Health Risk Assessments

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Here's a spreadsheet with a partial listing of screening threshold values from Montana's incinerator rule at ARM 17.8.770(1)(c). (Please replace it if you create or come across a more complete accounting.)

This is a description of a screening level human health risk assessment conducted by Indiana Department of Environmental Management (IDEM) for a lime plant permit for Synergy Management (CRC205638). This write-up (along with a table of results not included here) was presented in Appendix A of the draft Technical Support Document accompanying a draft permit (T181-26877-00050) for public review. It's relatively straightforward and addresses calculation of and thresholds for chronic cancer and non-cancer risks. This is the spreadsheet that corresponds to this particular analysis.

This EPA web site includes a document, "Table 1," that lists chronic exposure thresholds for individual HAPs. I presume the IDEM analyses above uses these values, but I've only confirmed that for two HAPs; they may have relied on other sources for some thresholds. The web site also includes accute exposure thresholds in "Table 2," but I haven't seen those used. This site describes the sources of the threshold exposure values.

For a different approach to evaluating health risk from exposure to air pollutants, see Minnesota's Air Emissions Risk Analysis web site. They have a very well-developed process, including a downloadable spreadsheet that calculates pollutant concentrations without modeling and calculates risk factors. For an example of a Minnesota risk analysis, see Steve Ackerlund's Human Health Risk chapter in the Essar Steel SEIS on this Minnesota DNR web site.

EPA's Human Health Risk Assessment Protocol (HHRAP, links here) appears to be at least one of the foundational guidelines for conducting these analyses. Minnesota's AERA guideline document includes it as a reference. Chapter 7 of the HHRAP describes how to calculate cancer risk from Unit Risk Factors and non-cancer "hazard quotients" from Reference Concentrations (RfC). Chapter 7 also teases that it might provide target values, but it just says target values are "set by the permitting authority."
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