October 13, 2015 Pollution Written by Greentumble
polychlorinated biphenyls
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[sc:1].

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[sc:2].

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[sc:2].

Health effects of 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[sc:2].

    • Liver Problems

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[sc:2].

    • Endocrine Effects

Potential negative impacts on the endocrine system that may occur due to PCB exposure include a 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[sc:2]. 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[sc:2].

    • Skin Problems

PCB exposure can potentially lead to skin lesions, skin irritations, and pigmentation of the skin and nails[sc:2].

    • Eye Problems

PCB exposure can potentially lead to swollen eyelids, abnormal eye pigmentation, and hypersecretion of the Meibomian glands[sc:2].

    • 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[sc:2]. Other potential immune system effects include atrophy of the thymus gland and spleen, changes in the lymph nodes, and reduced antibody production[sc:2].

    • Neurological Effects

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[sc:2]. Other potential neurological effects of PCBs include reduced spatial cognition, impaired learning, and a reduction in dopamine levels within the brain[sc:2].

    • Reproductive Effects

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[sc:2].

    • Developmental Effects

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[sc:2].

    • Cancer Risks

PCBs are classified as probable carcinogens by both the International Agency for Research on Cancer (IARC) and the the U.S. Environmental Protection Agency[sc:2].



[sc:1] http://www.epa.gov/epawaste/hazard/tsd/pcbs/about.htm
[sc:2] http://www.atsdr.cdc.gov/toxprofiles/tp17-c2.pdf