EPA Proposes Conditional Registration of Nanosilver Pesticide Product

The U.S. Environmental Protection Agency (EPA) proposed on August 13, 2010, that it will conditionally register a pesticide product containing nanosilver as an active ingredient. According to EPA, the nanosilver active ingredient is intended for use as a preservative in textile products, including those made from natural and synthetic fibers and which are used to manufacture indoor use articles such as sheets, blankets, towels, napkins, outerwear, sportswear, sleepwear, undergarments, socks and hosiery, and outdoor use articles such as sailcloth, tarps, tents, and awnings. According to the August 12, 2010, Decision Document, EPA “views a ‘nanoscale material’ as an active or inert ingredient and any component parts thereof intentionally produced to have at least one dimension that measures between approximately 1 and 100 nanometers.” EPA is proposing to grant a four-year conditional registration under Section 3(c)(7)(C) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). Comments on the proposed conditional registration are due September 11, 2010. More information is available online.

EPA states in the Decision Document that its basis for issuing the conditional registration is:

• Insufficient time has elapsed for the generation of data since the requirement for that data was imposed;
• Use of the pesticide is in the public interest; and
• Use of the pesticide during the period that the newly required data are being developed and reviewed by EPA will not cause unreasonable adverse effects.

Until recently, EPA had not formulated a view regarding the types of data needed to evaluate the potential risks to humans and environment from exposure to this nanosilver product. The reason given for not having a position was EPA needed the input and advice from the FIFRA Scientific Advisory Panel (SAP) before it developed its position. EPA has determined that more extensive product chemistry, toxicology, exposure, and environmental data are necessary. Ultimately, EPA will use these data to determine whether the ingredient can be registered under FIFRA Section 3(c)(5), unconditional registration.

General Data Requirements

The data requirements noted below are beyond the requirements typically required to support a conventional active ingredient. These data support the conditional registered use of a nanosilver product for use to preserve textiles. It is not known whether EPA would require the same, different, and/or additional data for uses that are substantially different than used to treat textiles. EPA suggests the protocols for testing the nano-material be discussed and reviewed by its scientific staff prior to initiation of any study.

Tier 1 Data Requirements Product Chemistry

830.1550		Product Identity and Composition. Topology of the nanocomposite needs to be fully described. Information on the binding and distribution of nanosilver in the matrix (uniform or heterogeneous).
830.1750		Certified Limits. Data are needed on the upper and lower limits for the nanosilver present.
830.1800		Enforcement Method. Analytical method needs to include high resolution images of the active.
830.6313		Stability to Normal and Elevated Temperatures, Metals, and Metal Ions. Methods also need to include test of stability to sunlight, detergents, and salinity.
830.6317		Storage Stability. Storage Stability studies were submitted using accelerated method. EPA requires one-year study at ambient temperature.
830.6320		Corrosion Characteristics. See Storage Stability above.
830.7050		UV-Visible Light Adsorption. UV/visible spectrum of nano-material. This study is a reliable identification method for nanoproducts and one that the SAP recommended.
830.7520		Particle Size, Fiber Length, and Diameter (size) Distribution. Data required to characterize adequately the size distribution of the nanoproduct composite and the nanosilver particles in the composite.
830.7840		Water Solubility: Column Elution Method; Shake Flask Method is needed at pH 5, 7, and 9.
No
Guideline		Surface Area Determination. Data required to characterize adequately the size distribution of the nanoproduct composite and the nanosilver particles in the composite.

Environmental Fate

No
Guideline		Dissolution Kinetics Study. This is a fundamental study on the persistence of the nanoparticle in the environment and the extent of silver ion or nanoparticle release. This test will dictate the test substance to be used for the Tier 2 other studies.

Environmental Effects

850.1010		Acute Toxicity Freshwater Invertebrates
850.1075		Freshwater Fish Toxicity
850.2100		Avian Oral Toxicity
850.5400		Algal Toxicity, Tier 2 The proposed use of the conditionally registered nanosilver product could lead to surface water contamination that could impact fish, invertebrates, avian, and algal communities. The above studies will address concerns regarding the potential risks of the nanosilver compound and will provide toxicity endpoints applicable to ecological risk assessment.

Human Exposure

875.1200
875.1400		Applicator, Indoor Exposure. These studies provide information useful for evaluating the form, route, and level of exposure experienced by workers who handle the nanosilver compound in the process of treating textiles. The exposure data are used in conjunction with the toxicology endpoints to assess the risk to applicators.
No
Guideline		Textile Leaching Study. A leaching study is needed to determine what, if any, materials are released from the nanosilver treated textiles under conditions of use. This study should be done in the manner of Geranio et al. [no reference given] with the addition of electron microscopy to characterize the particulate.

Toxicology

870.3465		90-Day Inhalation Toxicity (Rat). This is a conditional required study triggered by the potential for inhalation exposure to the nanosilver based upon its formulation as a powder and is use in textiles.
870.3200		21-Day Dermal Toxicity (Rat). This is a conditional required study triggered by the potential for dermal exposure to the nanosilver based upon its formulation as a powder and its use in textiles. Consumer dermal exposures could occur while wearing treated clothing.
870.3650		Combined Repeat Dose Toxicity Study with Reproduction/Developmental Toxicity Screening Test. This is a conditional required study triggered by the potential for incidental oral exposure to the nanosilver based upon its use in textiles.
870.5100
870.5300
870.5375
870.5385
870.5395		Genetic Toxicity Tests. Genetic toxicity tests are used to screen chemicals for mutagenic or carcinogenic potential. The data from these tests will be used to determine if the nanosilver product is a potential mutagen or carcinogen.

Tier 2 Requirements

Tier 2 data are required if the nanoparticles are released during the Tier1 stability, dissolution, or leaching studies. Tier 2 data requirements are the same as above for all disciplines except for the environmental fate studies listed below. The testing for Tier 2 should be carried out with the material(s) that are released from the nanosilver composite.

Environmental Fate

850.1730		Fish Bioaccumulation Factor. Bioconcentration studies will assess the potential that the test substance will accumulate in fish and therefore its potential to impact the food chain.
835.1230		Adsorption/Desorption (Batch Equilibrium). EPA is requesting adsorption/desorption equilibrium studies to be conducted with the nanosilver. This information will be used to assess the sorption of a test material on soil/sediment and to estimate exposure.
No
Guideline		MITI Glucose. The purpose of the study is to assess the impact of nanosilver or its constituents on microbial activity in waster water treatment.

Conclusion

Although HeiQ will be required to generate and provide a significant amount of data, at a likely substantial cost, EPA’s proposal to register conditionally the nanosilver product represents progress in the challenge for nanomaterial manufacturers to register them as pesticides. Importantly, EPA’s registration is time-limited (four years), which is unusual under FIFRA Section 3(c)(7)(C). Conditional registrations are not so typically time-limed. From a business perspective, this limitation is not good news as it raises the possibility that data generated under the registration may be reviewed by EPA and found not to satisfy the registrant’s burden under FIFRA allowing EPA to take the position the registration will not be renewed.

In the proposed Decision Document, EPA acknowledges that there are already silver-based antimicrobial products on the market that contain nanoscale silver material, although EPA claims to have approved the registrations without knowing that the products contain nanoscale silver material. EPA intends to require that similar data be developed to support the continued registration of the other nanoscale silver products, although it remains to be seen how exactly EPA intends to achieve thus, and how successful EPA’s efforts in this regard will be.