This section explains how to choose which HQs and CRs to base public health decisions on, and how to decide whether site-specific scenarios need further evaluation in the next scientific component of the PHA process: the In-Depth Toxicological Effects Analysis.
When evaluating your sites, you may have HQs and CRs based on site-specific, CTE, and/or RME doses. How do you know which values to use to make public health decisions?
- In most cases, use the RME values to make public health decisions.
- If you have information that indicates average intakes are most appropriate, use the CTE values to determine whether people with typical intakes are at risk, but explain why the RME values were not used in your evaluation.
- If you have a site-specific scenario, use these results, as long as you can justify the inputs.
- It is important to remember that when using CTE and site-specific scenarios, the concern for RME exposure could still exist. For instance, if the exposed population changed over time and the future population had higher than average exposures, you would also want to evaluate the future RME exposure scenario.
- Contact the ADS group if you need assistance with identifying the most appropriate values to use for making public health decisions in your documents.
Based on the EPC and exposure calculations, you will perform the next component of the scientific evaluation, the in-depth toxicological effects analysis, if any of the following conditions are met for your site-specific scenarios:
- A hazard quotient exceeds 1.
- A cancer risk exceeds 1E-06.
- No health guideline is available to evaluate non-cancer health effects for a contaminant.
- No cancer risk value is available to evaluate cancer risk for a known or suspected carcinogen.
- A contaminant is of community concern.
- Another factor (specific populations, multiple pathways of exposure, multiple contaminant exposures) warrants further evaluation (even if no HQs or CRs are above acceptable levels).
A summary of the EPC and exposure calculation process should be included in your documents.