Every year, between 1,000 and 2,000 new organic and inorganic chemicals are added to some 100,000 already produced commercially. Though all chemicals are toxic, the vast majority are not provided with toxicity data. Waste which contains potentially toxic chemicals are simply considered hazardous. Toxic chemicals are released into the environment directly or indirectly as wastes from other activities. Once released, many chemicals undergo transformation and some may be carried away by the elements to cause regional or global chemical pollution. Worldwide some 338 million tonnes of hazardous wastes are produced every year, about 80% of which are produced in the USA and Western Europe. Over the years, most hazardous waste has been deposited in landfills or stored in surface impoundments. Leaks from such sites have contaminated groundwater and soil in some cases and as time passes many more are considered potentially dangerous sites. Clean-up costs may involve huge sums of money. The risk to human health and the environment depends on the degree of toxicity and length of exposure. In the last 20 years concern over acute health effects has broadened to include such chronic effects as birth defects, genetic and neurological disorders, and cancer. Hazardous waste management policy, including their export for treatment or disposal, has until recently been chiefly tied to economic considerations. Since the 1980s industrialized countries have tightened their controls over the movement and disposal of hazardous waste as ecological concern and impact increases. As a result, illegal dumping and traffic have increased.
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. Agenda 21 recommends adopting technical guidelines for the environmentally sound management of hazardous wastes and support for the implementation of regional and international conventions.