| Wikipedia: Xenoestrogen |
Xenoestrogens are novel, industrially made compounds, that have estrogenic effects and differ chemically from archiestrogens (ancient, naturally occurring) produced by living organisms. Their potential ecological and human health impact is under study.[1]
As a heterogeneous group of chemicals that are hormonally active agents xenoestrogens differ from phytoestrogens (estrogenic substances from plants) and mycoestrogens (estrogenic substances from fungi, which can be considered as one type of mycotoxin), and can be divided into pharmacological estrogens (estrogenic action is intended in ethinyl estradiol) and in agents that have an unintended estrogenic effect. 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 and consumers only in the last 70 years or so.
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Effects
Xenoestrogens have been implicated in a variety of medical problems, and while there has been little hard evidence of damage, the potential for adverse effects is considered real.[2] Foremost is the concern that xenoestrogens as false messengers disrupt the process of reproduction. Xenoestrogens have an effect similar to that of naturally produced estrogen and can increase growth of the endometrium, so treatments for endometriosis include avoidance of products which contain them. Likewise, they are avoided in order to prevent the onset or aggravation of adenomyosis. Studies have implicated observations of disturbances in wildlife with estrogenic exposure. Reproductive issues which are of concerns in humans are fetal exposure (perhaps leading to hypospadias) and decreased reproductive ability in men (i.e. decrease in sperm numbers).
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.[3]
Presence
The ubiquitous presence of such estrogenic substances is a significant health concern, both individually and for a population. Life relies on the transmission of biochemical information to the next generation, and the presence of xenoestrogens may interfere with this transgenerational information process through "chemical confusion" (Vidaeff and Sever),[4] who state: "The results do not support with certainty the view that environmental estrogens contribute to an increase in male reproductive disorders, neither do they provide sufficient grounds to reject such a hypothesis."
A 2008 report demonstrates further evidence of widespread effects of feminizing chemicals on male development in each class of vertebrate species as a worldwide phenomenon.[5] Ninety-nine percent of over 100,000 recently introduced chemicals are poorly regulated.[5]
Agencies such as the United States Environmental Protection Agency and the World Health Organization International Programme on Chemical Safety are charged to address these issues.
Research
Believers that environmental estrogen disruption is a major health hazard are opposed by detractors who argue that observed effects are spurious and inconsistent, or that the quantities of the agents are too low to have any effect.[6] A 1997 survey of scientists in fields pertinent to evaluating estrogens found that 13 percent regarded the health threats from xenoestrogens as "major," 62 percent as "minor" or "none," and 25 percent were unsure. [7]
In a 1993 study Sharpe and Shakkeback attributed the incidence of falling sperm counts in males to increased oestrogen exposure in utero.[8] Sharpe in a 2005 review indicated that external estrogenic substances are too weak in their cumulative effects to alter male reproductive functioning, but indicates that the situation appears to be more complex as external chemicals may affect the internal testosterone-estrogen balance.[9]
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, indicating that classical models where dose equals response may not be applicable in susceptible tissue.[10] As this study involved intra-cerebellar injections, its relevance to environmental exposures is unclear.
Chemicals shown to have estrogenic effects
- Alkylphenol
- atrazine (weedkiller)
- 4-Methylbenzylidene camphor (4-MBC) (sunscreen lotions)
- butylated hydroxyanisole / BHA (food preservative)
- bisphenol A (monomer for polycarbonate plastic and epoxy resin; antioxidant in plasticizers)
- dichlorodiphenyldichloroethylene (one of the breakdown products of DDT)
- dieldrin (insecticide)
- DDT (insecticide)
- endosulfan (insecticide)
- erythrosine / FD&C Red No. 3
- ethinylestradiol (combined oral contraceptive pill) (released into the environment as a xenoestrogen)
- heptachlor (insecticide)
- lindane / hexachlorocyclohexane (insecticide)
- metalloestrogens (a class of inorganic xenoestrogens)
- methoxychlor (insecticide)
- nonylphenol and derivatives (industrial surfactants; emulsifiers for emulsion polymerization; laboratory detergents; pesticides)
- polychlorinated biphenyls / PCBs (in electrical oils, lubricants, adhesives, paints)
- parabens (lotions)
- phenosulfothiazine (a red dye)
- phthalates (plasticizers)
- DEHP (plasticizer for PVC)
- Propyl gallate
See also
- Diethylstilbestrol (obsolete pharmacological estrogen)
- Endocrine disruptor
- Epidemiology and etiology of breast cancer
- List of breast carcinogenic substances
- Phytoestrogens
- SULT2B1
- Xenobiotic
References
- ^ Korach, Kenneth S. (1998). Reproductive and Developmental Toxicology. Marcel Dekker Ltd. pp. 278–279, 294–295. ISBN 978-0824798574.
- ^ Evidence of effects of environmental chemicals on the endocrine system in children PMID 12837917
- ^ Environmental endocrine modulators and human health:an assessment of the biological evidence PMID 9557209
- ^ Vidaeff AC and Sever LE, In-utero exposure to environmental estrogens and male reproductive health. PMID 15808781
- ^ a b It's official: Men are the waker sex 7 December 2008. The Independent.
- ^ Endocrine disruptors and human health. Is there a problem? Toxicology 2004 PMID 15458784
- ^ Lichter, SR., Murray, DW. Correspondence. New England Journal of Medicine. 1998 April 2;338(14):988-991.
- ^ Sharpe RM, Skakkebaek NE. "Are oestrogens involved in falling sperm counts and disorders of the male reproductive tract?". Lancet. 1993 May 29;341(8857):1392-5.. PMID 8098802.
- ^ Sharpe RM. "The 'oestrogen hypothesis'- where do we stand now?". Int J Androl. 2003 Feb;26(1):2-15.. PMID 12534932.
- ^ A.Zsarnovszky A, Le HH, Wang HS, Belcher SM. "Ontogeny of rapid estrogen-mediated extracellular signal-regulated kinase signaling in the rat cerebellar cortex: potent nongenomic agonist and endocrine disrupting activity of the xenoestrogen bisphenol". Endocrinology. 2005 Dec;146(12):5388-96.. PMID 16123166.
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