The U.S. Court of Appeals for the Ninth Circuit voided the U.S. Environmental Protection Agency (EPA) conditional registration for the nanosilver-containing antimicrobial pesticide, NSPW-L30SS (“NSPW” or Nanosilva). In an opinion filed on May 30, 2017, the Court found that EPA failed to support its finding that early approval of Nanosilva was in the public interest.

Pesticides, including antimicrobials, generally must be registered with EPA under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) prior to distribution or sale in the United States. EPA may, however, grant a temporary, conditional registration for a pesticide upon determination that its use will not cause any unreasonable adverse effect on the environment and that its use is in the public interest. In 2015, EPA granted conditional registration for Nanosilva. The National Resources Defense Council, and the Center for Food Safety and the International Center for Technology Assessment, separately challenged EPA’s conditional approval of NSPW in court. (See National Resources Defense Council v. U.S. Environmental Protection Agency, case number 15-72308, and Center for Food Safety; International Center for Technology Assessment v. U.S. Environmental Protection Agency et al., case number 15-72312.) The two cases were combined in August 2015.

Based on a substantial evidence standard, the U.S. Court of Appeals for the Ninth Circuit held that EPA failed to support that conditional registration of NSPW is in the public interest. Although the Court found that substantial evidence supported EPA’s conclusion that NPSW has lower application and mobility rates than conventional silver pesticides, it disagreed that substantial evidence supported EPA’s conclusion that use of NSPW is in the public interest on the basis that it has the potential to reduce the amount of silver released into the environment. More specifically, the Court ruled that EPA’s conclusion in this regard was based on two unsubstantiated assumptions: (1) that current users of conventional-silver pesticides would replace those pesticides with NSPW; and (2) that NSPW would not be incorporated into new products to the extent that such incorporation would actually increase the amount of silver released into the environment.” Due to these assumptions, the Court agreed with the Petitioners that EPA’s public-interest finding for NSPW is not supported by substantial evidence as required by FIFRA.