Bio-Magnification

Biomagnification, also known as bioamplification or biological magnification, is the increasing concentration of a substance, such as a toxic chemical, in the tissues of organisms at successively higher levels in a food chain. 

This increase can occur as a result of:

• Persistence – where the substance cannot be broken down by environmental processes
• Food chain energetics – where the substance's concentration increases progressively as it moves up a food chain
• Low or non-existent rate of internal degradation or excretion of the substance – often due to water-insolubility

There is a concern about these phenomena because together they mean that even small concentrations of chemicals in the environment can find their way into organisms in high enough dosages to cause problems.

• Biological magnification often refers to the process whereby certain substances such as pesticides or heavy metals move up the food chain, work their way into rivers or lakes, and are eaten by aquatic organisms such as fish, which in turn are eaten by large birds, animals or humans. 

The substances become concentrated in tissues or internal organs as they move up the chain. 

• Bioaccumulants are substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted.

In order for bio-magnification to occur, the pollutant must be:

1. Long-lived
2. Mobile
3. Soluble in fats
4. Biologically active

• If a pollutant is short-lived, it will be broken down before it can become dangerous.
• If it is not mobile, it will stay in one place and is unlikely to be taken up by organisms.
• If the pollutant is soluble in water it will be excreted by the organism. 
• Pollutants that dissolve in fats, however, may be retained for a long time. It is traditional to measure the amount of pollutants in fatty tissues of organisms such as fish. 
• In mammals, we often test the milk produced by females, since the milk has a lot of fat in it and because the very young are often more susceptible to damage from toxins (poisons).