Polychlorinated biphenyls hormones, effect

Hallgrcn S, Damerud P. 1998. Effects of polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and chlorinated paraffins (CPs) on thyroid hormone levels and enzyme activities in rats. Organohalogen Compounds 35 391-394. 

PCBs Polychlorinated biphenyls are a group of toxic chemicals used for a variety of purposes and found in a number of products, such as carbonless copy paper, adhesives, hydraulic fluids, and caulking compounds. They were originally used to insulate electrical equipment, and although they ve been banned in the United States since the late seventies, they are still found in water. They accumulate in the sediment at the bottoms of rivers and lakes, and build up in the fatty tissues offish. The primary effect of PCBs is on the endocrine system, which is responsible for regulating the hormones in our bodies. They are particularly dangerous to fetuses and young children. If PCBs get into your bloodstream, they can upset the body s natural hormone levels and can lead to birth defects and cancers. 

Seo B-W, Li M-H, Hansen LG et al. 1995. Effects of gestational and lactational exposure to coplanar polychlorinated biphenyl (PCB) congeners or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on thyroid hormone concentrations in weanling rats. Toxicol Lett 78 253-262. 

Sher ES, Xu XM, Adams PM, Craft CM, Stein SA (1998) The effects of thyroid hormone level and action in developing brain Are these targets for the actions of polychlorinated biphenyls and dioxins Toxicol Ind Health, 14 121-158. 

The biological activities of steroid hormones result from interactions with specific receptors. For example, estradiol interacts with the estrogen receptor. Some industrial chemicals, such as DDT, bisphenol A, and polychlorinated biphenyls, may possibly interact with these receptors and cause hormonal effects on people and wildlife. 

Neurotoxicity can also occur as a result of indirect effects. For example, damage to hepatic, renal, circulatory, or pancreatic structures may result in secondary effects on the function and structure of the nervous system, such as encephalopathy or polyneuropathy. Secondary effects would not cause a substance to be considered neurotoxic, though at high enough doses, neurotoxicity could be evident. Thus, for the purpose of this review, a substance is defined as neurotoxic when it or its metabolites produce adverse effects as a result of direct interactions with the nervous system. It should be noted, nevertheless, that some chemicals may have multiple modes of action and affect the nervous system directly and indirectly. For example, several halogenated compounds (e.g., polychlorinated biphenyls (PCB), polybrominated diphenyl ethers (PBDE)) may interact directly with brain cells, and also affect the development of the nervous system by altering thyroid hormone homeostasis.7 8... 

The saga of brominated flame retardants offers a cautionary tale for the chemical industry.65 These chemicals, developed in the early 1970s, are used in a wide range of consumer products, such as furniture, foam, and plastic casings of electronic devices. In 1998, Swedish scientists reviewing archived human breast milk samples discovered that certain flame retardant chemicals (polybrominated diphenyl ethers, or PBDEs) had doubled in concentration in Swedish breast milk about every five years over the preceding twenty. This was a source of concern, as studies of laboratory animals had shown that PBDEs dismpt thyroid hormones. Such dismption yields neurobehavioral effects similar to those of PCBs (polychlorinated biphenyls), whose manufacture the United States banned in 1976. 

Gould JC, Cooper KR, Scanes CG. 1997. Effects of polychlorinated biphenyl mixtures and three specific congeners on growth and circulating growth-related hormones. Gen Comp Endocrinol 106(2) 221-30. 

Koopman-Esseboom C, Morse DC, Weisglas-Kuperus N, et al. 1994a. Effects of dioxins and polychlorinated biphenyls on thyroid hormone status of pregnant women and their infants. Pediatr Res... 

Schuur AG, Bergman A, Brouwer A, et al. 1999. Effects of pentachlorophenol and hydroxylated polychlorinated biphenyls on thyroid hormone conjugation in a rat and a human hepatoma cell line. Toxicol in Vitro 13 417-425. 

Zoeller RT, Dowling ALS, Vas AA. 2000. Developmental exposure to polychlorinated biphenyls exerts thyroid hormone-like effects on the expression of RC3/neurogranin and myelin basic protein messenger ribonucleic acids in the developing rat brain. Endocrinology 141(1) 181-189. 

Zoeller, R.T. (2001). Polychlorinated biphenyls as disrupters of thyroid hormone action. In (eds L.W. Robertson and L.G. Hansen), PCBs, Recent Advances in Environmental Toxicology and Health Effects. The University Press of Kentucky, Kentucky, pp. 265—269. 

As outlined in Chapter 2, ECD are chemicals that can cause hormonal related diseases and dysfunctions that can be effective even at very low levels (at parts per trillion, levels at which most chemicals have never been tested). ECD became a significant focus of environmental science and medicine in recent years because of its critical importance in heath. A wide range of chemicals, both natural compounds (phytoestrogens) and some synthetic chemicals (including polychlorinated biphenyls (PCB), dioxins, certain preservatives and metal ions, even certain woods) are all suspected of being capable of endocrine disruption in humans. 

In its broadest sense, environmental chemistry might be considered to include the chemistry of everything outside of the synthetic chemist s flask The moment that a chemical substance is released to the environment, its physico-chemical properties may have an enormous impact on ecological systems, including humans. Researchers have identified 51 synthetic chemicals that disrupt the endocrine system. Hormone disrupters include some of the 209 polychlorinated biphenyls (PCBs), and some of the 75 dioxins and 135 furans that have a myriad of documented effects (1). The latter half of the twentieth century has witnessed more synthetic chemical production than any other period in world history. Between 1940 and 1982, the production of synthetic chemicals increased about 350 times. Billions of pounds of synthetic materials were released into the environment during this period. United States production of carbon-based synthetic chemicals topped 435 billion pounds in 1992 or 1600 pounds per capita (2). 

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