|MadSci Network: Environment & Ecology|
Brandi, You ask if certain chemicals can cause problems with animals if they eat plants or animals that that have been treated with these products. The answer is definitly YES. The most famous example is that of DDT. DDT was used extensivly in the 1950's as a pesticide. It effectivly killed mosquitos and other pest insects. The trouble was that the DDT would then get into the food chain( or web). Imagine an insect gets sprayed with DDT, the insect then lands on a lake. A fish in the lake eats the insect ( actually many, many insects). This fish gets eaten by a larger fish, who then gets eaten by an eagle. An eagle is a large, meat eating bird called a Raptor. After so many steps in the Foodchain the eagle ( who now sits at the top of the chain) gets a lot of the DDT ( a process called BIOACUMULATION). DDT effects the bird by interfering with calcium absorbption. Which means the eagle can not use the calcium in its body. Remember that bird lay eggs, and an important part of the egg is calcium. It is the calcium that makes the egg hard. When a mother eagle sits on her eggs to keep them warm the egg need to be hard enough to support her weight. If the egg does not have enough calcium, when the eagle tries to incubate the egg, it will crack and the baby will die. Thus, if to much DDT gets into the environment many types of birds will not be able to have surviving offspring. An this is exactly what happened in the 1950's- 1970's . Many types of birds almost went extict because of the use of DDT. When this chemical was banned these species began to recover. Another problem with chemcials like DDT is that they do not brake down very fast. They stay in the environment for many years. Even though DDT has not been used in the United States for almost 30 years we can still find it in the environment so it still possible that it may be causing wildlife problems. If you would like to know more about this subject there is a famous book by Rachel Carson called "Silent Spring". This book is credited with starting the environmental movement in the USA and is must read for anyone interested in the subject. Good luck on your project! Steven Korenstein Environmental Health Specialist
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