July 14, 2025 | Source: Chemical & Engineering News | by Britt E. Erickson

The US Environmental Protection Agency is doubling down on efforts to decrease a backlog of new pesticide active ingredients waiting for EPA approval to enter the marketplace. Since April, the agency has proposed registering four of them—cyclobutrifluram, diflufenican, isocycloseram, and trifludimoxazin.

All four pesticides contain a fully fluorinated methyl or methylene group, raising concerns that they will persist in soil and water for many years. Environmental groups argue that the chemicals are per- and polyfluoroalkyl substances (PFAS) under the definition recommended by the Organisation for Economic Co-operation and Development (OECD) in 2021. PFAS are notoriously difficult to remove from the environment, and some of them are toxic at extremely low levels.