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 persistencebioaccumulationmimics hormones so disrupt endocrine systems in wildlife and possibly humans

Not soluble in waterSoluble in lipids (fats)Builds up in fatty tissue

Soil half life – 22 days to 30 years

Build up of non-biodegradable chemicals in body

Concentration of non-biodegradable chemicals increasing at each trophic level

• Bioaccumulation

• Biomagnification

DDT led to decline of the bald eagle

Human health – disputed facts

Farmers – asthma and/or diabetesExposed 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 MEDCsUSA – 1972UK – 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 chainb) Bioaccumulation of DDT occursc) Biomagnification of DDT occursd) DDT was originally used in WW1 to control

cholerae) DDT was used on farms to kill rats

f) DDT was used to kill mosquitoesg) Pests became resistant to DDTh) Water small fish zooplankton large fish eagles fish-eating birdsi) Babies get asthma and / or diabetesj) Exposed people suffer cancer and pregnancy/birth problems.k) Malaria affects 1 million people a year

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

The answers

a) DDT increases along a food chainb) Bioaccumulation of DDT occursc) Biomagnification of DDT occursd) DDT was originally used in WWII to control

typhuse) DDT was used on farms to kill pests

f) DDT was used to kill mosquitoesg) Pests became resistant to DDTh) Water zooplankton small fish large fish fish-eating birds eagles i) Farmers get asthma and / or diabetesj) 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 MEDCsn) The Stockholm Convention stopped its use in agriculture worldwide.

Evaluate: make an appraisal by weighing up the strengths and limitations

IB: Evaluate the advantages and disadvantages to ecosystems and societies of banning the pesticide DDT. [10]

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 accountOutline: give a brief account or summaryComment on: give a judgement based on a given statementEvaluate: make an appraisal by weighing up the strengths and limitations