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California Proposition 65, commonly referred to as Prop 65, is one of the most visible chemical disclosure laws in the United States. For companies selling products into California, Prop 65 compliance directly affects labeling, ecommerce listings, and supplier data management.
As chemical listings expand and enforcement remains active, understanding California Prop 65 requirements is critical. We'll cover the Prop 65 chemical list, Prop 65 safe harbor levels, Prop 65 labeling requirements, and core compliance steps, as well as how Source Intelligence helps teams manage risk with confidence.
What is California Prop 65?
California Prop 65, formally known as the Safe Drinking Water and Toxic Enforcement Act, is a right-to-know law requiring businesses to provide clear warnings when products expose consumers to certain chemicals. Those chemicals are published on the official Prop 65 list and are known to the State of California to cause cancer, birth defects, or other reproductive harm.
A key distinction in understanding Prop 65 is that the law focuses on exposure, not simply the presence of a chemical. A product may contain a listed substance, but a warning is only required if consumer exposure exceeds defined thresholds.
Who must comply with Prop 65?
Prop 65 compliance applies broadly across the supply chain and is not limited to companies headquartered in California. Any business selling products into the state may be subject to Prop 65 compliance requirements.
Covered entities include:
- Manufacturers
- Importers
- Distributors
- Retailers
- Online sellers and marketplaces
The law generally applies to businesses with 10 or more employees, but smaller organizations are often impacted through contractual or customer requirements.
Prop 65 chemical list & recent updates
Monitoring updates to the Prop 65 chemical list is one of the most resource-intensive aspects of Prop 65 compliance. New chemical listings can create future warning obligations, even for long-established products.
Overview of the Prop 65 chemical list
The California Prop 65 list includes hundreds of chemicals identified as causing cancer, reproductive harm, or both. To support implementation, the state maintains the California Prop 65 list, also referred to as the Prop 65 list, through the Office of Environmental Health Hazard Assessment (OEHHA). The Prop 65 list is updated regularly as new scientific evidence becomes available.
For businesses, this means compliance is not static. Substances previously unregulated may later appear on the Prop 65 chemical list, requiring reassessment of materials, components, and finished goods. Proactive tracking is essential to avoid missed deadlines and enforcement risk.
New Prop 65 chemical listing: N-methyl-N-formylhydrazine
Addition of N-methyl-N-formylhydrazine to the Prop 65 list for cancer
The OEHHA has added N-methyl-N-formylhydrazine to California’s Proposition 65 list of chemicals known to cause cancer, effective December 8, 2025.
The listing was made through California’s “Qualified Experts” process following a determination by OEHHA’s Carcinogen Identification Committee (CIC). At the public meeting on November 18, 2025, the CIC reviewed OEHHA staff’s findings and public comments, ultimately voting 8–1 to list the chemical as a carcinogen.
Warnings for significant consumer exposures will be required starting December 8, 2026. This one-year window provides businesses time to evaluate whether the chemical is present in their products, assess potential exposure, and update Prop 65 compliance and labeling programs as needed.
Prop 65 warning & labeling requirements
Prop 65 compliance requires businesses to provide a clear and reasonable Prop 65 warning before knowingly or intentionally exposing individuals to any listed chemicals. For most consumer products, this obligation is met through product labeling.
Warnings may also be required in other contexts, such as workplace signage or posted notices, depending on the mode of exposure.
When Prop 65 warnings are required
A Prop 65 warning is generally required when exposure to a listed chemical exceeds Prop 65 safe harbor levels, including No Significant Risk Levels (NSRLs) for cancer and Maximum Allowable Dose Levels (MADLs) for reproductive harm.
Exposure assessments consider how a product is used, how often exposure occurs, and for how long, using safe harbor levels as the compliance benchmark.
Required elements of a Prop 65 warning label
Prop 65 warning labels for consumer products must meet specific content and formatting requirements. At a high level, labels must include:
- The name of at least one listed chemical
- A yellow triangular warning symbol with a black exclamation point
- The word WARNING in bold, capital letters
- A statement regarding cancer and/or reproductive harm
- A reference to OEHHA’s official Proposition 65 website
The warning text must also be clearly visible and comparable in size to other consumer information on the package.
Short-form vs. long-form Prop 65 warnings
The OEHHA allows both long-form and short-form Prop 65 warning formats. Long-form warnings provide more chemical detail, while short-form warnings are often used when packaging space is limited.
Businesses must confirm which warning format is appropriate for each product. Misapplication of short-form warnings can increase Prop 65 compliance risk.
Where Prop 65 warnings must appear
California Prop 65 warning placement extends beyond product labels and packaging to also include:
- E-commerce product pages and online listings
- Printed catalogs
- On-site signage where applicable
Alignment across physical and digital channels is essential.
Prop 65 compliance checklist
Prop 65 compliance is ongoing work, not a one-time exercise. As product portfolios expand and suppliers change, teams need a repeatable way to manage obligations without restarting the analysis each time something shifts.
The steps below reflect how many manufacturers, importers, and brand owners organize Prop 65 work across products and sales channels:
- Identify chemicals in materials, components, and finished products.
- Screen substances against the Prop 65 chemical list, including new additions.
- Evaluate exposure scenarios against Prop 65 safe harbor levels.
- Align packaging, labels, and e-commerce listings with Prop 65 warning requirements.
- Maintain supplier documentation and internal compliance records.
- Monitor California Prop 65 list updates and effective dates.
A defined process helps teams move faster, reduces guesswork, and supports consistent decision-making as requirements evolve.
Common Prop 65 compliance challenges
Even with clear regulatory requirements, Prop 65 compliance is difficult to manage at scale. Many organizations rely on fragmented data, manual tracking, and supplier follow-ups that are hard to sustain over time.
Common compliance challenges include:
- Limited visibility into chemical content across global supply chains.
- Incomplete or inconsistent supplier disclosures.
- Difficulty tracking changes to the Prop 65 list.
- Interpreting Prop 65 safe harbor levels accurately.
- Synchronizing physical labels with online Prop 65 warning content.
- Documenting decisions for audits or enforcement actions.
When these challenges persist, compliance becomes reactive, rather than proactive. This increases regulatory risk and places unnecessary strain on internal teams, driving many companies to look for more centralized, automated ways to manage Prop 65 obligations.
How Source Intelligence supports Prop 65 compliance
Prop 65 requirements change fast, and manual tracking doesn’t scale. Without a centralized system, teams struggle to keep chemical data current, trigger the right warnings, and respond quickly to audits or enforcement actions.
Source Intelligence simplifies Prop 65 compliance by bringing regulatory intelligence, supplier data, and documentation into one connected workflow. Built for day-to-day compliance decisions, our Prop 65 solution helps teams:
- Identify regulated chemicals faster by screening materials and products against the Prop 65 chemical list.
- Collect and validate supplier data efficiently using structured, automated outreach.
- Stay ahead of regulatory changes with continuous monitoring of Prop 65 list updates and effective dates.
- Support labeling and warning decisions with centralized records and audit-ready documentation.
The result is lower regulatory risk, less time spent chasing documentation, and stronger continuity across compliance programs. Teams can also align Prop 65 efforts with broader TSCA and REACH workflows to reduce duplication. Explore our Prop 65 solution to see how it works.
Prop 65 compliance FAQs
California Prop 65 is a state right-to-know law that requires businesses to provide clear warnings when products or environments expose people to listed chemicals linked to cancer or reproductive harm.
What is a Prop 65 warning label?
A Prop 65 warning label is a consumer-facing notice that informs individuals about potential exposure to one or more chemicals on the California Prop 65 chemical list. These warnings typically appear on product packaging, online product pages, or posted signage, and must meet specific content and formatting requirements set by the state.
When is a Prop 65 warning required?
A Prop 65 warning is required when exposure to a listed chemical exceeds established safe harbor levels set by California’s Office of Environmental Health Hazard Assessment (OEHHA). Determining whether a warning is required depends on how a product is used and the level of exposure that may occur over time.
What is the California Prop 65 chemical list?
The California Prop 65 chemical list is a regularly updated inventory of substances identified by the state as causing cancer, birth defects, or other reproductive harm. The OEHHA updates the list based on scientific review, authoritative sources, and state evaluation processes.
What are Prop 65 Safe Harbor Levels?
Prop 65 Safe Harbor Levels are exposure thresholds that help determine whether a warning is required. These levels include No Significant Risk Levels (NSRLs) for cancer-causing chemicals and Maximum Allowable Dose Levels (MADLs) for chemicals linked to reproductive harm.
Does a Prop 65 warning mean a product is unsafe?
No. A Prop 65 warning does not mean a product is unsafe or illegal to sell. It indicates that the product may expose users to a listed chemical at a level that requires disclosure under California law.