Note: This article is for general informational and editorial purposes only. It is not legal, toxicology, regulatory, or compliance advice. Businesses should consult qualified counsel or compliance professionals before making Proposition 65 decisions.
California’s Proposition 65 Spotlight Turns to Bisphenol S
California has a talent for making chemical compliance feel like a pop quiz you did not know was scheduled. The latest name showing up on the board is Bisphenol S, better known as BPS. The California Office of Environmental Health Hazard Assessment, or OEHHA, has added Bisphenol S under Proposition 65 for reproductive toxicity endpoints, including female reproductive toxicity, male reproductive toxicity, and developmental toxicity.
For consumers, this may sound like another mysterious chemical in the alphabet soup of modern life. For businesses, it is a regulatory alarm bell. BPS has been used in products and materials such as thermal receipt paper, shipping labels, product stickers, packaging, certain plastics, synthetic fibers, and other applications where it often appeared as a replacement for Bisphenol A, or BPA. In other words, BPS was sometimes the “BPA-free” understudy. Now the understudy has its own compliance drama.
The key point is simple: Proposition 65 does not ban BPS. Instead, it requires businesses to provide a clear and reasonable warning before knowingly and intentionally exposing individuals in California to significant amounts of a listed chemical. That means companies selling into California need to understand where BPS may appear, whether exposure occurs, whether a warning is required, and how that warning must be delivered before exposure happens.
What Is Bisphenol S?
Bisphenol S is a bisphenol compound structurally related to BPA. It has been used in manufacturing processes involving plastics, resins, thermal paper, and other commercial materials. One of the most common consumer-facing concerns involves thermal paper, the glossy-feeling paper used for many receipts, tickets, labels, packing slips, and shipping materials.
Thermal paper does not rely on ordinary ink in the way a home printer does. Instead, it uses heat-sensitive chemistry that darkens when exposed to a print head. BPS can function as a color developer in that process. That is why receipts can fade in a glove compartment faster than your memory of where you parked.
For years, many shoppers recognized “BPA-free” as a reassuring phrase. The problem is that removing BPA did not always mean removing bisphenols as a class. In some cases, BPA was replaced with BPS or other related chemicals. This kind of substitution has become a recurring theme in chemical regulation: one chemical receives scrutiny, industry moves to a replacement, and scientists later ask, “Did we just change the label on the same problem?”
How OEHHA Listed BPS Under Proposition 65
OEHHA’s listing of BPS developed in stages. BPS was first placed on the Proposition 65 list for female reproductive toxicity, effective December 29, 2023. The warning requirement for significant exposures tied to that endpoint took effect one year later, on December 29, 2024.
OEHHA later added the male reproductive toxicity endpoint, effective January 3, 2025. Under Proposition 65’s standard timing, warning obligations for significant exposures related to that endpoint began one year later. OEHHA then added the developmental toxicity endpoint, effective December 8, 2025, based on a determination by the Developmental and Reproductive Toxicant Identification Committee, known as DARTIC.
This matters because the BPS listing is no longer a narrow, single-endpoint issue. It now covers major reproductive toxicity categories under Proposition 65. For companies that manufacture, distribute, package, label, ship, or sell products in California, that widens the compliance lens. It is not enough to ask only whether the finished product contains BPS. Businesses also need to ask whether BPS may be present in related items that accompany a product purchase, such as receipts, labels, tags, stickers, shipping materials, packaging, instructions, or manuals.
Why Proposition 65 Matters for Businesses
California Proposition 65, formally the Safe Drinking Water and Toxic Enforcement Act of 1986, requires the state to maintain a list of chemicals known to cause cancer, birth defects, or other reproductive harm. Once a chemical is listed, businesses generally have 12 months to comply with warning requirements and 20 months to comply with restrictions on discharges into drinking water sources.
For BPS, the practical business question is not simply, “Is the chemical listed?” It is, “Could our product, label, receipt, packaging, or related materials expose someone in California to BPS at a level that requires a warning?” That question can be surprisingly tricky. A product may not contain BPS in its main material, yet the receipt, adhesive label, UPC sticker, packing slip, or shipping label might.
That is the compliance equivalent of checking the front door while the raccoon sneaks in through the dog flap. BPS may enter the risk conversation through the less glamorous parts of commerce: the label stuck to a box, the thermal receipt handed across a counter, or the product sticker a customer touches before tossing it into the recycling bin.
What “Clear and Reasonable Warning” Means
A Proposition 65 warning must be provided before exposure occurs. For consumer products, warnings may appear on labels, signs, websites, catalogs, or other approved communication methods, depending on the exposure scenario. Newer changes to short-form warning rules also make chemical identification more important, which means businesses relying on generic warnings should review whether their language still fits current requirements.
For BPS in thermal receipts, timing is especially important. A warning printed on the receipt itself may come too late because the customer may already have handled the receipt by the time they read it. OEHHA has indicated that warnings near cash registers may be more appropriate in situations where customers can choose an emailed receipt instead of a printed one.
Receipts, Shipping Labels, and the Surprise Compliance Zone
One of the biggest real-world developments is OEHHA’s clarification that items accompanying a consumer purchase can create consumer product exposures. That includes receipts, labels, tags, product stickers, shipping materials, packaging, and manuals, whether the purchase happens in a store or online.
This guidance is important because it pushes compliance teams beyond the product itself. A retailer selling a ceramic mug may focus on lead or cadmium in the mug glaze, but if the printed receipt or shipping label contains BPS, the compliance question shifts. The exposure may arise from the purchase experience, not the coffee cup. Suddenly the humble receipt has main-character energy.
Online sellers should also pay attention. Shipping labels, product stickers, packing slips, return labels, and warehouse-applied tags can all become part of the exposure review. For e-commerce companies, this means the compliance audit should not stop at product specifications. It should include fulfillment materials, third-party logistics practices, label vendors, receipt systems, and packaging suppliers.
Retail Workers and Occupational Exposure
Consumers may touch a receipt briefly. Retail workers may handle hundreds of receipts, labels, or packing slips during a shift. OEHHA has encouraged businesses to consider not only consumer product exposure but also occupational exposure for workers handling BPS-containing paper. This is a practical reminder that compliance is not just about avoiding warning letters. It is also about reducing routine exposure in the workplace.
What Products and Materials Could Be Affected?
BPS-related compliance reviews may be relevant to a wide range of industries. The most obvious category is thermal receipt paper, but the issue can reach much farther. Businesses may need to evaluate:
- Point-of-sale receipt paper
- Shipping labels and return labels
- Product stickers, barcode labels, and UPC labels
- Thermal tags used in retail, logistics, grocery, and apparel
- Packaging inserts, manuals, and printed materials
- Plastics, coatings, resins, and synthetic fibers that may involve BPS chemistry
- Items marketed as BPA-free without clear confirmation that they are also BPS-free
Businesses should avoid assuming that “BPA-free” automatically means “bisphenol-free.” That assumption has caused plenty of regulatory heartburn. A more careful approach is to request supplier declarations, review safety data sheets, confirm chemical composition, test where needed, and document the decision-making process.
Safe Harbor Levels and Exposure Assessments
Proposition 65 is exposure-based, not merely presence-based. A listed chemical can be present in a product or material, but a warning may not be required if the exposure is low enough under the law. OEHHA develops safe harbor levels for many chemicals, including No Significant Risk Levels for carcinogens and Maximum Allowable Dose Levels for reproductive toxicants.
When there is no OEHHA-established safe harbor level for a chemical, businesses may need to determine whether the anticipated exposure level poses no significant risk or is below the level requiring a reproductive toxicity warning. That analysis can involve toxicology, exposure modeling, product use assumptions, dermal transfer data, and other technical information. Translation: this is not a “vibes and spreadsheets” exercise.
Because BPS exposure from thermal paper may involve direct skin contact, the assessment may need to consider how often the paper is handled, how long it is held, whether workers handle it repeatedly, and whether transfer to skin or other surfaces occurs. A cashier, warehouse worker, or fulfillment employee may have a very different exposure profile than a customer who declines a receipt and walks away feeling environmentally virtuous.
Practical Compliance Steps for Companies
Companies that sell products in California or ship to California customers should treat the BPS listing as a prompt to review supply chains and warning practices. The best approach is proactive, documented, and boring in the best possible way. Regulators and plaintiff attorneys love gaps; compliance teams love receipts, but preferably digital ones.
1. Map Where BPS May Appear
Start by identifying all materials that may contain BPS. Include the product, packaging, labels, tags, inserts, shipping materials, receipts, and point-of-sale systems. Ask suppliers direct questions. “Is this BPA-free?” is not enough. Ask whether the material contains BPS or any bisphenol-based developer.
2. Review Vendor Documentation
Request updated supplier declarations, technical data sheets, safety data sheets, and chemical compliance certificates. If a vendor cannot answer basic BPS questions, that is not automatically proof of a problem, but it is a sign that more verification may be needed.
3. Consider Testing and Exposure Analysis
Testing can help identify whether BPS is present. Exposure analysis helps determine whether a warning obligation exists. These are related but not identical. A lab result showing presence does not always answer the legal exposure question, and a clean certificate from three years ago may not reflect current production.
4. Update Warning Systems
If a warning is required, companies should evaluate where and how it appears. For in-store receipts, a sign near the register may be more useful than text printed on the receipt. For online sales, warnings may need to appear before purchase completion. For shipped goods, companies should consider whether labels, stickers, packaging, or inserts create their own exposure issues.
5. Explore BPS-Free Alternatives
Businesses may reduce risk by switching to phenol-free thermal paper, electronic receipts, BPS-free labels, or alternative printing technologies. Reformulation and substitution should be handled carefully. The goal is not to play chemical whack-a-mole by replacing BPS with another compound that becomes tomorrow’s headline.
What Consumers Should Know
For consumers, the BPS listing is not a reason to panic every time a cashier asks whether you want a receipt. It is a reason to make small, practical choices. Choose digital receipts when possible. Avoid crumpling receipts in your hand for long periods. Keep receipts away from food. Wash hands after handling thermal paper, especially before eating. Workers who handle receipts constantly may want to ask employers about BPS-free paper or protective practices.
Proposition 65 warnings are often criticized because they are everywhere in California, from parking garages to coffee shops. Still, the law’s purpose is transparency. A warning does not necessarily mean a product is unsafe in ordinary use; it means a business believes an exposure to a listed chemical may occur. The smarter response is not fear. It is informed choice.
Why the BPS Listing Signals a Bigger Trend
The BPS listing reflects a broader regulatory shift toward scrutinizing chemical substitutes. In the past, industry often moved from one restricted chemical to a structurally similar alternative. That approach can work when the alternative is genuinely safer. It can backfire when the substitute shares similar hazard concerns.
Bisphenols are a good example. BPA became a household name, and “BPA-free” became a marketing phrase. But consumers were rarely told what replaced BPA. BPS entered many applications because it performed well technically. Now regulators, scientists, retailers, and advocacy groups are asking whether chemical substitution should be evaluated more carefully before it spreads across millions of everyday items.
For businesses, the lesson is clear: safer substitution should be evidence-based. The cheapest replacement is not always the lowest-risk replacement. A procurement decision made quietly in a paper supply contract can become a legal, reputational, and operational issue later.
Experience Notes: What This Looks Like in Real Business Life
In practical compliance work, BPS is the kind of issue that hides in plain sight. Imagine a retailer that sells clean-label home goods, carefully audits paints, coatings, adhesives, and packaging inks, and proudly removes BPA from its product claims. Everything looks tidy until someone asks about the thermal receipt rolls at checkout. The team calls the receipt vendor. The first response is, “They are BPA-free.” The second question is, “Are they BPS-free?” Silence enters the chat.
That silence is where real compliance begins. Companies often discover that the highest-risk item is not the hero product on the shelf, but a supporting material no one thought to review. A shipping label may be sourced by a warehouse partner. A product sticker may be selected by a packaging broker. A return label may be printed by a third-party logistics provider. A marketplace seller may not even know what paper stock is used after an order leaves the fulfillment center. BPS teaches a valuable lesson: supply chains have corners, and corners collect surprises.
Another common experience involves warning placement. A business may think, “Fine, we will print the warning on the receipt.” That sounds logical until the timing problem appears. If the customer must touch the receipt to see the warning, the exposure may already have happened. In real-world retail settings, this pushes teams toward register-area signage, digital receipt prompts, point-of-sale screen notices, or checkout messaging before the customer chooses a printed receipt. It is a small operational change, but it requires coordination between legal, store operations, IT, procurement, and training. In other words, it is a group project. Everyone’s favorite.
For online sellers, the experience can be even more tangled. A company may update product pages but forget about packing slips. It may change labels at one fulfillment center but not another. It may ship from multiple vendors using different label materials. A California order fulfilled from Nevada or Texas still needs California compliance thinking if the product is sold into California. The internet did not repeal Proposition 65; it just made the paper trail longer.
Retail workers also bring a practical perspective that spreadsheets miss. A customer touches one receipt. A cashier touches hundreds. A warehouse employee may peel, stick, scan, and handle labels all day. When companies move from “How do we avoid a notice?” to “How do we reduce unnecessary exposure?” the conversation becomes more useful. Digital receipts, phenol-free paper, gloves for certain tasks, better handwashing access, and supplier upgrades can all be part of a sensible plan.
The best experience-based takeaway is this: do not wait for a notice of violation to learn what is in your paper, labels, and packaging. Ask now. Document answers. Replace questionable materials when feasible. Train teams before warnings go live. And never assume that a product claim like “BPA-free” tells the whole story. Sometimes the sequel is called BPS, and as California has made clear, the sequel deserves its own review.
Conclusion
California OEHHA’s addition of Bisphenol S under Proposition 65 is more than a technical listing update. It is a reminder that chemical compliance now reaches deep into the ordinary materials that make commerce work: receipts, labels, stickers, packaging, shipping supplies, and replacement chemicals once treated as safer by default.
For businesses, the path forward is practical: identify where BPS may appear, review supplier data, assess exposure, update warnings if required, and consider BPS-free alternatives. For consumers, the message is equally straightforward: choose digital receipts when possible, reduce unnecessary handling of thermal paper, and use Proposition 65 warnings as information rather than panic fuel.
The BPS listing also carries a bigger lesson. Chemical substitution should not be a guessing game with better branding. If a material is replacing a known concern, companies should ask whether it is truly safer, not merely newer. In compliance, as in life, “different” and “better” are cousins, not twins.
