Xenoestrogens are part of a heterogeneous group of chemicals that are hormonally active agents. They differ from phytoestrogens (estrogenic substances from plants), mycoestrogens (estrogenic substances from fungi, which can be considered as one type of mycotoxin), and pharmacological estrogens (estrogenic action is intended) in that they are man-made and their effects are unintended. Estrogens from a variety of sources may have a cumulative effect upon living organisms, and xenoestrogens may be part of a larger picture of a process of estrogenisation of the environment. Xenoestrogens have been introduced into the environment by industrial, agricultural and chemical companies in only the last 70 years or so, but similar compounds have existed in the environment since the beginnings of life itself. (see phytoestrogens)
In a study by Sharpe and Shakkeback, published in the respected scientific journal, The Lancet in 1993, the researchers attributed the incidence of falling sperm counts in males to increased oestrogen exposure in utero.
Another issue is the potential effect of xenoestrogens on oncogenes, specifically in relation to breast cancer. Some scientists doubt that xenoestrogens have any significant biological effect, in the concentrations found in the environment.
A 2005 study by Belcher and coworkers demonstrated that even very low levels of a xenoestrogen, in this case Bisphenol A, could affect fetal neural signalling more than higher levels (PMID 16123166), indicating that classical models where dose equals response may not be applicable in susceptible tissue. As this study involved intra-cerebellar injections, its relevance to environmental exposures is unclear.
Antiestrogens Inhibit Xenoestrogen-Induced Brain Aromatase Activity but Do Not Prevent Xenoestrogen-Induced Feminization in Japanese Medaka (Oryzias Latipes)
Apr 01, 2006; In fish, exposure to estrogen or estrogen-mimicking chemicals (Xenoestrogens) during a critical period of development can...
Combining Xenoestrogens at Levels below Individual No-Observed-Effect Concentrations Dramatically Enhances Steroid Hormone Action. (Articles)
Sep 01, 2002; The low potency of many man-made estrogenic chemicals, so-called Xenoestrogens, has been used to suggest that risks...