Polluted air has many adverse impacts: on human health, through inhalation of harmful gases and particulates; by damaging biotic and ecosystem functions; through accelerated deterioration of building materials; and by inducing climatic disturbances. In the short term, it is the human health risks, especially chronic respiratory illnesses, that are of greatest concern.
Damage to ecosystems through acidification and acid rain is also causing growing anxiety in some regions. Once regarded only as a problem in Europe and parts of North America, airborne pollution has become apparent in parts of Asia and the Pacific and in Latin America-fuelled literally by the by-products of industrialization. The cause lies largely in the burning of fossil fuels for industry and transport in countries with developed and rapidly growing market economies. The long-range transportation and transboundary effects of such atmospheric processes are increasingly of global concern.

The concentration of people and activities close to urban and industrial areas is of particular concern in Europe-especially in eastern Europe, where poor air quality is considered the most common environmental problem. Large cities in Asia and the Pacific, Latin America, and North America also experience problems of local air pollution. The rapid growth of a number of African cities points to emerging problems of poor urban air quality there in the near future.
The Montreal Protocol clearly illustrated the ability of the international community to quickly mobilize and respond to a scientifically identified environmental problem stemming from ozone depleting substances. Despite coordinated action world-wide, damage to the ozone layer continues faster than expected. The resulting increase of ultraviolet-B radiation in the lower atmosphere has adverse impacts on human health (skin cancer, cataracts, and reduced immune efficiency), on terrestrial and aquatic ecosystems (reduced species survival and productivity), and on building materials (faster deterioration). While ozone depletion continues in the upper atmosphere, rising ozone concentrations in the troposphere have focused world attention on the extent of the human contribution to this problem.

Global warming is yet another universal problem emanating from a changing atmosphere. All regions express concern over global warming and place emphasis on the need for adaptive mechanisms to cope with accompanying climate variability and sea level change.