As a typical example of bioaccumulation, an aquatic environment can be contaminated by certain organochlorines (DDT, PCBs, etc.) which are persistent substances. These persistent pollutants can be accumulated subsequently inside some small aquatic creatures in the same environment. As these contaminated creatures fall prey to carnivorous fish, birds, and larger species, the pollutant’s concentrations are progressively magnified in each of these predators. Thus, humans too may suffer detrimental health effects as a result of this bioaccumulation. Similarly, other ecosystems, such as soil, air, plants, and any of their combinations with or without water can provide an environment for bioaccumulation of these pollutants.

Not all environmental pollutants, including those capable of causing endocrine disruption, are prone to bioaccumulation. As expected, contaminants that are more stable in the environment are those having relatively longer half-lives (for definition see Slide 15). These pollutants are the ones tending to pose greater threat of bioaccumulation within an ecosystem. Posing even greater threat are those chemicals that are fairly resistant to metabolism once inside an organism. Chemicals that are lipophilic (fat soluble or fat-loving) can be stored in fat deposits for many years inside an organism. It is these persistent, stable, and lipophilic chemicals that are likely to be accumulated by animals and eventually by humans.

In general, chemicals that tend to move freely within an organism’s body, or to be excreted rapidly from the body, are less likely to be bioaccumulated. Thus, the accumulation would be more in an old trout than in a young yellow perch from the same lake, since the former is a relatively larger, fatter, and long-lived fish that has a lower rate of excreting a chemical.