Historical overview and main features
Initial legislation on emissions from point sources
To complement to this legislation on emissions from point sources, EU started to fix, between 1980 and 1985, concentration values - which it called again "limit values", which added to considerable confusion - for sulphur dioxide, dust, lead and nitrogen oxides. In 1996, it reviewed Directive 96/62/EC and decided that it would fix, at EU level, binding concentration levels for thirteen pollutants. Subsequently, between 1999 and 2002, eight of these pollutants were regulated by three pieces of legislation: Directive 1999/30/EC relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in the ambient air; Directive 2000/69/EC relating to limit values for benzene and carbon monoxide in ambient air; and Directive 2002/3/EC relating to ozone in ambient air; which largely updated and strengthened earlier legislation, - the new pollutants added were particulate matters (PM10 and PM2.5). As regards the other five pollutants - cadmium arsenic, nickel, mercury and polycyclic aromatic hydrocarbons (PAH), - EU let itself be persuaded that the fixing of concentration values was not necessary, as most emissions came from industrial installations and were already covered by the requirement to recur to the "best available technique not entailing excessive costs". EU therefore abandoned the idea of binding concentration values in Directive 2004/107/EC and declared that (non-binding) target values for these pollutants should be attained "where possible".
Concentrations of sulphur dioxide and lead in the air diminished progressively, due to measures such as the introduction of lead-free petrol, flue-gas desulphurisation of power plants, or the reduction of sulphur in coal and other fuels. Progressively, thus, the attention concentrated on air pollution by particulate matters and nitrogen dioxides.