Over the last 60 years farmers and growers have changed the way they produce food in order to meet the expectations of consumers, supermarkets and Governments. In doing so they have made many changes to the way they farm. This often includes the use of

1
Introduction

• Over the last 60 years farmers and growers have
  changed the way they produce food in order to
  meet the expectations of consumers, supermarkets
  and Governments. In doing so they have made many
  changes to the way they farm. This often includes
  the use of pesticides.

2
What is a pesticide?

• A pesticide is any substance or mixture of
  substances intended for preventing, destroying,
  repelling, or mitigating any pest.
• Under United States law, a pesticide is also any
  substance or mixture of substances intended for
  use as a plant regulator.

3
What is a pest?

• Pests are living organisms that occur where they
  are not wanted or that cause damage to crops or
  humans or other animals. Examples include
• insects
• mice and other animals
• unwanted plants (weeds)
• fungi
• microorganisms such as bacteria and viruses

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Types of Pesticides

• Common misunderstood to refer only to
  insecticides, the term pesticide also applies to
  herbicides and fungicides. Pesticide use is now
  common practice worldwide.
• Herbicides control weeds.
• Insecticides control insects.
• Fungicides control diseased crops.

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Household Products- Pesticides

• Many household products are pesticides. For
  example
• Cockroach sprays
• Insect repellents for personal use
• Rat poisons
• Kitchen, laundry, and bath
• disinfectants and sanitizers
• Products that kill mold
• Some swimming pool chemicals.

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Benefits / Risks

• Pesticides can cause harm to humans, animals, or
  the environment because they are designed to kill
  or otherwise adversely affect living organisms.
• At the same time, pesticides are useful to
  society - can kill potential disease-causing
  organisms and control insects, weeds, and other
  pests.

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Other Risks

• Pesticides are among the most widely used
  chemicals in the world, and also among the most
  dangerous to human health
• Cancer
• Neurological damage
• Miscarriage

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Introduction DDT

• When people hear the word, "pesticides," they
  often associate it with something very negative.
  And many times, they'll soon think of DDT.
• DDT is one of the most famous pesticides in the
  world, and it has been with us for quite a long
  time.
• It was first made in a laboratory in 1873, but it
  was not until 1939 that Paul Muller of Geigy
  Pharmaceutical in Switzerland discovered the
  effectiveness of DDT as an insecticide.

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Chemical DDT
DDT stands for dichloro, diphenyl
trichloroethane. It is a chlorinated
hydrocarbon. DDT is a chemical used mainly as a
pesticide. DDT was one of the most widely used
chemicals for controlling insect pests on
agricultural crops.
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Chemical DDT
Ingestion and other exposures to the chemical can
cause various symptoms. The chemical may be
absorbed through the skin. The type and severity
of symptoms varies depending on the amount of
chemical involved and the nature of the exposure.
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Symptoms

• Skin irritation
• Eye irritation
• Anxiety
• Dizziness

Headache Weakness Fatigue Nausea
Vomiting
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DDT Effects
So far, we have learned that DDT is an extremely
persistent chemical. It gets into the fats of
organisms, and it stays there. Even small
amounts of DDT can affect small microorganisms.
This is especially true for microorganisms that
live in the water. As an example of this high
sensitivity, water that contains only 0.1 gram of
DDT per liter can slow down growth and
photosynthesis in green algae.
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History

• As a pesticide, DDT was first used during WWII.
  It was so effective as an insect killer that some
  called it the "atomic bomb" of pesticides.
• After WWII, we realized that DDT could also be
  used on farms to control some common agricultural
  pests.

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Real Life Situation

• DDT and malaria
• It was found to be particularly effective against
  insects which carry disease - especially the
  mosquitoes which carry malaria.
• Even today, every year 300 million people catch
  malaria and more than a million of them die.
  Using DDT to kill the mosquitoes has almost
  eliminated malaria from more than 20 countries
  with a total population of more than a billion
  people. The effect of using DDT is well
  illustrated by the example of India. Before the
  use of DDT, there were more than 75 million cases
  of malaria every year, and about a million
  deaths. Using DDT has reduced this to 5 million
  cases a year, and only 5000 of these result in
  death.

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The environmental case against DDT

• In 1962 an important book was published called
  "Silent Spring" by Rachel Carson. The name
• came from a worrying fall in the numbers of some
  birds. This was found to be caused by
• pesticides like DDT which are only broken down
  very slowly in the body or in the soil. They are
• described as "persistent organic pesticides" or
  POPs.
• DDT has now been found all over theworld, even in
  the Arctic - far from where it was used.
• DDT is a chlorinated hydrocarbon. These are very
  stable and are stored in body fat. Animals
• and birds can accumulate more DDT from the food
  chain faster than they can get rid of the DDT
• they already have in their bodies. The levels of
  DDT in the body increase over time. One of the
• effects of this in birds is that it causes them
  to lay eggs with very thin shells. These break
• easily before the eggs can hatch.

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The environmental case against DDT

• Animal studies using rats and mice have shown
  some harmful effects of DDT including a
• possible link with cancer and possible effects on
  the immune system and the reproductive
• System.
• On the other hand there is no definite proof of
  any harmful effects on humans although DDT has
• been found in human blood and breast milk. This
  is despite the fact that millions (or even
• billions) of people have been exposed to it over
  long periods of time. Some studies have shown
• that there may be effects on human development.
  Exposure may result in low birth weights or
• reduced heights in children.

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The environmental case against DDT

• 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.

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Questions

• Questions
• 1. DDT is a chlorinated hydrocarbon. What do you
  understand by this term?
• 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. Thenumber of deaths fell
  from 1 million to 5000 a year. 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
  sparrow, hawks 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.