Heavy Metal Testing and Proposition 65 Compliance: What Brand Owners Should Know
July 2, 2025
For dietary supplement and food product manufacturers, regulatory compliance is more than just an obligation—it’s a critical factor in brand reputation and consumer trust. One of the most stringent regulations that brand owners must navigate is Proposition 65 (Prop 65) in California, which mandates warnings for products containing specific chemicals, including heavy metals. This blog outlines the essentials of heavy metal testing and how brands can effectively comply with Prop 65 to avoid legal risks and maintain quality assurance.
Understanding Heavy Metal Contamination Risks
Heavy metals such as lead, arsenic, cadmium, and mercury occur naturally in the environment and can unintentionally end up in dietary supplements and food products through soil contamination, water sources, or ingredient processing. While trace levels of heavy metals may be unavoidable, excessive exposure can be toxic and harmful to consumers.
Common Sources of Heavy Metal Contamination in Supplements
Botanical Ingredients – Herbs and plant-based materials may absorb heavy metals from the soil.
Mineral-Based Supplements – Ingredients like calcium or magnesium sourced from natural deposits can contain trace heavy metals.
Water-Soluble Components – Water contamination can introduce metals during production.
Manufacturing Equipment – Poor facility controls may contribute to product contamination.
To ensure product safety and compliance, manufacturers must adopt robust testing protocols that identify and mitigate the presence of these contaminants.
Proposition 65: What Brand Owners Need to Know
California’s Proposition 65, officially known as the Safe Drinking Water and Toxic Enforcement Act of 1986, requires businesses to provide clear warnings if their products contain chemicals known to cause cancer or reproductive harm. This includes specific limits on lead, cadmium, and arsenic in food and dietary supplements.
Key Compliance Considerations
Understanding Safe Harbor Limits
California establishes safe harbor exposure levels for certain chemicals. If levels exceed these limits, a Prop 65 warning is required.
Example: The safe harbor limit for lead is 0.5 micrograms per day for reproductive harm and 15 micrograms per day for cancer risk.
Regular Heavy Metal Testing
To determine compliance, brands should conduct routine analytical testing using methods like Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to quantify heavy metal concentrations.
Third-party labs specializing in Prop 65 compliance can help ensure accurate assessments.
Labeling and Consumer Warnings
If a product exceeds Prop 65 limits, businesses must include a clear warning statement on packaging and marketing materials.
Example of a compliant warning: “WARNING: This product contains lead, a chemical known to the State of California to cause reproductive harm.”
Defending Against Legal Challenges
Prop 65 is highly litigated, with frequent lawsuits filed by private parties and consumer advocacy groups.
Maintaining batch records, lab testing reports, and supplier documentation strengthens legal defenses.
Consider enrolling in industry organizations that provide guidance on regulatory challenges.
Best Practices for Managing Compliance
1. Work with Certified Laboratories
Partner with labs that use validated testing methods such as ICP-MS or Atomic Absorption Spectroscopy (AAS) to detect heavy metals with high accuracy.
2. Source Ingredients from Reputable Suppliers
Establish strict supplier qualification programs to ensure raw materials meet quality and safety specifications before entering the production process.
3. Implement Risk-Based Quality Control Systems
Conduct routine environmental monitoring and apply Hazard Analysis and Critical Control Points (HACCP) principles to proactively reduce contamination risks.
4. Stay Informed on Regulatory Updates
Prop 65 limits evolve, and new chemicals may be added to the regulation. Subscribe to California Office of Environmental Health Hazard Assessment (OEHHA) updates and join compliance forums to stay ahead.
Final Thoughts
For brand owners in the supplement and food industries, heavy metal testing and Proposition 65 compliance are essential components of regulatory responsibility. By investing in rigorous testing protocols, proactive supplier management, and transparent labeling, companies can safeguard their brand reputation and minimize legal exposure.
Navigating Prop 65 can be challenging, but with proper quality controls and risk assessment strategies, manufacturers can successfully meet compliance requirements while maintaining consumer trust.