Predicting PBT: How to Tell if a Chemical Could be Persistent, Bioaccumulative, or Toxic
Jessie Kneeland, Ph.D.
Many chemical regulatory assessments focus on the chemical’s potential to be persistent, bioaccumulative, or toxic (PBT) to human health or the environment. For example, EPA has raised concerns about potential PBT characteristics of onium photoacid generators (PAGs), resulting in an extensive collaboration within the semiconductor industry to better characterize PAG risks. PBT regulatory status reflects specific regulatory definitions; while these definitions can vary from one jurisdiction to another (e.g., TSCA in US vs. REACH in the EU), most jurisdictions place restrictions on the use of PBT or very persistent and very bioaccumulative (vPvB) chemicals. For new chemicals, these properties are often predicted on the basis of the chemical structure or a limited set of physicochemical parameters. This presentation will review each part of the PBT definition, including common regulatory thresholds. We will outline key data and models commonly used to assess and predict PBT status, including limitations to those models. Finally, we will recommend a tiered framework for completing a PBT assessment.