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Heavy Metal Contamination of Vegetables Grown in Chapai Nawabganj, Bangladesh and Its Implication to Daily Intake for Human Health

M. R. Islam
Department of Soil Science, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.

M. E. Hoque
Department of Soil Science, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.

M. Jahiruddin
Department of Soil Science, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.

S. Islam
Department of Soil Science, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.

Abstract/ Executive Summary:

A study was undertaken to determine thc extern or heavy metal contamination in 24 different types of vegetables (7 leafy, 13 fruity, and 4 root & tuber) grown on five intensively vegetable growing areas of Chapai Nawabganj district of Bangladesh during March to April 2003-04. A wide variation in arsenic, lead, cadmium, iron, manganese and zinc concentrations (dry weight basis) in vegetables were observed. The lowest As concentration was found in bottle gourd (0.31 µg g^-1) and the highest one was found in cabbage (0.81 µg g^-1). The concentrations of Pb and Cd were higher in root & tuber vegetables compared to those or leafy and fruity vegetables, while reverse was true for Mn and Fe. Pb and Cd concentrations of the vegetables ranged from 0.03 to 0.70 µg g^-1 and 0.02 to 0.36 µg g^-1, respectively. The intake of 130 g fresh vegetables daily by an adult of 60 kg body weight contributes only 2.4-16.4%, 0.2-5.0%, 0.4-13.4% of the permissible maximum tolerable daily intake (PMTDI) for As, Pb and Cd, respectively. The same amount of vegetables supplies considerable amount of essential trace elements like Fe, Mn and Zn for human.

Keywords: Arsenic, Cadmium, Lead, lron, Zinc,Vegetables

Location: Chapai Nawabganj, Bangladesh

Start Date: 00-03-2003

End Date: 00-04-2004

Program Area: Risk Management in Agriculture

Commodity: Contamination of soil

Objectives:

(i) To determine the level of contamination of As, Cd, Pb, Zn, Mn and Fe in vegetables of five intensively vegetable growing areas of Chapai Nawabganj, Bangladesh.

(ii) To estimate their contribution to daily ingestion of heavy metals for people.

Methodology:

Chapai Nawabganj is located in the north-west part of Bangladesh between 24° 25' North latitudes and between 88° 58' and 88° 30' East longitudes. It belongs to the AEZ 11 of High Ganges River floodplain. The area has complex mixture of calcareous silt loam, silty and silty clay loam alluvium. Organic matter status ranged from 0.78 to 2.42% with a mean of 1.73% and soil pH from 7.45 to 8.16 with a mean of 7.92. The mean concentrations of total As. Pb, Cd, Fe, Mn and Zn in the soils were 8.73, 16.2, 0.26, 4043, 162 and 62.7 µg g^-1, respectively. Vegetables are grown intensively in these areas using shallow tube-wells for irrigation purpose. Irrigation water contains a high level of arsenic (350 ± 48 ppb, n=5). One hundred and thirty five vegetable samples covering 24 different types were collected from five intensively vegetable growing areas, namely, Tikra, Hotathpara, Ghorapakhia. Ranihati and Noylabanga using a random sampling procedure. The vegetables were washed with water to remove dusts adhering on the surface. The vegetable samples were put into the individual polythene bag and brought to the laboratory. The edible portion of the vegetables was used for analysis. Vegetable samples were cut into small pieces and air-dried. Then the samples were dried in an oven at 65°C for 48 hours and ground using a ceramic coated grinder for heavy metal analysis. A sub-sample weighing 0.5 g was transferred into a dry clean digestion vessel. Five ml of HNO₃ was added and the sample was allowed to stand for over night under fume hood. The following day, the vessels were placed on a heating block and heated at a temperature slowly raised to 120°C for two hours. After cooling, 2 ml of hydrogen per oxide (H₂O₂) was added and kept for few minutes. Again, the vessel was heated at 120°C. Heating was momentarily stopped when the dense white fumes occurred, after which the volume was reduced to 3-4 ml. The digest was cooled, filtered through Whatman No. 42 filter paper into plastic bottle and diluted to 50 ml with deionized water. Arsenic content \\JS determined from the digest by now ingestion hydride generator atomic absorption spectrophotometer (AAS) with UNICAM Model No. 969 with a hydride generator assembly using matrix-matched standards. Lead, Cd, Zn, Mn and Fe were determined by using the AAS at 193.7, 217.0, 213.9, 279.6 and 248.4 nm, respectively. For each set of digest, blank and standard solutions were included to determine the recovery of element from the solution. Recovery of different heavy metals from the standard solution was 88-93% (n=16). The presented data have not been corrected for these recoveries. Mean and standard deviation of the concentrations of heavy metals in vegetables were calculated using the MSTATC programme.

Source of Information: Bangladesh, J. Agric. and Environ. 1 (1): 37-47. June 2005, ISSN: 1816-0808

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Vegetables are bulky in nature and contain high amount of moisture. Our study shows that the moisture percentage of the fresh vegetables ranges from 73 to 94%. Therefore, the dry weights of vegetables that are consumed by the peoples are very low. The daily vegetable consumption by an adult of Bangladesh is 130 g. The percent dry weight of the vegetables ranges from 6.2 to 26.2%. These amount of vegetables with high concentration of As supply only 2.90 to 19.71 µg As d^-1 which is only 2.4-16.4% of the provisional maximum tolerable daily intake (PMTDI) for an adult of 60 kg body weight. The international standard of As for drinking water is 10 µg As L^-1. If a man drinks 3 L water daily having 10 µg As L^-1, then the ingestion of As is 30 µg d^-1. On the other hand, the consumption of vegetables as to an ingestion of 2.90 to 19.71 µg As d^-1, which is less compared to the As ingestion by the drinking water. Therefore, As in vegetables may not be a threat for human health yet. However, attempts should be taken to get safe drinking and irrigation water. The concentration of Pb and Cd in vegetables is much below the maximum permissible limit for human consumption. On the other hand, the vegetables supply a good amount of Fe, Mn and Zn for human.

Knowledge Management: Journal