Where did the cancer toxicity values for carcinogenic PAHs come from?
The PAH SFOs are all calculated relative to benzo[a]pyrene, which has an IRIS slope factor. The relative factors for the other PAHs can be found in Provisional Guidance for Quantitative Risk Assessment of Polycyclic Aromatic Hydrocarbons (PDF) (28 pp, 1MB) . The Toxicity Equivalency Factors (TEFs) are listed in Section 2.3.5 of the User’s Guide. The PAH IURs are all from California EPA. • Why is there no oral RfD for mercury? How should I handle mercury? IRIS gives oral RfDs for mercuric chloride and for methylmercury, but not for elemental mercury. Therefore, the SL Table follows suit. Consult your toxicologist to determine which of the available mercury numbers is suitable for the conditions at your site (e.g., whether mercury is likely to be organic or inorganic.) • The cadmium numbers are labeled “food” and “water.” Which do I use if I have another medium, such as soil? The cadmium RfDs on IRIS are based on the same study. The food RfD incorporates a 2.5% absorption adjustment; the
The PAH SFOs are all calculated relative to benzo[a]pyrene, which has an IRIS slope factor. The relative factors for the other PAHs can be found in Provisional Guidance for Quantitative Risk Assessment of Polycyclic Aromatic Hydrocarbons (PDF) (28 pp, 1.05MB, About PDF). The Toxicity Equivalency Factors (TEFs) are listed in Section 2.3.5 of the User’s Guide. The PAH IURs are all from California EPA.
