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

*Published:* 2011-09-29
*Author:* 

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

I want to clarify and expand on the discussion in [my last post ](http://blogs.edf.org/nanotechnology/2011/09/20/acc%e2%80%99s-chemical-prioritization-tool-helpful-but-flawed-and-off-the-mark-for-epa-to-use-without-tsca-reform/)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)](http://live.unece.org/trans/danger/publi/ghs/ghs_rev00/00files_e.html):

- 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)](http://www.epa.gov/fedrgstr/EPA-TOX/1999/November/Day-04/t28888.htm) and [Toxics Release Inventory (TRI) PBT definitions](http://www.epa.gov/fedrgstr/EPA-TRI/1999/January/Day-05/tri34835.htm):

- 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](http://www.epa.gov/dfe/alternatives_assessment_criteria_for_hazard_eval.pdf): These are the values that I cited in [my last post](http://blogs.edf.org/nanotechnology/2011/09/20/acc%e2%80%99s-chemical-prioritization-tool-helpful-but-flawed-and-off-the-mark-for-epa-to-use-without-tsca-reform/); 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](http://guidance.echa.europa.eu/docs/guidance_document/information_requirements_part_c_en.pdf?vers=20_08_08):

- 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)](http://www.ipen.org/ipenweb/poprc/criteria.html) 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.