Alarmerend
bericht over de stof Bisphenol A (BPA), aanwezig in allerlei toepassingen.*
De
chemische stof BPA die wereldwijd op grote schaal toegepast wordt in allerlei
producten zoals o.a. CD’s, GSM’s, groentenblikken, plastic flessen,
waterleidingen en zelfs tandvullingen geeft negatieve gevolgen voor de
ontwikkeling van hersenen zelfs zoals nu blijkt al in zeer lage dosering.
Al
langer is bekend dat BPA in het lichaam reageert als het hormoon oestrogeen en
daardoor ontwikkelingsproblemen kan veroorzaken en een verhoogd risico geeft
voor borst- en prostaatkanker. Uit deze studies nu blijkt dat zelfs een zeer
lage dosis van BPA de ontwikkeling van hersenen zowel bij een foetus als de
eerste jaren van een baby danig kan verstoren. Deze zeer lage dosis bleek in
eerdere studies gewoon aanwezig te zijn in bijv. drinkwater. BPA dat in de
chemische industrie gebruikt wordt om polymeren om te zetten tot polycarbonaten
en epoxyharsen wordt wereldwijd op grote schaal toegepast waardoor in het milieu
steeds meer restanten gevonden worden, die zoals nu blijkt grote gevolgen kunnen
hebben. Ondanks de hoeveelheid aan studies over BPA is nog geen enkele overheid
ertoe overgegaan BPA te verbieden terwijl er voldoende oplossingen zijn om
plastic te maken zonder BPA.
Bisphenol
A Used In Food Containers Disrupts Brain Development
The chemical bisphenol A (BPA), widely used in products
such as food cans, milk container linings, water pipes and even dental sealants,
has now been found to disrupt important effects of estrogen in the developing
brain.
A University of Cincinnati (UC) research team, headed by Scott Belcher, PhD,
reports in two articles in the December 2005 edition of the journal
Endocrinology that BPA shows negative effects in brain tissue "at
surprisingly low doses."
The research was supported by funding from the National Institutes of Health and
the Pediatric Brain Tumor Foundation.
"These new studies are also the first to show that estrogen's rapid
signaling mechanisms are active in the developing and maturing brain in regions
not thought to be involved with sexual differences or reproductive functions,"
Dr. Belcher said.
BPA has often been implicated in disease or developmental problems.
Long known to act as an artificial estrogen, the primary hormone involved in
female sexual development, BPA has already been shown to increase breast
cancer cell growth, and in the January 2005
edition of the journal Cancer Research, another UC research team reported that
it increased the growth of some prostate cancer cells as well. Warnings about other
possible long-term health risks associated with fetal exposures to BPA have also
been discussed in recent scientific literature.
"BPA molecules are linked into polymers used to create polycarbonate
plastics and epoxy resins that are widely used in many products," said Dr.
Belcher, an associate professor in the pharmacology and cell biophysics
department at UC College of Medicine. "While plastics are typically thought
of as being stable, scientists have known for many years that the chemical
linkage between BPA molecules was unstable, and that BPA leaches into food or
beverages in contact with the plastics."
Dr. Belcher and his colleagues worked with rats at a period in their development
equivalent to the third trimester of human fetal development through to the
first few years of childhood.
Although best known for its function as a female sex hormone, Dr. Belcher
explained, estrogen also has very important roles in the developing brain of
both males and females.
In the absence of estrogen, Dr. Belcher said, BPA alone was found to mimic the
actions of estrogen in developing neurons, and very low doses of BPA completely
inhibited the activity of estrogen. Because estrogen normally increases the
growth and regulates viability of developing neurons, he said, these results
support the idea that BPA may harm developing brain cells.
In fact, Dr. Belcher said, while high doses cause little effect, analysis of
cellular and molecular markers of estrogen signaling revealed that near-maximal
effects of BPA on rat brain neurons not only occurred "at surprisingly low"
doses of 0.23 parts per trillion, they also happened in a matter of minutes.
"From other studies it's clear that these low concentrations are in line
with human fetal exposures, and at levels one might even see in the water supply,"
said Dr. Belcher.
This "low-dose" effect of BPA is troubling, Dr. Belcher points out,
since its maximal effects occur at the level typical of human exposure. This
means that the harmful effects of BPA could easily be missed using standard
approaches for determining the risks of chemical exposure.
"These are important considerations in view of the widespread presence of
low concentrations of BPA in the environment," said Dr. Belcher.
In earlier research, which showed estrogens could control the survival of
maturing neurons in the brain region involved in movement and coordination, Dr.
Belcher and his co-workers found the effects of estrogen were the same in both
males and females.
"Estrogen's actions on these neurons appear to be a double-edged sword,"
he said. "During certain periods of development estrogen can kill specific
subsets of neurons, but at a later developmental stage it actually appears to
increase their viability." Disruption of either of these actions of
estrogen could be considered potentially harmful, he added.
"We have now shown that environmental estrogens like BPA appear to alter,
in a very complicated fashion, the normal way estrogen communicates with
immature nerve cells," Dr. Belcher explained. "The developmental
effects that we studied are known to be important for brain development and also
for normal function of the adult brain," he said.
What remains unclear, he said, is how inappropriate hormone signaling, or
blocking the normal signaling at a critical time during development, will
influence later life.
In the face of more than 100 studies published in peer-reviewed journals showing
the detrimental effects of BPA, Dr. Belcher said, the chemical industry and
federal regulatory agencies have resisted banning BPA from plastics used as food
and beverage containers, despite the fact that plastics free of BPA and other
toxic chemicals are available.
David Bracey
david.bracey@uc.edu
University of Cincinnati
http://www.uc.edu/news
(December
2005) (Opm.
Hoe lang zal het nog moeten duren voordat de overheden hun
verantwoording nemen om simpel BPA te verbieden? En waarom, alternatieven zijn
zo voor handen. Het zal nog wel lang duren want om de huidige Europese
norm van 0,6 mg/kg voor drinkgerei voor kinderen te verlagen naar 0,03 mg/kg is
men al jaren bezig. In de tussentijd kunnen wij zelf beter opletten, als dat al
mogelijk is, bij wat we aanschaffen.)
