Proposition 65 compliance testing is how a business measures whether a product sold in California contains listed chemicals at levels that trigger the state’s warning requirement. The work has three parts: figure out which chemicals could plausibly be in your product, run laboratory analysis to measure them, and convert those measurements into a daily exposure figure that can be compared against California’s safe harbor levels. If the exposure falls below the threshold, no warning is required. If it exceeds the threshold, you either reformulate the product or apply a compliant warning. Testing is also the documentation you rely on if a private enforcer serves a 60-day notice, and those notices arrive by the thousand each year, with penalties reaching $2,500 per day per violation.1Proposition 65 Warnings Website. What Are the Penalties for Violating Proposition 65
The warning obligation applies to any business with 10 or more employees that sells into California, regardless of where the company is based.2OEHHA. Businesses and Proposition 65 Shipping to a California address counts. When OEHHA adds a new chemical to the list, businesses have 12 months to bring products into compliance from the listing date.3OEHHA. Proposition 65 in Plain Language That clock is the practical trigger for retesting an established product.
Which Chemicals to Test For
OEHHA maintains a list of roughly 900 chemicals identified as causing cancer, reproductive harm, or both.4OEHHA. Proposition 65 List No lab screens all 900. The scope is narrowed to substances that are plausible given the product’s materials, which is why the preparation step matters more than the analytical step.
A short list of chemicals turns up over and over in consumer goods enforcement. Lead and cadmium appear in metal alloys, ceramics, and painted surfaces. Phthalates such as DEHP and DBP show up in soft plastics and vinyl. Arsenic and formaldehyde appear in treated wood, adhesives, and finishes. Testing typically targets these first, then expands based on what the product’s raw materials suggest.
Safe Harbor Levels: What You’re Measuring Against
Safe harbor levels are the numerical thresholds that determine whether a warning is required. Exposure below the applicable level exempts the business from the warning requirement.5OEHHA. Proposition 65 No Significant Risk Levels NSRLs and Maximum Allowable Dose Levels MADLs Two categories exist depending on the type of hazard.
For carcinogens, the state sets No Significant Risk Levels. An NSRL is the daily intake expected to produce no more than one additional cancer case per 100,000 people over 70 years of exposure.6New York Codes, Rules and Regulations. 27 CCR 25721 – Level of Exposure to Chemicals Causing Cancer For reproductive toxicants, the state sets Maximum Allowable Dose Levels. An MADL is one-one-thousandth of the exposure level that produced no observable effect in laboratory studies.7New York Codes, Rules and Regulations. 27 CCR 25805 – Specific Regulatory Levels Chemicals Causing Reproductive Toxicity The thousand-fold cushion is deliberate.
OEHHA has published safe harbor levels for about 310 of the roughly 900 listed chemicals.5OEHHA. Proposition 65 No Significant Risk Levels NSRLs and Maximum Allowable Dose Levels MADLs When a chemical has no published NSRL or MADL, the burden shifts entirely to the business to demonstrate that the exposure is safe. That is a much harder position. If your product contains a listed chemical without a published safe harbor level, plan on working with a toxicologist to build a defensible exposure assessment rather than assuming you are in the clear.
Preparing the Product Before It Goes to the Lab
Good testing starts before anything reaches a bench. Pull Safety Data Sheets for every raw material in the product. These give a preliminary picture of what’s inside plastics, paints, alloys, and adhesives, and they let you narrow the testing panel to substances that are actually plausible. Broad-spectrum screening without this step wastes money.
Map the parts of the product a consumer actually touches. A chemical sealed inside a housing poses a different exposure question than one in a surface coating a child might mouth. Contact mapping tells the lab whether to run composite testing on mixed materials or analyze components separately, and that choice feeds directly into the exposure calculation.
Ask upstream suppliers for certificates of compliance. A useful certificate names the manufacturer, identifies the regulations covered (Prop 65 among them), states the basis for the compliance claim, and discloses any substances present above threshold limits together with the exemptions relied on. Certificates do not replace testing, but they help prioritize what to screen first and create a paper trail of good-faith diligence.
Laboratory Methods
When a sample arrives, the lab prepares it physically for analysis. Solids are ground to powder or broken down by acid digestion so the chemicals become accessible to detection equipment. Most labs start with X-ray fluorescence screening. XRF is non-destructive and quickly flags heavy metals such as lead or cadmium in surface coatings. Elevated XRF readings send the sample to more precise instruments.
Inductively Coupled Plasma Mass Spectrometry (ICP-MS) measures trace metals down to parts per billion. That sensitivity is necessary because many safe harbor levels sit at single-digit micrograms per day. For organic compounds such as phthalates and formaldehyde, labs use Gas Chromatography-Mass Spectrometry (GC-MS), which vaporizes the sample, separates the compounds through a column, and identifies each against a library of known standards.
Combined lead and phthalate screening for a single product typically runs a few hundred dollars per sample. Costs rise quickly with additional components or a wider chemical panel. Requesting only the tests relevant to your materials keeps the bill manageable.
Turning Lab Results Into a Compliance Decision
Raw results usually come back in parts per million. That figure alone does not answer the compliance question. Safe harbor levels are expressed as daily intake in micrograms per day, so the concentration has to be converted into a daily exposure estimate.
The conversion depends on assumptions about how a consumer actually uses the product: how often they handle it, how long skin contact lasts, whether hand-to-mouth transfer is realistic. Children’s products draw especially conservative assumptions. OEHHA publishes default transfer factors for some exposure pathways, but contact frequency and duration have to be justified case by case for the specific product.8OEHHA. Interpretive Guideline for Hand-to-Mouth Transfer of Lead through Exposure to Consumer Products The exposure step is where the analysis becomes judgment work rather than pure measurement.
Compare the resulting daily exposure directly against the applicable NSRL or MADL.9Proposition 65 Warnings Website. What Are Safe Harbor Numbers Below the threshold, no warning is required. Above it, the business must either apply a compliant warning or reformulate. Document every step. A defensible file shows a clean line from lab data through exposure assumptions to the regulatory comparison, and that record is your primary defense if the product is ever challenged.
What to Do When a Product Exceeds the Threshold
Exceeding a safe harbor level does not force you to add a warning. The two real choices are reformulating to bring the chemical level down or labeling with a compliant warning.
Most manufacturers prefer reformulation. A Prop 65 warning on retail packaging can suppress sales because many buyers read it as a signal that the product is dangerous, even when the actual exposure is low. Common paths include switching to alternative pigments, sourcing cleaner raw materials, or adjusting manufacturing to eliminate the listed chemical. Some companies set internal targets below the safe harbor level to leave themselves margin. Reformulation costs vary, but for many products it is cheaper over time than defending a warning-based strategy against private enforcement.
If reformulation is not feasible, the warning must meet California’s content and formatting rules for safe harbor protection, and the compliance decision should be documented alongside the testing file. Courts assessing a Prop 65 dispute weigh whether the business took good-faith measures to comply and when those measures were taken.10California Legislative Information. California Health and Safety Code HSC 25249.7
How Testing Documentation Holds Up Against a 60-Day Notice
Prop 65 is enforced almost entirely through civil suits, and the majority are brought by private individuals and advocacy groups acting “in the public interest.” Before filing, a private enforcer must serve a 60-day notice on the alleged violator, the Attorney General, and the local prosecutor.10California Legislative Information. California Health and Safety Code HSC 25249.7 For failure-to-warn claims, the notice must include a certificate of merit stating that someone with relevant expertise has reviewed exposure data and believes the claim has merit.
The 60-day window is a working period, not a waiting period. Businesses that already hold current test results and a documented exposure analysis can often resolve a notice on the strength of that file. Businesses without testing scramble to commission it under time pressure and negotiate from a weaker position. Reformulating or applying a compliant warning during the notice period demonstrates good faith and can reduce any penalty. The statute directs courts to weigh the nature and severity of the violation, the economic impact of the penalty, the good-faith compliance measures taken, and the willfulness of the conduct when setting the amount.10California Legislative Information. California Health and Safety Code HSC 25249.7 Testing done before a notice arrives is the strongest evidence of every one of those factors.