"The evidence for adverse reproductive outcomes (infertility, cancers, malformations) from exposure to endocrine disrupting chemicals is strong" -- The Endocrine Society
Endocrine disruptors or endocrine disrupting chemicals (EDCs) are exogenous chemicals that interfere with the normal physiological function of the endocrine system in humans and wildlife. The endocrine system is a system of glands that secrete hormones that bind to receptors on the surfaces of specific cells. The endocrine system allows a cell to respond to external stimuli, causing long term developmental and reproductive changes. It is crucial in the maintainance of homeostasis and in allowing normal development of an organism.
EDCs that interfere with the endocrine system have developmental, reproductive, neurological and immunological effects. Research has shown that such effects are most pronounced during prenatal and early post-natal development, at a time when organs and neurological systems develop. Developmental defects due to EDCs may include low sperm quality in males, reduced fertility in females, skewed sex ratio in populations, abnormalities of male sex organs such as cryptorchidism and hypospadias, endometriosis in females and precocious puberty. The effects of EDCs may be transmitted to future generations by germline epigenetic modifications such as DNA methylation and histone modifications.
EDCs are both natural and man-made, and include pesticides such as DDT [1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane], plasticizers such as bisphenol A [4,4'-dihydroxydiphenyldimethylmethane], pharmaceuticals such as ethinylestradiol found in birth control pills, industrial chemicals such as PBDEs [eg. 1-(2,3,4,5,6-Pentabromophenoxy)-2,3,4,5,6-pentabromobenzene] used as a flame retardant, or phthalates [eg. bis(1S,2R,4S-bornyl) phthalate] used in soft toys and in medical tubing. There are currently several hundred chemicals thought to act as EDCs.
In 2002 the World Health Organisation published an overview titled “Global assessment of the state-of-the-science of endocrine disruptors” in which it concluded that “evidence that wildlife have been affected adversely by exposures to EDCs was extensive” and, in the case of humans, suggestst that “low-level exposures to a number of chemicals with endocrine disrupting potential and the fundamental roles played by the endocrine system in maintaining homeostasis, make understanding the potential effects posed by exposure to these chemicals an obvious international priority”.
In June 2009 The Endocrine Society in the US, a professional society of endocrinologists and medical scientists, issued as scientific statement that concluded that “the evidence for adverse reproductive outcomes (infertility, cancers, malformations) from exposure to endocrine disrupting chemicals is strong, and [that] there is mounting evidence for effects on other endocrine systems, including thyroid, neuroendocrine, obesity and metabolism, and insulin and glucose homeostasis.” The Environmental Protection Agency in the US is currently (2010) undertaking an Endocrine Disruptor Screening Program to try and identify chemicals that impact on normal endocrine function. The National Institute of Environmental Health Sciences, part of the National Institutes of Health in the US, supports an ongoing research program into the effects of EDCs on human health
In South Africa scientific studies have shown a statistically significant correlation between the incidence of external urogenital birth defects in boys born to mothers who lived in areas where DDT was sprayed as an anti-malarial pesticide (see Bornman et al., 2009), and noted testicular abnormalities such as multiple intratubular dystrophic calcifications associated with significant levels of phenols or DDT metabolites in the fatty tissue of the Eland buck (see Bornman et al., 2010). |