Bisphenol A (BPA)

Bisphenol A (C₁₅H₁₆O₂) with an IUPAC name [4,4′-(propane-2,2-diyl)diphenol], is a colorless crystalline solid from organic compounds. It is almost insoluble in water (0.3% w/w) and soluble in common organic solvents i.e. n-hexane, toluene, etc. BPA has been used, since the 1950s, with other chemicals to manufacture plastics (primarily polycarbonate plastics), epoxy resins, thermal papers, and as a polymerization inhibitor for polyvinyl chloride plastics.

Bisphenol A is produced industrially and its production exceeds 10-12 million tonnes/year as of 2022. BPA-added products are particularly useful in the lining of foods & beverages; cans & bottles, eyewear, dental sealant composites, water supply linings, plastics, and resins.

Along with many uses, bisphenol-A is considered to have certain health hazards. Most people are generally exposed to Bisphenol A through diet. It seeps/leaches into food from protective internal epoxy coatings of food cans and plastic tableware. The degree of this leaching/absorbance of BPA into food depends on the temperature and period of exposure.

Discovery & Structure of Bisphenol A

Aleksandr Pavlovich Dianin (a Russian chemist from Saint Petersburg) in 1891, carried out studies on phenol and discovered a derivative, which was named Dianin compound, and later on, came to be known as Bisphenol A.

Bisphenol A belongs to the group of diphenylmethane. By IUPAC rules, it is usually named 4,4′-(propane-2,2-diyl)diphenol, and sometimes, 4-[2-(4-hydroxyphenyl)propan-2-yl]phenol. It can be identified as {CAS no: 80-05-7}.

The torsional angle between the two phenol groups is 91.5°, therefore the correct way to pictorially represent BPA is;

However, its structure may also sometimes be drawn as;

Synthesis of Bisphenol A

Bisphenol A is a condensation product of acetone and phenol. This is a 130-year-old method still used today (with fundamental changes) called Dianin’s method.

For the synthesis of BPA, acetone is condensed with phenol, in the presence of a strong acid, i.e. HCl, H₂SO₄. Sulfonic acid or polystyrene sulfonate (solid acid resins) can also serve the purpose.

Bisphenol A is a cheap compound because the reactant components of Dianin’s reaction are available through the cumene process, which creates phenol and acetone by using benzene and propylene.

Properties of Bisphenol A

Bisphenol A has a fairly high melting point (155 °C). It dissolves in organic solvents and is also slightly soluble in water. It may be recrystallized from acetic acid with water.

BPA is a structural component of polycarbonate plastic bottles. It is also a structural component of metal can coating epoxies, which protect the food from directly contacting metallic surfaces. As the food is directly in contact with BPA, it is most likely to migrate in food and be consumed (in some amounts). As the structure of BPA is similar to that of estrogen, a debate about the hazardousness or usefulness of bisphenol A arises here.

Spectroscopic data:

IR spectrum

NMR spectrum

Effects/Hazards of Bisphenol A

The main reason for being concerned about the effects of bisphenol A on human health is its widespread use. The U.S. National Institute of Environmental Health Sciences (NIEHS), conducted a study, back in 2003-04 which reported detectable levels of BPA in almost 93% of people, aged six years and older.

The U.S. Food and Drug Administration (FDA) is continuously observing available informational studies and will update its assessment of BPA, however, the current scientific evidence continues to support the safety of bisphenol A for use in food containers and packaging.

Biological effects of Bisphenol A

Some animal studies have suggested that infants and children may be most vulnerable to bisphenol A. The concern over BPA consumption is the estrogen-like activity At high concentrations, bisphenol A starts mimicking the effects of estradiol, a female sex hormone. Although the effects are 100 to 2000 folds less potent, they have been noted to produce effects with the increasing concentration (TDI/kg/day) of BPA.

The effects according to FDA (2008) increase as;

The U.S. Centers for Disease Control and Prevention (CDC)  has stated that BPA has been noted to affect the reproductive system of laboratory animals. The most common animals for such symptoms and studies are mice and rats.

Environmental effects of Bisphenol A

According to EFSA, BPA might be present in meat and related products through contact with packaging and processing equipment or through other forms of contamination i.e. environment, feed, etc.

BPA is a contaminant of emerging concern. The continuous release of BPA in the environment affects both plants and animals, despite its short half-life and non-bioaccumulating character. Recent studies have suggested a significant impact of this pollutant on fishes, amphibians, and other life forms on the planet, however, no existing data proves these studies.

Safe levels of Bisphenol A (TDI)

According to European Food Safety Authority (EFSA), the Tolerable Daily Intake (TDI) of bisphenol A is 4μg per kilogram of body weight [4μg/day-bw/kg]. The EFSA considers that BPA poses no risk to consumers of any age group including unborn children and infants. In a report published in 2015, the highest dosage from exposure to different sources was found to be 3 to 5 times lower than the TDI.

However, the U.S. Environment Protection Agency (EPA) agrees that BPA is a reproductive and developmental toxicant at doses in animal studies of more than 0.05mg or 50μg per kilogram of body weight [50μg/day-bw/kg].

How to prevent exposure to BPA?

1. Do not microwave food in polycarbonate plastic bottles and kitchenware. Polycarbonate is a strong polymer, but it may start breaking down at high temperatures over time. Porcelain, glass, or steelware may be used instead for food heating purposes.
2. Babies may be given BPA-free baby bottles.
3. The plastics made with BPA are marked with the number 3 or 7 in between the recycle symbol (♲). Their use may be avoided to stay away from BPA, but keep in mind that BPA plastics may be unmarked too.
4. Canned and packaged foods are the primary source of BPA exposure. Fresh whole foods may be used instead to reduce exposure.
5. Go for BPA-free products everywhere because almost everything we use has a direct or indirect connection to the plastic industry.

Alternatives of Bisphenol A [Bisphenol AF, S, Z & F]

The best way to deal with a potentially damaging chemical is to find its alternatives. Some steps have been taken in this direction for bisphenol A as well but some recent studies have also highlighted the hazards of these alternatives as well.

The alternatives of bisphenol A are bisphenol AF, bisphenol F, bisphenol S, bisphenol Z, and tetramethyl bisphenol F. The most famous among these substitutes are bisphenol S and F.

Concepts Berg

Why are people concerned about BPA?

people tend to be more and more concerned about BPA because of its growing and widespread use, its contact with our daily life routine items especially food, and because of its potential systematic changes in the body that may induce reproductive changes and even cancer.

How does BPA get into the body?

BPA gets into our bodies most probably through food. Our foods being more and more canned and processed make it all easier.

If I am concerned, what can I do to prevent exposure to BPA?

If in case a person is concerned about being exposed to BPA, he/she should use alternative plastics, avoid canned and processed foods, avoid heating food in polycarbonate plastics, esp[ecially in a microwave oven, and use BPA-free products in every aspect of life.

What are the levels of BPA in the U.S. Population?

Bisphenol A is present in almost every individual living today. The level to which a person has been exposed matters most. According to a study conducted by U.S. CDC [National Report on Human Exposure to Environmental Chemicals (NHANES)] (2011-2016), among the U.S. population, males were more effected than females in terms of BPA (μg/L) of the urine samples. Males of ages (11-12 years) had ~1.64μg/L and females (11-12 years) had ~1.39μg/L of BPA in their urine samples.

Similarly, Non-Hispanic Black people were more effected (2.12μg/L) than any other races; Non-Hispanic Whites (1.46μg/L), All Hispanics (1.48μg/L), Mexican Americans (1.45μg/L), and Asians (1.03μg/L).

How does BPA effects people’s health?

The long-term effects of BPA on human health have been reported to be systematically reduced body weight leading to liver effects in initial and then proceeding to Irreversible and reversible reproductive effects. However, some cardiovascular diseases and Type 2 diabetes have sometimes been associated with BPA as well.

What does the government do to deal with BPA?

The governmental authorities are regularly keeping a check on the potential effects of BPA on human health and environment and the authorities are regularly updating their scheme and instructions for the public to amend their lifestyle to be BPA-free.

What can parents do to avoid BPA risks?

Parents should avoid BPA products and only provide BPA-free plastics e.g. bottles for their children.

What are the potential health effects of BPA exposure?

The potential health effects of BPA exposure are cardiovascular diseases, blood pressure, diabetes, and reproductive changes.

Which products may contain BPA?

Almost all cans containing food are lined with BPA to avoid contact with metals and food. Besides that, all bottles (especially polycarbonate ones) contain bisphenol A. Epoxy resins are a major source of BPA as well.

Are BPA alternatives safe?

Although bisphenol A is being avoided for some years by using alternatives but, these products e.g. bisphenol S and F have also been reported to cause some problems with human health. However, bisphenol S contains sulfur which makes it biodegradable and safe for the environment.

Is Bisphenol A toxic?

Bisphenol A is thought to be toxic however there is no significant scientific evidence to support this thought.

When and why was bisphenol A banned?

BPA has never been banned as a whole. FDA banned its use for baby bottles in 2012. However, in 2017, the European Chemicals Agency (ECHA) listed BPA as a product of high concern due to its activities related to the endocrine system.

What is bisphenol A used for?

Bisphenol A is used as a reactant in polycarbonate plastics leading to its use in baby bottles, water bottles, food containers, pitchers, storage containers, and epoxy resins.

Is BPA still used today?

According to recent reports, over six billion pounds of BPA are synthesized each year and are being consumed by an enormous industrial giant i.e. plastics and epoxy resins.

Can BPA enter a body through skin?

BPA can seep into or get absorbed by the skin of humans when handling plastics, thermal papers, and much more.

Does BPA build up in the body?

BPA does not get synthesized in our bodies. It enters one way or another and then wanders our fat tissues.

What does ‘a’ stand for in bisphenol-a?

The ‘A’ in bisphenol A stands for acetyl or acetone. This is because, in Dianin’s production method, acetone is a major reactant along with two phenol groups.

What is the difference between Bisphenol A and Bisphenol F?

The structural difference between bisphenol A and F is that in BPA an acetone group acts in between two phenols to make a carbon connected to two phenols and further connected to two methyl groups. In BPF however, the central carbon is further linked to two hydrogen atoms. This makes it a structurally similar compound for use in plastics with less carbon content.

References

• Data table (U.S.CDC, NHANES)
• Action Plan [U.S. Environment Protection Agency (EPA)]
• Tips to help reduce your exposure (Toxic Free Future)
• Nutrition and Healthy Eating (MayoClinic)
• Chemical compound (Brittanica.com)