Introduction
Carbon, hydrogen, and chlorine atoms make up polychlorinated biphenyls (PCB)s. PCB molecule's chemical and physical characteristics depend on the number of chlorine atoms and their location within the molecule. PCBs range in viscosity from an oil to a waxy solid and contain no discernible flavor or odor.
PCBs are a member of the large group of organic compounds created by humans known as chlorinated hydrocarbons. Between 1929 and 1979, PCBs were produced domestically before being outlawed in 1979. They come in various toxicities and consistencies, ranging from thin, light-colored liquids to waxy yellow or black solids. PCBs were utilized in countless industrial and commercial applications because of their non-flammability, chemical stability, high boiling point, and electrical insulating qualities. Some of these uses include:
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Equipment for heat transport, electricity, and hydraulics.
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Paints, plastics, and rubber products all include plasticizers.
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Various colors, dyes, and carbonless paper.
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Further industrial applications.
What Are the Commercial Uses of PCBs?
Products that contain PCBs include:
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Capacitors and transformers.
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Voltage regulators, switches, re-closers, bushings, and electromagnets are all examples of electrical equipment.
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The oil is used in hydraulic and motor systems.
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Outdated electrical equipment with PCB capacitors.
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Ballasts for fluorescent lights.
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Insulation for cables.
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Materials for thermal insulation include fiber, felt, foam, and cork.
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Tapes and adhesives.
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Paint made from oil.
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Plastics.
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Non-carbon copy paper.
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Floor finish.
The PCBs utilized in these items were chemical combinations of various distinct congeners of chlorinated biphenyls.
How Are PCBs Exposed in the Environment?
PCBs can be released in the environment from:
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Locations with PCB-filled hazardous trash need to be correctly kept.
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Inappropriate or illegal disposal of PCB waste.
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Leaks or releases from PCB-containing electrical transformers.
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Disposal of consumer products containing PCBs in municipal or other landfills that are not equipped to manage hazardous trash.
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Some garbage is being burned in municipal and commercial incinerators.
As soon as they are in the environment, PCBs do not quickly degrade. Instead, they can linger for extended durations while switching between the earth, water, and air. PCBs have been discovered in snow and sea water in locations far from where they were introduced into the environment, proving that they may travel great distances. As a result, they can be found anywhere. Generally speaking, PCB may be moved farther from the source of contamination the lighter it is.
Plants and food crops can acquire PCBs in their leaves and other above-ground components. Additionally, they are absorbed by fish and tiny creatures. As a result, PCBs that have bioaccumulated in the fish that people eat may be exposed to them.
What Are the Adverse Effects of PCBs on Health?
It has been shown that PCBs can have several harmful impacts on health. They have been proven to have substantial non-cancer health impacts on animals, including effects on the immune system, reproductive system, neurological system, endocrine system, and other health consequences. They have also been proven to induce cancer in animals. Studies on humans provide evidence for PCBs' possible cancer-causing and non-cancerous impacts. In addition, there may be connections between PCBs' various health consequences. Changes in one system may significantly impact how the body's other systems function. The different health effects are discussed below:
1. Cancer: Assessments of PCBs' potential carcinogenicity have been made in numerous studies, including both human and animal populations; by employing a method that enables a review of the entire carcinogenicity database, Environmental Protection Agency (EPA) makes it possible to view individual research findings in the context of all other available studies. Animal studies have proven beyond a doubt that PCBs cause cancer. Studies on people raise new questions about PCBs' propensity to cause cancer. Together, the information suggests that PCBs are probably carcinogenic for humans.
2. Non-Carcinogenic Effects: When estimating the probable noncarcinogenic toxicity of environmental pollutants, such as PCBs, EPA considers all the currently available information. The EPA discovered unequivocal evidence that PCBs have considerable harmful effects on animals, including non-human primates, based on much research using environmentally relevant concentrations. Animals' immune systems, reproductive systems, neurological systems, and endocrine systems can all be impacted by PCBs. All these systems are intricately regulated by the body and linked together. Unsurprisingly, PCBs can have many detrimental health impacts.
3. Immune Effects: The immune system is essential for preventing infections, and immune system disorders have potentially severe consequences for human and animal health. Rhesus monkeys and other animals have been used in studies on the immunological implications of PCB exposure. The similarity between the immune systems of Rhesus monkeys and people should be noticed. Studies on monkeys and other animals have identified several grave immune system consequences brought on by PCB exposure, including:
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The thymus gland, essential to developing the young monkey's immune system, has significantly decreased.
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Immune system responses are less aggressive after being challenged with sheep red blood cells. This standard laboratory test assesses an animal's capacity to produce a primary antibody response and acquire protective immunity.
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Animals exposed to PCBs have decreased resistance to the Epstein-Barr virus and other diseases.
Immune system disorders may make a person more prone to viral infections and pneumonia. According to a recent human study, those who carried the Epstein-Barr virus were more likely to have higher PCB exposures. Additionally, compared to people who did not have an Epstein-Barr virus, it raised the chance of non-Hodgkin's lymphoma. This result is in line with an increase in Epstein-Barr virus infection in PCB-exposed animals.
4. Reproductive Effects: Rhesus monkeys, rats, mice, and mink are just a few of the animal species in which the effects of PCBs on reproduction have been researched. The most reliable laboratory species for predicting harmful effects on human reproduction is widely thought to be rhesus monkeys. Following exposure to PCB combinations, monkeys and other animal species showed potentially dangerous effects on the reproductive system. Most significantly, PCB exposure was found to lower sperm counts in rats and lower sperm weights, conception rates, and live birth rates in monkeys and other species. Long after PCB doses were administered, the effects in monkeys were still noticeable. Studies on the results of PCB exposure on reproduction have also been conducted in human populations. Children born to mothers who worked in workplaces with PCBs had lower birth weights and significantly shorter gestational ages as their PCB exposure increased. Studies on fishing populations that are thought to have substantial PCB exposure also point to similar declines. The fact that different species of animals exposed to PCBs experienced the same impact shows that PCB exposure may have significant consequences on human reproduction.
5. Neurological Effects: Early learning depends on the nervous system developing correctly, which can also affect an individual's health throughout their lifetime. Monkeys and many other animal species have been used to study PCBs' effects on the nervous system's development. A permanent and substantial loss in brain development, including visual recognition, short-term memory, and learning, was seen in newborn monkeys exposed to PCBs. The PCB kinds most frequently identified in human breast milk were used in several of these research studies. Learning deficits and changes in activity linked to PCB exposures have been suggested by human studies, along with similar effects to those shown in monkeys exposed to PCBs.
Conclusion
Animal studies have proven beyond a doubt that PCBs cause cancer. In addition, studies on people raise new questions about PCBs' propensity to cause cancer. Together, the information suggests that PCBs are probably carcinogenic for humans.
