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 crops Runoff into aquatic ecosystems Through 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 chains Kills more organisms than just pests Health affects on humans: consuming foods which contain pesticides

POP’s Persistent Organic Pollutants (POP’s): “Dirty Dozen” Contain chlorine Insoluble in water and persist in fats and soil Banned use by the Stockholm Convention in 2004 Examples: DDT, chlordane, aldrin NR=1 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 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 ’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 Bioaccumulation Thinning of egg shells: Bald Eagle population Human Health: linked to increased cancer, diabetes, and other neurological conditions. This is still an issue today, as DDT is so persistant in the environment

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 tissue Most 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 pesticides Your textbook pages can help with the questions