Polychlorinated biphenyls, or commonly referred to as PCBs, are mixtures of up to 209 individual chlorinated compounds. There is no evidence of a natural source of these congeners, and they are either oily liquids or solids that are colorless and sometimes a light yellow. PCBs have been used as coolants and lubricants in transformers, capacitors, and other electrical equipment because of they do not burn easily and serve as good insulators. Many of these commercial PCB mixtures are known in the U. S. by the trade name Aroclor.
Because of evidence that showed PCBs collecting in the environment and causing health problems, the manufacture of PCBs was stopped in the U. S. in 1977 (1).
Although the manufacture of these toxins has ceased, there are still reports of high PCB levels in our wildlife. These effects on the wildlife, in turn, effect the people that consume these contaminated species, and can cause serious health problems. Because PCBs are not created naturally, all the PCBs that seep into the environment are caused from man’s recklessness.
PCBs initially enter the air, water, or soil during their manufacture, use, or disposal. They are released into the environment from accidental spills and leaks during their transport or from leaks or fires in the products containing PCBs. Some hazardous wastes containing PCBs that have been improperly disposed or handled allow the toxins to escape as well. Leaks in old electrical transformers containing PCBs and the burning of some wastes in incinerators is an example of this improper disposal. It is important to understand how these chemicals enter the environment to increase prevention of the problems these toxins create (1).
The Review on Problems and Purposes
Most English as a second language teachers find it a difficult task to implement clasroom management in a cooperative learning environment. This research will focus on identifying the classroom techniques that ESL lecturers use to effectively implement clasroom management during cooperative learning. The researcher used both the quantitative and qualitative research methods to display the ...
A large concern with PCBs is that they do not readily break down in the environment and thus may remain there for a very long period of time (1).
PCBs are highly mobile because they have the ability to evaporate, and can be carried by winds (4).
PCBs can travel long distances in the air and be deposited in area far away from where they were released. In the St. Lawrence River, where no PCBs or related chemicals have been produced for decades, beluga whales have PCB levels so high that they are treated as hazardous waste after they die.
Even in the most remote Arctic regions PCBs can be found because of their permeable nature (3).
In water, a small amount of PCBs may remain dissolved, but most stick to organic particles and bottom sediments. PCBs also bind strongly to soil (1).
PCB levels in water alone are not the problem, however it is the way PCBs persist in the food chain because of the way they accumulate in animal fat tissue (3).
Bottom-feeders such as crawfish and other small aquatic species take up these PCBs either directly from the water or from smaller organisms that have previously consumed the chemical. In turn, the PCB is transferred to larger animals that eat these bottom-feeders.
The PCBs, then, accumulate in fish and marine animals, reaching levels that may be thousands of times higher than water (1).
An environmental group released a study showing that farmed salmon concealed high levels of toxic PCBs. The Environmental Working Group warned that the farm-raised fish should not be eaten more than one a month. These farmed fish amass such high levels of PCBs because they are fed ground-up fish that can have high levels of PCBs.
The level is far below the Food and Drug Associations limit of 2, 000 part per billion in fish, but the Environmental Protection Agency does not recommend eating fish with PCB levels between 25 and 48 parts per billion more than one a month. This made the pin-raised salmon tested by the Environmental Working Group flagged as unhealthy since it had PCB levels of 27 parts per billion (2).
The Term Paper on Small Animal Diseases Corona Virus
Louise Pasteur, a Frenchman who was neither a physician nor a veterinarian moved into the spotlight to help find a vaccine for Rabies. He began the study of Rabies when two rabid dogs were brought into his laboratory. One of the dogs suffered from the dumb form of the disease: his lower jaw hung down, he foamed at the mouth, and his eyes had a rather vacant look. The other dog was furious: he ...
Scientist argue whether the heart-healthy benefits of salmon outweigh the PCB exposure, but when one considers the health risks of PCB, the two effects have little to do with each other. The effects of PCBs can be quite serious.
However people in the general population do not show these symptoms, people who are exposed to large amounts of PCBs most commonly observe skin condition such as acne and rashes. Studies in exposed workers have shown changes in blood and urine that may indicate liver damage. In laboratories experiments were created to test PCBs’ effects on smaller mammals, and animals that ate food containing large amounts of PCBs for short periods of time had mild liver damage and some died. Animals that ate smaller amounts of PCBs in food over several weeks or months developed various kinds of heath effects, including anemia; acne-like skin conditions; and liver, stomach, and thyroid gland injuries. Other effects of PCBs in animals include changes in the immune system, behavioral alterations, and impaired reproduction (1).
With certain animals such as the alligator or turtle, when PCBs are applied at the right developmental stage, it can change male turtles or alligators into females. In Japan in 1968, and again in Taiwan in 1979, women ingested rice oil that was contaminated with PCBs. The children born to those women have suffered from physical and mental developmental delays, behavioral problems including hypo activity, hyperactivity, abnormally small penises, and IQ scores five points below average. Another study was done on babies born to mothers who had eaten trout or salmon caught in Lake Michigan, a known lake deposit of PCBs and other toxins. At birth the babies’ blood in the umbilical chord was tested for PCB levels, and those with the highest levels of PCB had smaller heads and a lower birth weight.
Cognitive tests were then done seven months after birth in which they would show a two identical photos to the infants for about twenty seconds. Then, one of the old photos was paired with a new photo and shown to the infant once more. The normal response is for the infant to recognize the old photo and spend more time looking at the new photo. The babies that had the highest exposure to PCBs, however, spent the same amount of time looking at each of the photos, suggesting either short-term memory loss or an attention disorder. Later, when the children were four years old another test was conducted where each child would have to remember progressively longer strings of words and numbers.
The Review on The Effects of Truancy on High School Students
1.1 Statement of Problem Truancy is defined as an unexcused absence. It is a common problem facing nearly all high schools across the nation (Baker, Sigmon, & Nugent 2001 p.1). High school truants contribute to many consequences both to themselves and community. According to Garry (n.d.), many police departments report that daytime crime rates are rising in the part because students are ...
Again, those who had the highest exposure scored lower on the test. The differences in scores between unexposed and the highest-exposed children, says the scientist in charge of the experiments, Joseph Jacobson, “would be like ten points on an IQ test. We ” re not seeing mental retardation, but we are seeing that the children are just not doing as well. (3) ” There are no reports of structural birth defects caused by exposure to PCBs or of health effects of PCBs in older children (1).
Because there are many factors that have not been monitored such as alcohol intake and tobacco smoking, there is no direct proof yet that PCBs are the main reason for these lessened behavioral responses. The correlation between these studies and the levels of PCBs is significant and can not be ignored either. A theory on how PCBs might be de scrambling messages in the brain is that PCBs are mimicking or blocking the action of the thyroid hormones. These hormones help organize the fetal brain and promote the growth of neurons, the nerve cells that transmit information.
Severe disruptions in the thyroid’s hormone levels can even lead to mental retardation. Theo Colburn, a scientist credited with giving awareness to these endocrine-disrupting chemicals, said: “You can’t go back and rebuild a brain. You can’t go back and put more sperm cells in a male. But the beauty of this is that it’s not the result of genetic damage. The blueprint for the normal individual is still there. What we have to do is make sure that while that blueprint is being followed, while the chemical messengers that tell this individual how to develop are doing their job, we ” re not introducing more chemicals into the environment of the womb.” (3) He basically tells us that these chemicals do not change our genetic makeup, which means that the effects of PCBs will not be passed on hereditarily; however, they do hinder our bodies’ development.
The Term Paper on Fish Farming
Fish farming is the principal form of aquaculture, while other methods may fall under mariculture. Fish farming involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases young (juvenile) fish into the wild for recreational fishing or to supplement a species’ natural numbers is generally referred to as a fish hatchery. Worldwide, the most important ...
The biggest way to reduce risk from PCBs is prevention. The fish farms that are supplying these polluted fish should have a required inspection for water toxins. Areas with high levels should be abandoned and not used to raise the fish. Even though studies have shown that high levels of PCBs have been found in these farms, not all farms are polluted. Many farms are clean and have no problems.
Also, women who are pregnant should steer clear from fish. In general, the level of fish one eats should be regulated. One should be cautious of where the fish was raised or caught before consuming, because even fish caught in the wild have been known to carry dangerous chemicals such as mercury (5).
Too much of one thing is usually not good, and in this case fish consumption needs to be moderate. Preventing the toxins from entering our environment is important as well. The old appliances that contain PCBs, such as electrical equipment and transformers should be disposed of properly, as to avoid leakage.
Although PCBs have not been produced in thirty years, these toxins cannot be ignored, because their effects have proved to be potent.
