"While ACC’s tool has some serious flaws and is not something that EPA has the authority or resources to utilize under current TSCA, ACC has put forth a serious proposal for prioritization that should help to raise the level of debate over this critical issue in TSCA reform."
As suggested, Denison notes that the ACC proposal offers some "refreshing elements and acknowledgements." He describes it as "substantive and specific" and is "welcome in several ways." He goes on to summarize some of the areas he feels are constructive (see his full blog entry). Notwithstanding these kudos, however, Denison does suggest that ACC's proposal seems better suited for a full TSCA Reform element and that implementation of the ACC plan is not likely to be possible under the current (and likely future) resource and funding constraints limiting EPA's activities.
Denison finds that there are "a number of quite problematic aspects of ACC's proposal," including:
- Overly rigid rules applied in lockstep: Denison finds ACC's proposed "equal basis" rule to be "sleight of hand" that will "rule out any types of information that may indicate a hazard or exposure of high concern unless it has been measured across basically all chemicals subject to prioritization." The "high hazard and high exposure" rule would allow prioritization of only those chemicals "for which high hazard and high exposure can be demonstrated;" a proposal that Denison finds to be "simply shortsighted." He also critiques ACC's "persistent and bioaccumulative" rule, which he finds includes "extremely narrow definitions of P and B" that would avoid prioritizing chemicals that would in fact be either P or B (or both).
- Consistent use of the least conservative classification values: Denison points out that the ACC proposal relies on the classification criteria developed under GHS, which he generally supports. However, he does quibble with what he feels are two limitations - GHS doesn't include every endpoint of concern and ACC chooses the least conservative values instead of adhering to GHS' cutoff values faithfully. A choice where Denison feels "ACC fails badly."
- Over-relying on limited exposure information and discounting evidence of hazard: Denison notes that ACC's tool lumps together its health and environmental hazard rankings into a single score while combining scores for its three exposure elements, which "means that a chemical that harms both people and other organisms only gets counted once, while a chemical that is low-volume and used only as an intermediate and is not P or B gets credit for being of low concern for all three attributes." The way the tool handles hazard vs exposure rankings also is likely to skew the results such as to avoid prioritization for chemicals that could indeed be problematic.