PCBs are a group of chemicals known as chlorinated hydrocarbons. There are different chemical makeups for the PCBs known as congeners. They started being used in 1929 and then were banned 50 years later in 1979. They were used in high quantities for different industrial processes. The most common PCB is known as aroclor.
PCBs can be found within the environment due to the improper disposal of waste, and leaching from old hazardous waste sites. When PCBS enter the environment they are extremely persistent and do not readily break down. They can be found within the water, soil, and air.
PCBs are known to cause negative effects in rodents to the endocrine system, nervous system, reproductive system, and immune system. The effects upon the endocrine system include decreased thyroid hormone levels. An effect upon the nervous system includes learning disabilities. The reproductive effects include low birth weight of children exposed to PCBs. Finally, effects include suppression of the immune system. The EPA has determined that PCBs are probable human carcinogens.
For more information regarding polychlorinated biphenyl (PCB):