California Federal Court Rules on the Conditional Registration of Nanosilver-containing Pesticide, Nanosilva

The Policy

What it does

Specifies what is needed for nanomaterial-containing pesticides to meet the public interest requirement for conditional registration under the Federal Insecticide, Fungicide, and Rodenticide Act.


Natural Resources Defense Council v. US Environmental Protection Agency, 857 F.3d 1030 (9th Cir. 2017) is a federal case that vacated the conditional registration of NSPW-L30SS – also called Nanosilva, a nanosilver-containing pesticide – under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). 

Prior to this case, the Environmental Protection Agency (EPA) had been promulgating a policy wherein the EPA regarded each product that incorporated nanosilver as containing a new active ingredient.  Pesticides containing new active ingredients qualified for conditional registration under section 136a(c)(7)(C) and did not require all the risk data that unconditional registration requires so long as the EPA, among other requirements, determines that use of the pesticide is in the public interest. The U.S. Court of Appeals for the Ninth Circuit concluded the EPA had failed to meet the public-interest requirement specified in section 136a(c)(7)(C) when granting a conditional registration to Nanosilva. 

Although the EPA asserted Nanosilva registration could potentially fulfill the public-interest requirement, the court held that this potential was insufficient for compliance with 136a(c)(7)(C).  According to the court’s interpretation of the statute, the public-interest requirement necessitated the EPA to provide substantial evidence prior to conditional registration.  Moving forward, the EPA cannot rely on the “potential” for a product to be in the public interest.  Furthermore, the EPA cannot depend on post-hoc arguments from historical observations when justifying conditional registrations under 136a(c)(7)(C).  The EPA should evaluate information from analogous products when such information is available. 

Additionally, the National Resources Defense Council (NRDC) argued that Nanosilva LLC, the manufacturer of Nanosilva, had sufficient time to provide the data necessary for an unconditional registration; however, the court disregarded the time argument as the court decided to vacate the Nanosilva registration prior to addressing the issue.


FIFRA is federal law established in 1947 and amended in 1972.  The Act establishes the guidelines for pesticide examination and registration and is enforced by the EPA.  In 2009, a FIFRA Scientific Advisory Panel convened to address the hazards and exposures associated with silver nanoparticles.  In its summary, the Panel suggested that the EPA should consider the hazard profiles of silver nanoparticles to be different from the profiles of conventional silver.  In 2013, the Court of Appeals for the Ninth Circuit vacated in part a conditional registration for AGS-20, another silver nanoparticle-containing pesticide.  The court held that the EPA erred in its lack of concern regarding health risks associated with AGS-20.  The EPA failed to consider risk mitigation, which contravened the unreasonable adverse effects clause of conditional registration.

The Science

Science Synopsis

Nanomaterials are chemical substances that measure between 1-100 nanometers (nm, 10-9 meters) along at least one dimension.  Nanomaterials exhibit chemical and physical characteristics distinct from their bulk material counterparts.  Because of their different properties, nanomaterials interact with environmental chemicals to yield new and unclear manifestations.  The EPA uses conservative assumptions to derive unique risk profiles and is constantly refining methods used to assess nanomaterial characteristics.  The active ingredients in the proprietary Nanosilva formulation are silver nanoparticles.  In response to companies seeking to use nanosilver in their pesticides, a scientific advisory panel suggested that the distinct biological distributions of silver nanoparticles could lead to unique hazard profiles. 

Silver is an antimicrobial agent that is becoming increasingly incorporated into pesticide formulation and materials as a preservative. In relation to their ionic counterparts, silver nanoparticles have greater surface areas to which microorganisms are exposed; the superior surface area improves the chances of microbial death.  As a result, the amounts of silver nanoparticles needed for products to be effective (application rates) are lower than conventional ionic silver-containing pesticides.  In addition, silver nanoparticles are designed remain chemically stable throughout the product’s time of usage.  Relevant to the current case, silver nanoparticles are less mobile – that is, they dissolve from the product and transported throughout the environment – than ionic silver. 

The Nanosilva formulation enhances product stability by anchoring silver nanoparticles to silica microparticles embedded in a polymer textile.  By adding Nanosilva to polymeric materials, unwanted effects from bacterial and fungal growth, such as foul odors, are prevented.  The strong bonds formed between the silver nanoparticles and silica microparticles minimize the possibility that Nanosilva leaches and contributes to hazardous silver levels.