Endocrine disrupters and Prostate Enlargement and low sperm counts
Observation of wildlife also provided evidence for the effects of endocrine disruptors on reproductive health. Various publications described how chemicals suspected to have endocrine-disrupting effects, including DDT, dioxins, polychlorinated biphenyls (PCBs), which are all banned, and various pesticides and fungicides, caused a wide range of reproductive disorders and deformities of sexual organs among wild animals in polluted areas. Nonylphenol, a degradation product from many detergents, herbicides, spermicides and cosmetics, has been shown to cause imposex in oysters, which is a pseudo-hermaphroditic condition in which females acquire male sex characteristics (Nice et al, 2003). Scientists in the UK found that oestrogenic compounds in human and agricultural wastewater triggered the feminization of male fish in British lakes and rivers. Else-where, US scientists found that female mosquito fish in Florida exposed to pulp-mill effluent developed a gonopodium, an organ normally found only in males. Similarly, male alligators in various contaminated lakes in Florida suffered from phallus deformations and an impaired immune system. Half of male carp caught in the Tama River in Japan were found to produce unusually large amounts of the yolk precursor protein vitellogenin, specific to female fish.
In 1996, Colborn, together with science writers Dianne Dumanoski and John Peterson Myers, compiled these observations into the book Our Stolen Future and drew a straight line between the effects observed in wild animals and human health effects, including breast and prostate cancer and decreasing male fertility caused by decreasing sperm counts, cryptorchidism (where one or both testicles fail to descend from the body) and hypospadias (deformation of the phallus). Often compared to Rachel Carson's Silent Spring, Colborn's book had an enormous impact on public opinion and triggered intense media coverage about the suspected epidemic of cancers and male infertility.
Bisphenol A (BPA), a commonly used compound found in many plastics, caused abnormal prostate growth and decreased sperm production in rats at doses far lower than those considered to be safe health advocates who seek to ban chemicals such as BPA because they can exert their toxic effects at extremely low doses.
In fact, a series of studies that closely investigated the original publications claiming an increase in breast and prostate cancer and a decline in male fertility found that this is not so
Indeed, the evidence of detrimental effects of endocrine disruptors in animals, particularly for aquatic organisms, is quite convincing, Sharpe maintained. He cited the example of TBT (tributyltin), widely used in ship paint. The chemical does not bind to a hormone receptor but modulates the endogenous hormonal milieu in mussels elsewhere to cause imposex. Consequently, as the human fetus is "kind of an aquatic organism," as Sharpe put it, such chemicals could potentially impair prenatal development and cause effects later in life. But "humans are different from fish," Safe countered, and he questioned the sense of extrapolating observations made in wild or laboratory animals to humans, who often have very different hormonal metabolisms. "There isn't a single chemical that doesn't have an effect," he said, but "what are these animal studies telling us?" Witorsch agreed that making such assumptions is like "shooting from the hip". "To judge in utero effects in rodents and try to extrapolate them to humans has to be done with caution," he said. "An observation doesn't mean that you should ban a substance and a lack of observation doesn't necessarily mean that it is safe."
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