Bioaccumulation and Biomagnification

• Bioaccumulation• This is the way

materials become concentrated in the tissues of a living organism.

• Biomagnification• This is the way

substances become concentrated in living things as the substance moves through a food chain. (up trophic levels)

Bioaccumulation• This is the process by

which pollutants are absorbed and stored in living org’s.

• Chronic exposure over long periods may lead to bioaccumulation.

• Initial exposure may have been to concentrations too low to cause problems but accumulation of pollutant may result in poisoning

Bioaccumulation

• This is the process of the accumulation of materials in living things.

• Bioaccumulation occurs when the rate at which the material is absorbed and stored in the organism is faster than the rate at which it is removed. Removal may be through excretion or because of the breakdown of the substance.

Bioaccumulation cont’d• Liposoluble pollutants tend

to build up in lipid stores...• Water soluble pollutants

tend to be excreted more easily.

• Chlorinated organic compounds (eg organochlorine insecticides, dioxins and PCBs and heavy metals all bioaccumulate.

dioxin

Biomagnification • This is the concentration of

pollutants that bioaccumulate as a result of them passing up trophic levels.

• Pollutants that bioaccumulate in one organism are eaten by predators, and as large quantities of prey are eaten over a long time the pollutant becomes increasingly concentrated.

• The mercury concentration in the tissues of the tuna is....

• The more trophic levels there are in a food chain the.....

Biomagnification of DDT

Biomagnification• http://techalive.mtu.edu/meec/module02/FoodChain.html

Synergism • Substances act

synergistically when their combined affect is greater than the sum of their individual affects

• e.g. the synergy between oxides of nitrogen and sulphur dioxide

• Also their is a synergistic affect between zinc and cadmium

Mutagenicity • Substances or forms of

energy that cause changes to DNA are termed mutagens

• The effect of a mutagen depends not only on the extent of the damage to DNA but also depends on the type of cells that are affected

• PCBs, dioxins, asbestos and ionising radiation

Carcinogenicity

• Any substance that can cause cancer is termed a carcinogen.

• These are mutagens that affect normal tissue growth

• Cadmium, asbestos, DDT, carbon tetrachloride and many more!

Teratogenicity

• Teratogens are substances that can cause birth defects without altering DNA

• They work by disrupting normal development

• Mercury and the herbicide 2,4,5T are examples of pollutant teratogens