INFLUENCE OF ENVIRONMENTAL CONTAMINATION ON CHROMIUM AND ZINC CONTENT OF SELECTED EDIBLE VEGETABLES SAFETY AND NUTRITIONAL ASPECT

Abstract

The content of heavy metals in vegetables may be increased by contamination through varioussources. It is therefore important to test and maintain the quality of vegetables in terms of heavymetals, in view of recent recommendations to increase their intake. People who are notexcessively exposed in their occupation to environmental trace element contamination comesinto contact with these pollutants through the contaminated foods and water they ingest.Vegetables are the first link in the trophic chain affected by this contamination.

Chromium and Zinc are essential dements required for normal functions in plants and animals.Chromium has a complicated environmental chemistry and plays a role as both a nutrient and atoxic agent, also as a known carcinogen. Chromium enters the environment as a result of effluentdischarge from steel work, electroplating, tanning industry, oxidative dyeing, chemicalindustries, and cooling water towers. Zinc is biologically one of the most important metal and isapparently necessary to all forms of life. Although it is not very toxic to animals zinc isphytotoxic and soil can be "poisoned" by exposure to zinc smelting or from application of zinc -rich sewage sludge. Zinc oxide is used as an accelerating and activating agent for hardeningrubber product. Tires and tire wear is a major vector for the transfer of Zn to the environment.In this study the Cr & Zn content cf edible vegetables commonly grown and sold in Colombo,Kandy & Balangoda were determined by flame atomic absorption spectrometer(FAAS) after dryashing. For the dry ashing procedure, dried samples were used and ashed at 450 OC overnight.Ashed samples were dissolved in 0.1 M HN03. Extensive validation of the proposed methodwas carried out by the standard addition method

In the FAAS used measurement could be made over a linear range between 0.119-5 ug/ml for Crand 0.0374-1.64 ug/ml Zn respectively. Cr and Zn of Colombo samples varied from 0.0079-0.2044 mg/kg and 1.13-3.59 mg/Kg respectively. Both Cr and Zn levels in Balangoda samplesvaried from 0.006-0.0468 rug/Kg :respectively. Kandy samples also gave similar values asBalangoda samples.

It is seen that the leafy vegetable samples obtained from Colombo had a higher mean level of Crand Zn when compared to those obtained from Kandy and Balangoda: Tubers and roots gavelower mean level of Cr and Zn than leafy vegetables. Therefore it confirms the role ofenvironmental influence to the content of these elements, which could be attributed to thecontaminated soil, dust, sewage or water sources. Results obtained in this study seem to suggestthat environmental contamination plays a role in the Cr content of edible vegetables.