In stratosphere, freon is able to initiate radical chain
reactions that can upset the natural ozone balance DDT, the first chlorinated organic insecticides, was originally prepared
in 1873, but it was not until 1939 that Paul Muller of Geigy
Pharmaceuticals in Switzerland discovered the effectiveness of DDT as
an insecticide Paul Muller was awarded the Nobel Prize in Medicine
and Physiology in 1948 for this discovery The use of DDT increased
enormously on a worldwide basis after World War II, primarily because
of its effectiveness against the mosquito that spreads malaria and lice
that carry typhus