The U.S. Environmental Protection Agency (EPA) announced on December 1, 2011, that it is conditionally registering a pesticide product containing nanosilver as a new active ingredient. HeiQ AGS-20 is a silver-based antimicrobial pesticide product approved for use as a preservative for textiles. HeiQ Materials AG is a Swiss company producing high performance textile products. This is the first instance of the EPA registering a nanosilver product as a pesticide.
As a condition of registration, the EPA is requiring additional data on the product to confirm its assessment that the product will not cause unreasonable adverse effects on human health or the environment. The required studies include:
- An indoor applicator study to quantify the unit exposure values during mixing, loading, and applying the active substance
- Textile leaching and laundry drying tests to determine the nature and quantity of silver released from AGS-20 treated textiles under conditions of use.
- Sub-chronic inhalation in rats with in vivo bone marrow assay and functional observational battery, motor activity and detailed neuropathology
- Dermal toxicity in rats
- Reproduction and developmental toxicity screening tests in rats
- In-vitro micronucleus assay for mutations in genetic material
- Acute avian, fish, and aquatic invertebrate data
The following tests may be required in the future
- Sorption/Desorption Characteristics
- Bioaccumulation Characteristics
- Impacts to Wastewater Treatment
- Wastewater Treatment Removal Efficiency
- Chronic Effects to Sediment Dwelling Organisms
- Terrestrial Plant Toxicity
The EPA believes that the FIFRA section 3(c) (7)(C) registration is appropriate in this case where the data for registration of the new active ingredient are newly required or identified. In addition, it believes that granting a conditional registration is particularly appropriate given it suspects that some already-registered similar products on the market contain nanosilver as the active ingredient. While the EPA approved these registrations without knowledge that these products might contain nanoscale silver and without specifically assessing any potential risks that might be associated with any nanosilver contained in those products, they are nonetheless on the market. To avoid disparate treatment, the EPA intends to seek similar data along with comparable terms on already registered products that are identified to contain nanosilver.
During the public comment period from 12 August to 13 September, 2010 the EPA received 45 comments on the proposed decision document.
- 27 from citizens
- 3 from public treatment works operators
- 1 from a trade association (Copper Development)
- 2 from state agencies (Wisconsin DHS, California DPR)
- 3 from industry (Dow, BASF, HeiQ)
- 9 from NGOs
Apart from the industry representatives, commenters were mainly opposed to the registration, citing among other reasons the potential for environmental contamination and the lack of sufficient toxicology data to conduct an adequate human risk assessment.
The Agency responded to the Environmental issue by saying that AGS-20 could lead to reductions in the overall use of silver in textiles. For example, Geranio et al. (2009, Environ. Sci. Technol., 43:8113) reported that commercially available textiles treated with electrolytically deposited silver contained 21.6 mg/g silver as compared to textiles treated with AGS-20, which contained a maximum of 0.099 mg/g silver.
On the Toxicology question, the Agency said that it has determined that there is sufficient inhalation and oral toxicity data for nanosilver that can be used to determine the potential health effects caused by nanosilver released from AGS-20. It acknowledges that the database is incomplete with respect to reproductive and developmental toxicity, neurotoxicity, immunotoxicity, and mutagenicity and is therefore using the maximum 10-fold database uncertainty factor to extend the inhalation and oral toxicity data to cover the missing information in those areas The Agency is requiring studies investigating these effects in order to complete the toxicity database for AGS-20 and any material that leaches from treated textiles. A new risk assessment will be conducted when these data are available. In the interim, the Agency believes that the 10 fold database uncertainty factor is health protective.
Representatives from BASF and Dow commented that it was unclear why the EPA had chosen to identify this submission as containing a new active substance. The Notice as written was thought likely to generate confusion among current registrants of the active ingredient silver.
The BASF representative commented that silver is not a new active ingredient. It has been an active ingredient in pesticide products since the 1970s and was addressed during re-registration (RED issued 1992) and is still being addressed through registration review. BASF Corporation is a registrant of several pesticide products containing silver that are approved for the same uses.
The response of the EPA was to say that Silver is not a new active ingredient but it could not conclude that the nanoscale material in AGS-20 was an active ingredient in any currently registered pesticide. Until recently, the Agency has generally not focused on the size of an ingredient as an attribute relevant when determining if the product in an application is identical or substantially similar in composition to a registered pesticide product. However, a nanoscale ingredient may have properties that are different from those of conventionally-scaled ingredients. Therefore, a nanoscale ingredient may also have different environmental health and safety properties. Accordingly, for a product containing an ingredient that is a nanoscale version of a conventionally-sized active or inert ingredient, or a different nanoscale version of a nanoscale material, contained in an already-registered product, EPA necessarily will need data on that nanoscale material.
The decision document and supporting material can be found at Docket ID # EPA-HQ-OPP-2009-1012:
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