6PPD-q, PFOA, PFOS ... it's raining alphabet soup!

Notes on the Washington Department of Ecology's (WECY) updates to Aquatic Life Toxics Criteria (ALTC) (WAC 173-201A), adopted 14 August 2024 and effective 14 September 2024 from Washington state sets newlimits for toxic chemicals in water.

"This rule update includes adding aquatic life criteria for 6PPD-q, the first numeric criteria in the country adopted to protect aquatic life from the harmful effects of this chemical that comes from tire wear. We are also adding criteria for PFOA and PFOS (part of the PFAS chemical group)."

There is much of interest in this latest round of rule making, including the incorporation of mathematical modeling (MLR or multiple linear regression models) to set protective freshwater criteria for certain metals. This will require further study …

At first glance, two major issues which I have concerns have been addressed in that - from the WECY update -

“We integrated methods used in EPA’s 6PPD-quinone screening level calculations that utilize time-weighted average median lethal concentrations (LC50s) and incorporated additional scientific studies released since the rule proposal, resulting in an increase (i.e., less stringent) in the 6PPD-quinone criterion.”

The adoption of a numeric standard will take some time to develop beyond the initial 5-years data collection requirement of the (new) stormwater permit. While studies have documented of the deleterious effects of this pollutant to Coho salmon "in the lab,” what-to-do about it where the rubber meets the road (pun intended) is another matter. There are hundreds of miles of roads in this state, and mitigating 6PPD-quinone is a task that will eclipse barriers to fish passage in comparison in effort and especially public expense. The regulatory aspects of setting numerical criteria will be interesting from both the environmental and regulatory will be interesting.

A tighter criteria - as advocated by WRIA8 in their 7 May 2024 letter to Ecology - that “… [g]iven the very high acute toxicity of 6PPD-q to coho salmon, we [WRIA8] strongly support using EPA’s 5th percentile of the species sensitivity distribution method to set criteria. A freshwater acute criterion of 8 ng/L will ensure coho salmon and other aquatic life are protected.” How they determined such a specific regulatory pollutant concentration to me is unclear … call it a sanity check, but if I could suggest modeling from an environmental services point of view, it would be to establish some realistic relationship of costs to retrofit public infrastructure (i.e. roads) vs. amount of mitigation required to satisfy the numerical concentration selected … fundamental Cost vs. Benefit analysis … a requirement under any regulatory framework as much as it is a political reality.

The PFOA and PFOS is of both national and state-wide concern as it has adverse impacts on drinking water and is an immediate public health concern. As our analytical abilities to detect and measure these toxics of emerging concern advances, this interplay of pollutant concentrations and costs to mitigate I think is at the forefront of public policy. Is too much ever enough?

edited & updated: 2024-08-22 @ 15:15