Bioaccumulation of Persistent Chemicals and Microplastics in Fish
By Pierre Mouchette | Bits-n-Pieces
How Does Bioaccumulation in Fish Happen?
Bioaccumulation in fish happens when:
Persistent Organic Pollutants Examples
Persistent chemicals are very stable chemicals that do not break down over time. Chemicals such as PCBs, DDT, dioxins, and mercury are all persistent chemicals. Because chemicals like these do not break down and go away, it becomes a problem with the fish or wildlife because they will build up in their system. The chemicals will be stored and bioaccumulated if you eat the fish or wildlife, which can lead over time to health problems.
The problem is not the fish. The toxic chemicals like mercury and other toxins injected into the air, water, and land end up in the fish we eat. Mercury is extremely bad for consumption and is found in different fish that scientists have identified as having more risk than others. Even though the EPA and other governing agencies have done an excellent job at eliminating the source of heavy metals like mercury from the environment, the persistent chemicals that entered the ecosystem years before remain and will be there for a long time.
How Does Mercury Get Into the Water
We have known for a while that mercury is the heavy metal that impacts fish the most. Fish in oceans, rivers, and bays are exposed to it. It is not just mercury but a host of chemicals and even microplastics found in fish muscles and livers. These plastics and chemicals are bioaccumulated into the fish over time. Information on testing for microplastics and chemical pollutants build up in fish over time is a new type of science. However, we know that microplastics act like sponges for other chemicals that can be absorbed into the fish and passed on through the food chain once they get inside aquatic life, from the smaller to the more significant species that live longer and absorb more toxins. Our oceans and rivers have been a toilet for a long time, and time has caught up.
Scientists know the risk of chemicals moving up the food chain as predators eat the smaller fish, and we eat the predator species. It is why the fattest and largest fish, like Tuna and Swordfish, end up with the most mercury and PCBs (polychlorinated biphenyls) and other toxins that are not as easy to measure as mercury. It is concerning, as Tuna is the most consumed fish from the ocean by people in the US.
Mercury comes from a broad spectrum of industries throughout the world. The burning of coal is the largest single anthropogenic source of mercury air emissions, having more than tripled since 1970. And coal burning for power generation is increasing alongside economic growth. Emission releases from power plants and industrial boilers represent today roughly a quarter of mercury released into the atmosphere. Household burning of coal is also a significant source of mercury emissions and a human health hazard. Although coal contains only tiny concentrations of mercury, it is burnt in huge volumes and has been for many years globally.
The Good News
From studies to date, we know that up to 95% of mercury released from power plants can be reduced. It can be achieved by improving coal and plant performance and optimizing control systems for other pollutants. The bad news is that mercury, like PCPs and many others, is regarded as a persistent chemical that will not break down for years. And yes, there is plastic!
Identifying and stopping the source is a great thing. However, the contaminants that are already in the sediments of lakes, rivers, and oceans will continue to enter the smallest of macroinvertebrates that minnows will eat up, which will be eaten by the more significant, older predatory aquatic fish or wildlife that humans will consume at the top of the food chain. That is Bioaccumulation in Action.
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