To comply with California's Safe Drinking Water and Toxic Enforcement Act (Proposition 65), companies must conduct a scientific exposure risk assessment for substances listed in the Proposition 65 List that may be present in their products. This provides a clear, step-by-step framework to help companies determine if their products require a "clear and reasonable" warning label. The core of the assessment involves quantifying human exposure doses and comparing them with official safety thresholds. A complete exposure assessment typically follows the steps below, combining model estimation and experimental testing.

Step 1: Identify Substances and Exposure Scenarios

First, confirm whether the product contains any chemicals from the Proposition 65 List. Then, analyze how these chemicals are released from the product and come into contact with humans, constructing an "exposure scenario." Common exposure pathways include:

Oral Ingestion: Such as children licking toys or migration from food contact materials.

Dermal Contact: Such as wearing jewelry, using cosmetics, or touching product surfaces.

Inhalation: Such as inhaling fumes from electronic soldering or volatile organic compounds in vehicles.

Important Notes: When reviewing the Proposition 65 List, pay special attention to:

• The same chemical may have different safety thresholds depending on the type of toxicity (carcinogenic or reproductive) and exposure pathway (e.g., oral, inhalation). For instance, "benzene" and "acrolein" have values listed for both oral and inhalation exposure.
• Some chemicals may not have established safety thresholds (NSRL or MADL listed as blank). For these substances, any quantifiable exposure may trigger a warning obligation, requiring extra caution in assessment.
• For exposures through multiple pathways, consider the total exposure. The list's footnotes provide examples of calculation methods (e.g., benzene's MADL).

Step 2: Data Collection and Assessment Method Selection

This step requires two key types of data: the concentration or release amount of the chemical at the point of contact, and human parameters describing exposure behavior.

Determining Chemical Concentration or Release Amount:

Laboratory Testing: This is the most direct method. Send the product to a qualified laboratory (e.g., ISO/IEC 17025 certified) to analyze substance content using methods like GC-MS, HPLC, or ICP-MS. For migration risks, conduct simulation tests such as wipe tests (simulating skin contact), saliva migration tests (simulating children's licking), or volatile detection.

Using Literature or Default Values: In some cases, refer to published scientific literature or default concentration data provided by regulatory agencies.

Determining Exposure Parameters: Include daily product usage, contact frequency, contact time, skin absorption rate, body weight, etc. These parameters should preferably use data from actual product use scenarios. In the absence of data, refer to authoritative guidelines (e.g., US EPA Exposure Factors Handbook, EU SCCS guidelines) or adopt conservative default values (e.g., using children's body weight, assuming 100% skin absorption, daily contact) to cover the most sensitive populations and worst-case scenarios.

Step 3: Calculate Daily Exposure Dose

Using the relevant mathematical model, combine concentration data with exposure parameters to calculate the estimated daily exposure dose (usually in micrograms/day, µg/day). This dose represents the amount of chemical potentially ingested or absorbed daily through a specific pathway and is the key value for direct comparison with safety thresholds.

A general risk assessment formula is:

Exposure Dose = (Substance Concentration × Contact Frequency × Absorption Rate) / Body Weight

Step 4: Compare with Safety Thresholds and Determine

Compare the calculated daily exposure dose with the "No Significant Risk Level" (NSRL, for carcinogens) or "Maximum Allowable Dose Level" (MADL, for reproductive toxicants) officially published by the California Office of Environmental Health Hazard Assessment (OEHHA).

Safe Harbor: If the exposure dose is ≤ NSRL or MADL, the exposure level is within the "safe harbor," and the company does not need to provide a warning under Proposition 65.

Warning Obligation: If the exposure dose is > NSRL or MADL, it exceeds the safety threshold, and the company must fulfill the warning obligation by providing a "clear and reasonable" warning label on the product.

CIRS Testing is fully equipped with both Exposure Risk Assessment capabilities and testing facilities. Should you require this service, please feel free to contact us at test@cirs-group.com.