THE problem of environmental pollution due to toxic metals has begun to cause concern now in most major metropolitan cities. The toxic heavy metals entering the ecosystem may lead to geoaccumulation, bioaccumulation and biomagnification. Heavy metals like Fe, Cu, Zn, Ni and other trace elements are important for proper functioning of biological systems and their deficiency or excess could lead to a number of disorders.Food chain contamination by heavy metals has become a burning issue in recent years because of their potential accumulation in biosystems through contaminated water, soil and air. Therefore, a better understanding of heavy metal sources, their accumulation in the soil and the effect of their presence in water and soil on plant systems seem to be particularly important issues of present-day research on risk assessments. The main sources of heavy metals to vegetable crops are their growth media (soil, air, nutrient solutions) from which these are taken up by the roots or foliage. Most of our water resources are gradually becoming polluted due to the addition of foreign materials from the surroundings. These include organic matter of plant and animal origin, land surface washing, and industrial and sewage effluents.

Rapid urbanization and industrialization with improper environmental planning often lead to discharge of industrial and sewage effluents into lakes. The lakes have a complex and fragile ecosystem, as they do not have selfcleaning ability and therefore readily accumulate pollutants.  Bellandur Lake, the largest one in Bangalore urban area, recently attracted a lot of public attention because of the formation of froth during rainy season due to chemicals (soaps, detergents, etc.) and biosurfactants. For the last few decades, the treated, partially treated and untreated wastewater has been discharged to this lake and the lake water is being used for farming purposes.

It has been reported that sewage effluents of municipal origin contain appreciable amount of major essential plant nutrients and therefore the fertility levels of the soil are improved considerably under sewage irrigation of crop fields. However, studies on the water of Vasai Creek . Maharashtra, reveal that the presence of toxic heavy metals like Fe, Pb and Hg reduce soil fertility and agricultural output. Treated sewage water also contains variable amounts of heavy metals such as Pb, Ni, Cd, Cu Hg, Zn and Cr, which have the potential to contaminate crops growing under such irrigation.

Comprehensive studies related to the analyses of water,  soil and vegetation around a particular lake are only a few in the country. Therefore, the present study has been undertaken (i) to assess the extent of heavy metal contamination in water, irrigated  soil and grown crop (rice), vegetables (spinach, brinjal, beans and radish) and fruit (banana) using sewagefed Bellandur Lake water, (ii) to investigate the uptake of seven heavy metals in crop plants in order to establish advice regarding consumption of vegetables grown in soils contaminated by heavy metals and (iii) to know the availability of metals (water-soluble) to plants and their accumulation in the food chain, and also to quantify the impact of heavy metals on the vegetation irrigated using lake water.