Bioaccumulation

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.

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.

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.

Ways to counter effects. DDT was banned in the 60’s 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.