Atmosphere: North America

Air quality

Emissions of major air pollutants: United States (million tonnes/year)

Emissions of many air pollutants have been reduced over the past 30 years, particularly for CO, VOCs and SO2 Source: US EPA 2001

Over the past 30 years, there have been notable air quality improvements at both regional and local levels in the region. Levels of many air pollutants have been gradually reduced - the trends in the United States (see graph) are representative of the region.

Acid rain control programmes contributed to the dramatic decline in sulphur emissions since 1995 with reductions of 10-25 per cent in some parts of the north-eastern United States (US EPA 2000a). Recent evidence, however, suggests that many sensitive areas are still receiving acid deposition that exceeds their assimilation capacity, and damage caused by acid deposition may be more fundamental than was previously believed (CEC 2000, Munton 1998).

New concerns have arisen over ground level ozone and fine particulate matter, whose emissions have not decreased as markedly as other common pollutants.