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: Often lack specificity and were toxic to user or non-target organisms
1945-1955
Chlorinated organics, DDT, HCCH, chlorinated cyclodienes
Organic synthesis
Persistent, good selectivity, good agricultural properties, good public health performance, resistance, harmful ecological effects
1945-1970
Cholinesterase inhibitors, organophosphorus compounds, carbamates
Organic synthesis, good use of structure-activity relationships
Lower persistence, some user toxicity, some environmental problems
1970-1985
Synthetic pyrethroids, avermectins, juvenile hormone mimics, biological pesticides
Refinement of structure activity relationships, new target systems
Some lack of selectivity, resistance, costs and variable persistence
1985-
Genetically engineered organisms
Transfer of genes for biological pesticides to other organisms and into beneficial plants and animals. Genetic alteration of plants to resist non-target effects of pesticides
Possible problems with mutations and escapes, disruption of microbiological ecology, monopoly on products
The impact on water quality by pesticides is associated with the following factors: · Active ingredient in the pesticide formulation. · Contaminants that exist as impurities in the active ingredient. · Additives that are mixed with the active ingredient (wetting agents, diluents or solvents, extenders, adhesives, buffers, preservatives and emulsifiers). · Degradate that is formed during chemical, microbial or photochemical degradation of the active ingredient. In addition to use of pesticides in agriculture, silviculture also makes extensive use of pesticides. In some countries, such as Canada, where one in ten jobs is in the forest industry, control of forest pests, especially insects, is considered by the industry to be essential. Insecticides are often sprayed by aircraft over very large areas. Irrigated agriculture, especially in tropical and subtropical environments, usually requires modification of the hydrological regime which, in turn, creates habitat that is conducive to breeding of insects such as mosquitoes which are responsible for a variety of vector-borne diseases.