Proposition 65 for Supplement Brands: Warnings, Testing, and Risk

A supplement can be fine for sale in forty-nine states and still land you a legal notice in California. That sentence surprises almost every brand the first time it happens, because it doesn’t fit the mental model people bring to compliance. Proposition 65 is not a purity standard. It does not set a maximum amount of lead your product is allowed to contain. It is a warning law, a right-to-know statute, backed by an enforcement engine that runs on private lawsuits rather than government inspectors. The practical result is that a batch whose heavy-metal content is unremarkable for national commerce can trigger a warning obligation in California, and a firm you have never heard of can be the one to point it out, after buying your product off a shelf or a marketplace and sending it to a lab.

This is the part of supplement compliance that is least like the rest of it, and the part where a testing decision made on the manufacturing floor months earlier decides how exposed you are. Here is how Proposition 65 actually works for a supplement, which chemicals put you in its path, why the enforcement model is the real risk, and where the line sits between what a manufacturer can settle for you with data and what only your counsel can decide.

Educational overview: not legal, regulatory, or medical advice. Requirements change and vary by jurisdiction and sales channel. Last reviewed July 2026.

Short answer. Proposition 65 (California’s Safe Drinking Water and Toxic Enforcement Act of 1986) requires a “clear and reasonable” warning before a business knowingly exposes a Californian to a listed chemical above its safe-harbor level. For supplements the usual triggers are three heavy metals with very low oral safe-harbor levels: as of mid-2026, lead 0.5 µg/day and cadmium 4.1 µg/day (reproductive MADLs) and inorganic arsenic 10 µg/day (cancer NSRL), per California OEHHA. It is enforced mostly by private “bounty-hunter” plaintiffs who, after a 60-day notice and a certificate of merit, can seek penalties up to $2,500 per violation per day plus attorney fees. The warning decision is a legal one, but it starts as a testing question: test the finished product, and if every result sits under the applicable level, there is no warning obligation to decide.

Best for: Brand owners and Amazon/ecommerce sellers whose products reach California, which, on a national marketplace, is effectively all of them.

Key decision: Whether your finished product clears the applicable safe-harbor levels (a testing question your manufacturer answers), and if it does not, whether to reformulate, re-source, or warn (a legal question your counsel answers).

Apollo path: Apollo screens incoming materials at receiving and tests finished batches per lot through vetted ISO/IEC 17025 third-party labs, with itemized per-metal Certificates of Analysis, the verified numbers your counsel needs to make the warning call. Request a Manufacturing Quote → /quote

One boundary up front, because it matters more here than almost anywhere. This explains how Proposition 65 works; it is not legal advice, and whether any specific result obligates a warning is a question for your counsel. Apollo produces the number: the verified, itemized contaminant data on your batch, and the incoming-material discipline behind it. What that number requires of your label, and whether an exemption applies to your product, is your counsel’s call. We support; your counsel decides.

How Proposition 65 actually works: list, level, warning

Strip away the folklore and Prop 65 is a three-part machine. Understanding the three parts tells you exactly where a supplement is exposed and where a manufacturer can help.

The list. California’s Office of Environmental Health Hazard Assessment (OEHHA) maintains a list of chemicals “known to the state” to cause cancer or reproductive harm. It is long (hundreds of entries) and it grows: the version referenced by OEHHA’s safe-harbor tables carries a list date of April 21, 2023, and chemicals are added over time. Being on the list is not, by itself, the problem. Lead, inorganic arsenic, and cadmium are all listed, and all three ride into supplements through ordinary raw materials, not through anything a formulator adds on purpose.

The level. For many listed chemicals OEHHA has established a “safe-harbor” number, the exposure below which no warning is required. For cancer-causing chemicals it is a No Significant Risk Level (NSRL); for reproductive toxicants it is a Maximum Allowable Dose Level (MADL). OEHHA’s own guidance is explicit that exposures below the safe-harbor level are exempt from the warning requirement. This is the pivot the whole thing turns on: a safe-harbor level is not a “limit” in the sense of a legal maximum your product may contain; it is the threshold that decides whether you owe a warning. Stay under it and you have no warning duty. Go over it and you have a decision to make.

The warning. When a business “knowingly and intentionally” exposes a person in California to a listed chemical above the safe-harbor level, it must give a clear and reasonable warning first. The obligation sits on the business, and (importantly for small brands) it applies to businesses with ten or more employees; California’s Health & Safety Code exempts anyone employing fewer than ten. There is no government pre-approval of your product, no California certificate, no filing that clears you in advance. You are expected to know where your product sits and to warn when the law requires it.

That structure is why a Prop 65 problem is, at its root, a testing problem wearing a legal coat. You cannot know whether you owe a warning until you know where your product’s exposure sits against the applicable level, and you cannot know that without testing the finished product against the right number.

The three chemicals that put supplements in the crosshairs

Prop 65 covers a long list, and a handful of other entries touch food: acrylamide, certain botanical constituents, mercury in some marine ingredients. But for the average supplement, three heavy metals do nearly all the work, because they arrive with ordinary raw materials and their safe-harbor levels are strikingly low. As of mid-2026, per OEHHA’s published safe-harbor levels:

Values as of mid-2026, from California OEHHA’s Proposition 65 safe-harbor tables. These are exposure levels from your product, per day, at the labeled serving. Verify the current figures against OEHHA before acting, and route any warning decision to your counsel.

The reason these numbers matter so much is the gap between them and every other yardstick a supplement is measured against. Prop 65’s lead safe-harbor of 0.5 µg/day sits far below the reference points that govern general US commerce; it is often described as roughly twenty times stricter than the federal side, though the exact multiple depends on which federal number you compare against and which body set it. The direction is not in dispute: California’s warning threshold is dramatically lower. A product whose lead content raises no flag for national sale can still cross the 0.5 µg line at its serving size and put you in warning territory.

Where do the metals come from? Not the formula. They ride in from the soil a botanical grew in, from a mineral or earth-derived ingredient, from water, occasionally from equipment, and they vary lot to lot because the dirt varies. Root powders, leafy greens, cocoa, and rice-derived ingredients are frequent lead, cadmium, and inorganic-arsenic carriers; plant proteins draw scrutiny because a large serving of a soil-grown crop is a large dose of whatever that crop accumulated. That whole story is the subject of a companion piece on heavy metals in supplements: how the metals get in, how they are measured by ICP-MS to parts per billion, why inorganic arsenic has to be tested by speciation rather than as “total arsenic,” and how the same batch is measured against three different bars (FDA, USP, and Prop 65). The Prop 65 point here is narrower: these three are the entries most likely to force a warning decision, and the level that governs that decision is the lowest one in the room.

Why the enforcement model is the real risk

Most compliance regimes are enforced by a regulator who inspects, cites, and gives you a chance to fix. Prop 65 is different, and the difference is the whole reason it feels like an ambush. The statute lets the California Attorney General, district attorneys, and city attorneys (in cities over 750,000 people) bring actions, but it also authorizes enforcement by private parties acting “in the public interest.” That private-enforcement provision is the engine. The Attorney General publishes annual Proposition 65 settlement reports, and those public records are dominated year after year by private actions, not government ones. A cottage industry of plaintiff firms buys consumer products (including supplements, often straight off a national marketplace), sends them to a lab, and pursues the ones that test over a safe-harbor level without a warning.

The mechanics are worth knowing because they explain both the risk and the pace at which it moves:

• The 60-day notice. A private enforcer must serve a “60-day notice of violation” on the business and on the Attorney General and appropriate prosecutors before filing suit. This notice, not a government letter, is usually a brand’s first sign of trouble. It typically arrives with the plaintiff’s own test data showing a listed chemical over its level.
• The certificate of merit. The private enforcer must also provide a certificate of merit stating that they have consulted with the relevant experts and believe there is a reasonable, meritorious basis for the action: a threshold meant to filter frivolous notices, tightened by recent California legislation.
• The penalties. A violation can carry a civil penalty of up to $2,500 per day for each violation. The number that actually moves settlements, though, is often the plaintiff’s attorney fees, which the statute allows a prevailing enforcer to recover (which is why the large majority of these matters settle rather than litigate).

Put those pieces together and the risk profile is unusual: there is no inspection to pass and no inspector to satisfy, the party enforcing the law is financially motivated to find you, and the trigger is a lab result on a product you already shipped. That is precisely why the defense has to be built before the product ships, in the form of data that tells you and your counsel where you stand. A brand that can show a current, itemized, per-metal Certificate of Analysis on the lot, measured against the applicable levels, is in a very different position from one reacting to a stranger’s test result with no data of its own. (None of the figures above is a target to aim for; they are the enforcement facts your counsel weighs. Confirm current penalty and procedure details against the statute, because they change.)

The “naturally occurring” trap: why “it’s a natural botanical” rarely saves you

Here is the assumption that sinks a surprising number of brands: my product is a natural botanical, so any lead in it is “naturally occurring” and therefore exempt. It feels right, and it is mostly wrong.

There is a naturally-occurring allowance in California’s Prop 65 food regulations: the law recognizes that some listed chemicals are natural constituents of food or unavoidably present from the environment, and to the extent a chemical is genuinely naturally occurring, an exposure to it can fall outside the warning requirement. But the allowance is narrow, and the catch is what disqualifies a chemical from it. As the American Herbal Products Association (AHPA) explains in its Prop 65 guidance for the supplement trade, a chemical is generally not treated as naturally occurring when it is present as a result of human activity: historic soil contamination from leaded gasoline, past or present pesticide use, industrial fallout, or the manufacturing process itself. Because most of the lead and cadmium that ends up in botanicals traces back to exactly those human-activity sources, the “it’s natural” allowance rarely rescues a real-world supplement.

Two things follow. First, do not treat the naturally-occurring exemption as a self-assessment you can make from the label. Whether it applies to a specific product, ingredient, and supply chain is a fact-specific legal determination: the kind of question your counsel answers with your sourcing records, not the kind you settle with a shrug and the word “natural.” Second, the exemption’s existence is not a reason to skip testing; it is a reason to have the testing data in hand, because the analysis your counsel runs depends on knowing the numbers and the sources. Whether the allowance applies is your counsel’s call. Producing the data that call depends on is the manufacturer’s.

Warning or no warning: the decision, and why it’s a testing decision first

The question every brand actually wants answered (“do I need a Prop 65 warning?”) has a structure, and most of that structure is a testing question that resolves before a legal one begins. Walk it in order:

1. Does the product reach California? On a national marketplace, assume yes. You cannot reliably fence California out of ecommerce, so plan as if every SKU is sold there.
2. Test the finished product, at the serving size, against the applicable safe-harbor levels. This is the manufacturer’s step. The exposure that matters is per day at the labeled serving, so the number is your finished product’s content, not a raw ingredient’s, converted to a daily exposure. Lead and cadmium are measured against their MADLs; arsenic must be tested as inorganic arsenic (by speciation), because “total arsenic” is not the figure the level is written against. Metals stack across a multi-ingredient formula, so the serving as a whole is what’s measured. The mechanics of that testing live in what supplement testing you actually need and the heavy-metals piece above.
3. Is every result under its level? If yes, there is no warning obligation to decide: document the result, keep the lot’s Certificate of Analysis, and you have the data that answers a 60-day notice before it’s ever sent. This is the outcome good incoming-material discipline and finished-batch testing are built to produce.
4. If a result is over a level, the decision moves to your counsel, and it is genuinely a decision, not an automatic warning. The usual options: reformulate or re-source to bring the exposure under the level (a different supplier, a cleaner lot, a lower serving, a different form of an ingredient), or provide a warning. Whether a warning is required, whether an exemption applies, and how to word and place it are legal questions. What Apollo contributes is the front half: the verified numbers, and the ability to re-source or re-formulate toward a cleaner result if you and your counsel choose that path. That testing-and-documentation model is laid out on the quality, testing, and compliance section.

The reason to see it as a testing decision first is leverage. Almost every Prop 65 problem a supplement brand can actually control is controlled upstream: at receiving, where a contaminated lot is caught before it’s committed, and at finished-batch testing, where you learn where you stand before a plaintiff does. By the time the question is purely legal (a result is over a level and shipped), your options are narrower and more expensive. The cheapest place to manage Prop 65 is the same place you manage heavy metals: on the floor, with a number.

What a compliant warning has to contain, and what changed in 2025

If the decision lands on “warn,” the warning itself is not freeform. To earn “safe harbor” (the legal comfort that your warning was clear and reasonable), it has to follow OEHHA’s regulated content. As of mid-2026, a safe-harbor warning’s required components include the warning symbol (a yellow triangle with a black exclamation point), the word “WARNING,” the name of at least one listed chemical, language that the chemical is known to California to cause cancer and/or birth defects or other reproductive harm, and a link to OEHHA’s warnings website, with food and dietary-supplement warnings directing consumers to the food-specific page (www.P65Warnings.ca.gov/food). The exact wording is fixed by regulation; take it from the current OEHHA regulation or your counsel rather than from memory, because it recently changed.

The change is the “short-form” warning, and it matters to anyone using a compact label. For years, brands leaned on a short-form option that could read simply “WARNING: Cancer” or “WARNING: Reproductive Harm” alongside the website, without naming any chemical. That option has been rewritten. On November 26, 2024, California’s Office of Administrative Law approved OEHHA’s amendments to the safe-harbor warning regulations, effective January 1, 2025: amending sections 25601, 25602, 25603, and 25607.2 and adding sections 25607.50 through 25607.53. The core change: a short-form warning must now name at least one chemical for each health endpoint it covers (a chemical for cancer, a chemical for reproductive harm) rather than the bare “Cancer” or “Reproductive Harm,” and OEHHA added new warning-content options alongside it.

OEHHA paired the change with a three-year transition. As of mid-2026, the framework works like this: products manufactured on or after January 1, 2028 that rely on a short-form warning for safe-harbor protection must use the new content, while products manufactured and labeled with the existing short-form warning before that date may continue to be sold through. There is also a 60-day window for retailers to update online short-form warnings after a manufacturer notifies them of a change. What it means going forward is simple to state and easy to underestimate: the era of the anonymous “Cancer / Reproductive Harm” short-form is ending, naming the chemical is becoming the norm, and any brand printing labels now should be designing to the new content so it isn’t re-printing in 2027. All of this is administered by OEHHA and current as of mid-2026; confirm the operative dates and exact wording against OEHHA’s regulation before you print, and route the label decision to your counsel.

Prop 65 on the marketplace: Amazon, DTC, and the warning you can’t fence out

Prop 65 became a near-universal supplement concern, rather than a California-only one, because of ecommerce. Sell on a national marketplace or ship DTC nationwide and you are selling into California; the warning obligation follows the product to the buyer. Marketplaces build this in. Amazon, for instance, provides Prop 65 warning fields in the listing and expects sellers to supply the correct warning where one applies, and a missing or mismatched warning is the kind of gap that can put a listing at risk. The upstream requirement is the same one that governs the rest of a marketplace program: a finished-product Certificate of Analysis you can stand behind, which is why the marketplace and Prop 65 questions collapse into the same document. That channel-specific side is covered in what Amazon’s supplement rules require from your manufacturer. The takeaway: you cannot geo-fence California out of your risk, so decide the warning question at the product level, on data.

Questions that expose a Prop 65 gap

You can learn a lot about whether a manufacturer can support your Prop 65 posture from a short list of questions. Bring these to any shop, Apollo included. Vagueness is its own answer.

• Do you test finished products for lead, cadmium, and inorganic arsenic against Prop 65 safe-harbor levels, or only against USP or a general spec? There is no single “the limit”; the honest answer names Prop 65 specifically when you sell into California.
• Do you test inorganic arsenic by speciation, or report total arsenic? Total arsenic is not the figure the Prop 65 level is written against; “total” is not an answer.
• Will my Certificate of Analysis show a numeric result per metal, with the method and the limit, for the specific lot? A bare “PASS” is not a document you can put in front of a plaintiff or your counsel.
• Do you screen incoming raw materials for heavy metals, or rely on the supplier’s certificate? Reliance is only acceptable if it follows qualification and periodic re-testing; this is where contaminated lots are caught before they’re a warning decision.
• If a result comes in over a level, can you help me re-source or reformulate toward a cleaner lot? This separates a shop that hands you a failing number from one that can help you move it.
• Is contaminant testing quoted as its own line? Testing and the CoA are their own scope; seeing them itemized lets you compare quotes honestly and know exactly what your Prop 65 data is costing.

A manufacturer who answers these plainly, and can show you a real, itemized heavy-metals CoA, is a shop that treats Prop 65 as the managed, data-driven risk it is. One who waves at “we’re compliant” without a number is leaving you to meet a private plaintiff’s lab result with nothing of your own.

About this information

This article is an educational overview for brand owners, Amazon and ecommerce sellers, and founders evaluating how a manufacturer supports a California Proposition 65 posture. It is not legal, regulatory, or medical advice. Laws, regulations, and marketplace policies (including the Proposition 65 list, OEHHA’s safe-harbor levels, the safe-harbor warning content and short-form warning rules, and enforcement procedures) change frequently and vary by jurisdiction and by where and how a product is sold. The figures and rules here are current as of the review date above and were checked against their primary sources (California OEHHA, the California Attorney General’s Proposition 65 pages, and the OEHHA warnings website); they can move, and a value or requirement correct today may not be correct when you read this. In particular, whether a Proposition 65 warning is required for a specific product, whether the naturally-occurring or any other exemption applies, and how to word and place a warning are fact-specific legal determinations. Verify current requirements with qualified counsel or a regulatory professional before acting, and treat everything here as a starting point for that conversation, not a substitute for it. Apollo Future Labs supports manufacturing execution: incoming-material screening, finished-batch contaminant testing coordinated through vetted third-party labs, and the itemized documentation that comes with it. Your counsel decides your compliance strategy, including whether any specific result requires a Proposition 65 warning.