Developing appropriate pollution control technology on the basis of risk assessment and epidemiological research for the introduction of environmentally sound production processes and suitable safe mass transport.
Most urban air pollution comes from the combustion of fossil fuels, in motor vehicles and for industrial processes, heating and electricity generation, but some also comes from incinerators, petrochemical plants and refineries, metal smelters and the chemicals industry. Some primary pollutants can combine to form even more damaging secondary pollutants. For example, ozone and other photochemical oxidants are formed when hydrocarbons react with nitrogen oxides and oxygen in the presence of sunlight. Tropospheric ozone is one of the major components of urban smog, a growing problem in cities around the world.
This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities.