Health hazard, Herbicides residues, Implication, Monitoring of residue, Non-targeted organisms
Herbicides use is increasing throughout the globe due to increasing labour cost, choice of application of herbicides, quick weed control in crop and non-crop areas. In India, herbicide use has increased up to 30% during the last 10 years in the country. Herbicides are chemical in nature, therefore, excessive and repeated use may pose residue problems, phytotoxicity to crop plants, residual effects on susceptible intercrops or succeeding crops, adverse effects on non-target organisms and ultimately health hazards to human and animals. Many herbicides are found as bound residues which make them not only unavailable to the targets but also polluting the soil ecosystem in a number of ways. Thus monitoring of these residues in soil, water, plants, fishes and other matrixes is very much important. The fate of herbicide in soil depends on adsorption, absorption, volatilization, leaching, runoff, photodecomposition, degradation by microbial and chemical processes etc. In Indian tropical conditions, the half-life of imadazoline, phynylureas, sulfonylureas, triazines, chloroacetinalides, dinitroanilines, diethyl ethers, thiocarbamates, and fop group of herbicides in soil are found to varied 57-71, 13-60, 13-147, 12-58, 5-60, 12-77, 19-29, 19-24, and 8-24 days. At harvest, herbicides in various commodities were found either below the maximum residue limit or below detectable limits. Indirect effects of herbicides are not common in India. However increasing incidences of intentionally acute pisioning by some of the herbicide such as butachlor, fluchloralin, paraquat, 2,4-D, pendimethalin, glyphosate etc. are emerging problem in India. Paraquat poisoning is an uncommon entity in India, and is associated with a high mortality rate. It can be concluded that in India herbicide contamination of soil, plants and natural waters occurs infrequently and at low levels.