There are many different types of air pollutant. These pollutants have different effects on the environment and on our health. Some, directly because they are harmful chemicals and others because they can react together to produce harmful chemicals. Other pollutants or pollutant combinations upset the natural balance of acidity and nitrogen in the environment which can affect the diversity of species in sensitive areas. Other pollutants can contribute to changing global conditions and potentially give rise to dramatic changes in climate and sea level.

What are emission inventories?

Emission inventories are estimates of the amount and the type of pollutants that are emitted to the air each year from all sources. There are many sources of air pollution, including traffic, household heating, agriculture and industrial processes.

Emission inventories don't directly tell you about the quality of the air you are breathing

Its not just the quantity of pollutant that is important, its also the way that the pollutant is emitted. Emissions from high chimneys (e.g. power stations) will not affect local pollution concentrations as much as the same quantity of emissions from cars and buses. This is because pollutants emitted close to the ground does not generally get dispersed as well as pollution further from the ground.

Different pollutants, in different quantities, have different effects

There are many different pollutants and each one has different environmental effects. The mass of emissions of two different pollutants shown on this website should not be compared directly because their effects on health and the environment may be very different. For example:

Carbon dioxide (CO₂) contributes to global warming, but has an insignificant direct effect on health.

A number of pollutants are toxic to humans and the environment. These include particles (PM10), heavy metals, NO₂ from NOx and some Non Methane Volatile Organic Compounds (NMVOCs).

Pollutants such as SO₂, NOx and ammonia cause acidification (including acid rain), which can damage ecosystems and buildings.

Combinations of some of these pollutants in the air can react together, to produce other pollutants, known as secondary pollutants. For example, ozone is made by a chemical reaction between other pollutants in the air. At ground level, it can have affect peoples' health and can damage crops, forests and some materials. Find out about emissions in your area