Non-target and environmental hazards of pesticides

When compared with pesticide pollution from other sources and pollution by other agents, the hazards of atmospheric pollution by pesticides appear relatively insignificant. The high persistency in the environment observed especially with the organochlorines suggests that there could be a gradual accumulation of residual pesticides in the atmosphere. Thus, in addition to the function of redistributing pesticides by air currents and aerial drifts, the atmosphere may become a major reservoir for drift prone finely divided particulate pesticides and highly volatile compounds. Indiscriminate aerial spraying should be avoided. A more selective approach should be adopted whereby forest areas are sprayed without contaminating streams, lakes and inland waters. Improvement in spraying devices are needed such that pesticides are more precisely delivered to target. Direct spraying of water bodies should be avoided as much as possible. Treatment of waste water for pesticide removal or neutralization prior to effluence from factories and disposal of effluence to legally designated sites in addition to chemical treatment of contaminated water are more ways of reducing water pollution. Pesticide residues in soil, in addition to eliminating or reducing parasitic microbes, are also toxic to the non-parasitic and ecologically useful soil microbial and vertebrate population. Pesticides may reduce certain microorganism populations while they stimulate the growth of others, especially the saphrophytic and spore forming types. Soil chemical properties may also be altered by accumulation of residual pesticides and their metabolites. These processes may disrupt the ecological balance in the soil microenvironment, first by simplifying the microbial population, and possibly by reducing soil fertility and its ability to support life. Non-target or residual pesticide toxicity would also disrupt the population of some of the valuable soil invertebrates like earthworms, predatory mites, centipedes and carabid beetles. Accumulation of pesticides in resistant or tolerant species may provoke episodes of toxicity to organisms higher in the food chain. The chlorinated hydrocarbons are likely to be most ecotoxic. Use of such pesticides ought to be restricted. Efforts to find alternatives to pesticides, especially research into biological control, should be intensified.