Title: Environmental Estrogens Ethinyl Estradiol and Bisphenol' Are we drowning in a Sea of estrogens or, i
1Environmental Estrogens Ethinyl Estradiol and
Bisphenol. Are we drowning in a Sea of
estrogensor, is this Estro-Phobia?
- L. Earl Gray Jr., PhD Senior Reproductive
Biologist and Toxicologist Reproductive
Toxicology Branch US Environmental Protection
Agency - This presentation does not necessarily reflect
USEPA policy, but rather represents the authors
current view on the state of the science
2Outline
- Our research Program on Endocrine Disrupting
Chemicals - Estrogens in aquatic systems and effects on fish
- Bisphenol A the controversy
- The press and advocates say it is dangerous
- Most regulatory agencies say current exposure
levels are safe - Compare in vitro and in vivo studies on BPA
versus the drug Ethinyl Estradiol (EE2) which
also is an environmental estrogen - My level of concern about BPA
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5Our research on Endocrine Disrupting Chemicals
(EDCs)
- Identify the cellular and molecular mechanisms of
abnormal reproductive development - Developed in vitro assays for these studies and
for screening estrogens and androgens, including
water samples - CAFOs (concentrated animal feedlot effluents) and
other effluents - Global Water Research Coalition (GWRC) assessed
the utility of various assays to screen for the
presence of estrogenic chemicals in water
samples. - Screening drinking water samples for
estrogenicity in South Africa - USEPA Tier 1 Screening Battery for EDCs
6Why screen for estrogens?There are Valid
Concerns about Estrogens in aquatic systems
- Ethinyl estradiol (EE2) is a common contaminant
of aquatic systems from human pharmaceutical
usage - Effluents also may contain natural estrogens like
estradiol and estrone and occasionally
alkylphenols - Exposures to estrogens as estrogen-equivalents
(EEQs) of 0.3 ng/L feminize fish. 1 to 5 ng/L can
cause infertility. (Tyler and Jobling, 2008) - 5.7 of 139 US streams had gt5 ng/L EEQs (Kolpin
2002) - Less data on levels of EEQs in drinking water
- In contrast, no known adverse effects of BPA in
aquatic systems
7Widespread disruption of male fish by estrogens
in the UK (Tyler and Jobling. 2008. Bioscience)
8Why are some people so concerned about BPA?
Concern has been elevated by statements from
advocates of banning BPA like the following
- "The science is clear and the findings are not
just scary, they are horrific," (name removed). l
said. "When you feed a baby out of a clear, hard
plastic bottle, it's like giving the baby a birth
control pill. - However, BPA does not cause infertility at any
dose level in animal studies
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10Several governmental agencies have conducted risk
assessments on the potential effects of BPA on
human health, for example.
- UK Committee on Toxicology 2001
- European Food Standards Agency 2005
- National Toxicology Program and the NTP CERHR BPA
Expert Panel which advised the NTP - FDA draft 2006 the current controversy
11UK COT comments on low dose reports of effects of
BPA (2001)
- The Committee considers that it is not
appropriate, at this time, to base human health
risk assessment on these reports, for several
reasons. - Firstly, it is not known whether the reported
effects are transient or irreversible. - Secondly, the functional significance of the
reported effects is unknown, ... - Thirdly, the observations of low-dose effects of
BPA are not robust, in that they cannot be
independently reproduced in other competent
laboratories. - Fourthly, other chemicals that can induce subtle
effects on the developing reproductive organs
inevitably cause more gross defects at higher
doses, whereas BPA shows no such gross
developmental toxicity. - The European Food Standards Agency reiterated
these comments after reviewing the new data in
2006
12http//cerhr.niehs.nih.gov/chemicals/bisphenol/bis
phenol.html
- NTP CERHR Expert Panel
- Review of
- Bisphenol A
13Literature reviewed
14What a review of these studies of BPA revealed
- A significant percentage of studies failed to
meet minimum standards for experimental design
and analysis - Among Adequate studies, BPA had not caused
- Cancer of the prostate, breast or any other
tissue. - It is not mutagenic
- Reproductive malformations
- Infertility
- Or consistently (at low dosage levels)
- Alter prostate weight or the weight of any
androgen-dependent tissue - Alter hormone levels
- Lower sperm counts
- Alter puberty in male or female rats or male mice
- Cause Obesity
- NTP-CERHR expert panel report on the reproductive
and developmental toxicity of bisphenol A. Birth
Defects Res B Dev Reprod Toxicol. 2008
Jun83(3)157-395. Chapin RE, Adams J,
Boekelheide K, Gray LE Jr, Hayward SW, Lees PS,
McIntyre BS, Portier KM, Schnorr TM, Selevan SG,
Vandenbergh JG, Woskie SR.
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16Human Exposures
EPAs oral reference dose (RfD) is 50 µg/kg/day
17BPA levels in water samples(Chapin et al, 2008.
Birth defects research NTP CERHR BPA Expert
Panel Final report, 2007)
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20Is there a Biologically Plausible Mechanism to
explain how BPA might induce adverse effects at
low doses?
21BPA is a million-fold less potent than is ethinyl
estradiol (EE2) in inducing ER-dependent gene
expression in vitro.
BPA ER gene expression
EE2 ER gene expression
22Effects of Ethinyl Estradiol (EE2) and BPA given
orally or sc on uterine weight in immature female
rats (data from published OECD interlab studies).
Orally, BPA displays partial agonist activity at
a dose a million fold higher than the ED50 of EE2.
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24Administration of BPA in utero, during lactation
and after weaning does not accelerate the age of
puberty in female rats over a broad dose range
25Standard in vitro and in vivo assays used to
detect estrogenic activity reveal the BPA is a
very weak estrogen.
Recently, it has been proposed that BPA act at
low concentrations with GPR30 and membrane ERs,
however, the role of these receptors in
reproduction, if any, is unknown.
26What our study reveals about the reproductive
effects of EE2 and BPA in male and female rats
after exposure in utero and during lactation via
the dam.
27BPA had no effect
28EE2 reduces maternal weight gain and litter sizes
at birth, BPA does not
29EE2 permanently reduces F1 male body, prostate,
seminal vesicle and testis weights and sperm
counts, BPA does not
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31EE2 accelerates the age at puberty, BPA does not
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33EE2 exposure during fetal and neonatal life
reduced fecundity in F1 female rat offspring.
BPA did not
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35The robust, comprehensive multigenerational
studies in rats are mice are consistent. BPA
dose not produce adverse effects at low dosage
levels.
36Conclusions about low dose effects - EE2 versus
BPA
- Biological plausibility of the mechanism of
action at low dose levels - Ethinyl estradiol is a very potent synthetic
estrogen - Doses as low as 10 µg/day are effective in girls
Doses as low as 0.2-1 µg/day are effective in
rats - BPA is far too weak an environmental estrogen for
binding to the ERs alpha and beta that act a
nuclear transcription factors to account for any
low dose effects. - Some other proposed mechanisms of action have no
known role in reproductive development or
reproductive function (GRP30 and membrane ERs).
37Conclusions about low dose effects - EE2 versus
BPA Toxicity
- When EE2 is administered at doses equivalent to
pharmacologically effective levels in humans
administered to the mother rat in utero and
during lactation, EE2 causes - Maternal and neonatal effects
- Reduced maternal weight gain
- Reduced offspring viability
- Female rat offspring display
- Accelerated age at puberty
- Reproductive tract malformations
- Infertility and abnormal estrous cyclicity
- Alterations (defeminization) of some sexual
dimorphic behaviors - Male rat offspring display
- Reduced sperm counts
- Histopathological alterations of prostate and
seminal vesicles - Permanent reductions in reproductive organ
weights - Bisphenol A does not produce adverse effects in
multigenerational studies in rats or mice at low
dosage levels
38Conclusions about low dose effects - EE2 versus
BPAExposure
- Wildlife
- EE2 exposures in aquatic systems are a problem in
aquatic ecosystems at 1 ng/L and above - BPA exposures in such systems has not been
associated with any adverse effects - Humans
- EE2 exposures from drinking water and etc are not
yet well characterized - Total BPA exposures from all sources are in the
50-80 ng/kg/d (median from biomonitoring data)
with a max of about 3.5 micrograms/kg/d. (NTP
monograph) - Total BPA in drinking water was below the MDL in
2/3 samples and 2-5 ng/L in a third (0.2-0.5
ng/kg/d for a 10 kg child drinking 1 L) (NTP
monograph) - Human BPA exposures are well below the EPAs RfD
of 50 micrograms/kg/d
39Our USEPA Research Team
- Multigenerational studies
- Dr LE Gray Jr
- Johnathan Furr
- Fetal endocrine and genomic studies
- Dr Kembra Howdeshell
- In vitro mechanistic studies and assay
development - Dr Vickie Wilson
- Dr Dieldrich Bermudez
- Ms Christy Lambright
- Dr Phillip Hartig
- Ms Mary Cardon
40The End
41BPA and estrogen in 139 streams (Kolpin et al
2002)
42- A FACA committee An Official advisory committee
to a governmental agency - FACA rules require
- No conflict of interest
- Public comment
- Open meetings
- Objectivity of the participants
- The Final report represents the opinion of ALL of
the participants, consensus or not. - Prevent special interest groups from unduly
influencing the government
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44World Health Organization EDC Definition
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47Estrogenic potential of BPA in in vitro and
short-term in vivo assays
48 49Experimental design and statistical issues
50Routes of Exposure
51BPA does not cause Obesity in rodents
52Obesity page 2
53- BPA does not consistently affect T or LH levels
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55Effects are small, transient and not necessarily
adverse
One dose level, Small sample size, No dose
response, Poor design
U shaped dose response for BPA not demonstrated
Result contrary To effects in recognized Guideline
studies
Lack of reproducibility Of low dose effects
56Bisphenol A