What is Bioaccumulation?

The Fish Model: How Mercury Ends Up in Our Food
The gradual accumulation of toxic substances such as plastic, pesticide, or other chemicals in an oraganism is known as the Bioaccumulation. This happens when an organism consumes or absorbs a toxic substance at a greater rate than excretion. The greater the toxic substance stays in the body, the greater is the risk of poisoning.

The bioaccumulation is one of the factors used to determine the environmental impact of a substance. A substance with higher tendency towards bioaccumulation cause a greater hazard. Moreover, when a substance bioaccumulates at each step of the food chain, it multiplies. One can understand this phenomenon through the fish model.

The Fish Model
1. The substance enters the water body.
2. The substance sinks to the bottom of the water body.
3. Small creatures known as macroinvertebrates eat these toxic substances as they dig in the sendiment for food.
4. The macroinvertebrates are then eaten by minnows; minnows are in turn eaten by small or medium fish, and then they are eaten by large fishes, at each stage magnifying the bioaccumulated substance.
5. Similarly when these fishes are eaten by humans, they end up in our bodies.

Common Bioaccumulating Pollutants and Their Areas in Human

PollutantTarget Area
Leadbone, teeth, nervous system
Mercurynervous system
Organochlorine pesticidesfatty tissue, breast milk
Microplasticslymphatic system, liver

However, some organism show bioaccumulation as the defence mechanism by consuming toxic plants and animals. One such example is Tabacco Hornworm who bioaccumlates the nicotine to the toxic levels by consuming tabacco.

Image Source: MERC Vermont

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