Question:Describe the issues associatedwith the persistence of pesticides in the environment
Why Pesticides so Persistent in the Environment?
· Because of their synthetic chemical structures, natural decomposers like bacteria and fungi haven't evolved ways yet to degrade synthetic pesticides
· Since there is no natural way to degrade pesticides (except for waiting out for the half-time, which can be over 100 days), pesticides accumulate in environment and food web
· Chlorinated hydrocarbons take especially long to degrade in environment (persist for many years)
Bioaccumulation and Biological Magnification of
Pesticides:
· As pests consume pesticides and die, they may get consumed
· These pesticides continue up the food web and buildup in organisms' bodies
· This problematic continual buildup of pesticides, normally as fatty tissues, is called bioaccumulation
· Organisms at higher trophic levels have greater concentrations of pesticides than organisms at lower levels have (the 10% rule doesn't apply to pesticides, so all pesticides in an organisms are passed onto the next tropic level
· This is called Biological Magnification
Effects of Pesticides on Non-Target Organisms:
· Pesticides, because of their motility, can reach a variety of different organisms
· Bald eagles were nearly driven to extinction at one point, partially due to DDT, a pesticide
· Bald eagles consumed organisms contaminated with DDT, and as a consequence, their eggs became so thin that they often cracked before the embryo matured and the egg could hatch
· Because pesticides are often air-sprayed, they can contaminate the air and accumulate in bird populations which can inhale them
· Also, all marine life is vulnerable to pesticides because pesticides in the air can come down with precipitation and enter oceans, fresh water, and soil
· The pesticide triclopyr has been shown to kill nitrifying bacteria; other pesticides have similar affects on beneficial soil microbes
· Since they can kill the mutually symbiotic bacteria of plants, pesticides indirectly harm plant growth because these bacteria help them attain useful nutrients
· Due to biological magnification, many organisms in the uppermost trophic level can die and thus destroy fragile ecosystems
· Trifluralin, a pesticide, was found to inhibit the growth of two common cyanobacteria
· Many pesticides kill harmful pests, but also other small beneficial insects like ladybugs and butterfliess
Mobility of Pesticides in the Environment:
· Pesticides have the potential to move great distances through the air, soil, and water
· Pesticides which remain in the soil can seep downward and enter bodies of water, where they can disrupt ecosystems
· Pesticides can also seep into wells which humans use
· Pesticides can be carried by the air to aquatic sites or other ecosystems where they can be harmful
· Pesticides can accumulate in crops, wh5ch are harvested and eaten
· Even if the crop is fed to livestock, the pesticides from the crop will accumulate in the livestock and when humans consume the meat, they will also consume the pesticides inside of it
Pesticides' Risk to Humans:
· Humans normally absorb pesticides through their skin, but they can also enter through inhaling and swallowing
· Mild exposure to most pesticides will normally result in headaches, nausea, vomiting, diarrhea, and numbness
· According to the EPA, heavy exposure (such as coming into contact with an airdrop of pesticide) to certain pesticides, such as organophosphates, can debilitate the nervous system, cause cancer, and even kill humans
· Exposure to pesticides made of chlorinated hydrocarbons can result in convulsions which lead to comas
· When pesticides are mishandled people can be killed and hurt
In the Bhopal disaster in India, 40 tons of MIC gas, which is used to make pesticides, erupted and created a huge toxic cloud which killed 2500 people and rendered another 60,000 psychologically, neurologically, or reproductively impaired
· Continual long-term exposure to pesticides has been linked with cancer, sterility, and hormonal problems
· The World Health Organization estimates that 3 million people have been poisoned, and 220,000 have been killed, by pesticides
· Pesticides have a larger affect on children than on adults
· Studies have shown that exposure to pesticides affects children’s intellectual and motor development
· Most legislation just protects the general population from pesticides, but children require different and stricter regulations for their health
Works Cited
"Extoxnet FAQs - Questions About Pesticide Exposure." EXTOXNET - The EXtension TOXicology NETwork. Web. 23 Feb. 2010. <http://extoxnet.orst.edu/faqs/pesticide/pestexp.htm>.
- This website helped show effects of pesticides on humans
"Harmful Effects of Pesticides on Non-target Organisms." Safe Pest Control. Web. 24 Feb. 2010. <http://stephentvedten.blogspot.com/2009/10/harmful-effects-of-pesticides-on-non.html>
- This website gave detail on studies done about pesticides' effects on non-target organisms
Map Displaying Pesticide Contamination. Digital image. Water Resources for Maryland, Delaware, and the District of Columbia. United States Geological Survey. Web. 23 Feb. 2010. <http://md.water.usgs.gov/publications/fs-2006-3119/html/figure1_big.gif>.
- This map is used in our website to show how mobile pesticides can be
"Specific Effects of DDT on Predatory Bird Populations and Relationship to Biological Magnification." TCSINCWEB.COM. Web. 24 Feb. 2010. <http://www.tcsincweb.com/DDT/DDTEffectsOnBirds.htm>.
- Graph which showed relationship between eagles and DDT exposure
West, Jim. Graph Relating Pesticides and Polio. Digital image. WHALE. Web. 23 Feb. 2010. <http://www.whale.to/vaccine/west5a.html>.
- Graph showing relationship between human disease and pesticide exposure
