Pesticides what makes a good one? Hazardous Chemicals. Arguments for Pesticides. Why Use them? DDT The beginnings of the Environmental Movement

Transcription

1 Pesticides what makes a good one? Hazardous Chemicals With Special Emphasis on Persistent organic compounds Kills only target Has no effects on non-target organisms Degrades in appropriate time span Will not produce resistance in target Saves money Why Use them? Agroecosystems are simplified No webs of interactions Our crops have lots of predators and competitors Arguments for Pesticides Save lives Increase food supplies Increase farm profits Faster and better than alternatives Arguments Against Pesticides Evolution of resistance Mobility and biotic accumulations Threats to Wildlife Short term threats to human life Farm workers Long-term effects of low-level exposure Residues in food DDT The beginnings of the Environmental Movement Chlorinated hydrocarbon worst of the worst Highly persistent Fat soluble Developed during WWII Wide use Lice control Mosquito control

2 Problems with DDT Widespread spraying for insects People noticed losses of wildlife Rachel Carson Government Scientist Noticed the problem Wrote Book Silent Spring Bioaccumulation DDT is fat soluble Accumulates UP the food chain Very persistent Bacteria don t work very well on it It is a totally new and human-made compound The Effects of DDT Wildlife biologists noticed that predatory birds were dying Poor reproduction Thin egg shells Kinds of birds Osprey Bald Eagle Peregrine Falcon Experimental Evidence Scientists fed DDTtainted food to ducks Got same problems seen in eagles What happened DDT banned in US Passed FIFRA in 1977 Federal Insecticide, Fungicide, Rodenticide Act We are moving away from pesticide application Integrated Pest Management Biological Controls Use a variety of approaches

3 Other Persistent Pesticides Chlordane Great for termites Very persistent Protects house for 10 years Also Absolutely Banned Problems in fish from Lake Springfield and the Meremec River What do we do about West Nile Virus???? Have you seen the spray trucks? Is it a good idea to spray? New York uses Malathion (certainly not DDT) PCB s (Polychlorinated Biphenyls) Other Persistent Chemicals Pesticides are not the only problem. Each chemical has its own story Persistent similar to DDT Also very resistant to decay by bacteria Used as liquid coolant and insulator in electrical devices Toxicity in Lab Animals Liver and Kidney damage Tumors Gastric disorders Birth Defects Toxicity in humans unclear May cause cancer Rice Oil Disease - Japan Bioaccumulates just like DDT PCB Contamination in the Arctic Diagram from Colborn et al.

4 Fishing bans in parts of Lake Michigan because of PCB s Major pollution problem in the Hudson River because of PCB s from General Electric Superfund sites where PCB s were used Made as a byproduct in manufacture of other chemicals Also very persistent Not very toxic to humans Causes Chloracne May cause other problems Very toxic to other animals Bioaccumulates Dioxin The Missouri Story Hexachlorophene factory sold waste oil to Russell Bliss Ol Russell sprayed oil on streets of Times Beach, Mo and a couple of horse tracks The horses died Somebody followed Russell around and found where he deposited the oil All sites contaminated with Dioxin USEPA bought out the town of Times Beach and incinerated the soil Endocrines Endocrine Disruptors Chemical Messengers Control Growth and Development Control development of sex organs and secondary sexual characteristics (among other things) Figure from Colborn et al.

5 Ultimately genes control what sex an animal will be Genes turn on endocrine systems which determine development of sexual organs and secondary sexual characteristics Environmental Problems from Endocrine Disruptors Problems in polluted locations Matings between female herring gulls Disrupted maturation Reduced viability of eggs and offspring PCB s, DDT, Dioxins all seem to act like endocrines They disrupt the endocrine systems of wildlife Result is the problems already seen in nature We don t know how much of a problem this is for humans