Bioaccumulation Of Toxic Heavy Metals

Fish, being a protein rich food, is often recommended for consumption by many dieticians. However, the effect of pollution of water reservoirs on the quality of nutrition provided by fish cannot be ignored. It was necessary to focus on toxic substance levels specifically heavy metals which have tendency to bio accumulate. This study investigates the bioaccumulation of heavy metals in the various tissues of Siluriformes fish found in Patalganga River, India. The bioaccumulation often results due to the constant vicinity of fish with the pollutants. Such contaminated fish acts as a pollution indicator of waterbody and also possess life threat to the consumers.

In the present study, fish samples are found to contain high concentration of Lead, Iron, Cadmium, Mercury, and Copper. The gills, muscles and skin of fish from segment of Patalganga river were carefully dissected and analyzed for heavy metal concentration by Atomic Absorption Spectroscopy. The study reveals that fish contains high amount of heavy metals such as Fe, Hg and Cu. Especially muscle which are edible part of fish were found to contain heavy load of copper and mercury. The order of bioaccumulation in different organs found was gills > skin > muscle. The result reveals that polluted water bodies are becoming a serious concern not only for the flora and fauna but also for the human beings and thus require regular biomonitoring.

Introduction

India is endowed with the vast expanse of open fresh water in the form of rivers, canals, natural and manmade reservoirs, lakes, and ponds etc. these are the immense source of freshwater production. These river systems have certain characteristics of their own with respect to their ecology and climatic conditions. These rivers are shelter for large number of living aquatic animals, which are economically important for nature as well as human beings. Fishes found in the rivers are most valuable source of high grade protein and other organic products. Fishes are not only the source of food but they also provide employment opportunity to South Asian population. In recent years, the consumption of fish throughout the world has increased rapidly due to increase in the awareness of its nutritional and therapeutic benefits ( Bawuro et al, 2018, ). Fish consumption is estimated at 30 kg per capita. In addition to being important source of protein, fish are enriched with essential minerals, vitamins, and unsaturated fatty acids (El-Moselhy. 2000). The American Heart Association recommended consumption of fish at least twice per week in order to reach the daily intake of omega-3 fatty acids. As fish is the major component of diet in many countries therefore it is deemed necessary to focus on trace element levels in fish (Zhao S. et al .2012).

Patalganga is the river flowing across huge industrial zone known as Patalganga Industrial Region (PIR). All the treated, semi treated and untreated waste from different sources are released in this river. These pollutants then acts as the source of heavy metals in the waterbody. Fishes normally accumulate these heavy metals from food, water, and sediments of the river. Such contaminated fish acts as a pollution indicator. The presence of toxic heavy metals in fish can invalidate their beneficial effects. Several unfavourable effects of heavy metals to human health have been known for long time. This includes serious threats like renal failure, liver damage, cardiovascular diseases, and even death. Thus, many local and international monitoring programs have been established in order to assess the quality of fish for human consumption and to monitor the health of the aquatic ecosystem. The present investigation indicates the accumulation of heavy metals in the different organs of Siluriformis fish species found in Patalganga River and their hazards to the human health.

Material & Methods

1. Sampling site

Study area of the present study is the Patalganga River catchment area which receives effluent load from its nearby industries. The Latitude of Patalganga River is 18.86o N whileits longitude is 73.14o E. Patalganga Industrial region (PIR) is an important industrial hub of the state of Maharashtra, in India. The area is home to various industries like chemicals, Insecticides, textiles, Pharmaceuticals, Hydro Power Station, Steel, paper, fertilizer, dye, engineering etc. resulting into potentially high level discharge of heavy metals.

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2. Sample analysis

Total 12 samples were collected from the sampling site and stored under freezing condition at 40C. For analysis, the frozen samples were thawed at room temperature and then dissected for analysis using stainless steel scalpels. The gills, skins and muscles of the fish were dried in an oven at 40°C for two days until they reached to a constant weight. Each dried sample was powdered using a porcelain mortar and pestle. A one gram dry weight of the powdered form of muscle and gill and skin were used for analysis. The samples were digested by adding mixture of conc. nitric acid and perchloric acid in 1:1 ratio. The solutions were heated to obtain a clear solution. After filtration the solution was diluted to 25 mL with double distilled water. Concentrations of Fe, Cu, Pb, Hg and Cd were assayed by using atomic absorption spectroscopy technique. [SHIMADZU, AA-7000]. All the glassware were washed in nitric acid for 15 minutes and rinsed with double distilled water before being used.

Result & Discussion

The findings of the study show that the fish species under study contained the metal concentration above prescribed limit (FAO/WHO 1984, 1989)

Heavy load of heavy metals such as Fe, Cu and Hg is found in gills, skin and muscle of the Siluriformes fish collected from Patalganga River. The study revealed that highly polluted water bodies are responsible for the accumulation high level of pollutants in fish. The order of bioaccumulation is found to be muscle < skin < gills which is in agreement with many previous studies [Voigt 2004, Jayakumar & Paul 2006]. Gills are pathways of metal ion exchange from water, because gills have very wide surface area that fastens diffusion of metals rapidly as a result gills are highly exposed to polluted water. Skin is also in continuous contact with water showing high accumulation of heavy metals than muscle. However, being edible part, muscles only can transfer heavy metals to human consumer. Metal concentrations in the fish followed an order: Fe > Cu > Hg > Pb > Cd. This order is in agreement with previous studies [Ghani.et al.2013]. High concentration of fe, Cu and especially Hg in muscles can pose threat to health of regular consumers.

Toxicological effect

The muscle is major part consumed by the human population. Hence the muscles of fishes loaded with heavy metal can show deleterious effect on human health [Jaishanjar et al, 2014]. Mercury accumulates in the body and causes neurological disorder that is passed to the later generations. Mercury is present in the sediments due to the release of effluents from industries and other anthropogenic activities. Siluriformes are the fish species that live in shallow water and feeds around the nearby sediments. This results in accumulation of high amount of mercury in the fish body, which when consumed by the other fishes and humans causes different health hazards and also affect the food chain. Even the metal present in less amount can get accumulated in human body due to regular consumption of contaminated food and pose danger to health. Like many other trace elements iron is an essential element. The level of iron in the body is tightly regulated, this is done by regulating the rate of absorption. Increased iron level can act as pro-oxidant and causes iron poisoning (Chang et al, 2011). Copper is a significant trace element necessary for the normal growth and metabolism of living organisms. However, this element may become very dangerous if used beyond its limit, turning into continuous metal compounds with the ability to accumulate in water and cause imbalance to the biological system. (Padrilah, et al.2018). Acute symptoms of copper contamination by ingestion include vomiting, hematemesis (vomiting blood), and gastrointestinal distress (Arwind, 2002). The accumulation of heavy metals in the body part of fishes shows that the river water is loaded with heavy metals.

Conclusion

In conclusion, the fish sample collected from Patalganga river are contaminated with the toxic metals. Concentration of Copper, Mercury, Iron were found more than prescribed limit whereas lead and cadmium were found in trace amount. High concentration of Hg in the fishes studied is a major cause of concern as it is highly bioaccumulative and have many adverse health effects. Metals found in low concentration should not be neglected as the bioaccumulation is time related. Thus, the regular monitoring of heavy metals in fish is essentially required. Also, risk assessment study and awareness among the local people is recommended.