### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

MEMORANDUM DATE: November 12, 2013 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION



### SUBJECT: Nanosilva: Considerations on Tier 2 Toxicity Studies PC Code: 072599 Decision No.: N/A Petition No.: N/A Risk Assessment Type: N/ A TXR No.: 0056817 MRID No.: N/A DP Barcode: N/ A Registration No.: N/A Regulatory Action: N/ A Case No.: N/A CAS No.: N/A 40CFR:NA FROM: Kristin Rury, MPH 

# y__ O**~** Executive Secretary,

# H~oO Health Effects Division (HED; 7509P) THROUGH: Jess Rowland, Co-Chair Anna Lowit, Ph.D., Co

-Chair Hazard and Science Policy Council (HASPOC) HED (7509P) TO: Seiichi Murasaki Antimicrobial Division (AD; 751 OP) MEETING ATTENDEES: HASPOC Members: Anna Lowit, Elissa Reaves, Elizabeth Mendez, JeffDawson, Jonathan Kough, John Chen, Michael Metzger, PV Shah Presenter: Jonathan Leshin, Timothy Dole, Timothy Leighton Other Attendees: Alexandra LaMay, Julie Van Alstine, Kristin Rury, Linda Taylor, Uma Habiba

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### I. PURPOSE OF MEETING In August, 2009 Nanosilva LLC submitted an application to register Nanosilva, a pesticide containing nanosilver as a new active ingredient. As part ofthe registration application, Nanosilva LLC submitted acute toxicity studies, a study that determined the amount of silver leaching from textiles and plastics incorporating Nanosilva, and a request to waive some ofthe required toxicity studies. Previously, the Hazard and Science Policy Council (HASPOC) reviewed Tier 1 toxicity studied needed for Nanosilva (TXR#0056700). The Antimicrobials Division (AD) requested that the Hazard and Science Policy Council (HASPOC) discuss Tier 2 data needs for Nanosilva; the HASPOC met on October 24, 2013. 

### II. GENERAL CONSIDERATIONS FOR NANOSCALE MATERIALS DATA NEEDS The HASPOC previously considered toxicology data needs for nanoscale materials to facilitate a transparent and consistent approach to evaluating pesticides containing nanoscale ingredients (TXR0056700). The foundation for these considerations can be found in Appendix A ofthe HeiQ-AGS 20 Decision Document with further refinements based on insights gained from further review ofthe toxicology database for nanosilver and on the HASPOC's experience with conventional pesticides. The HASPOC generally uses a risk-based weight ofthe evidence (WOE) approach in considering toxicology data needs. This WOE approach does not involve a "check-box approach," but instead evaluates and weighs the confidence and uncertainty associated with multiple scientific areas (htt p ://www.epa.gov/pesticides/regulating/part 15 8

-toxdata-reguirement.pdf). The following four principles are used by HASPOC to determine the need for additional toxicity studies for conventional pesticides, and can be applied, with ad

j ustments as described below, to nanoscale materials. 1. 

### Physical-Chemical Properties, Including Particle Information: Some important nanoscale properties for consideration are: form (e.g., powder, liquid) , composition (i.e., whether or not the material is a composite) , size, shape, coating, and surface charge. 

### 2. Use 

### Pattern and Exposure Scenarios: Exposure patterns and pathways need to be evaluated and described to ensure that toxicity data match, to the extent possible, the appropriate duration and route of exposure in addition to the population of interest. This description needs to explicitly consider exposure to occupational handlers and consumers separately. 

### 3. Toxicity Profile: First, the available experimental toxicology studies need to be summarized for the nanoscale ingredients in a specific pesticide product being evaluated. Then, available, relevant toxicology data on the same nanoscale ingredients from the open literature needs be considered. Uncertainty factors also need to be described. 

### 4. Margins of Exposure (MOEs) or Other Appropriate Risk Metrics (e.g., 

### Percent Reference Dose): The WOE approach includes charact erization of risk metrics

Page 2 of5which incorporate toxicity and exposure together. MOEs should be compared to the target MOE and associated confidence and uncertainties need to be described. III. SUMMARY OF USE PROFILE AND RISK ASSESSMENT FOR NANOSILV A Nanosilva is a liquid suspension containing 1% nanosilver particulates by weight where the nanosilver active

-ingredient is attached to crystalline silica via a thiolate bond. Nanosilva LLC is proposing that Nanosilva be incorporated into plastics and textiles at a maximum of 0
.003% nanosilver by weight to suppress the growth ofbacteria, algae, fungus, mold, and mildew to reduce odors, discoloration, stains, and deterioration. Nanosilva LLC proposed that Nanosilva be used in a wide range ofnon-food contact categories including housewares, building materials, bathroom fixtures and accessories, electronics, appliances , personal care products, automotive equipment, hospital and institutional facility equipment, sporting goods, and textiles. There are no product-specific intermediate

- or long-term experimental toxicity studies available for Nanosilva. EPA evaluated the risk from occupational and consumer exposure using experimental toxicology data available in the scientific literature for nanosilver. Oral and dermal exposure is being assessed using oral toxicity studies by Kim et al. (2008) and Kim et al. (20 1 0)
. These studies used CMC coated nanosilver with average diameter of 56 and 60 nm, respectively; EPA acknowledges that the Kim studies use nanosilver which is different from the diameter and surface coating ofthe nanosilver in Nanosilva. Unlike most toxicity studies from the scientific literature, however, these studies were completed according to Organization for Economic Cooperation and Development (OECD) guidelines
. Moreover, these studies identified histopathological patterns in the liver that were indicative ofdistinct adverse effects. EPA has determined that the no-observed adverse

-effect level (NOAEL) of30 mg/kg/day from the 28-day oral toxicity study by Kim et al
. (2008) is the point ofdeparture (POD) for short

-term oral exposures (<30 days) to the nanosilver in Nanosilva based on significant increases in alkaline phosphatase and cholesterol and significant changes in hematology that were accompanied by histopathological evidence ofliver toxicity (bile

-duct hyperplasia around central vein, infiltration ofinflammatory cells, and dilation ofthe central vein) seen at the lowest

-observed adverse-effect level (LOAEL) of300 mg/kg/day
. EPA has also determined that the LOAEL of 30 mg/kg/day based on histopat hological evidences of liver toxicity (bile

-duct hyperplasia with focal, multifocal, or lobular necrosis) in both males and females from the 90

-day oral toxicity study by Kim et al. (2010) is the POD for intermediate

term oral exposures (1 to 6 months) to the nanosilver in Nanosilva. A dermal absorption factor (DAF) of 6.7% based on a human clinical study by Wan et al. (1991) is applied to extrapolate from the oral to dermal routes. EPA has determined that the NOAEL of49 11glm 3 is the POD for short- and intermediate-term inhalation exposures to the nanosilver in Nanosilva
. The inhalation toxicity study by Song et al. (2012) used uncoated nanosilver with average diameters of 14 to 15 nm, respectively, which is similar to the diameter, but different than the surface coating, ofthe nanosilver in Nanosilva. EPA has determined that the NOAEL is 49 Jlglm3 based on adverse histopathological patterns in lung tissue observed at the 117 11g/m3 dose
.
Page 3 of 5For short

-term exposure, the target MOE of 1,000 is applied based on the standard 10

-fold uncertainty factors for potential interspecies extrapolation and intraspecies variation, and a 1 0- fold database uncertainty factor (accounting for differences in size, charge, and coating from open literature studies). In addition, a 3

-fold uncertainty factor (UF) was used to account for the lack ofNOAEL in the 90 day oral toxicity study by Kim et al., 2010 making the intermediate

term oral target MOE 3,000
. EPA does not typically consider long

-term occupational exposures to antimicrobial preservatives used to treat plastics or textiles because application ofthese chemicals does not typically occur on a daily basis for more than 6 months. However, consumer exposure to Nanosilver may result in long

-term exposure. The maximum recommended target MOE is 3,000 (U.S. EPA, 2002), which has already been established for intermediate

-term exposures. Therefore, an additional UF for extrapolation from a subchronic study to chronic exposure durations has not been applied
. At the previous HASPOC meetings discussing Nanosilva (TXR#0056700) the HASPOC concluded that a subchronic inhalation study and a reproduction/developmental toxicity screening study are needed to support the new use registration ofNanosilva
. In addition, data to evaluate the potential for neurotoxicity and in vivo bone marrow assay are needed
. Immunotoxicity and subchronic dermal studies are not needed and can be waived. The HASPOC recommends that the registrant submit protocols for the needed studies for the Agency to review. Ifthe registrant has additional exposure or toxicity information which could be used to further refine the data needs described here for Nanosilva, the registrant may submit a rebuttal for review. Tier 2 toxicity studies needed are determined based on the outcome ofmaterial leaching study(ies) with the nanomaterial. In the case ofNanosilva, a textile study is available and acceptable for use in risk assessment. The textile leaching study shows low leaching potential and use ofthese data leads to MOEs > 100,000 for users ofthe textiles
. However, the existing plastics study used a protocol not approved by EPA. This study tested less than the maximum nanosilver concentration of 30 mg/kg and the study did not use physiological fluids. As such, the study needs to be repeated. Upon receipt ofthe new plastics study, the agency will review the data and if acceptable, incorporate into a WOE analysis. In the event that the WOE supports the need for additional toxicity data, the HASPOC recommends a non-guideline study. This study would be used to assess incidental oral exposures for infants and children who mouth plastic toys and household items treated with Nanosilva. A non-guideline peri- and post-natal study is preferred over guideline developmental or developmental neurotoxicity studies since a non-guideline study can tailored toward the population ofconcern (young children), the toxic effects ofconcern, and the peri

- and post
-natal unique properties ofnanomaterials. Guideline developmental toxicity study focuses more on growth, maternal effects, and structural abnormalities resulting from in utero exposure. Guideline developmental studies doe not include post-natal exposure relevant to young children. The DNT study is a large, expensive study which includes both prenatal and postnatal exposure. However, a tailored, more focused study would more efficiently evaluate the lifestage and endpoints ofconcern for Nanosilva
. Page 4 of5VIII. HASPOC CONCLUSIONS In summary, similar to the Tier 1 data requirements, the HASPOC recommends that the WOE approach be conducted prior to requiring Tier 2 toxicity testing ofNanosilva
. This WOE approach should limit further testing only to studies that will evaluate effects relevant to exposed populations. The results ofthe textiles leaching study do not support the need for additional toxicity testing. In the event that a new plastics leaching study supports the need for additional toxicity testing, then the HASPOC recommends a peri

- and post-natal non-guideline study
.

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