Bioaccumulation

1
Bioaccumulation
2
Principles

• Non-biodegradable pesticides are taken up into
  environments and food chains and stored in fatty
  tissues.
• As these chemicals move through the food chain
  there concentrations increase in the creatures
  increase. This process is bio magnification.
• When the chemicals reach a tertiary consumer or
  higher in a food chain they reach toxic levels
  and so effect the live cycles of animals.
• This is mainly seen with birds in the thinning of
  bird shells or the premature hatching of eggs. Or
  in extreme cases the the levels of toxins
  increasing to fatal levels.
• The most well documented example of this is DDT.

3
Consequences of DDT

• 0.1 µg (micrograms) of DDT per litre can slow
  down growth and photosynthesis in green algae.
• Molluscs retain a lot of the DDT in their bodies
  this makes it dangerous for those predators who
  eat these organisms.
• Some problems associated with DDT include
  reproductive/development impairment and nervous
  system disorders.
• In fish DDT interferes with the plasma membrane
  where many important reactions occur.

4
Consequences of DDT

• In birds DDT causes the thinning of eggshells
  this is caused by interferences with enzymes
  involved with reproduction.
• Some species affected by DDT osprey eagles,
  pelicans, falcons and hawks
• When DDT gets into our bodies, it is stored
  primarily in such fatty organs as the adrenals,
  testes, and thyroid. DDT is also stored in
  smaller concentrations in the liver and kidneys.
• Concentration of 6-10 mg/kg leads to such
  symptoms as headache, nausea, vomiting,
  confusion, and tremors.

5
Ways to counter effects.

• DDT was banned in the 60s to prevent further
  accumulation of chemicals. The most obvious
  effect of which has been increasing levels of
  peregrine falcons from near extinction due to
  increased shell strength.
• Use of biodegradable pesticides prevents build up
  within organisms, despite being more expensive to
  produce and often less effect due to a short
  shelf lives.
• Restrictions are in place for non-biodegradable
  pesticides but this is often ignored in
  developing countries trying to increase yield so
  chemicals are still entering food chains.