Pesticides First generation pesticides – found to be toxic to humans – polluted water and soil – NOT biodegradable (able to break down naturally) Second generation pesticides – generally man made organic chemicals – They were l ess toxic to humans – More biodegradable
some of these chemicals are fat soluble and become stored within animal tissues. This creates a problem known as bioaccumulation. Pesticides
Bioaccumulation Toxins and poisons begin to build up in living organisms. Toxins increase in concentration over time. The substance is taken in (ingested, absorbed or inhaled) and stored faster than it is broken down by the body
Examples: DDT (and other pesticides) Methyl Mercury (and other industrial pollution) Effects: Cancer and Birth Defects, Changes in body chemistry Bioaccumulation
An example… DDT Benefits – Low toxicity for humans – Highly effective against insects – Easy and cheap to manufacture Problems – Remains active in the environment for a long time – Causes shell thinning in birds and other reproductive problems Status – Banned for use in North America since the 1970’s – Still used in the 3 rd World to fight malaria (carried by mosquitoes) – Saves 1000’s of human lives each year
Biomagnification – process that results in the build-up of a chemical in an organism at higher levels than are found in its prey. – occurs when a chemical becomes more and more concentrated as it moves up a food chain – Eating contaminated food “magnifies” the effect of bioaccumulation.
Biomagnification – Tracking through the use of colored dots: Producers suffer from only bioaccumulation and receive one dot. Consumers suffer from both bioaccumulation and biomagnification and receive an extra dot for each increase in trophic level.
In Lake Ontario… mothers who consumed high amounts of Lake Ontario fish were found to have babies with poor reflexes and whose organs developed at a slower than normal level
YOUR TASK DDT Case Study- Read Article and Answer questions