SCIENCE 10 O2

Pesticides and DDT

What are Pesticides?

PESTICIDES: chemicals that are designed to kill pests.

PEST: any organism that people consider harmful or inconvenient.

As much as 30% of the annual crop in Canada is lost to pests (weeds, insects, birds, fungi, and small animals)

Can you think of some uses for pesticides?

Pesticide Uses

Most common industrial uses are in forestry and agriculture

Pesticides are used to: Control pest borne diseases such as malaria In agriculture for control of pests on crops Added to shampoo, carpets, mattresses, paints

Types of Pesticides

There are four main types:

INSECTICIDE: targeting insects

HERBICIDE: targeting weeds and invasive plants

FUNGICIDE: targeting fungi such as mould

BACTERICIDES: targets bacteria

How do pesticides enter the environment?

Through spraying on cropsRunoff into aquatic ecosystemsThrough consuming organisms that have fed

on affected areas

Benefits of Pesticide Use

Helps to control pests and increase crop yields

Can help reduce the transmission of diseases such as malaria

Downfalls to Pesticide Use

Enters into food chainsKills more organisms than just pestsHealth affects on humans: consuming foods

which contain pesticides

POP’s

Persistent Organic Pollutants (POP’s):“Dirty Dozen”Contain chlorineInsoluble in water and persist in fats and soil Banned use by the Stockholm Convention in

2004Examples: DDT, chlordane, aldrin

http://www.youtube.com/watch?v=vJoyx_PDAS0&NR=1

DDT: dichlorodiphenyltrichloroethane

One of 12 POP’s

Is an organochlorine (is organic and contains chlorine in structure)

Hydrophobic (water hating) and insoluble in water

Soluble in fats and oils Why is this bad?

Demonstration!!

Uses of DDT

Widely used in World War II to fight against malaria and typhus in troops

In 1955 the World Health Organization relied on DDT to eradicate (get rid of) malaria worldwide

From 1950-1980 it was heavily used as a pesticide (insecticide) in agriculture

Ban of DDT

In 1962 Rachel Carson published the book “Silent Spring” which outlined the environmental impacts that spraying DDT had on environment

Agricultural use was banned in the US in 1972, and most other countries in the 1970-80’s, but agriculture still continues in India and North Korea

Vector control use (against diseases) has not been banned.

The Stockholm Convention: outlawed several POP’s, including DDT.

Environmental and Human Impacts

BioaccumulationThinning of egg shells: Bald Eagle populationHuman Health: linked to increased cancer,

diabetes, and other neurological conditions.This is still an issue today, as DDT is so

persistant in the environment http://www.youtube.com/watch?v=Foy5Eav8cDg

Bioaccumulation

When pesticides contain chlorine, such as DDT, they are soluble in fat but not water

Because they are not soluble in water, they cannot be released from the body through sweat or urine

Instead, they accumulate (build up) in the fatty tissue of animals

At each stage of the food chain, the pesticide concentration increases.

The higher the trophic level, the greater the concentration of pesticide toxins or poisons.

This build up is called bioaccumulation.

Improved Pesticides

Modern pesticides are not stored in fat tissueMost are soluble in water. Why is this

important?These new pesticides act like a nerve gas,

affecting muscle activity.These are safer than old pesticides but still

have some drawbacks: Break down faster and must be applied more often Do not target only one single organism, but many Bioaccumulation can still occur Insects can build up resistance

Task

Complete the activity sheet on pesticidesYour textbook pages 34-37 can help with the

questions