Glaser's "Chemistry is in the News"
To Accompany Wade Organic Chemistry 4/e.
Chapter 16. Aromatic Compounds.
The bald eagle population has been greatly affected by the high levels of polychlorinated biphenyls-which are found in the eggs of the nests located near Lake Eerie. Studies have been conducted comparing the number of eggs hatched from nests located farther inland as opposed to those on the Lake. Because of runoff from nearby rivers and streams, industrial waste containing the PCB's enters the Lake and is incorporated into the food chain. The eagles' eggshells are weakened as a result of these molecules and as a result fail to hatch. The Bald Eagle is one of our national symbols to learn more about these eagles, try The Eagle's Advocate
Polychlorinated biphenyls are a group of around 200 man-made structurally related chemicals that were originally used to synthesize hydraulic fluids, flame-retardants, ink, paint, and adhesives. PCBs are among the most stable organic compounds known, they resist breakdown from high temperatures and aging. The World Chlorine Council have produced a paper on The Best Available Techniques for Destruction of PCBs. These physical and chemical properties that make PCBs commercially valuable also make them environmentally detrimental. Here is a PCB Hazard Summary from the EPA, posted courtesy of The Coalition Opposed to PCB Ash in Monroe County, Indiana (COPA)
Because of their stability, these compounds are known to be
bioaccumulative and concentrated at higher levels of food chains. The
first thing that reacts when the PCB is exposed to bodily mechanisms is
its own hydrolysis, which interferes with various metabolic processes and
disguises itself as estrogen. Because of this, PCBs and other similarly
biologically active compounds are collectively known as Environmental
Estrogens. These chemicals interfere with embryonic development and
are the reason why the eggs didn't hatch. The Introduction to Hormone
Disrupting Chemicals provides more information on these potentially
dangerous chemicals. Studies
at the University of Albany have also shown that PCBs also hinder
reproductive processes with other animals.
Pertinent Text References
Chapter 16. Aromatic Compounds.
Question 1: What evidence the article present that PCB's are responsible for the declining population of Bald Eagle hatchlings?
Question 2: If the production of PCB's in North American Industry was banned in 1977, then why do they continue to pose a problem to the environment? (Especially animals at the top of the food chain, like the Bald Eagle.)
Question 3: What are some of the possible effects on humans of PCB's and other similar hormone disrupting chemicals?
Question 4: Considering the information presented in the article, and the lab studies done on the effects of PCB's in rats (project 3); is the article justified in concluding that PCB's are the cause of the decreased hatchling population?
Why do humans only take action concerning environmental
issues when it
directly affects us? What must it take for legislators and other
politicians to take the initiative and propose courses of action to help
control this situation? Could there possibly be economic trade-offs for
which the condition of the environment is compromised? What can be done
to make people more aware and responsive to environmental hazards?
AnswersAnswer 1: 1. The article presents as evidence, that there are increased levels of PCBs in eggs that failed to hatch.
Answer 2: PCBs do not naturally degrade in the environment, and they are bioaccumulative and thus while present in low levels in smaller animals and the soil, they become concentrated at the top of the food chain.
Answer 3: The effects of these hormone-disrupting chemicals in humans may include: increased levels of breast and testicular cancers, lowered sperm counts, and many other reproductive abnormalities.
Answer 4: Yes, the article appears to be justified in its assertion, because the studies on rats have shown that high levels of PCBs in pregnant rats have caused severe developmental problems in the embryonic rats.