Bioaccumulation of a Contaminant in Fish

Mercury – Methyl-mercury. Bioaccumulation of a Contaminant in Fish, as we all known and learned, Mercury (Hg) is well known as an environmental pollutant for very long and it is the very highly toxic element that is found both naturally and man-made or industries pollutant in the environment. The pollutant has serious effects on human health and as well as ecological system health. The public health and health care providers are repeatedly being warmed us how mercury contamination of aquatic ecosystem transferred to human health due to the food chain.  Pregnant women are warned that avoid consuming fish during pregnancy because fish can carry high methylmercury level. Like many environmental contaminants, mercury undergoes bioaccumulation.  The U.S. Environmental Protection Agency (EPA) has stated that for most people, A primary route of mercury exposure is when eating fish that have mercury-contaminated.

Mercury Bioaccumulation in Food Chain:

This is because the food source for organisms in the food chain is increasingly concentrated in mercury and other contaminants, thus increasing the bioaccumulation rate at the top of the food chain. We all know that mercury bioaccumulation through the food chain, but it is also unknown what the exact mechanisms by which mercury enters the food chain are likely to vary between ecosystems. The other mechanism seems like most bacteria play an important role in the early part. The microbes that process sulfate in the environment digest mercury in its inorganic form and transform it to mercury toxicity via biological processes, according to the research studies. For two reasons, the conversion of inorganic mercury to methylmercury is valuable, methylmercury is much more toxic than inorganic mercury, and organisms need to eliminate methylmercury significantly longer (Harding, Dalziel, & Vass, 2018)2. Thus, the process of bioaccumulation in the food chain is a complex process. We do know that human exposure to Methylmercury from consuming mercury-contaminated fish. The clear mechanism to understand the Mercury bioaccumulation in the food chain in the ecological system, the cycle explained in figure 1.

Figure 1.U.S Geological Survey (USGS). Copyright Lewis Publishers, an imprint of CRC Press

Thread to human health:

According to U.S Geological Survey (USGS), human uptake mercury in two ways. First; as methylmercury from fish consumption, or second, by breathing vaporous mercury emitted from various sources such as metallic mercury, dental amalgams, and ambient air. The second part of Hg exposure doesn’t seem much impact on human health. Methylmercury, in contract, the primary exposure is ingestion, which affects the central nervous system and in-service case irreversibly damage area of the brain and the most prevalent to human (Krabbenhoft & Rickert, 2018).

Minamata – The unfolding mercury disaster

In the history documented, the most severe methylmercury poisoning is from Minamata Bay, Japan in 1956 when the industrial release of methyl-mercury. Due to the Minamata Disease (M.d.), hundreds of people died, and thousands were affected, many with permanent damage. In milder instances of mercury harming, adults whine of decreases in movements and dulled sense of touch, taste, and sight. These milder impacts are commonly reversible if the presentation to mercury is ended. Unborn babies are at most serious hazard from the low-level introduction to methylmercury. Recent Research proposes that pre-birth impacts happen at admission levels 5-10 times lower than that of grown-ups. If these results are confirmed, a substantial fraction of unborn children would be at risk (Harada, 1995).

Thread to Ecosystem Health: Ecosystem Health-Cycle in term of bioaccumulation (Right)- Figure 2.

Figure 2: Simplified schematic of biomagnification (left) and bioaccumulation (right) processes of methylmercury in the ecosystem. Copyright www.canda.ca.

The U.S Environmental Protection Agency (EPA) has determined that in water marine ecosystems, birds and mammals eating fish are more exposed to methylmercury than other animals. There’s also a risk of predators eating these mammals and birds. In eagles, otters and endangered Florida panthers, methyl mercury has been discovered. The harmful effects of methylmercury on these animals at high concentrations include death, reduced reproduction, slower growth and development, and abnormal behavior.

In Canada, there are a substantial number of aquatic environments in which there is a sufficiently high level of mercury in fish-eating according to wildlife management. Methylmercury, the organic form of mercury, is of greatest concern to human health and the environment due to its high toxicity and its ability to accumulate in the tissues of organisms and become more highly concentrated following the move from prey species to predators. Thus, predatory fish and wildlife at the top of aquatic food chains can have mercury concentrations in their tissues 1 000 000 times greater than the concentrations in the freshwater where they live (Climate Change Canada, 2017).

Mercury: From Source to Seafood by Dartmouth

Consumption advisories and Prevention of Fish-Methylmercury contaminated.  

Kentucky: As a state level, Kentucky also well known at the mercury-contaminated on Kentucky’s water surface and now mercury is found in some fish in Kentucky. The prevention step is taken, the statewide advisor charges/tables were created based on the waterways and many kinds of fish in Kentucky water should be consumed with caution. The Kentucky Departments for Environmental Protection, Health Services and Fish and Wildlife Resources jointly issue a fish consumption advisory to the public when fish are found contaminated. An advisory warns people about potential health problems precipitated by fish caught in an area. An advisory does not really restrict fish; it is a harm reduction guide. This guide tells you how often fish can be eaten relatively safely.

The Kentucky Department of Fish and Wildlife Resource has advised that the rate of consumption of specific fish was established because of a meal of 1/2 pound of fish (before cooking) eaten by an individual with 150 pounds. It is stated that fillet the fish, remove the skin and trim all fat, avoid eating fish eggs, instead of frying or microwaving suggested that boil and grill them, and avoid eating or reusing juices or fats that cook out of the fish.  This is because, there is a sensitive population category exit for women of childbirth, children 6 years of age or younger, pregnant and nursing women and women who plan to become pregnant.

Canada: The Government of Canadian, the Canadian Food Inspection Agency (CFIA) has admitted that in term of fish consumption can have a beneficial and harmful effect on childhood neurodevelopment, but many public. As a result, determining whether the benefits of fish consumption outweigh the risks is challenging, although some researchers have tried to do so. Health Canada recently issued advice on mercury consumption in fish in 2002. This advice is now being updated to better reflect the latest data on mercury levels in retail fish and Canadians ‘ current consumption habits, and to help Canadians make more informed decisions about Canadians who like to eat these types of fish can continue to eat them but should limit their consumption to the amounts listed in the following table. Other types of fish should be chosen to make up the remaining weekly fish consumption recommended for the following.

General Population – 150 g per week

Specified Women * – 150 g per month

Children 5-11 years old – 125 g per month

Children 1-4 years old – 75 g per month

Bioaccumulation of a Contaminant in Fish. Also concern in the sensitive group of people, specified women are those who are or may become pregnant or are breastfeeding. 150 grams represents two Food Guide servings and is equivalent to approximately one cup. The fish consumption advisories have different consumption recommendations in different fish.  This reduces the risk of mercury exposure in human health.

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