Registration Decision for NSPW-L30SS (previously referred to as 

"N anosilva") 

A Materials Preservative for Use in Textiles and Plastics 

/a k o senger, Dire tor 

Offile of P sticide Programs 
ii 

TABLE OF CONTENTS 

Executive Summary ................................................................................................................................... iv

I. Regulatory Decision Summary ............................................................................................................... 1

II. Background ............................................................................................................................................ 1

2.1 Regulatory History ............................................................................................................................. 1

2.2 FIFRA Scientific Advisory Panel (SAP) Meeting .............................................................................. 2

2.3 Proposed Decision Document ............................................................................................................ 3

III. Product Description, Testing, and Use ............................................................................................... 3

3.1 Product Description ............................................................................................................................ 3

3.2 Product Use ........................................................................................................................................ 3

3.3 Product Testing and Waivers .............................................................................................................. 3

IV. Hazard Characterization of Nanosilver ............................................................................................. 5

4.1 Acute Human Toxicology of NSPW-L30SS ...................................................................................... 6

4.2 Subchronic and Chronic Toxicological Studies Available for Nanosilver ......................................... 6

4.2.1 Oral .............................................................................................................................................................. 6

4.2.2 Inhalation..................................................................................................................................................... 8

4.2.3 Dermal ......................................................................................................................................................... 9

4.2.4 Reproductive and Developmental Toxicity of Nanosilver ........................................................................ 10

4.2.5 Mutagenicity of Nanosilver ....................................................................................................................... 11

4.2.6 Silver Ions ................................................................................................................................................. 13

4.3 Absorption, Distribution, Metabolism, and Excretion (ADME) of Nanosilver ............................... 14

4.3.1 Injection of Nanosilver .............................................................................................................................. 14

4.3.2 Oral Administration of Nanosilver ............................................................................................................ 15

4.4 Safety Factor for Infants and Children (FQPA Safety Factor) ......................................................... 16

4.5 Antimicrobial Resistance .................................................................................................................. 16

4.6 Point of Departure Selections and Target Margin of Exposure ........................................................ 16

4.6.1 Point of Departures for NSPW-L30SS ...................................................................................................... 17

4.6.2 Target Margin of Exposure ....................................................................................................................... 20

4.6.3 Margin of Exposure ................................................................................................................................... 20

V. Occupational and Consumer Risk Assessment ................................................................................. 21

5.1 Occupational Risk Assessment for Mixing and Loading the NSPW-L30SS Liquid Suspension .... 21

5.1.1 Occupational Exposure Preparing the Master Batch Containing NSPW-L30SS ...................................... 22

5.1.2 Occupational Margins of Exposure ........................................................................................................... 22

5.1.3 Conclusions for Occupational Risk ........................................................................................................... 24

5.1.4 Occupational Exposure and Health Data Requirements ............................................................................ 25

5.2 Consumer Risk Assessment for Products Incorporating NSPW-L30SS .......................................... 25

5.2.1 Consumer Exposures to Plastics and Textiles Incorporating NSPW-L30SS ............................................ 26

5.2.2 Consumer Margins of Exposure to Plastics Incorporating NSPW-L30SS ................................................ 30

5.2.3 Consumer Margins of Exposure to Textiles Incorporating NSPW-L30SS ............................................... 34

5.2.4 Aggregate MOES for Plastics and Textiles Incorporating NSPW-L30SS ................................................ 37

5.2.5 Conclusions for Consumer Risk ................................................................................................................ 39

5.2.6 Consumer Exposure and Health Data Requirements ................................................................................ 40

VI. Environmental Risk Assessment ....................................................................................................... 40

6.1 Environmental Fate .......................................................................................................................... 40

6.1.1 Nanosilver ................................................................................................................................................. 41

6.1.2 Silver Ions ................................................................................................................................................. 41

6.1.3 Impacts to Wastewater Treatment/Septic Systems .................................................................................... 41

6.2 Environmental Toxicity .................................................................................................................... 42

6.2.1 Silver Ions ................................................................................................................................................. 42

6.2.2 Aquatic Toxicity of Nanosilver ................................................................................................................. 42

6.3 Aquatic Risk Assessment ................................................................................................................. 46

6.3.1 Aquatic Risk Quotient ............................................................................................................................... 46

6.3.2 Conclusions for Aquatic Risk.................................................................................................................... 48
iii 

6.4 Ecological Effects and Environmental Fate Data Requirements. ..................................................... 49

VII. Regulatory Action ............................................................................................................................. 50

7.1 Legal Framework .............................................................................................................................. 50

7.2 Findings and Registration Decision .................................................................................................. 51

7.3 Basis for Conditional Registration ................................................................................................... 52

7.3.1 Data Generation ........................................................................................................................................ 52

7.3.2 Public Interest ............................................................................................................................................ 53

7.3.3 No Unreasonable Adverse Effects ............................................................................................................ 54

References:................................................................................................................................................. 56

Appendix A – Evaluation of Nanosilva LLC’s Data Waiver Requests ................................................ 61

Appendix B – Data Requirements, Enforceable Schedule, and Conditions of the Conditional 

Registration for NSPW-L30SS ................................................................................................................ 64

LIST OF TABLES 

Table 1 – Product Testing for the NSPW-L30SS Liquid Suspension .......................................................... 4

Table 2 – Acute Toxicity Profile for the NSPW-L30SS Liquid Suspension ................................................ 6

Table 3 – Toxicity Endpoints for Use in the Risk Assessment of NSPW-L30SS Nanosilver .................... 18

Table 4 – Unit Exposures for Mixing and Loading the NSPW-L30SS Liquid Suspension ....................... 22

Table 5 – Occupational Handlers Inhalation MOEs for the Nanosilver in NSPW-L30SS ......................... 23

Table 6 – Occupational Handlers Dermal MOEs for the Nanosilver in NSPW-L30SS ............................. 24

Table 7 –Silver Concentrations in Fluid Contacting NSPW-L30SS Treated Plastic Coupons................... 27

Table 8 – Concentration of Silver Released from Shirts Incorporating NSPW-L30SS .............................. 29

Table 9 – Amount of Silver Released from Shirts Incorporating NSPW-L30SS ....................................... 30

Table 10 – Incidental Oral MOEs for Plastic Toys Incorporating NSPW-L30SS ...................................... 31

Table 11 – Dermal MOEs for Flooring Incorporating NSPW-L30SS ........................................................ 32

Table 12 – Incidental Oral MOEs for Flooring Incorporating NSPW-L30SS ............................................ 34

Table 13 – Inhalation MOE for Drying Textiles Incorporating NSPW-L30SS .......................................... 35

Table 14 – Dermal MOEs for Textiles Incorporating NSPW-L30SS ......................................................... 36

Table 15 – Incidental Oral MOES for Textiles Incorporating NSPW-L30SS ............................................ 37

Table 16 – Aggregate MOEs for Toys, Flooring and Textiles Incorporating NSPW-L30SS ..................... 38

Table 17 – Nanosilver Toxicity to Aquatic Species .................................................................................... 43

Table 18 – Reported Characteristics of Nanosilver Materials in the Aquatic Species Toxicity Studies .... 44

Table 19 – Risk Quotients for Nanosilver in Surface Water ...................................................................... 48
iv 

Executive Summary 

EPA is granting a conditional registration for the Nanosilva LLC product NSPW-L30SS 

(previously referred to as “Nanosilva”) under section 3(c)(7)(C) of the Federal Insecticide, 

Fungicide and Rodenticide Act (FIFRA). EPA’s basis for the conditional registration is that: 

 NSPW-L30SS contains nanosilver as an active ingredient and the nanosilver in NSPWL30SS is not in any currently registered pesticide; 

 Use of NSPW-L30SS will not cause unreasonable adverse effects on the environment 

during the four year period when newly required data are being developed; 

 Insufficient time has elapsed for the newly required data to be generated and submitted; 

and 

 Use of NSPW-L30SS is in the public interest. 

NSPW-L30SS, which contains 1% nanosilver by weight, is the subject of an application 

submitted by Nanosilva LLC in August 2009 (MRID 47828900). Nanosilva LLC requested that 

the nanosilver in NSPW-L30SS be registered as a new active ingredient because it was not an 

active ingredient in any currently registered pesticide product. NSPW-L30SS is a liquid 

suspension containing silica-sulfur-nanosilver particulates where the nanosilver is attached to 

amorphous silica via a thiolate bond. 

EPA is making a registration decision for non-food contact uses of NSPW-L30SS incorporated 

into plastics and textiles to suppress the growth of bacteria, algae, fungus, mold and mildew, 

which cause odors, discoloration, stains, and deterioration. The plastics and textiles will contain 

less than 0.003% silver by weight. 

EPA determined that workers, consumers, and the environment could be exposed to: 

1. silver ions released from NSPW-L30SS; 

2. NSPW-L30SS; and/or 

3. nanosilver that might break away from NSPW-L30SS. 

In evaluating the risk from exposure to silver ions, EPA relied on the existing reregistration 

decision for silver which concluded that the human health or ecological risk from exposure to 

silver ions derived from plastics and textiles incorporating NSPW-L30SS are not of concern. 

For purposes of evaluating the risk from short-term exposure to NSPW-L30SS, Nanosilva LLC 

submitted results from acute animal-toxicity tests completed using high-level doses of NSPWL30SS showing that there were no mortalities or abnormalities in test animals after 

administration of NSPW-L30SS by oral, dermal, and inhalation exposure routes. NSPW-L30SS 

caused moderate irritation to the eyes of test animals, and was not a skin sensitizer. Based on 

these results, shipping containers filled with NSPW-L30SS are required to carry a label stating 

“CAUTION” where contact with eyes or clothing should be avoided. Nanosilva LLC submitted a 

request to waive the required intermediate-term toxicity studies because silver leaches from 

plastic coupons incorporating NSPW-L30SS below the limit of detection (LOD) and because of 

the lack of toxicity noted in the acute animal-toxicity tests completed using high-level doses of 

NSPW-L30SS. 

To evaluate occupational exposure to the nanosilver that might break away from NSPW-L30SS, 

EPA calculated the daily-dose to workers assuming that all the silver in NSPW-L30SS was 

freely available as nanosilver. EPA believes that this assumption overestimates the daily-dose of 
v 

nanosilver that a person could potentially receive when working with NSPW-L30SS. To evaluate 

consumer exposure to the nanosilver that might break away from plastics and textiles 

incorporating NSPW-L30SS, Nanosilva LLC submitted studies showing that silver leaches from 

plastic coupons and shirts incorporating NSPW-L30SS below the LOD. Thus, there is little or no 

exposure to nanosilver from plastics and textiles incorporating NSPW-L30SS. EPA assumed that 

silver leaching from plastic coupons and shirts incorporating NSPW-L30SS was at one-half the 

analytical LOD and was in the form of nanosilver as found in NSPW-L30SS. 

There are no intermediate- or long-term human or environmental toxicity studies available for 

NSPW-L30SS or for the nanosilver released from products incorporating NSPW-L30SS. In the 

absence of intermediate-term toxicity studies, EPA evaluated the risk from occupational and 

consumer exposure using intermediate-term hazard data available in the scientific literature for 

other nanosilvers. Because of the potential difference between the nanosilver in the available 

toxicity data and the nanosilver in NSPW-L30SS, along with the lack of an acceptable 

developmental and reproductive toxicity study for nanosilver, EPA used a maximum 10-fold 

database uncertainty factor when evaluating the risk from exposure to NSPW-L30SS and the 

nanosilver released from products incorporating NSPW-L30SS. 

Impact to the environment was assessed based on ecotoxicity studies available in the scientific 

literature for other nanosilvers and environmental exposure from indoor use (assuming that 300 

million people (U.S. population) each purchased one t-shirt containing NSPW-L30SS) and from 

the plastic lumber use (assuming that 1% of the projected yearly production of plastic lumber in 

the U.S. would contain NSPW-L30SS). All t-shirts in the textile scenario were assumed to be 

washed weekly for 52 weeks, releasing 1.6% of the initial silver load as nanosilver per wash to 

waste water and in the plastic scenario all of the silver in the plastic lumber was assumed to be 

released during the year. 

Using toxicity data on nanosilver, conservative occupational exposure assumptions, leaching 

data showing minimal consumer exposure to nanosilver, and maximum values for risk 

uncertainty factors, EPA is able to determine that for the period of conditional registration, the 

use of NSPW-L30SS will not cause unreasonable adverse effects on the environment during the 

period when newly required data are being developed. 

As a condition of the registration, EPA is requiring that Nanosilva LLC conduct a number of 

studies during the period of conditional registration. The required information includes 

characterization studies to better characterize NSPW-L30SS and the nanosilver in NSPWL30SS; stability and dissolution studies to determine if nanosilver breaks away from NSPWL30SS and the rate nanosilver dissolves; and a new plastic leaching study to address specific 

uncertainties and confirm EPA’s risk findings. In addition, EPA is requiring the following 

inhalation route-specific studies: 

 90-Day Inhalation Toxicity (Rat) (OCSPP GLN 870.3465) modified to include a 

functional observational battery, motor activity and detailed neuropathology 

 Reproduction/Developmental Toxicity Screening Test via inhalation route (Modified 

OCSPP GLN 870.3550/ OECD TG 421) 

Although there is no risk concern for workers who use close-system loading when mixing and 

loading the NSPW-L30SS liquid suspension, EPA is requiring these studies to account for 

potential physiochemical differences of the nanosilver and because there are currently no 

acceptable studies on the reproductive and developmental toxicity for nanosilver. The EPA is 
vi 

also requiring a freshwater acute invertebrate study using Daphnia magna to confirm Agency 

assumptions and ecological risk findings. Additional particle characterization, human health 

effects, ecological effects and environmental fate studies may be triggered based on the results of 

these studies. The testing requirements are based on a tiered approach. 

These studies must be completed within four years after issuing the conditional registration. This 

time period was chosen to allow time for protocol reviews prior to initiation of the studies, 

completion of the studies, and Agency review of the study results. EPA will evaluate these data 

as they are submitted to confirm EPA’s determination that the use of NSPW-L30SS will not 

cause unreasonable adverse effects to human health and the environment during the conditional 

registration period while these data are being developed. If Nanosilva LLC fails to take 

appropriate steps to initiate the required studies, or if Nanosilva LLC fails to submit the protocols 

or data, EPA will issue a notice of intent to cancel NSPW-L30SS’s registration under FIFRA 

section 6(e). In addition, the conditional registration for NSPW-L30SS will automatically expire 

four years after being issued. Nanosilva LLC should request an amendment to remove the 

expiration date once they have submitted the required data if they wish to continue to sell and 

distribute NSPW-L30SS in the United States. 

EPA believes that the use of NSPW-L30SS is in the public interest. Use of NSPW-L30SS may 

lead to less environmental loading of silver as compared to currently registered products with the 

same use patterns. 
1 

I. Regulatory Decision Summary 

EPA is granting a conditional registration for the Nanosilva LLC product named “NSPW-L30SS” 

under section 3(c)(7)(C) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). 

NSPW-L30SS, which contains 1% nanosilver by weight, is the subject of an application submitted 

by Nanosilva LLC in August 2009 (MRID 47828900). Nanosilva LLC requested that the 

nanosilver in NSPW-L30SS be registered as a new active ingredient because it was not an active 

ingredient in any currently registered pesticide product. 

As described in the risk assessment sections of this document, EPA has determined that use of 

NSPW-L30SS will not cause unreasonable adverse effects on the environment during the fouryear period when newly required data are being developed. 

In August, 2009 Nanosilva LLC submitted acute toxicity studies required under 40 CFR part 1611

, 

a study that determined the amount of silver leaching from plastic coupons incorporating NSPWL30SS, and a request to waive some required studies. The waiver request was based on the low 

exposure to NSPW-L30SS given that the product is embedded in plastic and the submitted 

leaching study for a plastic incorporating NSPW-L30SS indicated that silver was not released at 

concentrations above the analytical limit of detection (LOD). In May 2013, Nanosilva LLC also 

submitted a study showing that silver was not released at concentrations above the analytical LOD 

from textiles incorporating NSPW-L30SS. EPA is granting the registration request with 

requirements for new data as terms and conditions on the NSPW-L30SS registration. Nanosilva 

LLC, however, has not had sufficient time to generate and submit these newly required data. 

EPA has determined that use of NSPW-L30SS is in the public interest. EPA believes that 

Nanosilva LLC’s product may lead to less environmental loading of silver as compared to 

currently registered products containing silver salts with the same use patterns. 

EPA is requiring Nanosilva LLC to conduct a number of studies as a condition of registration. 

These studies must be completed within a time duration of four years which was chosen to allow 

time for protocol reviews prior to initiation of the studies, completion of the studies, and Agency 

review of the study results. EPA will evaluate these data as they are submitted during the period of 

the conditional registration to confirm EPA’s risk assessment. If Nanosilva LLC fails to take 

appropriate steps to initiate the required studies, or if Nanosilva LLC fails to submit the protocols 

or data, EPA has the authority to use the procedures of FIFRA section 6(e) to cancel Nanosilva 

LLC’s registration. In addition, Nanosilva LLC’s conditional registration for NSPW-L30SS will 

automatically expire four years after being issued. Nanosilva LLC will need to submit an 

application to obtain an unconditional registration if they wish to continue to sell and distribute 

NSPW-L30SS in the United States. 

II. Background 

2.1 Regulatory History 

In August 2009, Nanosilva LLC submitted an application for the registration of a new 

antimicrobial pesticide product named NSPW-L30SS, a nanosilver-based product that was 

proposed for use as a materials preservative additive with no food contact uses. Nanosilva LLC’s 

application claimed that NSPW-L30SS contains a new nanosilver active ingredient not contained 

 

1 At the time Nanosilva LLC applied to register NSPW-L30SS, test guidelines were listed in 40 CFR part 161. In 

2013, updated test guidelines were finalized in 40 CFR part 158W. 
2 

in any currently registered silver-based pesticide products and should be given a registration under 

FIFRA section 3(c)(7)(C) (MRID 47828900). 

2.2 FIFRA Scientific Advisory Panel (SAP) Meeting 

In November, 2009 EPA convened a meeting of the FIFRA Scientific Advisory Panel (SAP) to 

address a number of questions associated with assessing the hazard of and exposure to nanosilver 

and other nanoscale metal-based pesticides (FIFRA SAP, 2009). In general, the SAP advised that 

the toxicity of nanosilver could differ from and might be higher than other forms of silver (e.g., 

silver ions). 

The SAP was unsupportive of bridging among silver-based materials with different properties. 

However, the SAP indicated that bridging would be appropriate for materials of similar size and 

essentially identical physical properties and that bridging between silver ions released from 

nanosilver and the existing database for silver ions is feasible (FIFRA SAP, 2009). The SAP 

cautioned about extrapolating from one nanosilver formulation to another when assessing hazards 

because differences in particle formulation (e.g., coating and inert ingredients) could affect 

biological activity, among other things. 

The SAP commented that not enough literature was available to draw any firm conclusions 

regarding human (occupational or consumer) and environmental exposures to nanosilver under 

realistic use scenarios. Potentially, three major routes exist for human exposure to nanoparticles: 

oral, inhalation, and dermal. Only a few studies in rodents were known that investigated the 

toxicity of nanosilver from exposure by these routes. Nor was there much information on the level 

of human exposure to nanosilver by these routes, for either workers or consumers using products 

containing nanosilver. The same situation existed for the environmental fate and transport of 

nanosilver. The ability to measure concentrations of nanosilver in the environment along with the 

environmental exposure pathways, bioavailability, toxicity, and potential impact of nanosilver on 

ecological systems were not well quantified. Furthermore, little or no information on the fate of 

nanosilver in soils and sediments was found. As a result, the SAP recommended a case-by-case 

approach to hazard and exposure assessment (i.e., product-by-product). The SAP also advised that 

existing requirements may need to be adjusted to obtain data appropriate to assess the fate, 

degradation, metabolism, mobility, dissipation, and accumulation of nanomaterials. 

The SAP report further suggested that existing information on conventional silver could be useful 

but would not necessarily be sufficient in assessing potential nanosilver risks. The SAP 

recommended that EPA treat nanosilver differently from its conventional silver counterpart in 

evaluating proposed nanosilver product applications (in terms of both data requirements and the 

conduct of risk assessments). Moreover, the Panel recommended that EPA require additional data 

on the physical chemistry, exposure potential, and the potential hazard to human health and the 

environment. 

Historically, EPA has considered applications for pesticide products that claim to be identical or 

substantially similar in composition to a registered product as so-called “me-too registrations” 

under FIFRA registration authorities. Until recently, EPA generally has not focused on the size or 

surface coating of an ingredient as attributes relevant to 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 and properties that differ from the atoms or molecules from 

which the nanoscale ingredient is constructed. Therefore, a nanoscale ingredient may also have 

different environmental health and safety properties. Accordingly, for a product containing an 
3 

ingredient that is a nanoscale version of a conventionally-sized active or inert ingredient contained 

in an already-registered product or a different nanoscale version of a nanoscale material that is an 

active or inert ingredient in an already registered pesticide product, EPA may require additional 

data to assess the nanoscale material and to make the requisite statutory findings. 

2.3 Proposed Decision Document 

On August 27, 2013, EPA posted a draft version of this Decision Document to the Pesticides 

Public Regulatory Docket for public comment. EPA received comments on the draft Decision 

Document along with supporting information for a period of 30 days until September 26, 2013. 

EPA is posting responses to the ten comments received regarding this decision in the Pesticides 

Docket. 

III. Product Description, Testing, and Use

3.1 Product Description 

NSPW-L30SS is a liquid suspension containing silica-sulfur-nanosilver particulates where the 

nanosilver is attached to amorphous silica via a thiolate bond. The particles are formed by reacting 

silver nitrate and polyvinylpyrrolidone (PVP) with spherical silica particles that have been 

modified with thiol groups and are suspended in ethanol (Lee et al. 2007). The diameter of the 

spherical silica core particles are 320 nm on average (Lee et al., 2006). The nanosilver particles 

form with time and have an average diameter of 6.9 nm (minimum diameter of 3 nm and 

maximum diameter of 12 nm) after 10 minutes and 10.6 nm (minimum diameter of 5 nm and 

maximum diameter of 18 nm) after 2 hours (Lee et al., 2007). The liquid suspension contains 1% 

nanosilver by weight with average diameters between 6.9 and 10.6 nm (minimum diameter of 3 

nm and maximum diameter of 18 nm). 

The label states that NSPW-L30SS, which contains 1% nanosilver by weight, is to be formulated 

into a polymeric intermediate known as a master batch at rates up to 2% of NSPW-L30SS. The 

application rate for treatment of the finished consumer product is 5.0 - 15.0% of the master batch 

that contains NSPW-L30SS. Thus, the final product to which a consumer may be exposed will 

contain less than 0.003% nanosilver by weight. 

3.2 Product Use 

NSPW-L30SS is registered to be incorporated into non-food contact plastics and textiles to 

suppress the growth of bacteria, algae, fungus, mold and mildew, which cause odors, 

discoloration, stains, and deterioration. 

3.3 Product Testing and Waivers 

As an applicant for registration of a new active ingredient in 2009, Nanosilva LLC was required to 

submit all the applicable information and studies under 40 CFR part 161. Nanosilva LLC 

submitted results from testing of NSPW-L30SS to determine the product identity and composition, 

physical and chemical properties, and acute toxicity as summarized in Table 1. Some of these tests 

were completed using standard EPA test guidelines2

 prior to consulting with EPA. Although these 

test results provided useful information for NSPW-L30SS, the guidelines on which they are based 

have not been adapted generally for use with nanoscale particles. EPA anticipates that these 

guidelines will require revision going forward in terms of their application to nanoscale materials. 

 

2

 Available at http://www.epa.gov/ocspp/pubs/frs/home/guidelin.htm 
4 

As a result, until revisions are completed, it is recommended that future applicants for products 

containing nanoscale materials consult with the EPA prior to performing any tests. 

Table 1 – Product Testing for the NSPW-L30SS Liquid Suspension 

Guideline 

Number 

Guideline Name Required under 

40 CFR 

Nanosilva LLC 

Submission (MRID) 

Product Identity and Composition

830.1550 Product identity and composition 161.155 47828901 

830.1600 Description of materials to produce product 161.160 47828902 

830.1620 Description of production process 161.162 47828903 

830.1650 Description of formulation process 161.165 47828904 

830.1670 Discussion of formulation of impurities 161.167 47828905 

830.1700 Preliminary analysis 161.170 47828906 

830.1750 Certified limits 161.175 47828907 

830.1800 Enforcement analytical method 161.180 47828908 

Physical and Chemical Properties

830.6302 Color 161.190 47828909 

830.6303 Physical state 161.190 47828910 

830.6304 Odor 161.190 47828911 

830.6317 Storage stability 161.190 47828912 

830.6320 Corrosion characteristics 161.190 47828912 

830.7000 pH 161.190 47828913 

830.7100 Viscosity 161.190 47828914 

830.7220 Boiling Point/Boiling Range 161.190 47828915 

830.7300 Density 161.190 47828916 

830.7520 Particle size, fiber length, and diameter 

distribution 

Information in Lee et al., 2006 and 2007 

used to address data requirement 

830.7840 Water solubility 161.190 47828917 

Health Effects (Toxicology)

870.1100 Acute Oral Toxicity 161.340 47828918 

870.1200 Acute Dermal Toxicity 161.340 47828919 

870.1300 Acute Inhalation Toxicity 161.340 47828920 

870.2400 Acute Eye Irritation 161.340 47828921 

870.2500 Acute Dermal Irritation 161.340 47828922 

870.2600 Skin Sensitization 161.340 47828923 

In addition to the test results listed in Table 1, Nanosilva LLC submitted the following study to 

support the registration of NSPW-L30SS: 

Plastic Leaching Study 

 Leaching protocol for NSPW-L30SS-treated LLDPE polymer in food and food simulated 

matrices as functions of time, temperature and chemistry of the matrix with determined 

migration values (MRID 47828925) 

Nanosilva LLC also submitted a request to waive the following data requirements: 

1. Hydrolysis (OCSPP Guideline Number (GLN) 835.2120) 

2. Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids (OCSPP GLN 850.1010) 

3. Fish Acute Toxicity Test, Freshwater and Marine (OCSPP GLN 850.1075) 

4. Avian Acute Oral Toxicity Test (OCSPP GLN 850.2100) 

5. 90-Day Dermal Toxicity (OCSPP GLN 870.3250) 
5 

6. Prenatal Developmental Toxicity Study ( OCSPP GLN 870.3700) 

7. Bacterial Reverse Mutation Test (OCSPP GLN 870.5100) 

8. Detection of Gene Mutations in Somatic Cells in Culture (OCSPP GLN 870.5300) 

9. In Vitro Mammalian Cytogenetics (OCSPP GLN 870.5375) 

10. Mammalian Bone Marrow Chromosome Aberration Test (OCSPP GLN 870.5385) 

11. Immunotoxicity (OCSPP GLN 870.7800) 

Waivers for the above studies were requested because of the lack of acute toxicity noted in the six 

acute toxicity studies (MRID 47828918 through 47828923), because NSPW-L30SS has a specific 

gravity greater than water, because NSPW-L30SS has low solubility in water as determined by the 

water column generator method (MRID 47828917), due to the non-leaching characteristic of 

NSPW-L30SS, and because silver was below the level of detection (LOD) in leaching studies 

conducted with a plastic incorporating NSPW-L30SS (MRID 47828925). Evaluation of Nanosilva 

LLC’s Data Waiver Requests is detailed in Appendix A. 

In response to EPA’s review of the leaching and product chemistry studies, Nanosilva LLC 

subsequently submitted the following documents: 

Nanosilver Content of Plastic Coupons Containing NSPW-L30SS 

 Determination of Silver Content and Silver Recovery Rate for NSPW-L30SS (MRID 

48652901) 

Description of Production and Formulation Process 

 Lee, J.M., Kim, D.W., Jun, Y.D., Oh, S.G. 2006. Preparation of silica-silver heterogeneous 

nanocomposite particles by one-pot preparation strategy using polyol process: Sizecontrolled immobilization of silver nanoparticles. Materials Research Bulletin 41:1407-

1416.(MRID 48379901 and 48379903) 

 Lee, J.M., Kim, D.W., Kim, T.H., Oh, S.G. 2007. Facile route for preparation of silicasilver heterogeneous nanocomposite particles using alcohol reduction method. Materials 

Letters 61:558-1562. (MRID 48379902 and 48379904) 

Textile Leaching Study 

 Nanosilva LLC prepared and submitted on August 20, 2012 a draft protocol titled “The 

Quantification and Characterization of Silver Released from Textiles Treated with NSPWL30SS (NSPW-L30) as a Results of Washing” 

 The Quantification and Characterization of Silver Released from Textiles Treated with 

NSPW-L30SS As a Result of Simulated Laundering Conditions. Study Number: 

110112.0001 Revision 2 (MRID 49045301) 

IV. Hazard Characterization of Nanosilver 

Nanosilver is a broad-spectrum antimicrobial agent that works by releasing ionic silver, but also 

exhibits particle-specific effects (Wang et al. 2013). In November 2009 EPA convened a meeting 

of the FIFRA Scientific Advisory Panel (SAP) to address a number of questions associated with 

assessing the hazard of and exposure to nanosilver and other nanoscale metal-based pesticides 

(FIFRA SAP, 2009). In general, the SAP advised that the toxicity of nanosilver could differ from 

and might be higher than other forms of silver (e.g., silver ions). The Panel agreed with EPA that 

particle size has a substantial impact on particle properties, including rate and concentration of 

silver ion release, where the effects of size are generally most observable for particles with 

dimensions below 20 nm and largely below 10 nm (FIFRA SAP 2009, p. 6). In addition to size, 
6 

other properties such as shape, charge, and surface coating have the potential to impact the 

biological response to nanosilver. 

4.1 Acute Human Toxicology of NSPW-L30SS 

Nanosilva LLC submitted results from guideline acute animal-toxicity tests completed using highlevel doses of a liquid suspension containing NSPW-L30SS with 1% nanosilver by weight. As 

outlined in Table 2, there were no mortalities or abnormalities noted in test animals after 

administration of NSPW-L30SS by oral, dermal, or inhalation routes at dose levels of up to 5,000 

mg/kg and 2.05 mg/L, respectively; NSPW-L30SS 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. According 

to EPA’s Toxicity Category system, which is used for product labeling purposes, shipping 

containers filled with NSPW-L30SS are required to carry a label stating “CAUTION” where 

contact with eyes or clothing should be avoided. 

Table 2 – Acute Toxicity Profile for the NSPW-L30SS Liquid Suspension 

Study Result Toxicity 

Category 

Acute Oral Toxicity No mortality or abnormalities after dose of 5,000 mg/kg IV 

Acute Dermal Toxicity No mortality or abnormalities after dose of 5,000 mg/kg IV 

Acute Inhalation Toxicity No mortality or abnormalities after dose of 2.05 mg/L IV 

Acute Eye Irritation Moderate to not irritating after dose of 0.1 mL III 

Acute Dermal Irritation Mild or slight irritation after dose of 0.5 mL IV 

Skin Sensitization Not a sensitizer N/A 

4.2 Subchronic and Chronic Toxicological Studies Available for Nanosilver 

There are no repeated-dose subchronic or chronic toxicity studies available for NSPW-L30SS or 

the nanosilver in NSPW-L30SS. However, there are repeated-dose toxicity studies available in the 

scientific literature for nanosilver. Since nanosilver might be released from NSPW-L30SS and 

articles incorporating NSPW-L30SS, EPA considers the scientific literature studies on nanosilver 

toxicity relevant. EPA believes the studies described in the following sections are sufficient for 

assessing the risks from the use of NSPW-L30SS during generation of the requisite data. 

4.2.1 Oral 

There are currently three studies in the scientific literature that investigate the oral toxicity of 

nanosilver in rats and two studies completed with mice. The first study reported findings after 28 

days of repeated gavage administration of carboxymethyl cellulose-coated nanosilver with average 

diameter of 60 nm (minimum diameter of 53 nm and maximum diameter of 71 nm) to four-week 

old male and female Sprague-Dawley rats (n = 10 per dose) (Kim, et al, 2008). There were liver 

effects (dilation of the central vein, bile-duct hyperplasia and increased foci), a coagulative effect 

on peripheral blood, and an increase in serum alkaline phosphatase (ALP) and cholesterol. There 

was a dose-dependent increase in silver distribution in many tissues (liver, kidneys, stomach, 

brain, lungs, testes, and blood) and a two-fold higher accumulation of silver in the kidneys of 

female rats when compared with male rats was also reported for all dose groups. A no observed 

adverse effect level (NOAEL) of 30 mg/kg/day (lowest dose level) was reported based on the 

observed liver effects and increase in ALP and cholesterol at 300 mg/kg/day (mid dose level). 

The second study was performed by the same group using four-week old Fisher rats (n= 10 per 

dose) for 90 days (Kim et al., 2010). This study involved repeated gavage administration of 
7 

carboxymethyl cellulose-coated nanosilver with average diameter of 56 nm (minimum diameter of 

25 nm and maximum diameter of 125 nm) to rats and reported similar findings as the 28-day study 

including gender-related distribution of silver in the kidneys and a reported NOAEL of 30 

mg/kg/day. However, intestinal pigmentation from exposure to nanosilver was reported, which 

was not observed in the 28-day study (Kim et al. 2008). 

The third study involved feeding nanosilver (14 nm average diameter) stabilized with PVP or 

silver acetate to four-week old male (n= 6 per dose) and female (n=10 per dose) Wistar Hannover 

Galas rats for 28 days (Hadrup et al. 2012a). They also reported no observed effects on the 

microbiological status of the rat’s gastrointestinal tract following ingestion of nanosilver. 

However, Hadrup et al., (2012a) did report effects for silver acetate at a dose of 14 mg/kg/day 

including an increase in ALP, decrease in plasma urea, and lower thymus weights. Hadrup et al. 

(2012b) compared the neurotoxic effects of PVP-stabilized nanosilver (average diameter of 14 nm) 

and silver acetate, both, in vivo and in vitro. Following 28 days of oral administration, nanosilver 

(4.5 and 9 mg/kg/day) and silver acetate (9 mg/kg/day) significantly increased the concentration of 

dopamine in the brains of Wistar female rats, while the brain concentration of 5-

hydroxytryptamine (5-HT) was increased only by nanosilver at a dose of 9 mg/kg/day. The 

NOAEL for this study was 9 mg/kg/day, but as this was the top dose tested, no LOAEL could be 

established. However, in the 14-day range-finding component of the studies, the brain dopamine 

concentration decreased in rats treated with nanosilver at doses of 2.25 and 4.5 mg/kg/day. In the 

in vitro experiment, three solutions consisting of 1) nanosilver, 2) an ionic silver solution obtained 

by filtering a nanosilver suspension, and 3) silver acetate were tested in neuronal-like PC12 cells. 

Nanosilver did not induce necrosis; however, cell viability was decreased and apoptosis (involving 

both the mitochondrial and the death receptor pathways) was found with all three solutions with 

the silver acetate being most potent. 

There is one study of repeated administration of nanosilver with average diameter of 42 nm 

(minimum diameter of 25 nm and maximum diameter of 55 nm) to mice for 28 days (Park, et al., 

2010). The study reported that, after oral administration of nanosilver at the dose levels of 0.25 

mg/kg/day, 0.5 mg/kg/day, or 1.0 mg/kg/day, the serum enzyme levels of ALP and aspartate 

transaminase (AST) were significantly elevated in both male and female mice in the high dose 

group. The level of alanine transaminase (ALT) was also elevated in the high dose females. 

Histopathological analysis was performed in the high-dose groups and revealed that tissue change 

(i.e., slight cell infiltration) was observed in the cortex of the kidneys in both male and female 

mice, but no other histopathological changes were found in the portions of liver or small intestines 

that were examined. A NOAEL of 0.5 mg/kg/day was initially reported, based on the observed 

findings of elevated ALP, AST and ALT and the histopathological changes in the kidneys at the 

1.0 mg/kg/day dose level. However, EPA reviewed this study again as part of this assessment and 

now concludes that although the results of the Park et al. (2010) study showed evidence of changes 

in clinical chemistry, it lacks histological support for the effects used as the basis for the study 

NOAEL/LOAELs. In the absence of histopathological findings, the clinical chemistry changes 

observed alone are insufficient evidence of an adverse effect. The updated NOAEL is 1.0 

mg/kg/day, the highest dose tested. 

Liu et al. (2013) reported that nanosilver did not affect spatial cognition or hippocampal 

neurogenesis in adult male ICR mice (n=15 per dose, n=10 for control). Adult mice were 

administered nanosilver with average diameter of 51.4 nm by Dynamic Light Scattering (DLS) 

and 26.3 nm (size range from 10 to 70 nm) by Transmission Electron Microscopy (TEM) via 

intraperitoneal injection, at doses of 0, 10, 25, or 50 mg/kg, once a day in the morning for 7 

consecutive days. Another group of mice received scopolamine (3mg/kg) as a positive control for 
8 

the behavioral studies. Investigators used the Morris water maze (MWM) test to evaluate spatial 

cognition and bromodeoxyuridine for detecting proliferating cells to measure neurogenesis. The 

test results showed that both reference memory and working memory were not impaired in 

nanosilver exposed groups, compared with the control group, and no differences were revealed in 

hippocampal progenitor proliferation, new born cell survival, or differentiation in nanosilver 

treatment groups, indicating that neurogenesis was also unaffected. 

4.2.2 Inhalation 

The subchronic inhalation toxicity of nanosilver was evaluated in six-week old male and female 

Sprague-Dawley rats (n=10 per dose) exposed to nanosilver with average diameters between 18 to 

19 nm (minimum diameter of 2 nm and maximum diameter of 65 nm) in a whole body inhalation 

chamber for 13 weeks (90-day) using OECD test guideline 413 (Sung et al., 2009). Male and 

female rats exposed to the high-dose level of 515 μg/m3

 (3.03×106 particles/cm3) showed toxic 

effects in the liver (bile-duct hyperplasia) and lungs (chronic alveolar inflammation and 

macrophage accumulation in both males and females, and erythrocyte aggregation). A follow-on 

study was performed to determine lung-function recovery of five-week old male and female 

Sprague-Dawley rats (n= 17 male and 12 female per dose) after exposure to nanosilver with 

average diameters between 14 to 15 nm (minimum diameter of 4 nm and maximum diameter of 47 

nm) in a whole body inhalation chamber for 12 weeks, followed by a 12-week recovery period 

(Song et al., 2012). The pathological findings in the lungs were very similar to those observed in 

Sung et al. (2009) even though there were slight differences in particle size and concentration. 

During the 12-week exposure period, there was a decrease in lung function of male animals 

exposed to all doses of nanosilver, including a decrease in tidal and minute volume, and peak 

expiratory flow. After the 12-week recovery period, the male rats in the mid- (117 μg/m3 or 

1.41×106 particles/cm3) and high-dose (381 μg/m3 or 3.24×106 particles/cm3) groups did not 

achieve complete recovery of lung function. Remarkably, no adverse lung function effects were 

observed for female rats. The decrease in lung function was accompanied by histopathological 

observations of perivascular mixed cell infiltrate and chronic alveolar inflammation in male 

animals, but these effects were also observed in females even though they had no measurable 

decrease in lung function. Although female rats showed gradual clearance of silver from lung 

tissues and decreased inflammation after 12 weeks of recovery, persistent inflammation in lung 

tissues was still observed in the high-dose male rats throughout the 12-week recovery period. This 

lack of recovery indicates permanent or persistent organ damage. Significant increases in the 

amount of silver in tissues, such as lungs, liver, olfactory bulb, brain, kidneys, and blood, were 

also reported. Females had two to three times more silver accumulation in their kidneys than 

males. 

Liu et al. (2012) investigated the effects of nanosilver on hippocampal synaptic plasticity and 

spatial cognition in adult male Wistar rats (n=8 per dose). Uncoated nanosilver with average 

diameter of 244.5 nm (size range from 33 to 380 nm) by DLS and with sizes ranging from 50 to 

100 nm by TEM was administered to rats by nasal drops at doses of 3 mg/kg and 30 mg/kg once 

every two days for 14 days. Spatial cognition as determined by the Morris water maze (MWM) 

test showed that animals receiving nanosilver exhibited lower learning ability and memory 

retention, which was more prominent in the high-dose group (30 mg/kg). This finding was also 

supported by impaired synaptic plasticity as determined by long-term potentiation (LTP) 

recordings for these same animals. In addition, the quantity of reactive oxygen species (ROS) in 

hippocampal homogenate was significantly increased in nanosilver- treated groups, and edema, 

nuclear shrinking phenomenon, and necrobiosis were shown in hematoxylin and eosin (HE) stains 

of pyramidal neurons in the PP (perforant path) and DG (dentate gyrus) regions of hippocampus. 
9 

4.2.3 Dermal 

There are only two dermal toxicity studies available for nanosilver. One study was performed to 

determine liver, skin and spleen pathologies of five to six week old male guinea pigs (n=6) after 

exposure to nanosilver (concentrations 100 μg/ml, 1000 μg/ml, and 10,000 μg/ml) with a particle 

size of less than 100 nm based on exposure to aqueous solution using AgNO3 as a positive control 

(Korani et al, 2011). The nanosilver suspension was applied by daily rubbing to an area of 5 cm by 

5 cm (10% surface area) on the back of the animal with no wipe off or removal of chemical 

mentioned. The applied dose in mg/kg was not determined in the study. According to email 

contact with authors, animals were restrained for 5 hours after application of the solution; 

however, the method of restraint was not discussed. During the 13 week study, dose dependent and 

nanosilver specific effects were seen in the liver, the spleen and on the skin. Skin effects included 

decreased thickness of the epidermis and dermis, inflammation, increased levels of round cells, 

acidophilic cytoplasm in muscle fibers and increased levels of macrophages in the endomysium. 

Liver effects included overproduction of Kupffer cells and degeneration of hepatocytes in a dose 

dependent fashion and necrosis at the 10,000 μg/ml concentration. Other dose-dependent effects 

observed in the liver included the following: thinner red capsules, inflammation, accumulation of 

red blood cells, and white pulp atrophy along with hepatic cord destruction. It does not appear that 

gauze or another dressing was used to cover the dosed area. No hematology, clinical chemistry or 

urinalysis was performed. Only the liver, spleen and skin were examined histopathologically. 

Another study was performed to determine the effect of skin exposure to nanosilver (size = 20 and 

50 nm, concentration = 0.34, 3.4 and 34 μg/ml aqueous solution) in 2 female pigs (Samberg et al, 

2010). A 500 μL nanosilver suspension was placed on one of 14 spots on the back of a hairclipped pig, allowed to air dry, then covered with a Hilltop chamber (occlusion pad) and secured 

with non-irritating tape. This was followed by a body stocking covering the dorsum of each pig. 

Actual exposure was 0.6, 6, and 60 ng/mm2

 and total exposure was 0.17, 1.7 and 17 μg per dosing 

period. No gross pathological effects were noticed on the porcine skin. A concentration, but not 

particle size or washing state, dependent effect was seen on the dermal layers under microscopic 

investigation. Low dose effects were slight intra and intercellular epidermal edema. Intermediate 

effects were a more focal intra and intercellular epidermal edema alongside focal dermal and 

epidermal inflammation. The highest dose caused severe edema, with severe focal dermal 

inflammation, epidermal hyperplasia and parakeratosis. Precautions were taken to prevent oral 

dosing, including restraint/anesthesia and multiple covering layers. Only effects relating to the skin 

were examined. 

None of the above studies are an acceptable substitute for a dermal subchronic study or a dermal 

irritation study. In no case was a full gross or microscopic histopathology panel performed, even in 

the cases where dose dependent effects of nano-silver particles were seen. None of these studies 

used the same size particles, coating type or washing state, making it potentially difficult to 

generalize information from them onto other products. In Korani et al. (2011), the study lacked 

any clinical chemistry, hematology or urinalysis of the guinea pigs. This study also could not draw 

NOAEL/LOAEL conclusions given that effects were seen at all levels of dosing. In Samberg et al. 

(2010), no systemic histopathological evaluations were possible as multiple dose concentrations 

were tested on the same animal. 

However, there is one published report on nanosilver that is available for use by EPA concerning 

nanosilver used in wound dressings for patients suffering from burns. In this report, a burn patient 

using a nanosilver-coated wound dressing developed clinical signs of argyria and elevated serum 

liver enzymes indicative of liver toxicity along with elevated silver concentrations in blood and 
10 

urine (Trop, 2006). This study indicates to EPA that nanosilver can be systemically absorbed when 

a large area of the skin barrier is severely compromised. 

In the absence of any dermal toxicity studies, EPA normally uses extrapolation from another route 

of exposure (usually oral). However, use of the oral endpoint for evaluating dermal toxicity 

requires knowledge regarding the amount absorbed through the skin. This information is typically 

provided by a dermal penetration study using whole animals (usually rats), which allows 

determination of the fraction of topically applied dose that is available for systemic absorption 

(i.e., the dermal absorption factor or DAF). There are in vitro techniques available that enable 

determination of dermal penetration of chemicals through isolated animal or human skin. 

However, EPA does not rely on in vitro dermal absorption study data as the sole basis for deriving 

a DAF because standardized in vitro test methodology is not currently available. Without detailed, 

standardized methodology for in vitro absorption studies, EPA has observed variation in test 

results among laboratories. As a result, EPA assumes a default DAF of 100% when no in vivo data 

are available. Therefore, if in vivo dermal penetration studies are available, either those studies 

alone or in combination with in vitro studies are used for deriving a DAF of less than 100%. 

Currently, there is no guideline or scientific literature study conducted in animals for the in vivo

dermal absorption of the nanosilver in NSPW-L30SS or of nanosilver available to EPA. However, 

there is a human clinical study, which is observational, that examined silver levels in serum and 

urine after application of burn wound cream containing silver sulfadiazine nanosilver (Wan et al., 

1991). EPA used this information to derive a conservative DAF of 6.7% for nanosilver. A study 

completed by Brandt et al. (2012) demonstrated that nanosilver and silver sulfadiazine have 

similar skin absorption characteristics in mice after normalizing for silver dose. In addition an in 

vitro study with nanosilver in human skin is available in the scientific literature. This study 

demonstrated that nanosilver penetration is very low for both intact and abraded skin at 0.00066% 

and 0.0033%, respectively (Larese et al., 2009). 

4.2.4 Reproductive and Developmental Toxicity of Nanosilver 

There are studies showing dose-dependent increases in the concentration of silver in the testes of 

rats after oral ingestion, inhalation, and injection of nanosilver (see Section 4.3); however, there 

are few studies available on the reproductive and developmental toxicity of nanosilver. 

There is an in vitro study investigating the toxicity of 15 nm nanosilver on spermatogonia isolated 

from 6-day old mouse testes and immortalized with SV40 large T antigen (Braydich-Stolle et al., 

2005). In this transformed (i.e., immortalized) cell line, both nanosilver and silver ions 

individually caused altered cellular morphology, decreased mitochondrial activity (as indicated by 

MTS cell viability assay), and increased apoptosis at doses up to 10 μg/ml; however, the effects 

from nanosilver were greater than observed for silver ions. The conservative interpretation of these 

data is that nanosilver that reaches the testes may be able to cause decreased fertility due to 

toxicity to spermatogonia and this effect would be more severe for nanosilver than for silver ion. 

In another study, Austin et al. (2012) investigated the distribution of citrate-coated nanosilver with 

diameters between 30 and 60 nm and silver nitrate in pregnant mice (n= 6 to 12 per dose) and 

developing embryos. Nanosilver suspensions and silver nitrate were administered by intravenous 

injection (i.v.) on gestation days (GD) 7, 8, and 9 at nanosilver concentrations of 0, 0.4, and 0.73 

mg/kg/day. Austin et al. (2012) reported a significant increase in nanosilver content as compared 

to silver nitrate treated animals in nearly all tissues; nanosilver accumulation was significantly 

higher in liver, spleen, lung, tail (injection site), visceral yolk sac, placenta and endometrium. This 

study did not find significantly higher nanosilver in the ovary. Nanosilver was identified in 
11 

vesicles in endodermal cells of the visceral yolk sac. This study demonstrated that nanosilver 

distributed to major maternal organs and extra-embryonic tissues, but the authors stated that very 

little silver reached developing embryos and no adverse morphological effects on the developing 

embryos were observed. 

In a 14-day repeated maternal dose study (Yu et al. 2013), nanosilver (7.5 nm) was administered 

via gavage to 11 pregnant Sprague-Dawley rats per dose from days 6 to 19 of gestation. No gross 

pathological effects or other developmental effects on the fetus were observed up to the maximum 

dose of 1000 mg/kg/day. There were no effects on maternal food consumption or body weight but 

there were some slight changes in liver catalase and glutathione reductase levels (all dose levels) 

and a decrease in glutathione at the maximum dose. No effects were seen in any organs, including 

the ovaries. The teratogenicity potential of nanosilver in pregnant rats was investigated by 

Mahabady et al. (2012). Nanosilver of unknown size and surface coating was administered to 

pregnant rats via intraperitoneal injection (i.p.) on GD 8 and 9. Fetuses collected on GD 20 from 

animals that received nanosilver were reported to have reduced weight and length but there were 

no effects on the skeletal system as compared to animals treated with a saline control. Because 

Mahabady et al. (2012) did not report key information about the nanosilver particles size and 

surface coatings, it is not possible to compare these results to the nanosilver in any other study or 

in any nanosilver-containing product. 

4.2.5 Mutagenicity of Nanosilver 

Currently, there are no studies in the scientific literature that investigate the potential of nanosilver 

to cause cancer (i.e., carcinogenicity). The exposures from this chemical are not expected to be 

long term. However, the potential of nanosilver to induce changes in genetic material (i.e., 

mutagenicity, genotoxicity) has been investigated with equivocal results in vitro, using traditional 

mutagenicity tests including the bacterial reverse mutation assay (i.e., Ames test), the mouse 

lymphoma forward mutation test, the mammalian cell chromosome aberration test in Chinese 

hamster ovary cells, and the mouse lymphoma Comet assay for oxidative damage. These in vitro

studies are equivocal as to the cytotoxicity and genotoxicity of nanosilver. Additionally, nanosilver 

was investigated in a series of in vivo studies. Results from these assays are summarized below. 

In vitro reverse gene mutation assay in bacterial cells: The mutagenicity of nanosilver (average 

diameter of 10 nm) suspended in a 1% citric acid solution was determined at concentrations of up 

to 500 μg/plate in bacterial cells using the Ames test (Kim et al., 2012). Although cytotoxicity was 

observed at 31.25 μg/plate, nanosilver did not induce a mutagenic effect in the histidine-requiring 

strains of Salmonella typhimurium TA98, TA100, TA1538 and TA1537 or in tryptophan-requiring 

Escherichia coli WP2uvrA with or without the metabolic activation system (±S9). A similar result 

was obtained by Li et al.(2012) for nanosilver with an average diameter of 5 nm (size range from 4 

to 12 nm) prepared in TEM for the primary particles and for particles with a diameter of 1608.7 ± 

175.4 nm, prepared in culture media. In this test, there was no increase in revertant mutant 

colonies of the standard S. typhimurium tester strains, which included the strain used to detect 

oxidative damage (TA102) up to cytotoxic concentration (31.25-62.5 μg/plate -S9; 125-250 

μg/plate +S9). However, Li et al. (2012) cautioned that because of cytotoxicity and the physical 

properties of nanosilver, this test system may lack the sensitivity required to detect the mutagenic 

action of the test material. 

In vitro forward gene mutation assay in mouse lymphoma L5178Y/TK+/- cells with a Comet 

Assay: The mutagenicity of nanosilver, which had an average diameter of 5 nm (size range from 4 

to 12 nm) prepared in TEM for the primary particles and a diameter of 1608.7 ± 175.4 nm in the 

culture media, was evaluated in mouse lymphoma L5178Y at the TK+/- locus and the modes of 
12 

action was assessed using standard alkaline and enzyme-modified Comet assays with a gene 

expression analysis (Mei et al., 2012). Nanosilver induced dose-dependent cytotoxicity and 

mutagenicity with a marked increase in the mutation frequency at 4 and 5 μg/mL (<50% cell 

survival at ≥5 μg/mL) where nanosilver had a clastogenic mode of action. Subsequent testing 

revealed no evidence of DNA damage (Comet test), but oxidative damage (modified Comet test), 

confirmed by gene expression analysis, which showed an expression pattern consistent with 

production of reactive oxygen species (ROS). 

In Vitro Chromosome Aberration Test: The clastogenic effect of nanosilver (average diameter of 

10 nm) suspended in a 1% citric acid at concentrations of less than 31.25 μg/mL was determined 

in Chinese hamster ovary cells (CHO-k1) after 6- and 24-hour exposures ±S9 using OECD Test 

Guideline 473 (Kim et al. 2012). Nanosilver did not induce any statistically significant increase in 

the number of cells with chromosome aberrations, polyploidy, or endoreduplication when 

compared with the control group at concentrations causing approximately 50% cytotoxicity. 

In Vitro Mammalian Cell Assays: An in vitro mammalian cell micronucleus test (OECD Test 

Guideline 487) was used to determine the genotoxicity of nanosilver, which had an average 

diameter of 5 nm (size range from 4 to 12 nm) by TEM for the primary particles and a diameter of 

1608.7±175.4 nm prepared in culture media. Nanosilver at concentrations of up to 30 μg/mL 

induced a significant and dose-related increase in micronuclei in human lymphoblastoid TK6 cells, 

indicating that nanosilver has weakly positive genotoxic potential (Li et al, 2012). 

The genotoxic effects of silver nanoparticles (43-260 nm) were further studied by Kim et al. 

(2011) on normal human bronchial epithelial (BEAS-2B) cells using the in vitro micronucleus and 

comet assays. As expected, ≈100% of the particles with diameters in the range of 40-55 nm were 

taken up by the cells; ≥50% of the particles in the range of 60 to 100 nm were found within in the 

cells and lower percents of the larger sixe particles were also deposited in the cells. Significant and 

concentration-related increases in DNA damage and micronuclei induction were found in the 

bronchial cells exposed to concentrations of 0.01 to 10 μg/mL silver nanoparticles. Significant and 

dose-related Intracellular generation of reactive oxygen species (ROS) was also demonstrated at 

0.01 to 10 μg/mL silver nanoparticles. Finally, the investigators present data indicating that the 

DNA damage induced by silver nanoparticles in BEAS-2B cells was blocked by several wellknown ROS scavengers, primarily superoxide dismutase (SOD). 

In Vivo Studies: In contrast to the above in vitro findings, the oral gavage administration of 

carboxymethyl cellulose-coated nanosilver with average diameter of 60 nm (minimum diameter of 

53 nm and maximum diameter of 71 nm) caused overt toxicity but failed to induce an increase in 

micronucleated polychromatic erythrocytes (MN PCEs) in the bone marrow of male and female 

rats after 28 days of treatment at doses 0, 30, 300, and 1,000 mg/kg/day (Kim et al, 2008). This 

study indicates that nanosilver is neither clastogenic nor aneugenic in vivo, although a limitation of 

this study is that no measurements were performed to determine if nanosilver reached the bone 

marrow. Nevertheless, subsequent studies discussed below provide confirmation that silver 

nanoparticles are readily absorbed and distributed throughout the rodent body. 

Negative results were also obtained by other researchers (Kim J S et al., 2011) using the inhalation 

route for a rat micronucleus assay. In this study, male and female rats were exposed by inhalation 

to concentrations of silver nanoparticles (18 nm) as high as 2.9 x 106

 particles/cm3 (equivalent to 

≈1000 mg/kg/day), 6 hours/day for 90 days. Although silver nanoparticles were not toxic to the 

animals or cytotoxic to the target tissue (bone marrow cells), a dose-dependent deposition of 

AgNPs was found in the blood, stomach, brain, liver, kidney, lungs, and testes of the treated rats. 
13 

In a series of in vivo studies, Li et al. (2013) found that various types of silver nanoparticles 

ranging in size from 5 to 15 - 100 nm (coated with either PVP or silicone), were neither 

clastogenic, aneugenic nor mutagenic in the mouse bone marrow micronucleus or Pig-a gene

mutation assays. Tissue distribution was confirmed at the highest dose tested (25 mg/kg), 

following intravenous injection once or daily for 3 days. At 25 mg/kg, PVP-coated silver 

nanoparticles caused significant, ≈30% reductions in the percentage of reticulocytes. By contrast, 

no cytotoxicity occurred after treatment with silicon-coated Ag particles. Thus, there is compelling 

evidence that PVP-coated silver nanoparticles reached the target tissue but did not induce a 

mutagenic response in mouse bone marrow cells. 

Similar results indicate that PVP- or silicone-coated 25 mg/kg silver nanoparticles reached the 

target organ but were not genotoxic. However, both PVP- and silicone-coated 25 mg/kg silver 

nanoparticles induced significant oxidative damage in the mouse liver, manifested as binding to 8-

oxoguanine adducts in the modified Comet assay. 

In another in vivo test, Cho et al., (2013) exposed male rats to concentrations of silver 

nanoparticles (14-15 nm) ranging from 0.66 x 106

 particles/cm3 (≈49 μg/m3) to 3.24 x 106

particles/cm3

 (≈381 μg/m3) 6 hours/ay for 12 weeks. Lung cells were harvested and DNA damage 

was assessed using the Comet assay. No significant changes in body weight or lung weight were 

observed. Histopathological examination of the lungs revealed an increased incidence of 

perivascular and chronic inflammation, accompanied by alveolaritis, granulomatous lesions and 

alveolar wall thickening and macrophage accumulation. This inflammatory response paralleled a 

significant and dose-dependent increase in silver nanoparticles and DNA damage in lung tissue. 

The genotoxic effect at the high dose was significant and ≈2X higher than effects seen in the 

control. 

In summary, the data from the in vitro studies (i.e., Ames bacterial gene mutation and mammalian 

cell mutation and chromosome aberration assays) indicate that nanosilver is not expected to be 

mutagenic in bacteria. In mammalian cells, however, the in vitro micronucleus test and the mouse 

lymphoma comet assay suggest that nanosilver may have mutagenic potential. This is consistent 

with a recent review article which stated that in vitro data point to possible mutagenic properties of 

nanosilver (Bartłomiejczyk et al., 2013). However, the lack of mutagenicity in several wellconducted in vivo studies, showing cytotoxicity and evidence that the nanoparticles reached the 

target tissue, suggests that the in vitro mutagenic potential observed in some of the in vitro studies 

may be intrinsic to nanoparticles, but is not expressed in whole animals. There is evidence that 

silver nanoparticles are genotoxic, expressing DNA damage in cultured human lung cells and in 

the lungs and liver of intact animals (comet assay) via intracellular generation of ROS. These 

findings are supported by the inflammatory processes described above in lungs. However, since 

initiation of ROS-induced oxidative DNA damage can be blocked by ROS scavengers, there is not 

a concern for mutagenicity or genotoxicity. 

4.2.6 Silver Ions 

Humans may also be exposed to silver ions that would be released by NSPW-L30SS. 

Conventional silver, and the silver ions it releases, can qualify as pesticides under FIFRA when 

used for pesticidal purposes. The SAP concluded that the hazards of silver ions would be the same, 

whether they came from conventional silver or from silver nanoparticles. With respect to silver 

ions, EPA evaluated the toxicity and exposure to silver ions and determined that unreasonable 

adverse effects from use of silver-containing products are unlikely (U.S. EPA, 1993). EPA 

reviewed a recent unpublished FDA study (DP# 427190) and determined that it did not change the 

conclusions of the Silver risk assessment. 
14 

4.3 Absorption, Distribution, Metabolism, and Excretion (ADME) of Nanosilver 

Studies were completed using either injection or oral administration of nanosilver to laboratory 

animals to determine the absorption, distribution, metabolism, and excretion (ADME) of 

nanosilver in whole animals. Based on the studies described in the following sections EPA 

believes biliary or fecal excretion of nanosilver is the primary elimination pathway. Silver is found 

primarily in the liver, spleen, and kidneys, but also in the thymus, brain, heart, lungs and testes of 

animals dosed with nanosilver, silver nitrate, and silver acetate, where the organs of animals dosed 

with silver nitrate and silver acetate contained greater amounts of silver than did animals dosed 

with nanosilver. Animals can clear silver from blood and most organs given enough time but retain 

silver in the testes and brain. Animals treated with silver nitrate, silver acetate, and nanosilver all 

contain silver granules with dimensions on the nanoscale. However, it is unclear if intact 

nanosilver is absorbed into tissues or if nanosilver dissolves into ionic silver before being absorbed 

into tissues and forming nanoscale granules. 

4.3.1 Injection of Nanosilver 

The translocation, distribution and accumulation of silver after a single subcutaneous injection at 

62.8 mg/kg of body weight of nanosilver with diameters between 50 and 100 nm and microsilver 

with diameters between 2,000 and 20,000 nm was determined in Wistar female rats (n = 30 per 

group) (Tang et al, 2009). The silver content of feces between 2 and 24 weeks after injection was 

significantly higher than in urine for both the nanosilver and microsilver-injected animals, which 

suggests that both nanosilver and microsilver are eliminated through biliary excretion. Although 

there was no significant difference between the amount of silver at the injection site or in 

excrements after administration of nanosilver or microsilver, the amount of silver in organs was 

significantly greater for nanosilver. Animals injected with nanosilver were found to contain 

significantly more silver in the liver, kidney, spleen, brain, lung and blood than in animals injected 

with microsilver. Histopathological observations found that nanosilver-injected animals contained 

elemental silver spheres that were absent from the microsilver-treated animals. The elemental 

silver spheres were observed in different kinds of cells, such as renal tubular epithelial cells and 

hepatic cells. Moreover, these elemental silver spheres also induced blood-brain barrier (BBB) 

destruction and astrocyte swelling, and caused neuronal degeneration. 

The serum kinetics, tissue distribution, and excretion of silver after single injections of 0.5 mg/kg 

and 5 mg/kg of citrate-coated nanosilver with average diameter of 7.9±0.95 nm was determined in 

SPF New Zealand White rabbits (n = 4) (Lee et al, 2012). There was no significant general toxicity 

reported in either the 0.5 or 5 mg/kg treatment groups. Accumulation of silver was observed in all 

the tested organs including liver, kidney, spleen, lung, brain, testes, and thymus, where the liver 

and spleen contained the greatest amount of silver. As with the rat study above, the amount of 

silver in feces between 1 and 28 days after injection was significantly greater than in urine, which 

suggests biliary excretion of silver is the major route of elimination after injection of nanosilver. 

Blood kinetics, tissue distribution, and organ accumulation of silver were determined after daily 

intravenous injections for 5 consecutive days of between 23.8 and 27.6 mg/L of nanosilver with 

average diameters of 20, 80, and 110 nm in six-week old male Wistar rats (n=21 in treatment 

groups; n= 2 in control) (Lankveld et al., 2010). The concentration of silver in blood rapidly 

decreased during the initial 10 minutes following both single and repeated injection of nanosilver 

and then remained stable for up to one hour after injection. Silver was distributed to all organs 

evaluated, including the liver, lungs, spleen, brain, heart, kidneys and testes, regardless of the size 

of nanosilver injected. After injecting 20 nm diameter nanosilver, silver was found to be 

distributed mainly to the liver, followed by the kidneys and spleen, whereas after injection of the 
15 

80 and 110 nm diameter nanosilver, silver was distributed mainly to the spleen, followed by the 

liver and lung. Thus, there was a size-dependent tissue distribution. Repeated administration of 

nanosilver resulted in accumulation of silver in the liver, lung and spleen, indicating that these 

organs may be potential target organs for toxicity after repeated exposure. 

4.3.2 Oral Administration of Nanosilver 

The organ distribution and cellular localization of silver was determined following 28-day 

repeated oral administration at 9.0 mg/kg/day of PVP-stabilized nanosilver with average diameter 

of 14 ± 4 nm and silver acetate to four week old female Wistar Hannover Galas rats (n = 9 for 

nanosilver and n = 7 for silver acetate) (Loeschner et al., 2011). Although the distribution of silver 

in organs for animals treated with nanosilver and silver acetate was similar, the concentration of 

silver in the organs treated with silver acetate was greater than it was for nanosilver-treated 

animals. This was in agreement with the higher fecal excretion of nanosilver as compared to silver 

acetate. Besides the intestinal system, the largest silver concentrations were detected in the liver 

and kidneys; however, silver was also found in the lungs and brain. Remarkably, silver-containing 

granules in the same size range as that of the administered nanosilver were observed in the ileum 

and kidney tissues of rats exposed to nanosilver and silver acetate. Using transmission electron 

microscopy (TEM), sulfur and selenium containing granules were detected in the ileum of animals 

exposed to nanosilver and silver acetate, and were mainly located in the basal lamina of the ileal 

epithelium and in lysosomes of macrophages within the lamina propria. The results of the present 

study demonstrate that the organ distribution and form of silver was similar when nanosilver or 

silver acetate were administered orally to rats. 

The toxicokinetics and tissue distribution of silver was determined following 28-day oral gavage at 

90 mg/kg/day of nanosilver with average diameter of 17.7±3.3 nm by TEM, PVP-coated 

nanosilver with average diameter of 12.1±8.0 nm by TEM, and 9 mg/kg/day of silver nitrate to 

six-week-old male pathogen free Sprague-Dawley rats (n = 5 per group) (Van der Zande et al., 

2012). Greater than 99% of the silver administered to the rats was excreted in their feces indicating 

that only a small fraction (<1%) of silver from nanosilver and silver nitrate was absorbed. After 

normalizing for gavage dose, the concentration of silver in the blood of the silver nitrate treated 

animals was significantly higher than for the nanosilver-treated animals at all timepoints during 

exposure. This clearly illustrates a much higher uptake of silver when silver nitrate was 

administered as compared to nanosilver. One day after the oral gavage, a significant reduction in 

blood silver concentration was observed. One week after the oral gavage, the concentration of 

silver in blood was reduced to nondetectable levels indicating rapid clearance of silver from the 

blood for both nanosilver and silver nitrate treated animals. After normalizing for gavage dose, 

silver was observed in all examined organs with the highest levels in the liver and spleen where 

animals treated with silver nitrate had accumulated significantly more silver than in animals 

treated with nanosilver. Silver was cleared from most organs eight weeks after the final gavage, 

but remarkably not from the brain and testes, where between 94 and 100% of the silver was still 

present in the brain compared to the amount one day after the last gavage of nanosilver and silver 

nitrate, respectively. Using single-particle inductively coupled plasma mass spectrometry, 

nanosilver was detected one day after the final gavage in the liver, spleen, lungs, and 

gastrointestinal contents of nanosilver gavaged rats. Nanosilver was also detected in the liver, 

spleen, lungs, and gastrointestinal contents one day after the final gavage from silver nitrate treated 

rats demonstrating the in vivo formation of nanosilver from silver nitrate. Blood enzyme levels 

were not significantly different from untreated animals indicating that there was no acute 

hepatotoxicity observed. Also, there was no indication that nanosilver caused nonspecific immune 

responses based on immunotoxic responses. 
16 

4.4 Safety Factor for Infants and Children (FQPA Safety Factor) 

Under section 408(b)(2)(C) of the Federal Food, Drug and Cosmetic Act (FFDCA) (as amended in 

1996 by the Food Quality Protection Act (FQPA), P.L. 104-170), EPA was directed to "ensure that 

there is a reasonable certainty that no harm will result to infants and children" from aggregate 

exposure to a pesticide chemical residue when establishing, modifying, leaving in effect, or 

revoking a tolerance or tolerance exemption. The law further states that for dietary exposures in 

the case of threshold effects, "an additional tenfold margin of safety for the pesticide chemical 

residue and other sources of exposure shall be applied for infants and children to take into account 

potential pre- and post-natal toxicity and completeness of the data with respect to exposure and 

toxicity to infants and children. Notwithstanding such requirement for an additional margin of 

safety, the Administrator may use a different margin of safety for the pesticide residue only if, on 

the basis of reliable data, such margin will be safe for infants and children." 

There is no food use for NSPW-L30SS at this time, and therefore, no FQPA Safety Factor and no 

FFDCA aggregate exposure analysis addressing potential NSPW-L30SS residues is required. 

4.5 Antimicrobial Resistance 

Silver is currently used as a broad-spectrum antibiotic in wound dressings. There is a concern that 

increasing use of silvers, including nanosilver used for preserving plastics, may result in more 

bacteria developing resistance to silver and will limit its use as an antibiotic agent for wound care 

(Gupta and Silver, 1998). In the wound-care setting, a recent review by Chopra (2007) concluded 

that the threat of bacterial resistance to silver in the clinical setting is low. However, Chopra 

(2007) cautioned against use of wound dressings that release sublethal levels of silver over a long 

period of time allowing bacteria to develop resistance. 

In terms of the environment, a recent study involved releasing 1 mg/L of nanosilver into 

microcosms containing estuary water overlying estuarine sediment cores (Bradford et al., 2009). 

The study found no impact to the microbial community over a 30-day monitoring period. Evidence 

for antibacterial resistance was also evaluated during this study and no increase in antibiotic 

resistance to the bacterial population in the sediment was found (Mühling et al. 2010). Wigginton 

et al. (2010) suggested that the lack of antimicrobial effect in the microcosm was expected given 

that bacterial proteins efficiently bind to nanosilver. 

EPA concludes that, while development of antibacterial resistance due to the use of nanosilver in 

NSPW-L30SS is possible, the likelihood is low that the levels used in products incorporating 

NSPW-L30SS will lead to the development of silver-resistant microbes that will spread throughout 

the environment and result in widespread bacterial resistance to silver. 

4.6 Point of Departure Selections and Target Margin of Exposure 

The currently available oral toxicity studies indicate that nanosilver causes liver and kidney 

toxicity in laboratory animals in which silver is distributed to all organs and tissues. Inhalation 

toxicity studies also identified liver toxicity as well as lung effects including alveolar 

inflammation. There were potential neurotoxic effects identified with increases in neurotransmitter 

concentrations and decrease in spatial cognitive ability; however, these same effects were not 

observed in a follow-on study. 

Together, these studies indicate to EPA that, if sufficient quantities of nanosilver break away from 

NSPW-L30SS, and if such nanosilver displays toxicity similar to the nanosilver used in the oral 

and inhalation route-specific studies, then route-specific exposure to NSPW-L30SS-derived 

nanosilver may result in adverse health effects. 
17 

4.6.1 Point of Departures for NSPW-L30SS 

The toxicological point of departure (POD) is the lower confidence bound on the lowest 

experimental dose from a dose-response study that showed an effect. This dose is determined from 

dose-response data and marks the beginning of extrapolation to determine the risk associated with 

environmentally relevant human exposures. Commonly, this is a NOAEL from a laboratory animal 

toxicity study, which represents the dose at which no adverse effects were observed in laboratory 

animals. Oral or dermal subchronic and chronic toxicology studies are not available for NSPWL30SS or the nanosilver that might break away from articles incorporating NSPW-L30SS. In place 

of these studies, EPA is determining NOAELs and LOAELs from subchronic inhalation and oral 

toxicity studies found in the scientific literature for nanosilvers to evaluate the effects that could 

occur from exposure to the nanosilver present in NSPW-L30SS. 

As stated in Section 2.2, the FIFRA SAP was unsupportive of bridging among silver-based 

materials with different properties. However, the SAP indicated that bridging would be appropriate 

for materials of similar size and essentially identical physical properties and that bridging between 

silver ions released from nanosilver and the existing database for silver ions is feasible (FIFRA 

SAP, 2009). The SAP cautioned about extrapolating from one nanosilver formulation to another 

when assessing hazards because differences in particle formulation (e.g., coating and inert 

ingredients) are likely to affect biological activity, among other things. 

The oral toxicity study by Hadrup et al. (2012a) used PVP-coated nanosilver with average 

diameter of 14 nm, which is similar to the diameter and surface coating of the nanosilver in 

NSPW-L30SS. However, EPA cannot determine a NOAEL or LOAEL from this study because 

histopathological patterns indicative of distinct adverse effects at the highest nanosilver dose of 9 

mg/kg/day were not identified. A LOAEL was not identified. The oral toxicity study by Park et al. 

(2010) used uncoated nanosilver with an average diameter of 42 nm, which is different from the 

diameter and surface coating of the nanosilver in NSPW-L30SS. In 2011, EPA used the NOAEL 

reported in the Park et al. (2010) study as the POD for evaluating the oral and dermal toxicity of 

the nanosilver in HeiQ AGS-20 (U.S. EPA, 2011a). EPA reviewed this study again as part of this 

assessment and now concludes that although the results of the Park et al. (2010) study showed 

evidence of changes in clinical chemistry, it lacks histological support for the effects used as the 

basis for the study NOAEL/LOAELs. In the absence of histopathological findings, the clinical 

chemistry changes observed alone are insufficient evidence of an adverse effect. 

The oral toxicity studies by Kim et al. (2008) and Kim et al. (2010) used CMC-coated nanosilver 

with average diameter of 56 and 60 nm, respectively, which is different from the diameter and 

surface coating of the nanosilver in NSPW-L30SS. These studies were stated as being completed 

according to OECD guidelines and identified histopathological patterns in the liver that were 

indicative of distinct adverse effects. EPA has determined that the NOAEL is 30 mg/kg/day from 

the 28-day Kim et al. (2008) study based on significant increases in ALP and cholesterol, 

significant changes in hematology, and accompanied by histopathological evidences of liver 

toxicity (bile-duct hyperplasia around central vein, infiltration of inflammatory cells, and dilation 

of the central vein) at the LOAEL dose of 300 mg/kg/day. A NOAEL for the 90-day Kim et al. 

(2010) cannot be established because of adverse histological patterns evident at the lowest dose of 

30 mg/kg/day. EPA has determined that the LOAEL from the 90-day Kim et al. (2010) study is 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. 

The inhalation toxicity studies by Sung et al. (2009) and Song et al. (2012) used uncoated 

nanosilver with average diameters of 18 to 19 nm and 14 to 15 nm, respectively, which is similar 
18 

to the diameter but different than the surface coating of the nanosilver in NSPW-L30SS. EPA has 

determined that the NOAEL is 133 μg/m3

 from the 90-day Sung et al. (2009) study based on the 

minimal bile-duct hyperplasia, perivascular mixed cell infiltrate and chronic alveolar inflammation 

and macrophage accumulation in the lungs in both male and female rats, and on decreases in 

physiological measures of lung function (respiratory minute volume, tidal volume, and peak 

inspiratory flow) in the male rats. EPA has determined that the NOAEL is 49 μg/m3

 from the 12-

week Song et al. (2012) study based on adverse histopathological patterns in lung tissue observed 

at the 117 μg/m3

 dose. In 2011, EPA used the NOAEL reported in the Sung et al. (2009) study as 

the POD for evaluating the inhalation toxicity of the nanosilver in HeiQ AGS-20 (U.S. EPA, 

2011a). EPA compared the Sung et al. (2009) study to the Song et al. (2012) study and now 

concludes that the newly available Song et al. (2012) study is more appropriate for evaluating 

inhalation exposure to nanosilver, as this study included a recovery period in addition to an 

exposure period. This recovery period indicated that some effects persisted in male rats past the 

end of the exposure period, something not studied in Sung et al. (2009). 

Based on the above analysis, EPA has determined that the NOAEL of 30 mg/kg/day from 28-day 

oral toxicity study by Kim et al. (2008) is the POD for short-term oral exposures (< 30 days) to the 

nanosilver in NSPW-L30SS (Table 3). EPA has also determined that the LOAEL of 30 mg/kg 

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 NSPW-L30SS. EPA has determined that the 

NOAEL of 49 μg/m3 derived from the Song et al. (2012) study is the POD for short- and 

intermediate-term inhalation exposures to the nanosilver in NSPW-L30SS. These studies were 

conducted using OECD guidelines, therefore they are the most robust and the effects are consistent 

across studies. The NOAELs/LOAELs from these studies are therefore protective of the types of 

effects seen in other studies. 

Table 3 – Toxicity Endpoints for Use in the Risk Assessment of NSPW-L30SS Nanosilver 

Exposure Scenario Point of Departure 

(POD) 

Uncertainty 

Factor 

Target MOE for 

Risk Assessment Study 

Incidental Oral 

(short-term) 

NOAEL = 30 

mg/kg/day 

UFA = 10 

UFH = 10 

UFD = 10 

1000 Kim et al. (2008) 

Incidental Oral 

(Intermediate-term) 

LOAEL = 30 

mg/kg/day 

UFA = 10 

UFH = 10 

UFD = 10 

UFL = 3 

3000 Kim et al. (2010) 

Dermal 

 (short -term) 

NOAEL = 30 

mg/kg/day 

DA = 6.7% 

UFA = 10 

UFH = 10 

UFD = 10 

1000 Kim et al. (2008) 

Dermal 

(Intermediate-term) 

LOAEL = 30 

mg/kg/day 

DA = 6.7% 

UFA = 10 

UFH = 10 

UFD = 10 

UFL = 3 

3000 Kim et al. (2010) 

Inhalation (short- and 

intermediate- term) NOAEL = 49 μg/m3

UFA = 10 

UFH = 10 

UFD = 10 

1000 Song et al. (2012)

Cancer (oral, dermal, 

inhalation) 

At this time there is inadequate information to assess carcinogenic potential of 

nanosilver due to differences in results between the in vitro studies and in vivo

study, and the limitations of the only available in vivo study. 
19 

There are no acceptable dermal toxicity studies on nanosilver available to EPA. In the absence of 

any such dermal toxicity studies, EPA normally uses extrapolation from another route of exposure 

(usually oral) and assumes a default dermal absorption (DA) of 100% when no in vivo data are 

available (see Section 4.2.3). The available human in vivo study indicating absorption of 

nanosilver is 6.7% and the in vitro data indicating absorption of nanosilver from intact and abraded 

human skin is substantially below 0.1% provide scientific support for setting a conservative DA of 

6.7% for the nanosilver that might break away from the NSPW-L30SS. EPA has determined that 

the dermal toxicity for the nanosilver in NSPW-L30SS will be evaluated using the oral POD of 30 

mg/kg/day and a DA of 6.7%. In 2011, EPA used a DA of 0.1% that was based on a human 

clinical study by Moiemen et al., (2011) for evaluating the dermal toxicity of the nanosilver in 

HeiQ AGS-20 (U.S. EPA, 2011a). EPA reviewed this study again as part of this assessment and 

now concludes that the 0.1% DAF was an underestimate because it was based on the Moiemen et 

al. (2011) study which only reported silver concentrations in the blood of patients. The 6.7% DA is 

based on the observational study by Wan et al. (1991) which reported silver concentration in 

serum as well as that eliminated through urine. 

The estimated DA of 6.7% is based on application of 500 mg of silver to damaged skin while 

significantly less silver and nanosilver are used to preserve materials. For example, the maximum 

dermal exposure to nanosilver from HeiQ AGS-20 treated textiles was 0.17 mg/day (EPA, 2011) 

and was 0.0165 mg/day for NSPW-L30SS-treated textile (EPA, 2013). Therefore, the 

concentration of silver in the burn wound studies were from approximately 3,000 to 30,000 times 

greater than those for materials treated with nanosilver. 

There are currently no acceptable studies on the reproductive and developmental toxicity of 

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-embryonic tissues although no 

adverse morphological effects on the developing embryos were observed. Therefore, EPA believes 

that the short-term incidental oral NOAEL and incidental-oral LOAEL of 30 mg/kg/day and 

inhalation NOAEL of 49 μg/m3

 are expected to be protective of developmental and reproductive 

effects of nanosilver. 

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. 

The study by Liu et al. (2013) reported no effects on spatial cognition or hippocampal 

neurogenesis of mice after injecting nanosilver into the body cavity (i.e., intraperitoneal injection) 

at concentrations of up to 50 mg/kg. Therefore, EPA believes that the short-term incidental oral 

NOAEL and intermediate-term LOAEL of 30 mg/kg/day are expected to be protective of 

neurotoxic effects of nanosilver. 

The effects on spatial cognition and hippocampal synaptic plasticity 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). Therefore, EPA believes that the inhalation 

NOAEL of 49 μg/m3

 based on the Song et al. (2012) study is expected to be protective of 

neurotoxic effects of nanosilver. 
20 

4.6.2 Target Margin of Exposure 

The target margin of exposure (MOE) is based on uncertainty factors. There are two standard 

uncertainty factors that account for potential interspecies extrapolation and intraspecies variation. 

The first is a 10 fold uncertainty factor (UFA) assigned to account for extrapolation of laboratory 

animal data to humans (interspecies). The second is a 10 fold uncertainty factor (UFH) assigned to 

account for variations in susceptibility within the human population (intraspecies). In addition to 

the two standard uncertainty factors given above, there is a third uncertainty factor (UFD) which 

accounts for the incomplete characterization of nanosilver toxicity (database). In this case, EPA 

has determined that the inhalation and oral toxicity data for nanosilver are sufficient to assess the 

potential health effects caused by nanosilver released from NSPW-L30SS (Table 3). However, as 

the SAP concluded, there is uncertainty on how particle parameters such as size, surface charge 

and coating affect the toxicity potential of nanosilver. In addition, the database is incomplete with 

respect to reproductive and developmental effects. Therefore, EPA is using the maximum 10 fold 

database uncertainty factor to cover the missing information on reproductive and developmental 

effects and the potential for differences between the nanosilver in the available toxicity data (U.S. 

EPA, 2002). Thus, the target MOE is: 

Target MOE: 10 (UFA) × 10 (UFH) × 10 (UFD) = 1,000 

The target MOE of 1,000 is for evaluating short-term (< 30 days) and intermediate-term (1 to 6 

months) continuous daily inhalation exposures to NSPW-L30SS because the inhalation POD was 

based on a 90-day study by Song et al. (2012). The target MOE of 1,000 is for evaluating the 

short-term exposure (< 30 days) continuous daily oral exposures to NSPW-L30SS because the oral 

POD was based on a 28-day oral toxicity study by Kim et al., 2008. 

The oral POD that was based on the LOAEL from the 90-day oral toxicity study by Kim et al. 

(2010) has an additional 3 fold uncertainty factor (UFL) to account for the lack of NOAEL. The 

target MOE for evaluating intermediate-term exposure (1 to 6 months) continuous daily oral 

exposures to NSPW-L30SS is: 

Target MOE (intermediate-term oral): 10 (UFA) × 10 (UFH) × 10 (UFD) × 3(UFL) = 3,000 

The maximum recommended long-term target MOE is 3,000 (U.S. EPA, 2002), which has already 

been established for intermediate-term exposures. 

4.6.3 Margin of Exposure 

The margin of exposure (MOE) is used to determine if exposure to a chemical can be expected to 

cause an adverse effect. The MOE is calculated by dividing the POD by the estimated daily dose 

to which humans will be exposed as expressed by the following: 

MOE = POD / Daily Dose 

After calculating a MOE from the POD and daily dose, EPA evaluates the risk from exposure to a 

pesticide by comparing the calculated MOE to a target MOE (U.S. EPA, 2002). If a calculated 

MOE is equal to or greater than a target MOE, EPA may conclude that exposure to the pesticide is 

unlikely to pose a risk concern and, therefore, will not cause unreasonable adverse effects for that 

specific exposure scenario. If a calculated MOE is less than a target MOE, then EPA may have a 

risk concern. However, the MOE analysis is not the only factor EPA uses when determining if 

there is a risk concern from exposure to a pesticide. EPA also considers other scientific evidence 

in a weight of evidence evaluation such as the severity of toxic effects, the controls used to 

minimize exposures, and the population exposed to the pesticide. A risk concern is not the 
21 

equivalent of a determination that the potential risk constitutes an unreasonable adverse effect. 

Rather, where EPA finds a risk concern, EPA will generally: (1) require protective measures or 

use restrictions to mitigate the risk; (2) further refine its risk assessment analysis, particularly if 

conservative assumptions were used to produce the initial assessment; or (3) explicitly analyze any 

potential benefits of the pesticide to determine whether, on balance, those benefits outweigh the 

identified risk. 

EPA’s MOE approach for nanosilver uses mass-based metrics, both for determining the POD and 

for calculating exposure. EPA is aware of the ongoing debate within the scientific community that 

metrics other than mass (such as particle number or surface area) may be more suitable for 

assessing nanosilver risks and therefore acknowledges the potential for limitations of mass-based 

risk estimates. 

V. Occupational and Consumer Risk Assessment 

Based on the use pattern of NSPW-L30SS in plastics and textiles, EPA anticipates humans could 

be exposed to the following substances: 

1) Silver ions released from NSPW-L30SS; 

2) NSPW-L30SS complex; and/or 

3) Nanosilver that might break away from NSPW-L30SS. 

Because the levels of silver in plastics and textiles incorporating NSPW-L30SS are lower than for 

other currently registered products which use silver ions and because EPA determined that 

unreasonable adverse effects from use of silver-containing products are unlikely (U.S. EPA, 1993), 

EPA concluded that the risk from exposure to silver ions derived from plastic and textile products 

incorporating NSPW-L30SS is not of concern. Nanosilva LLC has submitted a number of studies 

and other information to support its application for registration, including information relevant to 

assessing the toxicity of and exposure to NSPW-L30SS. In addition, EPA has also reviewed data 

and information on nanosilver from the scientific literature. This section discusses EPA’s 

assessment of the potential risks to human health from exposure to nanosilver from the use of 

NSPW-L30SS. 

5.1 Occupational Risk Assessment for Mixing and Loading the NSPW-L30SS Liquid 

Suspension 

EPA expects that occupational inhalation and dermal exposures to NSPW-L30SS, including 

nanoparticles that might break away from NSPW-L30SS, are likely to occur during the following 

use scenarios:

1. Mixing and loading of NSPW-L30SS during preparation of a master batch 

2. Mixing, loading, and applying the NSPW-L30SS containing master batch during treatment 

of plastics and textiles 

3. Handling plastics and textiles incorporating NSPW-L30SS 

EPA evaluates the risk of occupational exposures from mixing, loading, and applying or handling 

pesticide products. Although exposure to NSPW-L30SS during subsequent work activities 

involving plastics and textiles incorporating NSPW-L30SS can occur in occupational settings 

(items 2 and 3), the risk to workers for these scenarios is unlikely to exceed the risk during mixing 

and loading NSPW-L30SS during preparation of the master batch (item 1). Therefore, only the 

mixing and loading of NSPW-L30SS during preparation of a master batch is evaluated in the 

subsequent sections. 
22 

5.1.1 Occupational Exposure Preparing the Master Batch Containing NSPW-L30SS 

A master batch consists of polymer pellets (i.e., plastic pellets) containing NSPW-L30SS which 

are subsequently used in treating plastics (MRID 48652901). A master batch is prepared by 

blending a polymer and the NSPW-L30SS liquid suspension using a mixer and compounding this 

mixture using an extruder. Workers may be exposed to NSPW-L30SS and/or nanosilver particles 

that break away from NSPW-L30SS while loading the NSPW-L30SS liquid suspension into the 

master batch mixer. 

Nanosilva LLC did not submit data or information quantifying the amount of NSPW-L30SS that 

workers are exposed to during loading of the NSPW-L30SS liquid suspension into a master batch 

mixer. To calculate worker exposure, EPA is using the standard occupational handler unit 

exposure values for mixing and loading of liquids, as shown in Table 4, which are from the 

Antimicrobial Exposure Assessment Task Force II (AEATF II) liquid pour human exposure 

monitoring study (U.S. EPA, 2012a) and the Pesticide Handlers Exposure Database (PHED) (U.S. 

EPA, 1998). 

Table 4 – Unit Exposures for Mixing and Loading the NSPW-L30SS Liquid Suspension 

Mitigation LevelA Exposure 

Route Unit Exposure Data Source 

None (No respirator or Engineering Control) Inhalation 0.21 μg/m3/lb AEATF II 

Engineering Control – Closed System Loading Inhalation 0.016 μg/m3/lb PHED 

None (No gloves or engineering control) Dermal 10 mg/lbB AEATF II 

Gloves Dermal 1.2 mg/lbC AEATF II 

Engineering Control – Closed System Loading Dermal 0.0086 mg/lb PHED 

A.It is assumed that all workers will wear long pants, long sleeve shirts, shoes and socks at all mitigation levels.

B. Arithmetic mean for conventional liquid pour scenario 

C. Estimated from the no gloves unit exposure using a glove protection factor of 10. 

The inhalation unit exposure for mixing and loading of liquids using engineering controls (closed 

system loading) as listed in PHED is 0.083 mg/lb. This value was calculated based on the air 

concentrations measured in workers’ breathing zone during the handling of a pesticide, the time 

that elapsed during the sampling, an assumed breathing rate of 29 liters per minute, and the 

amount of the pesticide that was handled during the sampling period. When the PHED unit 

exposures were initially calculated, they were expressed in units of mg/lb for comparisons to 

PODs that were expressed in units of mg/kg/day. Because the POD for inhalation exposure to 

nanosilver is expressed as a daily-average air concentration of μg/m3

, the PHED unit exposure was 

converted to a daily-average air concentration with units of μg/m3 per lb of pesticide handled per 

day. This was done by dividing the air concentrations listed in the PHED by the amount of 

pesticide handled while accounting for the time elapsed during sampling and an eight hour work 

day. This yielded an inhalation unit exposure of 0.016 μg/m3

 per lb of pesticide and it represents 

an eight hour time weighted average (Table 4). This unit exposure is the arithmetic mean of 27 

PHED monitoring events (formerly called replicates) that represent inhalation exposure during the 

mixing and loading of pesticide containing liquids while using closed-system loading. 

5.1.2 Occupational Margins of Exposure 

As detailed in the following sections, EPA evaluated the risk to workers who load the NSPWL30SS liquid suspension into a master batch mixer. 
23 

Occupational Inhalation Exposure 

The inhalation exposure to the nanosilver in the NSPW-L30SS liquid suspension was calculated 

using the following: 

Inhalation Daily Exposure = Amount of nanosilver in NSPW-L30SS handled per day × 

Inhalation Unit Exposure 

Where: 

 Amount of nanosilver in NSPW-L30SS handled per day is 1.2 lb/day. This value was 

calculated assuming that the NSPW-L30SS liquid suspension was mixed into a low density 

polyethylene plastic using an extruder with the maximum screw diameter of 8 inches 

(Chanda and Roy, 2007) which yields a plastic production rate of 5,000 lb/hour (Flite 

Technology, 2012). Assuming an 8 hour work day yields a plastics production volume of 

40,000 lb per day at each treatment facility. The maximum amount of nanosilver applied to 

plastics or textiles is 0.003% by weight. Thus, the amount of nanosilver that is handled per 

day is 40,000 lb/day × 0.003% ÷ 100% = 1.2 lb/day. 

 The unit exposure for inhalation is 0.21 μg/m3

/lb when no respirator is worn and 0.016 

μg/m3/lb when closed-system loading is used (see Table 4). 

The MOEs shown in Table 5 were calculated by dividing the inhalation exposure for nanosilver by 

the POD of 49 μg/m3, which is the NOAEL from a 90-day inhalation toxicity study for nanosilver 

(Song et al., 2012). This assumes that all the nanosilver in NSPW-L30SS is freely available after 

inhalation and behaves like the nanosilver used in the Song et al. (2012) study even though the 

nanosilver in NSPW-L30SS is attached to a silica core particle through a thiolate bond. When no 

respirator is worn the MOE is 200, and is less than the target MOE of 1,000 which means that the 

risk is of concern. The MOE is 2,500 when closed-system loading is used. This MOE is greater 

than the target MOE of 1,000 which means the risks are not of concern. These MOEs indicate that 

the risk concern for inhalation exposures to the nanosilver in NSPW-L30SS is mitigated when 

workers use closed-system loading during mixing and loading of the NSPW-L30SS liquid 

suspension. 

Table 5 – Occupational Handlers Inhalation MOEs for the Nanosilver in NSPW-L30SS 

Mix/Load NSPWL30SS Liquid 

Suspension 

(i.e. Liquid Pour) 

Amount 

of 

Plastics 

Treated 

per day 

Application 

RateA 

Amount of 

Nanosilver 

Handled 

per day 

Inhalation 

Unit 

Exposure 

(μg/m3/lb) 

ExposureB

(μg/m3) MOEC,D 

Without Respirator 

40,000 lb 0.003% 

By Weight 1.2 lb 

0.21 0.25 200 

Closed System 

Loading 0.016 0.02 2,500 

A. Maximum amount of nanosilver in plastics incorporating NSPW-L30SS 

B. Daily Exposure = Amount nanosilver Handled × Unit Exposure 

C. MOE = POD / Daily Exposure 

D. Target MOE is 1000 

Occupational Dermal Exposure 

The dermal dose from exposure to the nanosilver in the NSPW-L30SS liquid suspension was 

calculated using the following: 
24 

Dermal Daily Dose = (Amount of nanosilver in NSPW-L30SS handled per day × Dermal Unit 

Exposure × Dermal Absorption) / Body Weight 

Where: 

 Amount of nanosilver in NSPW-L30SS handled per day is 1.2 lb/day (Table 5). 

 The dermal unit exposures are 10 mg/lb when no gloves are worn, 1.2 mg/lb when gloves 

are worn, and 0.0086 mg/lb when closed-system loading is used (Table 4). 

 The dermal absorption (DA) for nanosilver is 6.7 percent (see Section 4.2.3). 

 The body weight of an adult is 80 kg (U.S. EPA, 2011b). 

The MOEs shown in Table 6 were calculated by dividing the dermal dose by the POD of 30 

mg/kg/day, which is the NOAEL from a 28-day oral toxicity study (Kim et al., 2008) and the 

LOAEL from a 90-day oral toxicity study (Kim et al., 2010). This assumes that all the nanosilver 

in NSPW-L30SS is freely available after dermal contact and behaves like the nanosilver used in 

the Kim et al. (2008 and 2010) studies even though the nanosilver in NSPW-L30SS is attached to 

a silica core particle through a thiolate bond. The MOEs range from 3,000 when no gloves are 

worn to 3,500,000 when closed-system loading is used. These MOEs are well above the target 

MOEs of 1,000 and 3,000 for short and intermediate term exposures, respectively, which means 

that the risks are not of concern. 

Table 6 – Occupational Handlers Dermal MOEs for the Nanosilver in NSPW-L30SS 

Mix/Load NSPW-L30SS 

Liquid Suspension 

(i.e. Liquid Pour) 

Amount of 

Nanosilver Added 

or HandledA 

Dermal Unit 

Exposure 

(mg/lb) 

ExposureB 

(mg/day) 

DoseC 

(mg/kg/day) MOED, E

Without Gloves 

1.2 lb/day 

10 12 0.010 3,000 

With Gloves 1.2 1.4 0.0012 25,000 

Closed System Loading 0.0086 0.01 0.0000086 3,500,000

A. Based on the same assumptions as those used for the inhalation MOE (see Table 5) 

B. Dermal Exposure = Amount of nanosilver Handled × Dermal Unit Exposure 

C. Dermal Dose = (Dermal Exposure × Dermal Absorption)/ Body Weight 

D. Dermal MOE = POD / Daily Dose 

E. Target MOE is 1000 for short-term exposures and 3000 for intermediate term exposures. 

5.1.3 Conclusions for Occupational Risk 

The MOE for occupational inhalation exposure to the nanosilver in the NSPW-L30SS liquid 

suspension is 2,500 if workers use close-system loading. This MOE is greater than the target MOE 

of 1,000 which means that the risk is not of concern. The MOE for dermal exposure to the 

nanosilver in the NSPW-L30SS liquid suspension is 3,500,000 if workers use closed-system 

loading. This MOE is well above the target MOEs of 1000 and 3,000 for short and intermediate 

term exposures, respectively, which means that the risk is not of concern. EPA is requiring that 

closed-system loading as defined in 40 CFR part 170.240(d)(4) be used when mixing and loading 

the NSPW-L30SS liquid suspension to mitigate risks with inhalation exposure. The closed-system 

loading requirement is based on unit exposure data from PHED. The MOEs for handling NSPWL30SS without closed system loading were calculated using unit exposure data from AEATF II. 

EPA does not typically consider long-term occupational exposures to materials 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. 
25 

There are several uncertainties in the occupational risk assessment. The exposure analysis assumes 

that all the nanosilver in NSPW-L30SS is freely available even though the nanosilver in NSPWL30SS is attached to a silica core particle through a thiolate bond. The PODs used were based on 

inhalation and oral toxicity studies completed using nanosilver, not NSPW-L30SS or the 

nanosilver that might break away from NSPW-L30SS, and thus these PODs may not equal PODs 

determined from testing conducted with NSPW-L30SS or the nanosilver found in NSPW-L30SS. 

Because the nanosilver in the toxicity database is different from the nanosilver in NSPW-L30SS 

and because the database is incomplete with respect to reproductive and developmental effects, 

EPA used a maximum 10-fold database uncertainty factor when evaluating the risk from 

occupational exposure to NSPW-L30SS. There are also uncertainties in extrapolating from effects 

observed after feeding test-animals nanosilver (i.e., oral route) to the effects that might be 

observed after applying nanosilver to the skin of test animals (i.e., dermal route). 

5.1.4 Occupational Exposure and Health Data Requirements 

EPA is not requiring that Nanosilva LLC conduct an indoor applicator study to quantify the unit 

exposure values during mixing and loading of the NSPW-L30SS liquid suspension into the master 

batch mixer. This is because closed-system loading, such as lock and load containers, where the 

NSPW-L30SS liquid suspension is transferred to a plastic extruder through piping minimizes 

occupational exposure to NSPW-L30SS to the greatest extent possible. 

Although there is no risk concern for workers who use closed system loading when mixing and 

loading the NSPW-L30SS liquid suspension, EPA is requiring an inhalation route-specific 

subchronic test (OCSPP GLN 870.3465) to account for the lack of inhalation data on the specific 

form of nanosilver in assessing the risks to workers who mix and load NSPW-L30SS. Also, 

because workers of child bearing age could handle NSPW-L30SS during mixing and loading, EPA 

is requiring a modified reproduction/developmental toxicity screening test since data on the 

specific form of nanosilver are missing from the toxicity database. The current points of departure 

and additional 10x database uncertainty factor is sufficient and health protective until these data 

are submitted to the Agency. 

In summary, the following guideline studies are required for NSPW-L30SS: 

 90-Day Inhalation Toxicity (Rat) (OCSPP GLN 870.3465) modified to include a functional 

observational battery, motor activity and detailed neuropathology 

 Reproduction/Developmental Toxicity Screening Test via the inhalation route (Modified 

OCSPP GLN 870.3550/ OECD TG 421) 

5.2 Consumer Risk Assessment for Products Incorporating NSPW-L30SS 

EPA expects consumer exposures to NSPW-L30SS, the silver ions released from NSPW-L30SS, 

and the nanoparticles that break away from NSPW-L30SS could potentially occur during the 

following use scenarios: 

1. Incidental oral exposure to plastics and textiles incorporating NSPW-L30SS 

2. Dermal exposure to plastics and textiles incorporating NSPW-L30SS 

NSPW-L30SS is registered 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 NSPW-L30SS 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 NSPW-L30SS. 
26 

While children younger than 6 months may potentially be exposed to plastics and textiles 

incorporating NSPW-L30SS, it is believed that exposure for children older than 6 months will be 

equivalent, if not greater, due to behavioral and anatomical/physiological development; therefore, 

EPA assessed exposure to children older than 6 months. EPA recently revised its standard 

operating procedures (SOPs) for residential pesticide exposure assessments (U.S. EPA, 2012b). 

Based on the combined quantitative and qualitative analysis of the life stages, EPA has determined 

that the 1 to < 2 year-old life stage represents the most appropriate “index life stage” for children 

for most exposure scenarios. This analysis of lifestages is included in Appendix A of the SOPs 

(U.S. EPA, 2012b) and it focused on four specific child lifestages as defined the Guidance on 

Selecting Age Groups for Monitoring and Assessing Childhood Exposures for Environmental 

Contaminants (U.S. EPA, 2005). These lifestages included children 6 < 12 months old, children 1< 

2 years old, children 2 < 3 years old and children 3 < 6 years old. The quantitative life stage 

analysis, which included such as factors as body weight, exposure time and frequency of object 

and hand to mouth activities, indicated that 6 to < 12 month-old children and 1 to < 2 year-old 

children have the greatest potential for exposure. When qualitative factors are considered in 

addition to the quantitative factors; however, the 1 to < 2 year-old children are considered to be the 

most appropriate. 

In 2011, EPA evaluated the exposure to textiles containing the nanosilver based pesticide HeiQ 

AGS-20 using children in the 2 to 3 year-old life stage based on EPA’s determination, at that time, 

that the 2 to 3 year-old child was likely the most exposed population from chewing on and wearing 

textiles treated with HeiQ AGS-20 (U.S. EPA, 2011a). After issuing the registration decision for 

HeiQ AGS-20, questions were raised about the use of the 2 to 3 year-old life stage. In light of 

those questions and in light of the newly revised SOPs, in this case, EPA is evaluating exposure to 

children in the 6 to < 12 month, the 1 to < 2 year, and 2 to <3 year-old age range from plastic toys 

and flooring and textiles incorporating NSPW-L30SS for transparency. 

5.2.1 Consumer Exposures to Plastics and Textiles Incorporating NSPW-L30SS 

Leaching studies are required to determine the amount and form of silver that consumers will be 

exposed to when in contact with plastics and textiles incorporating NSPW-L30SS. These studies 

typically involve immersing products incorporating nanosilver in biological fluids such as 

simulated saliva solutions for extended periods of time at physiological temperatures (i.e., 98.6 

degrees Fahrenheit or 37 degrees Celsius) and measuring the amount and form of silver released to 

those fluids. Such “leaching studies” were submitted by Nanosilva LLC using food contact 

solutions for plastic coupons incorporating NSPW-L30SS and using laundry detergent and 

simulated saliva for shirts incorporating NSPW-L30SS. 

Plastic Coupon Leaching Study (MRID 478289-25) 

Nanosilva LLC submitted a plastics leaching study on the migration of silver in NSPW-L30SS 

from a linear low-density polyethylene (LLDPE) plastic (MRID 478289-25). The plastics leaching 

study was based on Food and Drug Administration methodology to determine the migration of 

chemicals from plastics which contact food. The plastics leaching study involved 44 LLDPE 

coupons with 14 being ashed to determine silver content and 28 used in the leaching tests. The 28 

plastic coupons were prepared with four NSPW-L30SS master batch concentrations where seven 

coupons each contained 0, 2.5, 5, and 10%, respectively. These master batch concentrations 

corresponded to nanosilver concentrations of 0, 5, 10, and 20 mg/kg (supplementary information 

provided on 17 December 2010). The coupons each had a surface area of approximately 112 cm2

, 

a volume of approximately 16.3 mL and an approximate mass of 15g. Each coupon was exposed 
27 

to 50 mL of the food simulation fluids, which included aqueous solutions of low and high pH 

fluids, 10% alcohol, 10% sodium phosphate monbasic, 10% olive oil and 10% sodium phosphate 

and sucrose at temperatures of 40 and 100 degrees Celsius for periods of up to 240 hours (10 

days). The amount of nanosilver present in the coupons was 0, 75, 150, and 300 μg, respectively. 

Given that coupons were in contact with 50 mL of fluid, the maximum silver concentrations that 

could be obtained from each coupon was 0, 1500, 3000, and 6000 μg/L, respectively. 

Since EPA is only evaluating risk from non-dietary human contact with non-food use plastics 

incorporating NSPW-L30SS, results for low and high pH fluids, which are more representative of 

biological fluids, are included in this assessment (other fluids would be used if dietary exposures 

from food use plastics were anticipated). Given that EPA is evaluating human exposure to plastics 

incorporating NSPW-L30SS which occur at physiological temperatures (i.e., 98.6 degrees 

Fahrenheit or 37 degrees Celsius), the leaching results for the trials conducted at 100 degrees 

Celsius are not addressed here. The 100 degrees Celsius conditions are more representative of 

microwaving plastics than of contact with humans. 

The concentration of silver in the low and high pH fluids contacting plastic incorporating NSPWL30SS was below the analytical LOD. The analysis method, inductively coupled plasma atomic 

emission spectroscopy (ICP-AES), employed an acid digestion and thus the silver concentrations 

are for total-silver content. The plastics leaching study reported method detection limits that 

ranged from 0.8 to 2 μg/L. However, because there were no validation data provided to support 

these LODs, EPA is using the silver LOD of 5 μg/L, which is the value reported as the estimated 

LOD in U.S. EPA Method 6010C (U.S. EPA, 2007a) and as the reporting limit in the plastics 

leaching study (see Table 1, Page 30 of the study report). 

Table 7 –Silver Concentrations in Fluid Contacting NSPW-L30SS Treated Plastic Coupons 

Fluid (40 degrees C) Maximum Silver Concentration 

Detected (μg/L)

Silver Matrix Spike 

Recovery (%) 

Low pH, pH 2.0 using 10% nitric acid in 

water 15 of 15 samples < 5 μg/L 93 to 110 

High pH, pH 8.0 using 0.1N sodium 

hydroxide in water 15 of 15 samples < 5 μg/L 100 

Because the concentration of silver in the low and high pH fluids were all below the analytical 

LOD of 5 μg/L, the EPA used 2.5 μg/L as the concentration of silver released from plastics 

incorporating NSPW-L30SS. This was based on the assumption that all results reported as being 

below the LOD had a value of one-half the LOD (i.e., 2.5 μg/L), which is consistent with how 

EPA assigns values to non-detect results when evaluating pesticide residues in food (US EPA, 

2000). Since this value is below the LOD, the form of any potentially released silver is unknown 

and was assumed to be in the form of nanosilver as found in NSPW-L30SS. Using the assumed 

concentration of 2.5 μg/L equates to nanosilver releases of 0.17, 0.08, and 0.042% from the 

coupons containing 5, 10, and 20 mg/kg of nanosilver, respectively. Plastic products incorporating 

NSPW-L30SS are to contain a maximum of 0.003% nanosilver by weight or 30 mg/kg of 

nanosilver. Assuming that a leaching study conducted using a coupon containing 30 mg/kg of 

nanosilver would also result in nanosilver releases below the LOD would result in a nanosilver 

release rate of 0.028% for a coupon containing 30 mg/kg of nanosilver. 

The plastic coupon leaching study was initially determined to be unacceptable by EPA because 

less than 0.8% of the silver in the plastic coupons was recovered during the ashing process, the 

wide range in silver matrix-spike recoveries for some of the food simulants (particularly alcohol 
28 

and oil), and the lack of validation data for the silver analysis. Nanosilva LLC subsequently 

completed an additional study to determine the silver content of identically prepared plastic 

coupons (MRID 48652901). As per EPA recommendation, Nanosilva LLC employed the nondestructive Neutron Activation Analysis (NAA) to determine the silver content of the NSPWL30SS liquid suspension, a master batch containing 2% NSPW-L30SS, and plastic coupons 

containing 5% of the NSPW-L30SS master batch. Using NAA, Nanosilva LLC determined the 

amount of silver in coupons was within 99% of the amount added. In addition, EPA decided that 

the plastics leaching study could be used to evaluate the release of silver from NSPW-L30SS 

treated plastics into physiological fluids because the recoveries for the most relevant food 

simulants, low and high pH fluids, were close to 100 percent. 

The plastics leaching study was conducted using a protocol that was not reviewed by EPA prior to 

conducting the study. The plastics leaching study did not employ physiological fluids such as 

artificial saliva; however, the study was completed at the physiological temperature of 40 degrees 

Celsius. The coupons tested contained nanosilver at concentrations of 5, 10, and 20 mg/kg, which 

are less than the maximum nanosilver concentration of 30 mg/kg that on the NSPW-L30SS 

pesticide label. Even though the study was not conducted using physiological fluids, the study 

does provide a reasonable estimate for the amount of silver transferred to the mouth while 

mouthing and transferred to skin while contacting plastics incorporating NSPW-L30SS. 

Based upon this study, the transferable surface residue is 0.0011 ug/cm2

. This value represents the 

concentration of silver detected in low and high pH fluids, which are more representative of 

biological fluids, contacting NSPW-L30SS containing coupons that is transferable from the 

surface of the toy into the child’s mouth. The concentration of silver in the low and high pH fluids 

were all below the analytical LOD of 5 μg/L for coupons containing 5, 10, and 20 mg/kg of 

NSPW-L30SS. EPA is assuming that non-detectable concentrations of silver would be found in a 

similar test conducted with coupons containing 30 mg/kg of NSPW-L30SS. EPA is using 2.5 

μg/L, which is one-half the LOD of 5 μg/L, as the concentration of silver released from plastic 

incorporating NSPW-L30SS. Using the concentration of silver, the volume of the leachate (50 

mL), and the surface area of the test coupons, the amount of transferable nanosilver at the coupon 

surface is: 

Transferable Surface residue: ଶ.ହ	௨௚

௅

ൈ

ହ଴	௠௅

ൈ

௅

ଵ଴଴଴	௠௅

ൈ

ଵଵଶ	௖௠మ ൌ ଴.଴଴ଵଵ௨௚௖௠మ

Textile Leaching Study 

Nanosilva LLC prepared and submitted a draft protocol titled “The Quantification and 

Characterization of Silver Released from Textiles Treated with NSPW-L30SS (NSPW-L30) as a 

Results of Washing” with the stated purpose to quantify and characterize silver released from 

textiles incorporating NSPW-L30SS during laundering. The protocol was based on methods 

developed by Geranio et al. (2009) and Lorenz et al. (2012) who modified the ISO Colour Fastness 

test (ISO, 1997) to determine the amount and form of silver released to the environment when 

washing textiles containing silver and nanosilver. Because EPA must also evaluate the release of 

nanosilver when children chew and mouth textiles incorporating NSPW-L30SS, EPA 

recommended including an additional test using simulated human saliva. EPA does not anticipate 

dermal exposure will result in a risk concern for textiles incorporating NSPW-L30SS, and 

therefore a separate leaching study involving simulated human sweat was not recommended. EPA 

will use the results of the ISO Colour Fastness test completed with simulated human saliva to 

evaluate the dermal exposure to nanosilver from textiles incorporating NSPW-L30SS. 
29 

Nanosilva LLC completed and submitted the modified ISO Colour Fastness test (MRID 

49045301) using shirts incorporating NSPW-L30SS. The washing tests were conducted on shirts 

composed of polyethylene terephthalate (PET), which incorporated NSPW-L30SS into the PET 

yarn for a final nanosilver content of 0.00262% or 26.2 mg/kg per shirt. For the detergent wash 

test, a section was cut from each of three shirts and washed separately in 150 mL of distilled water 

with commercial laundry detergent and 10 hard rubber balls with diameter of 10 mm for 30 

minutes at 40 degrees Celsius. The detergent wash was followed by two rinse cycles with 

deionized water. The concentrations of silver in the wash and rinse water were determined after 

filtering samples through a 0.45 μm pore size filter using inductively coupled plasma mass 

spectrometry (ICP-MS). The concentration of silver retained on the filter was also determined by 

ICP-MS. These samples were acid digested prior to analysis and thus the silver concentrations are 

for total-silver content and do not distinguish between silver ions, nanosilver, or NSPW-L30SS. 

Although the NSPW-L30SS wash test study reported an ICP-MS LOD of 0.0094 μg/L for aqueous 

samples and 0.94 μg/kg for filter samples, EPA determined that the LOD for aqueous samples was 

10 μg/L and 1,000 μg/kg for solids samples. EPA determined these LODs based on a statistical 

analysis of seven ICP-MS calibration curves and the analysis results from 100 μg/L quality control 

samples. The concentration of silver in the wash and rinse water from the detergent wash test for 

three shirt sections was below the analytical LOD of 10 μg/L (Table 8). The concentration of 

silver retained on 0.45 μm pore size filters was also less than the analytical LOD of 1,000 μg/kg. 

Table 8 – Concentration of Silver Released from Shirts Incorporating NSPW-L30SS 

Number of 

Shirt Sections Wash Medium 

Concentration of Silver 

Wash/Rinse Water 0.45 μm Pore Size Filter 

(Particles with Diameters >0.45 μm) 

3 Distilled Water 

with Detergent < 10 ug/liter < 1,000 ug/kg 

9 Simulated Human 

Saliva < 10 ug/liter < 1,000 ug/kg 

A separate study was conducted using three sections from each of three shirts and washed 

separately in 150 mL of simulated human saliva with 10 hard rubber balls with diameter of 10 mm 

for 45 minutes at 40 degrees Celsius. The concentration of silver in the simulated saliva was 

determined after filtering through a 0.45 μm pore size filter using ICP-MS where the concentration 

of silver in the saliva for nine shirt sections was below the analytical LOD of 10 μg/L (Table 8). 

The concentration of silver retained on filters was less than the analytical LOD of 1,000 μg/kg. 

Given that none of the silver concentrations in detergent or saliva solutions were above 10 μg/L 

and none of the filters contained silver at a concentration above 1000 μg/kg, EPA evaluated the 

amount of silver released from textiles incorporating NSPW-L30SS by replacing the non-detect 

values with half the LOD, 5 μg/L for liquid samples and 500 μg/kg for solids samples (U.S. EPA, 

2000). The amount of silver released from textiles was calculated based on the volume of 

detergent and rinse water, and saliva along with the mass of the 0.45 μm filters used for each test 

(Table 9). 
30 

Table 9 – Amount of Silver Released from Shirts Incorporating NSPW-L30SS 

Wash Medium Volume/Mass Concentration Amount of 

Silver (μg) 

Total-silver 

Potentially Released 

(μg) % 

Distilled Water 

with Detergent 

190 mL wash/rinse water 5 μg/LB 0.95 1.05 1.6 0.2 g filtersA 500 μg/kgB 0.1 

Simulated Human 

Saliva 

150 mL Saliva 5 μg/L 0.75 0.81 0.9 0.12 g filter 500 μg/kg 0.06 

A. There was a 0.1 g filter used for the detergent wash and another 0.1 g filter for the rinse. 

B. Set to half the LOD. 

The initial amount of silver in textiles washed with distilled water and detergent was 66.54 μg, 

therefore the amount of silver released during the detergent wash was: 

Silver released in detergent wash = ଵ.଴ହஜ௚

଺଺.ହସ	ஜ௚ ൈ 100% ൌ 1.6%

The initial amount of silver in textiles washed with simulated human saliva was 94.9 μg, therefore 

the amount of silver released during the saliva wash was: 

Silver released in saliva wash = ଴.଼ଵஜ௚

ଽସ.ଽ	ஜ௚ ൈ 100% ൌ 0.9%

The value of 1.6% is used in evaluating releases to the environment from wash water and the value 

of 0.9% is used in calculating oral and dermal exposures to textiles incorporating NSPW-L30SS. 

Since these releases were determined using concentrations that were below the ICP-MS LOD, the 

form of silver is unknown. EPA assumes the form of silver is identical to the nanosilver present in 

NSPW-L30SS in the absence of further information. 

The results of these studies demonstrate that PET shirts which incorporate NSPW-L30SS at 26.2 

μg/kg of nanosilver do not release silver at concentrations above the analytical LOD. The ISO 

Colour Fastness test is thought to represent aggressive washing conditions with one wash cycle 

representing up to five domestic or commercial laundering cycles when the multiple test is 

employed. The amount of silver released during one ISO Colour Fastness test is believed to exceed 

the daily exposure to nanosilver from a treated textile because the ISO Colour Fastness test 

involves immersing the textile in water containing detergents or simulated human saliva and hard 

rubber balls followed by mechanical agitation for 30 to 45 minutes. Thus, results from studies 

which are based on the ISO Colour Fastness test will be used to determine the daily dose of 

nanosilver for children who chew and mouth, adults who wear, and workers who manufacture 

items from nanosilver-treated textiles even though this likely overestimates the daily dose of 

nanosilver. 

5.2.2 Consumer Margins of Exposure to Plastics Incorporating NSPW-L30SS 

EPA expects that consumers will be exposed to plastics incorporating NSPW-L30SS by the routes 

of incidental oral and dermal exposures. As detailed in the following sections, EPA evaluated the 

risk to children, as the likely most vulnerable subpopulation, from mouthing toys, and mouthing 

and crawling on flooring incorporating NSPW-L30SS. 

Incidental Oral Exposures for Toys Incorporating NSPW-L30SS

Incidental oral exposures to toys incorporating NSPW-L30SS were calculated using the following: 

Incidental Oral Exposure = Transferable Surface Residue × Surface Area of Toy Mouthed 
31 

Where: 

 The transferable surface residue is 0.0011 ug/cm2 based on the Plastics Leaching Study 

(MRID 478289-25). This value represents the concentration of silver detected in low and 

high pH fluids, which are more representative of biological fluids, contacting NSPW-L30SS 

containing coupons that is transferable from the surface of the toy into the child’s mouth. 

 The surface area of a toy mouthed per day is 800, 560 and 396 cm2 for 6 to <12 month, 1 

to < 2 year and 2 to < 3 year-old children, respectively. These values were calculated 

assuming that a child mouths an area of 10 cm2

 each time they contact a toy, that 6 to < 12 

month-old children contact objects 20 times per hour, 1 to < 2 year-old children contact 

objects 14 times per hour, and 2 to < 3 year-old children contact objects 9.9 times per hour 

(U.S. EPA, 2011a) for 4 hours per day. 

The incidental oral dose was calculated from the incidental oral exposure using the following: 

Incidental Oral Dose = Exposure / Body Weight 

Where: 

 Exposure is determined in the calculations above. 

 The body weight is 9.2, 11.4 and 13.8 kg for children 6 to < 12 months old, 1 to <2 years 

old and 2 to < 3 years old, respectively (U.S. EPA, 2011b). 

The MOEs in Table 10 are for incidental oral exposures and were calculated from the incidental 

oral dose using the POD of 30 mg/kg/day, which is the NOAEL from a 28-day oral toxicity study 

(Kim et al., 2008) and the LOAEL from a 90-day oral toxicity study (Kim et al., 2010). The MOEs 

range from 310,000 to 940,000, depending on the age of the child. These MOES are well above 

the target MOEs of 1,000 and 3,000, for short and intermediate terms exposures, respectively, 

which means that the risk for short- and intermediate-term exposure to children who mouth plastic 

toys containing NSPW-L30SS is not of concern. 

Table 10 – Incidental Oral MOEs for Plastic Toys Incorporating NSPW-L30SS 

Age of Child 

Body 

Weight 

(kg) 

Transferable 

Surface Residue

(ug/cm2) 

Surface Area 

Mouthed per 

Day (cm2) 

ExposureA

(ug/day) 

DoseB

(ug/kg/day) MOEC,D 

6 to < 12 months 9.2 

0.0011 

800 0.88 0.096 310,000

1 to < 2 years 11.4 560 0.62 0.054 560,000

2 to < 3 years 13.8 396 0.44 0.032 940,000

A. Exposure = Transferable Surface Residue (ug/cm2) × Surface Area of Toy Mouthed (cm2) 

B. Dose = Exposure (ug/day) / Body Weight (9.2, 11.4 or 13.8 kg) 

C. MOE = [POD (30 mg/kg/day) x 1000 ug/mg] / Daily Dose (ug/kg/day) 

D. Target MOE is 1000 for short-term exposures and 3000 for intermediate term exposures. 

Dermal Exposure to Flooring Incorporating NSPW-L30SS 

The dermal exposure to flooring incorporating NSPW-L30SS was calculated using the following: 

Dermal Exposure = Transferable Surface Residue (mg/cm2

) × Body surface area in contact 

with floor (cm2

/day) 
32 

Where: 

 The transferable surface residue is 0.0011 ug/cm2 based on the Plastics Leaching Study 

(MRID 478289-25). 

 The body surface area contacting flooring is 4,500, 5300 and 6,100 cm2/day for 

children 6 to < 12 months old, 1 to < 2 years old, and 2 to < 3 years old, respectively (U.S. 

EPA, 2011b). These are the total surface area of children and do not account for the portion 

of child covered with clothing. 

The dermal dose was calculated from the dermal exposure using the following: 

Dermal Dose = [Exposure × Dermal Absorption]/ Body Weight 

Where: 

 Exposure is determined in the calculations above. 

 The dermal absorption is 6.7 percent (see Section 4.2.3). 

 The body weight is 9.2, 11.4 and 13.8 kg for children 6 to < 12 months old, 1 to <2 years 

old and 2 to < 3 years old, respectively (U.S. EPA, 2011b). 

The MOEs in Table 11 are for dermal exposures to flooring incorporating NSPW-L30SS and were 

calculated from the dermal dose using the POD of 30 mg/kg/day, which is the NOAEL from a 28-

day oral toxicity study (Kim et al., 2008) and the LOAEL from a 90-day oral toxicity study (Kim 

et al., 2010). The MOEs range from 820,000 to 910,000, depending on the age of the child. These 

MOES are well above the target MOEs of 1,000 and 3,000 for short and intermediate terms 

exposures, respectively, which means that the risk for short- and intermediate-term dermal 

exposure to children who contact flooring incorporating NSPW-L30SS is not of concern. 

Table 11 – Dermal MOEs for Flooring Incorporating NSPW-L30SS 

Age of Child 

Body 

Weight 

(kg) 

Transferable 

Surface Residue

(ug/cm2) 

Exposed Body 

Surface Area

(cm2) 

ExposureA

(ug/day) 

DoseB

(ug/kg/day) MOEC,D 

6 to < 12 months 9.2 

0.0011 

4,500 5.0 0.036 830,000 

1 to < 2 years 11.4 5,300 5.8 0.034 880,000 

2 to < 3 years 13.8 6,100 6.7 0.033 910,000 

A. Exposure = Transferable Surface Residue (ug/cm2) × Exposed Body Surface Area (cm2) 

B. Dose = [Exposure (ug/day) × Dermal absorption (6.7%)] / Body Weight (9.2, 11.4 or 13.8 kg) 

C. MOE = [POD (30 mg/kg/day) x 1000 ug/mg] / Daily Dose (ug/kg/day) 

D. Target MOE is 1000 for short-term exposures and 3000 for intermediate term exposures. 

Incidental Oral Exposures to Flooring Incorporating NSPW-L30SS 

The incidental oral exposure to nanosilver in flooring incorporating NSPW-L30SS was calculated 

using the following: 

Incidental Oral Exposure = Transferable Surface Residue (mg/cm2

) × Surface area of hand 

that contacts the floor and the child’s mouth (cm2

/event) × Frequency of hand-to-mouth 

contacts (events/hr) × Exposure time (hr/day) x Saliva Extraction Efficiency 

Where: 

 The transferable surface residue is 0.0011 ug/cm2 based on the Plastics Leaching Study 

(MRID 478289-25). 
33 

 The hand to mouth (HTM) surface area (i.e. the surface area of the hand that contacts both 

the floor and the child’s mouth) is 16 cm2

/event for 6 to < 12 month-old children, 20 

cm2/event for 1 to < 2 year-old children and 21 cm2/ event for 2 to < 3 year-old children. 

The HTM value of 20 cm2 for 1 to < 2 year children is listed in the SOPS (US EPA, 2012b) 

and is based on the mean surface area of one hand (150 cm2) for children 1< 2 years old as 

listed in Table 7-2 of the Exposure Factors Handbook (US EPA, 2011b) and the fraction of 

the hand mouthed per event (0.13) from an analysis included in Zartarian et al. (2005). 

Table 7-2 also lists mean hand surface areas of 120 cm2 for 6 to < 12 month-old children, 

140 cm2 for 2 to < 3 year-old children and 185 cm2 for 3 to < 6 year-old children. The hand 

surface area of 120 cm2 for 6 to < 12 month-old children was used in conjunction with the 

fraction of the hand mouthed per event (0.13) to derive the HTM value of 16 cm2

/event for 

6 to < 12 month-old children. The average of the hand surface areas values of 140 cm2 (2 

to < 3 old children) and 185 cm2 (3 to < 6 year-old children) along with the fraction hand 

mouthed value (0.13) was used to derive the hand to mouth surface of 21 cm2 for 2 to < 3 

old children. 

 Frequency of hand-to-mouth events is 19 events/hr for 6 to < 12 month-old children, 20 

events/hr for 1 to < 2 year-old children, and 13 events/hr for 2 to <3 year-old children (U.S. 

EPA, 2011b). 

 Exposure time is 101 minutes (1.68 hours) per day for 6 to < 12 month-old children, 126 

minutes (2.10 hours) per day for 1 to < 2 year-old children, and 108 minutes/day (1.80 

hours) for 2 to <3 year-old children. These are the mean times for “Doers” in kitchens and 

bathrooms (Table 16-15, U.S. EPA, 2011b) 

 Saliva extraction efficiency from hand to mouth is 50% (U.S. EPA, 2012b) 

The incidental oral dose was calculated from the incidental oral exposure using the following: 

Incidental Oral Dose = Exposure / Body Weight 

Where: 

 Exposure is determined in the calculations above. 

 The body weight is 9.2 kg, 11.4 kg and 13.8 kg for children 6 to < 12 months old, 1 to <2 

years old and 2 to < 3 years old, respectively (U.S. EPA, 2011b).

The MOEs in Table 12 are for incidental oral exposures to flooring incorporating NSPW-L30SS 

and were calculated from the incidental oral dose using the POD of 30 mg/kg/day, which is the 

NOAEL from a 28-day oral toxicity study (Kim et al., 2008) and the LOAEL from a 90-day oral 

toxicity study (Kim et al., 2010). The MOEs range from 970,000 to 1,500,000 depending upon the 

age of the child. These MOES are well above the target MOEs of 1000 and 3,000 for short and 

intermediate terms exposures, respectively. This means that the risk for short- and intermediateterm exposure to children who mouth their hands after contacting flooring incorporating NSPWL30SS is not of concern.
34 

Table 12 – Incidental Oral MOEs for Flooring Incorporating NSPW-L30SS 

Age of Child 

Transferable 

Surface 

Residue 

(ug/cm2) 

Frequency of 

Hand to Mouth 

Contacts 

(Events/ Hour)

Daily 

Exposure 

Time 

(Hours) 

ExposureA

(ug/day) 

DoseB

(ug/kg/day) MOEC,D 

6 to < 12 months 

0.0011 

19 1.68 0.28 0.031 970,000 

1 to < 2 years 20 2.10 0.46 0.041 730,000 

2 to < 3 years 13 1.80 0.27 0.020 1,500,000 

A. Exposure = Transferable Surface Residue (ug/cm2) × Surface area of hand that contacts the floor and the child’s 

mouth (16, 20 and 21 cm2

/event) × Frequency of Hand to Mouth Contacts (Events/hour) × Daily Exposure Time 

(hours) × Saliva extraction efficiency (50 %) 

B. Dose = [Exposure (ug/day)] / Body Weight (9.2, 11.4 or 13.8 kg) 

C. MOE = [POD (30 mg/kg/day) × 1000 ug/mg] / Daily Dose (ug/kg/day) 

D. Target MOE is 1000 for short-term exposures and 3000 for intermediate term exposures. 

5.2.3 Consumer Margins of Exposure to Textiles Incorporating NSPW-L30SS 

EPA expects that consumers will be exposed to textiles incorporating NSPW-L30SS by the routes 

of inhalation, dermal, and incidental oral exposures. 

Consumer Inhalation Exposures 

EPA recognizes the potential for inhalation exposure to nanosilver during laundry drying of 

textiles incorporating NSPW-L30SS. However, EPA lacks information on the release rate of 

nanosilver from textiles incorporating NSPW-L30SS during laundry drying. While exposure may 

occur during laundry drying, EPA believes that when compared to exposure through dermal and 

oral contact with textiles incorporating NSPW-L30SS, exposure during laundry drying will likely 

be of lower significance. To support this, an estimate of the inhalation dose that might occur from 

exposure to textiles incorporating NSPW-L30SS during laundry drying was calculated using the 

following: 

Inhalation Dose = Amount of NSPW-L30SS in clothing handled per day × Unit Exposure 

Where: 

 Amount of NSPW-L30SS in clothing handled per day assumed that one t-shirt containing 

NSPW-L30SS was laundered where the amount of nanosilver in a t-shirt is equal to 150 g 

× 30 mg/kg × kg ÷ 1000 g = 4.5 mg. 

 The unit exposure for inhalation of wettable powder is 7.8 μg/m3

/lb when no respirator is 

worn (U.S. EPA, 2011a). 

The MOE shown in Table 13 was calculated by dividing the inhalation dose by the POD of 49 

μg/m3, which is the NOAEL from a 90-day inhalation toxicity study for nanosilver (Song et al., 

2012). This assumes that NSPW-L30SS released from textiles during drying behaves like 

nanosilver after inhalation. This analysis further assumes that all of the nanosilver from the textile 

incorporating NSPW-L30SS becomes airborne during a single laundry drying event and this 

exposure would be similar to mixing and loading of wettable powders (U.S. EPA, 2011a). The 

MOE of 640,000 is well above the target MOE of 1000 which means that the risks are not of 

concern. Even if 100 t-shirts incorporating NSPW-L30SS were laundered per day, the MOE would 

be 6,400 which is well above the target MOE of 1,000. 
35 

Table 13 – Inhalation MOE for Drying Textiles Incorporating NSPW-L30SS 

Scenario 

Number of 

Nanosilver Treated 

T-shirts Laundered 

per day 

Amount of 

Nanosilver 

Laundered per 

dayA

Unit 

ExposureB 

(μg/m3/lb 

AI) 

DoseC 

(μg/m3) MOED,E 

Unload Clothes 

Dryer (Without 

Respirator) 

1 4.5 mg 

(0.0000099 lb) 7.8 

0.000077 640,000 

100 450 mg 

(0.00099 lb) 0.0077 6,400 

A. Amount of Nanosilver laundered per day = Amount of NSPW-L30SS in t-shirt × Mass of t-shirt 

B. PHED unit exposure value converted to air concentration units based on mean 8 hour TWA 

C. Dose = Amount Nanosilver Handled × Unit Exposure 

D. MOE = POD / Daily Dose 

E. The target MOE is 1000. 

Consumer Dermal Exposures to Textiles 

The dermal exposure to textiles incorporating NSPW-L30SS was calculated using the following: 

Dermal Exposure = Amount of NSPW-L30SS in Textile × Cloth Density × Surface Area 

Exposed × Transfer Efficiency 

Where: 

 The textile incorporating NSPW-L30SS contains 30 mg/kg nanosilver. 

 The cloth density is 10 mg/cm2 based on the density of mixed cotton and synthetics. This 

value is a standard assumption used in OPP risk assessments and was taken from the 

HERA Guidance Document Methodology (AISE/CEFIC, 2005). 

 The total surface area for a 6 to < 12 month-old is 4,500 cm2/day, for a 1 to < 2 year-old is 

5,300 cm2

/day, and for a 2 to < 3 year-old is 6,100 cm2/day (U.S. EPA, 2011b). 

 The cloth-to-skin transfer efficiency was based on the amount of silver released during the 

leaching study which was 0.9% based on one-half the LOD (see Table 9). 

The dermal dose was calculated from the dermal exposure using the following: 

Dermal Dose = Exposure × Dermal Absorption / Body Weight 

Where: 

 Exposure is determined in the calculation above. 

 The dermal absorption (DA) is 6.7% (see Section 4.2.3). 

 The body weight of a child with age between 6 and < 12 months is 9.2 kg, between 1 and < 

2 years is 11.4 kg, between 2 and < 3 years is 13.8 (U.S. EPA, 2011b). 

The MOEs in Table 14 for dermal exposures were calculated from the dermal dose using the POD 

of 30 mg/kg/day, which is the NOAEL from a 28-day oral toxicity study (Kim et al., 2008) and the 

LOAEL from a 90-day oral toxicity study (Kim et al., 2010). The MOEs range from 340,000 to 

370,000 depending upon the age of the child. These MOES are well above the target MOEs of 

1000 and 3,000 for short and intermediate term exposures, respectively, which means that the risks 

are not of concern. 
36 

Table 14 – Dermal MOEs for Textiles Incorporating NSPW-L30SS 

Age of 

Child 

Application 

Rate 

(mg/kg) 

Cloth 

Density 

(mg/cm2) 

Surface Area 

Exposed 

(cm2/day) 

Cloth-to-Skin 

Transfer 

Efficiency 

ExposureA 

(mg/day) 

DoseB 

(ug/kg/day) MOEC,D

6 to <12 

months 

30 10 

4,500 

0.9% 

0.012 0.087 340,000 

1 to < 2 

years 5,300 0.014 0.082 370,000 

2 to < 3 

years 6,100 0.017 0.083 360,000 

A. Exposure = Application Rate × Cloth Density × Surface Area Exposed × Cloth-to-Skin Transfer Efficiency 

B. Dose = [Exposure (mg/day) × 1000 ug/mg × DA (6.7%)] / Body Weight (9.2, 11.4 or 13.8 kg) 

C. MOE = [POD (30 mg/kg/day) x1000 ug/mg] / Daily Dose (ug/kg/day) 

D. Target MOE is 1000 for short-term exposures and 3000 for intermediate term exposures. 

Consumer Incidental Oral Exposures to Textiles

Incidental oral exposures were calculated using the following: 

Incidental Oral Exposure = Amount of NSPW-L30SS in Textile × Cloth Density × Surface Area 

Mouthed × Saliva Extraction Efficiency 

Where: 

 The textile incorporating NSPW-L30SS contains 30 mg/kg nanosilver. 

 The cloth density is 10 mg/cm2 based on the density of mixed cotton and synthetics. This 

value is a standard assumption used in OPP risk assessments and was taken from the 

HERA Guidance Document Methodology (AISE/CEFIC, 2005) 

 The surface area of fabric that is mouthed by a toddler per day is assumed to be 100 cm2 

(~16 in.2) which represents an estimate, for example, of the area of blanket or shirt sleeve. 

 The nanosilver saliva extraction efficiencies for mouthing fabric are based on the results of 

the leaching study which was 0.9% based on one-half the LOD (see Table 9). 

The incidental oral dose was calculated from the incidental oral exposure using the following: 

Incidental Oral Dose = Exposure / Body Weight 

Where: 

 Exposure is determined in the calculation above. 

 The body weight of a child with age between 6 and < 12 months is 9.2 kg, between 1 and 

<2 years is 11.4 kg, between 2 and < 3 years is 13.8, which is for children who mouth 

textiles (U.S. EPA, 2011b). 

The MOEs in Table 15 for incidental oral exposures were calculated from the incidental oral dose 

using the POD of 30 mg/kg/day, which is the NOAEL from a 28-day oral toxicity study (Kim et 

al., 2008) and the LOAEL from a 90-day oral toxicity study (Kim et al., 2010). The MOEs range 

from 1,000,000 to 1,500,000 depending upon the age of the child. These MOEs are well above the 

target MOEs of 1000 and 3,000 for short and intermediate terms exposures, respectively, which 

means that the risk for short- and intermediate-term exposure to children who mouth textiles 

incorporating NSPW-L30SS is not of concern. 
37 

Table 15 – Incidental Oral MOES for Textiles Incorporating NSPW-L30SS 

Application 

Rate 

(mg/kg) 

Cloth Density 

(mg/cm2) 

Surface Area 

Mouthed 

(cm2/day) 

Saliva 

Extraction 

Efficiency 

ExposureA 

(mg/day) 

DoseB

(ug/kg/day) MOEC, D

30 10 100 0.9% 0.00027 

0.029 1,000,000 

0.024 1,200,000 

0.020 1,500,000 

A. Exposure = Application Rate × Cloth Density × Surface Area Mouthed × Saliva Extraction Efficiency 

B. Dose = [Exposure (mg/day) x 1000 ug/mg] / Body Weight (9.2, 11.4 and 13.8 kg) 

C. MOE = [POD (30 mg/kg/day) x 1000 ug/mg] / Daily Dose (ug/kg/day) 

D. Target MOE is 1000 for short-term exposures and 3000 for intermediate term exposures. 

5.2.4 Aggregate MOES for Plastics and Textiles Incorporating NSPW-L30SS 

In the Federal Food, Drug, and Cosmetic Act (FFDCA), Congress specified that, to establish an 

acceptable level of a given pesticide’s chemical residue that could be found in or on food products, 

EPA must determine that “there is a reasonable certainty that no harm will result from aggregate 

exposures to the pesticide chemical residue, including all anticipated dietary exposures and all 

other exposures for which there is reliable information.” Furthermore, when enacting this 

provision of the FFDCA, Congress also amended FIFRA’s definition of unreasonable adverse 

effects. Specifically, Congress redefined unreasonable adverse effects to include “a human dietary 

risk from residues that result from a use of a pesticide in or on any food inconsistent with the 

standard under” the FFDCA. In other words, Congress explicitly required the consideration of 

aggregate exposures for registration decisions under FIFRA for food-use pesticides, but chose not 

to similarly alter the statutory requirements for nonfood-use pesticides. 

The following analysis is for children who are simultaneously exposed to nanosilver via the 

incidental oral and dermal routes of exposure while mouthing toys, contacting flooring, and 

mouthing textiles incorporating NSPW-L30SS. Inhalation exposure to children during laundry 

drying of textiles incorporating NSPW-L30SS is not anticipated and is not considered as part of 

the aggregate exposure. The aggregate daily dose was calculated by adding the daily oral and 

dermal doses using the following: 

Aggregate Dose = Incidental Oral Dose to Toys Incorporating NSPW-L30SS + Dermal Dose 

to Flooring Incorporating NSPW-L30SS + Incidental Oral Dose to Flooring Incorporating 

NSPW-L30SS + Dermal Dose to Textiles Incorporating NSPW-L30SS + Incidental Oral Dose 

to Textiles Incorporating NSPW-L30SS 

Where: 

 Incidental Oral Dose to Toys Incorporating NSPW-L30SS is from Table 10; 

 Dermal Dose to Flooring Incorporating NSPW-L30SS is from Table 11; 

 Incidental Oral Dose to Flooring Incorporating NSPW-L30SS is from Table 12. 

 Dermal Dose to Textiles Incorporating NSPW-L30SS is from Table 14; and 

 Incidental Oral Dose to Textiles Incorporating NSPW-L30SS is from Table 15. 

The oral and dermal daily doses can be summed because they are evaluated using the same POD 

of 30 mg/kg/day. The aggregate MOEs in Table 16 range from 110,000 to 160,000 depending on 

the age of the child. These MOEs are all well above the target MOEs of 1,000 and 3,000 for short 

and intermediate terms exposures, respectively, which means that the risk for short- and 

intermediate-term aggregate exposure to children is not of concern. 
38 

Table 16 – Aggregate MOEs for Toys, Flooring and Textiles Incorporating NSPW-L30SS 

Age of Child 

 Toys Flooring Textile Aggregate 

Incidental 

Oral Dose 

Dermal 

Dose 

Incidental 

Oral Dose 

Dermal 

Dose 

Incidental 

Oral Dose

DoseA

(ug/kg/day) MOEB,C

6 to < 12 months 0.096 0.036 0.031 0.087 0.029 0.28 110,000 

1 to < 2 years 0.054 0.034 0.041 0.082 0.024 0.24 120,000 

2 to < 3 years 0.032 0.033 0.020 0.083 0.020 0.19 160,000 

A. Aggregate Dose = Sum of the Incidental Oral and Dermal Doses (ug/kg/day) for Toys, Flooring and Textiles 

B. Aggregate MOE = [POD (30 mg/kg/day) × 1000 ug/mg] / Dose (ug/kg/day) 

C. The target MOE is 1000 for short-term exposure and 3000 for intermediate term exposures. 

The assessment above is for the concurrent exposure to the nanosilver in NSPW-L30SS via the 

incidental oral and dermal routes of exposure while mouthing toys and textiles, and contacting 

flooring incorporating NSPW-L30SS. Aggregate assessments can also include other sources of 

exposure such as to NSPW-L30SS in food and drinking water, and to other nanosilvers in the 

market place that are identical to the nanosilver in NSPW-L30SS. There are no anticipated food 

exposures to NSPW-L30SS since Nanosilva LLC has not supplied the necessary information to 

support a food contact application and the pesticide label for NSPW-L30SS states that it is only for 

non-food contact use. Neither the nanosilver that might break away from NSPW-L30SS or NSPWL30SS is anticipated to enter drinking water because any particulates released to surface water 

would be removed by gravitational sedimentation and adsorption (see Section 5.1.1). 

The only other pesticide product registered as containing nanosilver is HeiQ AGS-20 (U.S. EPA, 

2011a). The nanosilver in HeiQ AGS-20 has different size range and surface coatings than the 

nanosilver in NSPW-L30SS, and EPA has not determined that AGS-20 and NSPW-L30SS contain 

the same active ingredient or present exposures that should necessarily be aggregated. 

As to exposure to other nanosilvers in the market place, an aggregate risk assessment involves the 

analysis of exposure to a single chemical by multiple pathways and routes of exposure that share a 

common toxic effect. For EPA to conduct such an assessment requires that EPA possess sufficient 

information such as: 

 identification of toxicological endpoints for each exposure route and duration; 

 identification of potential exposures for each pathway (food, water, and/or residential); 

 reconciliation of durations and pathways of exposure with durations and pathways of 

health effects; 

 determination of which possible residential exposure scenarios are likely to occur together 

within a given time frame (co-occurrence); 

 determination of magnitude and duration of exposure for all exposure combinations; 

 determination of the appropriate technique (deterministic or probabilistic) for exposure 

assessment; and 

 determination of the appropriate risk metric to estimate aggregate risk. 

 When EPA has the above information, or as in the case of triclosan where populationbased biological monitoring data were available to assess the co-occurrence of uses, EPA 

develops an aggregate exposure assessment for residential uses of a single chemical. 

 However, in the case of nanosilver, with the exception of the HeiQ products, EPA does not 

yet have reliable information on the composition of the nanosilver or potential nanosilver 

in other silver based pesticides to determine if all nanosilvers should be treated as a single 
39 

chemical. These limitations include understanding how size, charge and coating effect the 

toxicity of nanosilvers. 

5.2.5 Conclusions for Consumer Risk 

The MOEs for the children’s exposure scenarios (toys, flooring and textiles) routes of exposure 

(dermal and incidental oral) and life stages (6 months to <1 year, 1 to <2 years and 2 to <3 years) 

range from 310,000 to 1,500,000 depending upon the scenario, exposure route and life stage. All 

of these MOE are well above the target MOEs of 1000 and 3,000 for short and intermediate term 

exposure, respectively, which means that there is no risk concern for children’s short- and 

intermediate-term exposure to toys, flooring and textiles incorporating NSPW-L30SS. 

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

flooring, and a textile while wearing a textile and crawling on flooring all incorporating NSPWL30SS are greater than 100,000 for all life stages, which indicates that the risk for short- and 

intermediate-term simultaneous exposure to plastics and textiles incorporating NSPW-L30SS is 

not a concern. 

Although children’s short- and intermediate-term exposure durations to plastic toys and textiles 

treated with NSPW-L30SS are expected, children are not anticipated to play with NSPW-L30SStreated toys or contact NSPW-L30SS-treated textiles every day for a period of greater than six 

months, thus long-term exposures are unlikely. Because of the potential for NSPW-L30SS to be 

used in flooring, long-term dermal and incidental oral exposures to children contacting flooring are 

possible. However, EPA does not believe that children will have continuous and daily exposure to 

flooring for a period of greater than 6 months. Even if these unlikely long-term exposures were to 

occur, the calculated MOEs for children’s dermal and incidental oral exposure to plastics and 

textiles incorporating NSPW-L30SS are greater than 100,000 indicating that daily exposure to 

plastics and textiles incorporating NSPW-L30SS for greater than 6 months are not of concern. 

There are several uncertainties in the consumer risk assessment. Because Nanosilva LLC 

completed leaching tests using plastic coupons containing nanosilver at concentrations of 5, 10, 

and 20 mg/kg, EPA assumed that non-detectable concentrations of silver would also be found if a 

leaching test was conducted with coupons containing nanosilver at 30 mg/kg. This assumption was 

reasonable because the concentration of silver in the textile leaching studies, which were 

conducted on textiles incorporating nanosilver at 30 mg/kg, was also below the analytical LOD, 

making it unlikely that NSPW-L30SS incorporated into plastic at 30 mg/kg will release nanosilver 

at detectable concentrations. The PODs used were based on inhalation and oral toxicity studies 

completed using nanosilver, not NSPW-L30SS or the nanosilver that might break away from 

NSPW-L30SS, and thus these PODs may not equal PODs determined from testing conducted with 

NSPW-L30SS or the nanosilver found in NSPW-L30SS. Because the nanosilver in the toxicity 

database is different from the nanosilver in NSPW-L30SS and because the database is incomplete 

with respect to reproductive and developmental effects, EPA used a maximum 10-fold database 

uncertainty factor when evaluating the risk from exposure to NSPW-L30SS and the nanosilver that 

might be released from products incorporating NSPW-L30SS. There are also uncertainties in 

extrapolating from effects observed after feeding test-animals nanosilver (i.e., oral route) to the 

effects that might be observed after applying nanosilver to the skin of test animals (i.e., dermal 

route). 

Taking the above into account, EPA concludes that use of NSPW-L30SS will not cause 

unreasonable adverse effects on the environment during the period when newly required data are 

being developed. 
40 

5.2.6 Consumer Exposure and Health Data Requirements 

EPA has determined that an additional leaching study is required for plastics incorporating NSPWL30SS using biological fluids and physiological temperatures, which includes methods to 

determine the form of silver released. EPA has determined that the textile leaching study 

submitted by Nanosilva LLC is acceptable and no additional studies on textiles incorporating 

NSPW-L30SS are required. 

EPA is requiring that Nanosilva LLC conduct plastic leaching tests as part of Tier I studies 

because the available study was completed using a protocol that was not reviewed by EPA prior to 

conducting the study, the coupons tested had less than the maximum nanosilver concentration of 

30 mg/kg, and the study did not use physiological fluids. The newly required leaching study 

should determine the nature and quantity of silver released from plastics incorporating NSPWL30SS under conditions of use. EPA will evaluate the results from the plastic leaching test along 

with results from Tier I toxicity studies discussed in Section 5.1.4 using a weight of evidence 

approach based on physical and chemical properties, toxicity, and exposure. If EPA identifies a 

concern, then EPA may require additional toxicity data to assess potential adverse health outcomes 

in young children resulting from incidental oral exposure to NSPW-L30SS-treated plastic toys 

(i.e., children chewing on toys). If additional toxicity data are needed, the study should evaluate 

peri- and post-natal exposure to NSPW-L30SS. A more detailed description of these data 

requirements is provided in Appendix B. 

VI. Environmental Risk Assessment

EPA anticipates the following substances could enter the environment through leaching of plastics 

and textiles incorporating NSPW-L30SS: 

1) silver ions released from NSPW-L30SS; 

2) NSPW-L30SS; and/or 

3) nanosilver that might break away from NSPW-L30SS. 

There are no studies available to characterize the environmental fate or ecotoxicity of NSPWL30SS. However, there are studies available in the scientific literature for nanosilver. Since 

nanosilver may be released from NSPW-L30SS, EPA has considered the scientific literature 

studies on nanosilver fate and ecotoxicity relevant to NSPW-L30SS. The following sections cover 

the environmental fate of nanosilver, the environmental hazards posed by silver and nanosilver, 

and the potential risk to aquatic species from nanosilver. Because it recognizes that differences in 

formulations from one nanosilver to another are likely to affect biological activity and fate, EPA 

has attempted to be cautious in how it has used information about other nanosilvers from the 

literature in assessing risks from NSPW-L30SS. As part of these discussions, additional data that 

EPA is requiring in order to confirm its assessment of the environmental risks of NSPW-L30SS 

are also identified in Section 7.3.1. 

6.1 Environmental Fate 

Nanosilva LLC has not conducted any studies to characterize the environmental fate of NSPWL30SS or the other particles that could be released during leaching or disposal of plastics and 

textiles incorporating NSPW-L30SS. In lieu of this information, EPA is relying on studies 

available in the scientific literature, discussed in the following section, as the basis for determining 

the fate of nanosilver in the environment. 
41 

6.1.1 Nanosilver 

The rate at which nanosilver transforms into ionic silver determines the length of time that these 

particles will reside in the environment. Although there are studies reporting that nanosilver will 

completely transform into ionic silver within six days after being dispersed into deionized water 

(Liu and Hurt, 2010), these results are only for one form of nanosilver and under conditions which 

are not representative of the environment. In the environment, nanosilver is likely to complex with 

naturally occurring anions such as chloride and sulfide or natural organic matter such as humic 

acids, which will significantly delay the rate at which nanosilver transforms into ionic silver. For 

example, Choi et al., (2009) provided spectroscopic evidence showing that nanosilver reacts with 

sulfide to produce stable silver-sulfide complexes, which were shown by Liu et al. (2010) and 

Levard et al. (2011) to have undetectable rates of nanosilver to ionic silver transformation. These 

stabilized nanosilver complexes are likely to partition to sediments, rather than remain suspended 

in water, due to gravitational settling and coagulation processes (FIFRA SAP, 2009, p. 19). 

Likewise, nanosilver is anticipated to partition to biosolids during wastewater treatment but may 

also be released in the effluent. Thus, there is the potential for nanosilver to reside or persist in the 

environment for a significant period of time where these particles are most likely to be associated 

with sediments. 

6.1.2 Silver Ions 

Ionic silver typically has low concentrations in natural waters, in the nanogram per liter range, due 

to its reactivity with chloride, sulfides, and natural organic matter (Andren and Armstrong, 1999). 

As with nanosilver, ionic silver is found in sediments and associated with biosolids in wastewater 

treatment plants. 

6.1.3 Impacts to Wastewater Treatment/Septic Systems 

There is the potential for nanosilver that might be released from plastics and textiles incorporating 

NSPW-L30SS to reach publicly owned wastewater treatment and privately owned septic systems 

where they will most likely complex with sulfide and partition to biosolids (Kaegi et al., 2011). 

Once entrained in the biosolids, the nanosilver could serve as a long-term source of ionic silver 

and could potentially adversely affect microorganisms that are vital to the wastewater treatment 

process. There are contradictory reports in the scientific literature regarding the impact of 

nanosilver on wastewater treatment systems. For example, nanosilver was reported to inhibit 

nitrification in the range of 50% (Choi and Hu, 2009a) to 84% (Choi and Hu, 2009b) based on a 

reduction in oxygen uptake rate in simulated wastewater sludge. However, Burkhardt et al. (2010) 

found no impact to nitrification at nanosilver dosages of 1 mg/L, the same dosage that Choi and 

Hu (2009a and 2009b) reported as inhibitory in municipal wastewater sludge. These two research 

groups are reporting different findings with the Burkhardt group suggesting little impact of 

nanosilver to nitrification and the Hu group suggesting that an impact to wastewater treatment 

systems from nanosilver is expected. A third group independently determined that nanosilver at 

concentrations from 0.5 to 1.5 mg/L had no detectable effect on the ability of the wastewater 

bacteria to biodegrade organic material, as measured by chemical oxygen demand (COD) (Wang 

et al., 2012a). More recent work by the Hu group reported that nanosilver at concentrations of up 

to 40 mg/L had negligible impact on anaerobic digestion and methanogenic organisms (Yang et 

al., 2012). 

While there are reports suggesting the potential for nanosilver to impact wastewater treatment 

operations, EPA does not anticipate that registering NSPW-L30SS will lead to negative impacts to 

wastewater treatment systems. This conclusion is based on the limited amount of silver released 
42 

from plastics and textiles incorporating NSPW-L30SS (see Section 5.2.1) and the small volume of 

nanosilver (i.e., < 1,693 kg/yr as estimated in Section 6.3.1) expected to be introduced into 

commerce from plastics and textiles incorporating NSPW-L30SS. 

6.2 Environmental Toxicity 

Nanosilva LLC has not conducted any studies to characterize the ecotoxicity of NSPW-L30SS or 

the other particles that could be released during leaching or disposal of plastics incorporating 

NSPW-L30SS. In lieu of this information, EPA is relying on studies available in the scientific 

literature, discussed in the following section, as the basis for determining the ecotoxicity of 

nanosilver. 

6.2.1 Silver Ions 

EPA has considerable data on the environmental hazards posed by the release of silver ions from 

conventional silver-based products. The precious metal silver is a trace element found in the 

Earth's crust and is generally naturally present in surface waters in relatively low concentrations as 

compared to metals such as copper and zinc. However, it may become toxic to aquatic life at 

elevated concentrations. Thus, silver concentrations in natural environments, and its biological 

availability, are important. Naturally occurring concentrations of silver have been reported from 

about 0.0002 to just over 1 μg/L in freshwater systems (Campbell et al., 2002). Elevated 

concentrations of silver in surface waters have generally been associated with wastewater 

treatment plant effluent discharges (Bell and Kramer, 1999). Based on the most recent Agency 

assessment of silver, EPA does not expect unreasonable adverse effects on the environment from 

registered uses, including the materials preservative use pattern (U.S. EPA, 1993). 

6.2.2 Aquatic Toxicity of Nanosilver 

Although no tests with NSPW-L30SS and aquatic organisms were submitted, there are studies in 

the scientific literature covering the toxicity of nanosilver to aquatic organisms (Table 17). These 

studies indicate to EPA that, if sufficient quantities of nanosilver break away from NSPW-L30SS 

and reach surface water, and if such nanoparticles display toxicity similar to the nanosilver used in 

these studies, then exposure of NSPW-L30SS derived nanosilver may result in adverse effects to 

aquatic species. These results also indicate that, of the organisms tested, Daphnia magna is the 

most acutely sensitive to nanosilver. As with the toxicity for silver ions, the toxicity of nanosilver 

may depend on the ligands or counter ions (e.g., Ca2+) present in the test media. For example, the 

LC50 reported by Laban et al. (2010) was up to 27 times greater than the LC50 reported by 

Kennedy et al. (2010) for the same organism where this difference may have been caused by the 

greater amount of calcium carbonate present in the work by Laban et al. (2010). Additionally, the 

D. magna results for the nanosilvers on a total-silver basis in Table 17 may be lower than expected 

when food or organic matter is present in the environment. In similar tests with silver salts, the 

acute LC50 is 3 to 40 times higher than acute tests where the daphnids are not fed during the test 

(EPA 1980, 1987; Ratte 1999). Standard acute test guidance for D. magna call for the daphnids to 

not be fed during testing and all of the D. magna studies listed in Table 17 were conducted in such 

a manner. 
43 

Table 17 – Nanosilver Toxicity to Aquatic Species 

Aquatic Organisms 

(Study Citation) Toxicity 

Silver 

Nitrate Nanosilver 

Totalsilver 

(μg/L) 

Totalsilver 

(μg/L) 

Dissolved 

Silver 

(μg/L) 

Water Characteristics 

Freshwater Algae, 

Raphidocelis subcapitata 

(Wang et al., 2012b) 

4.5-hr 

EC50

A 31.3 929-

120,000G

Not 

reported Dutch Standard Water 

(demineralized water with sodium 

bicarbonate, potassium 

bicarbonate, calcium chloride, and 

magnesium sulfate and then aerated 

for 24 h at 27 °C) 

Newborn Neonates of 

Freshwater Zooplankton, 

Chydorus sphaericus

(Wang et al., 2012b) 

48-hr 

EC50

4.3 36.7-

128.4G

Not 

reported 

Freshwater Fish Embryos, 

Danio rerio (Wang et al., 

2012b) 

96-hr 

EC50

78.8 88.4-

210.3G

Not 

reported 

D. magna (Kennedy et al., 

2010) 

96-hr 

LC50

B 1.2±0.5 1.8 to 

97.0C

0.3 to 

1.9C,D Moderately hard reconstituted 

water (MHRW), 80 mg/L as 

calcium carbonate 

Freshwater Fish Larval, 

Pimephales promelas 

(Kennedy et al., 2010) 

96-hr 

LC50

6.1±0.6 9.0 to 

125.6C

1.5 to 

5.6C,D

D. magna (Hoheisel et al., 

2012) 

48-hr 

LC50

0.98 4.3 to 

30.4E

Not 

reported 

Moderate ionic strength Lake 

Superior water 

D. magna (Asghari et al., 

2012) 

48-hr 

LC50

0.23 2 to 187E Not 

reported OECD 202 Media 

D. magna (Hoheisel et al., 

2012) 

24-hr 

LC50

0.81 4.3 to 

10.5E 3.5 to 8.1 MHRW, 96 mg/L as sodium bicarbonate 

Natural Bacterioplankton 

(Das et al., 2012) 48-hr 

EC50

Not 

reported 15 to 276 No reported 

EC50 values did not correlate with 

any of the basic limnological 

parameters 

Freshwater Fish Embryo, 

P. promelas (Laban et al., 

2010) 

96-hr 

LC50

15 9,400 to 

10,600 40 215 to 240 mg/L as calcium carbonate; pH 8.3 to 8.5 

Freshwater Fish Embryo, 

D. rerio (Wang et al., 

2012b) 

96-hr 

LC50

77 to 82 72 to 223G 0.7 to 22.3H Not reported 

A. EC50 (medium effect concentration): Concentration at which the response is halfway between the baseline and 

maximum after the specified exposure time. 

B. LC50 (median lethal concentration): Concentration required to kill half the tested population after the specified 

exposure. 

C. Range of eight different nanosilver formulations (see Table 18). 

D. Expressed as the fraction of suspended nanosilver. 

E. For nanosilvers with diameters from 10 to 50 nm (see Table 18). 

F. Range of three nanosilver formulations (see Table 18). 

G. Range of three different nanosilver formulations (see Table 18). 

H. Estimated 
44 

Table 18 – Reported Characteristics of Nanosilver Materials in the Aquatic Species Toxicity 

Studies 

Study Source Nano Material Shape Primary 

Size (nm) 

ζ-Potential 

(mV) 

Asghari et 

al., 2012 

ABC Nanotech Co., 

LTD 

SARPU 200 KWA (citrate 

capping agent), suspension 

spherical 7.32 Not reported 

Nano Nasb Pars 

Co., Ltd 

Nanocid L2000, suspension spherical 6.47 Not reported 

Xuzhou Hongwu 

Nanometer Material 

Co., Ltd 

Dry powder spherical 17.97 Not reported 

Das et al., 

2012 

Vive Nano, Toronto PN 3010L (20% Ag w/w, 

carboxy-functionalized 

polyacylate-capped), aqueous 

suspension 

Not 

reported 

1 to 10 Not reported 

Hoheisel 

et al., 

2012 

NanoComposix Aqueous suspensions in 2 mM 

phosphate buffer: 

 

10 nm spherical 10.2 Not reported 

20 nm spherical 20.3 Not reported 

30 nm spherical 34.4 Not reported 

50 nm spherical 53.1 Not reported 

Kennedy 

et al., 

2010 

NanoComposix MQ; 

MHRW5; 

MHRW24D

NC10 spherical 10 (cv = 

53%) 

-21 + 2; 5 + 

4; -8 + 3 

NC20 Mix of 

spheres 

and rods 

20 (cv = 

80%) 

-23 + 1; -1.7 

+ 0.1; -11 + 6

NC50 Mix of 

spheres 

rods 

49 (cv = 

46%)B

-34 + 1; -0.9 

+ 0.7; -21 + 1

NC80 spherical 50 (cv = 

35%) 

-20 + 1; -0.9 

+ 0.1; -24 + 2

Luna Innovations PVPC-coated spherical -15 + 1; -0.7 

+0.1; -6 + 4 

Virginia Tech Citrate dispersion Mix of 

spherical 

and rods 

29 (cv = 

57%); 

23 + 8 x 

150 + 47 

-46 + 3; -27 + 

1; -17 + 3 

EDTA dispersion spherical 36 

(cv = 35%) 

-33 + 1; -22 + 

2; 25 + 1 

American Biotech 

Laboratories 

Colloidal silver drink spherical 31 (cv = 

63%) 

Not reported 

Laban et 

al., 2010 

NanoAmor powder spherical 35 Not reported 

 Sigma-Aldrich powder spherical 21 to >300 

(>50% in 

21 to 60) 

Not measured
45 

Study Source Nano Material Shape Primary 

Size (nm) 

ζ-Potential 

(mV) 

Wang et 

al., 2012b 

Nanostructure & 

Amorphous 

Materials 

Powder, bare, 99.5% Ag spherical 35 

1000 and 10 

μM at pH 

7.0: 

-23.2 + 0.6, -

21.3 + 0.3 

Powder, PVP-coated ~0.3% 

PVP 

spherical 15 (90% 

<20) 

-24.1 + 1.2, -

20.6 + 1.5 

Joint Research 

Centre of the 

European Union 

monodispersed with dispersant 

(4% each of polyoxyethylene 

glycerol trioleate and 

polyoxyethylene sorbitan 

monolaurate) 

spherical 80 -10.3 + 1.0, -

13.9 + 1.5 

Wu and 

Zhou, 

2013 

Synthesized in the 

lab 

powder spherical 29.9 

(25.9-36.7) 

-43.4 

A. Reference material in OECD WPMN sponsorship program. 

B. Particles less than 5 nm were not included in primary diameter size; if included mean diameter is 12 nm (CV = 

96%). 

C. polyvinylpyrrolidone 

D. MQ = milli-Q water; MHRW5 = moderately hard reconstituted water after 5 minutes of media interaction; 

MHRW24 = moderately hard reconstituted water after 24 hours of media interaction 

Based on the studies listed in Table 17, the most sensitive aquatic species to nanosilver is Daphnia 

magna. The lowest 96-hr EC50 was 1.8 μg/L (Kennedy et al., 2010), which is 1.5 μg/L after 

subtracting the fraction of ionic silver present. This test was conducted in MHRW, which is a test 

medium representative of surface water in the United States. 

Although these studies are useful for indicating the concentration of nanosilver that might lead to 

effects in aquatic species, and to identify for this assessment an effect level for evaluating the 

ecotoxicity of nanosilver that could be released from plastics or textiles incorporating NSPWL30SS, the data represent short-term (e.g., 96 hr) acute exposures and do not characterize the 

effects from longer-term exposure to nanosilver. There is one long-term study on the effects of 

nanosilver on a freshwater fish (Oryzias latipes) that reported a no observed effect concentration 

(NOEC) of 100 μg/L based on the lethal effect observed at the concentration of 250 μg/L during a 

14-day subchronic exposure period (Wu and Zhou, 2013). Non-lethal effects (biomarker effects, 

histological lesions in the fish tissues along with silver accumulation in the liver) were reported for 

all nanosilver concentrations tested (50 to 500 μg/L). The study did not include any measurements 

of non-lethal apical endpoints (e.g., growth—length and/or dry weight) and there is no established 

model or relationship to predict from such data to apical non-lethal endpoints used in the risk 

assessment. While this is a longer-term study, it does not provide a lower apical endpoint for use 

in the risk assessment as the 14-d NOEC for lethality of 100 μg/L, on a total-silver basis, is about 

55 times higher than the lowest acute nanosilver endpoint (48-h EC50 of 1.8 μg/L) for the most 

acutely sensitive species, D. magna. In such a case use of the 14-d lethality NOEC for estimating 

chronic risks would underestimate the chronic risk to aquatic species. Non-apical endpoints are 

typically used in risk characterization, but again since this is not the most sensitive species, this 

information only provides evidence that there is potential for non-lethal apical endpoints in 

chronic studies to be affected at lower concentrations than where increased mortality is observed. 
46 

6.3 Aquatic Risk Assessment 

EPA expects that NSPW-L30SS, silver ions released from NSPW-L30SS, and nanosilver that 

might break away from NSPW-L30SS could enter the environment primarily through leaching of 

plastics and textiles incorporating NSPW-L30SS. 

Leaching of plastics and textiles incorporating NSPW-L30SS is anticipated to be the primary route 

by which NSPW-L30SS, silver ions, and nanosilver reach the environment. The silver released 

during leaching of plastics and textiles incorporating NSPW-L30SS could be discharged to the 

sanitary sewer system leading to publically owned wastewater treatment and privately owned 

septic systems, also known as the down-the-drain discharge scenario. Once NSPW-L30SS, silver 

ions, or nanosilver reach wastewater treatment and septic systems they will most likely complex 

with sulfide and partition to biosolids. However, some fraction of the silver compounds will reach 

surface water and may potentially impact aquatic organisms. Leaching of building material such as 

plastic siding and decks, and outdoor furniture and carpeting incorporating NSPW-L30SS will be 

discharged directly into the environment. 

As stated in Section 5.2.1, silver was not found above the analytical LOD leaching from plastic 

coupons and shirts incorporating NSPW-L30SS. EPA does not expect unreasonable adverse 

effects on the environment from registered uses of silver ions, including the materials preservative 

use pattern (U.S. EPA, 1993). To evaluate the impacts on surface water from leaching of NSPWL30SS from plastics and textiles, EPA is assuming that nanosilver as found in NSPW-L30SS is the 

only silver compound released. 

6.3.1 Aquatic Risk Quotient 

EPA uses a Risk Quotient (RQ) approach to assess impacts to surface water, which is similar to 

the MOE used for the human health risk assessment. The RQ is used to compare toxicity from 

environmental exposure by dividing a point estimate of exposure by a point estimate of effects. 

This ratio is a simple, screening-level estimate that identifies high- or low-risk situations. In this 

method, the estimated environmental concentration is compared to an effect level, such as an LC50. 

After the RQ is calculated, it is compared to EPA's Level of Concern (LOC). An LOC is a policy 

tool that EPA uses to interpret the RQ and to analyze potential risk to non-target organisms and the 

need to consider regulatory action (U.S. EPA, 2011c). Risks to aquatic organisms associated with 

two scenarios of in-service use of preserved textiles and plastics (an indoor textile use and an 

outdoor plastic lumber use) were used to screen for aquatic environmental loading of nanosilver 

from NSPW-L30SS and risks from all in-service uses of these materials listed on the label. Based 

on the results of the screening risk assessment, no further refinement of the environmental loading 

and risks by in-service use were conducted. 

Textile Use 

 Mass of silver release per year: 1123 kg/year. The amount of silver released from textiles 

incorporating NSPW-L30SS was derived assuming that 300 million people (U.S. 

population) purchase one t-shirt incorporating NSPW-L30SS each year. Each t-shirt 

weighs 150 grams and contains 0.003% nanosilver by weight silver and releases 1.6% 

silver per wash (see Section 5.2.1). 

 Release Weeks: Each t-shirt is washed once per week for 52 weeks/yr. 

 Wastewater Removal Efficiency: Ranged from 85 to 99% based on the range provided by 

Blaser et al. (2008). Wang et al. (2012a) reported nanosilver removal of 88% with biomass 

present. 
47 

 Speciation, Agglomeration and Sedimentation in the Surface Water Column: All of the 

silver released to surface water from a wastewater facility was assumed to be in the 

nanosilver form and it was assumed that all of the nanosilver was retained in the water 

column (i.e., no removal of released silver from the water column). The model used does 

not include these fate mechanisms and therefore surface water concentrations are expected 

be overestimated). 

Plastic lumber use 

 Mass of silver release per year: 570 kg/year. The amount of silver released from plastics 

incorporating NSPW-L30SS was derived assuming that 1% of the yearly plastic lumber 

production contains NSPW-L30SS at 0.003%. Yearly plastic lumber production for 2006 

was projected to be approximately 1900 million kg/yr (Stutz et al., 2003). This assumes 

that all the nanosilver in plastic incorporating NSPW-L30SS is released during a year even 

though results from the plastic leaching study indicate that little silver is released from 

plastic incorporating NSPW-L30SS (i.e., <0.042% in 10 days, see Section 5.2.1) and that 

this release is likely even lower in less porous plastics than the LLDPE plastic used in the 

study. 

 Release Days: 365 days per year. This assumes that each plastic incorporating NSPWL30SS releases all its silver as nanosilver over the course of one year (i.e., 0.274% leaches 

out per day) even though not all in-service plastic lumber will be in contact with water 

every day. 

 Wastewater Removal Efficiency: 0% to represent direct release into aquatic environments 

from the plastic lumber use of plastics incorporating NSPW-L30SS (i.e., no removal of 

nanosilver in the run-off due to adsorption to soil). 

 Speciation, Agglomeration and Sedimentation in the Surface Water Column: All of the 

silver released to surface water from a wastewater facility was assumed to be in the 

nanosilver form and it was assumed that all of the nanosilver was retained in the water 

column (i.e., no removal of released silver from the water column). The model used does 

not include these fate mechanisms and therefore surface water concentrations are expected 

be overestimated). 

Down the Drain Model 

The concentration of nanosilver in surface water resulting from the use of NSPW-L30SS in 

plastics was calculated using the Down the Drain Module of the Exposure and Fate Assessment 

Screening Tool (E-FAST model, version 2). The following input values were used: 

 Stream Dilution Factor: 1.0 or 20.1. These values are the 10th and 50th percentile values for 

the dilution that occurs during one day of lowest stream flow over a ten year period (1Q10) 

(U.S. EPA, 2007b). 

 The toxicity value for nanosilver: 1.5 μg/L based on the 96-hr EC50 value for Daphnia 

magna. 

 Level of Concern for the RQ: The presumptive acute level of concern (LOC) is 0.05 for 

listed (i.e., endangered or threatened) aquatic animals and 0.5 for non-listed animals. 
48 

Table 19 – Risk Quotients for Nanosilver in Surface Water 

Use 

Scenario 

Wastewater 

Treatment 

RemovalA 

Stream 

Dilution 

Factor 

Surface Water Silver 

Concentration (μg/L) 

Acute Risk 

QuotientD

Acute RQ 

Exceeds 

LOC?* 

Textiles 

(t-shirts) 85% 1.0B 0.004 0.003 No 

20.1C 0.0002 0.0001 No 

Plastics 

 (lumber) 0%E 1.0 0.014 0.009 No 

20.1 0.001 0.0007 No 

*The presumptive acute LOC is 0.05 for listed animal species and 0.5 for non-listed animal species. 

A. Silver removed from wastewater during treatment before discharge to a water body (e.g., lake, river etc.). 

B. 10th Percentile dilution factor for 1Q10 stream flow. 

C. 50th Percentile dilution factor for 1Q10 stream flow. 

D. Acute RQ = Surface Water Concentration / 96-h EC50 for D. magna (1.5 μg/liter) 

E. Assumes direct discharge to surface water with no retention in soil or sediment. 

The down-the-drain modeling results are shown in Table 19 and these results were divided by the 

96-hr EC50 of 1.5 μg/L for D. magna to obtain acute risk quotients (RQs). The effect level used to 

calculate the acute RQs (i.e., 1.5 ug/L) was chosen to represent the most sensitive aquatic 

organism D. magna and to represent conditions that are representative of surface water in the 

United States. The acute RQ of 0.009 at the worst-case stream dilution factor of 1.0 indicates that 

it is unlikely that the registration of NSPW-L30SS as a plastics and textiles preservative will lead 

to adverse effects for listed or non-listed aquatic organisms during the four year period of 

conditional registration. However, this assessment does not consider long-term exposures or 

exposure to estuarine and marine species. 

6.3.2 Conclusions for Aquatic Risk 

The acute RQs for D. magna exposed to nanosilver ranged from 0.0001 to 0.009, which are not of 

concern for listed or non-listed organisms because they were less than the acute LOC of 0.5 and 

0.05, respectively. The effect level used to calculate the acute RQs (i.e., 1.5 μg/L) was chosen to 

represent the most sensitive aquatic organism D. magna and to represent conditions of MHRW, 

which is a test medium representative of surface water in the United States. 

This analysis assumes that 1% of the projected yearly production of plastic lumber in the U.S. 

would contain NSPW-L30SS at 0.003% resulting in a nanosilver production-volume of 570 

kg/year. This is likely an overestimate given that the total mass of silver distributed as a material 

preservative in the U.S. during 2009 was less than 6,800 kg, based on EPA records. This analysis 

also assumes that all the nanosilver in plastic lumber incorporating NSPW-L30SS would be 

released into the environment during a one year period (i.e., 0.274% leaches out per day) when in 

fact the silver in the leaching study for plastic coupons was below the analytical LOD indicating 

that significantly less silver would be released from plastic lumber incorporating NSPW-L30SS 

(see Section 5.2.1; <0.042% would leach out in 10 days or <0.0042% daily). This assumption also 

requires nanosilver to migrate from the interior of the plastic at the same or higher rate daily from 

the interior to the exterior of the plastic lumber to replenish nanosilver for leaching availability the 

next day. 

There are several uncertainties regarding the exposure portion of this evaluation. The production 

volume of NSPW-L30SS is unknown since this product is not currently available in the U.S. 

Because of this, EPA made the assumption that 1% of all plastic lumber produced every year in 

the U.S. would contain 0.003% NSPW-L30SS. The nanosilver that could be released from the 

lumber incorporating NSPW-L30SS was assumed to directly enter the aquatic environment 

without any removal in soil or sediments. The rate at which nanosilver entered the sanitary sewer 
49 

systems was assumed to be constant in the down-the-drain model, which does not account for 

variability in the distribution of plastic products incorporating NSPW-L30SS among other factors. 

The ecotoxicity values shown in Table 17 are for acute effects and mortality, and there is only one 

study on the long-term exposure to nanosilver. The longer-term exposure study is not with a 

sensitive aquatic species and does not provide a chronic apical endpoint lower than the acute data 

used in the risk assessment for the most acutely sensitive species. Exposure models did not 

account for reduction in exposure due to removal and sorption of nanosilver particles to organic 

matter in the water column. 

The acute daphnid results in Table 17 are from tests where the daphnids were not fed during the 

study per standard test guidance for this species (e.g., OPPTS 850.1010, OECD 202). In tests with 

silver salts, chronic NOEC endpoints on a total-silver basis for daphnid have been found to be 

higher than acute endpoints, this has been attributed to the presence of food in the long-term 

exposure studies as compared to the acute (USEPA Ambient Water Quality Criteria for Copper 

1980, 1987). When daphnids are fed during the silver salt acute tests, acute toxicity has been 

observed to be reduced (2.9 to 40 times less toxic) (USEPA 1980). Similar decreases in acute 

toxicity have been observed for other sensitive cladoceran species (Ceriodaphnia reticulata, 

Daphnia pulex) when fed (USEPA 1987). While EPA has not reviewed more current public 

literature on acute toxicity for silver salts for acceptability for use in a risk assessment, open 

literature reviews of available silver toxicity data based on total recoverable silver demonstrate this 

pattern has also been observed in later studies with D. magna. (Ratte 1999). This difference has 

been attributed to the presence of food providing a mitigating effect (i.e., food binds silver, 

rendering it less bioavailable). Organic matter in the water column may potentially reduce the 

acute toxicity, on a total recoverable silver basis, of nanosilver. 

Given that all calculated RQs were below the presumptive LOC for listed species and the 

conservative assumptions used in calculating these RQs, EPA concludes, with a level of 

confidence acceptable for the period of conditional registration, that there is a low probability of 

adverse risk to the environment from plastics and textiles incorporating NSPW-L30SS. 

6.4 Ecological Effects and Environmental Fate Data Requirements. 

Even though EPA does not anticipate adverse ecological effects from plastics and textiles 

incorporating NSPW-L30SS during the period of conditional registration, EPA is requesting 

additional testing to confirm its conclusions. The testing is based on a tiered approach. Tier I 

studies will determine the nature and quantity of silver released from plastics incorporating 

NSPW-L30SS and confirm that the nanosilver in NSPW-L30SS is consistent with the risk from 

Table 19. The Tier I environmental fate testing categories include: 

 NSPW-L30SS Characterization Testing 

 Release Characteristics/Exposure which includes Silver Release from Plastics: Form, Rate 

and Characteristics 

The Tier I effects testing categories to confirm assumptions and include: 

 Health Effects (Inhalation Studies) 

 Ecological Effects (acute daphnid study). 

Completion of these Tier I studies will provide NSPW-L30SS product characteristics and 

determine the substance or substances released during leaching of plastics incorporating NSPWL30SS. Information from these studies will be used to substantiate NSPW-L30SS’s claim that no 

nanosilver is released from plastics incorporating NSPW-L30SS during use. However, if 
50 

nanosilver is found to be released during Tier I studies, and the RQ calculated using this release 

rate results in a risk concern or is within one order of magnitude of the LOC, then Tier II studies 

will be required. If necessary, the Tier II studies will provide quantitative toxicity data on the 

amounts and forms of silver released, which will then be used by EPA to re-run the environmental 

risk assessment for NSPW-L30SS. The Tier II environmental fate and ecological effects testing 

categories include: 

 Product Characterization 

 Sorption/Desorption Characteristics 

 Bioaccumulation Characteristics 

 Impacts to Wastewater Treatment 

 Wastewater Treatment Removal Efficiency 

 Aquatic Plant testing 

 Acute Effects to Freshwater Fish 

 Chronic Effects to Freshwater Fish and Invertebrates 

 Acute and Chronic Effects to Estuarine/Marine Animals 

 Chronic Effects to Sediment Dwelling Organisms 

 Terrestrial Plant Toxicity 

A more detailed description of these data requirements is provided in Appendix B. 

VII. Regulatory Action 

A registration for a new active ingredient may be granted under either section 3(c)(5) or section 

3(c)(7)(C) of FIFRA. A FIFRA section 3(c)(7)(C) registration is appropriate where, as here, the 

data for registration of the new active ingredient are newly required or identified as needing 

adaptation to fit nanosilver. As discussed more thoroughly below, because EPA had not reached a 

final decision with regard to which types of data would be further required, the data requirements 

for this registration are considered newly required. 

In addition, we believe granting the conditional registration with the terms and conditions 

identified in Appendix B is particularly appropriate given EPA suspects that some alreadyregistered like-situated products on the market contain nanosilver as the active ingredient. While 

EPA approved these registrations without knowledge that these products may 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 and consistent with the analytic decision framework in this document, EPA is seeking 

similar data along with comparable terms on already registered products that are identified to 

contain nanosilver. As part of this effort, EPA opened the Nanosilver Registration Review (docket 

EPA-HQ-OPP-2011-0370) on July 6, 2012, which is the first step towards issuing a Data Call-In 

for products containing nanosilver. 

7.1 Legal Framework 

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) section 3(c)(7)(C) provides that: 

The Administrator may conditionally register a pesticide containing an active ingredient not 

contained in any currently registered pesticide for a period reasonably sufficient for the 

generation and submission of required data (which are lacking because a period reasonably 

sufficient for generation of the data has not elapsed since the Administrator first imposed the 

data requirement) on the condition that by the end of such period the Administrator receives 

such data and the data do not meet or exceed risk criteria enumerated in regulations issued 
51 

under this Act, and on such other conditions as the Administrator may prescribe. A conditional 

registration under this subparagraph shall be granted only if the Administrator determines that 

use of the pesticide during such period will not cause any unreasonable adverse effect on the 

environment and that use of the pesticide is in the public interest. 

Therefore, EPA must make four findings in order to grant a section 3(c)(7)(C) conditional 

registration for a pesticide product containing a new active ingredient: 

1. NSPW-L30SS contains nanosilver as an active ingredient and the nanosilver in NSPWL30SS is not in any currently registered pesticide; 

2. Use of NSPW-L30SS will not cause unreasonable adverse effects on the environment 

during the period when newly required data are being developed; 

3. Insufficient time has elapsed for the newly required data to be generated and submitted; 

and 

4. Use of NSPW-L30SS is in the public interest. 

7.2 Findings and Registration Decision 

EPA is granting a conditional, four year registration for NSPW-L30SS in accordance with FIFRA 

section 3(c)(7)(C) and is requiring as a condition of registration specified use conditions as well as 

data from a number of studies that will allow EPA to refine its current assessment of the risks. 

Specific data requirements are outlined in Appendix B. Although these data requirements are 

specific to NSPW-L30SS, they form a starting point for identifying the types of data EPA will 

require for other nanomaterial-based products on a case-by-case basis. 

Consistent with Nanosilva LLC’s application, label language is required to reduce potential 

exposures. The pesticide label must include the following: 

1. The application rate must be less than 30 ppm (mg/kg) or 0.003% silver on a weight basis 

for plastics and textiles which incorporate NSPW-L30SS. 

2. NSPW-L30SS may only be incorporated into linear low-density polyethylene (LLDPE) 

plastic and polyethylene terephthalate (PET) based textiles consistent with the materials 

used in the leaching studies. 

3. NSPW-L30SS may only be used to preserve plastics and textiles and may not be used for 

drinking water or food contact uses. 

4. It is required that the following mitigation measures be employed when mixing and loading 

NSPW-L30SS during treatment of articles: 

 Closed system loading of NSPW-L30SS containing suspension. 

 NIOSH certified full-face respirators with P100 or equivalent filter cartridges 

immediately available for use in an emergency. 

 Gloves which are chemically resistant to all of the components of the NSPWL30SS liquid suspension. 

 A long-sleeve shirt, long pants, shoes plus socks. 

5. The label must have an environmental hazard statement consisting of the following: 

“This pesticide is toxic to fish, aquatic invertebrates, and birds. Do not discharge 

effluent containing this product into lakes, streams, ponds, estuaries, oceans, or 

other waters unless in accordance with the requirements of a National Pollutant 

Discharge Elimination System (NPDES) permit and the permitting authority has 

been notified in writing prior to discharge. Do not discharge effluent containing this 

product to sewer systems without previously notifying the local sewage treatment 
52 

plant authority. For guidance contact your State Water Board or Regional Office of 

the EPA.” 

7.3 Basis for Conditional Registration 

EPA’s basis for the conditional registration is as follows: 

7.3.1 Data Generation 

Nanosilva LLC submitted its registration application thinking its product was a new pesticide 

ingredient not contained in any currently registered silver-based pesticide product and should be 

given a registration under FIFRA section 3(c)(5). At the time of application for a new chemical, 

Nanosilva LLC was required to submit all the applicable information and studies under 40 CFR 

161. Although Nanosilva LLC submitted some of the required studies using guidelines not 

modified to be applicable for testing nanosilver, they also submitted a request to waive some of the 

data requirements. In addition, Nanosilva LLC completed a leaching study using a protocol that 

was modified to be applicable for nanosilver. Although Nanosilva LLC provided EPA with some 

data in an effort to address Agency questions and concerns, EPA had not reached a final decision 

with regard to which types of data would be further required for NSPW-L30SS. This was due in 

large part to the need to understand and apply the advice provided in the report from the 

consultation with the FIFRA Scientific Advisory Panel. As a result, EPA has determined that 

insufficient time has elapsed from the point at which EPA determined and informed Nanosilva 

LLC of the data requirements needed to assess Nanosilva LLC’s application for Nanosilva LLC to 

have generated the data. 

EPA is requiring the tests listed below to account for potential physiochemical differences of the 

nanosilver and because there are currently no acceptable studies on the reproductive and 

developmental toxicity for nanosilver. Because this list of data requirements are only being 

imposed with today’s action, Nanosilva LLC has not yet been able to conduct these studies. 

Therefore, EPA is requiring these studies as a condition of registration, allowing sufficient time for 

the study protocols to be agreed upon, the studies to be conducted, and for EPA to review them. 

The required studies are: 

 90-Day Inhalation Toxicity (Rat) (OCSPP GLN 870.3465) modified to include a functional 

observational battery, motor activity and detailed neuropathology 

 Reproduction/Developmental Toxicity Screening Test via the inhalation route. (Modified 

OCSPP GLN 870.3550/ OECD TG 421) 

 Acute Freshwater Invertebrate Testing using Daphnia magna

 Product Characterization and Testing 

 Dissolution Kinetics 

 Silver Release from Plastics: Form, Rate and Characteristics 

EPA will evaluate the results from the above studies using a weight of evidence approach based on 

physical and chemical properties, toxicity, and exposure. If EPA identifies a possible concern, then 

one or a combination of the following tests will be triggered: 

 Peri- and post-natal exposure to NSPW-L30SS 

 Product Characterization 

 Sorption/Desorption Characteristics 

 Bioaccumulation Characteristics 

 Impacts to Wastewater Treatment 

 Wastewater Treatment Removal Efficiency 
53 

 Aquatic Plant testing 

 Acute Effects to Freshwater Fish 

 Chronic Effects to Freshwater Fish and Invertebrates 

 Acute and Chronic Effects to Estuarine/Marine Animals 

 Chronic Effects to Sediment Dwelling Organisms 

 Terrestrial Plant Toxicity 

As discussed above, a listing of the studies that are required as terms and conditions of this 

registration of NSPW-L30SS are in Appendix B. If Nanosilva LLC does not meet the conditions 

set forth in this Decision Document, EPA will issue a notice of intent to cancel Nanosilva LLC’s 

registration under section 6(e). In addition, Nanosilva LLC’s conditional registration for NSPWL30SS will automatically expire four years after being issued. Nanosilva LLC should request an 

amendment to remove the expiration date once they have submitted the required data if they wish 

to continue to sell and distribute NSPW-L30SS in the United States. 

7.3.2 Public Interest 

As required under FIFRA section 3(c)(7)(C), for the reasons summarized below, EPA believes 

granting a conditional registration with the terms and conditions specified is in the public interest. 

Concluding that granting the registration is in the public interest is not an endorsement of the 

product. Under its authority set forth in FIFRA section 3(c)(7)(C), EPA is making only a public 

interest finding, which is provided for informational purposes only and not to be inferred as any 

endorsement of a pesticide product. EPA and its employees do not endorse any particular product, 

service or enterprise. If any registrant were to include "any statement directly or indirectly 

implying that the pesticide or device is recommended or endorsed by any agency of the Federal 

Government," then such statement, pursuant to 40 CFR 156.10(a)(5)(v), would be false or 

misleading. EPA believes that use of NSPW-L30SS offers the potential for conservation of the 

environment which contribute to the public interest. These points are discussed in more detail 

below: 

Conservation of the Environment 

EPA has already registered a number of silver-based pesticide products for use as materials 

preservatives. All silver-based pesticide products act via the release of a low concentration of 

silver ions that then interact with bacteria. Commonly, regardless of the silver additive type, upon 

contact with moisture, silver ions are released from the object incorporating the additive. The 

antimicrobial potency of a silver additive is therefore directly related to the potential for releasing 

silver ions. The release potential differs between various silver materials. As the size of silver 

particles decreases (e.g., from micro-size silver to nano-size silver), the potential for releasing 

silver ions increases, due to the increasing unit of surface area (i.e., availability of ions for release) 

per unit mass of silver. 

Specifically, most silver-based pesticide products currently contain a silver salt, [e.g., AgCl or 

AgNO3]. Compared to the amount of silver in Nanosilva LLC’s product, most currently registered 

silver-based materials preservatives incorporate larger amounts of silver (i.e., NSPW-L30SS is 

applied at a lower rate). 

Furthermore, the nanosilver in NSPW-L30SS is complexed to a larger particle that is then 

embedded into a polymer. The submitted leaching studies show that nanosilver is unlikely to be 

released in quantities above the detection limit from this polymer. Absent release from the 

polymer, the mobility of nanosilver in NSPW-L30SS is greatly reduced. Taking into consideration 
54 

the low application rates, low mobility, and the expected gradual and controlled release of silver 

ions from nanosilver as opposed to the rapid release of silver ions from a zeolite structure or the 

immediate dissolution of a silver salt, EPA believes there is potential for reduced environmental 

loading and likely reduced environmental risk. 

7.3.3 No Unreasonable Adverse Effects 

In assessing the potential risks to human health and the environment associated with the 

distribution and use of NSPW-L30SS as a materials preservative, EPA relied on data submitted by 

Nanosilva LLC and data in the public literature on nanosilver, and use of uncertainty factors and 

conservative assumptions. As a result of this analysis and taking into account the terms and 

conditions on this conditional registration, EPA believes that the likely risks from the use of 

NSPW-L30SS during the period of the conditional registration are small. Moreover, EPA expects 

the overall quantity of silver used in plastics and textiles as a result of this conditional registration 

will be lower than the overall quantity of silver used in other materials preservative products 

containing conventional silver resulting in expected reductions in environmental loadings of silver 

and to humans. EPA concludes that the registration would not cause unreasonable adverse effects 

on the environment during the conditional period. This conclusion is based on the findings 

discussed in the following sections. 

Risks to Human Health

As discussed above, humans could be exposed to silver ions, to NSPW-L30SS, and to nanosilver 

released from NSPW-L30SS. With respect to silver ions, EPA completed a risk assessment (U.S. 

EPA, 1993) for silver salts and determined that the risks from registered uses, including the 

materials preservative use pattern, were acceptable. EPA concludes that human exposure to silver 

ions from the use of NSPW-L30SS and consumer exposures to plastics and textiles incorporating 

NSPW-L30SS is not unreasonable. 

With respect to NSPW-L30SS, the acute toxicity of NSPW-L30SS is low by all routes of 

exposure. Because there are no subchronic or chronic oral or dermal toxicity studies available for 

NSPW-L30SS or on the nanosilver that might break away from products incorporating NSPWL30SS, the subchronic or chronic toxicities were estimated using studies on nanosilvers reported 

in the literature. Because of the potential difference between the nanosilver in the available 

toxicity data and the nanosilver in NSPW-L30SS along with the lack of an acceptable 

developmental and reproductive toxicity study for nanosilver, EPA used a maximum 10-fold 

database uncertainty factor when evaluating the risk from exposure to NSPW-L30SS and the 

nanosilver released from products incorporating NSPW-L30SS. 

To evaluate occupational exposure to the nanosilver that might break away from NSPW-L30SS, 

EPA calculated the daily-dose to workers assuming that all the silver in NSPW-L30SS was freely 

available as nanosilver. EPA believes that this assumption overestimates the daily-dose of 

nanosilver that a person could potentially receive when working with NSPW-L30SS. 

To assess consumer exposures to treated textiles and plastics, EPA relied on the results from 

studies submitted by Nanosilva LLC where the liquids in contact with plastic and shirts 

incorporating NSPW-L30SS were analyzed for silver content to estimate exposure the amount of 

NSPW-L30SS and nanosilver that might be released from plastics and textiles. EPA recognized 

the uncertainties and incorporated multiple uncertainty factors and conservative assumptions when 

calculating the Margin of Exposures (MOEs) for estimating the risk to children from plastics and 

textiles incorporating NSPW-L30SS. 
55 

Based on all of the foregoing, EPA concludes that use of NSPW-L30SS will not cause 

unreasonable adverse effects on the environment during the period when newly required data are 

being developed. 

Risks to the Environment 

The environment could be exposed to silver ions, to NSPW-L30SS, and to nanosilver released 

from NSPW-L30SS. With respect to silver ions, EPA completed a risk assessment (U.S. EPA, 

1993) for silver salts and determined that the risks from registered uses, including the materials 

preservative use pattern, were acceptable. EPA concludes that environmental exposure to silver 

ions from the use of NSPW-L30SS and plastics and textiles incorporating NSPW-L30SS is 

acceptable. 

With respect to the fate and ecotoxicity of NSPW-L30SS, because there are no fate or ecotoxicity 

studies available for NSPW-L30SS or the nanosilver that might break away from plastics or 

textiles incorporating NSPW-L30SS, the fate and ecotoxicity were estimated using studies on 

nanosilvers reported in the scientific literature. Direct release from leaching of plastics and 

laundering of textiles incorporating NSPW-L30SS were anticipated to be the primary route by 

which NSPW-L30SS, silver ions, and nanosilver reach the environment. EPA assessed impacts to 

surface waters assuming that nanosilver was the only compound released. Environmental exposure 

from indoor use was assessed assuming that 300 million people (U.S. population) each purchased 

one t-shirt containing 0.003% nanosilver where 1.6% of the silver in the t-shirt incorporating 

NSPW-L30SS was released during each weekly washing over a one year period. Environmental 

exposure from plastic lumber use was assessed assuming that 1% of the projected yearly 

production of plastic lumber in the U.S. would contain NSPW-L30SS at 0.003% where all the 

silver would be released into the environment as nanosilver during a one year period even though 

silver was released below the LOD in the leaching study for plastic coupons incorporating NSPWL30SS. EPA estimates, derived from modeling, of the concentrations of nanosilver resulting from 

the use of NSPW-L30SS do not exceed EPA’s estimate of the highest concentration of nanosilver 

in surface water to which an aquatic community can be exposed without resulting in an 

unacceptable effect. Thus, EPA concludes that use of NSPW-L30SS will not cause unreasonable 

adverse effects on the environment during the period when newly required data are being 

developed. 
56 

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Li, Y., Bhalli, J.A., Ding, W., et al. (2013) Cytotoxicity and genotoxicity assessment of silver 

nanoparticles in mouse. National Center for Toxicological Research, USFDA, MRID 

49291901. Nanotoxicology, early online 

Liu P, Huang Z, and Gu N 2013. Exposure to silver nanoparticles does not affect cognitive 

outcome or hippocampal neurogenesis in adult mice. Ecotoxicol Environ Saf. Jan;87:124-

30. doi: 10.1016/j.ecoenv.2012.10.014. Epub 2012 Nov 10. 

Liu Y, Guan W, and Ren G, et al. 2012. The possible mechanism of silver nanoparticle impact on 

hippocampal synaptic plasticity and spatial cognition in rats. Toxicology Letters, 209: 227-

231. 

Liu, J., Hurt, R.H. 2010. Ion Release Kinetics and Particle Persistence in Aqueous Nano-silver 

Colloids. Environmental Science Technology 44:2169-2175. 

Liu, J., Sonshine, D.A., Shervani, S., Hurt, R.H. 2010. Controlled Release of Biologically Active 

Silver from Nanosilver Surfaces. ACS Nano 4:6903-6913. 

Liu, Z., Ren, G., Zhang, T., Yang, Z. 2009. Action Potential Changes Associated with the 

Inhibitory Effects on Voltage-Gated Sodium Current of Hippocampal CA1 Neurons by 

Silver Nanoparticles. Toxicology 264(3):179-84. 

Loeschner et al. 2011. Distribution of silver in rats following 28 days of repeated oral exposure to 

silver nanoparticles or silver acetate. Particle and Fibre Toxicology, 8:18 

Lorenz, C., Windler, L., von Goetz, N. et al. 2012. Characterization of silver release from 

commercially available functional (nano) textiles. Chemosphere 89:817-824. 

Mahabady, M.K. 2012. The evaluation of teratogenicity of nanosilver on skeletal system and 

placenta of rat fetuses in prenatal period. African Journal of Pharmacy and Pharmacology

6: 419-424. 

Moiemen, N.S., Shale, E., Drysdale, K.J., et al. 2011. Acticoat dressing and major burns: Systemic 

silver absorption. Burns 37:27-35. 

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Cells. Environmental and Molecular Mutagenesis 53: 409-419. 

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into the Effects of Silver Nanoparticles on Antibiotic Resistance of Naturally Occurring 

Bacteria in an Estuarine Sediment. Marine Environmental Research 68:278-283. 
59 

NIOSH. 2009. Approaches to Safe Nanotechnology: Managing the Safety and Health Concerns 

Associated with Engineered Nanomaterials. DHHS (NIOSH) Publication No. 2009-125 

Park, E.J., Bae, E., Yi, J., et al. 2010. Repeated-Dose Toxicity and Inflammatory Responses in 

Mice by Oral Administration of Silver Nanoparticles. Environmental Toxicology and 

Pharmacology 30: 162-168. 

Ratte, H. 1999. Bioaccumulation and toxicity of silver compounds: a review. Environmental 

Toxicology and Chemistry 18(1): 89-108. 

Song et al. 2012. Recovery from silver-nanoparticle-exposure-induced lung inflammation and lung 

function changes in Sprague-Dawley rats. Nanotoxicology

doi:10.3109/17435390.2011.648223 

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Institute, Boston, MA. Available at: 

www.epa.gov/osw/conserve/rrr/greenscapes/pubs/lumber.pdf 

Sung, J.H., Ji, J.H., Park, J. D., et al. 2009. Subchronic Inhalation Toxicity of Silver Nanoparticles.

Toxicological Sciences 108:452-461. (MRID 477575-05) 

Tang, J., Xiong, L., Wang, S. et al. 2009. Distribution, translocation, and accumulation of silver 

nanoparticles in rats. J. Nanoscience Nanotechnology 9(8):4924-32. 

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Available at: http://characterizationmatters.files.wordpress.com/2008/11/mincharparameters-list.pdf 

Trop, M., Novak, M., Rodl, S. et al., 2006. Silver-Coated Dressing Acticoat Caused Raised Liver 

Enzymes and Argyria-like Symptoms in Burn Patient. Journal of Trauma-Injury Infection 

and Critical Care 60:648-652. 

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Silver Ions in Rats after 28-Day Oral Exposure. ACS Nano DOI: 10.1021/nn302649p. 

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Standards, Criteria and Standards Division, Washington, DC. EPA 440/5-80-071. 

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Development, Environmental Research Laboratories, Duluth, MN and Narragansett, RI. 

EPA 440/5-87-011. 

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Programs, June 1993. 

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1998, available at: http://www.epa.gov/pesticides/science/phedsur-expo-guide.pdf

U.S. EPA, 2000. Assigning Values to Non-Detected/Non-Quantified Pesticide Residues in Human 

Health Food Exposure Assessments. Available at: 

http://www.epa.gov/pesticides/trac/science/trac3b012.pdf 

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November 28, 2001. Available at: 

http://www.epa.gov/opp00001/trac/science/aggregate.pdf

U.S. EPA, 2002. A review of the Reference Dose and Reference Concentration Processes. 

EPA/630/P-02/002F. December. 

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Exposures to Environmental Contaminants. EPA/630/P-03/003F. November, 2005. 

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EPA SW846: Test Methods for Evaluating Solid Waste, Physical/Chemical Methods. 

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Documentation Manual. October, 2007. Available at: 
60 

http://www.epa.gov/oppt/exposure/pubs/efast2man.pdf 

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Preservative in Textiles. December 1, 2011. 

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2011. 

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Risk Presumptions for Aquatic Animals. Available at: 

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2012-public-meeting/AEATF-Liquid-Pour-Study.pdf 

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Health Effects Division, Office of Pesticide Programs, Office of Chemical Safety and 

Pollution Prevention. 

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at: http://www.epa.gov/pesticides/regulating/part158-tox-data-requirement.pdf

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and Tissues of Volunteers and Burn Patients. Clinical Chemistry 37:1681-1687. 

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Binding and RNA Transcription Inhibition in Erythroid Progenitor Cells. ACS Nano 7: 

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dioxide, and C60 (fullerene) nanomaterials during simulated wastewater treatment 

processes. Journal of Hazardous Materials 201-202:16-22 

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Trophic Organisms: Contributions of Particles and Free Silver Ion. Environmental 

Toxicology and Chemistry 31: 2408-2413. 

Wigginton, N.S., De Titta, A., Piccapietra, F., et al. 2010. Binding of Silver Nanoparticles to 

Bacterial Proteins Depends on Surface Modifications and Inhibits Enzymatic Activity. 

Environmental Science Technology 44:2163. 

Wu, Y., Zhou, Q. 2012. Silver Nanoparticles Cause Oxidative Damage and Histological Changes 

in Medaka (Oryzias latipes) after 14 days of Exposure. Environmental Toxicology and 

Chemistry, 32:165-173. 

Yang, Y., Chen, Q., Wall, J.D., Hu, Z. 2012. Potential nanosilver impact on anaerobic digestion at 

moderate silver concentrations. Water Research 46: 1176-1187. 

Yu, Wook-Joon, Son, Jung-Mo, Lee, Jinsoo, et al. (2013) Effects of silver nanoparticles on 

pregnant dams and embryo-fetal development in rats. Korea Institute of Toxicology, MRID 

49291902. Nanotoxicology early online: 1-7. 

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Probabilistic Exposure Assessment for Children Who Contact CCA-treated Playsets and 

Decks Using the Stochastic Human Exposure and Dose Simulation Model for the Wood 

Preservative Scenario (SHEDS-WOOD). Final Report. U.S. EPA, Washington, DC, 

EPA/600/X-05/009. 
61 

Appendix A – Evaluation of Nanosilva LLC’s Data Waiver Requests 

I. Introduction 

On August 10, 2009, Nanosilva LLC submitted an application to register NSPW-L30SS with a 

new nanosilver active ingredient (PRIA A420). In 2009, as an applicant for registration of a new 

active ingredient, Nanosilva LLC was required to submit all the applicable information and studies 

under 40 CFR part 161. EPA published a Notice of Proposed Rulemaking on October 8, 2008 

proposing to revise and update the existing data requirements under 40 CFR part 161 for 

antimicrobial pesticides. These data requirements were made final as 40 CFR part 158W on May 

8, 2013 (78 FR 26936). In 2009, the Nanosilva LLC application included a request to waive the 

requirement to generate data for NSPW-L30SS using the following test guidelines: 

1. Hydrolysis (OCSPP GLN 835.2120) 

2. Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids (OCSPP GLN 850.1010) 

3. Fish Acute Toxicity Test, Freshwater and Marine (OCSPP GLN 850.1075) 

4. Avian Acute Oral Toxicity Test (OCSPP GLN 850.2100) 

5. 90-Day Dermal Toxicity (OCSPP GLN 870.3250) 

6. Prenatal Developmental Toxicity Study ( OCSPP GLN 870.3700) 

7. Bacterial Reverse Mutation Test (OCSPP GLN 870.5100) 

8. Detection of Gene Mutations in Somatic Cells in Culture (OCSPP GLN 870.5300) 

9. in vitro Mammalian Cytogenetics (OCSPP GLN 870.5375) 

10. Mammalian Bone Marrow Chromosome Aberration Test (OCSPP GLN 870.5385) 

11. Immunotoxicity (OCSPP GLN 870.7800) 

The test guidelines in items 1 through 4 were required in 40 CFR part 161 at the time Nanosilva 

LLC applied to register NSPW-L30SS. Guidelines in items 5 through 11 were proposed in 2008 to 

be included in 40 CFR part 158W, which was finalized in 2013 and therefore, the test guidelines in 

items 5 through 11 were not required at the time Nanosilva LLC applied to register NSPW-L30SS. 

Even though these guidelines were not required at the time of application, EPA evaluated the 

request to waive each of these data requirements. 

Waivers for the above studies were requested because of the lack of acute toxicity noted in the six 

acute toxicity studies (MRID 47828918 through 47828923), because NSPW-L30SS has a specific 

gravity greater than water, because NSPW-L30SS has low solubility in water as determined by the 

water column generator method (MRID 47828917), and due to the non-leaching characteristic of 

NSPW-L30SS because silver leached below the LOD in leaching studies conducted with a plastic 

incorporating NSPW-L30SS (MRID 47828925). 

The data requirements listed above in item 1 and in items 3 through 11 are either waived or 

satisfied. In general, the data requirement is waived or satisfied because: 

 certain guideline studies are not appropriate for nanosilver and where appropriate are being 

modified and required as terms and conditions on the registration 

 certain environmental data requirements are satisfied by using literature studies 

 additional dermal studies are not needed based on calculated margins of exposure (MOEs) 

 in vitro and in vivo mutagenicity study requirements are satisfied and there is no concern 

for mutagenicity or genotoxicity 

Each of the above studies is addressed in the Environmental Fate, Wildlife and Aquatic Organism, 

and Toxicology data requirements listed in 40 CFR part 161 for antimicrobial pesticides. The 

following sections contain an evaluation of each waiver request. 
62 

A. Environmental Fate Data Requirements 

The following test for environmental fate is required for antimicrobials under 40 CFR 161.202 to 

assess the exposure to pesticides after application: 

1. Hydrolysis, OCSPP GLN 835.2120 

This test is waived because nanosilver undergoes dissolution with the generation of ionic silver 

rather than undergoing hydrolytic transformation. 

B. Wildlife and Aquatic Organism Data Requirements 

The acute ecotoxicity testing waiver request for the following tests required under 40 CFR 161 

was based on the non-leaching characteristic of NSPW-L30SS: 

2. Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids (OCSPP GLN 850.1010) 

3. Fish Acute Toxicity Test, Freshwater and Marine (OCSPP GLN 850.1075) 

4. Avian Acute Oral Toxicity Test (OCSPP GLN 850.2100) 

The results of these tests are required for use in determining the appropriate precautionary labeling 

on packages containing NSPW-L30SS prior to incorporating into a product. As summarized in 

Table 17, EPA has information on the acute toxicity of nanosilver for Daphnids and Freshwater 

Fish (items 2 and 3 above). Based on that information, because the EC50 values were less than 1 

mg/L, as indicated in Chapter 8 of the Pesticide Label Review Manual, EPA is requiring the 

following environmental hazard statement on the NSPW-L30SS label: 

This pesticide is toxic to fish and aquatic invertebrates. 

Given that there are no test results for avian species available for nanosilver, EPA requires that the 

environmental hazard statement for the NSPW-L30SS label be expanded to include birds: 

This pesticide is toxic to fish, aquatic invertebrates, and birds. 

However, if Nanosilva LLC wishes to remove birds from this statement they can submit results 

from an Avian Acute Oral Toxicity Test (OCSPP GLN 850.2100) showing that the nanosilver in 

NSPW-L30SS is non-toxic to birds with an LD50 of greater than 100 mg/kg. 

In addition, Nanosilva LLC is required to place the following statement on the NSPW-L30SS 

label: 

“Do not discharge effluent containing this product into lakes, streams, ponds, estuaries, oceans, 

or other waters unless in accordance with the requirements of a National Pollutant Discharge 

Elimination System (NPDES) permit and the permitting authority has been notified in writing 

prior to discharge. Do not discharge effluent containing this product to sewer systems without 

previously notifying the local sewage treatment plant authority. For guidance contact your 

State Water Board or Regional Office of the EPA”. 

EPA has waived the acute toxicity studies for fish and birds. The acute invertebrate study is 

required as a condition of registration to confirm the risk conclusions. 

C. Toxicology Data Requirements 

The following tests are required for antimicrobials under 40 CFR part 158.2230 (i.e., part 158W): 

5. 90-Day Dermal Toxicity (OCSPP GLN 870.3250 

6. Prenatal Developmental Toxicity Study (OCSPP GLN 870.3700) 
63 

The requirement for the 90-Day Dermal Toxicity study is waived because the calculated MOEs for 

dermal and incidental exposure to products incorporating NSPW-L30SS were greater than 

1,000,000 as compared to the highest target MOE of 3,000. However, if nanosilver is determined 

to be released during the leaching test of plastics incorporating NSPW-L30SS in amounts well 

above those found in the plastics leaching study already submitted such that the MOE calculated 

using the newly determined nanosilver release rate results in a possible risk concern, then the 

following route-specific subchronic tests is required to confirm the risk assessment for the 

nanosilver in NSPW-L30SS: 

 Dermal penetration study in rats (OCSPP GLN 870.7600) 

The requirement for the Prenatal Developmental Toxicity Study is waived because the following 

study has been determined to be more appropriate for NSPW-L30SS: 

 Modified 870.3550/ OECD TG 421: Reproduction/Developmental Toxicity Screening Test 

The following tests are required for pesticides under 40 CFR part 158.2230 (e.g., 158W): 

7. Bacterial Reverse Mutation Test (OCSPP GLN 870.5100) 

8. Detection of Gene Mutations in Somatic Cells in Culture (OCSPP GLN 870.5300) 

9. In Vitro Mammalian Cytogenetics (OCSPP GLN 870.5375) 

10. Mammalian Bone Marrow Chromosome Aberration Test (OCSPP GLN 870.5385) 

11. Immunotoxicity (OCSPP GLN 870.7800) 

The mutagenicity studies [Bacterial Reverse Mutation Test (OCSPP GLN 870.5100), Detection of 

Gene Mutations in Somatic Cells in Culture (OCSPP GLN 870.5300), In Vitro Mammalian 

Cytogenetics (OCSPP GLN 870.5375), and Mammalian Bone Marrow Chromosome Aberration 

Test (OCSPP GLN 870.5385)] are satisfied because there are in vitro studies available for 

nanosilver in the scientific literature which address/satisfy these data needs. There are also several 

well-conducted in vivo literature studies, showing cytotoxicity and evidence that the nanoparticles 

reached the target tissue, suggesting that the in vitro mutagenic potential observed may be intrinsic 

to nanoparticles, but is not expressed in whole animals. There is evidence that silver nanoparticles 

are genotoxic, expressing DNA damage in cultured human lung cells and in the lungs and liver of 

intact animals (comet assay) via intracellular generation of reactive oxygen species (ROS). 

However, since initiation of ROS-induced oxidative DNA damage can be blocked by ROS 

scavengers, there is not a concern for mutagenicity or genotoxicity and additional data are not 

needed. 

The immunotoxicity (OCSPP GLN 870.7800) is waived at this time. OPP has published a 

document (U.S. EPA, 2013) recommending that immune related endpoints be evaluated during the 

inhalation toxicity test, required as a term and condition on the registration, before determining if 

the immunotoxicity test is required. 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. The toxicology database for nanosilver does not reveal any evidence of treatmentrelated effects on the immune system, which suggests that nanosilver does not directly target the 

immune system. 
64 

Appendix B – Data Requirements, Enforceable Schedule, and Conditions of the 

Conditional Registration for NSPW-L30SS 

I. Introduction 

NSPW-L30SS is a liquid suspension containing 1% nanosilver by weight where the nanosilver 

active-ingredient is bonded to amorphous silica via a thiolate bond. The diameter of the spherical 

silica core is 320 nm on average (Lee et al., 2006) and the nanosilver particles that are attached to 

the silica core have mean diameters between 6.9 and 10.6 nm (Lee et al., 2007). The complex is 

formed by reacting spherical silica particles modified with thiol groups with silver nitrate and 

polyvinylpyrrolidone (PVP) in ethanol (Lee et al. 2007). 

II. Exposure Pathways

The human and environmental exposures resulting from the use of NSPW-L30SS, and use and 

disposal of plastics and textiles incorporating NSPW-L30SS will largely be a function of what 

materials are available for inhalation or dermal exposure during treatment of plastics and textiles 

or what materials leach or break away from the plastics and textiles incorporating Nanosilva 

during use and disposal. EPA anticipates that humans and the environmental will potentially be 

exposed to the following materials: 

1. Silver ions released from NSPW-L30SS; 

2. NSPW-L30SS complex; and/or 

3. Nanosilver that might break away from NSPW-L30SS. 

EPA expects that occupational inhalation and dermal exposures to NSPW-L30SS and the 

nanoparticles that might break away from NSPW-L30SS are likely to occur during the following 

use scenarios:

4. Mixing and loading of Nanosilver during preparation of a master batch 

5. Mixing, loading, and applying the NSPW-L30SS containing master batch during treatment 

of plastics and textiles 

6. Handling plastics and textiles incorporating NSPW-L30SS 

EPA expects consumer exposures to NSPW-L30SS, the silver ions derived from NSPW-L30SS, 

and the nanoparticles that break away from NSPW-L30SS could potentially occur during the 

following use scenarios:

1. Incidental oral exposure to plastics and textiles incorporating NSPW-L30SS 

2. Dermal exposure to plastics and textiles incorporating NSPW-L30SS 

Leaching of plastics and textiles incorporating NSPW-L30SS is anticipated to be the primary route 

by which NSPW-L30SS, silver ions, and nanosilver reach the environment. The silver released 

during leaching of plastics and textiles incorporating NSPW-L30SS could be discharged to the 

sanitary sewer system leading to publically owned wastewater treatment and privately owned 

septic systems, also known as the down-the-drain discharge scenario. Leaching of building 

material such as plastic siding and decks and outdoor furniture incorporating NSPW-L30SS will 

be discharged directly into the environment. Once NSPW-L30SS, silver ions, or nanosilver reach 

wastewater treatment and septic systems they will most likely complex with sulfide and partition 

to biosolids. However, some fraction of the silver compounds will reach surface water and may 

potentially impact aquatic organisms. 
65 

III. Data Needed to Confirm the Estimates for Risks of Exposure to NSPW-L30SS 

As a condition of the registration, EPA is requiring the Nanosilva LLC to conduct a number of 

studies, based on a tiered approach, which will allow EPA to confirm the findings of the risk 

assessment completed for the conditional registration and discussed in the decision document. 

These tests include Tier I studies to determine the nature and quantity of silver released from 

plastics incorporating NSPW-L30SS under conditions of use, product characterization testing, and 

silver release characteristics from the NSPW-L30SS complex. In addition, the Tier I studies 

include inhalation toxicity studies and an acute daphnid toxicity study. If nanosilver is determined 

to be released from plastics during the leaching tests as part of Tier I testing and the weight of 

evidence based on physical and chemical properties, toxicity, and exposure result in a risk concern 

then route-specific toxicity and environmental fate tests as part of Tier II studies to confirm the 

nanosilver risk assessment will be triggered. Data must be submitted within four years and 

according to the schedule provided in Table B3 to avoid cancellation of the conditional 

registration. 

The duration of four years was chosen to allow time for protocol reviews prior to initiation of the 

studies, completion of the studies, and Agency review of the studies following completion. EPA 

will evaluate these data as they are submitted during the period of the conditional registration to 

confirm EPA’s determination that the product is not expected to cause unreasonable adverse 

effects to human health and the environment. If EPA determines that Nanosilva LLC has failed to 

take appropriate steps to initiate the required studies, or failed to submit the protocols or studies, as 

required pursuant to this Appendix, EPA will issue a notice of intent to cancel Nanosilva LLC’s 

registration under FIFRA section 6(e). 

The following factors were considered in developing the data requirements for NSPW-L30SS: 

 Submitted as a new active ingredient application, NSPW-L30SS was subject to the data 

requirements for the registration of antimicrobial pesticides that are detailed in 40 CFR 

Part 161. These requirements include studies on physical and chemical characteristics, 

residue chemistry, environmental fate, toxicology, reentry protection, spray drift, wildlife 

and aquatic organisms, plant protection, nontarget insects, and product performance. 

 Although some studies, such as those dealing with physical and chemical characteristics, 

are required for all use patterns, many of the data requirements are conditional based on 

the use pattern. Information provided by Nanosilva LLC and information from the 

literature was used to tailor the data requirements to the use pattern. 

 Additional studies in the area of physical and chemical characterization that are not 

specifically included in 40 CFR Part 161 are needed because NSPW-L30SS contains 

nanosilver. These studies are needed because nanosized materials may have unique and 

new characteristics which are not present in the bulk or conventional materials. These 

characteristics have been recognized in the FIFRA SAP Report (FIFRA SAP, 2009) and by 

the MINChar Initiative (2008). 

In addition, the following recommendations from the FIFRA SAP report were considered in the 

development of the data requirements as terms and conditions on the conditional registration of 

NSPW-L30SS: 

 Both nano-sized particles of silver (Ag) as well as ionic silver (Ag+) can contribute to toxic 

effects of nanosilver. The rate of silver ion production, as well as the distribution of 

nanosilver in tissues and the environment, may differ substantially between nanosilver and 

other forms of silver, as nanosilver can potentially deliver silver ions directly to specific 
66 

tissues, cell membranes or inside cells – places where other forms of silver compounds 

cannot reach. Therefore, the hazard profile of nanosilver may differ from other forms of 

silver. 

 Particle size can substantially impact particle properties, such as rate and concentration of 

silver ion release, reactivity and catalytic efficiency, plasmon resonance, and quantum 

effects. Smaller sized-particles are more easily taken up by organisms and are distributed 

more widely. Other physicochemical properties, such as shape, surface area, surface charge 

or coating, are also likely to impact biological response and environmental fate. 

 The Panel “disagreed that nanosilver applied to a substrate will permanently bind with the 

substrate.” It is “especially challenging to determine that there is no release of 

nanomaterials from a substrate” under current state of science and available measurement 

standards. The Panel suggested that EPA require tests that simulate realistic use of products 

and potential nanosilver release along with quantitative life-cycle analysis and risk 

assessment. 

A listing of the studies that are needed for the registration of NSPW-L30SS is included in Tables 

B1 and B2. The studies included in Table B1 are considered to be Tier I, meaning that their need is 

not based on the results of other studies. The studies listed in Table B2 are considered to be Tier II, 

because they may or may not be required depending upon the results of the Tier I studies. NSPWL30SS and plastics/textiles incorporating NSPW-L30SS will be the test material during Tier I 

studies and the test material for Tier II studies will depend on the results of the Tier I leaching and 

dissolution studies. Figure B1 contains a conceptual diagram outlining the Tier I and Tier II testing 

approach. 
67 

Tier I – Testing

NSPW-L30SS Complex

Characterization, Stability, and Release Characteristics 

Particle Size Distribution 

Particle Surface Area 

Particle Stability 

Dissolution Kinetics

Occupation Inhalation Exposure 

90-day Inhalation Toxicity with Neuro 

Repro/Developmental Screening by Inhalation

Route 

 Silver Nanoparticle

Ecological Effects 

Figure B1 - Test material and tiered approach for NSPW-L30SS and plastic incorporating

NSPW-L30SS. See Tables B1 and B2 for the specific tests required for each

material.

Tier II

NSPW-L30SS Complex

Ecological Effects

Environmental Fate

Tier I – Testing

NSPW-L30SS Treated Plastic

Weight of evidence

is based on physical and chemical

properties, toxicity, 

and exposure. 

Low risk potential, high 

confidence in available data,

potential for no further testing.

Additional characterization of

toxicity needed. 
68 

IV. Enforceable Schedule 

EPA has prepared an enforceable schedule (Table B3) that is an estimation of the time required 

for developing and submitting protocols for review, conducting the studies, and submitting the 

resulting data, as well as EPA’s review of the submitted data. Technical issues may arise due to 

the unique nature of NSPW-L30SS, which may cause a delay in testing. In such a case, 

Nanosilva LLC shall submit a written request justifying the nature of the delay. In addition to 

technical delays, there may be delays by EPA in reviewing protocols and data submitted by 

Nanosilva LLC. In such a case, the EPA shall submit a written statement to Nanosilva LLC 

outlining the nature of the delay. In either case, if EPA determines a delay in the enforceable 

schedule is appropriate, it will amend the terms and conditions on the conditional registration. 

Notwithstanding technical delays or delays in reviewing data, if Nanosilva LLC fails to take 

appropriate steps to initiate the required studies, or fails to submit the protocols or data, as 

required pursuant to this Appendix, EPA will issue a notice of intent to cancel Nanosilva LLC’s 

registration under FIFRA section 6(e). Specifically, Nanosilva LLC shall: 

1. Submit protocols modified for NSPW-L30SS to EPA’s satisfaction for each of the 

data requirements listed in Tables B1 and B2. 

2. Perform each test and submit the results as described in Tables B1 and B2. 

These items shall be submitted according to the schedule provided in Table B3. If EPA 

determines that Nanosilva LLC has failed to initiate or to submit the required studies by the dates 

indicated in Table B3, then EPA will issue notice of intent to cancel Nanosilva LLC’s 

registration under FIFRA section 6(e). In addition, the conditional registration for NSPW-L30SS 

will automatically expire four years after being issued. 

All tests shall be conducted using laboratories that comply with the Good Laboratory Practice 

(GLP) standards of 40 CFR Part 160. In accordance with those regulations, the pesticide testing 

facility and the sponsor should comply with GLPs in the following areas: 

1. Organization and personnel 

2. Facilities 

3. Equipment 

4. Testing facilities operation 

5. Test, control, and reference substances 

6. Protocol for and conduct of a study 

7. Records and reports 

EPA expects that all studies performed to support, among other things, the registration or 

continued registration of a pesticide will address those requirements. However, studies deviating 

from those requirements may be considered if, as set forth in 40 CFR 160, a statement describing 

in detail all differences between the practices used in the study and those required by 40 CFR 

Part 160 is provided [see 40 CFR Part 160.12(b)]. As part of its review of the subject study, EPA 

will evaluate any such differences in determining if the study is acceptable for use in supporting, 

among other things, product registration or continued registration. 

V. Time-Limited Conditional Registration 

The conditional registration for NSPW-L30SS will automatically expire four years after being 

issued. Nanosilva LLC should request an amendment to remove the expiration date once they 

have submitted the required data if they wish to continue to sell and distribute NSPW-L30SS in 

the United States. 
69 

Table B1 - Summary of Tier I Required Data for NSPW-L30SS 

OCSPP Data Requirement1

Guideline Number: Study Title Reason for Study Test Material Comme

NSPW-L30SS CharacterizationNon-Guideline: Particle Size and Diameter (size) Distribution 

Required to characterize product. 

NSPWL30SS Determine both the size of the s

nanosilver particles. 

Non-Guideline: Surface Area Determination 

Required to characterize product. 

NSPWL30SS Determine both the surface area 

and the nanosilver particles. 

Non-Guideline: Particulate Stability Required to assess stability of NSPW-L30SS. NSPW- L30SS 

Nanosilva LLC claims that NSPcomplex that does not release nbe designed to demonstrate stab(normal and shear) and common EPA will use this information to claims of stability. 

Release Characteristics/Exposure Dissolution Kinetics 

Required to quantify the rate of dissolution of the nanosilver in NSPW-L30SS. 

NSPWL30SS 

Dissolution under environmentaneeded: moderate hard water at pH 6.5; and an estuarine conditithousand salinity. 

Non-Guideline: Plastic Leaching Study (Confirm Nanosilva LLC study results) 

Required to confirm assessment on human and environmental exposure. This test will determine what test substance will be used for Tier II studies. 

NSPWL30SS Treated Plastics 

A leaching study is needed to dform of silver that is released frplastics under conditions of usea leaching study using food simtotal-silver concentration. EPA follow-up study using physiologdetermine the form of silver reletreated plastic. The exposure daconfirm EPA’s evaluation of thNSPW-L30SS. 

Health Effects 870.3465: 90-Day Inhalation Toxicity (Rat) (Replace Song et al., 2012 study results) Modified to include a functional observational battery, motor activity and detailed neuropathology 

Required to account for the lack of inhalation data on the specific form of nanosilver 

NSPWL30SS 

The inhalation study is a route-sevaluate the effects of inhaling and loading NSPW-L30SS. The include a functional observationand detailed neuropathology to neurotoxicological effects. 
70 

Table B1 - Summary of Tier I Required Data for NSPW-L30SS 

OCSPP Data Requirement1

Guideline Number: Study Title Reason for Study Test Material Comme

Modified 870.3550/ OECD TG 421: Reproduction/Developmental Toxicity Screening Test* 

Required to account for the lack of reproductive and developmental data on the specific form of nanosilver 

NSPWL30SS 

The combined repeated-dose to

reproduction/developmental toxprovide additional information oreproduction and/or developmeninhalation study may also proviapplicable to a risk assessment fexposure. 

Ecological Effects850.1010: Aquatic Invertebrate Acute Toxicity, Freshwater Daphnids

Required to confirm findings/conclusions of the ecological risk assessment.

Nanosilver in NSPWL30SS 

The plastic lumber scenario has of the LOC for endangered aquarequired to confirm the conclusNSPW-L30SS is not significantnanosilvers from the open literarisk assessment.

1These guidelines only provide general guidance. Protocols shall be submitted prior to conducting these studies. *The use of a combined study that utilizes the two-generation reproduction study in rodents as a basic protocol for the addition of other assessments in the immature animal is encouraged. 
71 

Table B2 - Summary of Tier II Required Data for NSPW-L30SS 

OCSPP Data Requirement1

Guideline Number: Study Title Reason for Study Test Material Comm

Product Chemistry Non-Guideline: Plasmon resonance (UV-Visible Light) 

These studies are required to characterize the nanosilver if released during Tier I stability, dissolution or leaching studies. 

Nanosilver in NSPWL30SS 

Non-Guideline: Particle Size and Diameter (size) Distribution Non-Guideline: Surface Area Determination 830.7840: Solubility Non-Guideline: Zeta Potential and Surface Charge Determination Human Exposure – No Studies are Required in Tier IIHealth Effects 870.7600: Dermal Penetration 

Children’s exposure to nanosilver while contacting NSPW-L30SS treated plastics (flooring). 

** 

Based on the results of the pEPA may require additional potential adverse health outresulting from dermal expostreated plastics (flooring). 

Non-Guideline: peri- and postnatal exposure to NSPW-L30SS 

Children’s exposure to nanosilver while contacting NSPW-L30SS treated plastics and textiles. 

** 

Based on the results of the pEPA may require additional potential adverse health outresulting from incidental orL30SS-treated plastic toys (toys). 

Ecological Effects850.1850: Modified Aquatic Food Chain Transfer 

Required to determine bioavailability and biomagnification. 

** 

Traditionally use Fish and Obioaccumulation for chemictests more likely to yield usnanomaterials. If nanosilver be attached to or within aquaquatic plant, Tier II studiesinvertebrates in the chronic this study may potentially b
72 

Table B2 - Summary of Tier II Required Data for NSPW-L30SS 

OCSPP Data Requirement1

Guideline Number: Study Title Reason for Study Test Material Comm

850.4100: Terrestrial Plant Toxicity 

Required to determine effects to plants during early critical stages in their development. 

** 

If green algae (Selenastrum is the same or less sensitive silver, EPA would consider study. 

850.4400: Aquatic Plant Toxicity, Tier II (Definitive Test) 

Required to determine the toxicity to freshwater and aquatic plants. 

** 

Aquatic plants are the primacarbon and chemical energy Impacts to these primary primplications for the aquatic 

850.4500: Algal Toxicity, Tier II (Definitive Test) 

Required to determine the phytotoxicity to freshwater and marine algae. 

** 

Algae are the primary sourcchemical energy for aquatic these primary producers woimplications for the aquatic the green algae (S. capricorconfirm the findings/concluassessment. If the S. caprico

or of similar toxicity to the plants in the risk assessmenspecies then EPA would constudies with the other three freshwater diatom (Navicula diatom (Skeletonema costat(Anabaena flos-aqua) test). 

850.4550: Cyanobacteria Toxicity, Tier II (Definitive Test) 

Required to determine the toxicity to an important functional aquatic plant group. 

** 

Non-Guideline: Measuring the Chronic Effects of Freshwater Sediment-Associated Contaminants on Chironomus dilutes

Required to determine chronic impact to freshwater sediment dwelling organisms. 

** If more than one test material is identified for testing, only the more toxic material based on the Hyalella azteca results is required for testing with C. dilutes. 

Silver nanoparticles if releaenvironments are likely to pChronic tests on a freshwate(Chironomus dilutes, formewith epibenthic ecological nestimate potential risks to frorganisms. 
73 

Table B2 - Summary of Tier II Required Data for NSPW-L30SS 

OCSPP Data Requirement1

Guideline Number: Study Title Reason for Study Test Material Comm

Non-Guideline: Measuring the Chronic Effects of Freshwater Sediment-Associated Contaminants on Hyalella azteca

Required to determine chronic impact to freshwater sediment dwelling organisms. 

** 

Silver nanoparticles if releaenvironments are likely to pChronic tests on a freshwate(Hyalella azteca) with infau

be used to estimate potentiabenthic organisms. 

Non-Guideline: Measuring the Chronic Effects of Marine and Estuarine Sediment-Associated Contaminants on Leptocheirus plumulosus

Required to determine chronic impact to marine sediment dwelling organisms. 

** If more than one test material is identified for testing, only the more toxic material based on the Hyalella azteca results is required for testing with L. plumulosus. 

Silver nanoparticles if releaenvironments are likely to pChronic tests on an estuarin(Leptocheirus plumulosus) w

potential risks to marine ben

850.1075: Acute Toxicity Test with Freshwater and Marine Fish 

Required to confirm the acute effects of nanosilver. ** 

Acute toxicity test with fish assessment of possible risk environments, as an aid in dwater quality criteria for reguse in correlation with acute for comparative purposes. Bdemonstrated to be less sensnanosilvers than daphnia, if daphnid results demonstrate and its nanosilver are not sithe other nanosilvers used to assessment, testing with a frmay potentially be waived. 

850.1300: Daphnid Chronic Toxicity Test 

Required to determine the chronic effects of nanosilver. ** 

This guideline prescribes a which daphnids are exposed static-renewal or a flow thro
74 

Table B2 - Summary of Tier II Required Data for NSPW-L30SS 

OCSPP Data Requirement1

Guideline Number: Study Title Reason for Study Test Material Comm

850.1400: Early-Life Stage Toxicity Test for Freshwater, Estuarine, and Marine Fish 

Required to determine the chronic effects of nanosilver. ** 

Tests with the early-life stagdefine the lethal and subleththe stages and species testedof value for the estimation osublethal effects of the subs

Environmental FateNon-Guideline: Rate of Deposition/Aggregation 

The rates of aggregation and sedimentation are required for confirming estimates on the environmental fate and potential ecological impacts of these materials. 

** 

Knowing the rate of aggregthe products released from tinformation on the behavior aquatic environment. 

835.1100: Activated Sludge Sorption Isotherm 

Required to determine wastewater treatment removal efficiency. 

** 

The EPA uses Guideline 83estimate the removal efficiepasses through a wastewate

835.1230: Adsorption/Desorption (Batch Equilibrium) modified to also measure leaching (835.1240) 

Required to determine partitioning to solids and to determine the mobility in subsurface environment. 

** 

If the material is removed dtreatment, it may be depositdeposition of sludge (i.e. lanis not removed during wastereleased into aquatic envirosediment. Adsorption/desorrequired to determine the mnanosilver in the environmeThe distance that nanoparticgroundwater is thought to dsoil grains. Attachment of ndepends on the physical prointerception, and diffusion rnatural organic matter. Naninteraction depends on nanochemistry, and the arrangembe measured using soil colu
75 

Table B2 - Summary of Tier II Required Data for NSPW-L30SS 

OCSPP Data Requirement1

Guideline Number: Study Title Reason for Study Test Material Comm

850.3300 or OECD 209: Modified Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals 

Required to determine impact to wastewater treatment systems. 

** 

Silver from industrial procehas been shown to reduce mwastewater treatment systemstudy is to assess the impact nanosilver on microbial actitreatment. 

1These guidelines only provide general guidance. Protocols shall be submitted prior to conducting these studies. 

**The test material shall include materials that are released during the stability and plastics leaching studies. These materialreleased from NSPW-L30SS or plastics treated with NSPW-L30SS and or NSPW-L30SS released from plastics treated with 
76 

Table B3 – Enforceable Schedule 

NSPW-L30SS and plastics treated with NSPW-L30SS will be the test material during Tier I 

(Phases 1 – 4) studies. The test material for Tier II studies (Phases 5 – 9) will depend on the 

results of the Tier I leaching and dissolution studies (nanosilver and /or NSPW-L30SS released). 

 Tier I 

Guideline Protocols* Results† 

 Phase 1 – NSPW-L30SS Characterization 3 12 

NGL Particle Size Distribution 

NGL Surface Area 

 

Phase 2 – Product Testing 3 12 

NGL Particulate Stability 

 

Phase 3 – Release Characteristics/Exposure 3 15 

NGL Dissolution Kinetics 

NGL Leaching Test of Plastic 

 

Phase 4 – Health Effects 6 32 

870.3250 

90-Day Inhalation modified to include a functional 

observational battery, motor activity and detailed 

neuropathology 

 

870.3550 Modified Reproduction/Developmental Toxicity Screening Test 

via the inhalation route 

 

Phase 5 – Ecological Effects 6 18 

850.1010 Aquatic Invertebrate Acute Toxicity, Freshwater Daphnids 

 

 

Tier II 

Guideline Protocols* Results† 

Phase 6 – Characterization 18 24

NGL Plasmon Resonance 

NGL Particle Size Distribution 

NGL Surface Area 

830.7840 / 

830.7860 Solubility 

NGL Zeta-potential 

 

Phase 7 - Health Effects 18 45

NGL peri- and post-natal exposure to NSPW-L30SS 

870.7600 Dermal Penetration 

 

Phase 8 – Ecological Effects 18 45 

850.1850 Modified Aquatic Food Chain Transfer 

850.4100 Terrestrial Plant Toxicity, Seedling Emergence 

850.4400 Aquatic Plant Toxicity, Tier II (Definitive) Test 

850.4500 Algal Toxicity, Tier II (Definitive) Test 

850.4550 Cyanobacteria Toxicity, Tier II (Definitive) Test 

 
77 

Guideline Protocols* Results† 

Phase 8 – Ecological Effects (continued) 18 45 

NGL Measuring the Chronic Effects of Freshwater SedimentAssociated Contaminants on Chironomus dilutes 

NGL Measuring the Chronic Effects of Freshwater SedimentAssociated Contaminants on Hyalella azteca 

NGL 

Measuring the Chronic Effects of Marine and Estuarine 

Sediment-Associated Contaminants on Leptocheirus 

plumulosus

 

850.1075 Acute Toxicity Test with Freshwater and Marine Fish 

850.1300 Daphnid Chronic Toxicity Test 

850.1400 Early-Life Stage Toxicity Test for Freshwater, Estuarine, and 

Marine Fish 

 

Phase 9 – Environmental Fate 18 45 

NGL Rate of Deposition/Aggregation 

850.1100 Activated Sludge Sorption Isotherm 

835.1230 Adsorption/Desorption (Soil/Sediment) modified to include 

leaching component 

850.3300 or 

OECD 209 

Activated Sludge, Respiration Inhibition Test for Sparingly 

Soluble Chemicals 

*Number of months after conditional registration is issued to prepare and submit protocols. 

†Number of months after conditional registration is issued to perform study and submit results. 

NGL = Non-Guideline