Bisphenol S (BPS): Is the “BPA-Free” Alternative Actually Safe?

Introduction

For years, consumers have been told to look for "BPA-free" labels on plastic products, receipts, and food packaging. Bisphenol A (BPA) - a well-known endocrine-disrupting chemical - has been phased out of many consumer goods due to growing evidence of its harmful health effects. But here's the uncomfortable truth: "BPA-free" does not mean "risk-free."

Bisphenol S Uses

In response to consumer demand and regulatory pressure, manufacturers have replaced BPA with structurally similar alternatives - chief among them, Bisphenol S (BPS). Today, BPS is widely used in thermal paper (receipts, tickets, labels), polycarbonate plastics, epoxy resins, food packaging, coatings, textiles, and even personal care products. It is also a key monomer in the production of high-performance polymers like polysulfone (PSU) and polyethersulfone (PES).

But is BPS truly safer than BPA? A growing body of scientific evidence suggests otherwise. This article explores what the research actually says about BPS safety, how it compares to BPA, and why regulators are now taking action.

What Is Bisphenol S (BPS) Powder?

Bisphenol S (CAS 80-09-1) is a chemical compound used primarily as a substitute for BPA in the production of polycarbonate plastics and epoxy resins. It appears as a slightly beige crystalline powder and offers similar thermal and chemical stability to BPA, making it attractive for industrial applications.

Common uses of BPS include:

Thermal paper coatings (receipts, tickets, labels)
Monomer for polysulfone and polyethersulfone polymers
Epoxy resins and coatings
Textile dye-fixing agents and leather modifiers
Metal electroplating additives

The problem? BPS entered the market largely unregulated and understudied - a classic case of "regrettable substitution," where one questionable chemical is replaced by another with similar risks.

BPS vs. BPA: A Chemical Cousin with Similar Risks

Because BPS and BPA share a similar chemical structure, researchers have long suspected they might also share similar toxicological properties. Recent studies confirm these suspicions.

1. Endocrine Disruption

BPS is classified as an endocrine-disrupting chemical (EDC) - meaning it can interfere with the body's hormonal system. In silico molecular docking studies have shown that BPS exhibits binding affinities and interaction patterns comparable to BPA across multiple hormone receptors, including estrogen receptors (ERα and ERβ), androgen receptors, and thyroid receptors. Notably, BPS was found to form an additional hydrogen bond with estrogen receptor α, potentially stabilizing the protein-ligand complex even more effectively than BPA.

Research has demonstrated that BPS, like BPA, can activate both estrogen receptors. This means BPS has the potential to disrupt normal hormonal signaling in the human body - the very reason BPA was restricted in the first place.

2. Reproductive Toxicity

The reproductive toxicity of BPS is particularly concerning. A 2024 study on pregnant rats found that perinatal BPS exposure disrupted the hypothalamic-pituitary-ovarian (HPO) axis, altered hormone levels, and affected offspring development and fertility. The effects included abnormal body weight changes, estrous cycle disruption, and embryonic dysplasia in the F1 generation.

Another study using human ovarian epithelial cells revealed that BPS exposure at human-relevant levels triggered cell cycle arrest through the ERβ-MAPK signaling pathway - a mechanism linked to female reproductive toxicity. The researchers established a benchmark dose lower confidence limit (BMDL5) of 9.55 μM for cell cycle disruption after 24 hours of exposure.

Perhaps most alarming is the evidence of transgenerational toxicity. A 2024 study found that prenatal exposure to environmentally relevant doses of BPA and BPS caused reproductive impairments that persisted across multiple generations (F1 to F3) in male mice, accompanied by epigenetic changes in neonatal spermatogonia.

3. Higher Bioavailability Than BPA

One of the most striking findings in BPS research involves its oral bioavailability. Toxicokinetic studies in animal models have shown that BPS has a 100-fold higher oral bioavailability compared to BPA. In practical terms, this means that for the same oral dose, the amount of BPS that reaches the bloodstream is approximately 100 times higher than BPA. The oral bioavailability of BPS has been measured at 57%, compared to just 0.50% for BPA.

This is a critical finding: even if BPS were slightly less potent than BPA on a per-molecule basis, the body absorbs far more of it, potentially resulting in greater overall exposure and health risk.

4. Oxidative Stress and Multi-System Effects

BPS has been linked to oxidative stress, inflammation, and cellular damage across multiple organ systems. A 2025 study on rats found that low-dose exposure to BPS disrupted oxidative balance in lung tissue. BPS and BPA showed comparable pro-inflammatory potential, both upregulating the production of free radicals and cytokine expression.

Other studies have linked BPS exposure to:

Cardiovascular effects: endothelial dysfunction via mitochondrial pathways
Thyroid disruption: interference with thyroid hormone function
Bone health: homeostatic imbalance in human bone marrow mesenchymal stem cells
Ovarian function: decreased ovarian reserve and impaired oocyte quality
Neurodevelopmental effects: potential impacts on brain development and behavior

5. Ocular and Dermal Toxicity

A 2025 study using the Hen's Egg Test-Chorioallantoic Membrane (HET-CAM) assay found that BPS had a stronger irritation impact than BPA, appearing as hemorrhage and coagulation, while BPA caused only moderate irritation. The researchers concluded that both BPA and BPS are serious toxic chemicals for human health, particularly for workers with higher exposure levels.

The "BPA-Free" Myth: What the Data Shows

The substitution of BPA with BPS has been remarkably effective - from a marketing perspective, at least. A Czech study published in 2025 found that over approximately a decade, urinary BPA levels in the population dropped by 28.6% in adults and 47.5% in children. But during the same period, BPS levels increased by 121.1% in adults and 90.0% in children.

The study's lead author noted: "The rise in BPS levels is worrisome because BPS was originally introduced as a safer alternative, but toxicological studies suggest it can pose similar health risks".

The bottom line: BPA restrictions have successfully reduced BPA exposure, but they have inadvertently increased exposure to BPS - a chemical that appears to carry many of the same risks.

A comprehensive review published in 2025 highlighted that most mainstream BPA alternatives exhibit estrogenic/anti-androgenic activity, metabolic disruption potential, reproductive toxicity, and neurodevelopmental effects similar to those of BPA. The authors warned against the "structural analogue substitution pitfall" - replacing one harmful chemical with another that is chemically similar and biologically comparable.

Regulatory Landscape: BPS Under Scrutiny

The scientific evidence has not gone unnoticed by regulators. In recent years, BPS has come under increasing regulatory scrutiny:

European Union: Under Commission Regulation (EU) 2024/3190, which took effect in January 2025, BPS is banned in food contact materials. The EU has also classified BPS as a reproductive toxicant (Category 1B) under the CLP Regulation.
United Kingdom: The Food Standards Agency (FSA) has proposed a ban covering BPA and its analogues, including BPS and BPF, in food contact materials. The FSA's preferred approach (Option 3) is a comprehensive prohibition, citing concerns around endocrine disruption and immunotoxicity.
California (USA): The Office of Environmental Health Hazard Assessment (OEHHA) has added BPS to the Proposition 65 list for reproductive toxicity, with the developmental toxicity designation effective December 2025.
Switzerland: BPS is included in the ban on hazardous bisphenols in food contact materials, effective July 2025.

These regulatory actions reflect a growing consensus: BPS is not a safe alternative to BPA, and regulating bisphenols as a group - rather than one chemical at a time - is essential to protect public health.

What This Means for You

If you work with BPS powder or BPS-containing materials, or if you manufacture products that use BPS, it's critical to stay informed about:

Regulatory changes: Bans and restrictions are expanding rapidly. The EU, UK, and California are just the beginning.
Health and safety protocols: With mounting evidence of BPS toxicity, proper handling procedures and exposure monitoring are essential - especially for workers.
Supply chain transparency: As BPS faces increasing restrictions, understanding the composition of your materials and seeking safer alternatives will become increasingly important.

Contact now