Bisphenol A , commonly abbreviated as BPA , is an organic compound with two phenol functional groups. It is a difunctional building block of several important plastics and plastic additives. With an annual production of 2–3 million tonnes, it is an important monomer in the production of polycarbonate.
Suspected of being hazardous to humans since the 1930s, concerns about the use of bisphenol A in consumer products were regularly reported in the news media in 2008 after several governments issued reports questioning its safety, and some retailers have removed products made of it from their shelves.
Synthesis
Bisphenol A was first reported by A.P. Dianin in 1891.
It is prepared by the condensation of acetone (hence the suffix A in the name) with two equivalents of phenol. The reaction is catalyzed by an acid, such as hydrochloric acid (HCl) or a sulfonated polystyrene resin. Typically, a large excess of phenol is used to ensure full condensation:
A large number of ketones undergo analogous condensation reactions. The method is efficient and the only by-product is water.
Use
Further information: PolycarbonateBisphenol A is used primarily to make plastics, and products containing bisphenol A-based plastics have been in commerce for more than 50 years. It is used in the synthesis of polyesters, polysulfones, and polyether ketones, as an antioxidant in some plasticizers, and as a polymerization inhibitor in PVC. It is a key monomer in production of epoxy resins and in the most common form of polycarbonate plastic. Polycarbonate plastic, which is clear and nearly shatter-proof, is used to make a variety of common products including baby and water bottles, sports equipment, medical and dental devices, dental fillings and sealants, eyeglass lenses, CDs and DVDs, and household electronics. Epoxy resins containing bisphenol A are used as coatings on the inside of almost all food and beverage cans. BPA is found in high concentration in thermal paper and carbonless copy paper. Bisphenol A is also a precursor to the flame retardant, tetrabromobisphenol A, and was formerly used as a fungicide.
Global production of bisphenol A in 2003 was estimated to be over 2 million tonnes. In the U.S., it is manufactured by Bayer MaterialScience, Dow Chemical Company, SABIC Innovative Plastics (formerly GE Plastics), Hexion Specialty Chemicals, and Sunoco Chemicals. In 2004, these companies produced just over 1 million t of bisphenol A, up from just 7,260 t in 1991. In 2003, annual U.S. consumption was 856,000 t, 72% of which was used to make polycarbonate plastic and 21% going into epoxy resins. The amount of BPA used in the US is equivalent to six pounds per habitant per year.
Identification in plastics
Main article: Resin identification codeThere are seven classes of plastics used in packaging applications. Type 7 is the catch-all "other" class, and some type 7 plastics, such as polycarbonate (sometimes identified with the letters "PC" near the recycling symbol) and epoxy resins, are made from bisphenol A monomer.
Type 3 (PVC) can also contain bisphenol A as an antioxidant in plasticizers.
Types 1 (PET), 2 (HDPE), 4 (LDPE), 5 (polypropylene), and 6 (polystyrene) do not use bisphenol A during polymerization or package forming.
Health effects
Bisphenol A is an endocrine disruptor, which can mimic the body's own hormones and may lead to negative health effects. Early development appears to be the period of greatest sensitivity to its effects. Regulatory bodies have determined safety levels for humans, but those safety levels are currently being questioned as a result of new scientific studies.
In 2009 the The Endocrine Society released a scientific statement expressing concern over current human exposure to BPA.
Previous studies
In 2007, a consensus statement by 38 experts on bisphenol A concluded that average levels in people are above those that cause harm to animals in laboratory experiments. A panel convened by the U.S. National Institutes of Health determined that there was "some concern" about BPA's effects on fetal and infant brain development and behavior. A 2008 report by the U.S. National Toxicology Program (NTP) later agreed with the panel, expressing "some concern for effects on the brain, behavior, and prostate gland in fetuses, infants, and children at current human exposures to bisphenol A," and "minimal concern for effects on the mammary gland and an earlier age for puberty for females in fetuses, infants, and children at current human exposures to bisphenol A." The NTP had "negligible concern that exposure of pregnant women to bisphenol A will result in fetal or neonatal mortality, birth defects, or reduced birth weight and growth in their offspring."
Obesity
A 2008 review has concluded that obesity may be increased as a function of BPA exposure, which "merits concern among scientists and public health officials". A 2009 review of available studies has concluded that "perinatal BPA exposure acts to exert persistent effects on body weight and adiposity". Another 2009 review has concluded that "Eliminating exposures to (BPA) and improving nutrition during development offer the potential for reducing obesity and associated diseases". Other reviews have come with similar conclusions. A later study on mice has shown that perinatal exposure to drinking water containing 1 mg/L of BPA increased adipogenesis in females at weaning.
Breast cancer
Further information: Risk factors of breast cancer#Bisphenol AA 2008 review has concluded that "perinatal exposure to (...) low doses of (..) BPA, alters breast development and increases breast cancer risk". Another 2008 review concluded that " animal experiments and epidemiological data strengthen the hypothesis that foetal exposure to xenoestrogens may be an underlying cause of the increased incidence of breast cancer observed over the last 50 years". A 2009 review, funded by the "Breast Cancer Fund", has recommended "a federal ban on the manufacture, distribution and sale of consumer products containing bisphenol A".
Neither the U.S. Environmental Protection Agency nor the International Agency for Research on Cancer have evaluated bisphenol A for possible carcinogenic activity.
Neurological issues
A panel convened by the U.S. National Institutes of Health determined that there was "some concern" about BPA's effects on fetal and infant brain development and behavior. A 2008 report by the U.S. National Toxicology Program (NTP) later agreed with the panel, expressing "some concern for effects on the brain".
A 2007 review has concluded that BPA, like other xenoestrogens, should be considered as a player within the nervous system that can regulate or alter its functions through multiple pathways. A 2007 review has concluded that low doses of BPA during development have persistent effects on brain structure, function and behavior in rats and mice. A 2008 review concluded that low-dose BPA maternal exposure causes long-term consequences at the level of neurobehavioral development in mice. A 2008 review has concluded that neonatal exposure to Bisphenol-A (BPA) can affect sexually dimorphic brain morphology and neuronal phenotypes in adulthood. A 2008 review has concluded that BPA altered long-term potentiation in the hippocampus and even nanomolar dosage could induce significant effects on memory processes. A 2009 review raised concerns about BPA effect on anteroventral periventricular nucleus.
A 2008 study by the Yale School of Medicine demonstrated that adverse neurological effects occur in non-human primates regularly exposed to bisphenol A at levels equal to the United States Environmental Protection Agency's (EPA) maximum safe dose of 50 µg/kg/day. This research found a connection between BPA and interference with brain cell connections vital to memory, learning and mood.
Disruption of the dopaminergic system
A 2005 review concluded that prenatal and neonatal exposure to BPA can potentiate the central dopaminergic systems, resulting in the supersensitivity of the drugs of abuse-induced rewarding effects and hyperlocomotion in the mouse.
A 2009 study on rats has concluded that prenatal and neonatal exposure to low-dose BPA causes deficits in development at dorsolateral striatum via altering the function of dopaminergic receptors.
Thyroid function
A 2007 review has concluded that bisphenol-A have been shown to bind to thyroid hormone receptor and perhaps have selective effects on its functions.
A 2009 review about environmental chemicals and thyroid function, raised concerns about BPA effects on triiodothyronine and concluded that "available evidence suggests that governing agencies need to regulate the use of thyroid-disrupting chemicals, particularly as such uses relate exposures of pregnant women, neonates and small children to the agents".
A 2009 review summarized BPA adverse effects on thyroid hormone action.
Research
Reproductive s
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