California Prop 65 Compliance for Product Sellers

A customer in Sacramento opens a parcel from your online shop and finds no warning label. Nothing looks wrong. Six months later a letter arrives from a law firm you have never heard of, citing California's Safe Drinking Water and Toxic Enforcement Act of 1986, better known as Proposition 65. This is not a rare event: private enforcers filed 593 separate 60-day notices in October 2025 alone. The rule catches out sellers who have never set foot in California, because it applies to anyone whose product reaches a Californian buyer, not just businesses based there.

What is Prop 65, and does it really apply to sellers outside California?

Proposition 65 requires a "clear and reasonable warning" before knowingly exposing anyone in California to a chemical the state has listed as causing cancer, birth defects, or other reproductive harm. It applies to any business with ten or more employees that is "doing business" in California, and that phrase is read broadly. Courts and OEHHA guidance treat a company as doing business in the state the moment its products reach Californian consumers, whether that happens through your own website, a marketplace listing, or a wholesale distributor who ships nationwide on your behalf.

That is the detail that trips up online sellers and importers. You do not need a warehouse, an office, or a single employee in California. If your product can end up in a Californian's hands, and it contains a listed chemical above the relevant threshold, the warning duty follows the product there. A brand based in Ohio, Texas, or overseas selling through Amazon or Shopify has exactly the same exposure as a company headquartered in Los Angeles, because Prop 65 tracks the customer's address, not the seller's.

Who keeps the list, and how big is it now?

California's Office of Environmental Health Hazard Assessment, OEHHA, maintains what is formally called the Proposition 65 list. It has grown a long way from its 1987 starting point and now runs to more than 900 chemicals, spanning industrial solvents, heavy metals, pesticides, pharmaceuticals, and everyday plasticisers found in cables, packaging, and moulded plastic parts. OEHHA is required to update it at least once a year, and it typically adds several substances at a time. Its most recent update, in December 2025, added bisphenol S (BPS) and N-methyl-N-formylhydrazine, both now subject to the usual one-year grace period before warnings become mandatory for products containing them.

Because the list only grows, a product that cleared Prop 65 review two years ago is not automatically clear today. A component supplier can change a plasticiser, a colourant, or a stabiliser without telling you, and that change alone can turn a compliant product into one that needs a warning. Treating a Prop 65 check as a one-off task, rather than something to revisit whenever you reformulate or resource a component, is one of the most common ways sellers end up on the wrong end of a notice. For a quick plain-English definition of the term, see our Prop 65 glossary entry.

What actually triggers a warning?

A warning is required only for a "knowing and intentional" exposure to a listed chemical above OEHHA's safe harbor threshold. For carcinogens, this is expressed as a No Significant Risk Level; for reproductive toxicants, it is a Maximum Allowable Dose Level. Below those levels, no warning is legally required at all, though many businesses choose to warn anyway rather than pay for the testing needed to prove they are under the threshold.

In practice, this means three separate questions decide whether you need a label: does the product contain a listed chemical, is the exposure level above the relevant safe harbor threshold, and did you know, or should you reasonably have known, that the chemical was present. That third question is where a lot of businesses get caught, because "should have known" does not require deliberate concealment. Buying a component from a factory without asking what is in it does not protect you; it just means you found out later, usually from a plaintiff's lawyer rather than your own supplier.

Say you are a small US brand selling phone accessories through a marketplace, sourcing charging cables from a factory in Shenzhen. A batch of 2,000 cables uses a PVC sheath the factory has always supplied, and nobody on your side has ever asked for a material breakdown. A compliance testing lab commissioned by a rival, or simply a private enforcer running routine screening, finds the sheath contains DEHP, a phthalate plasticiser, above the safe harbor level. Roughly one in eight of your marketplace orders ships to California addresses. Every one of those sales, going back a year, is now a potential violation, and you had no warning label on any of them because nobody in your supply chain flagged the plasticiser. This is exactly the profile of product category that shows up repeatedly in enforcement data: bags, cases, and small electronics accessories, alongside jewellery, receipts, and glassware.

What does a compliant warning label actually look like?

OEHHA's regulations set out "safe harbor" warning methods that, if followed exactly, are deemed to satisfy the law. The standard long-form product warning reads: "WARNING: This product can expose you to chemicals including [name of one or more chemicals], which is known to the State of California to cause cancer [and/or] birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov." It must appear with a black exclamation point inside a yellow equilateral triangle with a black border, and the word "WARNING" must be bold, capitalised, and in a type size no smaller than the rest of the text.

Shorter warnings are available for small packaging, but amendments that took effect on 1 January 2025 tightened them: a short-form warning must now name at least one chemical for each risk endpoint (cancer, reproductive harm, or both) rather than relying on the generic wording alone. Existing stock made before that date has a grace period, with full compliance required for anything manufactured after 1 January 2028, but new product runs should already be using the updated wording.

For online sales specifically, the warning has to appear before the sale completes, not just inside the box once it arrives. That usually means putting the warning directly on the product listing page, behind a clearly labelled hyperlink such as "California Prop 65 Warning" on the listing, or as a pop-up triggered when a buyer enters a California address or zip code at checkout. A warning printed only on the product itself, discovered after the customer has already paid, does not satisfy the requirement.

The table below summarises the main warning formats and where each one applies.

Why citizen suits make this different from EU-style compliance

If you have worked with the EU's GPSR or REACH, you are used to compliance being enforced by government market surveillance authorities who set priorities, run inspections, and issue corrective notices. Prop 65 works on a fundamentally different model. Section 25249.7 of the underlying statute lets any private individual, acting "in the public interest," file a 60-day notice alleging a violation and, if the business does not fix the problem within that window, bring a lawsuit and collect a share of the penalty.

That mechanism has created a specialised plaintiffs' bar built around Prop 65 enforcement. Civil penalties run up to $2,500 per violation per day, calculated per unit sold across the exposure period, split 75% to the California Attorney General and 25% to the private enforcer who brought the case. Many cases settle well before trial, often in the low tens of thousands of dollars once legal fees are included, because contesting a well-supported notice can cost more than paying it. Lead in decorative ceramics, phthalates in bags and accessories, and bisphenol S on thermal receipt paper have all been recurring targets in recent notice data, alongside more established categories like jewellery and vinyl products.

This is worth sitting with if your only compliance experience comes from EU-style, regulator-enforced regimes, where a national authority decides when and whether to act. Under Prop 65, anyone can act, there is no regulator gatekeeping which notices get filed, and volume, not severity, drives most of the enforcement activity. A small business shipping a modest number of units into California carries the same theoretical exposure per unit as a large retailer; it simply has fewer units for a penalty calculation to multiply against.

Do I need lab testing before I can sell into California?

Not automatically, but you need a credible basis for whatever conclusion you reach. If your product genuinely contains no listed chemical, and you can show that through supplier material declarations, you may not need testing at all. If a component realistically could contain something like lead, phthalates, or a listed flame retardant, and you have no documentation proving otherwise, testing is the only way to know your actual exposure level rather than guessing. Given that a 60-day notice can arrive based on someone else's testing of your product, it is generally cheaper to test proactively on your own terms than to find out reactively on a plaintiff's schedule.

Building a practical Prop 65 process

The workable approach for most small and mid-size sellers starts with mapping which of your products realistically could contain a listed chemical, based on material type rather than assumption: plastics, metals, and coated or printed items are the highest-risk categories. From there, request supplier material declarations for anything that scores as a risk, and treat "we've never had a complaint" as no answer at all, since it says nothing about actual chemical content. Where a declaration cannot rule out a listed substance with confidence, commission independent testing rather than relying on the factory's word alone, particularly for accessories, cables, and printed packaging, which show up disproportionately often in notice data.

Once you know where you stand, decide deliberately whether to warn or to rely on staying under the safe harbor threshold, because "warn on everything" is a valid strategy but it is not free: overwarning can undermine consumer trust and, in some circumstances, itself invite scrutiny if a warning is added without any listed chemical actually being present. Build the warning into your listing templates so every new product variant inherits it automatically, rather than relying on someone remembering to add it product by product. If you are also managing importer duties from Chinese suppliers, fold the Prop 65 material check into the same supplier questionnaire you already use for other compliance documentation, since the two overlap heavily in practice.

Prop 65 is not going away, and the chemical list is not going to stop growing. Building a habit of checking new products and reformulated materials against the current list, rather than treating an old assessment as permanent, is the difference between a five-minute label fix and a legal letter with your business's name on it. Our free requirements checker can help you work out which US, UK, and EU product rules apply to your specific product before you commit to a production run.