Dirty Dozen a name to indicate world's twelve most toxic chemicals responsible for environmental pollution. Among these 12 chemicals, eight are insecticides-aldrin, dieldrin, chlordane, endrin, heptachlor, DDT, mirex and taxaphene; two are industrial chemicals-PCBs and hexachlorobenzene- and the other two are unwanted by-products of combustion and industrial processes-dioxins and furan. These hazardous chemicals entering in the food chain affect almost all types of organisms globally, and are also known to be linked to birth defects, cancer, and development problems of children.
Since Endrin is highly toxic to fish and other aquatic organisms, it was banned in East Pakistan, now Bangladesh, in 1962. Restrictions have also been imposed on the use of DDT from1990s, although it was banned for general use in USA in 1972. Aldrin, dieldrin, chlordane, and heptachlor are chlorinated cyclodiene organic insecticides. They were widely used in Bangladesh for the control of soil pests. Only recently have their use been prohibited because of their toxic persistent residues. Toxaphene, an organophosphorus insecticide, had been used in the past decades for crop pest control. Since World War II, DDT was the most widely used insecticide throughout the world. In addition to crop pest control, it was most successfully used in the control of mosquitoes that spread malaria and vectors of other arthropod-borne diseases. Because of its high toxicity and persistence in the environment, it is now banned in most countries of the world.
In December, 2000, delegates from 122 countries, including Bangladesh, met in Johannesburg and agreed to ban or severely restrict the use of the 12 toxic materials that are now popularly known as the 'dirty dozen'. The convention also made provision for adding chemicals to the list of persistent organic pollutants (POPs) in the future. It also provides exemptions with deadlines for specific countries to phase out various POPs. On 23rd May, 2001, the officials of 90 countries signed a landmark UN treaty in Stockholm outlawing or restricting the 'dirty dozen' chemical pollutants blamed for causing deaths and diseases worldwide. [SM Humayun Kabir]
See also insecticide.