'Transboundary air pollution' refers to pollution transported in the atmosphere from one country or region to another and often undergoing chemical transformation in the process. As a result of the distances travelled and chemical changes that occur, it is very difficult to pinpoint which emission source (e.g. sulphur dioxide emissions from a factory), in which location, has led to a specific impact in another location (e.g. increased acidity in a lake).
Acidification, eutrophication and ground level ozone are effects of transboundary air pollution, arising from the emissions of the following air quality pollutants:
- Nitrogen oxides
- Sulphur dioxide
- Hydrogen chloride
- Non-methane volatile organic compounds
- Ammonia
- Hydrogen fluoride
Concerns about acidifying pollutants arise as when acidifying species settle and accumulate they can have adverse effects on buildings and vegetation, as well as acidifying streams and lakes and damaging the aquatic environment. Eutrophying pollutants enrich soils or rivers and lakes through rain with higher levels of nitrogen, thereby disturbing the natural balance of nutrient levels and diversity of species in sensitive environments. Ground level ozone precursors play a key role in ozone formation and ozone can affect human health and damage plants and crops.
Particulate matter (PM) is also formed from the long-range transport of precursor gases forming PM through atmospheric processes.
Local air quality can also be affected by emissions of air pollutants. High concentrations of air pollutants are known to be harmful to human health and the environment. In addition to the pollutants which affect transboundary pollution, the NAEI also reports on emissions of pollutants for which the concentrations are subject to air quality objectives and controls under the Air Quality Standards Regulations (2010)
- The Air Quality Standards Regulations 2010 in England (UK Government , 2010), and their December 2016 amendment (UK Government , 2016)
- The Air Quality Standards (Scotland) Regulations 2010 in Scotland (Scottish Government, 2010), and their December 2016 amendment (Scottish Government, 2016)
- The Air Quality Standards (Wales) Regulations 2010 in Wales (Welsh Government, 2010)
- The Air Quality Standards Regulations (Northern Ireland) 2010 (Department of Environment Northern Ireland, 2010) and their December 2016 amendment (DAERA, 2017)
These pollutants are:
- Sulphur dioxide
- Nitrogen dioxide and oxides of nitrogen
- Particulate Matter
- Lead
- Benzene
- Carbon monoxide
- Ozone
- Arsenic
- Cadmium
- Nickel
- Mercury
- Benzo(a)pyrene (BAP) and Polycyclic Aromatic Hydrocarbons (PAHs)