019. In 2016, 91% of the global population were living in areas exceeding WHO air pollution limits. The WHO air pollution limits, currently in the process of being updated for 2020, are:

  • PM5: 10 µg/m3 annual mean, 25 µg/m3 24-hour mean
  • PM10: 20 µg/m3 annual mean, 50 µg/m3 24-hour mean
  • NO2: 40 µg/m3 annual mean, 200 µg/m3 1-hour mean
  • SO2: 20 µg/m3 24-hour mean, 500 µg/m3 10-minute mean
  • O3: 100 µg/m3 8-hour mean

Air quality in Northern Ireland is generally better than the UK average. In 2017 all 12 monitored air pollutants were within the EU set limits except for three roadside locations (Belfast Stockman’s Lane, Downpatrick Roadside, and Limavady Dungiven) which exceeded annual NO2 limits. In relation to the EU and EU limits, the UK generally falls within limits for most pollutants except for NO2, where the highest values recorded are amongst the highest in Europe. PM limit values can and have also been breached in the winter months due to domestic combustion use for home heating.

Prevention measures

The WHO estimates that:

Most sources of outdoor air pollution are well beyond the control of individuals and demands concerted action by local, national and regional level policy-makers…

It concludes that measures to tackle air pollution should be taken at the local, national and international levels, taking effective action to reduce pollution at source. Public Health England has published a guide particularly targeted to those in a local planning capacity, and there are many measures with proven success and substantial evidence for cost-benefit investment in air quality.

The Royal College of Physicians puts emphasis on the shared acceptance of responsibility and sets out 14 steps for wider society to tackle the problem. Within this are measures individuals can take, both to reduce air pollution and reduce exposure to air pollution:

  • Trying alternatives to petrol or diesel car travel;
  • Improving energy efficiency and reducing use in homes;
  • Maintaining gas and solid fuel burners;
  • Avoiding busy roads, and avoiding exercising outdoors at peak times; and
  • Learning more and staying informed on air quality.



¹The micron is a unit of length equal to a millionth of a metre, or 0.001 mm. For illustration, human hair is between 20 and 180 microns thick.