Expansion of my critique of the ACC tool’s persistence and bioaccumulation criteria

Richard Denison, Ph.D., is a Senior Scientist.

I want to clarify and expand on the discussion in my last post on ACC’s selection of criteria for persistence (P) and bioaccumulation (B).  The bottom line remains the same:  ACC selected the least conservative values proposed by any authoritative body for these parameters. 

I want here to give a fuller picture of available P and B criteria.  It should be noted that there can be multiple types of measures of both P and B, but so as not to overly complicate the discussion, and for comparative purposes, I’m focusing here on:

• Values for transformation half-lives for P
• Values for fish bioaccumulation factors (BAF) or fish bioconcentration factors (BCF) for B

As a reminder, here’s what ACC proposed for these values:

• Half-life < 180 days = non-persistent
• BAF/BCF > 5,000 = bioaccumulative

So how do those compare to cut-offs established by authoritative bodies?

Globally Harmonized System (GHS):

• For P, GHS doesn’t use transformation half-life values.
• For B, GHS indicates that a fish BCF < 500 is “considered as indicative of a low level of bioconcentration.”

EPA’s New Chemicals Program (policy for PBTs) and Toxics Release Inventory (TRI) PBT definitions:

• For P:
  • a half-life > 60 days in water is deemed persistent and triggers imposition of testing requirements and controls via a consent order (if B and T criteria are also met)
  • a half-life > 180 days is deemed highly persistent and triggers a presumptive ban unless demonstrated to be incorrect (if B and T criteria are also met)
• For B:
  • a fish BAF/BCF > 1,000 is deemed bioaccumulative and triggers imposition of testing requirements and controls via a consent order (if P and T criteria are also met)
  • a fish BAF/BCF > 5,000 is deemed highly bioaccumulative and triggers a presumptive ban unless demonstrated to be incorrect (if P and T criteria are also met)

EPA’s Design for Environment (DfE) Program:  These are the values that I cited in my last post; they were developed by DfE staff in consultation with other EPA experts and consideration of relevant literature.  They were designed to provide greater granularity in P and B rankings to reflect the continuous nature of these chemical properties.

EU REACH Regulation Annex XIII:

• For P:
  • a half-life > 40 days in fresh water is deemed persistent
  • a half-life > 60 days in fresh water is deemed very persistent (vP)
• For B:
  • a fish BAF/BCF > 2,000 is deemed bioaccumulative
  • a fish BAF/BCF > 5,000 is deemed very bioaccumulative (vB)

Finally, it’s worth noting that the Stockholm Convention on Persistent Organic Pollutants (POPs) also has criteria to identify P and B for chemicals for which international bans on production and use are warranted (when they also meet toxicity criteria) – which of course goes far beyond mere criteria for prioritizing chemicals for further scrutiny.  Here are the POPs criteria:

• For P:  a half-life > 60 days in fresh water
• For B:  a fish BAF/BCF > 5,000

It’s clear that ACC’s P and B cut-off values are those representing the most extreme level of concern for these parameters across a range of authoritative U.S. and international bodies.