UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

DATE: August 27, 2013 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Nanosilva: Summary of Hazard and Science Policy Council (HASPOC) 

Meetings on June 20 and August 15,2013: Recommendations on Data 

Requirements and Waivers for Nanosilva. 

PC Code: 072599 DP Barcode: N/ A 

Decision No.: N/A Registration No.: NIA 

Petition No.: N/A Regulatory Action: N/A 

Risk Assessment Type: N/A Case No.: NIA 

TXR No.: 0056700 CAS No.: N/A 

MRID No.: N/A 40 C~ NA • 

FROM: Julie Van Alstine, MPTT ~ .~.1 ; 11 01/\...~+-a-.____ Executive Secretary,~~ Health Effects Division (HED; 09P) 

THROUGH: Jess Rowland, Co-Chair 

Anna Lowit, Ph.D., Co-Chai 

Hazard and Science Policy Counc · 

HED (7509P) 

TO: Jed Costanza, Ph.D. 

Antimicrobial Division (AD; 751 OP) 

JUNE 20,2013 MEETING ATTENDEES: 

HASPOC Members: Anna Lowit, Elizabeth Mendez, Jeff Evans, Jeff Dawson, Jess Rowland, 

Jonathan Chen, Michael Metzger, P.V. Shah, Ray Kent 

Presenter: Jed Costanza 

Other Attendees: Joey Bever, Steve Weiss, Jonathan Leshin, Tim McMahon, Christopher 

Schlosser, Jaime D'Agostino, Minerva Mercado, Monique Perron, Yung 

Yang, Monica Hawkins, Tim Leighton, Amber Aranda, Michelle Centra, 

Jenny Tao, Tim Dole, Uma Habiba, Anwar Dunbar, Kristin Rury, Julie 

Van Alstine 

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AUGUST 15, 2013 MEETING ATTENDEES: 

HASPOC Members: Anna Lowit, Elissa Reaves, Elizabeth Mendez, Jeff Dawson, John 

Kough, Michael Metzger, P.V. Shah, Ray Kent 

Presenter: Timothy Leighton 

Other Attendees: Jonathan Leshin, Timothy Leighton, Joey Bever, Seiichi Murasaki, 

Kristin Rury, Julie Van Alstine 

I. PURPOSE OF MEETING

In August, 2009 Nanosilva LLC submitted an application to register Nanosilva, a nanosilver 

containing pesticide, as a new active ingredient. Nanosilva LLC submitted acute toxicity studies, 

a study that determined the amount of silver leaching from plastic coupons incorporating 

Nanosilva, and a request to waive some of the required toxicity studies. The Antimicrobials 

Division (AD) requested that the Hazard and Science Policy Council (HASPOC) evaluate two 

issues: 1) general considerations for toxicity data needs for nanoscale materials and 2) specific 

data needs for Nanosilva. The HASPOC met on June 20 and August 15, 2013 to discuss all of 

these issues. 

II. GENERAL CONSIDERATIONS FOR NANOSCALE MATERIALS DATA NEEDS

In this memo the HASPOC delineates important considerations for toxicology data needs for 

nanoscale materials to facilitate a transparent and consistent approach to evaluating pesticides 

containing nanoscale ingredients. 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/part158-tox-data-requirement.pdf). The following 

four principles used by HASPOC for toxicity needs for conventional pesticides can be applied, 

with adjustments, 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. 
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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 

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 NANOSILVA

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 30 mg per kg of article 

treated to suppress the growth of bacteria, algae, fungus, mold, and mildew, which cause 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. (2010). 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) of 30 

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) of 300 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. 
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EPA has determined that the NOAEL of 49 μg/m3 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 μg/m3

 based on adverse histopathological patterns in 

lung tissue observed at the 117 μg/m3

 dose. 

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 10-

fold database uncertainty factor. In addition, a 3-fold uncertainty factor (UF) was used to 

account for the lack of NOAEL 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 of these 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. 

IV. STUDY WAIVER REQUESTS

1. Physical-Chemical Properties: 

Table 1. Physical-Chemical Properties of Nanosilva. 

Parameter Nanosilva 

Form Liquid Suspension with 1% nanosilver by weight

Composition Nanosilver-Silica Composite 

Transmission Electron Microscopy 

(TEM) Image 

Overall Particle Size of Composite Average of 320 nm 

Shape of Nanosilver Spherical 

Size of Nanosilver (diameter) 3 to 18 nm 

Coating PVP and sulfur 

Surface Charge Negative 
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2. Exposure scenarios: EPA evaluates the risk of occupational exposures from 

mixing, loading, and applying or handling pesticide products. EPA expects that 

occupational inhalation and dermal exposures are likely to occur during mixing 

and loading of Nanosilva during preparation of a master batch. Nanosilva is 

proposed to be mixed into polymer and polymer-based products to suppress the 

growth of bacterial, algae, fungus, mold, and mildew, which cause odors, 

discoloration, stains, and deterioration of plastics and textiles. Because plastics 

incorporating Nanosilva could be subsequently used to manufacture children’s 

toys and textiles worn by children, it is assumed that children will be exposed to 

products containing Nanosilva. EPA expects children’s exposures are likely to 

occur during incidental oral and dermal exposures to plastics and textiles 

incorporating Nanosilva. 

To evaluate the risk from exposure to nanosilver that might break away from the 

Nanosilva complex, Nanosilva LLC submitted studies showing that silver at 

concentrations greater than the analytical detection limit were not found leaching 

from plastic coupons and shirts incorporating Nanosilva (Table 2). Thus, based 

on the available data, there is little exposure to nanosilver from plastic and textile 

incorporating Nanosilva. EPA calculated the daily-dose to workers assuming that 

all the silver in Nanosilva was freely available as nanosilver. Likewise for the 

daily-dose to consumers, EPA assumed that silver leaching from plastic coupons 

and shirts incorporating Nanosilva, which was at concentrations below the 

analytical detection limit, was in the form of nanosilver as found in Nanosilva. 

Table 2. Amount of Silver Released from Shirts and Plastics Incorporating 

Nanosilva. 

Parameter Nanosilva 

Source of Information Nanosilva Study 

Treatment Method Incorporated into 

Shirts 

Incorporated into 

Plastics 

Amount of Silver Released (% of 

silver in article) 1.6 to 0.9%* <0.1%* 

Transmission Electron Microscopy 

(TEM) Image Not enough silver to image 

Overall Particle Size of Composite Not enough silver 

Shape of Nanosilver Not enough silver 

Size of Nanosilver (diameter) Not enough silver 

Coating Not enough silver 

Surface Charge Not enough silver 

* Calculated assuming that silver at a concentration of one-half the detection limit 

was released during leaching studies. 

3. Margins of Exposure (MOEs): The MOE for occupational inhalation exposure to 

the nanosilver in the Nanosilva liquid suspension is 2,500 if workers use close-system 

loading when mixing and loading the Nanosilva liquid suspension (Target 

MOE=1,000). The MOE for dermal exposure to the nanosilver in the Nanosilva 
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liquid suspension is greater than 1,000,000 if workers use closed-system loading 

when mixing and loading the Nanosilva liquid suspension, which is significantly 

greater than the target MOE of 3,000. The MOEs calculated for the incidental oral 

exposure to nanosilver in plastic toys incorporating Nanosilva are 310,000 for 

children 6 to <12 months old, 550,000 for children 1 to <2 years old, and 940,000 for 

children 2 to <3 years old (Target MOE=3,000). The MOEs calculated for the dermal 

exposure to nanosilver in flooring incorporating Nanosilva are 820,000 for children 6 

to <12 months old, 860,000 for children 1 to <2 years old, and 910,000 for children 2 

to <3 years old (Target MOE=3,000). The MOEs calculated for the dermal exposure 

to nanosilver in textiles incorporating Nanosilva are 340,000 for children 6 to <12 

months old, 360,000 for children 1 to <2 years old, and 370,000 for children 2 to <3 

years old (Target MOE=3,000). The other route-specific scenarios for incidental oral 

exposure to flooring and textiles incorporating Nanosilva provide MOEs of 1,000,000 

or higher.

The aggregate MOEs for children who are, within the same short time frame, 

mouthing a toy, flooring, and a textile containing Nanosilva while wearing a textile 

containing Nanosilva and crawling on flooring incorporating Nanosilva are greater 

than 100,000 for all lifestages, indicating that the risk for short- and intermediate-term 

simultaneous exposure to plastics and textiles incorporating Nanosilva is not a 

concern (Target MOE = 3,000; U.S. EPA, 2002). The calculated MOEs for dermal 

and incidental oral exposure to plastics and textiles incorporating Nanosilva are 

greater than 100,000, indicating that daily exposure to plastics and textiles 

incorporating Nanosilva for greater than 6 months are not likely to be of concern. 

4. Toxicity: Nanosilva LLC submitted results from guideline acute animal-toxicity tests 

completed using high-level doses of a liquid suspension containing Nanosilva with 

1% nanosilver by weight. There were no mortalities or abnormalities noted in test 

animals after administration of Nanosilva by oral, dermal, and inhalation routes at 

dose levels of up to 5,000 mg/kg and 2.05 mg/L, respectively. Nanosilva caused 

moderate to no irritation to skin or eyes at dose levels of up to 0.1 mL and 0.5 mL, 

respectively, and was not a skin sensitizer. The currently available subchronic oral 

toxicity studies indicate that nanosilver causes liver and kidney toxicity in laboratory 

animals where silver is distributed to all organs and tissues with accumulation of 

silver in the brain and male animal testes. Subchronic inhalation toxicity studies also 

identified liver toxicity as well as lung effects including chronic alveolar 

inflammation. There were potential neurotoxic effects identified with increases in 

neurotransmitter concentrations and loss of spatial cognition; however, these same 

effects were not observed in a follow-on study. The in vitro Ames and chromosome 

aberration assays indicate that nanosilver is not expected to be mutagenic while the 

mammalian cell micronucleus and mouse lymphoma with comet assay suggest that 

nanosilver may have mutagenic potential. However, the lack of genotoxicity from the 

in vivo study indicates that there is inadequate information to assess mutagenic (and 

hence carcinogenic) potential of nanosilver. Finally, there is not enough information 

on the reproductive and developmental toxicity for nanosilver at this time. 
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V. HASPOC WOE EVALUATIONS

1. Inhalation Study: Previously, the Office of Pesticide Programs (OPP) used a set of 

criteria to determine whether an inhalation study could be waived. These criteria 

considered the scientific information available for the chemical, including its: 1) 

degree of irritation and corrosivity; 2) volatility; 3) aerosol particle size; and 4) Acute 

Toxicity Category and extrapolated MOEs (e.g., MOEs 10 times higher than the 

target). In 2009, OPP developed an issue paper on risk assessment approaches for 

semi-volatile pesticides. As part of that issue paper, an analytical comparison was 

conducted of oral and inhalation experimental toxicology studies. In general, this 

analysis showed that the degree to which oral PODs were protective of potential 

inhalation toxicity varied. In many cases the oral POD was protective, but in some 

cases the inhalation PODs were significantly more sensitive. Currently, OPP uses a 

WOE approach that builds upon OPP’s experience using the criteria listed above and 

conclusions from the 2009 SAP. As approaches for route-to-route extrapolation 

continue to evolve and improve, OPP may incorporate additional considerations into 

the WOE analysis. 

The HASPOC has concluded that a subchronic inhalation study with Nanosilva is 

needed to reduce the uncertainties related to the differences in the physical properties 

of the nanosilver particle used in the Song et al. (2012) study and the Nanosilva 

particles. This approach considered all of the available hazard and exposure 

information for nanosilver including: 1) the difference in the physical/chemical 

properties between the available nanosilver inhalation toxicity studies and the 

nanosilver in Nanosilva; 2) the sensitive effects noted in the inhalation study of 

decreases in physiological measures of lung function combined with chronic alveolar 

inflammation and macrophage accumulation in the lungs; and 3) the use of an 

inhalation POD which results in an MOE that is near the Agency’s level of concern 

when exposure is assessed with a closed system. 

2. Subchronic Dermal Toxicity Study: Based on a WOE approach, the HASPOC 

concludes that a dermal study is not required because the use of an oral POD results 

in MOEs that are ≥1,000,000 for occupational and greater than 300,000 for consumer 

exposure pathways. These MOEs are well above the Agency’s level of concern. 

3. Prenatal Developmental Toxicity Study: HASPOC has concluded that a 

reproduction/developmental toxicity screening test (Modified OCSPP 870.3550/ 

OECD TG 421) conducted via the inhalation route is needed. This determination is 

based on a WOE analysis which provides: 1) female workers of child bearing age 

will handle Nanosilva during mixing and loading; 2) as noted above, occupational 

MOEs are near the Agency’s level of concern when exposure is assessed with closed 

system and additional information is needed to reduce uncertainty; 3) there are 

currently no acceptable studies on the reproductive and developmental toxicity for 

nanosilver. However, there were dose-dependent increases in the concentration of 

silver in the testes of rats after oral ingestion, inhalation, and injection of nanosilver 

and, in another study, nanosilver was distributed to major maternal organs and extra-
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embryonic tissues although no adverse morphological effects on the developing 

embryos were observed. 

4. Bacterial Reverse Mutation Test, Detection of Gene Mutations in Somatic Cells 

in Culture, In Vitro Mammalian Cytogenetics, Mammalian Bone Marrow 

Chromosome Aberration Test: The mutagenicity studies [Bacterial Reverse 

Mutation Test (OPPTS 870.5100), Detection of Gene Mutations in Somatic Cells in 

Culture (OPPTS 870.5300), In Vitro Mammalian Cytogenetics (OPPTS 870.5375), 

Mammalian Bone Marrow Chromosome Aberration Test (OPPTS 870.5385)] are 

satisfied because the available in vitro studies suggest that nanosilver may have 

mutagenic potential. The one available in vivo micronucleus assay performed on rats 

after oral administration of nanosilver at concentrations of up to 1,000 mg/kg/day 

(Kim et al., 2008) indicated that nanosilver is neither clastogenic nor aneugenic in 

vivo; however, there was no positive proof that nanosilver reached the bone marrow 

in the micronucleus assay. The HASPOC has concluded that an in vivo bone marrow 

assay is needed and that this assay can be added as a component of the subchronic 

inhalation study. 

5. Neurotoxicity Battery: Acute and subchronic neurotoxicity studies can provide 

important scientific information on potential nervous system effects from pesticide 

exposure. These studies offer data on a wide range of functional tests for evaluating 

neurotoxicity including sensory effects, neuromuscular effects, learning and memory 

and histopathology of the nervous system. The study completed by Hadrup et al.

(2012b), which reported significant increases in neurotransmitter concentrations (e.g., 

dopamine) after oral administration of nanosilver to rats at concentrations of up to 9 

mg/kg/day, lacks histological support for determining NOAEL/LOAELs. Liu et al.

(2013) reported no effects on the spatial cognition or hippocampal activity of mice 

after injecting nanosilver into the body cavity (i.e., intraperitoneal injection) at 

concentrations of up to 50 mg/kg. The effects on spatial cognition and hippocampal 

activity observed by Liu et al. (2012) after administering nasal drops containing 

nanosilver at concentrations of 3 and 30 mg/kg to rats suggest possible neurotoxic 

effects from the inhalation of nanosilver. However, EPA believes that the doses used 

in the Liu et al. (2012) study were greater than the maximum dose used in the 

inhalation toxicity study by Song et al. (2012). Unless appropriate study designs are 

used, many guideline studies are considered inadequate in their assessment of 

behavioral effects and do not use optimal methods to evaluate the potential toxicity to 

the nervous tissue structure and function. The HASPOC has concluded that there is 

potential for neurotoxicity based on the open literature studies. However, in lieu of a 

standard guideline study, neurotoxicity evaluation (functional observational battery, 

motor activity and detailed neuropathology) can be added as a component of the 

subchronic inhalation study. 

6. Immunotoxicity: The HASPOC recommends that a waiver can be granted for an 

immunotoxicity study for Nanosilva, based on the following considerations: 
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 The currently available oral toxicity studies indicate that nanosilver causes liver 

and kidney toxicity in laboratory animals where silver is distributed to all organs 

and tissues with accumulation of silver in the brain and male animal testes. 

Inhalation toxicity studies also identified liver toxicity as well as lung effects 

including chronic alveolar inflammation. 

 PODs from the most sensitive endpoints are currently used for assessing risks 

from short and intermediate oral and inhalation exposures. 

 The toxicology database for nanosilver does not reveal any evidence of treatmentrelated effects on the immune system. The overall WOE suggests that this 

chemical does not directly target the immune system. 

IV. HASPOC CONCLUSIONS

In summary, the HASPOC concludes that a subchronic inhalation study and a 

reproduction/developmental toxicity screening study are needed. 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.