Examples of Endocrine Disruption

Data accumulated over the past two decades reveal substantial global contamination by EDCs. Contaminant dispersal is brought about by a combination of factors, including purposeful or accidental release into the environment, followed by long-range atmospheric transport. It also occurs because some EDCs have been incorporated both deliberately and inadvertently into consumer products. With regard to long-range transport, large masses of air have been tracked across the Pacific carrying a variety of pollutants from central Asia to the west coast of the US virtually undiluted, including ozone, heavy metals, and organochlorine compounds. In addition, so-called 'global distillation' processes - repeated sequences of volatilization and condensation - transport semivolatile compounds from sites of production, use, and disposal to colder regions, particularly at high latitude and altitude. The accumulation of vast amounts of plastic products in the oceans is yet another source of global pollution, due to leaching of endocrine disrupting chemicals from plastic.

Two of the many examples of inadvertent contamination of people due to the use of consumer products that contain EDCs include exposure to phthalates and bisphenol A. Phthalates are used as additives in cosmetics, intravenous medical tubing, and a wide variety of other products, including those made from polyvinyl chloride (PVC). Polyvinyl chloride products contain phthalates to soften the otherwise brittle PVC; so all PVC contains some amount of a phthalate, the softer the product, the greater the amount of phthalate. Exposure to bisphenol A is also widespread. Bisphenol A is a monomer (not just an additive) used in the manufacture of resins that line the inner surface of food metal cans, and to manufacture polycarbonate plastic, which is hard and clear (although it can be colored), and is used to make food and beverage containers as well as a wide range of other products; bisphenol A is thus also used as an additive in many types of plastic, including PVC. Phthalates and bisphenol leach from these products and disrupt endocrine function. There are over 6 billion pounds of bisphenol A and in excess of 4 billion pounds of phthalates produced each year.

Coincident with emerging knowledge of the ability of EDCs to disrupt a range of developmental processes, increases have been reported in a wide range of human health diseases and abnormalities, though some remain controversial. These include increases in the frequency of (obesity and cognitive/behavioral dysfunctions, such as autism and attention deficit hyperactivity disorder (ADHD). There have also been increases in a cluster of male reproductive outcomes (cryptorchism, hypospadias, testicular cancer, and decreased sperm function) all of which are believed to originate in utero, and have been termed the testicular dysgenesis syndrome. . The strength of the epidemiological evidence demonstrating these epidemics varies. For example, there is little argument that there has been a widespread increase in rates of obesity and diabetes, but there is still significant debate about global decreases in reproductive function or increases in ADHD, due to limitations of historical data. While extensive study will be required to identify causes of these trends, their underlying biology suggests that alterations in inter- and intracellular signaling processes may be causally involved, and for each of the mentioned epidemics, data are available indicating one or more points of vulnerability to EDCs in the mechanisms of control. EDCs may also contribute importantly to geographic variability in these health endpoints.

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