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
• Bioaccumulation
• 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)
b)
c)
d)
DDT decreases along a food chain
Bioaccumulation of DDT occurs
Biomagnification of DDT occurs
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)
b)
c)
d)
DDT increases along a food chain
Bioaccumulation of DDT occurs
Biomagnification of DDT occurs
DDT was originally used in WWII to control
typhus
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