Air Pollution

Various countries have set standards in legislation in the form of concentration levels that are believed to be low enough to protect public health. Source emission standards are also specified to limit the discharge of pollutants into the air so that air-quality standards will be achieved. However, the nature of the problem requires the implementation of international environmental treaties, and to this end 49 countries agreed in March 1985 on a United Nations convention to protect the ozone layer. This “Montreal Protocol”, which was renegotiated in 1990 and 1992, called for the phaseout of certain chlorocarbons and fluorocarbons by the end of the century and provides aid to developing countries in making this transition. In addition, several international protocols have been aimed specifically at reducing the incidence of acid rain. In December 1999 the Montreal Protocol announced that almost all production and consumption of virgin ozone depleting substances had been phased out in the developed world. Similar control measures were introduced for developing countries in July 1999, and it was anticipated that all developing countries would be able to meet their freeze targets and subsequent obligations under the protocol.

Concern over trans-boundary air pollution, including acid rain, in Europe has led to the United Nations Economic Commission for Europe (UNECE) developing air quality guidelines, called Critical Loads and Levels, which represent thresholds below which it is believed that damage will not occur to different ecological systems. Critical Loads are based on the amount of acidity that an ecosystem can tolerate being deposited indefinitely. Critical Levels are concentrations of ozone, sulphur dioxide, and nitrogen oxides over different averaging times and applicable to different categories of vegetation. Massive cuts are being made in emissions in Europe in order to move towards these thresholds. In contrast, in many developing countries, pollutant concentrations are rising very rapidly due to increased industrialization and motor traffic; concern in such places is primarily with impacts on human health in cities. The World Health Organization has published air quality guidelines designed to protect health.

See also Occupational and Environmental Diseases; Water Pollution.