Bisphenol A: Difference between revisions
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As an environmental contaminant this compound interferes with [[nitrogen fixation]] at the roots of [[leguminous]] plants associated with the [[bacterial]] [[symbiont]] ''[[Sinorhizobium meliloti]]''. Despite a [[half-life]] in the soil of only 1–10 days, its ubiquity makes it an important [[pollutant]].<ref name=fox>{{cite journal | author=Fox, J.E., J. Gulledge, E. Engelhaupt, M.E. Burrow & J.A. McLachlan | title=Pesticides reduce symbiotic efficiency of nitrogen-fixing rhizobia and host plants | journal=[[PNAS|Proc. Nat. Acad. Sci.]] | year=2007 | volume=104 | pages=10282–7}}</ref> |
As an environmental contaminant this compound interferes with [[nitrogen fixation]] at the roots of [[leguminous]] plants associated with the [[bacterial]] [[symbiont]] ''[[Sinorhizobium meliloti]]''. Despite a [[half-life]] in the soil of only 1–10 days, its ubiquity makes it an important [[pollutant]].<ref name=fox>{{cite journal | author=Fox, J.E., J. Gulledge, E. Engelhaupt, M.E. Burrow & J.A. McLachlan | title=Pesticides reduce symbiotic efficiency of nitrogen-fixing rhizobia and host plants | journal=[[PNAS|Proc. Nat. Acad. Sci.]] | year=2007 | volume=104 | pages=10282–7}}</ref> |
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==Identification in Plastics== |
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Seven groups of plastic polymers,<ref name=singapore>{{cite web | title=Safe Use Of Plastic Food Packaging And Containers | url=http://www.ava.gov.sg/FoodSector/FoodSafetyEducation/Food+Facts/SafeUsePlasticContainers/index.htm }}</ref> each with specific properties, are used worldwide for packaging applications (see table below). Each group of plastic polymer can be identified by its Plastic Identification code (PIC) - usually a number or a letter abbreviation. For instance, Low-Density Polyethylene can be identified by the number "4" and/or the letters "LDPE". The PIC appears inside a three-chasing arrow recycling symbol. The symbol is used to indicate whether the plastic can be recycled into new products. |
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The PIC was introduced by the Society of Plastics Industry, Inc. which provides a uniform system for the identification of different polymer types and helps recycling companies to separate different plastics for reprocessing. Manufacturers of plastic food packaging and containers can voluntarily mark their products with the PIC. Consumers can identify the plastic types based on the codes usually found at the base or at the side of the plastic food packaging and containers. The PIC is usually not present on packaging films, as it is not practical to collect and recycle most of this type of waste. |
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{| class="wikitable" |
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|- |
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! Plastic Identification Code |
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! Type of plastic polymer |
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! Properties |
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! Common Packaging Applications |
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|- |
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| 1 |
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| Polyethylene Terephthalate (PET, PETE) |
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| Clarity, strength, toughness, barrier to gas and moisture. |
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| Soft drink, water and salad dressing bottles; peanut butter and jam jars |
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|- |
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| style="background:#99FF99" | 2 |
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| style="background:#99FF99" | High Density Polyethylene (HDPE) |
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| style="background:#99FF99" | Stiffness, strength, toughness, resistance to moisture, permeability to gas. |
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| style="background:#99FF99" | Milk, juice and water bottles; yogurt and margarine tubs; trash and retail bags. |
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|- |
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| 3 |
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| Polyvinyl Chloride (V) |
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| Versatility, clarity, ease of blending, strength, toughness. |
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| Juice bottles; cling films |
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|- |
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| style="background:#99FF99" | 4 |
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| style="background:#99FF99" | Low Density Polyethylene (LDPE) |
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| style="background:#99FF99" | Ease of processing, strength, toughness, flexibility, ease of sealing, barrier to moisture. |
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| style="background:#99FF99" | Frozen food bags; squeezable bottles, e.g. honey, mustard; cling films; flexible container lids. |
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|- |
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| style="background:#99FF99" | 5 |
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| style="background:#99FF99" | Polypropylene (PP) |
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| style="background:#99FF99" | Strength, toughness, resistance to heat, chemicals, grease and oil, versatile, barrier to moisture. |
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| style="background:#99FF99" | Reusable microwaveable ware; kitchenware; yogurt containers; margarine tubs; microwaveable disposable take-away containers; disposable cups and plates. |
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|- |
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| 6 |
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| Polystyrene (PS) |
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| Versatility, clarity, easily formed |
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| Egg cartons; disposable cups, plates, trays and cutlery; disposable take-away containers; yogurt and margarine containers |
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|- |
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| 7 |
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| Other |
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| Dependent on polymers or combination or polymers. |
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| Beverage bottles; baby milk bottles. |
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|- |
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|} |
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==References== |
==References== |
Revision as of 18:12, 8 March 2008
Bisphenol A (abbreviated BPA) is an organic compound with the formula (CH3)2C(C6H4OH)2. Containing two phenol functional groups, it is a difunctional building block to several important polymers and polymer additives.[1] Bisphenol A has become controversial because it mimics estrogen and thus could induce hormonal responses.[2][3]
Synthesis
Bisphenol A is prepared by the reaction of two equivalents of phenol with one equivalent of acetone. Hydrochloric acid (HCl) and or sulfonated polystyrene is used as a catalyst. Typically, a large excess of phenol is used to ensure full condensation:
- (CH3)2CO + 2 C6H5OH → (CH3)2C(C6H4OH)2 + H2O
A large number of ketones undergo analogous condensation reactions. The methodology is an example of a "green chemical reaction" in the sense that the process is efficient and the only by-product is water.[1]
History and use
Bisphenol A was first reported by A.P. Dianin in 1891.[4][5] Bisphenol A current uses are numerous. It is a key monomer in production of polycarbonate plastic and epoxy resins. Otherwise it is used in the following polymer types: polyesters, polysulfones, and polyether ketones. Bisphenol A is also used as an antioxidant in plasticizers and as a polymerization inhibitor in PVC.[1]
It is a precursor to the flame retardant tetrabromobisphenol A.
Endocrine disruptor controversy
There is growing concern that exposure to bisphenol A may induce adverse effects in humans.[6]
Bisphenol A was investigated in the 1930s during the search for estrogen mimics. From this study the synthetic compound diethylstilbestrol was shown to be a better competitor with estrogen.[citation needed] Bisphenol A, like many other compounds, is known to be an estrogen receptor agonist.[7] Such agonists can activate estrogen receptors, leading to similar physiological effects as the body's own estrogens.[8] The first evidence of the estrogenicity of bisphenol A came from experiments in the 1930s in which it was fed to ovariectomized rats.[9][10] Some hormone disrupting effects in studies on animals and human cancer cells have been shown to occur at levels as low as 2–5 ppb (parts per billion). It has been claimed that these effects lead to health problems such as, in men, lowered sperm count and infertile sperm. Recent studies have confirmed that bisphenol A exposure during development has carcinogenic effects and produce precursors of breast cancer.[11][12] Bisphenol A has been shown to have developmental toxicity, carcinogenic effects, and possible neurotoxicity.[13][14] Recent studies suggest it may also be linked to obesity by triggering fat-cell activity.[15] Schizophrenia research indicates endocrine disruptors like BPA may be involved in schizophrenia pathogenesis.[16]
A consensus statement by 38 BPA experts concluded that average levels in people are above those that cause harm to animals in laboratory experiments,[17] and a NIH-sponsored panel in the U.S. determined that there was 'some concern' about BPA's effect on fetal and infant brain and behavior.[18] Peer reviewed publications have appeared pointing out flaws within the chemical industry funded studies that report bisphenol A safety.[19] In 2006, Canadian regulators selected bisphenol A as one of 200 substances deserving of thorough safety assessments after preliminary studies found it to be 'inherently toxic'; the chemical had not previously been studied by them in depth, having been accepted under grandfather clauses when stricter regulations were passed in the 1980s. The research will begin in May 2007, and take some time to complete.[20]
Dr. Maida Galvez, a pediatrician studying BPA, recommends parents stay away from bottles containing the chemical and says, "We know the animal studies raise concerns, but there aren't human studies showing effects yet ... so, when we don't have the evidence, what we recommend is that parents try to err on the side of caution."[21]
Bisphenol A has been known to leach from the plastic lining of canned foods and, to a lesser degree, polycarbonate plastics that are cleaned with harsh detergents or used to contain acidic or high-temperature liquids.[22] The chemical is found in almost everyone that lives in developed countries at low concentrations. Infants fed with liquid infant formula have among the highest exposures of anyone eating canned foods. Infants fed canned formula with polycarbonate bottles can consume quantities of bisphenol A up to 13 µg/kg/day,[23] while the most sensitive animal studies show effects at much lower concentrations. Debate continues on what is the safe limit of this compound. Within the United States, an exposure of up to 50 µg/kg/day (50 ppb/day) is considered safe[20] by the United States Environmental Protection Agency[24] - well above the levels found to have caused negative health effects in studies (see table below).
The city of San Francisco, California, banned the sale of baby bottles and other products for young children containing bisphenol A effective December 2006, and was, at the time, the only jurisdiction in the world to outright forbid the substance.[25] The ban was never enforced, and in May 2007 the city repealed the ban. In January 2006, the German Federal Institute for Risk Assessment announced that polycarbonate baby bottles are safe, stating that published research is "difficult to interpret and [is] occasionally contradictory".[26] A subsequent study by the European Union’s Food Safety Authority reached a similar conclusion, and sharply criticized the methodology used in many of the low-dose exposure studies on rodents.[27] Japan has also concluded that normal use of these products is safe.[28] Currently 9 U.S. states have legislation pending that would affect the use of BPA in containers.[21]
Growing awareness of health concerns in the U.S. retail sector, particularly in chains promoting healthy food and lifestyles, has led to a number of classes of products containing Bisphenol A to be withdrawn. In 2005, Patagonia Inc., a retailer of outdoor gear, ceased selling polycarbonate bottles. In 2006, Whole Foods Markets ceased selling baby bottles. In 2007, Mountain Equipment Co-op ceased selling bottles containing BPA.[29]
Dose (µg/kg/day) | Effects (measured in studies of laboratory animals) | Study Year[30] |
---|---|---|
0.025 | Permanent changes to genital tract | 2005 |
0.025 | Changes in breast tissue that predispose cells to hormones and carcinogens | 2005 |
2 | 30% increase in prostate mass | 1997 |
2.4 | Signs of early puberty | 2002 |
2.4 | Decline in testicular testosterone | 2004 |
2.5 | Breast cells predisposed to cancer | 2006 |
10 | Prostate cells more sensitive to hormones and cancer | 2006 |
10 | Insulin resistance | 2006 |
10 | Decreased maternal behavior | 2002 |
20 | Damage to eggs and chromosomes | 2003 |
25 | Health Canada provisional human exposure limit | 1999 |
30 | Hyperactivity | 2004 |
30 | Reversal of normal sex difference in brain structure | 2001 |
50 | U.S. human exposure limit | 1998 |
Environmental risk
Bisphenol has a low toxicity and negligible skin permeability. Bisphenols have been widely used as antioxidants in cosmetics and foods.Cite error: A <ref>
tag is missing the closing </ref>
(see the help page).
References
- ^ a b c Helmut Fiege, Heinz-Werner Voges, Toshikazu Hamamoto, Sumio Umemura, Tadao Iwata, Hisaya Miki, Yasuhiro Fujita, Hans-Josef Buysch, Dorothea Garbe, Wilfried Paulus "Phenol Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH: Weinheim, 2002. DOI: 10.1002/14356007.a19_313.
- ^ Hot liquids release potentially harmful chemicals in polycarbonate plastic bottles
- ^ Le HH, Carlson EM, Chua JP, Belcher SM (2008). "Bisphenol A is released from polycarbonate drinking bottles and mimics the neurotoxic actions of estrogen in developing cerebellar neurons". Toxicol. Lett. 176 (2): 149–56. doi:10.1016/j.toxlet.2007.11.001. PMID 18155859.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Dianin, Zhurnal russkogo fiziko-khimicheskogo obshchestva, 23 (1891), pp. 492 ff.
- ^ Theodor Zincke (1905). "Ueber die Einwirkung von Brom und von Chlor auf Phenole: Substitutionsproducte, Pseudobromide und Pseudochloride". Justus Liebigs Annalen der Chemie (343): 75–99. doi:10.1002/jlac.19053430106.
- ^ vom Saal FS, Hughes C (2005). "An extensive new literature concerning low-dose effects of bisphenol A shows the need for a new risk assessment". Environ. Health Perspect. 113 (8): 926–33. PMID 16079060.
- ^ Okada, H; et al. (2008), "Direct evidence revealing structural elements essential for the high binding ability of bisphenol A to human estrogen-related receptor-gamma.", Environ. Health Perspect., 116 (1): 32–38, PMID: 18197296
{{citation}}
: Explicit use of et al. in:|last2=
(help)CS1 maint: date and year (link) - ^ O’Connor, Chapin (2003). "Critical evaluation of observed adverse effects of endocrine active substances on reproduction and development, the immune system, and the nervous system" (Full Article). Pure Appl. Chem. 75 (11–12): 2099–2123. Retrieved 2007-02-28.
- ^ E. C. Dodds and Wilfrid Lawson, "Synthetic Œstrogenic Agents without the Phenanthrene Nucleus", Nature, 137 (1936), 996.
- ^ E. C. Dodds and W. Lawson, Proceedings of the Royal Society of London, Series B, Biological Sciences, 125, #839 (27-IV-1938), pp. 222–232.
- ^ Murray TJ (2007). "Induction of mammary gland ductal hyperplasias and carcinoma in situ following fetal bisphenol A exposure" (Abstract). Reproductive Toxicology. Retrieved 2007-02-28.
- ^ Soto AM, Vandenberg LN, Maffini MV, Sonnenschein C (2008). "Does breast cancer start in the womb?". Basic Clin. Pharmacol. Toxicol. 102 (2): 125–33. doi:10.1111/j.1742-7843.2007.00165.x. PMID 18226065.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Lee Ym; et al. (2007). "Estrogen receptor independent neurotoxic mechanism of bisphenol A, an environmental estrogen" (Abstract). J Vet Sci. 8 (1): 27–38. Retrieved 2007-02-28.
{{cite journal}}
: Explicit use of et al. in:|last=
(help) - ^ Zsarnovszky A, Le HH, Wang HS, Belcher SM. (2005). "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 A" (Abstract). Endocrinology. 146 (12): 5388–96. Retrieved 2007-02-28.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Grossman, Elizabeth. (March 12, 2007). "Chemicals May Play Role in Rise in Obesity". Washington Post.
- ^ Brown JS (2008). "Effects of Bisphenol-A and Other Endocrine Disruptors Compared With Abnormalities of Schizophrenia: An Endocrine-Disruption Theory of Schizophrenia". Schizophrenia Bulletin. doi:10.1093/schbul/sbm147. PMID 18245062.
- ^ vom Saal, Fred. (July 27, 2007). "Chapel Hill bisphenol A expert panel consensus statement: integration of mechanisms, effects in animals and potential to impact human health at current levels of exposure". Reprod Toxicol.
- ^ "CERHR Expert Panel Report for Bisphenol A" (PDF). Retrieved 2007-12-07.
- ^ Frederick S. vom Saal (2006). "Large effects from small exposures. II. The importance of positive controls in low-dose research on bisphenol A." (Abstract). Environmental Research. 100 (1): 50–76. Retrieved 2007-02-28.
- ^ a b Mittelstaedt, Martin (2007-04-07). "'Inherently toxic' chemical faces its future". Globe & Mail. Retrieved 2007-04-07.
{{cite news}}
: Check date values in:|date=
(help) - ^ a b Parents Concerned Over Potentially Toxic Baby Bottles ABC News, Feb. 7, 2008.
- ^ "Environmental Working Group". Retrieved 2007-03-07.
- ^ "European Food Safety Authority Opinion" (Abstract). Retrieved 2007-02-28.
- ^ Bisphenol A - United States Environmental Protection Agency
- ^ "Anxieties about toxics". San Francisco Chronicle. 2006-11-22.
{{cite news}}
: Check date values in:|date=
(help) - ^ Selected questions and answers relating to bisphenol A in baby bottles- Federal Institute for Risk Assessment
- ^ European Safety Review: No Risk from Bisphenol A Exposure
- ^ Why has bisphenol A not been banned? - Federal Institute for Risk Assessment
- ^ "Polycarbonate bottles raise questions". Associated Press. 2007-12-23.
{{cite news}}
: Check date values in:|date=
(help) - ^ Adapated from EWG, 2007. "Many studies confirm BPA's low-dose toxicity across a diverse range of toxic effects," Environmental Working Group Report: A Survey of Bisphenol A in U.S. Canned Foods. Accessed November 4th, 2007 at http://www.ewg.org/node/20941.
External links
- Plastics chemical alters female brains
- Frontline Fooling With Nature, interview Fredrick Vom Saal, Ph.D.
- News report on effect through plastic bottles
- Bisphenol A. A Known Endocrine Disruptor WWF publication
- Plastics Industry Bisphenol A information site
- United States Environmental Protection Agency page on Bisphenol A
- An Endocrine/Estrogen Letter special Report on BPA
- News coverage of bisphenol A from EnvironmentalHealthNews.org
- EWG testing of Bisphenol A in canned food and formula
- The Toxic Origins of Disease, Liza Gross, PLoS Biology - an essay examining some of the evidence and effects.
- CHEMICAL FALLOUT: JOURNAL SENTINEL WATCHDOG REPORT, Milwaukee Journal Star newspaper article examining effects of Bisphenol A on lab animals and humans.
- Safe Use Of Plastic Food Packaging And Containers, Agri-Food & Veterinary, Authority of Singapore
- Which plastic water bottles don't leach chemicals?, Vreni Gurd, 03/29/2007