DDT
DICHLORODIPHENYLTRICHLOROETHANE
What will we be learning in this PPT?
-What was it?
-Where was it used?
- Which food chain did DDT affect/How did it affect
our environment
-Why did it get banned?
The above shows an
WHAT IS DDT?
image Paul Herman
Muller
• DDT (dichloro-diphenyl-trichloroethane) was developed as the first of the modern synthetic insecticides in the 1940s.
It was initially used to fight malaria, typhus, and the other insect-borne human diseases among both military and
civilian populations. It also was effective for insect control in crop production, institutions, homes, and gardens. DDT's
quick success as a pesticide, broad use in the United States and other countries led to the development of resistance
by many insect pest species.
• Who invented DDT?
• . DDT has humble origins for a chemical that would eventually
reach much of the world. First discovered in 1873 by a German
chemistry student named Othmar Zeidler, the compound did
not receive serious attention until a 37-year-old chemist named
Paul Herman Muller synthesized it again in 1936.01
Low to moderate exposure (10mg/kg) may result in nausea,
diarrhea, irritation of eyes, nose or throat, while higher doses
(16mg/kg) can lead to tremors and convulsions. In experimental
animals, such as mice, rats, and dogs, DDT has shown to cause
chronic effects on the nervous system, liver, kidneys, and immune
system. It has also been found that humans, who were
occupationally exposed to DDT, suffered chromosomal damage.
What is Bioaccumulation?
Bioaccumulation occurs
WHICH FOOD CHAIN DID DDT AFFECT? when an organism absorbs
a substance at a rate faster
than that at which the
• DDT is an insecticide that can pass up the food chain from insects to small birds, and then from the small birds to birds of prey, like substance is lost or
hawks. It can accumulate in the birds of prey, giving them a large amount of DDT. High concentrations of DDT in birds cause weakness eliminated by excretion
in the shells of their eggs, which leads to a reduction in their population. DDT is now banned because of this.
• DDT's devastating effect on the aquatic environment has been thoroughly studied. Due to it's low solubility, it has a greater rate of
bioaccumulation in water, and thus poses a great long-term threat to aquatic wildlife. It's highly toxic to both aquatic invertebrate
species, like stoneflies and crayfish, as well as fish. Being able to affect all kinds of wildlife, and given it's low decay rate, it proliferates
through the entire web of life until it reaches the species inhabiting the throne of the great chain of life, Homo Sapiens.
After extensive exposure to soil, DDT will break down into two products, DDE and
DDD, with quite similar properties and the same highly persistent characteristics
as found in the original DDT. It is this metabolite known as DDE, which is thought
to be responsible for the eggshell thinning phenomenon observed birds. Studies
have been conducted in regard to this alarming issue, and a decrease in calcium in
the eggs laid by birds whose diet included small levels of DDT (100ppm) has been
shown.
PPM(Parts per Million)
Just as per cent means out of a hundred, so parts per million or ppm means out
of a million. Usually describes the concentration of something in water or soil.
One ppm is equivalent to 1 milligram of something per liter of water (mg/l) or 1
milligram of something per kilogram soil (mg/kg).
HOW DID DDT GET BANNED?
• The U.S. Department of Agriculture, the federal agency with responsibility for regulating pesticides
before the formation of the U.S. Environmental Protection Agency in 1970, began regulatory actions in
the late 1950s and 1960s to prohibit many of DDT's uses because of mounting evidence of the
pesticide's declining benefits and environmental and toxicological effects. The publication in 1962 of
Rachel Carson's Silent Spring stimulated widespread public concern over the dangers of improper
pesticide use and the need for better pesticide controls.
• In 1972, EPA issued a cancellation order for DDT based on its adverse environmental effects, such as
those to wildlife, as well as its potential human health risks. Since then, studies have continued, and a
relationship between DDT exposure and reproductive effects in humans is suspected, based on studies
in animals. In addition, some animals exposed to DDT in studies developed liver tumors. As a result,
today, DDT is classified as a probable human carcinogen by U.S. and international authorities.
Thank you!
I hope you understood and enjoyed my presentation!
