Decision Document

Conditional Registration of HeiQ AGS-20 as a Materials 

Preservative in Textiles

December 1, 2011

Environmental Protection Agency

Office of Pesticide Programs

Antimicrobials Division
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TABLE OF CONTENTS

EXECUTIVE SUMMARY .............................................................................................................IV

I. REGULATORY DECISION SUMMARY ................................................................................1

II. BACKGROUND .........................................................................................................................3

2.1 REGULATORY HISTORY .......................................................................................................................................3

2.2 FIFRA SCIENTIFIC ADVISORY PANEL (SAP) MEETING .......................................................................................3

2.3 PROPOSED DECISION DOCUMENT ........................................................................................................................4

III. PRODUCT CHARACTERIZATION AND TESTING ........................................................4

3.1 PRODUCT DESCRIPTION AND PROPOSED USE.......................................................................................................4

3.2 PRODUCT TESTING...............................................................................................................................................5

IV. HUMAN HEALTH RISK ASSESSMENT.............................................................................8

4.1 ACUTE HUMAN TOXICOLOGY OF AGS-20 ...........................................................................................................8

4.2 SUBCHRONIC AND CHRONIC TOXICITY OF NANOSILVER .....................................................................................9

4.2.1 Inhalation Toxicity of Nanosilver ...............................................................................................................9

4.2.2 Oral Toxicity of Nanosilver ........................................................................................................................9

4.2.3 Dermal Toxicity of Nanosilver .................................................................................................................10

4.2.4 Neurotoxicity of Nanosilver......................................................................................................................11

4.2.5 Chronic Toxicity of Nanosilver ................................................................................................................12

4.2.6 Reproductive and Developmental Toxicity of Nanosilver........................................................................12

4.2.7 Mutagenicity of Nanosilver.......................................................................................................................12

4.2.8 Silver Ions.................................................................................................................................................12

4.2.9 Conclusions from Toxicity Studies...........................................................................................................13

4.3 ANTIMICROBIAL RESISTANCE............................................................................................................................13

4.4 MARGIN OF EXPOSURE ......................................................................................................................................14

4.4.1 Calculation of MOE..................................................................................................................................14

4.4.2 Point of Departures for AGS-20 ...............................................................................................................14

4.4.3 Target MOEs.............................................................................................................................................15

4.5 OCCUPATIONAL RISK ASSESSMENT...................................................................................................................16

4.5.1 Occupational Exposure when Handling AGS-20 Powder.........................................................................16

4.5.2 Particle Penetration through Respirator Filters when Handling AGS-20 Powder.....................................18

4.5.3 Conclusions from the Occupational Exposure Study................................................................................18

4.5.4 Occupational Margins of Exposure...........................................................................................................18

4.5.5 Conclusions for Occupational Risk...........................................................................................................21

4.5.6 Occupational Exposure and Health Data Requirements ...........................................................................22

4.6 CONSUMER RISK ASSESSMENT ..........................................................................................................................22

4.6.1 Ultrapure Water Textile Leaching Study ..................................................................................................23

4.6.2 Alkaline Water and Simulated Laundering Textile Leaching Study.........................................................23

4.6.3 Conclusions Regarding the Consumer Exposures.....................................................................................24

4.6.4 Consumer Margins of Exposure................................................................................................................25

4.6.5 Conclusions for Risk to Consumers..........................................................................................................29

4.6.6 Consumer Exposure and Health Data Requirements ................................................................................31

V. ENVIRONMENTAL RISK ASSESSMENT............................................................................33

5.1 ENVIRONMENTAL FATE .....................................................................................................................................33

5.1.1 Nanosilver.................................................................................................................................................33

5.1.2 Silver Ions.................................................................................................................................................34

5.1.3 Impacts to Wastewater Treatment/Septic Systems ...................................................................................34

5.2 ENVIRONMENTAL TOXICITY ..............................................................................................................................34

5.2.1 Silver Ions.................................................................................................................................................35
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5.2.2 Nanosilver.................................................................................................................................................35

5.3 AQUATIC RISK ASSESSMENT .............................................................................................................................37

5.3.1 Aquatic Risk Quotient...............................................................................................................................37

5.3.2 Conclusions for Aquatic Risk ...................................................................................................................38

5.3.3 Ecological Effects and Environmental Fate Data Requirements...............................................................39

VI. REGULATORY ACTION .......................................................................................................41

6.1 LEGAL FRAMEWORK..........................................................................................................................................41

6.2 FINDINGS AND REGISTRATION DECISION...........................................................................................................42

6.3 BASIS FOR CONDITIONAL REGISTRATION ..........................................................................................................42

6.3.1 Data Generation ........................................................................................................................................42

6.3.2 Public Interest ...........................................................................................................................................43

6.3.3 No Unreasonable Adverse Effects ............................................................................................................44

References.................................................................................................................................... 47

LIST OF TABLES

Table 1 – Product Testing Submitted by HeiQ for AGS-20........................................................... 6

Table 2 – Acute Toxicity Profile for AGS-20 ................................................................................ 9

Table 3 – Points of Departures...................................................................................................... 15

Table 4 – Target Margins of Exposures........................................................................................ 15

Table 5 – Unit Exposures for Mixing and Loading of Wettable Powders (Matthews, 2000)...... 17

Table 6 – Inhalation MOEs for AGS-20 Occupational Handlers................................................. 19

Table 7 – Dermal MOEs for AGS-20 Occupational Handlers..................................................... 20

Table 8 – Silver Released During Washing of AGS-20 Treated Textile...................................... 24

Table 9 – Inhalation MOEs for Drying AGS-20 Treated Textiles ............................................... 25

Table 10 – Incidental Oral MOEs for Toddlers Exposed to AGS-20 Treated Textiles................ 26

Table 11 – Dermal MOEs for Toddlers Exposed to AGS-20 Treated Textiles............................ 28

Table 12 – Aggregate MOEs for Toddlers Exposed to AGS-20 Treated Textiles....................... 29

Table 13 – Nanosilver Toxicity to Aquatic Species..................................................................... 36

Table 14 – Risk Quotients for Nanosilver in Surface Water ........................................................ 38

Appendix A: Data Requirements for the Registration of HeiQ AGS-20 
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EXECUTIVE SUMMARY

EPA is granting a conditional registration for the HeiQ Materials AG product named “HeiQ 

AGS-20” (hereafter referred to as “AGS-20”) under section 3(c)(7)(C) of the Federal Insecticide, 

Fungicide and Rodenticide Act (FIFRA). The Agency’s basis for the conditional registration is 

that:

• AGS-20 contains nanosilver as an active ingredient and the nanosilver in AGS-20 is not 

in any currently registered pesticide; 

• Use of AGS-20 will not cause unreasonable adverse effects on the environment during 

the period when newly required data are being developed; 

• Insufficient time has elapsed for HeiQ to generate and submit the newly required data;

and 

• Use of AGS-20 is in the public interest.

AGS-20 is a nanosilver-silica composite where the nanosilver active-ingredient is sintered onto 

amorphous silicon dioxide having typical particle diameters of one micrometer (1 μm or 1,000 

nm). AGS-20 will be incorporated into textiles to suppress the growth of bacteria, which cause 

textile odors, stains, and degradation, through the slow release of silver ions. HeiQ proposed that 

textiles would be treated by application of AGS-20 either as a surface coating (e.g., textile 

finishing) or by incorporation into the starting materials (e.g. fiber spinning). The final textile 

article will contain less than 0.01% silver by weight to impart durable antimicrobial and 

preserving activity. The treated textiles can be manufactured into indoor use articles such as 

sheets, blankets, towels, napkins, outerwear, sportswear, sleepwear, undergarments, socks and 

hosiery, and outdoor use articles such as sailcloth, tarps, tents and awnings.

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

1) Silver ions released from the AGS-20 particles;

2) The AGS-20 particles; and

3) Nanosilver that might break away from AGS-20 particles.

For the purposes of risk from exposure to silver ions, EPA relied on the existing reregistration 

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

ions derived from AGS-20 treated textiles is not of concern.

For purposes of risk from exposure to AGS-20, HeiQ submitted results from short-term acute 

animal-toxicity tests completed using high-level doses of AGS-20 showing that there were no 

mortalities or abnormalities in test animals after administration of AGS-20 by oral, dermal, and 

inhalation routes. AGS-20 caused moderate to no irritation to the skin and eyes of test animals,

and was not a skin sensitizer. Based on these results, shipping containers filled with AGS-20 are 

required to carry a label stating “CAUTION” where contact with items treated with AGS-20 is 

restricted for 12 hours after application and AGS-20 does not require child-resistant packaging. 

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

AGS-20 or for the nanosilver that might break away from AGS-20. However, there are 

intermediate-term toxicity studies available in the scientific literature for analogous forms of 

nanosilver. In the absence of intermediate-term toxicity studies for AGS-20 or the nanosilver that 
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might break away from AGS-20, EPA evaluated the risk from occupational and consumer 

exposure using the data in the scientific literature on nanosilver. In addition, because the 

available exposure data are limited, EPA calculated the daily-dose to workers assuming that all 

the silver in AGS-20 was freely available as nanosilver. Likewise for the daily-dose to 

consumers, EPA assumed that all of the silver found in the wash water from color-fast testing of 

AGS-20 treated textiles and during drying of AGS-20 treated textiles consisted of nanosilver. 

Both of these assumptions overestimate the daily-dose of nanosilver that a person could 

potentially receive when working with AGS-20 or wearing AGS-20 treated textiles. Because the 

studies on which the assessment relies did not evaluate toxicity over all life stages or evaluate all 

potential effects, the Agency used a maximum 10-fold database uncertainty factor when 

evaluating the risk from exposure to the nanosilver that might break away from AGS-20. 

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

for analogous forms of nanosilver and environmental exposure was assessed assuming that 300 

million people (U.S. population) each purchased one t-shirt treated with AGS-20 and that all the 

silver in those t-shirts was released during a year as nanosilver.

Using conservative assumptions which overestimate the dose of nanosilver that could potentially 

be derived from AGS-20 along with maximum values for risk uncertainty factors, EPA is able to 

determine that for the period of conditional registration, there is a low probability of adverse risk 

to children and the environment from textiles treated with AGS-20. Thus, the Agency concludes 

that use of AGS-20 will not cause unreasonable adverse effects on the environment during the 

period when newly required data are being developed. The Agency does have a risk concern for 

occupational exposure when handling AGS-20 powder during mixing and loading operations. As 

a result of this concern, HeiQ amended its application so that the pesticide label requires workers 

to wear personal protective equipment and use engineering controls when handling AGS-20 

powder. 

As a condition of registration, EPA is requiring HeiQ to conduct a number of studies during the 

period of conditional registration. The required tests include route-specific toxicity studies for 

occupational exposure scenarios as well as product characterization and stability tests to 

determine if nanosilver breaks away from AGS-20. If nanosilver is found to break away from 

AGS-20 or textiles treated with AGS-20, then additional testing will be triggered to determine 

the affect of AGS-20 derived nanosilver on humans and the environment. 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. The Agency will evaluate these data as they are submitted during the period of the 

conditional registration to confirm that the use of AGS-20 will not cause unreasonable adverse 

effects to human health and the environment. If HeiQ fails to take appropriate steps to initiate the 

required studies, or if HeiQ fails to submit the protocols or data, EPA will issue a notice of intent 

to cancel HeiQ’s registration under FIFRA section 6(e).

EPA believes that the use of HeiQ’s product is in the public interest. Use of AGS-20 may lead to 

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

use patterns. In addition, AGS-20 appears to offer prolonged ability to suppress the growth of
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odor causing bacteria through the slow release of silver ions as compared to the rapid release of 

silver ions from registered products containing silver salts.
I. REGULATORY DECISION SUMMARY

EPA is granting a conditional registration for the HeiQ Materials AG product named “HeiQ 

AGS-20” (hereafter referred to as “AGS-20”) under section 3(c)(7)(C) of the Federal Insecticide, 

Fungicide and Rodenticide Act (FIFRA). The Agency’s basis for the conditional registration is 

that:

1) AGS-20 contains an active ingredient, silver nanoparticles also known as nanosilver. The 

AGS-20 nanosilver is not an active ingredient in any currently registered pesticide (i.e., a 

“new” active ingredient);

2) Use of AGS-20 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 HeiQ to generate and submit the newly required data; 

and 

4) Use of AGS-20 is in the public interest.

The product is the subject of an application submitted by HeiQ Materials AG (“HeiQ”) in 

September 2008. The product is named “HeiQ AGS-20,” referred to as AGS-20 in this 

document, and the nanosilver active ingredient is intended for use as a preservative in textile 

products. AGS-20 is a nanosilver-silica composite with typical particle diameters of one 

micrometer (1 μm or 1,000 nm) where the nanosilver active-ingredient is sintered onto 

amorphous silicon dioxide (i.e., silica). 

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 

of an ingredient as an attribute relevant when determining if the product in an application is 

identical or substantially similar in composition to a registered pesticide product. However, a 

nanoscale ingredient may have properties that are different from those of conventionally-scaled 

ingredients 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 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 necessarily will need 

data on the nanoscale material to make the requisite statutory findings. 

In September, 2008 HeiQ submitted an application for registration of AGS-20 as a “me-too” 

registration under FIFRA section 3(c)(7)(A). However, after consultation with the FIFRA 

Scientific Advisory Panel, which was held from November 3 through 5, 2009, EPA could not 

conclude that the nanoscale material in AGS-20 was an active ingredient in any currently 

registered pesticide. Consequently, EPA requested that HeiQ re-classify its application to 

register AGS-20 from “me-too” to a new active ingredient. HeiQ agreed to this request and on 

March 31, 2010 EPA announced that AGS-20 was re-classified as a product containing a new 
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active ingredient (Federal Register, Vol. 75, No. 61, Page 16110). Because the Agency had not 

reached a final decision with regard to which types of data would be further required for 

nanoscale materials, HeiQ did not have the benefit in support of an application for a new active 

ingredient of a reasonable period of time within which to generate and submit this data to the 

Agency. 

With respect to the third conclusion, EPA has determined that the use of HeiQ’s product during 

the period 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 is unlikely to 

cause unreasonable adverse effects on humans or the environment. Although the available data 

on nanosilver are limited, EPA is able to determine that for the period of conditional registration, 

there is a low probability of adverse risk to children and the environment from textiles treated 

with AGS-20. Thus, the Agency concludes that use of AGS-20 will not cause unreasonable 

adverse effects on the environment during the period when newly required data are being 

developed. The Agency does have a risk concern for occupational exposure when handling AGS20 powder during mixing and loading operations. As a result of this concern, HeiQ amended its 

application so that the pesticide label requires workers to wear personal protective equipment 

and use engineering controls when handling AGS-20 powder.

For a variety of reasons, the Agency has determined that granting a section 3(c)(7)(C) 

registration at this time is in the public interest. EPA believes that HeiQ’s product may lead to 

less environmental loading of silver as compared to currently registered products containing 

silver salts with the same use patterns. In addition, HeiQ’s product appears to offer prolonged 

ability to reduce the number of odor causing bacteria through the slow release of silver ions as 

compared to the rapid release of silver ions from registered products containing silver salts. 

Moreover, because we can find that a section 3(c)(7)(C) registration is unlikely to cause an 

unreasonable adverse effect on the environment, allowing such registration to be granted before 

the newly-required data is generated allows the HeiQ product to compete with other like-situated

products. Allowing HeiQ’s product on the market pending generation of data allows HeiQ to

participate in the textile economy along with the other registrants with like-situated products, and 

allows consumers of these products a new choice among the potential like-situated products.

As a condition of registration, EPA is requiring HeiQ to conduct a number of studies during the 

period of conditional registration. The required tests were adapted from 40 CFR Part 161 for 

nanoscale ingredients and include route-specific toxicity studies for occupational exposure 

scenarios as well as product characterization and stability tests to determine if nanosilver breaks 

away from AGS-20. If nanosilver is found to break away from AGS-20 or textiles treated with 

AGS-20 then additional testing will be triggered to determine the affect of AGS-20 derived 

nanosilver on humans and the environment. 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. The Agency will 

evaluate these data as they are submitted during the period of the conditional registration to 

confirm that the use of AGS-20 will not cause unreasonable adverse effects to human health and 

the environment. If HeiQ fails to take appropriate steps to initiate the required studies, or if HeiQ 

fails to submit the protocols or data, EPA will issue a notice of intent to cancel HeiQ’s 

registration under FIFRA section 6(e).
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II. BACKGROUND

2.1 Regulatory History

In September 2008, HeiQ submitted an application for registration of a new antimicrobial 

pesticide product named AGS-20, which is a silver-based product proposed for use as a materials 

preservative additive to coatings, polymers and textiles. HeiQ’s application originally claimed 

that AGS-20 was similar to other currently registered silver-based antimicrobial pesticide 

products and should be given a “me-too registration” under FIFRA section 3(c)(7)(A). The 

company later amended its application to limit the proposed use of AGS-20 for treatment only of 

textiles. After consultation with the FIFRA Scientific Advisory Panel, which was held from 

November 3 through 5, 2009, EPA determined that the nanosilver active ingredient in AGS-20 

differed from the active ingredients in currently registered silver-based antimicrobial products.

Consequently, EPA requested that HeiQ re-classify its application to register AGS-20 from a 

“me-too” to a new active ingredient. HeiQ agreed to this request and on March 31, 2010 EPA 

announced that AGS-20 was re-classified as a product containing a new active ingredient 

(Federal Register, Vol. 75, No. 61, Page 16110). In response to discussion with HeiQ regarding 

potential risk concerns, which resulted from using conservative assumptions and data in the 

public literature on nanosilver formulations, HeiQ submitted an amended application reducing 

the application rate for fabric treated by surface coating from 30 ppm to 20 ppm and requiring

use of personal protective equipment and engineering controls.

2.2 FIFRA Scientific Advisory Panel (SAP) Meeting 

In November, 2009 the Agency 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) are likely 

to affect biological activity, among other things. 

The SAP commented that not enough literature is 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 are known that investigate the toxicity

of nanosilver from exposure by these routes. Nor is 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 exists for the environmental fate and transport of 
4

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 are 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 have 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 the Agency 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.

2.3 Proposed Decision Document

On August 12, 2010, 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 13, 2010. 

EPA is posting responses to the 45 comments received regarding this decision in the Pesticides 

Docket. 

The majority of comments concerned the level of testing required prior to registering AGS-20. 

While a few commenters believed that nanosilver is substantially similar to already-registered

pesticides containing silver and therefore should not require additional testing, many commenters

suggested that, because the existing data are allegedly insufficient, all EPA data requirements 

should be satisfied prior to registering AGS-20. EPA considered these comments carefully and 

believes that additional testing is necessary but that there are sufficient data for making an 

informed scientific evaluation regarding the conditional registration of AGS-20. Other key 

comments were submitted regarding potential impacts to the operation of wastewater treatment 

plants, potential development of widespread antibiotic resistance, and potential exposures during 

laundry drying of AGS-20 treated textiles. EPA considered these issues as discussed in this 

decision document. In addition, studies published in the scientific literature after August 2010 

covering the effects of nanosilver on organisms were provided and incorporated into this 

document. Finally, EPA revised the data requirements being imposed in connection with this 

conditional registration based on EPA’s consideration of the submitted public comments and 

new studies in the scientific literature.

III. PRODUCT CHARACTERIZATION AND TESTING

3.1 Product Description and Proposed Use

AGS-20 contains nanosilver sintered onto amorphous silicon dioxide (SiO2). The SiO2 fine 

structure consists of aggregate matrix particles with an average diameter of approximately 1,000 
5

nm or 1 micron. Each silica particle contains many nanosilver particles with a typical diameter 

between 1 and 10 nm (Egger et al., 2009) and some particles in the 50 nm range. Reference to 

the nanosilver in AGS-20 (whether when part of the composite or when broken away from the 

composite) is to the “new active ingredient” and reference to “AGS-20” or the AGS-20 

“composite” is to the end use product. 

AGS-20 is a powder and was proposed to be incorporated into textiles to suppress the growth of 

bacteria that cause odors, stains, and degradation. HeiQ may not make any public health claims 

relating to the antimicrobial activity of AGS-20. HeiQ proposed to use AGS-20 to treat textiles 

either as a surface coating (e.g., textile finishing) or by incorporation into the starting materials 

(e.g. fiber spinning) prior to textile manufacture. The final textile article was proposed to contain 

less than 0.01% silver by weight to impart durable antimicrobial and preserving activity to 

manufactured products. The types of textiles include those made from natural and synthetic 

fibers, which are used to manufacture indoor use articles such as sheets, blankets, towels, 

napkins, outerwear, sportswear, sleepwear, undergarments, socks and hosiery, and outdoor use 

articles such as sailcloth, tarps, tents and awnings.

3.2 Product Testing

HeiQ submitted results from testing of AGS-20 to determine the product identity and 

composition, physical and chemical properties, and acute toxicity as summarized in Table 1. The 

tests were performed using standard EPA test guidelines1

. These tests are listed in the U.S. Code 

of Federal Register Title 40 Parts 158 and 161, and identify the types of data EPA expects an 

applicant to provide to support an application for registration of a pesticide product. HeiQ 

performed these tests in anticipation of obtaining a “me-too registration” prior to notifying EPA 

that AGS-20 contained nanosilver. Although the test results provided useful information, 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. As a result, future applicants for products containing 

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

 1 Available at http://www.epa.gov/ocspp/pubs/frs/home/guidelin.htm
6

Table 1 – Product Testing Submitted by HeiQ for AGS-20

Guideline 

Number

Guideline Name Required under 40 CFR

Product Identity and Composition

830.1550 Product identity and composition 161.155

830.1600 Description of materials to produce product 161.160

830.1620 Description of production process 161.162

830.1650 Description of formulation process 161.165

830.1670 Discussion of formulation of impurities 161.167

830.1700 Preliminary analysis 161.170

830.1750 Certified limits 161.175

830.1800 Enforcement analytical method 161.180

Physical and Chemical Properties

830.6302 Color 161.190

830.6303 Physical state 161.190

830.6304 Odor 161.190

830.6317 Storage stability 161.190

830.6320 Corrosion characteristics 161.190

830.7000 pH 161.190 (if dispersible with water)

830.7200 Melting point/melting range 161.190

830.7300 Density 161.190

830.7520 Particle size, fiber length, and diameter 

distribution

Not Required, information in 

Egger et al., 2009

830.7840 Water solubility 161.190 

830.7950 Vapor Pressure 161.190 (waived for solids)

Health Effects (Toxicology)

870.1100 Acute Oral Toxicity 161.340

870.1200 Acute Dermal Toxicity 161.340

870.1300 Acute Inhalation Toxicity 161.340

870.2400 Acute Eye Irritation 161.340

870.2500 Acute Dermal Irritation 161.340

870.2600 Skin Sensitization 161.340

In addition to the test results listed in Table 1, HeiQ subsequently submitted the following 

supplemental studies to support the registration of AGS-20:

Leaching Studies

• Height, M.J. 2009. Are silver particles released from textiles treated with the HeiQ AGS20 silver additive? (MRID 477287-01)

• Height, M.J. 2009. Supplemental to MRID 47728701 (Are silver particles released from 

textiles treated with the HeiQ AGS-20 silver additive?): Response to EPA Letter of July 

24, 2009. (MRID 478391-01)

Efficacy

• Egger, S., Lehmann, R.P., Height, M.J., Loessner, M.J., Schuppler, M. 2009. 

Antimicrobial Properties of a Novel Silver-Silica Nanocomposite Material. Applied and 

Environmental Microbiology 75:2973-2976. (MRID 477575-03)
7

Occupational Exposure

• Demou, E., Peter, P., Hellweg, S. 2008. Exposure to Manufactured Nanostructured 

Particles in an Industrial Pilot Plant. Annuals Occupational Hygiene 52:695-06. (MRID 

477575-02)

Impact to Wastewater Treatment

• Meyer, M., Height, M. 2008. Toxicity of HeiQ AGS-20 and HeiQ AGS-20 TF textile 

finish in municipal wastewater treatment. (MRID 479344-01)
8

IV. HUMAN HEALTH RISK ASSESSMENT 

Based on the proposed use pattern of AGS-20, EPA anticipates humans could be exposed to the 

following substances: 

1. Silver ions released from AGS-20 treated textiles;

2. AGS-20 particles; and 

3. Nanosilver that might break away from the AGS-20 particles.

Because the levels of silver in AGS-20 treated textiles are lower than for other currently 

registered products which use silver ions (U.S. EPA, 1993), EPA concluded that the risk from 

exposure to silver ions derived from AGS-20 treated textiles is not of concern. HeiQ 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 AGS-20. In addition, 

EPA has also reviewed data and information from the scientific literature. This section discusses 

EPA’s assessment of the potential risks to human health from the use of AGS-20. The first 

section addresses information concerning toxicity of AGS-20 and nanosilver. The second section 

addresses potential levels of occupational exposure and risk to workers who handle AGS-20 

powder. The final section addresses potential levels of consumer exposure and risk to children 

who wear AGS-20 treated textiles. As part of these discussions, additional data requirements are 

identified as necessary to confirm the assessment of risks from exposure to AGS-20 as are use 

restrictions consistent with those proposed in the original and amended applications.

4.1 Acute Human Toxicology of AGS-20

HeiQ submitted results from short-term guideline acute animal-toxicity tests completed using 

high-level doses of AGS-20 as outlined in Table 2. There were no mortalities or abnormalities 

noted in test animals after administration of AGS-20 by oral, dermal, and inhalation routes at 

dose levels of up to 2,000 mg/kg, 5,000 mg/kg, and 1,081 mg/L, respectively; AGS-20 caused 

moderate to no irritation to skin or eyes at dose levels of up to 1,000 mg and 5,000 mg, 

respectively; and was not a skin sensitizer. According to the Agency’s Toxicity Category system, 

which is used for product labeling purposes, shipping containers filled with AGS-20 are required 

to carry a label stating “CAUTION” where contact with items treated with AGS-20 is restricted 

for 12 hours after application and AGS-20 does not require child-resistant packaging. 
9

Table 2 – Acute Toxicity Profile for AGS-20

Study Toxicity Category

Acute Oral Toxicity Category III

No mortality or abnormalities after dose of 2,000 mg/kg

Acute Dermal Toxicity Category III

No mortality or abnormalities after dose of 5,000 mg/kg

Acute Inhalation Toxicity Category III

No mortality or abnormalities after dose of 1.081 mg/L

Acute Eye Irritation Category III

Moderate to not irritating after dose of 1,000 mg

Acute Dermal Irritation Category IV

Mild or slight irritation after dose of 5,000 mg 

Skin Sensitization Not a sensitizer

4.2 Subchronic and Chronic Toxicity of Nanosilver

There are no repeated-dose subchronic or chronic toxicity studies available for AGS-20. 

However, there are repeated-dose toxicity studies available in the scientific literature for 

analogous forms of nanosilver. Since nanosilver might be released from AGS-20, the Agency 

considers the scientific literature studies on nanosilver toxicity relevant to AGS-20.

4.2.1 Inhalation Toxicity of Nanosilver

There is one literature study on the inhalation toxicity of nanosilver (Sung et al., 2009). This 

study showed toxic effects in the liver (bile-duct hyperplasia) and lungs (chronic alveolar 

inflammation and macrophage accumulation in the lungs of males and females, and erythrocyte 

aggregation) of rats after administration of nanosilver with average diameters between 18 to 19 

nm (minimum diameter of 2 nm and maximum diameter of 65 nm) for 13 weeks (90-day) via the 

inhalation route at the high-dose level of 515 μg/m3 (3.03×106 particles/cm3

). The Agency 

considers these effects adverse. Also, 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. Based on the toxic effects 

observed, a No-Observed-Adverse-Effect-Level (NOAEL) of 133 μg/m3 (1.4×106 particles/cm3

, 

the mid-dose level) was determined. 

4.2.2 Oral Toxicity of Nanosilver

There are three studies in the scientific literature that investigate toxicity of nanosilver via the 

oral route. The first reported findings after 28 days of repeated administration of carboxymethyl 

cellulose-coated nanosilver with average diameter of 60 nm (minimum diameter of 53 nm and 

maximum diameter of 71 nm) to rats (Kim, et al, 2008). The effects reported 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. A dosedependent increase in silver distribution in many tissues (liver, kidneys, stomach, brain, lungs, 
10

testes, and blood), with a two-fold higher accumulation in the kidneys of female rats when 

compared with male rats across all dose groups, was also reported. A NOAEL of 30 mg/kg/day 

(lowest dose level), based on the observed liver effects and increase in alkaline phosphatase 

(ALP) and cholesterol at 300 mg/kg/day (mid dose level), was determined. The second study was 

performed by the same group in a different strain of rats for 90 days (Kim et al., 2010). This 

study involved repeated administration of 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 NOAEL of 30 mg/kg/day. However, intestinal pigmentation from

exposure to nanosilver was reported, which was not observed in the 28 day study. The third 

study was performed by repeated administration of nanosilver with average diameter of 42 nm 

(minimum diameter of 25 nm and maximum diameter of 55 nm) to mice over 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 alkaline 

phosphatase (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 

liver or the small intestines examined. A NOAEL of 0.5 mg/kg/day was determined, 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. This study provided the most conservative NOAEL via 

the oral exposure route for nanosilver.

4.2.3 Dermal Toxicity of Nanosilver

There is little data on dermal toxicity resulting from dermal exposure to nanosilver. However, 

there is one published report on nanosilver that is available for use by the Agency concerning 

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

patient using 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 urine (Trop, 2006). This study indicates to the Agency that nanosilvers can be 

systemically absorbed when a large area of the skin barrier is severely compromised. 

There are no dermal toxicity studies on nanosilver available to the Agency. In the absence of any 

such dermal toxicity studies, the Agency 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 allow 

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

However, the Agency 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, the Agency has 

observed variation in test results among laboratories. As a result, the Agency assumes a default 

DAF of 100% when no in vivo data are available. Therefore, if in vivo dermal penetration studies
11

are available, either those studies alone or in combination with in vitro studies are used for 

deriving a DAF of less than 100%.

Here, there are no Agency guideline or scientific literature studies conducted in animals for the 

in vivo dermal absorption of the nanosilver in the AGS-20 composite or of nanosilver available 

to the Agency. However, there is a human clinical study that examined silver levels in blood 

after application of burn wound dressings containing nanosilver (Moiemen et al., 2011). The 

study tracked both the absorption and elimination of silver and the EPA used this information to 

derive a conservative DAF of 0.1% for nanosilver. In addition an in vitro study with nanosilver 

in human skin is available in the scientific literature indicating that nanosilver penetration was 

very low for both intact and abraded skin at 0.00066% and 0.0033%, respectively (Larese et al., 

2009). EPA requires in vivo data on the ingredient in question to lower the DAF below the 100% 

default. The available human in vivo study indicating absorption of nanosilver is below 0.1% 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 DAF of 0.1% for 

the nanosilver that might break away from the AGS-20 composite. This DAF will be used by the 

Agency until Tier I dermal toxicity data are provided by HeiQ for AGS-20, which will provide a 

route-specific study for use in subsequent risk assessments. 

4.2.4 Neurotoxicity of Nanosilver

There are no studies in the scientific literature that investigate the neurotoxicity of nanosilver in 

mammals. A recent review of the scientific literature and clinical observations regarding the 

neurotoxicity of silver included observations for nanosilver used in burn wound bandages. In this 

review, it was concluded that although silver is known to be distributed throughout human 

tissues and organs after administration via pharmaceutical and burn wound bandage applications, 

there was little evidence suggesting that silver enters tissues of the central nervous system or is 

the cause of neurotoxic damage (Lansdown, 2007). The review suggested that silver be classified 

along with iron, zinc, and gold as a metal that is sequestered by tissue and not associated with 

pathological changes or pathophysiological consequences, including changes in the bloodcerebrospinal fluid barrier.

Arguing against this are in vivo studies completed with nanosilver indicating concentration/doserelated increases in the levels of silver in the olfactory bulb and/or brain after inhalation (Sung et 

al. 2009) and oral administration of nanosilver in rats (Kim et al. 2010, Kim et al. 2008). A 

caveat of these studies is that it is not possible to determine if silver identified in the olfactory 

bulb and/or brain was in the nanoparticlate or ionic form. However, there are reports in the 

literature from in vivo studies the nanosilver can cross the blood brain barrier in rats (Tang et al., 

2009; Lankveld et al. 2010) and induce brain edema (Sharma et al., 2010), indicating that 

nanosilver particles can reach brain tissue. Once in the brain, there is the question of whether or 

not nanosilver would cause neurotoxicity. The following in vitro studies indicate that nanosilver 

can cause neuronal toxicity and depletion of the neurotransmitter dopamine (Hussain et al., 

2006) and changes in inhibitory action potentials in hippocampal neurons (Liu et al., 2009), 

which suggests the potential for nanosilver to cause neurotoxicity by altered neurotransmission 

and direct cytotoxicity. However, it is unknown if the doses used in the in vitro studies would 

approximate in vivo levels. 
12

4.2.5 Chronic Toxicity of Nanosilver

There are no studies in the scientific literature that investigate the chronic toxicity or 

carcinogenicity of nanosilver.

4.2.6 Reproductive and Developmental Toxicity of Nanosilver

There are no studies in the scientific literature that investigate the reproductive or developmental 

toxicity of nanosilver in mammals. However, one study does show significant, dose-dependent 

increases in the concentration of silver in the testes of rats after ingesting nanosilver via gavage 

for 28 days at doses ranging from 30 to 1,000 mg/kg/day (Kim et al., 2008). No increases in 

silver were reported in the testes or reproductive organs of rats after inhaling nanosilver for 13 

weeks at concentrations up to 515 μg/m3 (Sung et al., 2009). The technique used to detect silver 

in these studies did not distinguish between nanosilver and silver ions. Thus, these animal data 

indicate that silver ions released from nanosilver or nanosilver can accumulate in the testes after 

oral, but not inhalation exposure. The only study that the Agency is aware of is an in vitro study 

investigating the toxicity of 15 nm nanosilver on spermatagonia 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, nanosilver and silver ions caused altered cellular 

morphology, decreased mitochondrial activity (as indicated by MTS assay), and increased 

apoptosis at doses up to 10 μg/ml; however, the affects from nanosilver were greater than 

observed for silver ions. It is unclear what the extrapolated dose to a whole mammal would be 

since there are no pharmacokinetic data on nanosilver. The conservative interpretation of this 

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

toxicity to spermagonia. This effect would be more severe for nanosilver than for silver ion.

4.2.7 Mutagenicity of Nanosilver

Genotoxic potential has been investigated in vivo by measuring micronucleated polychromatic 

erythrocytes (MN PCEs) 28 days after oral administration of carboxymethyl cellulose-coated 

nanosilver with average diameter of 60 nm (minimum diameter of 53 nm and maximum diameter 

of 71 nm) (Kim, et al, 2008). No statistically significant treatment-related increase of MN PCEs 

in the male and female rats when compared to study rats not treated with nanosilver (i.e., 

negative control). This study indicates that nanosilver is not genotoxic in vivo, although a 

limitation of this study is that no measurements were performed to determine if nanosilver 

reached the bone marrow. 

4.2.8 Silver Ions

Humans may also be exposed to silver ions that would be released by AGS-20. Conventional 

silver, and the silver ions it releases, are pesticides. 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, the Agency notes that safe exposure levels for silver 

have been established by several regulatory agencies, including OSHA and EPA. These safe 

exposure levels are based on the common endpoint argyria, a blue-gray discoloration of the skin. 

Silver and compounds, excluding nanosilver, are currently being re-evaluated through the 

Agency’s Registration Review program. 
13

4.2.9 Conclusions from Toxicity Studies

Together, these studies indicate to the Agency that, if sufficient quantities of nanosilver break 

away from AGS-20, and if such nanosilver displays toxicity similar to the nanosilver used in 

these studies, then route-specific exposure to AGS-20 derived nanosilver may result in adverse 

health effects. The inhalation NOAEL of 133 μg/m3 was determined after inhalation of 

nanosilver in rats over 90 days and was based on effects observed in the liver and lungs, and 

systemic accumulation of silver in tissues. The oral NOAEL of 0.5 mg/kg/day was determined 

after oral administration of nanosilver to mice over 28 days and was based on the elevated blood 

enzymes and effects observed in kidney tissues. These NOAELs were deemed to represent the 

lowest inhalation and oral daily-doses for nanosilver that does not cause an effect during shortterm (<30 days) and intermediate-term (1 to 6 months) exposures. 

The nanosilvers used in the 90-day inhalation toxicity and 28-day oral toxicity studies have

physical properties similar to the nanosilver present in AGS-20. The nanosilver sizes in AGS-20 

typically range from 1 to 10 nm (Egger et al., 2009) and some particles in the 50 nm range. The 

nanosilver used in the inhalation toxicity study (Sung et al., 2009) had average diameters 

between 18 to 19 nm (minimum diameter of 2 nm and maximum diameter of 65 nm) and the 

nanosilver used in the 28-day mouse oral toxicity study (Park, et al., 2010) had an average 

diameter of 42 nm (minimum diameter of 25 nm and maximum diameter of 55 nm). Thus, the 

size of nanosilvers in these studies overlaps the size range for nanosilver present in AGS-20. In 

addition, these studies involved uncoated nanosilver similar to the nanosilver present in AGS-20. 

The Agency believes the inhalation and oral toxicity studies described above are sufficient for an 

assessment of the risks from use of the nanosilver in the AGS-20 composite during generation of 

the requisite data because the data establish dose-response target endpoints in female and male 

animals, without animal mortality, for relevant routes of exposure over a duration sufficient to 

evaluate intermediate-term exposures (US EPA, 2002). Because the studies do not establish 

toxicity over all life stages, nor do they evaluate all potential effects, appropriate and relevant 

uncertainty factors are applied as discussed further below. 

4.3 Antimicrobial Resistance

Silver is currently used as a broad spectrum antiobiotic in wound dressings. There is a concern 

that increasing use of silver, such as nanosilver for preserving textiles, may result in more 

bacteria developing resistance to silver and 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 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.
14

The Agency concludes that while development of antibacterial resistance due to the use of 

nanosilver in AGS-20 is possible, the likelihood is low that the levels used in AGS-20 treated 

textiles will lead to the development of widespread bacterial resistance to silver. 

4.4 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.

4.4.1 Calculation of MOE

The MOE is calculated by dividing the toxicological point of departure (POD) by the estimated 

daily dose to which humans will be exposed as expressed by the following:

MOE = POD / Daily Dose

The POD is the lower confidence bound on the lowest experimental dose that showed an effect

in a dose-response study. 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 affects were observed in laboratory animals.

After calculating a MOE from the POD and daily dose, EPA evaluates the risk from exposure to 

a chemical by comparing the calculated MOE to a target MOE. If the calculated MOE is greater 

than the target MOE, then EPA does not have a risk concern. If the calculated MOE is less than 

the target MOE, EPA does have a risk concern. In this case, mitigation measures such as 

engineering controls and/or personal protective equipment (PPE) are employed until the 

calculated MOE exceeds the target MOE. These relationships are summarized below: 

• If calculated MOE > target MOE: risk is not of concern and mitigation is not required

• If calculated MOE ≤ target MOE: risk is of concern and mitigation is required

4.4.2 Point of Departures for AGS-20

Inhalation, oral, or dermal subchronic and chronic toxicology studies are not available for AGS20 or the nanosilver that might break away from textiles treated with AGS-20. In place of these 

studies, the Agency is using results from subchronic inhalation and oral toxicity studies found in 

the scientific literature for nanosilvers that have physical properties similar to the nanosilver 

present in AGS-20. The NOAEL from the 90-day inhalation toxicity study by Sung et al. (2009) 

was used to determine the POD for inhalation exposures to the nanosilver that might break away 

from AGS-20 (Table 3). The NOAEL from the 28-day oral toxicity study by Park et al. (2010) 

was used as the POD for oral and dermal exposures to the nanosilver that might break away from 

textiles treated with AGS-20 (Table 3). 
15

Table 3 – Points of Departures

Exposure Route POD Basis

Inhalation 133 μg/m3 NOAEL of 133 μg/m3 based on the observed effects in rats after 

inhaling nanosilver for 13 weeks (Sung et al., 2009)

Incidental Oral 0.5 mg/kg/day NOAEL of 0.5 mg/kg/day based on the observed effects in mice after 

ingesting nanosilver for 28 days (Park et al., 2010).

Dermal 0.5 mg/kg/day

No subchronic studies are available for dermal toxicity of nanosilver. 

Because of this, a POD was chosen by route-to-route extrapolation 

from the oral toxicity study with a NOAEL of 0.5 mg/kg/day (Park et 

al., 2010).

The Agency’s MOE approach uses mass-based metrics, both for determining the POD and for 

calculating exposure. The Agency 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 nanoparticle risks and therefore acknowledges the potential for limitations 

of mass-based risk estimates.

4.4.3 Target MOEs

The target MOE for continuous, daily inhalation, oral, and dermal exposures to AGS-20 for 

short-term (< 30 days) and intermediate-term (1 to 6 months) durations is 1,000 and is 3,000 for 

long-term (> 6 months) duration exposures (Table 4). 

Table 4 – Target Margins of Exposures

Continuous and Daily Exposure 

Duration

Target MOE

Inhalation Oral Dermal

Short-Term (<30 days) 1,000 1,000 1,000

Intermediate-Term (1 to 6 months) 1,000 1,000 1,000

Long-Term (> 6 months) 3,000 3,000 3,000

Target MOEs are 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, the Agency has 

determined that there is sufficient inhalation and oral toxicity data for nanosilver which can be 

used to determine the potential health effects caused by nanosilver released from AGS-20 (Table 
16

3). However, the database is incomplete with respect to reproductive and developmental toxicity, 

neurotoxicity, immunotoxicity, and mutagenicity. Therefore, the Agency is using the maximum 

10 fold database uncertainty factor to extend the inhalation and oral toxicity data to cover the 

missing information on developmental toxicity, neurotoxicity, immunotoxicity, and mutagenicity

(US EPA, 2002). The Agency is requiring studies investigating these effects in order to complete 

the toxicity database for AGS-20 and any material that leaches from treated textiles. A new risk 

assessment will be conducted when these data are available. In the interim, the Agency believes 

that the 10 fold database uncertainty factor is health protective. Thus, the target MOE for shortand intermediate-term duration exposures is:

Target MOE short- and intermediate-term = 10 (UFA) × 10 (UFH) × 10 (UFD) = 1,000

Because there are no repeated-dose chronic toxicity studies available for evaluating the longterm exposures to nanosilver that might break away from AGS-20, a duration adjustment was 

necessary to extrapolate the available nanosilver subchronic toxicity study results to chronic 

results. This extrapolation was accomplished by using a 3 fold uncertainty factor to account for 

the increase in liver toxicity and bioaccumulation observed for nanosilver between the 28-day 

(Kim, et al, 2008) and 90-day (Kim, et al, 2010) rat studies. Thus, the target MOE for long-term 

duration exposures is:

Target MOE long-term = 10 (UFA) × 10 (UFH) × 10 (UFD) × 3 = 3,000

4.5 Occupational Risk Assessment

EPA expects occupational inhalation and dermal exposures to AGS-20 and the nanoparticles that 

might break away from AGS-20 are likely to occur during the following use scenarios:

1. Mixing, loading, and applying AGS-20 powder during the treatment of textiles; 

2. Preparing textile articles from AGS-20 treated textiles; and 

3. Laundering AGS-20 treated textiles.

EPA evaluates the risk of occupational exposures from mixing, loading, and applying or 

handling pesticide products. Although exposure to AGS-20 during subsequent work activities 

involving AGS-20 treated textiles are occupational (items 2 and 3), these scenarios are addressed 

under the residential risk assessment (see Section 4.5).

4.5.1 Occupational Exposure when Handling AGS-20 Powder

HeiQ submitted an article published in a peer reviewed journal (Demou et al., 2008) where the 

authors measured the occupational inhalation exposures during post-production handling and 

processing of AGS-20 powder. The process monitored was a small-scale test version of the fullscale process that will be used for the production of AGS-20. Airborne particulate concentrations 

were measured using non-specific direct reading instruments such as Condensation Particle 

Counters (CPC), a Dust TrakTM aerosol monitor and a Scanning Mobility Particle Sizer (SMPS), 

which counted the number of particles with diameters between 6 and 673 nm. Although these 

instruments cannot determine the composition of the particles detected, they are often used to 

identify and characterize emissions sources in workplaces where nanoparticles might be present. 
17

In this study, temporal and spatial analysis of particle concentrations and sizes were performed 

during AGS-20 production, maintenance, and handling and packaging. The results indicated that 

the highest particle concentrations of 50,000 particles per cubic centimeter occurred during 

production and that these concentrations were significantly greater than the background particle 

concentrations of 9,000 particles per cubic centimeter on average. (Note - heating system 

combustion byproducts, vehicle exhaust, and electric motors are background sources of 

nanoparticles.) It was reported by the authors that the rate of AGS-20 production was related to 

both the profile and magnitude of the airborne particle concentration. It was determined that 

particle re-suspension was not relevant because airborne particle concentrations did not increase 

when equipment operation and production was not occurring. Manual cleaning of the reactor 

with a vacuum cleaner also resulted in a significant increase in the number of particles in the 6 to 

673 nm range. Transfer of AGS-20 powder during post-production handling and processing 

caused maximum particle concentrations of 15,000 particles per cubic centimetre compared to 

average background particle concentrations of approximately 9,000 particles per cubic 

centimeter.

Workers may be exposed to AGS-20 particles and nanosilver particles that break away from the 

composite particle. If AGS-20 particles remain intact during mixing, loading, and applying (i.e., 

handling), workers would be exposed to the 1,000 nm sized AGS-20 particles (Egger et al, 

2009). Although not conclusive, the submitted literature study suggests that this might be the 

case because the number of particles in the 6 to 673 nm range did not greatly increase above 

background levels during the handling of AGS-20 powder, which would be expected if 

nanosilver were breaking away from AGS-20. However, this study was completed for the AGS20 production process and may not represent conditions when AGS-20 powder is being mixed, 

loaded, and applied during the treatment of textiles. Because of this shortcoming, the Agency is 

using the standard occupational handler unit exposure values for mixing and loading of wettable 

powders, as shown in Table 5, which are provided in the Pesticide Handlers Exposure Database

(PHED) (U.S. EPA, 2011a). Wettable powders were chosen because these powders have a high 

proportion of particles with diameters less than 5,000 nm (Matthews, 2000), which is similar to 

AGS-20 particles with average diameters of 1,000 nm.

Table 5 – Unit Exposures for Mixing and Loading of Wettable Powders (Matthews, 2000)

Personal Protective Equipment (PPE) Level Exposure Route Unit Exposure

No gloves, use of long-sleeve shirt, long pants, 

shoes plus socks

Dermal 3.7 (mg/lb)

Gloves, long-sleeve shirt, long pants, shoes plus 

socks

Dermal 0.17 (mg/lb)

No respirator Inhalation 7.8 (μg/m3/lb)

The values in Table 5 indicate, for example, that if 100 lb of AGS-20 were handled during a 

work day, 370 mg of AGS-20 would reach the skin of a worker who was not wearing gloves. If 

gloves were worn then 17 mg of AGS-20 would reach the skin.
18

4.5.2 Particle Penetration through Respirator Filters when Handling AGS-20 Powder

The penetration of particles through four types of respirator filters was determined for particles 

generated during the production of AGS-20 (Demou et al., 2008). Three of these respirator filters 

were certified to the European Standard EN 143:2000 P3, which indicates that they provide the 

highest level of protection while one filter was certified to the EN 149:2001 P2 standard which 

indicates a lower level of protection. Particle laden air from the AGS-20 production process was 

drawn through each respirator filter and particle concentration measurements were taken on each 

side of the filter using Condensation Particle Counters. The initial chamber flow rate was set at 

one of two levels (1.0 m3

/hr and 2.15 m3/hr) to represent the inhalation rates of adults engaged in 

light and moderate activities. These breathing rates correspond to 6.7 liters per minute (LPM) for 

light activities and 36 LPM for moderate activities. The results indicated that at least 99.89% of 

the incoming particles were retained in the P3 respirator filters and 96.66% retained in the P2 

respirator filters. These results are consistent with other studies cited in the National Institute for 

Occupational Safety and Health Document Approaches to Safe Nanotechnology (NIOSH, 2009) 

which reported very high retention rates for respirator filters challenged with nanoparticles.

4.5.3 Conclusions from the Occupational Exposure Study

The submitted study discussed above provides some useful information regarding occupational 

exposure during post-production handling and processing of AGS-20 powder, but it does not 

provide quantitative data for purposes of estimating exposures from mixing, loading, and 

applying (i.e., handling) AGS-20 powder. EPA is using the PHED values for mixing and loading 

of wettable powders to evaluate the exposure to AGS-20 powder during transfer to shipping 

packages and application to textiles.

4.5.4 Occupational Margins of Exposure

EPA expects that workers will be exposed to AGS-20 powder through the routes of inhalation 

and dermal contact. EPA recognizes the potential for inhalation and dermal exposure to 

nanosilver during laundry drying of AGS-20 treated textiles; however, EPA lacks information on 

the release rate of nanosilver from AGS-20 treated textiles during laundry drying and is therefore 

requiring HeiQ to perform an attrition study to determine this information. While exposure may 

occur during laundry drying, EPA estimates that when compared to exposure through inhalation 

during mixing, loading, and applying (i.e., handling) of AGS-20 powder to textiles, exposure

during laundry drying is of lower significance (see Section 4.6.4). As detailed in the following 

sections, EPA evaluated the risk to workers who mix, load, and apply AGS-20 powder to 

textiles.

Occupational Inhalation Daily-Dose and MOEs

The inhalation dose from exposure to AGS-20 powder was calculated using the following:

Inhalation Daily Dose = Amount of AGS-20 handled per day × Unit Exposure 

Where:

• Amount of AGS-20 handled per day: OPP standard assumption is that 20,000 lb of 

textiles are treated per day at each textile treatment facility and the maximum amount of 
19

nanosilver in AGS-20 that can be applied to textiles is 0.01% silver by weight, thus the 

amount of nanosilver in AGS-20 that is handled per day is 20,000 lb/day × 0.01% ÷ 

100% = 2 lb/day.

• The unit exposure for inhalation is 7.8 μg/m3/lb when no respirator is worn (see Table 5).

• The unit exposure for inhalation is 0.16 μg/m3

/lb when a full-face respirator is worn. This 

value was calculated by dividing 7.8 μg/m3/lb by a protection factor of 50 which was 

recommended in Approaches to Safe Nanotechnology (NIOSH, 2009).

• The unit exposure for inhalation is 0.016 μg/m3/lb when a full-face respirator is worn and 

engineering controls are used. This value was calculated by dividing 0.16 μg/m3

/lb by a 

protection factor of 10. The efficacy of the engineering controls such as local exhaust 

ventilation is dependent upon their specific design characteristic, but local exhaust 

without enclosure can be assumed to result in a 3 to 10 fold reduction in exposure 

(AIHA, 2006; Marquart, 2008; Burgess, 1995) while local exhaust with enclosure can be 

assumed to result in a 30 to 100 fold reduction in exposure (Marquart, 2008; AIHA, 

2006).

Table 6 – Inhalation MOEs for AGS-20 Occupational Handlers

Scenario

Amount of 

Textile 

Treated per 

dayA

Application 

RateB

Amount of 

AI 

handled 

per day

Unit 

ExposureC

(μg/m3/lb 

AI)

Daily 

DoseF

(μg/m3)

MOEG

Mix/Load AGS20 Powder 

Without 

Respirator

20,000 lb 0.01% silver 

by weight 2 lb 7.8 16 10

Mix/Load AGS20 Powder 

With Full-Face 

Respirator

20,000 lb 0.01% silver 

by weight 2 lb 0.16D 0.32 420

Mix/Load AGS20 Powder 

With 

Engineering 

Controls

20,000 lb 0.01% silver 

by weight 2 lb 0.016E 0.032 4,200

A. Standard OPP assumption for textile treatment per manufacturing facility

B. Maximum amount of nanosilver in AGS-20 for treatment of textiles

C. PHED unit exposure value converted to air concentration units based on mean 8 hour TWA

D. PHED unit exposure value divided by 50 for full-face respirator

E. PHED unit exposure value divided by 50 for full-face respirator and divided by 10 for engineering controls

F. Dose = Amount AI Handled × Unit Exposure

G. MOE = POD / Daily Dose (rounded to two significant digits)

The MOEs shown in Table 6 were calculated by dividing the inhalation dose by the POD of 133 

μg/m3

, which is the NOAEL from a 90-day inhalation toxicity study for nanosilver (Sung et al., 

2009). This assumes that AGS-20 behaves like nanosilver after inhalation. When no respirator is 

worn, the MOE is 10 which is less than the target MOE of 1,000 and indicates a risk concern. 

The MOE increased to 420 assuming that full-face respirators are worn, which is also less than 
20

the target MOE of 1,000 and indicates a risk concern. HeiQ recommended that its workers wear 

full-face respirators during manufacture of AGS-20 (MRID 479344-02). If local exhaust 

ventilation engineering controls, which provide a protection factor of greater than 10, in addition 

to the full-face respirator are used, the MOE increases to 4,200 which is greater than the target 

MOE of 1,000 indicating the risk from short- and intermediate-term exposures is not of concern.

Occupational Dermal Daily-Dose and MOEs

The dermal dose from exposure to AGS-20 powder was calculated using the following:

Dermal Daily Dose = (Amount of AGS-20 handled per day × Unit Exposure × Dermal Absorption 

Factor) / Body Weight

Where:

• Amount of AGS-20 handled per day: OPP standard assumption is that 20,000 lb of 

textiles are treated per day at each textile treatment facility and the maximum amount of 

nanosilver in AGS-20 that can be applied to textiles is 0.01% silver by weight, thus the 

amount of nanosilver in AGS-20 that is handled per day is 20,000 lb/day × 0.01% ÷ 

100% = 2 lb/day.

• The unit exposures for dermal are 3.7 mg/lb when no gloves are worn and 0.17 mg/lb 

when gloves are worn (Table 5).

• The dermal absorption factor is 0.1% (see Section 4.2.3). 

• The body weight of an adult is 70 kg which is a standard assumption from the Exposure 

Factors Handbook (U.S. EPA, 1997).

Table 7 – Dermal MOEs for AGS-20 Occupational Handlers

Scenario

Amount of 

AI added or 

handledA

Unit 

ExposureB

(mg/lb AI)

ExposureC

(mg/day)

Daily DoseD

(mg/kg/day)

MOEE

Mix/Load AGS-20 

Powder During Textile 

Treatment

Without gloves

2 lb 3.7 7.4 0.00011 4,500

Mix/Load AGS-20 

Powder During Textile 

Treatment

With gloves

2 lb 0.17 0.34 0.000049 100,000

A. Based on the same assumptions as those used for the inhalation MOE (see Table 6) 

B. PHED unit exposure data for wettable powder (see Table 5).

C. Dermal Exposure = Amount AI Handled × Dermal Unit Exposure

D. Dermal Dose = [Dermal Exposure × Dermal Absorption Factor (0.1%)]/ Body Weight (70 kg)

E. Dermal MOE = POD / Daily Dose (rounded to two significant digits)

The MOEs shown in Table 7 were calculated by dividing the dermal dose by the POD of 0.5 

mg/kg/day, which is the NOAEL from a 28 day oral toxicity study (Park et al., 2010). This 
21

assumes that AGS-20 behaves like nanosilver after dermal absorption. The MOE for dermal 

exposures is 4,500 when no gloves are worn and is 100,000 when gloves are worn, which are 

both greater than the target MOE of 1,000 indicating that the risk from short- and intermediateterm occupational dermal exposures are not of concern.

4.5.5 Conclusions for Occupational Risk

The MOE for occupational inhalation exposure to AGS-20 was 10 assuming that AGS-20 

behaves like nanosilver after inhalation. The MOE increased to 420 assuming that full-face 

respirators are worn and 4,200 when engineering controls in addition to full-face respirator are 

utilized. These MOEs indicate that the risk concern for inhalation exposures to AGS-20 powder 

during handling is mitigated when workers wear full-face respirators and utilize engineering 

controls which provide a protection factor of 10 or greater. The MOE for occupational dermal 

exposure to AGS-20 for a worker who wears a long-sleeve shirt, long pants, and shoes plus socks

was 4,500 without the use of gloves and 100,000 assuming that gloves were worn. These MOEs 

indicate that the risk concern for dermal exposure to AGS-20 powder is not of concern when 

workers wear long-sleeve shirts, long pants, and shoes plus socks. 

There are several uncertainties in the occupational risk assessment. AGS-20 exposure values 

may be different from the PHED unit exposure values for wettable powders since AGS-20 

particle size is approximately 5 times smaller than the particle size for wettable powders. The 

PODs used were based on inhalation and oral toxicity studies completed using nanosilver, not

AGS-20 or the nanosilver that might break away from AGS-20, and thus these PODs may not 

represent the AGS-20 nanosilver-silica composite or the nanosilver found in AGS-20. Due to 

deficiencies in the toxicity studies available for nanosilver, the Agency used an additional 10 

fold database uncertainty factor resulting in a target MOE of 1,000. 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) for purposes of using the oral NOAEL to calculate a POD for dermal toxicity. 

However, the Agency believes that the 0.1% DAF used in calculating a dermal dose is 

conservative because the available human in vivo study indicates that absorption of nanosilver is 

below 0.1% and the in vitro data indicate absorption of nanosilver from intact and abraded 

human skin is substantially below 0.1% (see Section 4.2.3).

Occupational inhalation exposures during mixing, loading, and applying (i.e., handling) AGS-20 

powder can be minimized through the use of engineering controls such as closed system loading 

or local exhaust ventilation. The use of engineering controls as a primary method of reducing 

worker exposure to nanoparticles is discussed in Approaches to Safe Nanotechnology (NIOSH, 

2009). In addition, a secondary method of inhalation exposure control, which was proposed by 

HeiQ, requires workers to wear full-face respirators with high-efficiency filter cartridges (i.e. 

P100) and, assuming that they are properly fitted, these respirators will provide a protection 

factor of 50. Occupational dermal exposures to AGS-20 powder can be minimized by requiring 

workers to wear long-sleeve shirts, long pants, and shoes plus socks. However, because the 

particle size of AGS-20 powder is smaller than the particle size for the wettable powder which 

was used to estimate exposures to AGS-20, gloves and overalls or a Tyvek suit are recommended 

as an additional level of protection when handling AGS-20 powder .
22

If engineering controls and personal protective equipment are used when handling AGS-20 

powder, the Agency anticipates that the inhalation and dermal MOEs will be greater than the 

target MOE of 1,000 for short- and intermediate-term exposures, indicating that the occupational 

risk from AGS-20 will not be of concern during the four year period of conditional registration. 

EPA does not typically consider long-term occupational exposures to antimicrobial preservatives 

used to treat textiles because application of these chemicals does not typically occur on a daily 

basis for more than 6 months. However, if continuous daily production of AGS-20 treated 

textiles occurs for more than 6 months, the MOEs for inhalation and dermal exposures to AGS20 powder are greater than the target MOE of 3,000, indicating that any potential risk from longterm inhalation and dermal exposure to AGS-20 powder would not be of concern. 

4.5.6 Occupational Exposure and Health Data Requirements

EPA is requiring that HeiQ conduct an indoor applicator study to quantify the unit exposure 

values during mixing, loading, and applying AGS-20 powder. EPA will use these values to 

confirm the occupational risk assessment summarized above.

Based on the potential occupational exposures to AGS-20, the Agency has determined that routespecific subchronic tests are required as Tier I studies to confirm the Agency’s determination that 

the risks of this product to workers are not unreasonable. The Tier I health effects testing 

categories include:

• Route-specific subchronic inhalation study in rats with in vivo bone marrow assay and 

functional observational battery, motor activity and detailed neuropathology

• Route-specific dermal toxicity study in rats

• Reproduction and developmental toxicity screening tests in rats

• An in-vitro micronucleus assay for mutations in genetic material

A more detailed description of these data requirements is provided in Appendix A.

4.6 Consumer Risk Assessment

EPA expects consumer exposures to AGS-20, the silver ions derived from AGS-20, and the 

nanoparticles that might break away from AGS-20 could potentially occur during the following 

use scenarios:

1. Inhalation exposure during laundry drying of AGS-20 treated fabrics;

2. Incidental oral exposure to AGS-20 treated fabrics; and

3. Dermal exposure while wearing AGS-20 treated fabrics.

To determine the amount and form of silver that consumers will be exposed to when wearing and 

chewing on AGS-20 treated textiles would require a leaching study. These studies typically 

involve immersing textiles in biological fluids such as simulated sweat and saliva solutions for 

extended periods of time at physiological temperatures (i.e., 98.6 °F or 37 °C) and measuring the 

amount and form of silver released to those fluids. Such “leaching studies” using biological 
23

fluids were not submitted by HeiQ for AGS-20 treated textiles. However, HeiQ submitted two 

leaching studies involving AGS-20 treated textiles. One was completed using ultrapure water 

and the other involved alkaline water with detergents and simulated laundering conditions.

4.6.1 Ultrapure Water Textile Leaching Study

A textile leaching study (MRID 477287-01) was submitted by HeiQ and involved agitating 

AGS-20 treated fabric samples immersed in room temperature (i.e., 68 °F) ultrapure water for 24 

hours. The wash water was analyzed for silver ions using an ion specific electrode (ISE) and for 

nanosilver using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy 

(EDX). According to HeiQ, no ionic silver was detected using ISE and no nanosilver was

detected using SEM/EDX. There were other particles detected, but they were confirmed to be 

non-silver using EDX. 

EPA does not believe that this study is sufficient to support HeiQ’s conclusion that no ionic 

silver and no nanosilver are released from AGS-20 treated textile during use. The ISE method 

that was used to detect silver ions had a detection limit of either 160 μg/L or 800 μg/L, which are

much higher than other available methods such as inductively coupled plasma mass spectrometry 

(ICP-MS) with a silver detection limit of 0.2 μg/L. The magnification used for SEM, which was 

at the 1,000 nm scale, was insufficient to detect the possible presence of nanosilver particles that

are 1-10 nm in diameter. At best, this study supports the limited conclusions that no 1,000 nm

sized AGS-20 composite particles were released and that the release of ionic silver did not 

exceed 160 μg/L.

4.6.2 Alkaline Water and Simulated Laundering Textile Leaching Study

In addition to the ultrapure water textile leaching study mentioned above, HeiQ submitted a 

literature study that examined textiles treated with AGS-20 (Geranio et al., 2009). During this 

study, 9 textiles treated with silver, including two treated with AGS-20, were 1) immersed in 

water at pH 10 with detergent followed by agitation or 2) machine washed using an International 

Standards Organization (ISO) test for color fastness of textiles during laundering to determine 

the effect of pH, surfactants, and bleaching agents on the rate of silver release. The HeiQ 

samples were polyester fabrics treated with AGS-20 by either a surface coating (NP-PES-SURF) 

or by incorporation into the polyester fiber during manufacturing (NP-PES). Samples of the wash 

water were analyzed for silver ions using ISE before and after filtration using 450 nm filters and 

30 kDa membranes (~5 nm) to separate large and small particulate silver from silver ions. The 

ISE used in the Geranio et al. (2009) study reported a detection limit of 9 μg/L. The amount of 

silver retained by the filters was determined using inductively coupled plasma optical emission 

spectroscopy (ICP-OES). 

After immersing the surface coated textile (NP-PES-SURF) in pH 10 water with detergent for 

150 min (dissolution), approximately 15% of the nanosilver was released with 80% as ionic 

silver and 20% retained on a 450 nm filter (Table 8). The amount of silver released during the 

initial ISO color-fastness test (1st washing) of the surface coated fabric was 35% with 80% of the 

released silver retained on a 450 nm filter, 15% had diameter less than 450 nm, and 5% was

composed of ionic silver. Thus, the nanosilver in textiles surface treated with AGS-20 will likely 

transform into ionic silver after exposure to alkaline conditions while coarse silver-containing 
24

particles will likely be released during mechanical washing of these textiles. Geranio at al. 

(2009) did not perform a second or third washing of the surface coated textile. 

For the textile containing AGS-20 incorporated into the polyester fiber (NP-PES), no ionic silver 

was found above the 8 μg/L detection limit during the pH 10 water dissolution test or the ISO 

color-fastness test. Instead, the 1.3 to 1.5% of silver released was retained on a 450 nm filter.

Table 8 – Silver Released During Washing of AGS-20 Treated Textile

Designation in

Geranio et al. 

2009

Designation

in MRID

477287-01

Treatment 

Type

Silver 

Content

μg/g*

Silver Released (%)

Dissolution 1st

Washing

NP-PES-SURF Sample #2 Surface 

Coating 29 15A 35B

NP-PES Sample #3 Incorporation 99 1.5C 1.3C

* Units are in μg silver / g of textile

A. 80% as ionic silver and 20% retained on 450 nm filter

B. 80% retained on 450 nm filter, 15% with diameter < 450 nm, and 5% as ionic silver

C. 100% retained on 450 nm filter

4.6.3 Conclusions Regarding the Consumer Exposures

EPA has concluded that the AGS-20 treated textiles, particularly when surface coated, release 

silver in the form of ionic silver and coarse particulates, but it is not known if these particulates

consist of nanosilver in fibers or coating fragments, aggregates of nanosilver, or precipitates of 

ionic silver. Although Geranio et al. (2009) only reported results for the initial washing of the 

surface coated textile; EPA anticipates that less silver would be released during subsequent 

washings meaning that the initial washing probably released the greatest amount of silver and 

that subsequent washings would release less silver. 

The leaching study performed by Geranio et al. (2009) did not use biological fluids and does not 

directly simulate the release of silver in saliva or perspiration. However, the ISO color-fastness 

test involved the use of detergent, alkaline conditions, steel balls, and physiologic temperature 

(40 °C) to determine the persistence of color in textiles during laundering. EPA concludes that 

while this ISO color-fastness test does not exactly simulate wearing or chewing on textiles, 

because it involved aggressive conditions potentially resulting in greater release than might 

otherwise occur during chewing on or wearing textiles, it does provide a reasonable first estimate 

for the amount silver transferred to the mouth while chewing on and transferred to skin while 

wearing textiles treated with AGS-20. 

EPA has determined that an additional leaching study is required using biological fluids and 

physiological temperatures and includes electron microscopy to characterize any particulate that 

have been released. This study is needed to refine EPA understanding regarding the amount and 

form of silver released from AGS-20 treated textiles.
25

4.6.4 Consumer Margins of Exposure

EPA expects that consumers will be exposed to AGS-20 by the routes of inhalation, dermal, and 

incidental oral exposures. As detailed in the following sections, EPA evaluated the risk to 

children, as the likely most vulnerable subpopulation, from chewing on and wearing textiles 

treated with AGS-20. Because the ratio of dose and skin surface area to the body weight are

greater for children than for adults, evaluating the risk to children is also protective for adults

including workers who process AGS-20 treated textiles.

Consumer Inhalation Daily-Dose and MOEs

EPA recognizes the potential for inhalation exposure to nanosilver during laundry drying of 

AGS-20 treated textiles. However, EPA lacks information on the release rate of nanosilver from 

AGS-20 treated textiles during laundry drying and is therefore requiring HeiQ to perform an 

attrition study to determine this information. While exposure may occur during laundry drying, 

EPA believes that when compared to exposure through dermal and oral contact with AGS-20 

treated textiles, 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 AGS-20 treated textiles 

during laundry drying was calculated using the following:

Inhalation Daily Dose = Amount of AGS-20 in clothing handled per day × Unit Exposure 

Where:

• Amount of AGS-20 in clothing handled per day assumed that one 150 g t-shirt treated 

with 100 ppm of AGS-20 as silver was laundered, thus the amount of nanosilver in AGS20 that is laundered per day is 150 g × 100 mg/kg × kg/1000 g = 15 mg.

• The unit exposure for inhalation is 7.8 μg/m3

/lb when no respirator is worn (see Table 5). 

Table 9 – Inhalation MOEs for Drying AGS-20 Treated Textiles

Scenario Amount of AI 

Laundered per dayA

Unit ExposureB

(μg/m3/lb AI)

Daily DoseC

(μg/m3)

MOED

Unload Clothes Dryer

Without Respirator 15 mg 7.8 0.00026 51,000

A. Amount of AI laundered per day = Amount of AGS-20 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 AI Handled × Unit Exposure

D. MOE = POD / Daily Dose (rounded to two significant digits)

The MOEs shown in Table 9 were calculated by dividing the inhalation dose by the POD of 133 

μg/m3, which is the NOAEL from a 90-day inhalation toxicity study for nanosilver (Sung et al., 

2009). This assumes that AGS-20 released from textiles during drying behaves like nanosilver 

after inhalation. This analysis further assumes that all of the nanosilver from the AGS-20 treated 

textile becomes airborne during a single laundry drying event and that exposure would be similar 

to mixing and loading of wettable powders (U.S. EPA, 2011a). The MOE of 51,000 indicates

that the risk for short- and intermediate-term exposure to laundering one AGS-20 treated textile

per day is not of concern. Up to 510 t-shirts treated with AGS-20 could be laundered per day 
26

without exceeding the target MOE of 1,000 for risk from short- or intermediate-term exposure to 

AGS-20.

Consumer Incidental Oral Daily-Dose and MOEs

Incidental oral exposures were calculated using the following:

Incidental Oral Exposure = Pesticide Content × Cloth Density × Surface Area Mouthed × Saliva 

Extraction Efficiency 

Where:

• The textile contains 100 ppm silver when AGS-20 is incorporated during fiber production 

and 20 ppm silver when AGS-20 is applied as a coating, as proposed in the AGS-20 

application. 

• 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 the area of blanket or shirt sleeve.

• The nanosilver saliva extraction efficiencies for mouthing fabric are based on the results 

of the Geranio et al. (2009) leaching study.

The incidental oral daily-dose was calculated from the incidental oral exposure using the 

following: 

Incidental Oral Daily Dose = Exposure / Body Weight 

Where:

• Exposure is determined in the calculation above.

• The body weight of a toddler (3 years old) is 15 kg which is a standard assumption from 

the Exposure Factors Handbook (U.S. EPA, 1997).

The MOEs for incidental oral exposures were calculated from the incidental oral dose using the 

NOAEL of 0.5 mg/kg/day from Park et al. (2010) as the POD. The MOEs for incidental oral 

exposures are listed in Table 10 and range from 1,100 to 5,700 depending upon the application 

rate and saliva extraction factor used. All of these MOEs are greater than the target MOE of 

1,000 indicating that the risk for short- and intermediate-term exposure to toddlers who chew on 

AGS-20 treated textiles is not of concern. 

Table 10 – Incidental Oral MOEs for Toddlers Exposed to AGS-20 Treated Textiles
27

Application 

Rate (mg/kg)

Treatment Type

Cloth 

Density

(mg/cm2)

Surface 

Area 

Mouthed 

(cm2/day)

Saliva 

Extraction 

Efficiency

(See Table 8)

ExposureA

(mg/day)

Daily DoseB

(mg/kg/day) MOEC

20

Surface Coated 10 100

15% 

(Dissolution) 0.0030 0.00020 2,500

35% (1st

Washing) 0.007 0.00047 1,100

100

Incorporated in 

Fibers 

10 100

1.5% 

(Dissolution) 0.0015 0.00010 5,000

1.3% (1st

Washing) 0.0013 0.000087 5,700

A. Exposure = Application Rate × Cloth Density × Surface Area Exposed × Saliva Extraction Efficiency

B. Dose = [Exposure (mg/day)] / Body Weight (kg)

C. MOE = POD / Daily Dose (rounded to two significant digits)

Consumer Dermal Daily-Dose and MOEs

The dermal exposure was calculated using the following:

Dermal Exposure = Pesticide Content × Cloth Density × Surface Area Exposed × Transfer Efficiency

Where: 

• The textile contains 100 ppm silver when AGS-20 is incorporated during fiber production 

and 20 ppm silver when AGS-20 is applied as a coating. 

• 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 exposed is 5,700 cm2/day, which is the median surface area of clothing 

contacting the skin of a 3-year-old toddler. This value is a standard assumption used in 

OPP risk assessments and was derived from the Child Specific Exposure Factors

Handbook (U.S. EPA, 2008). 

• The cloth-to-skin transfer efficiency was based on the amount of silver released during 

the Geranio et al. (2009) leaching study. 

The dermal dose was calculated from the dermal exposure using the following: 

Dermal Daily Dose = Exposure × Dermal Absorption Factor / Body Weight

Where:

• Exposure is determined in the calculation above. 

• The dermal absorption factor is 0.1% 

• The body weight of a toddler (3 years old) is 15 kg which is a standard assumption from 
28

the Exposure Factors Handbook (U.S. EPA, 1997).

The MOEs for dermal exposures were calculated from the dermal dose using the NOAEL of 0.5

mg/kg/day from Park et al. (2010) as the POD. These MOEs are listed in Table 11 and range 

from 8,800 to 45,000 depending upon the application rate and cloth-to-skin transfer efficiency 

used. These dermal MOEs exceed the target MOE of 1,000 indicating that the risk for short- and 

intermediate-term exposure to toddlers from wearing AGS-20 treated textiles is not of concern.

Although these MOEs were calculated for children, they are protective of adults wearing and 

working with clothing treated with AGS-20, since ratio of skin surface area to the body weight is

greater for children than for adults. 

Table 11 – Dermal MOEs for Toddlers Exposed to AGS-20 Treated Textiles

Application 

Rate (mg/kg)

Treatment Type

Cloth 

Density

(mg/cm2)

Surface 

Area 

Exposed

(cm2/day)

Cloth-to-Skin 

Transfer 

Efficiency 

(See Table 8)

ExposureA

(mg/day)

Daily DoseB

(mg/kg/day) MOEC

20

Surface Coated 10 5,700

15% 

(Dissolution) 0.17 0.000011 45,000

35% (1st

Washing) 0.40 0.000027 18,500

100

Incorporated in 

Fibers 

10 5,700

1.5% 

(Dissolution) 0.085 0.000057 8,800

1.3% (1st

Washing) 0.074 0.000049 10,000

A. Exposure = Application Rate × Cloth Density × Surface Area Exposed × Cloth-to-Skin Transfer Efficiency

B. Dose = [Exposure (mg/day) × Dermal Absorption Factor (0.1%)] / Body Weight (kg)

C. MOE = POD / Daily Dose (rounded to two significant digits)

Consumer Aggregate Daily Dose and MOEs 

The possibility that toddlers could be simultaneously exposed to AGS-20 via the dermal and 

incidental oral routes of exposure while wearing and chewing on AGS-20 treated clothing 

comprises the aggregate assessment. 

The aggregate dose was calculated by adding the daily oral and dermal doses using the 

following:

Aggregate Daily Dose = Daily Oral Dose + Daily Dermal Dose 

Where:

• Incidental Daily Oral Dose is from Table 10

• Dermal Daily Dose is from Table 11
29

The oral and dermal daily doses can be added because they are both evaluated using the NOAEL 

of 0.5 mg/kg/day from Park et al. (2010) as the POD and the target MOE of 1,000. Aggregate 

assessments can also include other sources of exposure such as food and drinking water, and 

other nanosilvers in the market place. There are no anticipated food exposures since AGS-20 is 

not used in food contact applications. Neither AGS-20 nor the nanosilver that might break away 

are anticipated to enter drinking water because these particulates will be removed by 

gravitational sedimentation and adsorption (see Section 5.1.1). Finally, there is insufficient 

information to aggregate exposures to other nanosilvers currently in the market place because the 

Agency does not have information on the composition of the other nanosilvers, their distribution 

in the market place, or use by consumers to determine which exposure scenarios are likely to 

occur together. 

The MOEs for aggregate exposures were calculated from the aggregate daily dose using the 

NOAEL of 0.5 mg/kg/day from Park et al. (2010) as the POD. These MOEs are listed in Table 

12 and range from 1,000 to 3,600 depending upon the application rate, treatment type and cloth 

to skin transfer efficiency. All of these MOEs are greater than the target MOE of 1,000 

indicating that the risk for short- and intermediate-term exposure to toddlers from wearing AGS20 treated textiles is not of concern.

Table 12 – Aggregate MOEs for Toddlers Exposed to AGS-20 Treated Textiles

Application Rate 

(mg/kg)

Treatment Type

Cloth-to-Skin 

Transfer Efficiency 

(See Table 3)

Incidental Oral 

DoseA

(mg/kg/day)

Dermal DoseB

(mg/kg/day)

Aggregate 

DoseC

(mg/kg/day)

Aggregate 

MOED

20

Surface Coated

15% (Dissolution) 0.00020 0.000011 0.00021 2,400

35% (1st Washing) 0.00047 0.000027 0.00050 1,000

100

Incorporated in Fibers 

1.5% (Dissolution) 0.00010 0.000057 0.00016 3,100

1.3% (1st Washing) 0.000087 0.000049 0.00014 3,600

A. Incidental Oral Dose is from Table 10

B. Dermal Dose is from Table 11

C. Aggregate Dose = Incidental Oral Dose + Dermal Dose

D. MOE = POD/Dose where the POD is the NOAEL of 0.5 mg/kg/day from Park et al. (2010)

4.6.5 Conclusions for Risk to Consumers

The MOE for inhalation exposure to nanosilver during laundry drying of a textile treated with 

AGS-20 was estimated to be 51,000, which is not of concern because it exceeds the target MOE 

of 1,000. The MOEs for dermal exposures ranged from 8,800 to 45,000 and the MOEs for 

incidental oral exposure ranged from 1,100 to 5,700, all of these MOEs are greater than the 

target MOE of 1,000 indicating that the risk for short- and intermediate-term exposure to 

toddlers who wear and chew on AGS-20 treated textiles is not of concern. Aggregating the 
30

dermal and oral daily doses for children yielded MOEs ranging from 1,000 to 3,600, which is not 

of concern because they exceed the target MOE of 1,000.

The lowest MOEs, including the 1,100 value for oral exposure and the 1,000 for aggregate 

exposure, were based on the amount of silver released after the initial washing of AGS-20 treated 

textiles in the ISO color-fastness test. EPA anticipates that lesser amounts of silver would be 

released during subsequent washings as other similarly silver-treated textiles showed less silver 

release during subsequent washings (Geranio et al., 2009). While the ISO color-fastness test does 

not exactly simulate wearing or chewing on textiles, it does provide a reasonable estimate for the 

amount silver transferred to the mouth while chewing on and transferred to skin while wearing 

textiles treated with AGS-20. In using this study for the exposure assessment, EPA made the 

conservative assumption that all silver found in this study was in the form of nanosilver whereas 

the study showed the release of coarse silver-containing particles of unknown composition. 

Therefore, using this study to estimate the amount of daily nanosilver release may have 

overestimated the potential for incidental and oral exposures to nanosilver by toddlers and 

children. 

The estimate for the inhalation dose during drying of AGS-20 treated textiles was based on a unit 

exposure value that was derived from pouring kg quantities of wettable powders into mix tanks

and does not represent conditions likely to be encountered during drying of AGS-20 treated 

textiles. EPA anticipates that exposure to AGS-20 during drying of AGS-20 treated textiles is 

likely to be less than a comparable exposure to AGS-20 powder. This is because AGS-20 in 

treated textiles is likely to be associated with textile fibers and these fibers would be vented or 

caught in the lint trap during clothes drying thereby reducing the airborne concentration of AGS20 in comparison to AGS-20 powder.

There are several uncertainties regarding the consumer risk assessment. The POD used was 

based on an oral toxicity study completed using nanosilver, not AGS-20 or nanosilver that might 

break away from AGS-20, and thus the POD may not represent AGS-20 or the nanosilver found 

in AGS-20. The oral toxicity study did not establish toxicity of nanosilver over all life-stages or 

evaluate all potential effects, for this reason the Agency used a maximum 10-fold database 

uncertainty factor when calculating the target MOE, resulting in a target MOE of 1,000. 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) for purposes of using the oral NOAEL to calculate a POD for dermal 

toxicity. 

In the absence of information to the contrary, EPA typically does not consider long-term 

consumer exposures for textiles treated with an antimicrobial preservative because 1) the portion 

of the antimicrobial that is not bound to the textile is available for transfer and is expected to be 

depleted or washed out of the textile in less than 6 months (the remaining antimicrobial is bound 

to the textile and not available for transfer) and 2) because there is a low probability that an 

individual will be exposed to the same antimicrobial on a continuous, daily basis for 6 months 

(the scenario classified as long-term). However, EPA has received comments from the public

regarding long-term exposure to AGS-20 treated textiles. There are limited use scenarios where 

the potential for long-term exposure to AGS-20 treated textiles could be expected. For example, 
31

consumers could seek out textiles treated with AGS-20 because of its unique properties. Another 

example would be use of AGS-20 treated textiles by military personnel where there is a 

probability that they would be exposed to AGS-20 on a daily basis for more than 6 months. In 

the case of the surface applied treatment, given that 35% of the silver leached out after the colorfast test, EPA anticipates that the silver in this product will be depleted or washed out of the 

textile in less than 6 months (the remaining antimicrobial is bound to the textile and not available 

for transfer). In the case of AGS-20 incorporated into fibers, the fact that only 1.5% of the silver 

was removed during the color-fast test indicates that the silver in these textiles could be expected 

to remain in the textile for greater than 6 months. Regardless, the risk from long-term inhalation, 

incidental oral, and dermal exposure to AGS-20 treated textiles would not be of concern as the 

MOEs are greater than the target MOE of 3,000 (Table 4) for textiles treated with AGS-20 

(Tables 9, 10, 11, and 12). 

Although the available data on nanosilver are limited, EPA is able to determine that for the 

period of conditional registration, there is a low probability of adverse risk to children and the 

environment from textiles treated with AGS-20. Thus, the Agency concludes that use of AGS20 will not cause unreasonable adverse effects on the environment during the period when newly 

required data are being developed. 

4.6.6 Consumer Exposure and Health Data Requirements

EPA is requiring that HeiQ conduct textile leaching and laundry drying tests as part of Tier I 

studies to determine the nature and quantity of silver released from AGS-20 treated textiles under 

conditions of use. EPA will use these results to confirm the consumer risk assessment for the 

conditional registration of AGS-20. The Tier I health effects testing categories include:

• Route-specific subchronic inhalation study in rats with in vivo bone marrow assay and 

functional observational battery, motor activity and detailed neuropathology

• Route-specific dermal toxicity study in rats

• Reproduction and developmental toxicity screening tests in rats

• An in-vitro micronucleus assay for mutations in genetic material

The results of these studies will be used to confirm the findings of the risk assessment performed 

using scientific literature data for nanosilver. A more detailed description of these data 

requirements is provided in Appendix A.

If nanosilver is determined to be released during the textile leaching or drying tests as part of 

Tier I testing then the Agency will require route-specific subchronic tests as part of Tier II 

studies to confirm the nanosilver risk assessment. The Tier II health effects testing categories 

include:
32

• Route-specific subchronic oral study in rats with in vivo bone marrow assay and 

functional observational battery, motor activity and detailed neuropathology

• Route-specific dermal toxicity study in rats

• Reproduction and developmental toxicity screening tests in rats

• An in-vitro micronucleus assay for mutations in genetic material
33

V. ENVIRONMENTAL RISK ASSESSMENT

Based on the proposed use pattern of AGS-20, EPA anticipates the following substances could 

enter the environment through washing or disposal processes: 

1. Silver ions released from AGS-20 treated textiles; 

2. AGS-20 particles; and 

3. Nanosilver that might break away from AGS-20 particles.

There are no studies available to characterize the environmental fate or ecotoxicity of AGS-20. 

However, there are studies available in the scientific literature for analogous forms of nanosilver. 

Since nanosilver may be released from AGS-20, the Agency has considered the scientific 

literature studies on nanosilver fate and ecotoxicity relevant to AGS-20.

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. As part 

of these discussions, additional data that EPA is requiring in order to confirm its assessment of 

the environmental risks of AGS-20 are also identified.

5.1 Environmental Fate

HeiQ has not conducted any studies to characterize the environmental fate of AGS-20 or the 

other particles that could be released during machine washing or disposal of AGS-20 treated 

textiles. In lieu of this information, the Agency 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.

5.1.1 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 (see Page 

19 FIFRA SAP, 2009). 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. 
34

5.1.2 Silver Ions

Ionic silver typically has low concentrations in natural waters, in the nanogram per liter range, 

due to its reactivity with chloride, sulifides, and natural organic matter (Andren and Amstrong, 

1999). As with nanosilver, ionic silver is found in sediments and associated with biosolids in 

wastewater treatment plants. 

5.1.3 Impacts to Wastewater Treatment/Septic Systems

There is the potential for nanosilver that might be released from AGS-20 treated textiles to reach 

publically 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. To evaluate 

this potential, HeiQ submitted test results on the impact of AGS-20 to wastewater treatment 

bacteria (MRID 479344-01). This test involved introducing AGS-20 powder and an AGS-20 

liquid formulation used to surface treat textiles (AGS-20 TF) into bottles containing biosolids 

obtained from a wastewater treatment plant. Based on the similarity between the biological 

oxygen demand (BOD) caused by introducing glucose into bottles with AGS-20 and those 

without, there was no impact to the microorganisms in these bottles for AGS-20 loadings from 

3.8 to 188 mg/L (0.76 to 37.6 mg/L as silver) or the AGS-20 TF liquid at loadings from 1 to 50 

g/L over the 26 day test period. Thus, AGS-20 is not expected to adversely impact wastewater 

treatment or septic systems. However, this study was not designed to assess the impacts to 

wastewater treatment from nanosilver that might be released during the washing of textiles 

treated with AGS-20. 

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.

While there are reports suggesting the potential for nanosilver to impact wastewater treatment 

operations, the Agency does not anticipate that registering AGS-20 will lead to negative impacts 

to wastewater treatment systems. This conclusion is based on the small volume of nanosilver 

(i.e., < 4,500 kg/yr as estimated in Section 5.3) expected to be introduced into commerce from 

AGS-20 treated textiles. However, if nanosilver is found to be released from AGS-20 treated 

textiles during leaching studies then EPA will require HeiQ to determine the impact to 

wastewater treatment processes. 

5.2 Environmental Toxicity

HeiQ has not conducted any studies to characterize the ecotoxicity of AGS-20 or the other 

particles that could be released during machine washing or disposal of AGS-20 treated textiles. 
35

In lieu of this information, the Agency is relying on studies available in the scientific literature, 

discussed in the following section, as the basis for determining the ecotoxicity of nanosilver.

5.2.1 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 to the environment from 

registered uses, including the materials preservative use pattern (U.S. EPA, 1993). Silver and 

compounds, excluding nanosilver, are currently being re-evaluated through the Agency’s 

Registration Review program. 

5.2.2 Nanosilver

In contrast, the ecotoxicity information available to assess the potential hazards of nanosilver to 

aquatic life is limited. HeiQ submitted a study on the antimicrobial activity of AGS-20 as 

compared to silver nitrate, which readily dissociates to form silver ions in solution. Compared to 

silver ions, AGS-20 was 10 times less effective at inhibiting the growth of a wide variety of 

gram-negative and -positive microoganisms (Egger et al., 2009). Thus, AGS-20 appears to be 

less toxic to microorganisms than silver nitrate. Although no tests with AGS-20 and aquatic 

organisms were submitted, there are three studies in the scientific literature covering the toxicity 

of nanosilver to aquatic organisms (Table 13). The first study involved determining the 

concentration of silver nitrate and carbonate-coated nanosilver with average diameter of 40 nm 

(minimum diameter of 10 nm and maximum of 200 nm) that affected the photosynthetic activity 

of the freshwater algae Chlamydomonas reinhardtii (Navarro et al., 2008). Although nanosilver 

had lower toxicity than silver nitrate on a silver mass basis, nanosilver had greater toxicity on a 

silver ion basis suggesting that the presence of nanosilver enhanced the toxicity relative to silver 

nitrate. Through further experimentation the authors concluded that the observed effect of 

nanosilver on photosynthetic activity of algae was due to silver ions originating from nanosilver 

during the exposure period. The second study involved determining the acute toxicity of silver 

nitrate and eight different nanosilver formulations on the freshwater flea Daphnia magna and the 

larval-stage freshwater fish Pimephales promelas (Kennedy et al. 2010). Like the first study, 

nanosilver was less acutely toxic than silver nitrate on a total silver content basis. However, after 

accounting for the fraction of nanosilver suspended in solution, nanosilver toxicity was similar to 

that of silver nitrate (i.e., silver ions). For example, the nanosilver obtained from the ASAP 

formulation had an average diameter of 228 nm (minimum of 171 nm and maximum of 310 nm) 

in moderately hard reconstituted water (MHRW); however, after fractionation, the particles with 

average diameter of 1.5 nm (minimum of 1.3 nm and maximum of 1.7 nm) were more predictive 

of acute toxicity. The third study also involved the freshwater fish Pimephales promelas,

however, in the embryonic rather than the larval stage (Laban et al., 2010). Compared to silver 
36

nitrate, nanosilver were significantly less toxic on a total silver basis but similar in toxicity on a 

silver ion basis.

Table 13 – Nanosilver Toxicity to Aquatic Species

Aquatic Organisms Toxicity

Silver Nitrate Nanosilver

Total Silver

(μg/L)

Total Silver

(μg/L)

Dissolved 

Silver (μg/L)

Water 

Characteristics

Freshwater Algae

(Navarro et al., 2008)

1-hr EC50A 20±7 356±62 3.6±0.5 10 mM morpholine 

propanesulfonic 

acid (MOPS), 

buffered at pH 7.52 2-hr EC50 20±9 113±43 1.1±0.4

Freshwater Flea

D. magna

(Kennedy et al., 2010)

96-hr LC50B 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

Freshwater Fish 

Embryo

Pimephales 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 

A. Concentration at which the response is halfway between the baseline and maximum after some specified 

exposure time.

B. Concentration required to kill half the members of a tested population at 96 hrs.

C. Range for eight different silver nanoparticle formulations.

D. Expressed as the fraction of suspended nanosilver.

These studies indicate to the Agency that, if sufficient quantities of nanosilver break away from 

AGS-20 and reach surface water, and if such nanoparticles display toxicity similar to the 

nanosilver used in these studies, then exposure of AGS-20 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). 

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 AGS-20 treated textiles, the data represent 

short-term (e.g., 96 hr) acute exposures and do not characterize the effects from longer-term 

exposure to nanosilver. Given this limitation, as a condition of this registration, the Agency is 

requiring additional testing on the long-term or chronic ecotoxicity effects of AGS-20 and/or 

nanosilver found to be released from AGS-20 during leaching studies.
37

5.3 Aquatic Risk Assessment

EPA expects that AGS-20, silver ions released from AGS-20, and nanosilver that might break 

away from AGS-20 could enter the environment through the following scenarios: 

1. Accidental release during transport

2. Laundering AGS-20 treated textiles

3. Application of wastewater treatment biosolids to agricultural fields

4. After disposing of textiles in landfills or during incineration

Laundering AGS-20 treated textiles is anticipated to be the primary route by which AGS-20, 

silver ions, and nanosilver reach the environment. The silver released during washing of AGS-20 

treated textiles will 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 AGS-20, silver ions, or nanosilver reach the 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. 

As stated in Section 4.6.3, there is no adequate study available to determine the form of silver 

released from AGS-20 treated textiles during clothes washing. However, EPA does not expect 

unreasonable adverse effects to 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 laundering AGS-20 treated textiles, EPA is assuming that nanosilver is the only silver 

compound released. 

5.3.1 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 the Agency's Level of Concern (LOC). An 

LOC is a policy tool that the Agency uses to interpret the RQ and to analyze potential risk to 

non-target organisms and the need to consider regulatory action (U.S. EPA, 2011b).

The concentration of nanosilver in surface water resulting from the use of AGS-20 in textiles 

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:

• Mass of silver release per year: 4,500 kg/year. The value was derived assuming that 300 

million people (U.S. population) purchase one t-shirt treated with HeiQ AGS-20 each 

year. Each t-shirt weighs 150 grams and contains 100 ppm by weight silver.

• Release Days: 365 days per year. This assumes that each t-shirt treated with HeiQ AGS20 releases all its silver as nanosilver over the course of one year. 
38

• Wastewater Removal Efficiency: Ranged from 85 to 99%. These values are based on the 

range provided by Blaser et al. (2008).

• 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). 

• The toxicity value for nanosilver: 1 μg/L based on the LC50 values for Daphnia magna. 

• Level of Concern for the RQ: The presumptive level of concern (LOC) is 0.05 for listed 

(i.e. endangered or threatened) aquatic organisms and 0.5 for non-listed organisms.

The down-the-drain modeling results are shown in Table 14 and these results were divided by 

the LC50 of 1.0 μg/L for Daphnia magna to obtain risk quotients (RQs). The RQ of 0.016 at the 

worst case stream dilution factor of 1.0 and lowest wastewater removal efficiency indicates that 

it is unlikely that the registration of AGS-20 as a textile preservative will lead to adverse effects 

for listed or non-listed aquatic organisms. 

Table 14 – Risk Quotients for Nanosilver in Surface Water

Wastewater 

Treatment 

RemovalA

Stream 

Dilution 

Factor

Surface Water 

Silver Concentration 

(μg/liter)

Risk 

QuotientD RQ Exceeds LOC?* 

85%

1.0 B 0.016 0.016 No

20.1C 0.0007 0.0007 No

99%

1.0 B 0.0011 0.0011 No

20.1C 0.000045 0.00005 No

*The LOC is 0.05 (listed species) and 0.5 (non-listed species). RQs that exceed the LOC are of concern

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. RQ = Surface Water Concentration / LC50 for Daphnia magna (1.0 μg/liter)

5.3.2 Conclusions for Aquatic Risk

The RQs for Daphnia magna exposed to nanosilver ranged from 0.00005 to 0.016, which are not 

of concern for listed or non-listed organisms because they were less than the LOC of 0.5 and 

0.05, respectively. The effect level used to calculate the RQs (i.e., 1.0 μg/L) was chosen to 

represent the most sensitive aquatic organism Daphnia magna and to represent conditions of 

moderately hard reconstituted water (MHRW), which is a test medium representative of surface 

water in the United States. This level has an inherent safety factor ranging from 6 to 50 times 

because researchers found that only a fraction of the nanosilver added to cultures produced the 

toxic effect (Table 13). This analysis assumes that every person in the U.S. would purchase a tshirt treated with AGS-20 resulting in a nanosilver production-volume of 4,500 kg/year. This 

may be an overestimate given that the total mass of silver distributed as a material preservative in 
39

the U.S. during 2009 was less than 6,800 kg, based on EPA confidential records. It was also 

assumed that all the silver contained in these t-shirts would be released as nanosilver even 

though Geranio et al. (2009) found that silver-containing particles with diameters greater than 

450 nm will likely be released during mechanical washing of AGS-20 treated textiles. 

There are several uncertainties regarding the exposure portion of this evaluation. The production 

volume of AGS-20 is unknown since this product is not currently available in the U.S. Because 

of this, EPA made the conservative assumption that every person in the U.S. would purchase one 

AGS-20 treated t-shirt. The nanosilver that could be released from AGS-20 treated textiles were 

assumed to enter the environment through the sanitary sewer system, no evaluation of nanosilver 

in landfills or other routes were evaluated. The rate at which nanosilver entered the sanitary 

sewer systems was assumed to be constant in the down-the-drain model at 4.23×10-5

g/person/day, which does not account for variability in clothes washing patterns among other 

factors. The ecotoxicity values shown in Table 13 are for acute effects and mortality, and do not 

evaluate the long-term exposure to nanosilver. Finally, this assessment only considers silver that 

could be released by AGS-20 and does not include other sources of silver which will contribute 

to the environmental loading of silver. 

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 textiles treated with AGS-20.

5.3.3 Ecological Effects and Environmental Fate Data Requirements

Even though EPA does not anticipate adverse ecological effects from AGS-20 treated textiles 

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 AGS-20 powder and AGS-20 treated textiles. The Tier I 

environmental fate testing categories include:

• Product Characterization and Testing

• Silver Release: Form, Rate and Characteristics

In addition, EPA requires acute avian, fish, and aquatic invertebrate data for labeling packages 

which contain AGS-20 for shipment.

Completion of these Tier I studies will provide AGS-20 product characteristics and determine 

the substance or substances released during laundering of AGS-20 treated textiles. Information 

from these studies will be used to substantiate HeiQ’s claim that no nanosilver is released from 

AGS-20 treated textiles during laundering. However, if nanosilver is found to be released during 

Tier I studies, 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 AGS-20. The Tier II environmental fate and 

ecological effects testing categories include:

• Product Characterization 
40

• Sorption/Desorption Characteristics

• Bioaccumulation Characteristics

• Impacts to Wastewater Treatment

• Wastewater Treatment Removal Efficiency

• Chronic Effects to Sediment Dwelling Organisms

• Terrestrial Plant Toxicity
41

VI. 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 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 a conditional registration with the terms and conditions 

identified in Appendix A is particularly appropriate given EPA suspects that some alreadyregistered like-situated products on the market contain nanosilver as the active ingredient. 

However, 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, EPA intends to seek similar data along with comparable terms on 

already registered products that are identified to contain nanosilver. 

6.1 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 

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. AGS-20 contains an active ingredient, silver nanoparticles also known as nanosilver. The 

AGS-20 silver nanoparticles are not active ingredients in any currently registered 

pesticide (i.e., a “new” active ingredient);

2. Use of AGS-20 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 HeiQ to generate and submit the newly required data;

and 

4. Use of AGS-20 is in the public interest.
42

6.2 Findings and Registration Decision

The Agency is issuing a conditional, four year registration for HeiQ AGS-20 in accordance with 

FIFRA section 3(c)(7)(C) and requiring as a condition of registration specified use conditions as 

well as requiring that the company provide data from a number of studies that will allow the 

Agency to confirm its current assessment of the risks. Specific data requirements are outlined in 

Appendix A. Although these data requirements are specific to HeiQ AGS-20, they form a 

starting point for identifying the types of data the Agency will require for other nanomaterialbased products on a case-by-case basis. 

Consistent with HeiQ’s original and amended applications, label language is required to reduce 

potential exposures. The pesticide label will include the following:

1. The application rates must be less than 100 ppm (mg/kg) or 0.01% silver on a weight basis 

for textile fibers which incorporate AGS-20 and less than 20 ppm (mg/kg) or 0.002% for 

textiles surface coated with AGS-20. 

2. AGS-20 powder shall be applied in facilities equipped with engineering controls such as 

closed system loading or local exhaust ventilation systems that provide, at the least, a 10 fold 

reduction in the concentration of airborne AGS-20 as compared to the AGS-20 concentration 

generated without engineering controls. AGS-20 powder cannot be applied using open 

pouring methods.

3. The following PPE must be worn when handling AGS-20 powder.

• Gloves that are chemically resistant to all of the components of the textile fiber master 

batch or coating formulations to which the AGS-20 powder is added.

• A long-sleeve shirt, long pants, shoes plus socks, and overalls or a Tyvek® suit that cover 

the arms, legs and torso.

• NIOSH certified full-face respirators with P100 or equivalent filter cartridges.

6.3 Basis for Conditional Registration

The Agency’s basis for the conditional registration is as follows:

6.3.1 Data Generation

HeiQ submitted its registration application thinking its product was similar to currently 

registered silver-based antimicrobial pesticide products and provided all of the required productspecific data for this type of application. EPA typically does not require generation of any 

additional generic data to support such an application; applicants fulfill the applicable generic 

data requirements by citing previously submitted data. Over a year after HeiQ submitted its 

application the Agency determined that the nanosilver particles in AGS-20 are a new active 

ingredient. Throughout the application review process, EPA and HeiQ have discussed what data 

might be necessary to register a new active, nanoscale ingredient. Although HeiQ provided EPA 

with some data in an effort to address Agency questions and concerns, until today, EPA had not 

reached a final decision with regard to which types of data would be further required. 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 
43

insufficient time has elapsed from the point at which EPA determined and informed HeiQ of the 

data requirements needed to assess HeiQ’s application for HeiQ to have generated the data. 

EPA conducted an assessment of risks to human health and the environment associated with the 

use of AGS-20 as a materials preservative. However, the majority of the studies used for the risk 

assessment were not conducted with AGS-20 or the nanosilver that might break away from 

AGS-20; rather the studies were conducted using other silver nanomaterials. As indicated in the 

2009 SAP report, nanomaterials such as AGS-20 can be physically and chemically different from 

single molecules or bulk materials or even nanosized versions of the same substance, and these 

differences may impart properties that ultimately affect the potential risks of the nanoscale 

material. Therefore, EPA determined that more extensive product chemistry, toxicology, 

exposure, and environmental data are necessary to confirm EPA’s assessment of the risks from 

the proposed use of AGS-20. Because this list of data requirements are only being finalized with 

today’s action, HeiQ has not yet been able to conduct these studies. Therefore, the Agency 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 the Agency to review them. 

As discussed above, a listing of the studies that are needed for this section 3(c)(7)(C) registration 

of HeiQ AGS-20 are in Appendix A. If HeiQ does not meet the conditions set forth in this 

Decision Document, EPA will issue a notice of intent to cancel HeiQ’s registration under section 

6(e).

6.3.2 Public Interest

As required under FIFRA section 3(c)(7)(C), for the reasons summarized below, the Agency 

believes granting a conditional registration with the terms and conditions specified is in the

public interest. HeiQ provided information to the Agency regarding the economic benefits 

offered by its technology when compared to other options. EPA agrees that this information on

conservation of the environment and consumer benefits contributes 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 antimicrobial products for use as materials 

preservatives. All antimicrobial 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 treated with 

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 antimicrobial silver-based pesticide products currently contain a silver salt, 

[e.g., AgCl or AgNO3]. Compared to the amount of silver in HeiQ’s product, most currently 

registered silver-based materials preservatives allow larger amounts of silver to be added to an 

article in order to provide a sufficient lifetime of activity for antimicrobial treatment. Therefore, 
44

the overall potential environmental loading of silver resulting from the lower-volume use of the 

HeiQ product should be smaller than from a comparable use of currently registered silver-based 

pesticides.

For example, Geranio et al. (2009) reported that commercially available textiles treated with 

electrolytically deposited silver contained 21.6 mg/g silver as compared to textiles treated with 

AGS-20, which contained a maximum of 0.099 mg/g silver. EPA has reviewed the registered 

silver containing pesticides and found that for commercially available products, the amount of 

silver allowed in textiles ranges from 0.03 to 40 mg/g. By conditionally registering HeiQ, EPA is 

allowing a product in the market place where the amount of silver in AGS-20 is restricted to less 

than 0.1 mg/g or 0.01% as silver, which is on the low end of the spectrum for registered silver 

containing products. If AGS-20 displaces the silver-salt based materials preservatives currently 

on the market for comparable textile uses, which have significantly higher silver content, there 

exists the potential for a decrease in the net amount of silver entering the environment. 

Consumer Benefits

A nanosilver materials preservative should maintain its ability to reduce the number of odor 

causing bacteria longer than other silver active ingredients due to an expected gradual and 

controlled release of silver ions from the nanosilver as opposed to the rapid release of for 

example, silver ions from a zeolite structure or the immediate dissolution of the silver salt. While 

it may be that other silver active ingredients achieve greater silver concentrations, it is expected 

that their effects on odor causing bacteria are only short-lived due to rapid release of silver ions. 

In contrast, the Agency believes that AGS-20 will allow slow and controlled release of silver 

ions, potentially resulting in more prolonged antimicrobial activity (U.S. EPA, 2009). Data 

provided to the Agency by HeiQ supports this theory and will be confirmed by the required 

leaching study. Thus, consumers purchasing textiles treated with nanosilver may receive a more 

durable antimicrobial protection for AGS-20 treated textiles as compared to the alternatives even 

though there is less total silver in the AGS-20 treated textile, and such protection is believed to 

have equal ability to reduce the number of odor causing bacteria as other similar products on the 

market that contain conventional silvers. 

Innovation

EPA sees the emergence of nanotechnology as offering potential benefits for society in many 

different fields, including pest control products. The use of nanotechnology in pesticide products 

may allow for more effective targeting of pests and use of smaller quantities of pesticide. These 

could contribute to improved human and environmental safety and could lower pest control 

costs. Therefore, EPA seeks to encourage innovative work to realize these benefits.

In the case of the HeiQ application, EPA’s conditional registration of HeiQ’s AGS-20 product is 

in the public interest in that it will allow an innovative product to reach the market. 

6.3.3 No Unreasonable Adverse Effects

In assessing the potential risks to human health and the environment associated with the 

distribution and use of AGS-20 as a materials preservative, EPA relied on limited data submitted 
45

by HeiQ 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 

AGS-20 during the period of the conditional registration are small. Moreover, EPA expects the 

overall quantity of silver used in 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 following findings:

Risks to Human Health

As discussed above, humans could be exposed to silver ions, to AGS-20, and to nanosilver. With 

respect to silver ions, the Agency 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. These silver-salt preservatives are present in textiles at up to 3% silver 

by weight. Because the maximum amount of AGS-20 that can be used in textiles is limited to 

0.01% silver by weight and because AGS-20 is meant to displace the silver-salt based materials 

preservatives, the Agency concludes that human exposure to silver ions from the use of AGS-20 

and textiles treated with AGS-20 is acceptable. 

With respect to AGS-20, the acute toxicity of AGS-20 is low by all routes of exposure. Because 

there are no subchronic or chronic oral or dermal toxicity studies available for AGS-20 or on the 

nanosilver that might break away from textiles treated with AGS-20, the subchronic or chronic 

toxicities were estimated using studies on analogous nanosilvers reported in the literature. The 

Agency relied on the results from a study in the scientific literature involving the washing of 

AGS-20 treated textiles to estimate exposure to AGS-20 and nanosilver that might break away 

from textiles. The Agency 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 textiles treated with AGS-20. 

Based on all of the foregoing, EPA concludes, with a level of confidence acceptable for the 

period of conditional registration, that there is a low probability of adverse risk to consumers 

from short- and intermediate-term exposure to textiles treated with AGS-20. Thus, the Agency 

concludes that use of AGS-20 will not cause unreasonable adverse effects on the environment

during the period when newly required data are being developed. The Agency does have a risk 

concern for occupational inhalation exposures because the calculated MOEs were less than the 

respective target MOEs. However, HeiQ amended its application to require that workers use 

personal protective equipment and engineering controls when handling AGS-20 powder which 

effectively mitigated EPA’s risk concern.

Risks to the Environment 

The environment could be exposed to silver ions, to AGS-20, and to nanosilver. With respect to 

silver ions, the Agency 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, 
46

were acceptable. These silver-salt preservatives are present in textiles at up to 3% silver by 

weight. Because the maximum amount of AGS-20 that can be used in textiles is limited to 0.01% 

silver by weight and because AGS-20 is meant to displace the silver-salt based materials 

preservatives, the Agency concludes that environmental exposure to silver ions from the use of 

AGS-20 and textiles treated with AGS-20 is acceptable.

With respect to the fate and ecotoxicity of AGS-20, because there are no fate or ecotoxicity 

studies available for AGS-20 or the nanosilver that might break away from textiles treated with 

AGS-20, the fate and ecotoxicity were estimated using studies on analogous nanosilvers reported 

in the scientific literature. Laundering AGS-20 treated textiles was anticipated to be the primary 

route by which AGS-20, silver ions, and nanosilver reach the environment. Because there was no 

adequate study available to determine the form of silver released from AGS-20 treated textiles 

during clothes washing, the Agency assessed impacts to surface waters assuming that nanosilver 

was the only compound released. Environmental exposure was assessed assuming that 300 

million people (U.S. population) each purchased one t-shirt treated with AGS-20 at 0.1 mg/g 

silver and that all the silver in those t-shirts was released during a year as nanosilver. The 

Agency incorporated conservative assumptions when calculating Risk Quotients (RQs) for 

estimating risk to aquatic species from textiles treated with AGS-20. The RQs for Daphnia 

magna exposed to nanosilver ranged from 0.00005 to 0.016, which are not of concern for listed

or non-listed organisms because they were less than the LOC of 0.5 and 0.05, respectively. EPA 

estimates, derived from down-the-drain modeling, of the concentrations of nanosilver resulting 

from the use of HeiQ AGS-20, do not exceed the Agency’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, the Agency concludes that use of AGS-20 will not cause 

unreasonable adverse effects on the environment during the period when newly required data are

being developed.
47

References:

AIHA, 2006. A Strategy for Assessing and Managing Occupational Exposures, 3rd Edition. 

Ignacio, J.S. and Bullock, W.H., American Industrial Hygiene Association, 2006. (see page 270).

AISE/CEFIC, 2005. Human & Environmental Risk Assessment (HERA) on Ingredients of 

Household Cleaning Products, Guidance Document Methodology, International Association for 

Soaps, Detergents and Maintenance Products (AISE) and the European Chemical Industry 

Council (CEFIC), February 2005.

Andren, A.W., Armstrong, D.E. 1999. The Environmental Chemistry and Toxicology of Silver. 

Environmental Toxicology and Chemistry 18:1-2.

Asharani, P.V., Wu, Y.L, Gong, Z., Valiyaveettil, S., 2008. Toxicity of Silver Nanoparticles in 

Zebrafish Models. Nanotechnology 19:255102. 

Bell, R.A., Kramer, J.R. 1999. "Structural Chemistry and Geochemistry of Silver Sulfur

Compounds: Critical Review," Environmental Toxicology and Chemistry 18: 9-22.

Blaser, S.A., Scheringer, M., MacLeod, M., Hungerbühler, K. 2008. Estimation of cumulative 

aquatic exposure and risk due to silver: Contribution of nano-functionalized plastics and textiles. 

Science of the Total Environment 390:396-409.

Bradford, A., Handy, R.D., Readman, J.W., Atfield, A., Mühling, M. 2009. Impact of Silver 

Nanoparticles Contamination on the Genetic Diversity of Natural Bacterial Assemblages in 

Estuarine Sediments. Environmental Science and Technology 43:4530-4536.

Braydich-Stolle, L., Hussain, S., Schlager, J.J., Hofmann, M.C. 2005. In Vitro Cytotoxicity of 

Nanoparticles in Mammalian Germline Stem Cells. Toxicological Sciences 88:412-419.

Burgess, W. 1995, Recognition of Health Hazards in Industry, 2nd Edition, Published by John 

Wiley and Sons, Inc., 1995 (see page 289)

Burkhardt, M., Zuleeg, S., Kägi, R., Sinnet, B., Eugster, J., Boller, M., Siegrist, H. 2010. 

Verhalten von Nanosilber in Kläranlagen und dessen Einfluss auf die Nitrifikationsleistung in 

Belebtschlamm (Behavior of nano silver in wastewater treatment plants and its influence on 

nitrification in activated sludge). Umweltwissenschaften und Schadstoff-Forschung 

(Environmental Sciences in Europe). 22:529-540.

Campbell, P.G.C., Paquin, P.R., Adams, W.J. et al. 2002. "Risk Assessment," Chapter 4 in Silver 

in the Environment: Transport, Fate and Effects, Research Findings of the Argentum

International Conference Series, 1993-2000, A.W. Andren and T.W. Bober, eds., Pensacola, FL, 

USA:SETAC Press, pp. 97-139.

Choi, O. K. and Hu, Z. Q. 2009a. Nitrification Inhibition by Silver Nanoparticles. Water Science 

Technology-WST59.9/2009. (MRID 477953-01)
48

Choi, O.K. and Hu, Z.Q. 2009b. Role of Reactive Oxygen Species in Determining Nitrification 

Inhibition by Metallic/Oxide Nanpoparticles. Journal of Environmental Engineering 135:1365-

1370.

Choi, O., Clevenger, T.E., Deng, B. et al. 2009. Role of Sulfide and Ligand Strength in 

Controlling Nanosilver Toxicity. Water Research 43:1879-1886.

Chopra, I. 2007. The Increasing use of Silver-Based Products as Antimicrobial Agents: A Useful 

Development or a Cause for Concern? Journal of Antimicrobial Chemotherapy 59:587-590.

Demou, E., Peter, P., Hellweg, S. 2008. Exposure to Manufactured Nanostructured Particles in 

an Industrial Pilot Plant. Annuals Occupational Hygiene 52:695-06. (MRID 477575-02)

Egger, S., Lehmann, R.P., Height, M.J., Loessner, M.J., Schuppler, M. 2009. Antimicrobial 

Properties of a Novel Silver-Silica Nanocomposite Material. Applied and Environmental 

Microbiology 75:2973-2976. (MRID 477575-03)

FIFRA SAP, 2009. FIFRA Scientific Advisory Panel Meeting held November 3 - 5, 2009 on the 

Evaluation of Hazard and Exposure Associated with Nanosilver and Other Nanometal Pesticide 

Products Available at

http://www.epa.gov/scipoly/sap/meetings/2009/november/110309ameetingminutes.pdf

Hussain, S.M., Javorina, A.K., Schrand, A.M., et al. 2006. The Interaction of Manganese 

Nanoparticles with PC-12 Cells Induces Dopamine Depletion. Toxicological Sciences

92(2):456-63. 

Geranio, L., Heuberger, M., Nowack, B. 2009. The Behavior of Silver Nanoparticles during 

Washing. Environmental Science and Technology 43:8113-8118.

Gupta, A., Silver, S. 1998. Silver as a Biocide: Will Resistance Become a Problem? Nature 

Biotechnology 16:888.

Kaegi, R., Voegelin, A., Sinnet, B. et al., 2011. Behavior of Metallic Silver Nanoparticles in a 

Pilot Wastewater Treatment Plant. Environmental Science and Technology 45:3902-3908.

Kim, Y.S., Kim, J.S., Cho, H.S., et al., 2008. Twenty-Eight-Day Oral Toxicity, Genotoxicity, 

and Gender-Related Tissue Distribution of Silver Nanoparticles in Sprague-Dawley Rats. 

Inhalation Toxicology 20:575-583.

Kim, Y.S., Song, M.Y., Park, J.D., et al. 2010. Subchronic Oral Toxicity of Silver Nanoparticles. 

Particle and Fibre Toxicology 7:20.

Kennedy, A.J., Hull, M.S., Bednar, A.J. et al. 2010. Fractionating Nanosilver: Importance for 

Determining Toxicity to Aquatic Test Organisms. Environmental Science and Technology

44:9571-9577.
49

Laban, L., Nies, R., Turco, J., et al., 2010. The Effects of Silver Nanoparticles on Fathead 

Minnow (Pimephales promelas) Embryos). Ecotoxicology 19:185-95.

Lankveld, D.P., Oomen, A.G., Krystek, P., Neigh A, Troost-de Jong A, Noorlander CW, Van 

Eijkeren JC, Geertsma RE, De Jong WH. 2010. The kinetics of the tissue distribution of silver 

nanoparticles of different sizes. Biomaterials 31:8350-8361.

Larese, F.F., D'Agostin, F., Crosera, M., et al., 2009. Human Skin Penetration of Silver 

Nanoparticles through Intact and Damaged Skin. Toxicology 255(1-2):33-7. 

Lee, K.J., Nallathamby P.D., Browning, L.M. 2007. In Vivo Imaging of Transport and 

Biocompatibility of Single Silver Nanoparticles in Early Development of Zebrafish Embryos. 

ACS Nano 1:133-1343.

Levard, C., Reinsch, B.C., Michel, F.M., et al. 2011. Sulfidation Processes of PVP-Coated Silver 

Nanoparticles in Aqueous Solution: Impact on Dissolution Rate. Environmental Science and 

Technology 45:5260-5266.

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. 

Marquart et al., 2008. ‘Stoffenmanager’, a Web Based Control Banding Tool Using an Exposure 

Process Model. Annuals of Occupational Hygiene, Volume 52, No. 6 pp. 429-441, 27 June 2008

Matthews, G.A. 2000. Pesticide Application Methods 3rd Edition, Blackwell Science, 2000

Moiemen, N.S., Shale, E., Drysdale, K.J., et al. 2011. Acticoat dressing and major burns: 

Systemic silver absorption. Burns 37:27-35.

Mühling, M., Bradford, A., Readman, J.W., Somerfield, P.J., Handy, R.D. 2009. An 

Investigation into the Effects of Silver Nanoparticles on Antibiotic Resistance of Naturally 

Occurring Bacteria in an Estuarine Sediment. Marine Environmental Research 68:278-283.

NTP, 2002. Final Study Report on the Developmental Toxicity Evaluation for Silver Acetate 

Administered by Gavage to Spraque-Dawley Rats on Gestation Days 6 through 19. NTIS 

PB2002-109208.

Navarro, E. et al., 2008. Toxicity of Silver Nanoparticles to Chlamydomonas reinhardtii. 

Environmental Science Technology 42:8959-8964.
50

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.

Sharma, H.S., Hussain, S., Schlager, J., Ali, S.F., Sharma, A. 2010. Influence of Nanoparticles 

on Blood-Brain Barrier Permeability and Brain Edema Formation in Rats. Acta Neurochir 

Suppl. 106:359-64.

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.

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.

US EPA, 1993. RED Fact Sheet for Silver, EPA-738-F-93-005. EPA Office of Pesticide 

Programs, June 1993.

U.S. EPA. 1997. Exposure Factors Handbook. Vol. I-III. Office of Research and Development. 

Washington, D.C. EPA/600/P-95/002Fa.

U.S. EPA, 2002. A review of the Reference Dose and Reference Concentration Processes. 

EPA/630/P-02/002F. December.

U.S. EPA, 2003. Development Document for the Final Effluent Limitations Guidelines and 

Standards for the Metal Products and Machinery Point Source Category. EPA-821-B-03-001.

U.S. EPA. 2008. Child-Specific Exposure Factors Handbook. National Center for Environmental 

Assessment. Washington, DC; EPA/600/R-06/096F. September.

U.S. EPA, 2009. Literature Review of EPA File Symbol 85249-R, HeiQ AGS-20, Memorandum 

from Tajah Blackburn to Marshall Swindell, DP 366658, July 14.

U.S. EPA, 2011a. PHED Surrogate Exposure Guide, EPA Office of Pesticide Programs, May

2011. Available at: http://www.epa.gov/pesticides/science/handler-exposure-table.pdf

U.S. EPA, 2011b. Technical Overview of Ecological Risk Assessment, Risk Characterization. 

Risk Presumptions for Aquatic Animals. Available at: 

http://www.epa.gov/oppefed1/ecorisk_ders/toera_risk.htm
51

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.
Appendix A - Page 1

Appendix A –

Data Requirements, Enforceable Schedule, and 

Conditions of Registration for HeiQ AGS-20

December 1, 2011
Appendix A - Page 2

I. Introduction

AGS-20 is a silver-silica composite that contains nanosilver sintered onto amorphous silicon 

dioxide (SiO2). The SiO2 fine structure consists of aggregate matrix particles with an average 

diameter of approximately 1,000 nm or 1 micron. Each silica particle contains many small silver 

metal particles with a typical diameter between 1 and 10 nm (Egger et al., 2009) and some

particles in the 50 nm range. Reference to the nanosilver in AGS-20 (whether when part of the 

composite or when broken away from the composite) is to the “new active ingredient” and 

reference to “AGS-20” or the AGS-20 “composite” is to the end use product. 

II. Exposure Pathways

The human and environmental exposures resulting from the use of AGS-20, and use and disposal 

of textiles treated with AGS-20 will largely be a function of what materials are available for 

inhalation or dermal exposure during treatment of textiles or what materials leach or might break 

away from the treated textile during use and disposal. EPA anticipates that humans and the 

environmental will potentially be exposed to the following materials:

1. AGS-20 particles; 

2. Silver nanoparticles that might break away from AGS-20 particles; and 

3. Silver ions released from AGS-20 particles.

EPA expects occupational inhalation and dermal exposures to AGS-20 are likely to occur during 

the following use scenarios:

1. Mix, load, and apply AGS-20 powder during the treatment of textiles 

2. Preparing textile articles from AGS-20 treated textiles

3. Laundering AGS-20 treated textiles

Based on the AGS-20 product use patterns as shown in Figure 1A, the following consumer 

exposure scenarios may be possible for AGS-20 treated textiles:

1. Inhalation exposure during laundry drying of AGS-20 treated fabrics;

2. Incidental oral exposure to AGS-20 treated fabrics; and

3. Dermal exposure while wearing AGS-20 treated fabrics.

Exposures to the environment can also occur if the particles are released into wash water (downthe-drain).
Appendix A - Page 3

Figure 1A – Product Use Analysis for HeiQ AGS-20

III. Data Needed to Confirm the Estimates for Risks of Exposure to AGS-20 

As a condition of registration, EPA is requiring that HeiQ to conduct a number of studies, based 

on a tiered approach, which will allow the Agency to confirm the findings of the risk assessment 

completed for the conditional registration and discussed in the decision document. These tests 

include route-specific toxicity studies for occupational, residential, and environmental exposure 

scenarios. Data must be submitted within four years and according to the schedule provided in 

Table 3A 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. The Agency will evaluate these 

data as they are submitted during the period of the conditional registration to confirm the 

Agency’s determination that the product is not expected to cause unreasonable adverse effects to 

human health and the environment. If EPA determines that HeiQ 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 HeiQ’s registration under 

FIFRA section 6(e). Upon review of the data submitted, if EPA determines there is a risk of 

concern notwithstanding the terms and conditions on this conditional registration, HeiQ will 

need to propose risk mitigation measures to avoid potential cancellation of this registration under 

FIFRA section 6(b).

The following factors were considered in developing the data requirements for AGS-20:

• The nanosilver in AGS-20 is a new active ingredient and is therefore subject to the data 

requirements for the registration of antimicrobial pesticides that are detailed in 40 CFR 
Appendix A - Page 4

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 HeiQ and information from the literature was 

used to tailor the data requirements to the proposed 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 AGS-20 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 

AGS-20:

• 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 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 the Agency 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 AGS-20 is included in Tables 1A 

and 2A. The studies included in Table 1A are considered to be Tier I, meaning that their need is 

not based on the results of other studies. The studies listed in Table 2A are considered to be Tier 

II, because they may or may not be required depending upon the results of the Tier I studies. The 

AGS-20 composite and textiles treated with AGS-20 will be the test materials during Tier I 
Appendix A - Page 5

studies and the test material for Tier II studies will depend on the results of the Tier I leaching 

and dissolution studies. Figure 2A contains a conceptual diagram outlining the Tier I and Tier II 

testing approach.

Figure 2A - Test material and tiered approach for AGS-20. Only the testing category is 

shown; see Tables 1A and 2A for the specific tests required for each material.

IV. NonData-Related Terms and Conditions of Registration

Consistent with HeiQ’s original and amended applications, HeiQ is required to state on the 

pesticide label that the application rates must be less than 100 ppm (mg/kg) or 0.01% silver on a 

weight basis for textile fibers which incorporate AGS-20 and less than 20 ppm (mg/kg) or 

0.002% for textiles surface coated with AGS-20. 

1. HeiQ is required to state on the pesticide label that workers who handle the AGS-20 

powder shall wear the following personal protective equipment (PPE): Gloves that are 

chemically resistant to all of the components of the textile fiber master batch or coating 

formulations to which the AGS-20 powder is added.
Appendix A - Page 6

2. A long-sleeve shirt, long pants, shoes plus socks, and overalls or a Tyvek® suit that cover 

the arms, legs and torso.

NIOSH certified full-face respirators with P100 or equivalent filter cartridges.

In addition to the PPE listed above, AGS-20 shall be applied in facilities equipped with 

engineering controls such as closed system loading or local exhaust ventilation systems that 

provide, at the least, a 10 fold reduction in the concentration of airborne AGS-20 as compared to 

the AGS-20 concentration generated without engineering controls. AGS-20 cannot be applied 

using open pouring methods.

V. Enforceable Schedule

HeiQ agrees to take appropriate steps to secure the data listed in Tables 1A and 2A. As such, 

EPA has prepared an enforceable schedule that is presented in Table 3A. This schedule 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. 

However, unforeseen technical issues may arise due to the unique nature of AGS-20 (a difficultto-test substance), which may cause a delay in testing. If such a case arises, HeiQ 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 HeiQ. In this case, the EPA shall 

submit a written statement to HeiQ 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 HeiQ 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 HeiQ’s registration under FIFRA 

section 6(e). Specifically, HeiQ shall:

1. Submit protocols modified for AGS-20 to EPA’s satisfaction for each of the data 

requirements listed in Table 1A. 

2. Perform each test and submit the results from each test as described in Table 1A and 

2A. 

These items shall be submitted according to the schedule provided in Table 3A. If EPA 

determines that HeiQ has failed to initiate or to submit the required studies by the dates indicated 

in Table 3A, then EPA will issue notice of intent to cancel HeiQ’s registration under FIFRA 

section 6(e).

EPA will use this data to confirm EPA’s determination that the conditional registration of AGS20 will not cause unreasonable adverse effects on the environment, taking into account the terms 

and conditions on the registration.

References:
Appendix A - Page 7

Egger, S., Lehmann, R.P., Height, M.J., Loessner, M.J., Schuppler, M. 2009. Antimicrobial 

Properties of a Novel Silver-Silica Nanocomposite Material. Applied and Environmental 

Microbiology 75:2973-2976. (MRID 477575-03)

FIFRA SAP, 2009. FIFRA Scientific Advisory Panel Meeting held November 3 - 5, 2009 on the 

Evaluation of Hazard and Exposure Associated with Nanosilver and Other Nanometal Pesticide 

Products Available at:

http://www.epa.gov/scipoly/sap/meetings/2009/november/110309ameetingminutes.pdf

The Minimum Information for Nanomaterial Characterization (MINChar) Initiative, 2008. 

Available at: http://characterizationmatters.files.wordpress.com/2008/11/mincharparameters-list.pdf
Appendix A - Page 8

Table 1A - Summary of Tier I Required Data for HeiQ AGS-20

OSCPP Data Requirement (Note 1)

Guideline Number: Study Title Reason for Study Test Material Comments

Product Chemistry

830.1550: Product Identity and Composition

Required for antimicrobial 

pesticides per 40 CFR 161.

AGS-20 The topology of the nanocomposite needs to be fully described. Information is 

needed on how nanosilver is bound to and distributed on the silica matrix.

830.1750: Certified Limits AGS-20

The submitted study only provides data on the average amount of nanosilver 

present in AGS-20. Data are also needed on the upper and lower limits of 

nanosilver present in AGS-20.

830.1800: Enforcement Method AGS-20 Submitted method is based on analysis of total silver. Need method to include 

high resolution images of the nanosilver.

830.1900: Submittal of Samples AGS-20 EPA is requiring samples for independent testing and confirmation of HeiQ test 

results.

830.6313: Stability to Normal and Elevated 

Temperatures, and Metals/Metal Ions AGS-20

Also need to test stability to sunlight, detergents, and salinity. The results of 

these tests will dictate the test substance for the Tier II studies.

830.6317: Storage Stability

AGS-20 Originally submitted studies were not acceptable because they used an 

accelerated method. HeiQ is currently conducting one year studies.

830.6320: Corrosion Characteristics

830.7050: UV-Visible Light Adsorption AGS-20

UV-Vis data will be used to confirm that the material is in fact nano-sized. It 

may also provide data on the range of particle sizes of the nanosilver particles in 

AGS-20. 

830.7840: Solubility AGS-20 Submitted data for pH 7. Need data for pH 5 and 9.

Non-Guideline: Particle Size and Diameter 

(size) Distribution

Required to characterize 

product. AGS-20

A literature study (Egger et al., 2009) provides some particle size and surface 

area data; however, it does not have the quality control information and 

documentation that is required for a product chemistry study. Non-Guideline: Surface Area Determination Required to characterize 

product. AGS-20
Appendix A - Page 9

Table 1A - Summary of Tier I Required Data for HeiQ AGS-20

OSCPP Data Requirement (Note 1)

Guideline Number: Study Title Reason for Study Test Material Comments

Human Exposure

875.1200 and 875.1400: 

Applicator, Indoor Exposure

Required to confirm assessment 

on occupational handler 

exposure during pouring of 

powder.

AGS-20

This study will provide EPA with information useful for evaluating the form, 

route, and level of exposure experienced by workers who handle AGS-20

powder in the process of treating textiles. The exposure data will be used in 

conjunction with the toxicology endpoints to confirm the Agency’s evaluation 

of the risk of applicator exposure to AGS-20 powder. This risk assessment will 

be used to determine what, if any, further mitigation measures may be necessary

to prevent adverse health effects in exposed workers. 

Non-Guideline: Attrition Study

Required to confirm assessment 

on consumer and occupational 

exposure during laundry drying 

of AGS-20 treated textiles.

AGS-20 

Treated 

Textiles

This study will provide EPA with information useful for evaluating the form, 

route, and level of exposure to silver experienced by consumers and workers 

based on the lint produced during drying of AGS-20 treated textiles. 

Non-Guideline: Textile Leaching Study

(Confirm Geranio et al., 2009 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.

AGS-20 

Treated 

Textiles

A leaching study is needed to determine if materials other than silver ions are 

released from AGS-20 treated textiles under conditions of use. HeiQ has 

submitted both a leaching study they conducted and a leaching study from the 

literature (Geranio et al., 2009). HeiQ claims that these studies indicate that 

only silver ions were released from the AGS-20 or textiles treated with AGS-20. 

EPA has reviewed these studies and determined they do not support HeiQ 

claims of no silver nanoparticle release. An additional, follow-up leaching study 

is needed and this study could be done in the manner of Geranio et al. (2009) 

ISO wash-test with the addition of electron microscopy to characterize the 

particulate that is found to be released. The exposure data will be used in 

conjunction with the toxicology endpoints to confirm the Agency’s evaluation 

of the risk of exposure to AGS-20.
Appendix A - Page 10

Table 1A - Summary of Tier I Required Data for HeiQ AGS-20

OSCPP Data Requirement (Note 1)

Guideline Number: Study Title Reason for Study Test Material Comments

Health Effects

870.3465: 90-Day Inhalation Toxicity (Rat)

(Replace Sung et al., 2009 study results)

Modified to include in vivo bone marrow 

assay and functional observational battery, 

motor activity and detailed neuropathology

Conditionally Required for 

antimicrobial pesticides per 40 

CFR 161.340 (Required if use 

results in repeated inhalation 

exposure)

Occupational inhalation 

exposures to AGS-20 powder 

are anticipated during textile 

manufacturing and processing. 

AGS-20

The inhalation study is a route-specific study and is more appropriate than a 

subchronic oral toxicity study. Inhalation studies of shorter duration (e.g. acute 

inhalation studies or repeated exposure inhalation studies less than 90 days) 

would not be sufficient to identify health effects such as pulmonary fibrosis, 

which has been observed with other nanoparticles, and which takes several 

months to develop. Guideline modified to include in vivo bone marrow assay 

and functional observational behavioral battery, motor activity and detailed 

neuropathology.

870.3250: 90-Day Dermal Toxicity (Rat)

(Replace DAF of 0.1% and Park et al. 2010 

study results)

Conditionally Required for 

antimicrobial pesticides per 40 

CFR 161.340 (Required if 

human exposure via skin occurs)

Occupational dermal exposures 

to AGS-20 are anticipated 

during textile manufacturing and 

processing. 

AGS-20

A 90 day dermal toxicity study is needed to assess the risks of these exposures. 

The dermal toxicity study is route-specific, and is more appropriate than a 

subchronic toxicity study via another route (e.g. oral). The use of studies via 

other routes requires dermal penetration studies to estimate dermal absorption.

Modified 870.3550/ OECD TG 421: 

Reproduction/Developmental Toxicity 

Screening Test

Conditionally Required for 

antimicrobial pesticides per 40 

CFR 161.340 (Required for nonfood use products resulting in 

human exposure over significant 

portion of human lifespan)

Occupational exposure to 

workers of reproductive age. 

AGS-20

The combined repeated-dose toxicity study with the 

reproduction/developmental toxicity screening test will provide initial 

information on possible effects on reproduction and/or development. In 

addition, the study may also provide a toxicity endpoint applicable to a risk 

assessment for oral incidental exposure.

Non-Guideline: in vitro micronucleus (MN) 

assay

Required for antimicrobial 

pesticides per 40 CFR 161.340.

Nanosilver known to generate 

radical oxygen species which 

can induce genetic mutations.

AGS-20

Genetic toxicity tests are used to screen chemicals for mutagenic or 

carcinogenic potential. The data from this test will be used to determine if 

AGS-20 is a potential mutagen or carcinogen.
Appendix A - Page 11

Table 1A - Summary of Tier I Required Data for HeiQ AGS-20

OSCPP Data Requirement (Note 1)

Guideline Number: Study Title Reason for Study Test Material Comments

Ecological Effects

850.2100: Avian Acute Oral Toxicity

Required for labeling when 

shipping AGS-20. AGS-20 These data are required for labeling packages which contain AGS-20 for 

shipment.

850.1010: Aquatic Invertebrate Acute 

Toxicity, Freshwater Daphnids

850.1075: Fish Acute Toxicity Test, 

Freshwater and Marine 

Environmental Fate

Non-Guideline: Dissolution Kinetics Study

Required to assess 

environmental exposure from 

wash water.

AGS-20

This is a primary study on the persistence of AGS-20 in the environment and 

the extent of silver ion or nanoparticle release. This test will dictate the test 

substance to be used for the Tier II studies.

Table 2A - Summary of Tier II Required Data for HeiQ AGS-20 

OSCPP Data Requirement (Note 1)

Guideline Number: Study Title Reason for Study Test Material Comments

Product Chemistry

830.7050: UV-Visible Light Adsorption

These studies are required to 

characterize the nanosilver if released 

during Tier I stability, dissolution or 

leaching studies.

Nanosilver

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 Tier II Studies are Required

Health Effects

870.3100: 90-Day Oral Toxicity (Rat)

(Replace Park et al. 2010 study results)

Residential incidental oral exposure to

nanosilver. Nanosilver The oral study is a route-specific study required to evaluate the effects of ingesting nanosilver from incidental oral exposures. 

870.3250: 90-Day Dermal Toxicity (Rat)

(Replace DAF of 0.1% and Park et al. 2010 

study results)

Occupational dermal exposures to 

nanosilver are anticipated during AGS20 treated textile manufacturing and 

processing. Consumer dermal 

exposures to nanosilver are anticipated 

while wearing and mouthing AGS-20 

treated textiles.

Nanosilver

A 90 day dermal toxicity study is needed to assess the risks of the 

exposures to nanosilver if released from AGS-20 treated textiles during 

Tier I studies. The dermal toxicity study is route-specific, and is more 

appropriate than a subchronic toxicity study via another route (e.g. oral). 

The use of studies via other routes requires dermal penetration studies to 

estimate dermal absorption.
Appendix A - Page 12

Table 2A - Summary of Tier II Required Data for HeiQ AGS-20 

OSCPP Data Requirement (Note 1)

Guideline Number: Study Title Reason for Study Test Material Comments

Modified 870.3550/ OECD TG 421: 

Reproduction/Developmental Toxicity 

Screening Test

Children’s exposure to nanosilver while 

wearing and mouthing AGS-20 treated 

textiles. Occupational exposure to 

nanosilver for workers of child bearing 

age.

Nanosilver

The combined repeated-dose toxicity study with the 

reproduction/developmental toxicity screening test will provide initial 

information on possible effects to reproduction and/or the 

developmental effects if nanosilver is released from treated textiles in 

Tier I studies. In addition, the study may also provide a toxicity 

endpoint applicable to a risk assessment for oral incidental exposure.

Non-Guideline: in vitro micronucleus (MN) 

assay

Nanosilver is known to generate radical 

oxygen species which can induce 

genetic mutations.

Nanosilver

Genetic toxicity tests are used to screen chemicals for mutagenic or 

carcinogenic potential. The data from these tests will be used to 

determine if the nanosilver released from the AGS-20 in Tier I studies is 

a potential mutagen or carcinogen.

Ecological Effects

850.1850: Modified Aquatic Food Chain 

Transfer

Required to determine bioavailability 

and biomagnifications. See Note 2

Traditionally use Fish and Oyster BCF to estimate bioaccumulation for 

chemicals, however, mesocosm tests more likely to yield useful 

information.

850.4100: Terrestrial Plant Toxicity

Required to determine effects to plants 

during early critical stages in their 

development.

See Note 2

Nanosilver is likely to partition to biosolids during wastewater 

treatment. If those biosolids are then used in land farming, nanosilver

may impact growth of plants in farm fields.

850.4400: Aquatic Plant Toxicity, Tier 2 Required to determine the toxicity to 

freshwater and aquatic plants. See Note 2

Aquatic plants are the primary source of cellular carbon and chemical 

energy for aquatic environments. Impacts to these primary producers 

would have broad implications for the aquatic food chain.

850.5400: Algal Toxicity, Tier 2 Required to determine the phytotoxicity 

to freshwater and marine algae. See Note 2

Algae are the primary source of cellular carbon and chemical energy for 

aquatic environments. Impacts to these primary producers would have 

broad implications for the aquatic food chain.

Non-Guideline: Measuring the Chronic 

Effects of Freshwater Sediment-Associated 

Contaminants on Chironomus dilutes 

Required to determine chronic impact 

to freshwater sediment dwelling 

organisms.

See Note 2

Silver nanoparticles if released into aquatic environments are likely to 

partition to sediment. Chronic tests on a freshwater benthic emergent 

insect (Chironomus dilutes, formerly Chironomus tentans) with 

epibenthic ecological niche will be used to estimate potential risks to 

freshwater benthic organisms.

Non-Guideline: Measuring the Chronic 

Effects of Freshwater Sediment-Associated 

Contaminants on Hyalella azteca

Required to determine chronic impact 

to freshwater sediment dwelling 

organisms.

See Note 2

Silver nanoparticles if released into aquatic environments are likely to 

partition to sediment. Chronic tests on a freshwater benthic amphipod 

(Hyalella azteca ) with infaunal ecological niche will be used to 

estimate potential risks to freshwater benthic organisms.

Non-Guideline: Measuring the Chronic 

Effects of Marine and Estuarine SedimentAssociated Contaminants on Leptocheirus 

plumulosus

Required to determine chronic impact 

to marine sediment dwelling 

organisms.

See Note 2

Silver nanoparticles if released into aquatic environments are likely to 

partition to sediment. Chronic tests on an esuarine/marine benthic 

amphipod (Leptocheirus plumulosus) will be used to estimate potential 

risks to marine benthic organisms.
Appendix A - Page 13

Table 2A - Summary of Tier II Required Data for HeiQ AGS-20 

OSCPP Data Requirement (Note 1)

Guideline Number: Study Title Reason for Study Test Material Comments

Environmental Fate

Non-Guideline: Rate of Deposition

The rates of aggregation and 

sedimentation are required for 

confirming estimates on the 

environmental fate and potential 

ecological impacts of these materials. 

See Note 2

Knowing the rate of aggregation and sedimentation of the products 

released from textiles would give primary information on the behavior 

of these compounds in the aquatic environment. 

835.1100: Activated Sludge Sorption 

Isotherm

Required to determine wastewater 

treatment removal efficiency. See Note 2

The EPA uses Guideline 835.1110 test results to estimate the removal 

efficiency of a chemical as it passes through a wastewater treatment 

plant.

835.1230: Adsorption/Desorption 

(Batch Equilibrium)

Required to determine partitioning to 

solids. See Note 2

If the material is removed during wastewater treatment, it may be 

deposited on land through the deposition of sludge (i.e. land farming). 

If the material is not removed during wastewater treatment it may be 

released into aquatic environments and may bind to sediment. 

Adsorption/desorption equilibrium studies required to determine the 

mobility of AGS-20 or nanosilver in the environment.

835.1240: Leaching Studies (Soil Column 

Tests)

Required to determine the mobility in 

subsurface environment. See Note 2

The distance that nanoparticles move in soil and groundwater is thought 

to depend on interaction with soil grains. Attachment of nanoparticles to 

soil grains depends on the physical processes of sedimentation, 

interception, and diffusion rather than partitioning to natural organic 

matter. Nanoparticle to soil grain interaction depends on nanoparticle 

diameter, aqueous chemistry, and the arrangement of soil grains and 

must be measured using soil column tests.

850.6800: Modified Activated Sludge, 

Respiration Inhibition Test for Sparingly 

Soluble Chemicals

(Confirm HeiQ screening study)

Required to determine impact to 

wastewater treatment systems.

See 

Note 2

Silver from industrial processes (e.g., film processing) has been shown 

to reduce microbial activity in wastewater treatment systems. The 

purpose of the study is to assess the impact of AGS-20 or nanosilver on 

microbial activity during wastewater treatment. 

Note 1: These guidelines only provide general guidance. Protocols shall be submitted prior to conducting these studies.

Note 2: The test material shall include materials that are released during the stability, dissolution/dispersability, and textile leaching studies. These materials include the 

AGS-20 composite and/or nanosilver released from the AGS-20 composite.
Table 3A – Enforceable Schedule

The AGS-20 composite and textiles treated with AGS-20 will be the test materials during Tier I 

studies. EPA anticipates that data will be developed in a phased approach. Thus, the schedule is 

separated into phases where Phase 1 – Product Characterization and Phase 2 – Product Testing 

will occur prior to developing protocols for Phase 3 – Release Characteristics/Exposure, Phase 4 

– Health Effects, and Phase 5 – Ecologic Effects. 

Tier I: AGS-20 and AGS-20 Treated Textile Testing

Prepare and Submit

Protocols*

Perform Study and 

Submit Results*

Guideline Phase 1 – Product Characterization Q1† 2012 Q1 2012

Non-Guideline Particle Size Distribution

Non-Guideline Surface Area

Phase 2 – Product Testing Q1 2012 Q2 2012

830.6313 Stability

830.6320 Corrosion Characteristics

830.7050 UV-Vis

830.7840/7860 Solubility

Phase 3 – Release 

Characteristics/Exposure

Q3 2012 Q4 2012 - Q1 2013

Non-Guideline Dissolution Kinetics

Non-Guideline Leaching Test of Textile

875.1200 Dermal Exposure-Indoor

875.1400 Inhalation Exposure-Indoor

Non-Guideline Attrition Test - Laundry Drying

Phase 4 – Health Effects Q4 2012 – Q3 2013 Q4 2013 – Q3 2014

870.3465 90-Day Inhalation

870.3250 90-Day Dermal Toxicity

870.3550/

OECD 421

Reproduction/Developmental Toxicity 

Screening Test

Non-Guideline in vitro micronucleus (MN) assay

Phase 5 - Ecologic Effects Q2 – Q3 2013 Q4 2013 – Q1 2014

850.2100 Avian Acute Oral Toxicity

850.1010

Aquatic Invertebrate Acute Toxicity, 

Feshwater Daphnids

850.1075

Fish Acute Toxicity Test, Freshwater 

and Marine

*Submissions are due at end of quarter unless otherwise noted.

†

Q1- Jan thru March; Q2 - April thru June; Q3 - July thru September; Q4 - October thru 

December
Appendix A - Page 15

Table 3A – Enforceable Schedule

The test material for Tier II studies will depend on the results of the Tier I leaching and dissolution 

studies. EPA anticipates that data will be developed in a phased approach. Thus, the schedule is 

separated into phases where Phase 6 – Characterization will occur prior to developing protocols for 

Phase 7 – Health Effects, Phase 8 – Ecological Effects, and Phase 9 – Environmental Fate.

Tier II: Testing for Nanosilver and/or AGS-20 Released during Tier I Tests

Prepare and Submit

Protocols*

Perform Study and 

Submit Results*

Guideline Phase 6 – Characterization Q2 2013† Q3 2013

830.7050 UV-Vis

Non-Guideline Particle Size Distribution

Non-Guideline Surface Area

830.7840/7860 Solubility

Non-Guideline Zeta-potential

Phase 7 - Health Effects Developed during Q4 2013 – Q3 2014

870.3100 90-Day Oral Toxicity Phase 4

870.3250 90-Day Dermal Toxicity

870.3550 Modified Reproduction/Developmental 

Toxicity Screening Test

Non-Guideline in vitro micronucleus (MN) assay

Phase 8 – Ecological Effects Q3 - Q4 2013 Q1 – Q3 2014

850.1850 Modified Aquatic Food Chain Transfer

850.4100 Terrestrial Plant Toxicity, Seedling 

Emergence

850.4400 Aquatic Plant Toxicity, Tier II

850.5400 Algal Toxicity, Tier II

Non-Guideline

Measuring the Chronic Effects of 

Freshwater Sediment-Associated 

Contaminants on Chironomus dilutes 

Non-Guideline

Measuring the Chronic Effects of 

Freshwater Sediment-Associated 

Contaminants on Hyalella azteca

Non-Guideline

Measuring the Chronic Effects of Marine 

and Estuarine Sediment-Associated 

Contaminants on Leptocheirus plumulosus

Phase 9 – Environmental Fate Q3 – Q4 2013 Q1 – Q3 2014

Non-Guideline Rate of Deposition

850.1100 Activated Sludge Sorption Isotherm

835.1230 Adsorption/Desorption 

835.1240 Leaching Studies (Soil Column Tests)

850.6800

Modified Activated Sludge, Respiration 

Inhibition Test for Sparingly Soluble 

Chemicals

*Submissions are due at end of quarter unless otherwise noted.

†

Q1- Jan thru March; Q2 - April thru June; Q3 - July thru September; Q4 - October thru 

December