Post on 16-Dec-2015
Bisphenol A: Exposure in the Environment as it
Relates to Health
Candace Waynick, RD LDOctober 24, 2011
NUTN 507: Seminar
Objectives
Discuss the synthetic and legal history of Bisphenol A (BPA)
Describe uses of BPA and BPA containing products
Discuss harmful effects of exposure to BPA and controversial methods of testing
Describe the role of dietitians to minimize public health risks associated with BPA
Synthetic History2 phenol compounds and 1 acetone
Recognized for estrogenic properties in 1930’s by Edward Charles Dodd searching for the “mother substance” (synthetic estrogen)
In the 1950’s, BPA is used to synthesize epoxy resins and polycarbonate plastics
Superiority to glass and steel
Vogel 2009Braun et al 2011Biello 2008Image: Wikipedia
Epoxy Resins
BPA is a monomer in synthesisProducts:
Protective coatings of medical equipment, piping, steel drums, and interior of food/beverage/liquid infant formula cans
Vogel 2009Groff 2010US FDA Update 2010Taylor 2011Image: http://news.consumerreports.org/a/6a00d83451e0d569e20120a69fcb0e970c-800wi
Polycarbonate (PC) plastics
Hard plastic formed when BPA is polymerized
Products:Electronics, safety equipment,
automobiles, food containers, plastics with recycling code # 7, intravenous tubing, dental sealant, reusable water and baby bottles
Vogel 2009Groff 2010US FDA Update 2010Image: http://www.pacebutler.com/images/recycle/plastic-recycling-symbols-7.jpg
Thermal (Carbonless) Paper
Also contains BPA causing transdermal exposure
Products:Sales receipts, cigarette filters,
lottery tickets, fax paper, children’s books, and recycled paper products
Groff 2010US EPA DRAFT 2011Braun 2011Taylor 2011Image: http://www.bikudo.com/preview/292638.jpg
Leaching BPAMonomers of BPA can hydrolyze and leach
into foods or liquidsAccelerated by:
High temperaturesAcidic or basic conditionsDamaged surfaces
Le et al studyExposure to 100
。C (new and used PC water bottles)
allowing 24 hrs to cool to room temperatureResults: 15-55 fold increase in those exposed to heat
versus room temperature water onlyGroff 2010Braun et al 2011Biello 2008Le 2008
Federal Regulation1958- FDA approves BPA as indirect food
additiveSafety determined by toxicity, not carcinogenicity
1977- National Cancer Institute (NCI) initiated 1st carcinogenesis study of BPA due to increased productionResponsibility of program passed to the National
Toxicology Program (NTP) during 2 year study1988- Environmental Protection Agency
(EPA) defines safe exposure levels to BPA as 50 micrograms/kg body weight
Vogel 2009Shaw 2008
Health Implications
Endocrine system disruption
CancerObesityCognitive and
behavior impairment
Cardiovascular Disease (CVD)
Type 2 Diabetes (DM2)
AsthmaLiver enzyme
abnormalities
Shaw 2008Ballard 2010Image: http://bpafreewaterbottlespro.com/wp-content/uploads/2011/08/bpa-health-risks.jpg
Endocrine System Disruption
BPA is an endocrine-disrupting compound (EDC)An exogenous agent that interferes with
synthesis, secretion, transport, metabolism, binding, action, or elimination of natural blood-borne hormones that are present in the body and are responsible for homeostasis, reproduction, and developmental processes.
Bourguignon et al 2010
Studies showing BPA as EDC
Moriyama et al (2002) show BPA inhibiting thyroid hormone receptor (T3)-mediated transcription by acting as an antagonist
Ramos et al (2003) exposed rats to BPA in utero indicating prenatal exposure induces transient and permanent age-dependent alterations in the male reproductive axis at different levels
Moriyama et al 2002Ramos 2003Image: http://electiondebates.com/images/stimulus-pix/rats.png
Studies showing BPA as EDC
Song et al (2002) demonstrate BPA inducing NR4A1 gene expression (responsible for activating steroidogenesis) in mouse testicular cells
Akingbemi et al (2004) actually show the opposite with low doses of BPA showing an inhibitory effect on testicular steroidogenesis
Song et al 2002Akingbemi et al 2004
Metabolic disturbances
Lang et al use NHANES data to show higher BPA urine levels associated with increased prevalence of CVD, DM2, and liver-enzyme abnormalities
Lang et al 2008US EPA DRAFT 2011Image: http://www.online-diabetes-information.com/wp-content/uploads/2011/03/diabetes-heart-disease2.jpg
Young children, infants, and fetuses at higher risk
Higher BPA concentrations reflective of higher food intake per pound of body mass
Predominant sources:Fetus- shown to cross the placentaInfants- breast milk, canned infant formula,
and baby bottlesNICU infants exposed to higher levels due to
intensive medical interventionsChildren- canned food and beverages and
school lunchesGroff 2010Lang et al 2008Bourguignon et al 2010US EPA DRAFT 2011Image: http://www.sequoiapediatricgroup.com/images/nicu_baby.gif
Exposure outcomes during development
Prenatal exposure associated with aggression and hyperactivity in 2 year old children
Delayed breast development with higher BPA concentrations
More sensitive to adverse outcomes due to exposure during development of neurological and endocrine systems US EPA DRAFT 2011
Bourguignon et al 2010US FDA Update 2010Braun et al 2011
National Children’s StudyStarted 2009Examining fetal environment,
including BPA exposureFollowing pregnant women and
offspring until 21 years of ageGoal of 100,000 children
participantsLargest, most comprehensive study
of its kind in US
Groff 2010Image: http://www.mrothery.co.uk/images/growth.gif
Metabolism
Oral ingestion of BPA is metabolized in the intestines and liver to yield metabolite, BPA monoglucuronide, and is excreted in the urine (in humans)
Acute exposure studies show: rapid metabolism of BPA with urinary
elimination to be within 24 hours of exposure based on 4-6 hour half-life
Stahlhut 2009Lang et al 2008Image: http://image3.examiner.com/images/blog/wysiwyg/image/water_bottle1(1).jpg
Metabolism Controversy
BPA monoglucuronide elimination: humans/primates- from the blood via
kidneys into urine Rodents- bile excretion into feces
Current safety measured on belief that higher doses result in greater effectsIf higher doses cause no harm, lower
doses are deemed safe?Groff 2010Lang et al 2008Taylor et al 2011
Studies Addressing Controversy
Stahlhut et al suggest a longer than expected half life attributed to either environmental exposure or accumulation in adipose tissue
Taylor et al compare bioactive BPA (unconjugated) levels in primates and rodents reporting clearance rates are the same
Stahlhut et al 2009Taylor et al 2011Groff 2010Image: http://maxcdn.fooyoh.com/files/attach/images/3004/141/953/004/Monkey_facepalm.jpg
ExposureOver 90% of U.S. individuals have
measurable concentrations of BPA in their urineSignificantly higher levels of BPA in
younger children, women, and incomes < $45,000/year
1997-2005- 115 studies in US, Japan, and Europe show some effects at or below the reference dose
Braun et al 2011Lang et al 2008Groff 2010Taylor 2011Vogel 2009Image: http://3.bp.blogspot.com/_xo0o9nT5MLI/TOq_bZElPYI/AAAAAAAAAB8/nQspiA_mtwY/s1600/MP900431826.JPG
Back to Federal Regulation2007- Chapel Hill Consensus Statement
BPA, at concentrations found in the human body, is associated with “organizational changes in prostate, breast, testes, mammary glands, body size, brain structure and chemistry, and behavior of laboratory animals.”
2008- The Center for Evaluation of Risks to Human Reproduction (CERHR) within the NTP released two statements regarding BPA at current exposure:“some concern for effects on the brain, behavior, and prostate
gland in fetuses, infants, and children”“minimal concern for the effects on the mammary gland and an
earlier age for puberty for females in fetuses, infants, and children”
Vogel 2009US FDA Update 2010Image: http://www.knowabouthealth.com/wp-content/uploads/2010/07/BPA.jpg
Current Regulation of BPAJanuary 2010- Food and Drug Administration
announces it had some concern about BPANovember 2010- World Health Organization
recommend holding off on regulations that limit or ban use of BPA
Several local and state governments in US have limited or banned use of BPAOregon Senate Bill:
http://gov.oregonlive.com/bill/2011/SB695/October 2011- American Chemistry Council
asks to phase out allowance of BPA in baby products
US EPA 2010Brown 2010USA Today 2011
BPA-free Manufacturers
By March 2009, major baby bottle companies removed BPA from products
Sunoco requires written confirmation of BPA plastic not sold to children ≤ 3 years
2010- General Mills announced next tomato harvest, all Muir Glen tomatoes canned BPA-free
Eden Foods beans have been BPA free since 1999
Vogel 2009Szabo 2008USA Today 2011Image: http://www.kidsbabydesign.com/wp-content/uploads/2009/06/bpa-free-baby-bottles.jpgImage: http://www.greenbiz.com/sites/default/files/imagecache/wide_large/0410Muir.jpg
Minimizing Health RisksRudel et al conducted a study
following participants measuring BPA at baseline and 3 days post intervention (eliminating canned/packaged foods) 50-70% decrease in urinary BPA
Rudel et al 2011Image: http://3.bp.blogspot.com/_4J97xRX7uok/TG4Bj2OHSII/AAAAAAAAAAk/DOb-TqhLJh0/s1600/Fresh+foods+vs+Canned+foods.png
Role of the DietitianCounsel public to:
Avoid canned foodsReplace recycling #s 3, 6, & 7 with other
recycling #s (1, 2, 4, or 5), stainless steel, or glassware
Switch from liquid formula to powderedAvoid heating BPA plasticReplace canned foods with fresh or frozen foodsDiscard scratched baby bottles/cupsOnly use dishwasher safe and microwave safe
plastics in appliances
Braun 2011Groff 2010Bourguignon 2010US DHHS
Summary
BPA found in plastics (code # 7) and canned foods/beverages
Health implications include endocrine system disruption, risk of CVD, neurological impairments, obesity, DM2, and liver enzyme abnormalities
No federal limits or bans on usesDietitian can reduce public exposure by
suggesting replacements