Polychlorinated Biphenyls: What Are PCBs Used For & Human Health Effects of PCBs
Polychlorinated Biphenyls (PCBs) are man-made persistent organic chemicals that have many negative impacts on the environment and on human health. At one time, PCBs were widely used in both industrial and commercial applications but have now been banned since 1979.
Once PCBs are released into the environment, they are altered through various chemical and biological processes that convert them into polluting toxins that can bioaccumulate within food chains and within the human body. PCBs can pollute soil, air and water with a typical half-life of many years.
What were polychlorinated biphenyls (PCBs) used for in the 1970s?
Polychlorinated Biphenyls (PCBs) were manufactured beginning in 1929 until they were banned in 1979 based upon the discovery of their toxicity and accumulation in the environment .
Because PCBs are highly stable and insulating, they served as ideal chemicals for many different industrial and commercial uses, including:
- electrical equipment
- heat transfer equipment
- hydraulic equipment
- flame retardants
- pesticide extenders
- surface coatings
- wire insulators
- metal coatings
- carbonless copy paper
Consumer products made before 1979 that could contain PCBs include fluorescent lighting fixtures, electrical devices, appliances, microscope oil, and hydraulic oil [1,2,3].
How do PCBs affect the environment?
Prior to their ban, PCBs pollution of the environment occurred during the time of manufacturing and use.
Today, such pollution can still occur from leaks from hazardous waste sites that have PCBs in them, improper disposal of PCB wastes, leaks from electrical transformers that have been manufactured with PCBs, and the burning of PCB-containing waste in incinerators .
Because they are persistent organic pollutants, PCBs can remain in the environment for many years, and pollute air, water, and soil for long distances away from the location of the initial PCB pollution. In fact, PCBs are now found in many places around the world today .
PCBs can bioaccumulate in plants and animals such as fish and have the potential to cause negative health effects in the humans that consume them, such as cancer and problems with the immune system, reproductive system, nervous system, and endocrine system .
Human exposure to PCBs usually occurs when people eat food (such as by eating fish from PCB-polluted waters) or breathe air that has been contaminated with PCBs, with contaminated food as the major source.
Breast-feeding mothers who have been exposed to PCBs may pass some of these toxins along to their infants through their breast milk and pregnant women may pass along PCBs to their children in the womb.
Health effects of human exposure to PCBs
The exposure to PCBs can result in a number of negative health effects, including liver problems, endocrine system problems, thyroid, skin, and eye problems, altered immune systems, neurodevelopmental problems, reduced birth weight, toxicity of the reproductive system, and cancer .
Potential negative impacts on the liver that may occur due to PCB exposure include increased liver enzyme production, increased lipid and cholesterol production in the liver, and a reduced ability of the liver to store Vitamin A (Vitamin A is necessary for healthy growth and healthy cells.), and other forms of liver dysfunction .
Potential negative impacts on the endocrine system that may occur due to PCB exposure includea depletion of circulating thyroid hormone and the development of hypothyroidism, which can both occur as a result of exposure to PCBs in the womb.
Thyroid hormones are necessary for the proper development of the brain and thyroid during the second trimester of pregnancy. PCBs can interfere with the production and proper circulation of thyroid hormones .
Such negative endocrine system impacts may also negatively impact the adrenal glands and adrenaline levels in the body, as well as cause competitive binding to estrogen receptor sites in the body .
PCB exposure can potentially lead to skin lesions, skin irritations, and pigmentation of the skin and nails.
PCB exposure can potentially lead to swollen eyelids, abnormal eye pigmentation, and hypersecretion of the Meibomian glands .
Immune system effects
PCBs can negatively impact the immune system of both adults and infants, especially in infants that were exposed to PCBs in the womb and through breast feeding. Immune system problems caused by PCB exposure include an increased susceptibility to respiratory tract infections, ear infections, and other infectious illnesses.
Other potential immune system effects include atrophy of the thymus gland and spleen, changes in the lymph nodes, and reduced antibody production .
PCBs may be particularly harmful to the developing nervous systems of newborns and young children of women who have a large PCB body burden. Reduced memory capacity and lower IQ scores are associated with PCB exposure in the womb.
Other potential neurological effects of PCBs include reduced spatial cognition, impaired learning, and a reduction in dopamine levels within the brain .
Studies indicate that PCBs disturb the female menstrual cycles and negatively impact sperm production in males, as well as reduce fertility for both sexes. PCB exposure can also lead to reduced fetal survival in the womb .
Exposure of developing fetuses in the womb to PCBs has been associated with reduced thyroid function, negative impacts on the brain and reproductive system, and in some cases, reduced birth weight, reduced head circumference, and a reduced body weight at 4 years of age .
PCBs are classified as probable carcinogens by both the International Agency for Research on Cancer (IARC) and the U.S. Environmental Protection Agency .