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: 

Executive 

Kristin Rury, 

Secretary, 

MPH y__

H~oO 

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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, Jeff Dawson, 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 of the 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 of the 

HeiQ-AGS 20 Decision Document with further refinements based on insights gained from 

further review of the toxicology database for nanosilver and on the HASPOC's experience with 

conventional pesticides. The HASPOC generally uses a risk-based weight of the 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 (http ://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 

adjustments 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 characterization of risk metrics 

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which 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 of bacteria, algae, fungus, mold, and mildew to 

reduce odors, discoloration, stains, and deterioration. Nanosilva LLC proposed that Nanosilva 

be used in a wide range of non-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 of the 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 of distinct 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 of departure 

(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 of liver toxicity (bile-duct 

hyperplasia around central vein, infiltration of inflammatory cells, and dilation of the 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 histopathological 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 intermediateterm 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 of 49 11glm3 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, of the 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. 

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For 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 intermediateterm 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. If the 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 of material 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 of these data leads to MOEs > 100,000 for users of the 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 of the 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 of concern (young children), the toxic effects of concern, and the peri- and post-natal 

unique properties of nanomaterials. 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 of concern for Nanosilva. 

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VIII. 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 of the 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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