What Is the Prop 65 Naturally Occurring Chemical Exemption?

The Prop 65 naturally occurring chemical exemption lets a California food business skip the standard Proposition 65 warning when a listed chemical is in the food solely because of the natural environment where it was grown or raised. The rule sits in Title 27, Section 25501 of the California Code of Regulations, and it only applies if the business can prove three things: the chemical is genuinely natural, no human activity added to the amount present, and the business has reduced the contamination to the lowest level current technology allows.¹ Fail on any one of those and the exemption disappears, leaving the business exposed to civil penalties of up to $2,500 per violation per day.²

What the Exemption Covers

Proposition 65 requires businesses to warn Californians before knowingly exposing them to chemicals the state has identified as causing cancer or reproductive harm.³ The naturally occurring exemption carves out a narrow exception for food. If a listed chemical appears in food entirely because of natural geological or biological processes, consuming that food does not count as an “exposure” under the statute, and no warning is required.¹

The exemption is built around food, but Section 25501(b) extends it one step further. If a non-food consumer product contains a listed chemical only because it was manufactured using a food ingredient that carried the chemical naturally, the producer can claim the exemption for that portion. A skincare product made with cocoa butter, for example, can rely on the exemption for naturally occurring lead that came from the cocoa butter itself. Any additional contamination introduced during manufacturing falls outside the protection.¹

The same splitting logic applies when a food contains a chemical from mixed sources. The exemption shields only the natural portion, and the business still faces exposure liability for the human-caused share.¹

What “Naturally Occurring” Actually Means

Section 25501(a)(1) defines a chemical as naturally occurring if it is either a natural part of a food’s own composition or present solely because the food absorbed it from the environment where it was grown or raised. Minerals in volcanic soil pulled up by a crop’s root system qualify. So do toxins produced by natural fungal growth. The operative word is “solely.” If any portion of the chemical came from somewhere other than the food’s natural environment, that portion is not covered.¹

When Human Activity Disqualifies the Exemption

Section 25501(a)(3) is explicit: a chemical is naturally occurring only to the extent it did not result from any known human activity. Industrial runoff, pesticide residue, and chemical additives in irrigation water all push a substance out of the exemption. Cadmium absorbed by crops grown on soil contaminated by nearby factory emissions is not “naturally occurring,” even though the plants took it up through ordinary biology.¹

The regulation deliberately excludes basic farming from the definition of disqualifying “human activity.” Sowing seeds, planting, irrigating with clean water, and mechanical soil preparation do not count. Adding chemicals to irrigation water does. A grower drawing from a natural aquifer with trace arsenic stays within the exemption; a grower treating irrigation water with an additive that introduces a listed chemical does not.¹

Processing and packaging get the same scrutiny. Contaminated equipment, blended-in ingredients that carry listed chemicals, and storage containers that leach lead all introduce human-caused contamination. A raw crop that qualifies at harvest can lose protection at any step downstream.

The Lowest Feasible Level Requirement

Proving a chemical is natural is only half the test. Section 25501(a)(4) adds a second obligation: anyone in the supply chain, from producer to distributor, must use quality control measures that reduce natural contaminants to the “lowest level currently feasible.”¹ The regulation borrows that standard from federal FDA rules under 21 CFR 110.110(c), which require food handlers to push unavoidable defects as low as technology allows.⁴

In practice, this means following good agricultural practices in the field and good manufacturing practices in the facility. If a commercially available filtration system can meaningfully reduce lead in processing water, you need to be using it. If one sourcing region consistently produces lower arsenic levels than another, regulators and plaintiffs will ask why you chose the higher-arsenic source. The standard is not perfection. It is what current technology and reasonable economics make possible. “We didn’t know about it” fails as a defense once the rest of the industry has adopted the mitigation.

This is where most exemption claims break down in litigation. A company proves the chemical is genuinely natural, documents the soil and water conditions, and then gets challenged on whether it did everything feasible to reduce the levels.

Pre-Set Benchmarks for Specific Foods

For a handful of products, regulators or private settlements have established numbers that function as presumed naturally occurring levels, giving businesses a reference point instead of forcing each one to prove the baseline from scratch.

Inorganic Arsenic in Rice

In 2018, the state set default natural background levels for inorganic arsenic in rice under Section 25501.1: 80 parts per billion for white rice and 170 parts per billion for brown rice.⁵ These figures account for some contribution from human sources when setting the baseline.⁶

Lead in Cocoa Ingredients

No regulation sets default lead levels for chocolate, but a consent judgment in As You Sow v. Guittard Chocolate Company established figures the parties agreed to treat as naturally occurring for settlement purposes: 0.500 μg of lead per gram of cocoa powder, 0.200 μg per gram of cocoa liquor, and 0.100 μg per gram of cocoa butter.⁷ The parties stated these are not official safe harbor levels, but the figures have shaped how later chocolate cases get negotiated.

How a Business Claims the Exemption

There is no application to file and no state agency that pre-approves anything. The business makes its own determination that the chemical qualifies, leaves the warning off the label, and keeps the evidence ready for the challenge that may come. The California Attorney General’s office has described the process as one where the business itself “proves” the chemical is naturally occurring and has been reduced to the lowest feasible level.⁸

The exemption is an affirmative defense, which means the burden of proof sits with the business at every stage.⁹ A defensible evidence package generally includes:

Laboratory analysis of raw ingredients before any handling, establishing baseline chemical levels in the food as harvested or obtained
Geological and soil surveys of the specific growing region, ideally covering multiple seasons to account for variability
Water quality reports confirming that irrigation sources and processing water are not introducing contamination beyond natural background
Land use history for the production site showing no industrial activity, chemical spills, or contamination events that could elevate levels above natural baselines
Manufacturing process documentation showing that equipment, storage, and processing additives are not adding listed chemicals, plus records of the quality control measures used to reduce contaminants to the lowest feasible level

Lab testing should come from an accredited facility. ISO 17025 accreditation and National Environmental Laboratory Accreditation Program (NELAP) certification are the most widely recognized standards for this type of analytical work, and results from unaccredited labs face serious credibility challenges in litigation.

Documentation also needs refreshing. A soil survey from five years ago says little about what this season’s crop absorbed, and a water quality report from a prior irrigation cycle may not reflect current conditions. Treating the evidence package as a one-time exercise is how businesses discover the gap at the worst possible moment.

What Happens When the Exemption Gets Challenged

Most Proposition 65 enforcement comes from private plaintiffs. Before suing, a plaintiff must serve a 60-day notice of violation on the business, the Attorney General, and any relevant district attorney or city attorney. The notice has to include a Certificate of Merit in which the plaintiff’s attorney states they have consulted with someone with relevant expertise, reviewed the facts and data on the alleged exposure, and concluded there is a credible basis for the claim.¹⁰

The 60-day window is the only breathing room a business gets. Companies without a pre-existing evidence package rarely assemble a credible one in that time, which is why most defendants without strong documentation end up settling. Settlement agreements typically include injunctive relief requiring compliant warnings going forward, civil penalties, and reimbursement of the plaintiff’s attorney fees and investigation costs. If a case does go to judgment, penalties can reach $2,500 per day for each violation, with courts weighing the severity of the violation, the economic impact on the business, good-faith compliance efforts, and the deterrent effect of the penalty.²

One parallel pathway worth knowing about: Proposition 65 also provides safe harbor thresholds for each listed chemical, called No Significant Risk Levels for carcinogens and Maximum Allowable Dose Levels for reproductive toxicants. If daily exposure falls below those thresholds, no warning is required at all, regardless of whether the chemical is natural.⁹ For some chemicals those limits are extremely low, which is exactly why the naturally occurring exemption is the pathway food producers reach for when safe harbor is out of reach.¹¹

1
Legal Information Institute. California Code of Regulations Title 27 25501 – Exposure to a Naturally Occurring Chemical in a Food
2
California Legislative Information. California Health and Safety Code 25249.7
3
California Legislative Information. California Health and Safety Code 25249-6
4
eCFR. 21 CFR 110.110 – Natural or Unavoidable Defects in Food for Human Use That Present No Health Hazard
5
Legal Information Institute. California Code of Regulations Title 27 25501.1
6
Office of Environmental Health Hazard Assessment. New Section 25501.1 Naturally Occurring Concentrations of Listed Chemicals in Unprocessed Foods – Inorganic Arsenic in White and Brown Rice
7
State of California – Department of Justice – Office of the Attorney General. Stipulated Consent Judgment – As You Sow v. Guittard Chocolate Company
8
State of California – Department of Justice – Office of the Attorney General. Frequently Asked Questions – View All
9
California Legislative Information. California Health and Safety Code 25249-10
10
State of California – Department of Justice – Office of the Attorney General. Regulations
11
Office of Environmental Health Hazard Assessment. Proposition 65 No Significant Risk Levels NSRLs and Maximum Allowable Dose Levels MADLs