HEAVY METAL CONTAMINATION IN THE CULTIVATED VEGETABLES AND FARMED TILAPIA AND SHRIMP IN SOUTHWEST BANGLADESH: A STUDY TO HIGHLIGHT PROBABLE HEALTH RISKS (Funded by Research and Innovation Centre, KU)

Abstract/Summary

In southwest Bangladesh, aquaculture and agro-farming have been commercially characterized by the substantial provision of chemical feeds and supplementary agrochemicals to enhance productivity. The degree of metal (As, Cd, Cr, Pb, Cu, and Ni) concentrations in the cultivated fish species (Oreochromis mossambicus,Macrobrachium rosenbergii, and Penaeus monodon) and vegetable species (Solanum lycopersicum, Solanum melongena, and Phaseolus vulgaris) as well as the human health risks posed by detected metals were evaluated. Water, sediment, and fish feed samples from seven randomly selected spots in Satkhira and Khulna districts of Bangladesh, were collected to identify the potential source of the metal contamination in the tested fish and vegetable species. The level of metal concentration was detected by adopting flame-AAS and HG-AAS techniques. The metal contents in the investigated samples were observed in the following order of magnitude: Cu>Cr>Pb>Ni>As>Cd. This pattern demonstrates the similarities between each fish and vegetable species under study. The recorded values of As, Cr, Pb, and Ni content in each fish species were higher than those of the FAO and WHO (1983) permissible levels. Vegetable species have higher levels of As, Cr, Pb, and Ni above the maximum allowable limit suggested by the WHO and FAO (2011). Among fish species M. rosenbergii was identified with the maximum amount of Cu metal intake (4.59 mg/kg) and S. lycopersicum was found among tested vegetable species with the highest EDI of Cu (6.59 mg/kg). The hierarchical arrangement of potential to pose noncarcinogenic risks based on HI scores for tested fish species P. monodon>M. rosenbergii>O. mossambicus and for vegetable species, S. melongena>S. lycopersicum>P. vulgaris. The findings indicate that ingesting any of the tested fish and vegetable species might increase the likelihood of developing carcinogenic risks from exposure to Cd, Cr, and Pb, particularly As, which has the highest TR value of all tilapia and shrimp. P. monodon was found to have aggregated the highest (TRt) (8.10×10-4) among fish species, while S. lycopersicum demonstrated maximum cumulative carcinogenic risks (TRt) (1.39×10-3). Moreover, this study recommends building and enhancing the background knowledge on ingesting heavy metals by cultivated vegetable and fish species, within the context of a comprehensive monitoring and management system.

Summary of the proposal content:

Fish and vegetables are the two main foodstuffs commonly consumed by the Bangladeshi population on a daily basis. Contaminants in the ecosystem have become a crucial concern as they can accumulate in the foodstuffs derived from the surrounding environment. Among the contaminants, heavy metals are the most important pollutants because of their toxicity, accumulation, and biomagnification by aquatic organisms. In the southwest region of Bangladesh, farmers are progressively moving towards intensive agriculture. They are using chemical pesticides and fertilizer in the agricultural field as well as using factor-made feed in aquaculture instead of natural foods, which may often be contaminated with heavy metals such as Chromium (Cr), Cadmium (Cd), Mercury (Hg), Lead (Pb), Zinc (Zn), Manganese (Mn), Iron (Fe), and Copper (Cu). And those heavy metals can settle in sediment or soil, contaminating it with water. Sometimes they use wastewater for irrigation purposes or in aquaculture. Furthermore, sediments from aquaculture ponds are also used in the agricultural field to cultivate crops and vegetables. Finally, contamination in cultivated vegetables and cultured fish may happen through contaminated sediments and water. As a result, intake of this contaminated diet may cause a potential health risk to men since metals can bioaccumulate in the food chain. Taking into consideration the potential toxicity, persistent nature, and environmental pollution, it is deemed necessary to have the baseline environmental data on potential metal contamination in cultivated vegetables, farmed fish, and shrimp, as well as surrounding environmental components like water and sediment.

Duration (months): 24 Months (Two Years)

Total cost (in BDT): 450000/- (Four Lacs Fifty Thousand)

10. Conclusion

 The recorded data of the present study indicates that
▪ As, Cr, Pb, and Ni were detected in fish samples at higher concentrations compared with those of the maximum permissible limit recommended by FAO (1983).
▪ Vegetable species have higher levels of As, Cr, Pb, and Ni above the maximum allowable limit suggested by the WHO and FAO (2011).
▪ Excessive metal contents detected in fish feed, sediment, and water may be responsible for the bioaccumulation of metals in the studied fish and vegetable species.
▪ No metal detected in studied fish and vegetable species is demonstrated individually as posing non-carcinogenic risks to adult consumers.
▪ The detected magnitudes of As, Cd, Cr, and Pb in each of the tested fish and vegetable species were found to potentially pose carcinogenic risks to adult consumers.
▪ Regular monitoring of heavy metal concentrations in farming water, sediments, and environmentally friendly fish feed manufacturing needs to be ensured.
▪ A sustainable aquaculture and agricultural practices should be developed for the conservation of resources for the community.

• Research Project