The term « endocrine disruptors » has become familiar to us today, due to the abundance of publications in the press concerning Bisphenol (BPA) which is a compound used in plastic food packaging (bottles, the interior coating of drink cans), dental amalgams, children toys. We hear the acronym « ED » – these are “xenobiotics”, foreign chemical substances, not usually found in living organisms, mostly residues of human activity.
There is a strong suspicion of the implication of Endocrine disruptorsin in many current pathologies :
- fertility disorders,
- hormone-dependent cancers (breast, testicles, prostate),
- genital defects ((hypospadias, cryptorchidism),
- disorders of the metabolism (diabetes, obesity),
- certain behavioural disorders ( hyperactivity, autism)
An endocrine disruptor is a substance capable of interfering with the natural hormones of living organisms, human as well as animal. LHormones are chemical messengers which control multiple functions – metabolic, reproductive, cerebral. They are synthesized by the endocrine glands and transported by the blood system to different organs and tissues. They are active in low doses, as are endocrine disruptors. These hormones play an important and active role, particularly for the development of the foetus. According to different mechanisms of action, endocrine disruptors compete with natural hormones and cause potentially irreversible imbalance, depending on the window of exposure (the foetal phase, early childhood, puberty).
In 1977, the US Environmental Protection Agency defined ED’s as follows – « An exogenous agent which interferes with the synthesis, secretion, transport, metabolism, connection and elimination of natural hormones present in the organism which are responsible for the process of homeostasis, reproduction and development.»
Endocrine disruptors which are present in the environment
The first observations of ED’s were made in 1950, on wild fauna with reproductive disorders :
- sterility of the bald eagle (bird of prey), the minks of Michigan Lake, the Beluga whales of Saint-Laurent ;
- feminisation of males, presence of hermaphrodite fish noted in rivers and estuaries ;
- athrophied penis, low rates of testosterone and testicular disorder of the alligators of Lake Apopka (United States) ;
- sexual behavioural disorders (seagulls of the Channel Islands) ;
- genital defects : gastropods demonstrate aposex, hermaphrodite bass from the Seine estuary…
Different group of organochlorine substances are suspected, like DDT, PCB, Dicofol (an acaricide similar to DDT), tributyltin or TBT(anti-fooling paints for boat hulls), but also the residue of contraceptive pills or hormonal treatments which are evacuated into the water… These substances accrue for a long time in sediments and the water tables ; they are present and inventoried in all the ecosystems of the planet, as well as in humans. DDT residue has been found in shells from the Kerguelen Islands and in the sediments of the Rhône… BPA is present in all living organisms on the planet.
In 2001, the European Communities Commission noted at least 124 priority suspicious substances, and the list of substances with ED effects continues to rise. (Inserm/Afsset).
Human endocrine disruptors detected in humans
Blood samples from the umbilical cord of newborn babies have shown the presence of toxic and endocrine disruptors in utero (CordBloodReport, Canada 2013).
In the 1990s, two researchers, Sharpe and Skakkebaek, put forward the hypothesis that chemical substances present in the environment – xenoestrogens – may be able to interfere with hormones and cause reproductive disorders.
Certain of these substances are prohibited, but they continue to pollute the environment and infect the food chain. In fact, conventional toxicology models (one exposure dose = one physiological effect) are outdated, as are the notions of the limit below which there is no risk. . The example of Lake Apopka demonstrates the fact that even low doses, which are not detectable in lake waters, have a physiological effect on the reproductive system of alligators. Bioaccumulation and amplification phenomena reamain active throughout the food chain.
Even at very low doses, the exposure to xenobiotic endocrine disruptors during certain periods of life (fœtal, neonatal or prepuberty) is critical and presents a major risk for human health. Exposure during the fœtal and embryonic periods may cause gene methylation troubles, resulting in a reprogramming of gene expression in adulthood. Disorders may appear at birth, or at any other period of life, should the environment solicit the activation of this gene.
The distressingly infamous Distilbène® (Diethylstibestrol – a synthetic hormone with a high oestrogenic activity, known under the acronym DES – is an epidemiological model whose effects can be observed over 3 or 4 generations. Between 1950 and 1977 in France, 160,000 pregnant women – and about 4 million in the world – have been treated to prevent te risk of miscarriage. Different effects have been noted for the children and grandchildren of women for whom this medicine was prescribed – in girls: uterine malformations (T-shaped uterus), vaginal cancer, infertility and other reproductive disorders, repeated miscarriages… In boys : testicular hypotrophy, cryptorchidism (undescended testicles), oligospermia (decline of sperm quality), testicular cancer, and psychiatric disorders. Hundreds of scientific publications document this topic.
The impact of ED on human health
There are multiple effects. Individual sensitivity, predispositions, and the environmental context all play an important role in the development of pathologies resulting from endocrine disruptors. In other words, different people present different risks of developing ED-based pathologies.
First of all, we note reproductive disorders such as :
- inversion of the « sex-ratio » : more girls than boys born in populations exposed to certain of these substances ;
- sexual maturation disorders (early or late puberty) ;
- increase of the rate of testicular cancer (younger and younger men), breast cancer (younger and younger women), and prostate cancer ;
- decline of sperm quality, with a fall of 50% of the sperm rate over 50 years, accompanied by a loss of mobility ;
- 15% to 20% of infertility in couples (defined by the absence of conception beyond one attempt per year), and 6% of assisted births.
As well as other disorders such as :
- alterations of thyroid function leading to growth and development problems,
- alterations of the immune system,
- behavioural disorders : depression, schizophrenia, learning difficulties, fall in IQ, autism…
- metabolic diseases : diabetes, obesity,
- pro-inflammatory predisposition.
Bisphenol A is a highly-researched example of endocrine disruptors
Bisphenol A is part of the composition of plastics and epoxy resins; we find it in plastic packaging, bottles, the internal coating of drink cans and tinned food, dental amalgams, medical devices… It is water-soluble and migrates into food. In France, Bisphenol A is prohibited in food packaging for children. As regards adults, the law has been effective since 2015.
Numerous studies demonstrate the effect that this substance may have on living organisms by acting as a hormonal decoy. Below are some of the inventoried effects :
- significant decline of sperm quality in male mice, Vom Saal 1997 and 1998 ;
- breaching of the placental barrier, Schönfelder 2002 ;
- epigenetic effects : hypomethylation of genes involved in prostate cancer, Ho and Prinz, 2006, Sekizawa 2008 ;
- acceleration of the the development of adipocytes : risk factor for metabolic syndrome, Wada, Miyawaki 2007 ;
- responsible for the augmentation of prostate volume in men, and early puberty in young girls, NTP 2008 ;
- a correlation has been established between the risk of developing breast cancer and BPA exposure in primates at a concentration of 400μg/J/kg, during last two months of pregnancy, and a higher density of the mammary glands in descendants, Soto 2012 ;
- behavioural disorders in rats at very low doses, Bouskine 2009 ;
- decreases the efficiency of certain anticancer medicines, Lapensée 2011 ;
- the effects vary depending on the dosage and the window of exposure, Vandenberg 2012 ;
- also acts on on cell membrane receptors, Fenichel 2012 ;
- effects noted from 10 μg/day; the average daily consumption of tinned products represents around 8,3 μg/day, Rudel 2006.
How to act to protect your health ?
Of course, the first step consists of identifying the sources of domestic exposure (essentially cosmetics and dietary), and reducing them. A healthy lifestyle, a balanced diet, consumption of seasonal and local fruits and vegetables also reduce risks. Regular exercise and periods of seasonal detoxification help to eliminate accumulated toxins and toxic manifestations ; they limit the accumulation and storage of these harmful substances which, over time, saturate our organism.
For more information
http://www.youtube.com/watch?v=X4e1cCpKNkw : perturbateurs endocriniens et origine fœtale des pathologies, entretien avec le Professeur E. Burgio, pédiatre spécialisé dans l’épigénétique