The Fallacy of Prioritization of Existing Chemicals for Risk Evaluation Under TSCA

The creation of an elaborate prioritization process for existing chemicals was one of the many amendments to TSCA in 2016. Under TSCA section 6, EPA was required to develop “a risk-based screening process, including criteria for designating chemical substances as high-priority substances for risk evaluation or low-priority substances for which risk evaluations are not warranted at this time.” EPA was given 9-12 months to prioritize a substance, which included not one but two 90-day public comment periods. And importantly, there are only two designations for any substance that goes through the prioritization process – low-priority or high-priority. There are no in-betweens and no way to pause the prioritization process once it has been initiated. And upon formal designation as high-priority, the substance must undergo an even more time and resource-intensive risk evaluation process.

In practice, however, the prioritization process is a fallacy. Perhaps unbeknownst to the drafters of the 2016 amendments, TSCA now also contained two powerful disincentives to a true prioritization process. First, Congress only required EPA to designate at least 20 low-priority chemicals. EPA certainly has the discretion to designate more than 20 low-priority chemicals, but why would it? It makes more sense for EPA to devote its resources to implementing what it is statutorily required to do.

Secondly, initiating prioritization for any substance is fraught with peril. The only way for EPA to manage the number of risk evaluations for existing chemicals is for EPA to know whether the substances it selects for the prioritization process will be designated as high-priority. Why? Suppose EPA were to select a handful of substances for prioritization with the anticipation that one or more would be designated as low-priority. But then, during the prioritization process and through public comment, all the substances meet the criteria for high-priority. Consequently, EPA would have unwittingly increased the number of risk evaluations by more than it had anticipated. And because every completed risk evaluation triggers another, EPA is permanently stuck with additional risk evaluations, on top of the over 20 risk evaluations EPA has underway, all of which have missed their statutory timeline for completion.

Given these disincentives, the prioritization process of TSCA section 6 is a fallacy. Every substance picked for “prioritization” will be designated in the end as a high-priority substance. Clearly, the prioritization process needs to be entirely revamped so that it truly is a means to prioritize chemicals for risk evaluation.