The Long Goodbye: Finally Moving on from the Relative Potency Approach to a Mixtures Approach for Polycyclic Aromatic...

Area of Science:

• Environmental Health Sciences
• Toxicology
• Risk Assessment

Background:

• The relative potency approach, using potency equivalence factors (PEFs), is standard for estimating human health risks from polycyclic aromatic hydrocarbon (PAH) mixtures.
• PEFs are typically based on ratios to benzo[a]pyrene (BaP) and are often expressed qualitatively.

Purpose of the Study:

• To systematically develop quantitative PEFs for 18 selected carcinogenic PAHs.
• To assess the adequacy of existing carcinogenicity data for quantifying PEFs.

Main Methods:

• A systematic approach using a priori and dose-response criteria was applied.
• An exhaustive search identified 48 animal bioassay datasets, with only a few suitable for modeling PEFs.
• Data quality and availability for low-dose responses were critical selection criteria.

Main Results:

• Only four datasets were appropriate for modeling PEFs.
• Quantitative PEFs could only be determined for benzo[b]fluoranthene and cyclopenta[c,d]pyrene.
• Current knowledge is insufficient to support quantitative PEFs for most PAH mixtures.

Conclusions:

• Existing data on PAH carcinogenicity is inadequate for establishing quantitative PEFs for mixtures.
• An interdisciplinary approach is needed to improve PAH risk assessment.
• Recommendations include using alternative testing, better mixture characterization, and understanding bioavailability and exposure routes.