Public Health Risk Assessment of Heavy Metal Uptake by Vegetables Grown at a Waste-water-Irrigated Site in Dhaka, Bangladesh

BACKGROUND: Wastewater is often used in developing countries for irrigation of crops. This wastewater often contains a number of heavy metals which are harmful to human health due to their non-biodegradable nature, long biological half-lives and their potential to accumulate in different body parts. There are many potential risks to human health from heavy metal contamination of vegetables grown at waste-water-irrigated sites. OBJECTIVES: This study was carried out to assess the concentration of heavy metals and the risk to human health by heavy metals (lead (Pb), nickel (Ni) and arsenic (As)) through the intake of locally grown vegetables collected from wastewater irrigated agricultural fields. The objectives of the present study were to determine concentrations of heavy metals in vegetables collected from the wastewater-irrigated fields, to calculate daily intake of heavy metals from the consumption of vegetables for both adults and children, and to evaluate their potential health risk. METHODS: Twenty-seven samples of nine different types of vegetables were analyzed by an Atomic Absorption Spectrometer (AAS) (Varian AAS 240 F S). RESULTS: The range of various metals in waste-water irrigated vegetables were not detected (ND)-0.188, 0.072-1.069 and ND-0.076 mg/kg for Pb, Ni and As, respectively. The highest mean concentration of all metals was detected in jute leaf, except for Pb which was found in the stem amaranth leaf. The mean concentration of all metals in all vegetables was within the safe limits of the World Health Organization/Food and Agricultural Organization (WHO/FAO) and China's national standards. The health risk index was more than 1 for As in jute leaf for both adults and children. The metal pollution index was highest (0.16 mg/kg) in jute leaf, whereas green papaya showed the lowest metal pollution index (MPI) value (0.005 mg/kg). Among all vegetables tested, the highest intake values of Ni and As were from consumption of jute leaf and the highest intake values of Pb from consumption of stem amaranth leaf for both adults and children. CONCLUSIONS: Higher values in the metal pollution index and health risk index indicate heavy metal contamination in wastewater-irrigated soils that present the potential for a significant negative impact on human health.