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Major environmental health risk factors of agricultural development

Agricultural development issue	Direct environmental changes	Secondary environmental changes	Environmental health and risk factors
Irrigation development	Hydrological changes Waterlogging Salination Increased water surfaces Increased relative humidity	Increased insect populations Increased densities Greater chemical inputs	Introduction of new vector species Increased vector densities Changed vector population composition Prolonged transmission season Chemical poisoning
Land-use changes	Deforestation Reduced biodiversity/habitat Simplification	Changed composition of the insect fauna	Changed vector population composition Changed vector longevity
Cropping patterns	High-yielding varieties Shift from subsistence to cash crops Accelerated cropping cycle Plantation agriculture	Greater chemical inputs Greater densities of insect populations	Poisoning Reduction of predator insects in favour of pest and vector species
Livestock management	Changed in livestock densities and spacial distribution of livestock New breeds of livestock	Changed densities of bloodsucking insects	Changed disease transmission potential
Mechanization	Changes in livestock densities and loss of ecological features Associated with draught animals	Changed densities of bloodsucking insects Reduced refuge areas for predator insects Air and water pollution	Poisoning Introduction of new vector species Development of insecticide resistance in vector populations
Chemical inputs	Increased levels of pesticides, herbicides and/or fertilizer	Chemical contamination Eutrophication of water bodies Expansion of aquatic weeds

Extension and intensification of agricultural production systems, together with fluctuation in the supply of and demand for agricultural produce are causing shifts in the environmental determinants of the health status of local communities. Some of these are masked or ompounded by simultaneous demographic and socioeconomic shifts.

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