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Introduction
Bisphenol S (BPS) has gained considerable attention as a replacement for Bisphenol A (BPA) following widespread concerns about the endocrine-disrupting effects of BPA.
Structurally similar to BPA, BPS contains two phenol groups bonded by a sulfone group rather than a carbon bridge.
This substitution imparts thermal and photochemical stability, making BPS favorable in many industrial applications, especially in materials subjected to high heat.
However, recent toxicological studies raise questions about the safety profile of BPS.
The global transition from BPA to BPS occurred largely without rigorous toxicological evaluations. While some regulators considered BPS a "safer" alternative, emerging data suggests that BPS may exert comparable endocrine-disrupting effects, posing potential risks to human health and the environment.
As such, the increased use of BPS in consumer products—particularly in thermal paper receipts, food packaging, and epoxy resins—has resulted in widespread environmental dissemination and human exposure.
This article aims to provide an exhaustive review of the chemical characteristics, synthesis methods, commercial applications, environmental behavior, toxicological properties, regulatory developments, and public health implications of BPS.
It seeks to bridge knowledge gaps and stimulate further research to better inform policymakers, industries, and the scientific community.
Chemical Identity and Properties
Bisphenol S (BPS), also known by its IUPAC name 4,4'-sulfonylbisphenol, is a synthetic organic compound and a member of the bisphenol family.
It is derived from phenol and sulfur-containing reagents and features a symmetrical structure with two hydroxyphenyl moieties connected through a sulfone (–SO₂–) bridge.
Chemical and Physical Information
Property Value / Description
Chemical Name Bisphenol S
CAS Number 80-09-1
IUPAC Name 4,4'-Sulfonylbisphenol
Molecular Formula C₁₂H₁₀O₄S
Molecular Weight 250.27 g/mol
Synonyms BPS, 4,4′-Sulfonyldiphenol, Sulfonylbisphenol, Sulfonyldiphenol
Melting Point 240–250 °C
Boiling Point Decomposes before boiling
Solubility in Water Moderate (~77 mg/L at 25°C)
Log Kow (octanol/water) ~1.65 (moderate lipophilicity)
Appearance White to off-white crystalline powder
Stability Thermally stable; resistant to photodegradation
Due to its rigid aromatic and sulfone-containing backbone, BPS exhibits enhanced chemical stability, mechanical strength, and resistance to hydrolysis and thermal degradation compared to BPA.
This makes BPS particularly useful in applications where chemical resistance and high-temperature performance are critical.
Despite these advantageous material properties, the presence of phenolic groups renders BPS biologically active, especially in hormone-mimicking pathways.
These dual characteristics—a desirable industrial profile and potential biological reactivity—highlight the importance of understanding both the chemical and toxicological nature of BPS.
Synthesis and Manufacturing
Bisphenol S (BPS) is synthesized primarily via the sulfonation of phenol using sulfuric acid or sulfur trioxide as the sulfonating agent.
The industrial process generally involves the condensation of two equivalents of phenol with one equivalent of sulfuric acid or a sulfur trioxide complex under acidic conditions.
General Reaction:
2 C₆H₅OH (phenol) + H₂SO₄ → (HO–C₆H₄)₂SO₂ + 2 H₂O
The reaction occurs via electrophilic aromatic substitution, where sulfuric acid first protonates phenol, increasing its reactivity.
Then the electrophilic sulfur species reacts with two phenol molecules to form BPS.
The resulting BPS is precipitated, purified via recrystallization, and dried to obtain the commercial product.
Variations:
Some synthetic protocols use oleum (fuming sulfuric acid) or chlorosulfonic acid to increase the yield.
Green chemistry methods have employed ionic liquids, heterogeneous catalysts, or solvent-free conditions to minimize environmental impact.
By-products:
Ortho-substituted isomers of bisphenol S
Oligomeric sulfonates
Unreacted phenol and sulfonation residues
The production of BPS is relatively cost-effective due to inexpensive raw materials and simple reaction conditions.
This ease of synthesis contributes to its rapid adoption in various industrial applications.
Industrial and Commercial Applications
BPS is used in a wide range of applications due to its chemical and thermal stability.
Its role as a substitute for BPA has expanded significantly, particularly in products where heat or UV resistance is required.
Key Applications:
Thermal Paper:
BPS is commonly used as a color developer in thermal receipt paper.
It is favored over BPA due to regulatory restrictions and public health concerns.
BPS levels in thermal paper can reach 0.1–3% by weight.
Epoxy Resins and Polycarbonate Plastics:
Used in the synthesis of epoxy-based coatings and high-performance plastics.
These materials are utilized in can linings, bottle caps, and electronics.
Textiles and Flame Retardants:
Applied as a component in textile coatings and leather treatments.
Enhances flame resistance and chemical durability.
Adhesives and Sealants:
Included in industrial adhesives, especially in sectors requiring thermal and chemical resistance such as automotive and construction.
Electronics:
Found in printed circuit boards, insulation materials, and encapsulants.
SAFETY INFORMATION ABOUT BISPHENOL S
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off conSAFETYtaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
