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Bio Accumulation of Toxic Heavy Metals in Fish After Feeding with Synthetic Feed: a Potential Health Risk in Bangladesh

Md. Abdul Mannan*
Department of Chemistry, Rajshahi University, Rajshahi, Bangladesh

Md. Saddam Hossain
Department of Chemistry, Rajshahi University, Rajshahi, Bangladesh

Md. Al-Amin Sarker
Department of Fisheries, Rajshahi University, Rajshahi, Bangladesh

Md. Motahar Hossain
Department of Chemistry, Rajshahi University, Rajshahi, Bangladesh

Liton Chandra
Department of Chemistry, Rajshahi University, Rajshahi, Bangladesh

ABM Hamidul Haque
Department of Chemistry, Rajshahi University, Rajshahi, Bangladesh

Md. Kudrat-E-Zahan
Department of Chemistry, Rajshahi University, Rajshahi, Bangladesh

Abstract/ Executive Summary:

This present research was conducted to assess the bioaccumulation of toxic heavy metals in fish before and after six months feeding with synthetic feed. Here in concentrations of eight toxic heavy metals such as chromium (Cr), copper (Cu), cadmium (Cd), lead (Pb), nickel (Ni), zinc (Zn), iron (Fe) and manganese (Mn) were determined by atomic absorption spectrophotometric (AAS) method. Before feeding, the concentrations in fish were found to be 19.5 ppb, 61.8, 30.5, 35.3, 123.3, 121.9, 197.7 and 543.2 ppb, respectively. And after feeding with synthetic feed, the concentrations were found to be 22.1 ppb, 101.5, 37.7, 102.0, 147.6, 214.1, 175.8 and 508.0 ppb, respectively. Contents of the trace metals in the feed, fresh water and the water after addition with synthetic feed were also evaluated. The Labeo rohita locally known as “Rui fish” has been selected for this study since it is a very popular fish in the rural as well as in urban peoples of Bangladesh. The accumulation of beneficial elements i.e., Cu, Zn, Fe and Mn were found to be within the permissible limit in both the fishes before and after feeding with the synthetic feed. Concentrations of potentially toxic metals i.e., Cd, Pb and Ni (37.7 ppb, 102.0, and 147.6 ppb, respectively) accumulated in the fish after six months of feeding were found to be much higher than that of the recommended permissible limit. Concentrations of Cd, Pb and Ni (21.6 ppb, 102.0 and 114.0 ppb, respectively) in the synthetic feed used for feeding were also found to be much higher than the WHO/EU recommended value. Considering the potential health risk issues, it is recommended that the use of natural feed should be encouraged for feeding despite the synthetic feed in the fish farming project

Keywords: Heavy metals; Labeo rohita; Atomic absorption spectroscopy; Wet digestion; Synthetic feed

Location:

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Heavy metal, Fish

Objectives:

Contamination with heavy metals that might be accumulated in the various organs of fishes; and such accumulation may affect humans and other species that depend on such fish as food. In this study, we have analyzed the concentration of heavy metals bioaccumulated in fish before and after feeding with synthetic feed. We also analyzed the metal concentrations in the supplied feed and in the water sample before and after the addition of the feed in the experimental pond. The data were then compared against the recommended maximum permissible levels allowed in food.

Methodology:

Chemicals Analytical grade nitric [Aldrich, 69% (w/w)] and hydrochloric [Aldrich, 36% (w/w)] acids were used for the digestion of fish samples. Standard solutions of, Cr, Cu, Cd, Pb, Fe, Mn, Ni, and Zn were obtained from Merck Germany. The standard solution was diluted to 0.5, 1.0, 1.5 and 2.0 ppm with double distilled water. The absorbance of the solutions was measured immediately and finally, a calibration curve of concentration vs absorbance was constructed. Selection of pond This study was conducted through the cage culture system placed in the pond. The pond was located at the west side of the Rajshahi University residential area, Bangladesh. The study was carried out for the period of 180 days (six months) from December 2016 to May 2017. The average depth of the pond was 2 m, square in the shape of 250 m², well exposed to sunlight, independent and completely free from aquatic vegetation. The pond has inlet and outlet facilities. The main source of water was rainfall but there are facilities to supply water from a deep tube well whenever required. Preparation of cage Two cages each of 1 m3 size was made to run this experiment. The frame of the cages was made of a metallic iron rod and covered by synthetic special nylon knotless net (Makorsha brand) with 5 mm mesh size. The mesh size of the net was selected as it required to prevent the fishes from escaping from the cage and to keep water passing easily through it. An opening was kept at the top of each of the cages for supplying feed and handling of the fishes. The sinking feed was supplied through this opening. The cages were submerged 15 cm above the pond bottom. Two vertical and a horizontal bamboo poles were used to hang the cages. Nylon rope was used to tie the cages to make it float with the help of the bamboo poles. Feeding, cage management and collection of fish samples A very popular and well-known fish Labeo rohita local name “Ruhi” is selected for this study. According to fish size and weight a required amount of feed were given into the experimental cages. The synthetic feed purchased from the local market was given twice a day (in the morning at 9:00 AM and in the evening at 5:00 PM). The net of the cage was cleaned regularly during feeding time and dead fish if observed was removed to keep the environment good for fish. The fishes were sampled initially and after six months intervals with feeding. The initial (200 g) and final body weights (900 g) of the fishes were recorded and the growth rate was determined in terms of the increase of its weight. After six months, the fish was sampled and dissected its edible parts using a stainless stile knife and quickly wrap with plastic bags. The bags were frozen in an icebox until digestion. The samples were then dried overnight on oven at 105°C. The dried specimen of the fish tissue was then powdered in a blending machine. Digestion of fish and feed samples Digestion of the fish and the synthetic feed materials was performed by wet ashing digestion method. The dried specimen was transferred to the furnace oven and completely dried at 550°C. The dried sample was then powdered using mortar and pestle and made ready for the digestion process. 2.0 g of the powdered sample was placed in a 100 mL round bottom flask with a ground glass joint and mineralized under reflux using a mixture of 12.0 mL nitric acid; 4.0 mL perchloric acid. The digestion procedure took 5 h to obtain a clear solution. The solution was then filtered with Whatman filter paper and transferred to a 100 mL volumetric flask and the volume was made to mark. Digestion of the feed materials was the same as discussed for the fish sample. Digestion of water samples The collected water samples were filtered with Whatman filter paper and acidified with 2.0 mL conc. HNO3 acid. The acidified water samples were then transferred to a 100 mL volumetric flask and the volume was made to mark. Instrumentation and calibration Eight toxic heavy metal concentrations in the fish sample such as: Cr, Cd, Cu, Pb, Fe, Mn, Ni, and Zn, were determined by atomic absorption spectrophotometer (SHIMADZU, AA-6800) equipped with flame and graphite furnace at the Central Science Laboratory of Rajshahi University. All the analyses were performed using an air-acetylene flame for the atomization of metal content. Calibration was accomplished using a linear fit for all the elements. The data were rounded off suitably according to the value of standard deviation from measurements in triplicate. Physico-chemical water quality parameters The water quality parameters such as temperature (°C), transparency (cm), pH, dissolved oxygen (mg L-1) and total alkalinity (mg L-1) were measured on the spot at the fortnightly interval at 10:00 AM. Toxic heavy metal concentrations were analyzed in the Central Science Laboratory of Rajshahi University.

Source of Information: J Nutr Food Sci 8: 728.

Article Link (Online Journal): doi: 10.4172/2155-9600.1000728

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

We have studied the bioaccumulation of toxic heavy metals in fish before and after six months of feeding with synthetic feed. The results obtained in this research revealed that the highly concerned toxic Cd and Pb accumulated in fish with concentrations much greater than the recommended value. The Ni concentration was also found to be higher than the permissible limit. The other metal concentration increased in fish after feeding at a certain level but not exceeded the WHO/EU recommended value. The metal concentrations in feed, freshwater, and water collected after six months of feeding were almost lower than that of the WHO/EU value. The highest value of toxic metals accumulated in fish might be due to feeding with synthetic feed. Since, the feed contains a high level of Cd, Pb and Ni concentrations. Finally, considering the safety aspects of human health concern, the use of synthetic feeding that containing a high level of Cd, Pb and Ni must be avoided in the fish firming project rather than the natural feeding.

Knowledge Management: Journal