DDT Case Study
DDT Case Study
DDT Case Study
South Africa stopped using DDT because of worries about high levels of DDT in
blood and breast milk in the population. They used other insecticides to control
the malarial mosquitoes instead of DDT. Unfortunately, the mosquitoes quickly
became resistant to these other insecticides. South Africa had to start using
DDT again to avoid large numbers of deaths from malaria.
QUESTIONS
2. When India started to use DDT to control malarial mosquitoes, the number of people
getting malaria fell from 75 million cases a year to 5 million cases a year. It fell by a
factor of 15. The number of deaths fell from 1 million to 5000 a year - a factor of 200.
Can you suggest any reasons why the number of deaths fell faster than the number of
people catching the disease?
3. Using chlorinated hydrocarbons like DDT resulted in a fall in numbers of some birds.
This was especially true of birds of prey like sparrowhawks and peregrine falcons.
Why do you think that these were particularly affected?
4. There is disagreement among scientists and others whether DDT should be banned
completely.
Make a list of the reasons why DDT should continue to be used, and a second list of
the reasons why it should be banned.
5. What do you think should be done about the use of DDT and the problem of
malaria?
Remember that the majority of countries which have a major malaria problem and still
use DDT are poor.
Explain your reasoning. (Answer on a separate sheet as an essay question)