What is air pollution?
Air pollution is a term used to describe particles in the air that can have negative impacts on people’s health. Air pollution can affect everyone but can especially affect more vulnerable people. People who may be affected more include younger and older people as well as those with certain health conditions (such as asthma). Although air pollution can occur naturally, most elevated air pollution nowadays occurs because of human activity such as travel and transport (e.g. car use), combustion and industrial activity.
What are the different types of air pollution?
There are many types of air pollution. The most common types of pollution in the UK are:
- Particulate matter (PM). This is a mixture of varying size particles that can cause both lung and wider health impacts. Particles small enough to be inhaled are generally classified as ‘PM10’ or smaller. The number refers to the size of the particle (so PM10 particles are bigger than PM2.5). Very small particulates have been found to produce more serious health impacts, as they can enter deeper into our body. PM can be emitted by both natural sources, such as trees and vegetation, as well as from man-made sources, and are closely associated with the burning of fossil fuels and wood. PM can travel over large distances. It can include a number of different chemicals and is classified as carcinogenic (potential to cause cancer) by the International Agency for Research on Cancer.
- Nitrogen Oxides (NOx) is an umbrella term for a group of gases which includes nitrogen dioxide (NO2). These are mainly released through fossil fuel burning. Around 50% of NO2 released in the UK is from road traffic emissions (and from burning fossil fuels in a combustion engine). Gas boilers in buildings are also a source of NO2. Exposure to NOx can lead to health issues such as shortness of breath and reduced immunity to lung infections.
- Ammonia (NH₃) is a gas created mostly through agricultural processes. Direct exposure to low levels of ammonia may cause irritation to the eyes, nose and throat. Though it only stays in the atmosphere for a few hours it can mix with other gases in the atmosphere to form particulate matter.
- Sulphur dioxide (SO₂) exposure is associated with asthma and chronic bronchitis, and can lead to irritation and constriction of the airways. SO2 emitted from coal burning played a key contributory role to thousands of respiratory-related deaths during the London smog in 1952. UK emissions of SO2 from energy production have been vastly reduced in recent decades due to restrictions on the sulphur content of fuels and the closure of coal-fired power plants and there are aims to reduce SO2 emissions further.
- Non-methane volatile organic compounds (NMVOCs) present a number of negative impacts on health and the environment. They come from substances such as glues, paints and domestic aerosols (including body sprays and air fresheners). NMVOCs can react with other air pollutants to produce ozone which poses risks to health by triggering inflammation and asthma.
NMVOCs also pose a threat to health indoors as they can react with chemicals from smoking, heating, cooking or candle burning to produce chemicals like formaldehyde (as well as particulate matter). NMVOC generated formaldehyde can cause irritation to the eyes and upper airways and can be emitted directly from furniture, finishes and building materials such as laminate flooring, kitchen cabinets and wood panels.