Comment - 22030 - Level of Uncertainty

One area where OEHHA could improve the scientific foundation of Proposition 65 is by providing greater clarity and regulatory certainty for chemicals that do not have established MADLs or NSRLs. For many listed chemicals, manufacturers can conduct exposure assessments and demonstrate compliance against established safe harbor levels. However, where no MADL or NSRL exists, it becomes significantly more difficult to demonstrate that a product does not pose a reportable exposure. In these situations, even extensive testing may be unable to definitively disprove a potential exposure because of analytical uncertainty, background contamination, laboratory detection limits, and normal variability in test results. Trace amounts may be detected despite there being little evidence that the product creates a meaningful exposure under intended use conditions. As a result, the absence of a safe harbor level can leave manufacturers with no clear pathway to demonstrate compliance, regardless of the quality or quantity of testing performed. OEHHA should consider developing additional exposure assessment guidance, interim safe harbor values, or testing-based compliance frameworks for chemicals without established MADLs or NSRLs. Greater consideration should also be given to bioavailability, exposure route, and foreseeable use conditions rather than relying solely on the presence of a detectable chemical. Providing a science-based mechanism to evaluate chemicals lacking established safe harbor limits would improve consistency, encourage investment in testing and exposure assessments, and reduce uncertainty for both regulators and manufacturers while maintaining Proposition 65's public health objectives.