Prop 65 Warning Requirements: Do You Need One?

California's Proposition 65 warning requirements trip up more importers than any other US regulation. Here's a practical decision framework so you can figure out what applies to your products — and what your labels actually need to say.

You're browsing Amazon and notice a brass doorknob with a cancer warning label. A doorknob. Welcome to Proposition 65.

If you've ever imported consumer products that end up in California — and statistically, they do — you've probably encountered Prop 65 in some form. Maybe a retailer asked for a Prop 65 compliance letter. Maybe your freight forwarder flagged it. Maybe you just saw the warnings on every competitor's listing and thought, "Do I need one of those?"

The answer, as with most things in compliance, is "it depends." But unlike most regulatory gray areas, Prop 65 actually has a fairly clear decision framework once you understand how it works. Let's walk through it.

What Is California Proposition 65?

Proposition 65, officially the Safe Drinking Water and Toxic Enforcement Act of 1986, requires businesses to warn California consumers about significant exposures to chemicals that cause cancer, birth defects, or other reproductive harm. The state maintains a list of these chemicals — currently over 900 — managed by the Office of Environmental Health Hazard Assessment (OEHHA).

The key word there is "significant." Prop 65 doesn't ban products containing listed chemicals. It requires a clear and reasonable warning when a product exposes someone to a listed chemical above certain threshold levels. For carcinogens, that threshold is called the No Significant Risk Level (NSRL). For reproductive toxicants, it's the Maximum Allowable Dose Level (MADL).

Here's the twist that catches most importers off guard: the burden of proof is on you. If someone sues (and Prop 65 has a private right of action, meaning anyone can sue), you have to prove your product's exposure is below the threshold. You don't get the benefit of the doubt. This is why so many companies slap warnings on everything — it's cheaper than testing, and it's definitely cheaper than defending a lawsuit.

Does Prop 65 Apply to You? A Practical Decision Framework

Not every importer needs to lose sleep over Prop 65. Here's a quick decision tree:

1. Does your product reach California? If you sell on Amazon, Walmart.com, or any national retailer — yes. If you sell D2C and ship to California — yes. If you only sell in-person at a single store in Maine — maybe not, but good luck guaranteeing that forever.
2. Does your business have 10 or more employees? Companies with fewer than 10 employees are exempt. This is based on total headcount, not California employees.
3. Does your product contain or expose users to a listed chemical? This is the big question. Common culprits: lead in metals and ceramics, cadmium in jewelry and pigments, phthalates in soft plastics, BPA in food contact materials, formaldehyde in textiles and wood products.
4. Is the exposure above the safe harbor level? If your product contains a listed chemical but exposure is below the NSRL or MADL, no warning is required. But proving that requires testing.

If you answered yes to the first three and aren't sure about the fourth, you either need to test or you need to warn. Most mid-market importers choose the warning route because it's more practical — but there are good reasons to test, which we'll get to.

Safe Harbor Warnings: Short-Form vs Long-Form

In 2018, California overhauled its Prop 65 warning requirements. The old days of a vague "this product contains chemicals known to the State of California to cause cancer" are over. Well, sort of. The new regulations introduced two formats:

Long-form warning: Must include the word "WARNING" in all caps and bold, a triangle warning symbol, the specific chemical name(s), the type of harm (cancer, reproductive harm, or both), and a URL to www.P65Warnings.ca.gov. Example:

WARNING: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Short-form warning: For products with limited label space. Must still include "WARNING" in all caps and bold, the triangle symbol, the name of at least one chemical, and the P65Warnings URL. Example:

WARNING: Cancer and Reproductive Harm — Lead — www.P65Warnings.ca.gov

The short-form option is a lifesaver for importers dealing with small products or multilingual packaging where label real estate is at a premium. But here's the catch: short-form warnings can only be used when the product or packaging doesn't have enough space for the long-form version. You can't just pick whichever you prefer.

The Chemicals Importers Encounter Most Often

Out of 900+ chemicals on the Prop 65 list, a handful are responsible for most of the compliance headaches importers face. Here's the greatest hits:

• Lead — the undisputed champion. Found in brass, solder, ceramics, vinyl, painted surfaces, and electronics. If you import anything metal, you're probably dealing with lead.
• Cadmium — common in jewelry, pigments (especially reds and yellows), plastics, and rechargeable batteries.
• Phthalates (DEHP, DINP, others) — plasticizers used in soft PVC, vinyl products, some inks and adhesives. Also regulated under CPSIA for children's products.
• Bisphenol A (BPA) — found in polycarbonate plastics, epoxy linings in cans, thermal receipt paper.
• Formaldehyde — used in textile finishes, composite wood products, and some adhesives.
• Acrylamide — forms during high-temperature cooking processes; relevant for food importers.

If your product category intersects with any of these chemicals, Prop 65 is almost certainly on your radar — or should be. And if you're managing compliance across multiple regulations like PFAS disclosure requirements at the same time, the overlap gets interesting fast.

Prop 65 for Amazon and E-Commerce Sellers

This is where things get especially tricky for modern importers. Prop 65 requires that warnings be provided before or at the time of purchase. For brick-and-mortar retail, that means on the product or shelf. For e-commerce, that means on the product listing itself — before the customer clicks "Buy."

Amazon has its own Prop 65 compliance requirements. If you sell on Amazon and your product requires a warning, you need to:

• Include the Prop 65 warning text in your product listing (typically in the product description or a dedicated attribute field)
• Include the warning on the product itself or its packaging
• Some sellers also add warnings to packing slips or package inserts, though this alone doesn't satisfy the "before purchase" requirement

Amazon has been tightening enforcement. Listings without Prop 65 warnings for products that clearly need them can be flagged, suppressed, or removed. And California's Attorney General has brought enforcement actions against online sellers who failed to provide adequate warnings.

If you sell on Shopify, WooCommerce, or any other platform, the same rules apply. The warning needs to be visible to the customer before they complete the purchase. A tooltip, a dedicated section on the product page, or a checkbox acknowledgment at checkout are all approaches sellers use.

How to Generate Compliant Prop 65 Labels

Getting the label right requires attention to detail. Here's the practical checklist:

1. Identify the chemicals — Review your product materials, request Safety Data Sheets (SDS) from suppliers, and/or get third-party testing done. You need to know which listed chemicals are present.
2. Determine the warning type — Cancer, reproductive harm, or both. This depends on which chemical(s) you've identified and their classification on the OEHHA list.
3. Choose long-form or short-form — Based on available label space. When in doubt, use long-form.
4. Include all required elements — "WARNING" in bold caps, the triangle symbol, chemical name(s), harm type, and the P65Warnings.ca.gov URL.
5. Apply it everywhere it's needed — Product, packaging, product listing (for e-commerce), catalog, or any other point-of-sale material.

The formatting requirements are surprisingly specific. The warning symbol has to be a particular size relative to the text. The word "WARNING" needs to be in a specific format. And if you're producing labels for multiple products with different chemicals, managing this manually across your catalog gets old very quickly.

This is one of the reasons we built Prop 65 label generation directly into Aleph. You tell the platform which chemicals are relevant to each product family, and it produces labels with the correct current safe harbor language, formatted to spec. When California updates the warning requirements (and they do), the templates update too. No more wondering if your label text is still current.

And because Prop 65 is rarely the only regulation an importer deals with, Aleph ties your Prop 65 warnings into the same platform where you manage your Children's Product Certificates, your FSVP documentation, and your PFAS disclosures. One product, one dashboard, every regulation that applies.