Fish is the cold-blooded vertebrate with gills and fins and resides in the water. From a nutritious point of view, the fish contains protein and less fat and is an excellent source of omega-3 fatty acids.

These constituents play a crucial role in our health development, such as brain development, reducing blood pressure and cancer. It is the energy source and boosts immunity power once consumed with a healthy diet.

In the present context, fish contamination has been considered a crucial global issue. Even the developed countries are facing fish contamination issues frequently.

Table of Contents

Fish contamination

Be careful while eating fish. Copyright: Consumer Reports

In general, while we talk about fish contamination, we understand the consumption of the fish that absorb Polychlorinated Biphenyl (PCBs), DDT (Dichloro Diphenyl TrichloroEthane) dioxins, and chlorinated pesticides.

The fish contaminates water with methylmercury. A fisherman uses various techniques and chemicals to kill the fish in a large amount. There is the practice of using the trap net having a high voltage of current. Once the chemicals are ingested into the fish’s body, they are contaminated with several substances.

We suffer from contamination when we consume the same fish contaminated with chemicals. The current generation is going through urbanization and industrialization. Due to the unmanaged and haphazard industrialization without the pre-treatment, the industries and many factories are discharging the chemicals.

Once they enter the various water bodies, the chemicals settle as sediments. Once the fish consumes them, it affects the fish species and impacts human health once the human consumes the fish species.

The contamination accumulates as the species reach the food chain in the upper level by bioaccumulation, which means the accumulation of mercury in the organisms for a long time. The bottom-dwelling fish suffers from mercury contamination.

Another important term to know is biomagnification. Biomagnification refers to transferring chemicals from one trophic level to another within a food web. The fish that reaches the top of the food chain possess methyl mercury 1 to 10 million times greater than the fish in the surrounding water.

The exposure to the pollutants can be long-term or short-term based on the type and the amount of the contaminants. Various fish contaminants have been identified, including methyl mercury, arsenic, hexavalent chromium, dioxins, and Polychlorinated Biphenyls (PCBs).

Effects of the fish contamination on our health

Even Birds are not safe. Copyright: ABC Action News

Numerous research has insisted that it takes five or more years for childbearing women to get rid of the chemicals such as Polychlorinated Biphenyl (PCBs) and approximately 6 to 12 months to reduce the effects of the mercury.

Since most contaminants exist for a prolonged period in the atmosphere and human lives, it doesn’t seem easy to eliminate such pollutants from the body parts. It has been found that the fetus and the newborn baby who possess mercury in their body have difficulty learning.

Due to the high chance of mercury effects on the children, it may entirely affect the central nervous system and the cardiovascular system.

Moreover, polychlorinated biphenyl can alter the human liver and the blood. Pregnant women feel difficulty in pre-pregnancy and the post-pregnancy phases.

Incident of Minamata Bay regarding the fish contamination

Once the organic mercury accumulated in the fish had been a public health issue in Minamata Bay of Japan, most adults were hospitalized, and some died.

After the medical investigation, the primary cause revealed was they had consumed the fish products from the Bay of the Pacific. The fish consumption contaminated with organic methyl mercury caused 600 deaths, and 3000 sick people were hospitalized.

The medical investigation further illustrated that the vapours of mercury metals are very toxic. Once it gets ingested into the human body, we cannot pass it from the digestive system. This incident reveals that the fish consumed by the people were highly contaminated with methylmercury, severely impacting human health.

The abundance of mercury was from the industrial effluents of the factory that produced the acetic acid introduced to the river, increasing the concentration of the methylmercury. Upon the sedimentation, it entered the fish.

Once the people consumed the fish contaminated with methylmercury, all reported symptoms and signs related to the severe toxicity. It caused brain damage, paralysis, and delirium.

It was a significant health issue; the disease identification remained unknown for an extended period. After many years, they identified the disease due to methyl mercury contamination in the fish products. 

Harmful Contaminations in Fish

1. Polychlorinated Biphenyl

PCB level may increase from 2000 to 1000000 times greater than the original level in the surrounding water.

Once the fish is contaminated with PCB and when we consume it, it may slow the immune system, thyroid, and kidney problems, increasing the chance of cancer. Since it bioaccumulates in the body for the long term, the impacts caused by it remain for a prolonged period. 

Consuming fish with volatile organic compounds may increase the chance of cancer in humans and animals. Therefore, we should check the persistent contaminants within the body parts and follow the medical suggestions in time.

2. Chlordane

Unforeseen effects have been visualized regarding the fish contamination. The contaminants of the fish have already devastated the ecosystem, thereby persisting for the long term in the environment.

The chlordane accumulated in the fish remains in the food supply for a prolonged time. Because in the past, they primarily used it in agriculture. 

Long-term persistence in the environment may cause digestive and nervous system disorders, infants’ behavioural disorders before birth and during the nursing time, cancer, and many more. The contaminants such as toxaphene, Aldrin, and dieldrin can have detrimental effects on our health.

3. Dieldrin and Aldrin

Dieldrin is one of the pesticides used heavily in the agricultural field. Consuming the fish containing dieldrin and Aldrin increases the infant mortality rate, lowering the human reproductive capacity and causing congenital disabilities that affect the kidney working system and may even lead to cancer in the coming days. Dioxin has been recorded in the surface water, lakes, and soils.  

4. Dioxins

The significant health effects caused by the dioxin accumulated in fish and the same fish consumption cause severe skin disease with acne-like lesions, thereby resulting in skin discolouration, excessive body hair, and weakening of our body’s immune system.

Moreover, the effects of dioxins on human health entail disrupting the endocrine system and increasing the chance of cancer.

5. Mercury

Mercury level - Fish contamination
Fishes species and their mercury level (source)

Mercury and the associated compounds are considered the top 10 chemicals by the World Health Organization, which have serious public health concerns.

Regarding mercury, the health impacts are determined by several factors such as the dose, type of the mercury, duration of the mercury exposure, route of the direction, which entails ingestion, inhalation and the dermal contact, developmental stage of the person being exposed, and many more.

These may affect the children’s neurological development, fine motor, spatial skills, and languages. Regarding mercury contamination, kidney problems have been identified with the issue of increasing protein in the urine to kidney failure. The gastrointestinal tract may be affected highly.

Despite the Minamata convention in 2013, it has been observed that there is no control in releasing mercury into the atmosphere even today. The political instability and the lack of implementation of the set regulations seem on the frontline.

The convention and World Health Organization (WHO) had aligned to stop the mercury level in the water bodies and the less consumption and use of the mercury-related products.

The areas with high fish contamination reflect the current or past discharge of the industrial effluents from many factories and industries.

The mercury flows to the water through atmospheric deposition, including volcanic eruption or the incineration of hazardous wastes. It gets persistent in the atmosphere, either in aquatic bodies or others, through leaking or any means.


Fish contamination is not a minor issue. Once persistent in the environment through passing several mediums, it can negatively influence the whole ecosystem. Among the various contaminants of the fish, methylmercury and Polychlorinated Biphenyl are the most serious, which have detrimental effects on human lives.

The bioaccumulation and biomagnification process makes us realize how the fish contaminants have persisted in our bodies for a prolonged time. Therefore, to critically halt the severe contamination, the industries should discharge the effluents after the proper treatment, ensuring safe marine bodies.

(Last Updated on June 27, 2022 by Sadrish Dabadi)

Kalpana Ghimire holds a post-graduate degree in Environmental Science from Nepal. She possesses numerous research experiences working in water pollution, community forestry, environment conservation status, and wildlife ecology. She was an internee in the Department of Environment (EIA monitoring and auditing section) under the Government of Nepal. Kalpana Ghimire is an avid traveler, an enthusiastic wildlife researcher, and has a huge passion for working in the environment sector. She loves far traveling to the natural areas, conducting field wildlife research and reading the novels.