Impacts of Air Pollution
Air pollution can be defined as presence in the atmosphere of one or more contaminants which may be harmful to the environment, causing impacts on human health, crops, forests, fisheries, semi-natural ecosystems and materials (e.g. corrosion) etc.Air pollution from sulphur and nitrogen emissions can give rise to impacts close to sources in urban areas or in the vicinity of major industries. Pollutants can also cause impacts far from the source, through transfer in the atmosphere by winds, and may also cause impacts across national boundaries. Impacts of air pollution may therefore be both localised and/or transboundary in nature. Pollutants are emitted as gases, such as sulphur dioxide and nitrogen dioxide, and these can have direct impacts on the environment. Furthermore, the nitrogen oxides may react with volatile organic compounds to give rise to ozone gas, which is also damaging to health and vegetation. During transport in the atmosphere the sulphur dioxide is transformed into sulphuric acid and nitrogen oxides into nitric acid, which give rise to acidic deposition, causing potential acidifying effects on ecosystems.
There are a number of ‘regional’ air pollutants including sulphur oxides, nitrogen oxides, ammonia, tropospheric ozone, heavy metals and persistent organic pollutants (POPS). As it is used here ‘regional’ refers to that part of the issue that is not solely local (e.g. urban areas) or global (e.g. global climate change). In that emissions often give rise to local impacts and also regional effects after long-range transport, local impacts are considered part of the regional air pollution problem. Although there are a number of regional air pollutants, which are important in developing countries, the Malé Declaration on Control and Prevention of Air Pollution and its likely Transboundary Effects is concerned with impacts of sulphur and nitrogen compounds and tropospheric ozone.