Other Factors to Consider
This section explains the other factors health assessors need to consider during the EPC and exposure calculation process before excluding a contaminant from further evaluation.
Before excluding a contaminant from further evaluation, be sure to consider these other factors:
- Community concerns. As mentioned throughout this e-manual, community concerns are important to the PHA process. Therefore, when a community has expressed special concern about a particular contaminant or exposure, whether or not HQs exceed 1 or cancer risks exceed 1.0E-6, you should include this contaminant for evaluation and discussion.
- Specific populations. Although health guidelines and cancer risk values are designed to be protective for most of the population, including sensitive populations and children, they might not apply to all populations of potential interest. For example, subsistence fishers may be exposed at a higher rate than the general population, or people in extremely warm climates may ingest extremely high quantities of water. Account for these factors when estimating site-specific doses. In addition, some people, such as asthmatics or the elderly, might be more sensitive to the effects of a contaminant. When you have special populations, be sure to complete a site-specific scenario in PHAST. In addition, consult with an ATSDR toxicologist to determine whether any of the contaminants detected at your site warrant special attention in light of site exposure conditions (e.g., detected contaminants and demographics).
- Multiple pathways of exposure. People can be exposed to contaminants found in more than one environmental medium (e.g., in both water and soil). Consider whether contaminants detected in more than one medium could compound potential exposures. Be cautious, however, when assessing chemicals across pathways. Effects are not always additive. Exposure frequencies and absorption rates for a single contaminant can vary by medium and route of exposure.
- Multiple-contaminant exposures. Community members are often concerned about exposure to multiple chemicals. Generally, if detected levels of contaminants are individually below conservative health guidelines and cancer risk levels, exposure to these contaminants collectively is not expected to be of health concern. Even so, you might decide that further evaluation of multiple-contaminant exposures is necessary. Perform further analysis in consultation with a toxicologist, as necessary. Refer to ATSDR’s process for evaluating mixtures in the In-Depth Toxicological Effects Analysis section of this e-manual.
The In-Depth Toxicological Effects Analysis section expands on how you should weigh these factors in your evaluation of site exposures and determining public health implications.