A3.5 Bio-accumulation


Bioaccumulation is a general term for the accumulation of substances, such as pesticides in an organism. The accumulation process involves the biological sequestering of substances that enter the organism, for example through respiration, food intake, or skin contact with the substance. The sequestering results in the organism having a higher concentration of the substance than the concentration in the organism’s surrounding environment.

The level of bio-accumulation depends upon the following factors:

  • Solubility of the substance.
  • Rate of uptake.
  • Method of uptake (contact, ingestion etc).
  • Speed that the substance is eliminated from the organism.
  • Transformation of the substance by metabolic processes.
  • Fat (lipid) content of the organism.


A well known example of a substance that bio-accumulates is DDT (dichlorodiphenyltrichloroethane). This was an insecticide that was commonly used until it was found to bio-accumulate at every level of the food chain, after being washed off land into watercourses. High levels were found in birds of Prey, where an effect was that the egg shells produced were abnormally thin. This resulted in the adult birds accidentally breaking the egg shells and their un-hatched offspring died. The use of DDT was banned in the UK and USA during the 1970’s. However, it is still used today in some countries for the control of malaria.

As knowledge increases regarding the bio-accumulation of different substances, legislation is put in place to control the use, disposal and discharge of such substances.