Trace Metal Contamination of Vegetables Grown Near the Tannery Estate in Savar, Bangladesh: Human Health Risk Assessment

Abstract

Environmental pollution caused by tanneries is a long-term problem in Bangladesh. The present study investigated the levels of five globally alarming trace metals (Cd, Pb, Cu, Ni and Cr) in three commonly consumed leafy vegetables with corresponding soils (spinach – Spinacia oleracea ; broccoli – Brassica oleracea var-italica and stem amaranth – Amaranthus viridis), grown around the tannery estate in Savar, Bangladesh. Both in the soil and the vegetable samples, the observed trend of mean concentration of heavy metals was Cd>Cr>Cu>Ni>Pb. Excluding Cu and Cr in the vegetable samples, the level of all the studied metals in all the samples was higher than the maximum permissible limits set by the WHO. Plant transfer factor (PTF) was calculated in order to evaluate the metal uptake of the vegetables from the soil. PTF was found in increasing sequence of broccoli > stem amaranth > spinach and the trend of metal uptake found was, for spinach: Cu>Pb>Ni>Cr>Cd, for broccoli: Cu>Cr>Pb>Ni>Cd and for stem amaranth: Ni>Cu>Pb>Cr>Cd. Contamination factor (Cf) values revealed that the soil samples were highly contaminated by Cd. The values of the pollution load index (PLI) for spinach and stem amaranth were higher than 1, denoting the polluted state of the soil. To evaluate the potential health risk, target hazard quotient (THQ), hazard index (HI), and target cancer risk (TR) were analysed and the results showed that most of the values were significantly higher than the threshold values. This environmental assessment study should be of use during planning and management that aims to protect human health and the environment.