Title: Chapter 4: Pesticides as water pollutants
Headings: Chapter 4: Pesticides as water pollutants
Chapter 4: Pesticides as water pollutants
Historical development of pesticides
North-south dilemma over pesticide economics
Fate and effects of pesticides
Factors affecting pesticide toxicity in aquatic systems
Human health effects of pesticides
Ecological effects of pesticides
Natural factors that degrade pesticides
Pesticide monitoring in surface water
Pesticide management and control
The European experience
Pesticide registration
The Danish example
BOX 7: PESTICIDE INFORMATION
Pesticides and water quality in the developing countries

Content: In addition to pesticides used in the normal course of irrigated agriculture, control of vector-borne diseases may require additional application of insecticides such as DDT which have serious and widespread ecological consequences. In order to address this problem, environmental management methods to control breeding of disease vectors are being developed and tested in many irrigation projects (FAO, 1984). Historical development of pesticides
The history of pesticide development and use is the key to understanding how and why pesticides have been an environmental threat to aquatic systems, and why this threat is diminishing in developed countries and remains a problem in many developing countries. Stephenson and Solomon (1993) outlined the chronology presented in Table 16. North-south dilemma over pesticide economics
As noted above, the general progression of pesticide development has moved from highly toxic, persistent and bioaccumulating pesticides such as DDT, to pesticides that degrade rapidly in the environment and are less toxic to non-target organisms. The developed countries have banned many of the older pesticides due to potential toxic effects to man and/or their impacts on ecosystems, in favour of more modern pesticide formulations. In the developing countries, some of the older pesticides remain the cheapest to produce and, for some purposes, remain highly effective as, for example, the use of DDT for malaria control. Developing countries maintain that they cannot afford, for reasons of cost and/or efficacy, to ban certain older pesticides. The dilemma of cost/efficacy versus ecological impacts, including long range impacts via atmospheric transport, and access to modern pesticide formulations at low cost remains a contentious global issue. In addition to ecological impacts in countries of application, pesticides that have been long banned in developed countries (such as DDT, toxaphene, etc.),