DDT

DDT was the first synthetic pesticide of the

modern age. It promised much, but ultimately created widespread concern as an environmental hazard.

DDT: what is it?

DDT is one of nine persistent organic pollutants (POPs) DDT - originally World War II, control typhus which was spread by the body louse. 1955 – WHO – eradication plan for mosquito borne malaria Extensively used - general agricultural insecticide until 80s.

1950s - resistance problems 1960s - serious environmental problems Then: wide-ranging restrictions on its use Now: studies show environmental persistence bioaccumulation mimics hormones so disrupt endocrine systems in wildlife and possibly humans

Not soluble in water Soluble in lipids (fats) Builds up in fatty tissue Soil half life – 22 days to 30 years

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Bioaccumulation

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Biomagnification

Build up of non-biodegradable chemicals in body Concentration of non-biodegradable chemicals increasing at each trophic level

DDT led to decline of the bald eagle

Human health – disputed facts

Farmers – asthma and/or diabetes Exposed people - increased risk of some cancers - miscarriage, premature birth, low birth weight - Increased infertility in men

Malaria

Malaria

• • • • • 250 million cases each year 1 million deaths a year 90% of deaths in Africa 2006 – 13 countries still using it Many aid agencies won’t give aid if a country uses DDT

The ban

1970s and 80s – banned in most MEDCs USA – 1972 UK – 1984 Worldwide ban on agricultural use in the Stockholm Convention India and N Korea still use it for agriculture

Write down the true statements and change the false ones to make them true a) DDT decreases along a food chain b) Bioaccumulation of DDT occurs c) Biomagnification of DDT occurs d) DDT was originally used in WW1 to control cholera e) DDT was used on farms to kill rats

f) DDT was used to kill mosquitoes g) Pests became resistant to DDT h) Water small fish zooplankton large fish eagles fish-eating birds i) Babies get asthma and / or diabetes j) Exposed people suffer cancer and pregnancy/birth problems.

k) Malaria affects 1 million people a year

m) In 2000 it was banned in most MEDCs n) The Oslo Convention stopped its use in agriculture worldwide.

The answers a) DDT in creases along a food chain b) Bioaccumulation of DDT occurs c) Biomagnification of DDT occurs d) DDT was originally used in WW II typhus to control e) DDT was used on farms to kill pests

f) DDT was used to kill mosquitoes g) Pests became resistant to DDT h) Water zooplankton small fish large fish fish-eating birds eagles i) Farmers get asthma and / or diabetes j) Exposed people suffer cancer and pregnancy/birth problems.

k) Malaria affects 250 million people a year

m) In 1970s/80s it was banned in most MEDCs n) The Stockholm Convention stopped its use in agriculture worldwide.

IB: Evaluate the advantages and disadvantages to ecosystems and societies of banning the pesticide DDT. [10] Evaluate: make an appraisal by weighing up the strengths and limitations

a) Outline the main uses (past and present) of DDT. (3) b) Describe the variations in the level of DDT along a food chain. (3) c) Comment on the risks of using DDT. (4) • • • Describe: give a detailed account Outline: give a brief account or summary Comment on: give a judgement based on a given statement IB: Evaluate the advantages and disadvantages to ecosystems and societies of banning the pesticide DDT. [10] Evaluate: make an appraisal by weighing up the strengths and limitations

Describe: give a detailed account Outline: give a brief account or summary Comment on: give a judgement based on a given statement Evaluate: make an appraisal by weighing up the strengths and limitations