Comments on EPA/IRIS Draft Guidance Document on Relative Potency Factors for the PAHs

In 2010, PCTC participated with 5 other trade associations in a multi-industry coalition that came together to review and comment on the External Review Draft of the Relative Potency Factor (RPF) Approach for Polycyclic Aromatic Hydrocarbon (PAH) Mixtures (External Review Draft) prepared by the US EPA’s Integrated Risk Information System (IRIS) program. The draft was released for public comment prior to peer review by EPA’s Science Advisory Board (SAB). The SAB’s review is posted on EPA’s web site at the link provided above. Overall, the SAB found the RPF approach to be scientifically problematic when applied to “whole mixtures” – that is, to substances such as coal tar, asphalt, and the thousands of other materials that contain mixtures of PAHs. The SAB recommended that EPA develop a whole mixtures approach, with an eye to replacing the RPF approach as data warrant. In its cover letter, the SAB recommendation is summarized as follows:

The SAB also recommends that EPA consider developing a whole mixtures approach for PAHs.  This approach could validate the RPF approach and in the future, could replace the RPF approach.  The Agency should set this as a strategic initiative, with a specific timeline and benchmarks, that lays the foundation for an underlying concerted research program.

The SAB agreed with many of the comments made in the industry coalition’s comments, which are available on the federal web site at this link: Comments on Draft Guidance Document on Relative Potency Factors for the PAHs.