Regulation of Persistent Chemicals in Hazardous Waste: A Case Study of Washington State, USA.

Despite ongoing controversy, several strategic frameworks for defining chemicals of concern (e.g., persistent, bioaccumulative, toxic [PBT]; persistent, mobile, toxic [PMT]; persistent organic pollutant [POP]) share persistence as a key criterion. Persistence should be considered over the entire chemical life cycle from production to disposal, including hazardous waste management. As a case study, we evaluate persistence criteria in hazardous waste regulations in Washington state, USA, illustrate impacts on reported waste, and propose refinements in these criteria. Although Washington state defines persistence based on half-life (>1 y) and specific chemical groups that exceed summed concentration thresholds in waste (i.e., >0.01% halogenated organic compounds [HOCs] and >1.0% polycyclic aromatic hydrocarbons [PAHs]), persistence is typically addressed with HOC and PAH evaluation but seldom with half-life estimation. Notably, persistence is considered (with no specific criteria) in corresponding federal regulations in the United States (Resource Conservation and Recovery Act). Consequently, businesses in Washington state report annual amounts of state hazardous waste (including persistent waste) separately from federal hazardous waste. Total state-only waste, and total state and federal waste combined, nearly doubled (by weight) from 2008 to 2018. For the period 2016 to 2018, persistence criteria captured 17% of state-only waste and 2% of total state and federal waste combined. Two recommendations are proposed to improve persistence criteria in hazardous waste regulations. First, Washington state should consider aligning its half-life criterion with federal and European Union PBT definitions (e.g., 60-120 d) for consistency and provide specific methods for half-life estimation. Second, the state should consider expanding its list of persistent chemical groups (e.g., siloxanes, organometallics) with protective concentration thresholds. Ultimately, to the extent possible, Washington state should strive toward harmonizing persistence in hazardous waste regulations with corresponding criteria in global PBT, PMT, and POP frameworks. Integr Environ Assess Manag 2021;17:455-464. © 2020 SETAC.