Persistent Organic Pollutants (POPs) are chemicals that break down very slowly and can remain in the environment for years, even decades. POPs are introduced into the environment as pesticides, industrial chemicals, or as byproducts of industry.

Some examples of POPs include:

Pesticides: DDT, chlordane, aldrin, dieldrin, Industrial chemicals: PCBs
Industrial byproducts: dioxins and furans

All POPs share some common characteristics. They are easily carried by wind and can be transported to places far away from the original site. This means that plants and animals that are distant from places where these chemicals are used can be affected by them. POPs tend to concentrate in colder climates as they travel the globe, even though they are introduced in temperate and tropical climates.

POPs also have a low solubility in water and high solubility in fat. You may have seen news stories about how difficult it is to clean up an oil spill in the ocean. Because POPs have a low solubility in water, it is also difficult to wash these chemicals out of the environment.

However, POPs have a high solubility in fat. This means that if an animal gets some POPs in its body, the chemical will be stored in the animal's fat. POPs do not leave the body easily because bodily fluids like blood and urine have a high water content, and remember, POPs have a low solubility in water.

Because POPs are soluble in fat, they can build up in the fatty tissues of animals. This build-up of a chemical over time is called bioaccumulation.

Read more about bioaccumulation.