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Health Risk Assessment of Metals Transfer from Soil to the Edible Part of Some Vegetables Grown in Patuakhali Province of Bangladesh

Md. Saiful Islam*
Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali-8602, BANGLADESH

Mst. Salma Khanam
Department of Agronomy, Patuakhali Science and Technology University, Dumki, Patuakhali-8602, BANGLADESH

Nazirul Islam Sarker
School of Public Administration, Sichuan University, Chengdu, CHINA

Abstract/ Executive Summary:

This study was conducted to investigate the contamination and chemical speciation of six heavy metals like Cr, Ni, Cu, As, Cd and Pb in soil, their transfer to the edible parts of vegetables i.e. Brinjal (Solanum melongena), Green amaranth (Amaranthus hybridus), Red amaranth (Amaranthus Gangeticus), Bottle gourd (Lagenaria siceraria), Tomato (Solanum lycopersicum), Pumpkin (Cucurbita maxima), Chili (Capsicum annuum L), Carrot (Daucus carota), Bean (Phaseolus vulgaris), Onion (Allium cepa), Potato (Solanum tuberosum) and Lentil (Lens culinaris). The ranges of heavy metals in soil were 3.7-41, 3.9-36, 7.6-46, 2.3-26, 0.61-13 and 4.5-32 mg/kg for Cr, Ni, Cu, As, Cd and Pb, respectively. The metals were mainly associated with the residual fractions of 39%, 41%, 40%, 40%, 34% and 41% for Cr, Ni, Cu, As, Cd and Pb, respectively. In the edible tissues of vegetables, the concentrations of As, Cd and Pb in most vegetable samples exceeded the maximum permissible levels, indicating not safe for human consumption. Target hazard index (HI) value indicates people would experience health risk due to consumption of vegetables. The carcinogenic risk (TR) of As and Pb through consumption of vegetables were higher than the USEPA threshold level (10−6), indicating potential cancer risks.

Keywords: Heavy metals, Health risk, Sequential extraction, Soils, Transfer factor, Vegetables

Location: Patuakhali province of Bangladesh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Heavy metal

Objectives:

The present investigation was, therefore, aimed to assess the chemical speciation of heavy metals in soil, to evaluate the concentrations of heavy metals in commonly consumed vegetables i.e. Brinjal (Solanum melongena), Green amaranth (Amaranthus hybridus), Red amaranth (Amaranthus Gangeticus), Bottle gourd (Lagenaria siceraria), Tomato (Solanum lycopersicum), Pumpkin (Cucurbita maxima), Chili (Capsicum annuum L), Carrot (Daucus carota), Bean (Phaseolus vulgaris), Onion (Allium cepa), Potato (Solanum tuberosum) and Lentil (Lens culinaris) and to estimate the potential non-carcinogenic and carcinogenic health risks of heavy metals for the inhabitants in the study area.

Methodology:

Study area For the present study, the agriculture fields selected besides the Paira River located in the southern part of Bangladesh. The study area is located between latitudes 22º20'49.87'' and 22º27'27.18'' N and longitudes 90º23'58.24'' and 90º26'54.68'' E. Most of the treated and untreated industrial effluents have been continuously discharged to the river. Several acres of agricultural lands have been irrigated by river water and farmers cultivate various types of vegetable crops for their economic importance. As per the information given by the local farmers, we have identified the above area where river water irrigation has been a common practice for many years. The name of the sampling locations was S1: Chargarabdi, S2: Boga ferrighat, S3: Boga, S4: Big vegetable field, Patuakhali, S5: Ferri ghat, Patuakhali, S6: Patuakhali Sadar, S7 & S9: Patuakhali launch ghat area, S8: launch new market and S10: Patuakhali and Galachipa connecting point. Soil and vegetable sampling The sampling was conducted in August−September, 2013. The samples were collected from ten vegetable growing fields beside the Paira River of Patuakhali district located in the southern part of Bangladesh. At each sampling station, soil sample (up to 20 cm) was collected in the form of sub-samples at a distance of about 20 m each from the first sub-sample in five different locations. These sub-samples were thoroughly mixed to form a composite sample and in each station four composite samples were collected. Twelve different vegetable species i.e. Brinjal (Solanum melongena), Green amaranth (Amaranthus hybridus), Red amaranth (Amaranthus Gangeticus), Bottle gourd (Lagenaria siceraria), Tomato (Solanum lycopersicum), Pumpkin (Cucurbita maxima), Chili (Capsicum annuum L), Carrot (Daucus carota), Bean (Phaseolus vulgaris), Onion (Allium cepa), Potato (Solanum tuberosum) and Lentil (Lens culinaris) were collected from the same sites where the soil samples were collected in the study area during the sampling period. At each sampling site, three to five replicate vegetable samples were randomly collected. Soil samples were air-dried at room temperature, then grounded and homogenized. Each vegetable sample was carefully washed with distilled water and the edible part of vegetables was cut into small pieces and then oven-dried at 70–80 °C to attain constant weight (Tiwari et al. 2011). The moisture contents in vegetables were calculated by recording the fresh and dry weights. The dried soil and vegetable samples were crumbled and pulverized with a porcelain mortar and pestle and sieved through 2 mm nylon sieve and stored in an airtight clean zip lock bag in freezer condition up to chemical analysis was carried out. Sample processing All chemicals were analytical grade reagents and Milli-Q (Elix UV5 and MilliQ, Millipore, USA) water was used for solution preparation. For total metal analysis, 0.5 g of the soil sample was treated with 1.5 ml 69% HNO3 (Kanto Chemical Co, Japan) and 4.5 ml concentrated HCl (Kanto Chemical Co, Japan) in a closed Teflon vessel and was digested in a Microwave Digestion System (Berghof speedwave ®). For vegetables, 0.3 g of dried sample was digested with 6 ml 69% HNO3 and 2 ml 30% H2O2 (Wako Chemical Co, Japan) in a Microwave Digestion System. The digested soil and vegetable samples were then transferred into a Teflon beaker and were filtered by using syringe filter (DISMIC® - 25HP PTTF, pore size = 0.45 µm) Toyo Roshi Kaisha, Ltd., Japan and stored in 50 ml polypropylene tubes (Nalgene, New York). For chemical partitioning of metals, soil samples were analyzed by using the Tessier sequential chemical extraction procedure which helps to evaluate the mobility of metals (Tessier et al., 1979). The sequential extraction procedure was divided into five operationally defined chemical fractions: (F1) the exchangeable fraction: readily soluble and exchangeable; (F2) the carbonate bound and specifically adsorbed fraction: carbonate bound, specifically adsorbed and weak organic and inorganic complexes; (F3) the Fe–Mn oxides fraction: bound to iron and manganese oxides (Fe–Mn oxides); (F4) the organic/sulphide fraction: bound to stable organic and/or sulphide (organic) complexes; and (F5) the residual fraction: held in primary and secondary minerals within their crystal structure.

Source of Information: Archives of Agriculture and Environmental Science 3(2): 187-197 (2018)

Article Link (Online Journal): https://doi.org/10.26832/24566632.2018.0302013

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The results from the sequential extraction procedures revealed that Cr, Ni, Cu, As, Cd and Pb in soils were mainly associated with residual fraction followed by the organic matter bound fractions. Vegetables grown in the nearby sites were also contaminated by the relevant metals, especially As, Cd and Pb, which could be a potential health concern to the local residents. Most of the metals from dietary intake of vegetables were higher than the maximum tolerable daily intake (MTDI), suggesting a considerable risk. Since, the transfer of metals from soil to vegetables, Cu and Ni were indicated to have higher TF values than other metals. THQ revealed that the consumption of studied vegetable species can result in adverse non-carcinogenic health risks to the consumers. The results also elucidated that the concentrations of As and Pb in vegetable species might exert lifetime cancer risks in the consumers. The findings of this study significantly contribute to the field of food safety, considering the health risk for the Bangladeshi population as it represents the composite samples of highly consumed vegetables, grown and consumed in the country.

Knowledge Management: Journal