Understanding Bisphenol A’s Impact on Health and Environment
Bisphenol A is an organic compound that is processed synthetically and belongs to the diphenylmethane and bisphenol with two hydroxyphenyl groups attached to the carbon atom of the main chain. Its chemical formula is (CH3)2C(C6H4OH)2. Alternatively, bisphenol A (BPA) definition is that it is a synthetically obtained colourless crystalline organic compound that occurs in the solid phase belonging to the diphenylmethane group and is soluble in organic solvents but poorly dissolves in water (0.344 % wt. At 830C). The diagrammatic representation of the bisphenol A structure is given below.
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Bisphenol A structure represents a bisphenol 4,4’- methanediylphenol in which two methyl groups replace the methyl hydrogens attached with the carbon having a tetrahedral bond. BPAs are mostly used to manufacture certain plastic grades like polycarbonate plastics, some polysulfones and epoxy raisins, that are key material of plastic bottles, baby bottles and food and beverage containers. These are basically the byproducts that leach from the other products that are subjected to health and environmental degradation. BPA is a xenoestrogen and mimics estrogen present in the body, thus exhibiting hormone-like properties. Therefore, the EPA (environmental protection agency) in the USA has set a maximum permissible limit of BPA in the human body below 50 micrograms per kilogram of body weight per day.
Some of the Important Physicochemical Properties of Bisphenol A are Listed Below:
BPA Physico-Chemical Properties
The Chemical Properties of BPA are Listed below.
Bisphenol A Uses
BPA polycarbonate plastics are very sturdy in nature. Due to their high melting point, they have the ability to withstand high temperatures even inside microwaves. Thus they are used to make large variants of microwave-proof utensils.
Because of its high density, it has the capability to withstand high impact collisions. Thus they are very susceptible as a material for safety glasses, bulletproof windows and helmets.
Bisphenol A acts as a component in epoxy resins that are very good coating agents and therefore is used for the protective coating of pipelines and to cover the inner surface of food cans. This helps the food and beverages to last long without any decay. In 2003, the USA used 856000 tons of BPA to produce 21% of epoxy raisins that are mostly used in the printing industry for making sale receipts and other coating papers.
Due to their resiliency, they are used in many medical devices such as heart-lung machines, incubators, artificial kidney, dental fillers and sealants and due to their optical clarity it is also used as eyewear glasses.
BPA is used as the main agent for the production of major classes of resins. Alkylation of BPA with epichlorohydrin results in the formation of vinyl ester resins.
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It is a typical vinyl ester resin that is derived from bisphenol A diglycidyl ether. This is a bid cross-linking polymer produced by free radical polymerization.
Health and Environmental Effects
Some of the Biological Effects are Mentioned below:
Since bisphenol A acts as a xenoestrogen, it mimics the estrogen present in the body and thus shows the properties of certain hormones. Thus phenol containing molecules that are similar to that of BPA shows weak estrogenic properties and thus acts as an estrogenic chemical and endocrine disruptor. It also possesses the property that interrupts the nerve network that manages the signal for the development of the reproductive system in humans and animals.
BPA acts as a binder for both nuclear estrogen receptors, namely, ER alpha and ER beta. Though it is 1000 - 2000 times less fold potent than estradiol, it has the ability to mimic estrogen indicating that it is a selective estrogen receptor modulator t (SERM) and also antagonises estrogen. At high concentration, BPA also has the ability to act as an antagonist of the androgen receptor.
Few of the research shows that it causes stress and increases anxiety in rats. Thus, overexposure to it is harmful during pregnancy and the development of infants. Thus in 2012, the use of bisphenol was banned in baby products like feeding bottles, teethers etc. by the Food and Drug Administrator in the USA.
Some of the Environmental Effects of Bisphenol A are:
BPA can enter into the environment directly through the leaching of chemicals, or degradation of plastic bottles, industries that use BPA casting sands, paper and other recycling industries, plastic coating and straining manufacturers. These go straight into the land rendering it unfertile and barren making it unsuitable for agriculture.
BPA mostly affects the growth and reproduction of marine life. Fishes are the most sensitive species of freshwater. BPA causes endocrine effects in fish, amphibians and reptiles. The relevant exposure level of BPA in the environment is much higher than the level optimized for acute toxicity.
FAQs on Bisphenol A: Properties, Uses, and Health Effects
1. What is Bisphenol A (BPA) and what does its chemical structure look like?
Bisphenol A (BPA) is an organic synthetic compound with the chemical formula C₁₅H₁₆O₂. It is a key building block for several plastics and resins. Structurally, it consists of two phenol rings linked by a central carbon atom that is also bonded to two methyl groups. This structure is crucial as it mimics natural hormones in the body.
2. What are the key physical and chemical properties of Bisphenol A?
Bisphenol A exhibits several distinct properties relevant to its industrial applications:
Appearance: It is a white to light-brown solid, often in crystalline or flake form, with a mild phenolic odour.
Solubility: It has very low solubility in water but is soluble in organic solvents like ethanol, acetone, and ether.
Melting Point: It has a relatively high melting point, typically between 158°C to 159°C.
Reactivity: The two hydroxyl (-OH) functional groups on the phenol rings make it highly reactive, allowing it to undergo polymerisation to form long-chain polymers.
3. What are the most common industrial uses of Bisphenol A?
The primary industrial application of Bisphenol A is in the production of polymers. Its main uses include:
Polycarbonate Plastics: BPA is a primary monomer for producing polycarbonate, a strong, shatter-resistant, and clear plastic. This is used in food and beverage containers, water bottles, safety equipment, and electronic casings.
Epoxy Resins: It is used to create epoxy resins, which serve as protective linings on the inside of metal food and beverage cans to prevent corrosion and food contamination.
Other Applications: Minor uses include the production of flame retardants, dental sealants, and thermal paper for cash register receipts.
4. Why is Bisphenol A considered an endocrine disruptor?
Bisphenol A is considered an endocrine disruptor because its molecular structure closely mimics that of the natural hormone estrogen. Due to this structural similarity, BPA can bind to estrogen receptors within the human body. This interference can block or imitate the hormone's natural actions, leading to a disruption of the endocrine system which regulates metabolism, growth, development, and reproductive functions.
5. What are the main ways through which humans are exposed to Bisphenol A?
Human exposure to BPA occurs primarily through a process called leaching, where the chemical seeps out of products. The main routes of exposure are:
Dietary Intake: This is the most common route. BPA can leach from the polycarbonate plastics of food containers and the epoxy resin linings of canned foods into the food and beverages they hold, especially when heated.
Dermal Contact: Direct skin contact with materials containing BPA, such as thermal paper used for receipts, can lead to absorption.
Inhalation: Inhaling dust in air contaminated with BPA particles in household or industrial environments is another, less common, route of exposure.
6. What potential health effects are associated with exposure to BPA?
Research has linked BPA exposure to several potential health concerns, particularly due to its endocrine-disrupting properties. These potential effects include fertility problems, adverse effects on foetal brain development, behavioural issues in children, increased risk of certain hormone-related cancers, and a possible connection to conditions like obesity and heart disease. Regulatory bodies continue to study the levels at which these effects may become a concern.
7. How is Bisphenol A chemically synthesized for industrial use?
Industrially, Bisphenol A is produced through the condensation reaction of two parts (equivalents) of phenol with one part of acetone. This reaction is typically catalysed by a strong acid, such as hydrochloric acid (HCl), or a sulfonated polystyrene resin. Water is produced as a byproduct in this reaction.
8. Are products labelled 'BPA-free' always a safer alternative?
While 'BPA-free' products do not contain Bisphenol A, they often use chemically similar substitutes like Bisphenol S (BPS) or Bisphenol F (BPF). Some scientific studies suggest that these alternatives can also exhibit hormone-mimicking properties and may pose similar health risks. Therefore, while the label indicates the absence of BPA, it doesn't guarantee the product is free from other potentially disruptive bisphenols. Alternatives like glass, stainless steel, or polypropylene are often recommended to reduce exposure.
