Toxicity Evaluation of Pesticide Waste Leachate by Allium Cepa Root (Growth and Cytogenetic)

Dumping of industrial solid wastes in isolated and environmentally sensitive places is a very common practice and this dose poses serious damage not only to the neighbouring ecosystems but in some cases far reaching areas also. A similar pesticide waste dump of a lindane manufacturing industry is selected for this study. Dumped pesticide solid wastes were collected and leachate was extracted from the finely crushed homogenous waste by applying the batch leaching test EN12457-2 in which distilled water was used as a leachant. Higher concentration of chloride and lower amount of biodegradable organic fraction was reported form the physicochemical analysis of the leachate. Residue analysis of the leachate was carried out to quantify the presence of different isomers of HCH. Allium cepa (common onion) bulbs exposed to this leachate showed hampered root growth and morphological deformities. At 15% and higher concentrations of the leachate after 5 days, gall like swellings were noticed around the mitotic zone (zone of root growth). From the dose ₁₅th response curve, the EC₅0 values regarding root growth for the 5^th, 10^th, and 20^th day were calculated and the highest EC50 value, 24.9%, was for the ₅th day while the lowest (most effective) EC50 value, 20%, was for the 20^th day, thus the EC50 decreased from 5^th to the 20^th day successively. The test was extended to 20 days, deviating from the normal five days exposure, in order to mimic the exposure by the leachate under natural conditions. The genotoxicity of the leachate was assessed by the cytological studies on the roots. Observations in the cytological studies showed alterations in the values of mitotic index while the chromosomal studies showed presence of various aberrations such as vagrants, bridges, fragments and other aberrations. The response in root growth pattern, cytological aberrations and majority of the physicochemical parameters indicates that the leachate is toxic.