Saturday, 15 July 2006

Human Health Risk Due to Food Produced from Soil Contaminated with Urban Industrial Toxic Wastes.

Asim K. Bhattacharyya1, Sudarshana Chandrayan2, and Sutapa Bose2. (1) Jawaharlal Nehru University / School of Environmental Sciences, New Delhi-110067. ( India )., Address For Correspondence :- Pocket - 40 , House No - 5, Chittaranjan Park, New Delhi - 110019, India, (2) Jawaharlal Nehru University / School of Environmental Sciences, New Delhi -110067, India

Land disposal of Industrial toxic wastes poses a great threat to the human health. The present study was undertaken to ascertain the health risks involved in disposal of industrial wastes of Wazirpur, Delhi, which are heterogeneous and highly acidic (Av. pH 3.05) in nature containing a large amount of macro and micro-elements including toxic heavy metals (viz. Fe, Mn, Zn, Cu, Cr, Cd, Ni & Pb). Representative waste samples were observed to contain higher amounts of Fe, Mn, Cr and Ni and other metals viz. Pb, Cu, Zn and Cd were low in concentration. Soils used in this pot culture experiment were collected from JNU (Jawaharlal Nehru University) Nursery (uncontaminated) and Chhattarpur Farm-House (contaminated) They were sandy loam, alkaline, low in available Nitrogen, Phosphorus and C.E.C., but differing in other properties. Both Total as well as DTPA available metal concentrations in Chhattarpur control soils. Both Total and DTPA available metal concentrations in representative waste samples were many times higher than those in both the control soils. The waste samples were lime treated @ 0%, 0.5% and 1.0% and then mixed with homogenized JNU and Chhattarpur soil samples separately with different percentages (10%, 20% and 30%). Pea (Pisum sativum) and Wheat (Triticum aestivum) plants were grown in pots containing these two soils amended with the treated and untreated wastes maintaining 50% moisture of their Water Holding Capacities in a Glass-House Chamber at a constant temperature of around 25C. The samples of Soils and Plants (Roots + Shoots) were collected at the different stages of plant growth. The Seeds/ Grains of the pea and wheat crops were harvested at the end of the experiments. The samples of Soils, Plants and Seeds / Grains were properly processed and chemically analyzed. The chemical analysis of the experimental Plants revealed that the concentrations of heavy metals showed significant increase with waste application and the growth period. The Lime Treatment @0.5% and 1.0% lowered the concentration of all the heavy metals studied. It was found that the pea plants were more susceptible than the wheat plants towards metal toxicity and soil acidity. This fact was supported by the estimation of Translocation Factor (TF) from root to shoot which was higher in pea plants as compared to wheat plants. Larger amounts of heavy metals were retained in roots except in a few cases. The Bio-Concentration Factor (BCF) has been utilized for uptake of heavy metals by plants. The BCF in Pea shoot varied in the order: Mn>Fe>Ni > Zn >Cd > Pb > Cu in all the treatments of both the soils. The BCF in Pea Seeds followed the order: Ni >Cr > Fe= Mn >Pb > Cd = Zn > Cu. Whereas, the BCF in Wheat Shoot varied in the order: Fe > Mn > Cr > Ni > Pb > Cd = Zn > Cu. And the BCF in Wheat Grains followed the order: Fe > Mn > Ni > Cr > Pb > Zn > Cd > Cu. The BCF in Seeds / Grains of Pea & Wheat were quite low as compared to the corresponding values in Shoots of these Plants. Out of the eight (8) heavy metals studied, three (3) heavy metals viz. Cr, Ni & Pb were found to exceed the permissible limits (USEPA) not only in shoots & leaves but also in the seeds / grains of Pea & Wheat crops harvested with reference to pots of 20% & 30% waste amended soils. The Food procured from all the samples with reference to the treatment of 10% waste with 1% lime amended soils were found to contain the heavy metals within the permissible limits. Hence, Land Disposal of these urban Industrial wastes (20% & 30% amendments) poses a serious potential health risk not only to human beings but also to the animals.

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