It is widely acknowledged that the most common form of exposure to mercury occurs through the consumption of fish and seafood products contaminated with high levels of mercury. The biological processes from which fish become contaminated with mercury are known as bioaccumulation, and biomagnification.
Bioaccumulation is concerned with the steady accumulation of certain chemicals within a living organism, in this case fish. This usually occurs through the ingestion of contaminated food, or from exposure to contaminated water sources, and due to the composition of those chemicals, are very difficult to eliminate or metabolise. Biomagnification refers to the increase in concentration of a chemical compound in an organism, as the result of the bioaccumulation of said chemical in organisms belonging lower in the food chain.
The processes of bioaccumulation
and biomagnification.
For example, let's say a chemical refinery releases mercury into a water source, and as a result, the water’s concentration of mercury rises. The kelp in that water feeds off and absorbs the micronutrients found in the water, and in the process absorbs the higher level of mercury. Small fish that feed on the kelp subsequently begin to accumulate higher levels of mercury in their bodies. Larger predatory fish eat many of those small fish, and therefore accumulate much higher concentrations of mercury. This process continues up the food chain, with large predators such as sharks, tuna, swordfish, seals and sea birds receiving the highest doses of mercury. Due to humans’ preference for the harvesting of larger, predatory type species of fish such as tuna, we also receive fairly large concentrations of mercury in the fish that we consume