Pesticides

What ARE They?

Pesticides Pesticides are chemicals that kill unwanted

organisms, usually those that attack crops. Therefore, they are intended to help us by killing the species we don’t want.

They affect many processes of living things: GrowthGrowth Reproduction Reproduction Neurological DevelopmentNeurological Development Immune SystemImmune System

Why are they BAD for the environment?

Why are they BAD for the environment? They remain in the environment for a

long time, and often kill much more than what they are “intended” to kill

When humans first started to use pesticides

Bioaccumulation & Biomagnification

When substances (like pesticides) build up in an organism’s body throughout its lifetime, this is called bioaccumulation.

As we move up a food chain, a pesticide becomes more and more concentrated. This is known as biomagnification.

Biomagnification

When humans use pesticides, goes into abiotic components of the ecosystem (e.g. water, soil). It starts here in low concentration.

The producers that live in water or soil absorb these toxins into their bodies.

When the primary consumers eat the producers, they are also eating the toxins, and the toxins accumulate in their body.

Every trophic level has a higher concentration of toxins, making it fatal.

How do pesticides affect humans? As you have been learning throughout this

course, we are very connected to ecosystems. Think about the food we eat… how is it possible

that it contains toxins from pesticides? Video: http://youtu.be/aTm7i84mcMI Note that this video is from Europe, and they

have stricter rules about pesticide use that we do

DDT

DDT (dichlorodiphenyltrichloroethane) was a pesticide used in Canada and throughout the world up until 1970.

It was considered a miracle chemical because it killed insects that spread diseases and ruined crops. It was considered safe for humans because there were no short-term toxic effects

Therefore, it was applied to everything in mass quantities.

Dangers of DDT

In 1962, conservationist Rachel Carson wrote a book, Silent Spring, warning of the dangers of using pesticides such as DDT. She warned that pesticides kill species in ecosystems and would also affect human health.

Her book changed people’s attitudes towards the environment

Throughout the 1960’s, most people realized these dangers as DDT caused a huge amount of devastation because it would accumulate in top consumers

The peregrine Falcon almost became extinct because of DDT

Mallard Duck Eggs Affected by DDT

The DDT causes the eggs laid by many different birds to have soft shells that crack.

The baby birds then die before they hatch.

Consumption of DDT While microorganisms are While microorganisms are

affected by DDT, many tend to affected by DDT, many tend to keep it inside of them rather keep it inside of them rather than dying immediately than dying immediately ((bioaccumulationbioaccumulation))

This causes a chain reaction, This causes a chain reaction, up the food chains they are in up the food chains they are in ((biomagnificationbiomagnification))

Likewise, many small creatures Likewise, many small creatures on land (ex. Earthworms) can on land (ex. Earthworms) can accumulate DDT in their accumulate DDT in their systems, which is harmful to systems, which is harmful to predators that eat thempredators that eat them

Effects of DDT In birds, DDT causes the In birds, DDT causes the

thinning of eggshellsthinning of eggshells.. Humans can also Humans can also

accumulate DDT in their accumulate DDT in their bodies, where it is bodies, where it is stored in fatty organsstored in fatty organs and can be harmful to and can be harmful to bodily functionsbodily functions

ResultsResults: dizziness, : dizziness, seizures, respiratory illness, seizures, respiratory illness, and immune system and immune system dysfunctiondysfunction

The DDT ban

Since the 1970s, DDT was banned in North America. Since 2001, most other countries in the world agreed to ban it.

DDT is still used in some regions, such as Africa, to kill mosquitoes that spread the disease Malaria

Some argue that the Malaria kills more humans than the DDT, so they would rather be exposed to DDT. Therefore, they still use DDT, but in small quantities.

Banning DDT has been blamed for the increase of other insects too, such as bed bugs

Video: http://youtu.be/kyYpwOTtaLI

Considering the benefits of DDT, do you think it is justifiable to still use it?

Homework p. 80 #5 p. 85 #9, 10