Introduction
For companies selling consumer products in California, Proposition 65 often raises a deceptively simple question: Does this product need a warning? The answer is not determined simply by finding a Proposition 65-listed chemical somewhere in the formulation or product. The actual assessment depends on the chemical, the expected consumer exposure, the applicable safe harbor level where one exists, and the circumstances of product use.
The warning requirements have also evolved. OEHHA's latest amendments to the Proposition 65 warning regulations became effective January 1, 2025, including changes intended to make certain short-form warnings more informative and to clarify warning requirements for products sold online and through catalogs.
For manufacturers, brand owners, importers, and retailers, this makes it important to look beyond a simple ingredient-list screening and evaluate the current warning requirements together with the underlying exposure and toxicology.
What Is California Proposition 65?
California Proposition 65, formally known as the Safe Drinking Water and Toxic Enforcement Act of 1986, that requires businesses to provide a clear and reasonable warning before knowingly and intentionally exposing individuals in California to a chemical the state has identified as causing cancer, birth defects, or other reproductive harm. The regulation is administered by the California Office of Environmental Health Hazard Assessment (OEHHA), which maintains and periodically updates the Proposition 65 list of chemicals based on available scientific evidence.
An important point for consumer product companies is that Proposition 65 does not ban products containing listed chemicals. The presence of a listed chemical does not automatically mean that a warning is required.
What Determines Whether a Prop 65 Warning Is Required?
A practical Prop 65 assessment generally brings together four questions:
Is a Proposition 65-listed chemical present or potentially present?
Can consumers be exposed to that chemical under normal or reasonably foreseeable use?
What is the expected level and route of exposure?
Does the exposure fall within an applicable safe harbor level or otherwise qualify for an exemption?
Exposure may occur through different routes depending on the product, including ingestion, inhalation, or dermal contact. This is why two products containing the same listed chemical may not necessarily reach the same conclusion. Their formulations, concentrations, use patterns, exposure routes, and expected consumer exposure can be very different.
A chemical screening is therefore a useful starting point, but it is not always sufficient to support the final warning decision.
What Are Prop 65 Safe Harbor Levels?
A safe harbor level is a regulatory reference point that helps businesses assess whether an exposure to a specific listed chemical is significant enough to require a warning. Two types exist, and they apply to different categories of listed chemicals:
No Significant Risk Level (NSRL)
The No Significant Risk Level (NSRL) applies to chemicals listed as carcinogens.
Where consumer exposure remains below the applicable NSRL, a Proposition 65 warning is generally not required.
Maximum Allowable Dose Level (MADL)
The Maximum Allowable Dose Level (MADL) applies to chemicals listed for reproductive toxicity, including birth defects and other reproductive harm.
Where consumer exposure remains below the applicable MADL, a Proposition 65 warning is generally not required.
A safe harbor level is not available for every chemical on the Proposition 65 list. Where one does not exist, a company may still need to evaluate the anticipated exposure and determine whether it can demonstrate that the exposure does not present a significant risk under the applicable Proposition 65 framework. OEHHA provides regulatory approaches for making such determinations.
How Do Companies Determine If a Product Needs a Prop 65 Warning?
A practical assessment can follow a structured sequence:
1. Review the product composition
Evaluate the finished product, ingredients, raw materials, components, and, where relevant, packaging materials.
2. Identify potentially relevant listed chemicals
Compare the available chemical information against the current Proposition 65 list and investigate potential impurities or contaminants where appropriate.
3. Define realistic exposure scenarios
Consider how the consumer uses the product, how often it is used, how much is used, and which exposure routes are relevant.
4. Estimate exposure
Where appropriate, estimate consumer exposure based on product composition and realistic use conditions.
5. Compare with applicable safe harbor levels
If an NSRL or MADL is available, compare the estimated exposure with the applicable value.
6. Evaluate the scientific evidence
Where the situation is more complex, toxicological literature, analytical data, exposure information, and other scientific evidence may be needed to support the conclusion.
7. Document the decision
The final conclusion should have a clear scientific and regulatory rationale that can be revisited if the formulation, supplier, use pattern, or regulatory requirements change.
This approach is generally more reliable than applying a warning automatically to every product containing a listed chemical or assuming that no warning is needed simply because the chemical is present only at a low concentration.
What Information Must Be Included on a Prop 65 Warning Label?
When a warning is required, the applicable warning provisions determine the required content and presentation.
Depending on the product and warning method, considerations may include:
Required warning language
The appropriate signal word
The warning symbol
Identification of the relevant chemical
Placement and prominence
Product-specific warning provisions
Requirements for products sold through websites or catalogs
Prop 65 Risk Assessment and Toxicology Evaluation
Prop 65 compliance is a regulatory exercise, but scientific evaluation can be an important part of the decision-making process. It starts with hazard identification, understanding what a given chemical is capable of causing based on available toxicity information. From there, exposure assessment estimates dose, route of exposure, and realistic consumer use patterns, including duration and frequency of use and relevant population considerations.
This is particularly relevant when dealing with trace contaminants, impurities, complex formulations, multiple exposure routes, or chemicals for which an applicable safe harbor level has not been established. A chemical can appear on the list and still not require a warning for a specific product, if the realistic exposure falls below the level regulators consider significant.
Common Prop 65 Compliance Mistakes
Some common compliance problems are relatively straightforward to avoid:
Assuming that every listed chemical automatically requires a warning
Assuming that a low concentration alone means no warning is required
Using outdated warning language or formats
Failing to consider online sales requirements
Looking only at intentional ingredients and overlooking impurities or components
Failing to evaluate relevant exposure routes
Relying solely on supplier information without understanding its limitations
Not reassessing a product after formulation or supplier changes
Treating Prop 65 compliance as equivalent to FDA or other federal compliance
Applying the same warning strategy across products without considering product-specific exposure
Another important misconception is that a Prop 65 warning means a product is banned or prohibited from sale. Proposition 65 is a warning law; a warning requirement and a product prohibition are not the same thing.
Prop 65 Warning Labels vs. Other Product Safety Regulations
Proposition 65 operates independently from other regulatory frameworks that may also apply to a given product. Proposition 65 should be evaluated alongside, not instead of, other product safety and regulatory requirements. FDA, U.S. Consumer Product Safety Commission (CPSC), and other federal or state frameworks may address product safety, ingredients, labeling, or chemical restrictions from different perspectives.
A product that complies with applicable FDA or CPSC requirements is not automatically compliant with Proposition 65, and a Prop 65 warning does not replace other required safety or labeling measures (when applicable).
How Can SciQra Support for Prop 65 Compliance?
SciQra supports companies in evaluating Prop 65 requirements using a combination of chemical screening, exposure assessment, toxicological evaluation, scientific literature review, and regulatory analysis.
Depending on the product and available information, our support may include:
Screening ingredients, raw materials, components, and relevant impurities against the Proposition 65 list
Reviewing potential consumer exposure through relevant routes such as ingestion, inhalation, and dermal contact
Evaluating applicable safe harbor levels, where established
Reviewing toxicological and scientific evidence where further assessment is needed
Supporting targeted testing strategies when existing information is insufficient
Reviewing the scientific basis for a Prop 65 warning decision
Supporting documentation of the assessment and regulatory rationale
The objective is not to recommend a warning simply because a listed chemical is identified, but to help companies make a scientifically supported and appropriately documented compliance decision.
Conclusion
Prop 65 compliance is fundamentally an exposure-based regulatory assessment, not simply an exercise in checking whether a listed chemical appears in a product. The relevant conclusion depends on the chemical, the expected consumer exposure, applicable safe harbor provisions or other regulatory considerations, and the quality of the scientific information supporting the assessment.
For companies selling consumer products in California, evaluating these factors before market entry can provide a clearer basis for determining whether a warning is appropriate and what supporting documentation may be needed.
SciQra helps companies evaluate Prop 65 requirements through a combination of toxicology, exposure assessment, scientific review, and regulatory expertise, supporting informed compliance decisions rather than blanket assumptions
Frequently Asked Questions
When is a Prop 65 warning label required?
A Proposition 65 warning is generally required when a business knowingly and intentionally exposes individuals to a listed chemical, unless an applicable exemption or an exception based on sufficiently low exposure applies. Where an OEHHA safe harbor level has been established, exposure at or below that level provides a safe harbor from the warning requirement.
Does every product containing a Prop 65-listed chemical require a warning?
No. The presence of a listed chemical alone does not automatically mean that a warning is required. The assessment depends on the anticipated exposure, applicable safe harbor provisions, exemptions, and the available scientific information. Where no safe harbor level exists, a business may need to demonstrate that the anticipated exposure does not present the level of risk covered by the Proposition 65 warning requirement.
What information is needed to determine whether a Prop 65 warning is required?
The assessment may involve the product formulation, chemical and raw material information, potential impurities or contaminants, intended use, consumer exposure routes, use frequency and duration, analytical data where relevant, and applicable toxicological information. Where an OEHHA safe harbor level exists, estimated exposure can be compared with the applicable NSRL or MADL.
How can companies avoid Prop 65 compliance problems?
Companies can reduce compliance risk by evaluating products before market entry, reviewing ingredients and components against the current Proposition 65 list, assessing reasonably anticipated consumer exposure, reviewing applicable safe harbor levels, and maintaining documentation supporting the compliance decision. Companies should also monitor relevant regulatory changes and reassess their conclusions when formulations, suppliers, packaging, or use conditions change.
Does compliance with FDA requirements mean a product is compliant with Proposition 65?
No. Proposition 65 is a separate California requirement, so compliance with applicable FDA requirements does not automatically establish Proposition 65 compliance. However, Proposition 65 includes specific provisions addressing certain federally regulated products and warnings, which may affect whether a separate Prop 65 warning is required in particular circumstances. Companies should therefore evaluate the applicable federal and California requirements together rather than assume that one automatically replaces the other.