Description
Polychlorinated biphenyls are a mixture of individual chemicals which are no longer produced in the United States, but are still found in the environment. Polychlorinated biphenyls can cause irritation of the nose and throat, and acne and rashes. They have been shown to cause cancer in animal studies. Polychlorinated biphenyls have been found in at least 383 of the 1,430 National Priorities List sites identified by the Environmental Protection Agency (EPA).
Occurence
Polychlorinated biphenyls (PCBs) are a group of manufactured organic chemicals that contain 209 individual chlorinated chemicals (known as congeners). PCBs are either oily liquids or solids and are colorless to light yellow in color. They have no known smell or taste. There are no known natural sources of PCBs. Some commercial PCB mixtures are known in the United States by their industrial trade name, Aroclor.
PCBs don't burn easily and are good insulating material. They have been used widely as coolants and lubricants in transformers, capacitors, and other electrical equipment.
The manufacture of PCBs stopped in the United States in 1977 because of evidence that they build up in the environment and cause harmful effects. Products containing PCBs are old fluorescent lighting fixtures, electrical appliances containing PCB capacitors, old microscope oil, and hydraulic fluids.
Before 1977, PCBs entered the air, water, and soil during their manufacture and use.
Today, PCBs can be released into the environment from hazardous waste sites that contain PCBs, illegal or improper dumping of PCB wastes, and leaks from electrical transformers containing PCBs.
PCBs may be carried long distances in the air; they remain in the air for approximately 10 days.
In water, a small amount of the PCBs may remain dissolved, but most sticks to organic particles and sediments.
PCBs in water build up in fish and marine mammals and can reach levels thousands of times higher than the levels in water.
Exposure
Using old fluorescent lighting fixtures and old appliances such as television sets and refrigerators; these may leak small amounts of PCBs into the air when they get hot during operation
Eating food, including fish, meat and dairy products containing PCBs
Breathing air near hazardous waste sites that contain PCBs
Drinking PCB-contaminated well water
Repairing or maintaining PCB transformers
Health Effects
Animal testing is sometimes necessary to find out how toxic substances might harm people or to treat those who have been exposed. Laws today protect the welfare of research animals and scientists must follow strict guidelines.
People exposed to PCBs in the air for a long time have experienced irritation of the nose and lungs, and skin irritations, such as acne and rashes.
It is not known whether PCBs may cause birth defects or reproductive problems in people. Some studies have shown that babies born to women who consumed PCB-contaminated fish had problems with their nervous systems at birth. However, it is not known whether these problems were definitely due to PCBs or other chemicals.
Animals that breathed very high levels of PCBs had liver and kidney damage, while animals that ate food with large amounts of PCBs had mild liver damage.
Animals that ate food with smaller amounts of PCBs had liver, stomach, and thyroid gland injuries, and anemia, acne, and problems with their reproductive systems.
Skin exposure to PCBs in animals resulted in liver, kidney, and skin damage.
It is not known whether PCBs causes cancer in people. In a long-term (365 days or longer) study, PCBs caused cancer of the liver in rats that ate certain PCB mixtures.
The
Department of Health and Human Services (DHHS) has determined that PCBs may reasonably be anticipated to be carcinogens.
Exposure Tests
There are tests to find out if PCBs are in your blood, body fat, and breast milk.
Blood tests are probably the easiest, safest, and best method for detecting recent exposures to large amounts of PCBs.
However, since all people in the industrial countries have some PCBs in their bodies, these tests can only show if you have been exposed to higher-than-normal levels of PCBs.
However, these measurements cannot determine the exact amount or type of PCBs you have been exposed to or how long you have been exposed.
In addition, they cannot predict whether you will experience any harmful health effects.
The EPA has set a maximum contaminant level of 0.0005 milligrams PCBs per liter of drinking water (0.0005 mg/L).
The EPA requires that spills or accidental releases into the environment of 1 pound or more of PCBs be reported to the EPA.
The
Food and Drug Administration (FDA) requires that milk, eggs, other dairy products, poultry fat, fish, shellfish, and infant foods contain not more that 0.2–3 parts of PCBs per million parts (0.2–3 ppm) of food.
Reference :
Agency for Toxic Substances and Disease Registry. 1996. Toxicological profile for polychlorinated biphenyls (update). Atlanta, GA; U.S. Department of Health and Human Services, Public Health Service.
Source 1. :
Bk. "Mercury Free", by Dr. James Hardy. Gabriel Press, 1966.
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