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Registration of HeiQ AGS-20

EPA Response to Comments Received on

Proposed Decision Document for the Registration of HeiQ AGS-20 

as a Materials Preservative in Textiles

Docket: EPA-HQ-OPP-2009-1012

The public comment period was open from August 12 until September 13, 2010 and a total of 45 total 

comments were received as of October 8, 2010. The comments were listed in order received and each 

assigned a docket number. All comments are contained in this document but have been grouped and 

appear as follows:

A. Citizens - 27 from Citizens 

B. POTWs -3 from POTW Operators (Tri-TAC and Hampton Roads, NACWA)

C. Trade Association - 1 from Trade Association (Copper Development)

D. States - 2 from State Agencies (Wisconsin DHS, Cal DPR)

E. Industry - 3 from industry (DOW, BASF, HeiQ)

F. NGOs - 9 from NGOs (ICTA, NanoCEO, EWG, NRDC, Humane Society, Center for Environmental 

Health, Food and Water Watch, CLF Ventures, and Anonymous)

A. Citizens

Comment 3: J. Ferro (8/19/2010 EPA-HQ-OPP-2009-1012-0021) 

Do not approve use of nanosilver in textiles. When the day of Armagedon comes, and there won't be 

electricity or water to wash our clothes or take baths, we might need the stuff. Not now. We have 

enough illnesses and diseases to deal with and enough things causing the illnesses and diseases.

Response: HeiQ submitted short-term acute animal toxicity testing data for AGS-20 as detailed in the 

Decision Document. These data demonstrated that AGS-20 did not cause mortalities or abnormalities in 

test animals after administration by oral, dermal, and inhalation routes, was moderately to non-irritating 

in skin and eye testing, and was not a skin sensitizer based on dermal testing. Using conservative 

assumptions which overestimate the dose of nanosilver that could potentially be derived from the AGS20 nanosilver-silica composite along with maximum values for risk uncertainty factors, EPA was 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 manufactured treated with AGS-20. Thus, the Agency 

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

the period when newly required data are being developed. Thus, given the available information and 
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using sound scientific risk assessment methods, the Agency believes that use of HeiQ’s AGS-20 will not 

likely cause illness or disease during the period when data are being generated.

EPA has already registered a number of silver-based antimicrobial products for use as materials 

preservatives in textiles. 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 require larger amounts of silver to be added to textiles in 

order to provide a sufficient lifetime of activity for antimicrobial treatment. Therefore, 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. As a result of this information, with this registration there 

exists the potential for a decrease in the net amount of silver entering the environment as compared to 

the currently registered silver-salt based material preservatives. 

Comment 4: K. Mego (8/19/2010 EPA-HQ-OPP-2009-1012-0022)

I strongly oppose the conditional registration of this pesticide. We should require additional product 

chemistry, toxicology, exposure, and environmental data BEFORE it is allowed to enter the stream of 

commerce, not 4 years earlier than that. The adverse effects cannot yet be determined nor measured at 

this time, and therefore the reasonableness of the exposure cannot be determined.

The levels of human and environmental exposure and risks have not yet been measured, therefore the 

likelihood that those levels will be low is false reasoning. Pass-through of nanosilver in fabrics into the 

environment is only one issue. The exposure level created by direct contact with the skin is also 

something of concern. Again, that level of exposure has not been measured, so it cannot yet be 

determined what level is reasonable or likely. Complete studies should be conducted before any 

determination is made regarding this substance.

Response: EPA typically uses “leaching studies” to estimate the amount and form of silver that 

consumers wearing and chewing on AGS-20 treated textiles could potentially be exposed to. 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. HeiQ submitted two “leaching 

studies” one of which used a standard test for the color fastness of textiles during laundering to 

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

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded 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 purpose of 

requiring additional leaching studies is to confirm the results from the submitted studies regarding the 

low rate of nanosilver release from AGS-20 treated textiles. 

Comment 5: M. May (8/19/2010 EPA-HQ-OPP-2009-1012-0023)

I cannot believe that the EPA would approve of this chemical to be used in clothing. One of the 

advertized "benefits" is that such clothing would smell "fresh". There are many people, myself included, 

who have become very chemically sensitive and become sick when exposed to scents used in perfumes, 

fabric softeners, and other things. I have experienced many times being out on a bike path or other 

place where I encounter people whose clothing is permeated with heavy scents and the entire air 

surrounding them makes it difficult for others to enjoy the outdoors. A few years ago I ordered a 

swimsuit from L.L. Bean and it had a "fresh" scent which I tried to wash out. Nothing worked to remove 

the scent and I had to return the suit. I'm afraid of any more chemicals being introduced into our lives 

and the lives of our children and grandchildren who at younger ages suffer from allergies and other 

health problems. You are the watchdog for a clean environment. Do your duty!

Response: AGS-20 has no odor or scent; it is not a perfume or chemical with an odor. Instead it is 

intended to reduce the number of odor causing bacteria. 

Comment 6: E. Vrabel (8/19/2010 EPA-HQ-OPP-2009-1012-0024)

HeiQ AGS-20 should not be approved. No chemical or material should be approved unless there is 

irrefutable evidence that the chemical or material will cause no harm to the environment. The burden of 

proof should be on the *manufacturer* not the regulating agency. It is also important to note that 

*everything* ends up in the environment eventually. The only question is what the impact will be.

Response: The scientific consensus is that nanosilver is harmful to bacteria, which is why it is being used 

as an antibacterial agent. EPA evaluates antimicrobial products to determine if they will perform their 

intended function without causing unreasonable adverse effects on the environment. Using 

conservative assumptions which overestimate the dose of nanosilver that could potentially be derived 

from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty factors, 

EPA was 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 manufactured treated with AGS-20. Thus, the 
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Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on the environment 

during the period when newly required data are being developed.

Comment 8: C. Genung (8/19/2010 EPA-HQ-OPP-2009-1012-0026)

We do not need this product and it's unknown effects on our environment. There is already evidence 

that it is washed out of fabric and enters the environment, in teeny tiny particles that will be very 

difficult to remove or prevent from entering into places we don't want it to go. Four years approval is 

four years too many! We already have soap and water....wash your fabric and yourselves and this is a 

totally unnecessary unknown to add to our already struggling environment!

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA evaluates antimicrobial 

products to determine if they will perform their intended function without causing unreasonable 

adverse effects on the environment. EPA does not generally consider the need for nonpublic health 

pesticides unless the risks from use of such pesticide are of concern and such risks may not be mitigated 

to acceptable levels. Where the risks are not of concern, generally the need for the nonpublic health 

pesticide is determined by consumer demand. Using conservative assumptions which overestimate the 

dose of nanosilver that could potentially be derived from the AGS-20 nanosilver-silica composite along 

with maximum values for risk uncertainty factors, EPA was 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 manufactured treated with AGS-20. Thus, the Agency concluded that use of AGS-20 will not 

cause unreasonable adverse effects on the environment during the period when newly required data 

are being developed.

Comment 9: M. Loomis (8/19/2010 EPA-HQ-OPP-2009-1012-0027)

As a member of the medical community as well as a private citizen and parent, I respectfully request the 

EPA not allow the use of nanosilver in the United States. The long term consequences of nanosilver on 

the many beneficial bacteria necessary for the health of our environment and bodies are potentially 

catastrophic. The potential benefits of nanosilver pesticide do not in any way outweigh the risks of 

harm. Please protect us.

Response: Silver is currently used as a broad spectrum antiobiotic in wound dressings and thus will 

impact beneficial bacteria. However, the present concern is regarding the increase use of silver, such as 

silver nanoparticles for preserving textiles, which may result in more bacteria developing resistance to 

silver and limit its use as an antibiotic agent for wound care. 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. 

In terms of environmental impact, a recent study involved releasing 1 mg/L of silver nanoparticles 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 
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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 silver nanoparticles.

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

nanoparticles 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. 

Comment 10: Anonymous (8/19/2010 EPA-HQ-OPP-2009-1012-0028)

Please reconsider giving conditional approval to the use of nanosilver in consumer products. I am a 

supporter of the precautionary principle that states we should prove that something is safe before we 

allow its use - not the other way around as is being done here. 

There are already tens of thousands of toxic chemicals on the market that have never been tested for 

human safety - we don't need to add to that list. In this case there is a genuine concern and question 

over the potential negative environmental and human health impacts of nanosilver. Please don't allow 

its use in the United States until it is proven safe. Thank you.

Response: The scientific consensus is that nanosilver is harmful to bacteria, which is why it is being used 

as an antibacterial agent. EPA evaluates antimicrobial products to determine if they will perform their 

intended function without causing unreasonable adverse effects on the environment. HeiQ submitted 

results from testing of AGS-20 to determine the product identity and composition, physical and chemical

properties, and acute health effects. EPA reviewed the 24 submitted test results and determined that 17 

were acceptable. HeiQ also submitted five additional studies covering the amount of silver released 

from and the efficacy of AGS-20 treated textiles, the occupational exposures to AGS-20, and potential 

impacts to wastewater treatment.

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

Comment 11: M. McGuire EPA-HQ-OPP-2009-1012-0029)

I am very concerned with the proposed application to textiles as this will allow massive amounts into the 

environment without knowing what this product can actually do once introduced to the environment. I 

would expect a new technology such as this to be required to undergo stringent testing PRIOR to being 

used massive quantities. The unknown impact on sewage processing plants and the treatment of the 

water should be vigorously tested.
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Response: The maximum amount of AGS-20 that can be used in textiles is limited to 0.01% silver by 

weight. As to the total volume of nanosilver that will enter the market place as a result of registering 

AGS-20, this value is unknown at this time. However, based on Agency confidential records, the total 

mass of silver distributed as a material preservative in the United States during 2009 was less than 6,800 

kg. The Agency estimated that 4,500 kg/yr of AGS-20 nanosilver may be used in the unlikely event that 

every person in America was to purchase one t-shirt treated with AGS-20. While this volume is not 

insignificant, it is small relative to the approximately 500,000 kg of silver that was released into the 

environment from other industry sectors during 2008 according to the EPA’s Toxic Release Inventory.

There is the potential for silver nanoparticles 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. Once entrained in the biosolids, the silver nanoparticles could 

serve as a long term source of ionic silver which may 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. This test involved introducing AGS-20 powder and an AGS20 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. Although this 

result suggests that the silver in AGS-20 would not be expected to negatively impact wastewater 

treatment systems, it is unclear if the 26 day test period was sufficient time to evaluate this impact given 

that the rate of ionic silver released from AGS-20 is unknown. 

There are contradictory reports in the scientific literature regarding the impact of silver nanoparticles 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. 

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. 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) 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. 

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 
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factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

Comment 12: Anonymous (8/19/2010 EPA-HQ-OPP-2009-1012-0030)

I think approving this Nanosilver is not a good idea. The potential allergic reactions as well as general 

decline of hygience and potential risks to others. It may also mislead some who have diseases. I 

remember there was a time when I had some sort of allergic reaction and the doctors asked me if I had 

used a new laundry detergent, type of underwear etc...I am now wondering if this may have been a 

cause. What do the track records in other countries read? We should not trust everything that is touted 

as good.

Response: HeiQ submitted short-term acute animal toxicity testing data for AGS-20 as detailed in the 

Decision Document. These data demonstrated that AGS-20 did not cause mortality or abnormalities in 

test animals after administration by oral, dermal, and inhalation routes, was moderately to non-irritating 

in skin and eye testing, and was not a skin sensitizer based on dermal testing. Thus, AGS-20 is not 

anticipated to cause allergic reactions in healthy humans. It should also be noted that nanosilver is being 

used in wound dressings for patients suffering from burns.

Comment 13: Anonymous (8/19/2010 EPA-HQ-OPP-2009-1012-0031)

Please do not allow this! We live in a world full of chemicals, pesticides, and additives. It is becoming 

harder and harder to control what we put in and on our bodies. Although we are thankfully able to make 

choices about foods and cosmetics, it worries me that manufactures will follow suit with this decision 

and that it will become the standard in clothing. Environmental toxins play a part in our health and the 

health and safety of our children. Let's go back to the basics! We've lived centuries without this, why 

start adding it to fabrics now?

Response: There is no evidence to indicate that registration of AGS-20 will lead to it becoming standard 

in clothing. EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand.

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.
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Comment 14: M. Pescatore (8/19/2010 EPA-HQ-OPP-2009-1012-0032)

I am writing to voice my opposition to the use of nanosilver on fabrics. This is an unnecessary poison to 

be put on fabrics which will have direct contact with our skin. If nanosilver washes out in the laundry, it 

will be polluting our ground and water systems, and who is to say that sweating and open pores will not 

allow this substance to seep into our bodies. Why, when the public is so concerned with going green, 

would the EPA want to approve the use of this chemical. We need less chemicals, not more.

Response: EPA typically uses “leaching studies” to estimate the amount and form of silver that 

consumers wearing and chewing on AGS-20 treated textiles could potentially be exposed to. 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. HeiQ submitted two “leaching 

studies” one of which used a standard test for the color fastness of textiles during laundering to 

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

The rate at which silver nanoparticles transform into ionic silver determines the length of time that 

these particles will reside in the environment. Although there are studies reporting that silver 

nanoparticles 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) to have undetectable 

rates of nanosilver to ionic silver transformation. These stabilized nanosilver-sulfide complexes are likely 

to partition to sediments rather than remain suspended in water due to gravitational settling and 

coagulation processes. Likewise, nanosilver is anticipated to partition to biosolids during wastewater 

treatment but may also be released into the environment through 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. 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. 
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EPA has already registered a number of silver-based antimicrobial products for use as materials 

preservatives in textiles. 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 require larger amounts of silver to be added to textiles in 

order to provide a sufficient lifetime of activity for antimicrobial treatment. Therefore, 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. As a result of this information, we believe AGS-20 is 

expected to displace the silver-salt based materials preservatives, which have significantly higher silver 

content, and if so, with this registration there exists the potential for a decrease in the net amount of 

silver entering the environment.

Comment 15: Anonymous (8/19/2010 EPA-HQ-OPP-2009-1012-0033)

This is not a very well-thought out idea. I'll just cite one example: the use of synthetic fertilizer and the 

use of pesticides. The fertilizer and pesticides have been linked to neuro-muscular deterioration such as 

Parkinson's Disease. These links, of course, were not detected for several generations. The testing on 

this nanosilver product is incomplete and definitely not longitudinal. Hint: wash your clothes frequently 

and there will be no problem with germs, odor, etc. What a complete waste of money for something 

that may have catastrophic side-effects.

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand.

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. 

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.

Comment 16: Anonymous (8/19/2010, EPA-HQ-OPP-2009-1012-0034)
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I am against Nanosilver being given conditional approval. It allows a pesticide into the environment for 

four years which could present a danger for humans and the environment. This is not a product that 

saves lives. There is no need to rush and give it conditional approval while it is being tested.

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand. HeiQ 

submitted results from testing of AGS-20 to determine the product identity and composition, physical 

and chemical properties, and acute health effects. EPA reviewed the 24 submitted test results and 

determined that 17 were acceptable. Furthermore, HeiQ also submitted five studies covering the 

amount of silver released from and the efficacy of AGS-20 treated textiles, the occupational exposures 

to AGS-20, and potential impacts to wastewater treatment. Thus, safety testing of AGS-20 was 

performed. 

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

Comment 17: T. Pruitt (8/19/2010, EPA-HQ-OPP-2009-1012-0035)

No long drawn out speeches - just a NO for putting this nanosilver ingredient in our clothing. Being too 

lazy to take care of one’s own clothing and hygiene is not reason enough to introduce more chemicals 

into our bodies and environments. Do we really think our pores don't allow such things into our system. 

Next thing we know we'll be trying to figure out why some new form of disease has been 

introduced....This is just not a necessary evil

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand. The potential 

for penetration of nanosilver through skin was included in EPA’s evaluation of the risk from exposure to 

AGS-20 treated textiles. This was based on 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 

dermal absorption factor (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. 
December 1, 2011

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where EPA assumed that 0.1% of the nanosilver would cross the skin. 

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

Comment 18: Anonymous (8/19/2010 EPA-HQ-OPP-2009-1012-0036)

I am opposed to the EPA's approval of the use of nanosilver on fabric. There are unknown health risks 

related to nanosilver. I ask that the EPA oppose the use of nanosilver for our own safety.

Response: EPA used the best available science to determine the risk posed by the nanosilver in AGS-20, 

which included evaluating the effects caused by feeding nanosilver to test animals for periods of up to 

90 days. It is not possible to determine all possible health effects for all populations at this time. 

However, 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. Although the database is incomplete with respect to reproductive and developmental 

toxicity, neurotoxicity, immunotoxicity, and mutagenicity, 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.

Comment 19: R. Day (8/19/2010 EPA-HQ-OPP-2009-1012-0037)

If the EPA's intent and purpose is to protect the environment and the population of the United States, 

then how does it make any sense to release a product that doesn't have complete health hazard testing 

into the market and have the test results completed while the product is already on the market. What 

happens if it's found out 3 years from now that nanosilver is highly toxic, and it's been washing off of 

clothes and into the water system for the past 3 years? The effects would be irreversible. Where is the 

logic in releasing this product without it being fully tested for the harm it could have on public health 

and the environment!? Any product, no matter what it is, should have complete testing before it's 

released to ensure it will not effect the environment or the public? If it were to be released untested, it 

only stands to put more money in the pocket of big business at the expense of the consumer and the 

population, that is, if it is harmful to them. It should either be test completely before it's marketed, or 

not marketed at all.
December 1, 2011

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Response: There was sufficient health hazard testing to conclude that AGS-20 is not highly toxic. HeiQ 

submitted short-term acute animal toxicity testing data for AGS-20 as detailed in the Decision 

Document. These data demonstrated that AGS-20 did not cause abnormalities in test animals after 

administration by oral, dermal, and inhalation routes, was moderately to non-irritating in skin and eye 

testing, and was not a skin sensitizer based on dermal testing. Using conservative assumptions which 

overestimate the dose of nanosilver that could potentially be derived from the AGS-20 nanosilver-silica 

composite along with maximum values for risk uncertainty factors, EPA was 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 manufactured treated with AGS-20. Thus, the Agency concluded that use of 

AGS-20 will not cause unreasonable adverse effects on the environment during the period when newly 

required data are being developed.

Comment 20: L. Courtney (8/19/2010 EPA-HQ-OPP-2009-1012-0038)

The purpose of the Environmental Protection Agency is to protect the environment of the United States, 

not the profits of clothing manufacturers. Please do not grant approval, now or ever, to this completely 

unnecessary use of the pesticide HeiQ AGS-20, antimicrobial nanosilver. Evidence is already mounting 

that this substance will have an adverse environmental impact, and the consequences for human health 

are as yet unknown. 

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand. EPA has

already registered a number of silver-based antimicrobial products for use as materials preservatives in 

textiles. 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 require larger amounts of silver to be added to textiles in order to provide a 

sufficient lifetime of activity for antimicrobial treatment. Therefore, 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. As a result of this information, with this registration there exists the potential for a decrease in 

the net amount of silver entering the environment as compared to the currently registered silver-salt 

based material preservatives.

Comment 21: P. Smith (8/19/2010 EPA-HQ-OPP-2009-1012-0039)

As a consumer I do not support applying chemicals to any materials that would come into contact with 

the skin. If a product is labeled as no nanosilver, I would purchase it instead. If you do approve 

nanosilver to be applied to a product, please make sure you label these products so we have a choice in 
December 1, 2011

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not purchasing them. I'm shocked in this day and time that this agency would even consider looking at 

this concept considering our already chemical-laden society full of sick people living in a corrupted 

environment who just need to get back to basics. Can't you put yourselves in our shoes (without 

nanosilver)? If you can't think for all Americans, at least consider your own health and that of your own 

family.

Response: Consumers will be informed where there are marketing claims provided by product 

advertising. EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand.

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

Comment 22: Mother Raphaela (8/19/2010 EPA-HQ-OPP-2009-1012-0040)

Our environment is already polluted by innumerable contaminants which we may or may not be able to 

neutralize. The members of our monastery are unanimous in their opposition to adding a known 

pesticide (read poison) to fabric that will be washed (traces added to ground water) and ultimately end 

up in land fills. While perhaps the immediate effects on humans may not be noticable, if already tests 

are indicating stunted growth in plants, the cumulative effect (especially given the number of toxins 

already present) to plants, animals and humans should not be risked. At some point we will tip over a 

balance point and our small planet will no longer be a hospitable place for life.

Response: Based on our review as detailed in the decision document, we believe that registration of 

AGS-20 has the potential to reduce environmental loading of silver. EPA has already registered a number 

of silver-based antimicrobial products for use as materials preservatives in textiles. 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 

require larger amounts of silver to be added to textiles in order to provide a sufficient lifetime of activity 

for antimicrobial treatment. Therefore, 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. As a 

result of this information, with this registration there exists the potential for a decrease in the net 
December 1, 2011

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amount of silver entering the environment as compared to the currently registered silver-salt based 

material preservatives.

Comment 23: Anonymous (8/19/2010 EPA-HQ-OPP-2009-1012-0041)

I cannot believe that this agency that is charged with the enormously important task of protecting the 

citizens of this country would even consider allowing the use of pesticides in clothing-- especially 

without having done proper study of the material. We do not need more chemicals and pesticides in our 

environment. It is bad enough that harmful endrocine disrupters like BPA and pthalates are allowed to 

be put in products. This would be taking a step in the WRONG direction. We need to be moving toward 

products that are cleaner and contain LESS harmful chemicals. It would be a crime in my mind to allow 

this in the United States. If this happens, it will confirm to me and many others what we have suspected 

all along-- that the EPA can be persauded by lobbyists and bought by big corporations. That your real 

concern is not for the citizens of this country, but padding your own wallets. Shame on you!

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand. In taking this 

action, EPA has the expectation of reducing the amount of silver entering the environment. EPA has 

already registered a number of silver-based antimicrobial products for use as materials preservatives in 

textiles. 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 require larger amounts of silver to be added to textiles in order to provide a 

sufficient lifetime of activity for antimicrobial treatment. Therefore, 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. As a result of this information, with this registration there exists the potential for a decrease in 

the net amount of silver entering the environment as compared to the currently registered silver-salt 

based material preservatives.

Comment 25: Anonymous (EPA-HQ-OPP-2009-1012-0043)

Please do not approve the use of nanosilver in clothing. We do not need another chemical on our skins 

and in our water systems. We are living in a stew of chemicals already and can simply wash our clothes

to keep them fresh.

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 
December 1, 2011

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consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand. The potential 

for penetration of nanosilver through skin was included in EPA’s evaluation of the risk from exposure to 

AGS-20 treated textiles. This was based on 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 

dermal absorption factor (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.

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

Comment 27: Anonymous (8/23/2010 EPA-HQ-OPP-2009-1012-0045)

Please do not grant conditional approval for "HeiQ AGS-20." Nanoparticles have great potential to 

positively contribute to our lives; however, their unique properties also mean that we do not currently 

know enough about their effects on human health or the environment to authorize their use. We can 

not afford to simply "wait and see" if the effects are damaging, as we have with so many other 

technological advances. As a 22 year old, and part of the generation upon whom the "fate of the world" 

has begun to fall upon, I am deeply concerned about this conditional approval and hope you will not 

grant it. Thank you.

Response: The Agency is not taking a “wait and see” approach with nanosilver. EPA evaluates 

antimicrobial products to determine if they will perform their intended function without causing 

unreasonable adverse effects on the environment. EPA does not generally consider the need for 

nonpublic health pesticides unless the risks from use of such pesticide are of concern and such risks may 

not be mitigated to acceptable levels. Where the risks are not of concern, generally the need for the 

nonpublic health pesticide is determined by consumer demand.

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.
December 1, 2011

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Comment 28: C. Landerg (8/23/2010 EPA-HQ-OPP-2009-1012-0046)

I am a private citizen of the U.S. I am concerned about the use of nanotechnology, in this case, 

nanosilver being used in consumer goods. Actually, I am against it altogether. The ability of nano 

particles to move, freely and radically, within organisms, including our bodies, HAS to be studied further.

We can look at TEFLON as good example of a technological product that was not studied extensively or 

properly. Now we know that using it on cookware is dangerous. 

The same with margarine which we now know is harmful to people. The coating inside microwave

popcorn bags is harmful. The "fake butter" served on popcorn in movie theaters is harmful. The list goes 

on. 

I personally will not buy any piece of clothing/fabric that has been treated with nanosilver and I certainly 

hope that, if you allow nanosilver to be used., the product will be so labeled.....so that we can protect 

ourselves.

Response: Consumers will be informed where there are marketing claims provided by product 

advertising. EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand.

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

Comment 29: Brad Kahland (9/13/2010)

Dear Mr. Kiely,

By chance, I just learned of the possibility that the EPA may conditionally register a pesticide product 

containing nanosilver as a new active ingredient for a period of 4 years. The antimicrobial pesticide 

product, HeiQ AGS-20, is a silver-based product that is proposed for use as a preservative for textiles.

I am HIGHLY concerned about the research data I have seen showing the real danger of these nanosilver 

particles washing out into the environment and causing unknown and potentially devastating damage to 

other, potentially helpful, bacteria in our environment.

I am strongly opposed to any approval of nanosilver antimicrobial products.
December 1, 2011

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Not knowing who at the EPA receives public comment on this topic, I must ask, please forward this email 

to anyone who receives public comment on this important topic.

Thank you for your stewardship of our public environment.

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand.

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

Silver is currently used as a broad spectrum antiobiotic in wound dressings and thus will impact 

beneficial bacteria. However, the present concern is regarding the increase use of silver, such as silver 

nanoparticles for preserving textiles, which may result in more bacteria developing resistance to silver 

and limit its use as an antibiotic agent for wound care. 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. 

In terms of environmental impact, a recent study involved releasing 1 mg/L of silver nanoparticles 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 silver nanoparticles.

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

nanoparticles 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.

Uncategorized Citizen Comments

Comment 7: Anonymous (8/19/2010 EPA-HQ-OPP-2009-1012-0025)

I do not want nanosilver in my clothes. What is wrong with you people putting pesticides in clothing?

Comment 24: Anonymous (8/19/2010 EPA-HQ-OPP-2009-1012-0042)
December 1, 2011

Page 18 of 55

I am not in any govt office or organization but I do not want more chemicals in my clothing or water. 

Please do not approve this!!!!

Comment 29: M. Quinn (8/24/2010 EPA-HQ-OPP-2009-1012-0047)

PLEASE KEEP NANOSILVER OUT OF CLOTHING!!

We have more than enough toxins in our environment.

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand. 

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

POTWs

Comment 35: Chris Hornback, National Association of Clean Water Agencies (NACWA) (9/13/2010 EPAHQ-OPP-2009-1012-0053)

1. NACWA Comment: Unfortunately, since this conditional registration was not released in the Federal 

Register, many stakeholders, including many wastewater treatment plants that could be impacted by 

this product, will not have an opportunity to provide comments.

Response: The HeiQ Decision Document was not posted to the Federal Register because there was no 

statutory requirement to do so. However, to provide transparency in Agency decision making, the 

document was posed to the Pesticides Public Regulatory Docket for public comment. Postings to the 

public docket are sent via an automated email service, which can be accessed by going to 

http://www.epa.gov/oppfead1/cb/csb_page/form/form.html.

2. NACWA Comment: “However, given that the proposed decision document also indicates that silver 

ionization is greater for nanoscale particles due to an increase in surface area, the supposition of a lower 

environmental silver exposure resulting from nanosilver products may be false. No studies have been 

provided comparing the environmental exposure resulting from conventional silver-based pesticides 

and nanosilver pesticides, so there are no data to support the hypothesis that the overall environmental 

exposure is lower with nanoscale silver products.”
December 1, 2011

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Response: The decision document states that “As the size of silver particles decreases...the potential for 

releasing silver ions increases, due to the increasing unit of surface area...” However, the other factor to 

consider is that of release rate. The rate of silver ion release from conventional silver salts is greater 

than from a comparable amount of silver nanoparticles. This fact is inherent in the decision document 

statement that “...larger amounts of [conventional] silver [have] to be added to an article in order to 

provide sufficient lifetime of activity for antimicrobial treatment.” The slower rate of silver release from 

nanosilver particles means that a smaller amount of AGS-20 would be required to achieve the same 

level of antimicrobial activity over a comparable time period. Thus, it is the reduced amount of 

nanosilver, as compared to conventional silver salts, that would lead to a lower environmental silver 

exposure.

3. NACWA Comment: “NACWA believes EPA has insufficient information to declare that a particular 

nanosilver product has added value over other silver-based pesticides.”

Response: As a general matter, EPA does not consider the comparative value of antimicrobial pesticides. 

Rather, EPA evaluates antimicrobial products to determine if they will perform their intended function 

without causing unreasonable adverse effects on the environment. EPA does not generally consider the 

need for nonpublic health pesticides unless the risks from use of such pesticide are of concern and such 

risks may not be mitigated to acceptable levels. 

Because EPA is granting a conditional registration, EPA identified public interests in the potential to 

reduce environmental loading of silver and the availability of a more durable antimicrobial treatment as 

compared to the currently registered silver-salt based material preservatives. With this registration

there exists the potential for a decrease in the net amount of silver entering the environment as 

compared to the currently registered silver-salt based material preservatives. For example, Geranio et 

al. (2009, Environ. Sci. Technol., 43:8113) 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. We have reviewed the registered silver containing 

pesticides and found for commercially available products (Simoncic and Tomsic, 2010, Textile Research 

Journal, 80:1721) that the amount of silver allowed in textiles ranges from 0.03 to 40 mg/g. If the 

pending conditional registration for HeiQ were approved, it would restrict the amount AGS-20 to 

between 0.01 to 0.1 mg/g as silver, which is on the low end of the spectrum for registered silver 

containing products. 

4. NACWA Comment: EPA's primary reason for the conditional approval appears to be its concerns over 

market fairness and the fact that other competing products are already on the market. NACWA believes 

that EPA should instead focus its efforts on existing products and make sure there are sufficient data to 

determine their potential impacts.

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. Where EPA can make the 

requisite statutory findings, the result may be the creation of a level playing field between already 
December 1, 2011

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registered and new pesticides. The Agency plans to issue data call-ins for the existing nanosilver 

containing pesticides.

5. NACWA Comment: In terms of EPA's assessment of the potential for "unreasonable adverse effects", 

the environmental exposure for the conditional approval was calculated using the Down-the-Drain 

model and assumed a wastewater treatment removal efficiency of 88%. This removal rate was not 

based on the removal of nanosized materials and, therefore, such a high rate of removal cannot be 

assumed. The wastewater treatment process is typically far more effective at removing larger particles 

than smaller ones and so it is quite likely that there will be considerable pass through of small materials 

such as silver nanoparticles. The removal efficiency must be characterized based on nanosilver and not 

ionic silver.

Response: The down-the-drain assessment was revised to address the potential discharge of nanosilver

in wash water. Instead of using a single value for wastewater treatment removal efficiency, EPA 

considered a range of removal efficiencies for nanosilver from 85 to 99%, which were based on the work 

by Blaser et al. (2008, Sci. Total Environ. 390:396).

6. NACWA Comment: Based on the model output, EPA made the determination that the level of 

environmental exposure was unlikely to cause environmental harm. However, EPA recognizes that 

neither model considers the additive effect of other silver nanoparticles or silver containing products on 

the market. In addition, the Daphnia magna toxicity values which were used to evaluate the potential 

for in-stream toxicity were based on ionic silver. This is problematic as the FIFRA Scientific Advisory 

Panel stated: "... nanomaterials can deliver ions directly to specific tissues, cell membranes and inside 

cells - places where other forms of silver cannot reach. Therefore, the hazard profile of silver 

nanomaterials may differ from other forms of silver." This, coupled with the EPA statement that "... 

existing data seem to indicate that [nanosilver's] effects are different and/or more severe than for 

silver", does not corroborate EPA's expectation of "no unreasonable adverse effects" associated with 

approval for this product.

Response: In response to this comment the down-the-drain assessment was revised to address the 

potential discharge of nanosilver in wash water. Nanosilver toxicity to aquatic organisms including 

freshwater algae, flea, and fish were used to calculate risk quotients (RQs) that were compared to the 

Agency's Level of Concern (LOC) values for listed and non-listed aquatic species. The effect level for 

nanosilver 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. The RQs for Daphnia 

magna exposed to nanosilver ranged from 0.00005 to 0.016, which are not of concern for listed or nonlisted organisms because they were less than the LOC of 0.5 and 0.05, respectively.

7. NACWA Comment: From a wastewater treatment perspective, the conditional approval of another 

nanosilver product is discouraging. Wastewater utilities have been working diligently to reduce the input 

of silver into their wastestream in order to limit its presence in biosolids and wastewater effluent. 

Though strict pretreatment programs can limit the amount of silver entering the wastestream, 
December 1, 2011

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treatment plants do not have the authority or capability to regulate residential waste which is likely to 

be a large contributor of nanosilver materials.

Response: To date, AGS-20 is the only nanosilver containing product for which EPA made a registration 

decision involving nanosilver. Other products which claim to contain nanosilver are in the marketplace; 

however, these products are registered as containing elemental silver. As to the total volume of 

nanosilver that will enter the market place as a result of registering AGS-20, this value is unknown at this 

time. However, based on Agency confidential records, the total mass of silver distributed as material 

preservative in the United States during 2009 was less than 6,800 kg. The Agency estimated that 4,500 

kg/yr of HeiQ AGS-20 nanosilver could expected to be used in the unlikely event that every person in 

America was to purchase one t-shirt treated with AGS-20 every year. While this volume is not 

insignificant, it is small relative to the approximately 500,000 kg of silver that was released into the 

environment from other industry sectors during 2008 according to the EPA’s Toxic Release Inventory. 

8. NACWA Comment: In addition to the other data requirements, EPA must require any nanosilver 

pesticide product to be evaluated to assess its potential for nitrification inhibition at the wastewater 

treatment plant. In addition, it is not clear if a measure of removal efficiency during the wastewater 

treatment process is a component of the Tier 2 study requirements. Information on treatability is vital to 

characterizing environmental exposure in the Down-the-Drain model and must be a requirement of any

Tier 2 data collection efforts.

Response: There is the potential for silver nanoparticles 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. Once entrained in the biosolids, the silver nanoparticles 

could serve as a long term source of ionic silver which may 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. Although this result suggests that the silver in AGS-20 would not be expected to 

negatively impact wastewater treatment systems, it is unclear if the 26 day test period was sufficient 

time to evaluate this impact given that the rate of ionic silver released from AGS-20 is unknown. 

There are contradictory reports in the scientific literature regarding the impact of silver nanoparticles 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. 

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. These two research groups are 

reporting different findings with the Burkhardt group suggesting little impact of nanosilver to 
December 1, 2011

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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 silver nanoparticles 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) 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.

As a result of this information, with this registration there exists the potential for a decrease in the net 

amount of silver entering the environment as compared to the currently registered silver-salt based 

material preservatives.

9. NACWA Comment: In this case, there are no current data that can be used to support a conclusion of 

"no unreasonable adverse effects" for the unique properties of nanosilver. EPA should instead work, to 

the extent of its authority, to limit the use of the other nanosilver products that have been unknowingly 

registered until the necessary data are provided.

Response: The Agency respectfully disagrees. Using conservative assumptions which overestimate the 

dose of nanosilver that could potentially be derived from the AGS-20 nanosilver-silica composite along 

with maximum values for risk uncertainty factors, EPA was 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 manufactured treated with AGS-20. Thus, the Agency concluded 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 plans to issue data call-ins for the existing nanosilver containing pesticides.

Comment 36: Jamie Heisig-Mitchel, Hampton Roads Sanitation District (9/13/2010 EPA-HQ-OPP-2009-

1012-0054)

1. HRSD Comment: ...it is important to note that the manner in which this specific request for comment 

was disseminated greatly limited opportunity for public participation. This request for comment was not 

published in the federal register. At a minimum, EPA should have notified parties who had submitted 

comments on previous nanoparticle proposals of this comment request.

Response: The HeiQ Decision Document was not posted to the Federal Register because there was no 

statutory requirement to do so. However, to provide transparency in Agency decision making, the 

document was posed to the Pesticides Public Regulatory Docket to provide an opportunity for public 

comment. Postings to the public docket are sent via an automated email service, which can be accessed 

by going to http://www.epa.gov/oppfead1/cb/csb_page/form/form.html.
December 1, 2011

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2. HRSD Comment: EPA believes that the use of the HeiQ product should result in a lower potential

environmental exposure to silver as compared to conventional silver-based pesticides. However, given 

that the document also indicates that silver ionization is greater for nanoscale particles due to an 

increase in surface area, the supposition of a lower environmental silver exposure resulting from 

nanosilver products may be false. No studies have been provided comparing the environmental 

exposure resulting from conventional silver-based pesticides and nanosilver pesticides. There is no data 

to support the hypothesis that the overall environmental exposure is lower with nanoscale silver 

products.

Response: The decision document states that “As the size of silver particles decreases...the potential for 

releasing silver ions increases, due to the increasing unit of surface area...” However, the other factor to 

consider is that of release rate. The rate of silver ion release from conventional silver salts is greater 

than from a comparable amount of silver nanoparticles. This fact is inherent in the decision document 

statement that “...larger amounts of [conventional] silver [have] to be added to an article in order to 

provide sufficient lifetime of activity for antimicrobial treatment.” The slower rate of silver release from 

nanosilver particles means that a smaller amount of AGS-20 would be required to achieve the same 

level of antimicrobial activity over a comparable time period. Thus, it is the reduced amount of 

nanosilver, as compared to conventional silver salts, that would lead to a lower environmental silver 

exposure.

3. HRSD Comment: The consumer benefit highlighted is the prolonged antimicrobial activity of silver 

nanoparticles relative to other silver-based pesticides. ...there is no data representative of HeiQ AGS-20 

which supports a prolonged length of efficacy and no direct comparison with other conventional silverbased pesticides to indicate that this nanoparticle product has added value.

Response: HeiQ has recently submitted confidential testing results comparing AGS-20 treated fabric to 

fabric treated with other silver-based pesticides demonstrating AGS-20’s antimicrobial effectiveness at 

reduced silver loading.

4. HRSD Comment: ...the study provided by HeiQ which evaluated the leaching of AGS-20 in wash water 

was insufficient to assess the leachability of their product. Extrapolation of the results from leaching 

studies performed on other silver nanoparticle products is inappropriate as the size of the nanoparticle 

directly influences its properties. This was recognized in the FIFRA SAP report: “Particle size substantially 

impact particles properties, such as rate and concentration of silver ion release, reactivity...” 

Response: The study performed by Geranio et al. (2009, Environ. Sci. Technol., 43:8113) used textiles 

NP-PES-SURF and NP-PES which contained the HeiQ AGS-20 product. Thus, there was no extrapolation in 

results.

5. HRSD Comment: Rather than granting conditional approval to this new product and allowing 

currently registered products to remain on the market, EPA must remove all nanosilver pesticide 

products from the marketplace until data is provided for each product which indicates its use will not 

result in an unreasonable adverse impact on the environment.
December 1, 2011

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Response: The Agency will initiate cancellation action if it determines that dietary (food and drinking 

water) and/or non-dietary (occupational and ecological) risks of concern necessitate the cancellation of 

all currently registered uses of a pesticide, or such risks necessitate changes to the terms and conditions 

of registration that registrants have been unwilling to implement. The Agency plans to issue data call-ins 

for the existing nanosilver containing pesticides.

6. HRSD Comment: The environmental exposure was calculated using the Down-the-Drain model and 

assumed a wastewater treatment removal efficiency of 88%. This removal rate was not based on the 

removal of nanosized materials and, therefore, such a high rate of removal cannot be assumed.

Response: The down-the-drain assessment was revised to address the potential discharge of nanosilver 

in wash water. Instead of using a single value for wastewater treatment removal efficiency, EPA 

considered a range of nanosilver removal efficiencies from 85 to 99%, which were based on the work by 

Blaser et al. (2008, Sci. Total Environ. 390:396). 

7. HRSD Comment: Based on the model output, EPA made the determination that the level of 

environmental exposure was unlikely to cause environmental harm. However, EPA recognizes that 

neither model considers the additive effect of other silver nanoparticles or silver containing products on 

the market. 

Response: The maximum amount of ASG-20 is that can be used in textiles is limited to 0.01%. See terms 

and conditions on the registration as explained in the decision document. As to the total volume of 

nanosilver that will enter the market place as a result of registering AGS-20, this value is unknown at this 

time. However, based on Agency confidential records, the total mass of silver distributed as material 

preservative in the United States during 2009 was less than 6,800 kg. The Agency estimated that 4,500 

kg/yr of HeiQ AGS-20 nanosilver could expected to be used in the unlikely event that every person in 

America was to purchase one t-shirt treated with AGS-20 every year. While this volume is not 

insignificant, it is small relative to the approximately 500,000 kg of silver that was released into the 

environment from other industry sectors during 2008 according to the EPA’s Toxic Release Inventory.

8. HRSD Comment: ...the Daphnia magna toxicity values which were used to evaluate the potential for 

in-stream toxicity, were based on ionic silver.

Response: The down-the-drain assessment was revised to address the potential discharge of nanosilver 

in wash water. Nanosilver toxicity to aquatic organisms including freshwater algae, flea, and fish were 

used to calculate risk quotients (RQs) that were compared to the Agency's Level of Concern (LOC) values 

for listed and non-listed aquatic species. The effect level for nanosilver 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. 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.
December 1, 2011

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9. HRSD Comment: POTWs do not have the authority or capability to regulate residential waste which is 

likely to be a large contributor of nanosilver materials.

Response: With this registration there exists the potential for a decrease in the net amount of silver 

entering the environment as compared to the currently registered silver-salt based material 

preservatives. For example, Geranio et al. (2009, Environ. Sci. Technol., 43:8113) 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. We have 

reviewed the registered silver containing pesticides and found for commercially available products 

(Simoncic and Tomsic, 2010, Textile Research Journal, 80:1721) that the amount of silver allowed in 

textiles ranges from 0.03 to 40 mg/g. If the pending conditional registration for HeiQ were approved, it 

would restrict the amount AGS-20 to between 0.01 to 0.1 mg/g as silver, which is on the low end of the 

spectrum for registered silver containing products. 

10. HRSD Comment: In addition, the work by Choi and Hu (2008) and Choi et al. (2008), which indicates 

that silver nanoparticles can have an increased inhibitory effect on the bacterial community vital to the

wastewater nutrient removal process, is deeply concerning. With strict nutrient limitations imposed by 

National Pollutant Discharge Elimination System (NPDES) permits, there is little tolerance for even minor 

upsets to the microbial community present within the wastewater treatment plants. In addition to the 

other data requirements, the EPA must require HeiQ to conduct a nitrification inhibition evaluation on 

its product to assess its potential for nitrification inhibition at wastewater treatment plants. In addition, 

it is not clear if a measure of removal efficacy during the wastewater treatment process is a component 

of the Tier 2 study requirements. Information on treatability is vital to characterizing environmental 

exposure in the Down-the-Drain model and must be a requirement of Tier 2 data collection efforts.

Response: There is the potential for silver nanoparticles 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. Once entrained in the biosolids, the silver nanoparticles 

could serve as a long term source of ionic silver which may 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. Although this result suggests that the silver in AGS-20 would not be expected to 

negatively impact wastewater treatment systems, it is unclear if the 26 day test period was sufficient 

time to evaluate this impact given that the rate of ionic silver released from AGS-20 is unknown. 

There are contradictory reports in the scientific literature regarding the impact of silver nanoparticles 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. 
December 1, 2011

Page 26 of 55

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. 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 silver nanoparticles 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 test results provided by HeiQ 

and the small volume of nanosilver (i.e., < 4,500 kg/yr) 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.

11. HRSD Comment: Of the 19 Tier 1 studies EPA has indicated it will require from HeiQ to complete its 

assessment of human and environmental risk, HeiQ has not completed a single one. This is not a

scenario in which conditional approval is being granted pending the approval of a few additional studies. 

In this case, there is no data that can be used to support a conclusion of “no unreasonable adverse 

effects”. There is no data available that warrants conditional approval of this product.

Response: 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. 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.

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

Comment 39: Ben Horenstein, Tri-TAC (9/13/2010 EPA-HQ-OPP-2009-1012-0057)

1. TriTAC Comment: If silver pesticide product use becomes common, wastewater silver discharges 

could reach levels not seen in the last two decades—and could have adverse impacts on our wastewater 

treatment process as well as on the quality of our effluent and biosolids.
December 1, 2011

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Response: The use of AGS-20 could lead to reductions in the overall use of silver in textiles. For example, 

Geranio et al. (2009, Environ. Sci. Technol., 43:8113) 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. We have reviewed the registered silver 

containing pesticides and found for commercially available products (Simoncic and Tomsic, 2010, Textile 

Research Journal, 80:1721) that the amount of silver allowed in textiles ranges from 0.03 to 40 mg/g. If 

the pending conditional registration for HeiQ were approved, it would restrict the amount AGS-20 to 

between 0.01 to 0.1 mg/g as silver, which is on the low end of the spectrum for registered silver 

containing products. 

As to the volume of nanosilver that will enter the market place as a result of registering AGS-20, this 

value is unknown at this time. However, based on Agency confidential records, the total mass of silver 

distributed as material preservative in the United States during 2009 was less than 6,800 kg. The Agency 

estimated that 4,500 kg/yr of HeiQ AGS-20 nanosilver could expected to be used in the unlikely event 

that every person in America was to purchase one t-shirt treated with AGS-20 every year. While this 

volume is not insignificant, it is small relative to the approximately 500,000 kg of silver that was released 

into the environment during 2008 according to the EPA’s Toxic Release Inventory.

2. TriTAC Comment: POTWs are subject to National Pollutant Discharge Elimination System (NPDES) 

permits under the Clean Water Act. These permits include toxicity limits and may also include

quantitative effluent limitations for silver. Exceeding these limitations has serious consequences, 

including monetary fines and penalties and the risk of citizen lawsuits. Under California law, our 

members are liable for daily Mandatory Minimum Penalties should violations of their discharge permits 

occur.

Response: Based on Agency confidential records, the total mass of silver distributed as material 

preservative in the United States during 2009 was less than 6,800 kg. Assuming that HeiQ has a 

production volume of 4,500 kg/yr yields a total yearly volume of 11,300 kg/yr (4,500 + 6,800 = 11,300) 

or approximately 31 kg/day (11,300 kg/yr ÷ 365 days/yr = 31 kg/day) for all silver preservatives. Given 

that the Benchmark for silver in discharge water is 0.0318 mg/L and the approximate treatment capacity 

of the Bay Area POTWs is 300 million gallons per day, this means that the silver Benchmark is 36 kg/day 

for Bay Area POTWs. Since not all silver preservatives are used in the Bay Area, the approximately usage 

is 0.72 kg/day after adjusting for the Bay Area population (e.g., 7 million people). This is 50 times less 

than the amount of silver that would potentially lead to an NPDES violation. This analysis assumes that 

100% of the silver is released from these products and that 100% of this silver passes through the Bay 

Area POTWs. Thus, the mass of silver used as material preservatives is not anticipated to lead to 

violations of NPDES permits in the Bay Area.

Supporting Calculations

6,800 kg silver (2009 Agency data) + 4,500 kg silver (HeiQ AGS-20) = 11,300 kg/yr silver (total)

11,300 kg/yr silver (total) × yr/365 day = 31 kg silver/day (total)
December 1, 2011

Page 28 of 55

7 million people (Bay Area Population) / 300 million people (U.S. Population) = 0.0233 (population 

adjustment factor for Bay area)

31 kg silver/day (total) × 0.0233 (population adjustment factor for Bay area) = 0.72 kg silver/day 

(Bay area)

0.0318 mg silver/L (current bench mark value) × 300,000,000 gal (estimated combined 

wastewater outflow for Bay area) × 3.7854 L/gal = 3.6 x 107 mg/day 

3.6 x 107mg/day = 36 kg/day (bench mark value for Bay Area POTWs)

36 kg silver/day (bench mark value for Bay Area POTWs) /0.72 kg silver/day (Bay area) = 50 times

3. TriTAC Comment: ...Benn and Westerhoff (2008) found that for certain products, silver losses during 

washing were so large that most of the silver in these products would be washed into the municipal 

wastewater system during the products’ lifetimes. Where small particles occur in products, the entire 

particle could be washed down the drain. 

Response: Benn and Westerhoff (2008) tested products that are commercially available and are 

currently registered as material preservatives. The more recent work by Geranio et al. (2009, Environ. 

Sci. Technol., 43:8113) used textiles NP-PES-SURF and NP-PES containing the HeiQ AGS-20 product and 

showed significantly lower silver release rates during washing of the HeiQ AGS-20 treated product as 

compared to the currently registered silver materials preservatives.

4. TriTAC Comment: Nanosilver particle may have extraordinary effects on POTW treatment processes. 

In two related studies, Choi and Hu (2008) and Choi et al. (2008) found that silver particles less than 5 

nanometers in diameter are uniquely toxic to nitrifying bacteria, which are critical to biological nutrient 

removal at POTWs.

Response: There is the potential for silver nanoparticles 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. Once entrained in the biosolids, the silver nanoparticles 

could serve as a long term source of ionic silver which may 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. Although this result suggests that the silver in AGS-20 would not be expected to 

negatively impact wastewater treatment systems, it is unclear if the 26 day test period was sufficient 

time to evaluate this impact given that the rate of ionic silver released from AGS-20 is unknown. 

There are contradictory reports in the scientific literature regarding the impact of silver nanoparticles 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. 
December 1, 2011

Page 29 of 55

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. 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 silver nanoparticles 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) 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. TriTAC Comment: POTWs tend to be most efficient at removing larger particles from wastewater. 

Tiny particles and zeolites may have different potential to pass through POTWs than other forms of 

silver.

Response: While the Agency does not yet have removal efficiency rates for nanoscale materials, in the 

work by Kiser et al. (2009) they reported 70 to 85% removal efficiency for engineered TiO2 nanoparticles 

at 8 US wastewater treatment plants with most of the TiO2 mass detected in the settled biosolids. 

Similar removal efficiencies and associations to sludge were reported for CeO nanoparticles (Limbach et 

al., 2008). The down-the-drain assessment was revised to address the potential discharge of nanosilver 

in wash water. Instead of using a single value for wastewater treatment removal efficiency, EPA 

considered a range of removal efficiencies from 85 to 99%, which were based on the work by Blaser et 

al. (2008, Sci. Total Environ. 390:396). Recent work by Kaegi et al. (2011, Environ. Sci. Technol., 45:3902) 

reported removal efficiencies of 70% for nanosilver shock loadings of 2.4 g/L to a pilot scale wastewater 

treatment system and 97% for loadings of less than 0.13 g/L. Based on this work, the Agency anticipates 

that nanoscale materials will be readily removed during wastewater treatment. 

6. TriTAC Comment: While POTWs have the authority to regulate industrial and commercial sources of 

silver and other toxic pollutants, we have little or no control over the discharge of pollutants from the 

thousands of households we serve. Silver is a toxic metal that cannot degrade in the environment and is 

registered for use as a pesticide in numerous products. To allow the unrestricted usage of products that 

intentionally release silver into the environment would be an irresponsible neglect of the principles of 

environmental sustainability that should strongly influence U.S. EPA’s decisions.

Response: While silver cannot degrade, it can and is readily transformed into stable mineral forms that 

are not harmful. Recent work by Kim et al. (2010) reported finding nanosized silver-sulfide particulates 

in the sewage sludge samples collected as part of the Targeted National Sewage Sludge Survey (TNSSS). 

These silver nanoparticles, which may have originated from nanosilver or silver ions, were in the mineral 

form consisted of acanthite (Ag2S). This hypothesis is supported in the recent work by Kaegi et al. (2011, 

Environ. Sci. Technol., 45:3902) who reported the near complete transformation of nanosilver into the 

silver-sulfide mineral after introducing nanosilver at concentrations between 2.4 and 0.13 g/L into a 
December 1, 2011

Page 30 of 55

pilot scale wastewater treatment system. Acanthite (Ag2S) is a relatively insoluble mineral and was 

found to exhibit lower toxicity to organisms than silver ions or silver nanoparticles (Choi et al., 2009, 

Water Research, 43:1879).

Trade Association

Comment 37: Harold T. Michels, Copper Development Association (9/13/2010 EPA-HQ-OPP-2009-1012-

0055)

1. CDA Comment: Concerns of equity and fairness demand that instead of allowing silver-based 

antimicrobial products, including HeiQ AGS- 20, to be marketed with implied public health claims under 

the guise of the “treated article” exemption, that EPA insist that the efficacy of silver-based products be 

supported by meaningful, real world, GLP efficacy data.

Response: The EPA approved pesticide label for HeiQ AGS-20 does not contain public health claims.

2. CDA Comment: CDA remains concerned that this and similar silver-based “additives” are not 

marketed in a manner consistent with the clear requirements for “non-public health” “treated article” 

products.

Response: The Agency will take these comments into consideration during enforcement actions.

3. CDA Comment: [The label is] ambiguous and potentially misleading to consumers as it allows 

unqualified bacterial growth suppression claims without the requisite caveat that it only protects 

against bacteria that may cause odors, discoloration or deterioration.

Response: The EPA approved pesticide label for HeiQ AGS-20 does not contain unqualified bacterial 

growth suppression claims.

4. CDA Comment: CDA objects to the conclusion in the Proposed Decision Document that “consumers 

purchasing textile treated with nanosilver should receive a durable antimicrobial protection.” No such 

consumer benefit is demonstrated by the data provided for HeiQ AGS-20, as the testing does not 

demonstrate efficacy under real world conditions.

Response: HeiQ has submitted subsequent confidential test results demonstrating the durability of the 

AGS-20 treated textiles in comparison to other commercially available nanosilver treated textiles.

States

Comment 30: Lynda Knobeloch, Wisconsin DHS (9/1/2010 EPA-HQ-OPP-2009-1012-0048)

We are writing to request that the deadline for submission of comments be extended by at least 30 

days. This request is being made because of the number of documents that need to be reviewed and the 

amount of staff time needed to complete our review and prepare comments.
December 1, 2011

Page 31 of 55

Response: The public comment period was from August 12, 2010 through September 13, 2010. There 

was no statutory requirement for public comment on the Decision Document. However, to provide 

transparency in Agency decision making, the document was posed to the Pesticides Public Regulatory 

Docket to provide an opportunity for public comment. Postings to the public docket are sent via an 

automated email service, which can be accessed by going to 

http://www.epa.gov/oppfead1/cb/csb_page/form/form.html.

Comment 40: Marylou Verder-Carlos, California Department of Pesticide Regulation (9/13/2010 EPAHQ-OPP-2009-1012-0058)

1. CalDPR Comment: Insufficient toxicology data are available with which to make a scientifically 

informed evaluation of potential toxicity issues associated with nanosilver. Nanosilver has a distinctly 

different hazard profile when compared to more traditional forms of silver. The Proposed Decision 

Document points out numerous ways in which the toxicity could be underestimated based on available 

data.

Response: The Agency presented results from two toxicity studies performed with nanoscale silver. One 

was a 28-day rat feeding study using 60 nm diameter nanosilver (Kim et al., Inhal. Toxicol., 2008, 

10:575), which reported liver toxicity as well as effects on blood and systemic distribution of silver in rat 

tissues. The second study was a 90-day rat inhalation study completed with 18 to 19 nm diameter 

nanosilver (Sung et al., Toxicol. Sci., 2009, 108:452), which found toxic effects in the liver and lungs. 

There are two more recent studies which will be incorporated into the final Decision Document. One is a 

90-day rat feeding study that used 56 nm diameter nanosilver (Kim et al., Part. Fibre Toxicol. 2010, 7:20) 

and the other is a 28-day mouse feeding study that used 42 nm diameter nanosilver (Park et al., Environ.

Tox. Pharm., 2010, 30:162). 

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. 

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.

2. Cal DPR Comment: The proposed use of the product, HeiQ AGS-20, raises significant concerns for 

human exposure. The screening level assessment provides information and notes the potential problem 

with occupational inhalation of HeiQ AGS-20 during formulation and application processes. However, it 

does not address potential inhalation or dermal exposure to consumers who will be in direct contact 

with the nanosilver particles for prolonged periods of time through the daily wearing and use of treated 

textiles. Additionally, infant and toddler exposures may result from extended exposure to pillowcases, 
December 1, 2011

Page 32 of 55

bedding, and clothing. Washing may dislodge particles, making them available for inhalation and 

possibly dermal absorption. 

Response: The Decision Document contains an evaluation of the risk to children from dermal and 

incidental oral exposures to textiles treated with HeiQ AGS-20. Results from these studies were used to 

calculate the dose that a 3 year old toddler might receive while wearing and chewing on textiles treated 

with AGS-20. One conclusion of this process was that a child wearing an AGS-20 treated t-shirt would be 

exposed to nanosilver at a level that was, at a minimum, 1,000 times lower than the no observed 

adverse effects dosage. 

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. The final Decision Document contains an estimate of the dose of 

nanosilver that a consumer might receive when drying AGS-20 treated textiles. This estimate supports 

the expectation of lower exposure from laundry drying when compared to dermal and oral contact to 

AGS-20 treated textiles. EPA is requiring HeiQ to perform an attrition study to confirm the assessment of

exposure to nanosilver during laundry drying of AGS-20 treated textiles.

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, 

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 color-fast 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 for 

textiles treated with AGS-20.

3. CalDPR Comment: Very little is known about the environmental fate and ecotoxicology of nanosilver 

in the environment. 
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Response: The rate at which silver nanoparticles transform into ionic silver determines the length of 

time that these particles will reside in the environment. Although there are studies reporting that silver 

nanoparticles 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, silver nanoparticles 

are 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, Wat. Res. 43:1879) provided spectroscopic evidence showing 

that silver nanoparticles react with sulfide to produce stable silver-sulfide complexes, which were shown 

by Liu et al. (2010, Environ. Sci. Technol. 44:2169) and Levard et al. (2011, Environ. Sci. Technol. 45:5260) 

to have undetectable rates of nanosilver to ionic silver transformation. These stabilized silver 

nanoparticle 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, silver 

nanoparticles are anticipated to partition to biosolids during wastewater treatment but may also be 

released in the effluent. Thus, there is the potential for silver nanoparticles to reside or persist in the 

environment for a significant period of time where these particles are most likely to be associated with 

sediments. 

The down-the-drain assessment was revised to address the potential discharge of nanosilver in wash 

water. Nanosilver toxicity to aquatic organisms including freshwater algae, flea, and fish were used to 

calculate risk quotients (RQs) that were compared to the Agency's Level of Concern (LOC) values for 

listed and non-listed aquatic species. The effect level for nanosilver 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. 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.

4. CalDPR Comment: The pharmacokinetics or pharmacodynamics of nanosilver is unknown at this time. 

Response: The Agency agrees that the pharmacokinetic and pharmacodynamic properties of nanosilver 

are largely uncharacterized at present, and that these properties can provide important information 

about toxicity. Guideline metabolism and pharmacokinetic studies are conditionally required in tiered 

testing strategies for pesticides and the Agency asks for them only if it is anticipated that they will 

provide additional information that is necessary for understanding the toxicity of the test material. The 

Agency is requiring toxicity studies that are relevant to both the routes and durations of exposure for 

the use patterns of nanosilver products. Thus, it is anticipated that these studies will be sufficient for 

identifying and characterizing hazard in the absence of absorption, distribution, metabolism, and 

excretion (ADME) data. 

It is also important to note that ADME studies of nanosilver are likely to be technically complex since 

both the particle and ion content of tissues would have to be determined. This situation is exemplified 

by two recent studies that were used in the Agency's screening-level risk assessment. Rodent studies in 
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which silver nanoparticles were administered by the oral route (Kim et al., Inhal. Toxicol., 2008, 10:575-

583) or by inhalation (Sung et al., Toxicol. Sci., 2009, 108:452-461) show dose-dependent increases in 

silver content in diverse tissues (testes, liver, kidney, lungs, brain, stomach) and differences between 

male and female silver content via the oral route, with up to 3-fold more silver in female kidney tissue 

(Kim et al 2008). The silver in these tissues was detected by flame analysis, meaning there was no 

distinction between nanoscale silver and silver ions. Thus, these studies suggest that silver can localize 

to diverse sites in the body following exposure to nanosilver by different routes, and that there may be 

gender differences in organ levels. Although these results share some commonalities with those of other 

nanomaterials (e.g. ultrafine particulate matter, quantum dots) which have shown uptake by the 

reticuloendothelial system and translocation to the brain following exposure by different routes (i.e.

inhalation), there is still some uncertainty as to the form of silver in the tissues (nanoparticle or ion or 

both). One way of determining nanosilver content would involve counting silver nanoparticles in 

multiple tissue sections of diverse organs using electron microscopy, which is labor intensive and only 

assesses small subsamples of tissues. However, in spite of the uncertainty in ADME, both of these 

studies yielded toxicological effects that provided endpoints for quantitative risk assessment in the 

screening-level risk assessment conducted by the Agency.

5. CalDPR Comment: Nanosilver and nanometals may pose unique exposure profiles when compared to 

traditional silver/metals. 

Response: HeiQ AGS-20 is intended for use on textiles which are also treated using conventional silver. 

So the exposure profiles for textiles preserved with conventional and nanoscale silver appear to be 

similar.

6. CalDPR Comment: The physico-chemical behavior among various size groups of nanoparticles is 

unknown, with the smallest particle size generally considered to be the most reactive. Additionally, 

nanoparticles have been shown to aggregate to form larger intermediate forms (e.g., colloids, 

agglomerates, composites) with potentially unique properties. 

Response: HeiQ submitted test results for AGS-20 that included physical-chemical behavior such as 

water solubility, melting point, and density. While EPA does not have complete knowledge of all the 

behaviors of AGS-20, there is sufficient information available for making an informed scientific 

evaluation regarding the conditional registration of HeiQ AGS-20.

7. CalDPR Comment: Existing fate/transport models for metals (e.g., Down-the Drain Model, Biotic 

Lingand Model) were developed to address bulk, not nano-scale forms of metals. 

Response: The down-the-drain model is a basic mass discharge calculation (i.e., production volume/river 

flow) and assumes complete solubility of nanosilver, similar to the modeling approach used by Mueller

and Nowack (2008, Environ. Sci. Technol. 42:4447). In the revised Decision Document, the biotic ligand 

model (BLM) was repaced by route-specific nanosilver toxicity studies completed with aqautic species.
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8. CalDPR Comment: It is not known whether the proposed enforcement analytical method will suitably 

quantify the amount of the nanosilver active ingredient in the product, particularly when the product is 

a “nano-silver-silica composite.” 

Response: There remains a significant effort to develop protocols and analytical methods for the Tier 1 

Required Data. EPA would welcome CalDPR assistance with reviewing the analytical approaches that will 

be prepared by HeiQ as part of the conditional registration we are granting.

9. CalDPR Comment: The proposed product label indicates that the active ingredient in the product is 

silver metal (AG)* (19.3%). The label does not clearly indicate that the silver in the product is nanosilver. 

Underneath the active ingredient statement the label reads, “*size range < 1 μm” or 1,000 nanometers. 

Assuming an umbrella classification of 1-100 nanometers to be nanotechnology, the silver in the product 

would need to be less than 0.1 μm.

Response: The proposed label has been revised to read: includes particles in the size range between 1 to 

100 nm.

Industry

Comment 1: Abigail Trueblood, The Dow Chemical Company (4-27-10, EPA-HQ-OPP-2009-1012-0002.1)

Silver is not a new active ingredient, and it is unclear why EPA has chosen to identify this submission as 

containing a new active. If the submission in question contains a different form of silver other than 

those currently recognized by the Agency as active ingredients, this should have been made clear in this 

Notice. At the very least, the Notice as written generates confusion among current registrants of the 

active ingredient silver.

Dow hopes to see the Agency address this issue publically with an explanation of why the silver 

contained in the submission identified in EPA-HQ-OPP-2009-1012 is regarded as a new active ingredient.

Response: Silver is not a new active ingredient; however, EPA could not conclude that the nanoscale 

material in AGS-20 was an active ingredient in any currently registered pesticide.

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 
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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 active ingredient (Federal Register, Vol. 75, No. 61, Page 16110). 

Comment 2: Marie Paquette, BASF The Chemical Company (4-27-10, EPA-HQ-OPP-2009-1012-0003.1)

On March 31, 2010, EPA published a notice of receipt of applications for registration of pesticide 

products containing new active ingredients (75 FR 16109). In particular, the notice identified an 

application under File Number 85249-R, with silver identified as the new active ingredient, for uses as 

“antimicrobial and preservative additive used to treat fibers, plastics, polymers, latex products and 

ceramics.”

Silver is not a new active ingredient. Silver has been an active ingredient in pesticide products since the

1970’s. Silver was addressed during re-registration (RED issued 1992) and is being addressed through

registration review. The former Ciba Corporation, which is now BASF Corporation, is a registrant of

several pesticide products containing silver that are approved for the same uses.

Therefore, it is unclear as to why the Agency would list silver as a new active ingredient under this 

notice. If there is something that makes this a new active ingredient, the Agency must clearly identify 

what it is and why it is different, so that appropriate opportunity for public comment is provided in 

accordance with FIFRA § 3(c)(4) and 40 CFR § 152.102. Without providing that additional information 

and opportunity for comment, the Agency will have failed to meet its statutory obligations as well as its 

obligations under its regulations.

It is of concern to BASF Corporation that there is a change in the Agency’s determination of when silver 

is or is not a new active ingredient. We are requesting that the Agency extend the public comment 

period for this notice of receipt and provide a clear and specific explanation of why this silver is a new 

active ingredient so that there is appropriate opportunity for input on the basis for the Agency’s 

determination.

Response: Silver is not a new active ingredient; however, EPA could not conclude that the nanoscale 

material in AGS-20 was an active ingredient in any currently registered pesticide.

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 
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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 active ingredient (Federal Register, Vol. 75, No. 61, Page 16110). 

Comment 41: James G. Votow WilmerHale for HeiQ Matierals AG (9/13/2010 EPA-HQ-OPP-2009-1012-

0059)

This comment was in support of the registration of AGS-20 and no EPA response was necessary.

NGOs

Comment 26: Jaydee Hanson, ICTA (8/23/2010 EPA-HQ-OPP-2009-1012-0044)

The International Center for Technology Assessment (ICTA) would like to thank the agency for circulating

its memorandum announcing the posting of documents to Docket Number EPA-HQ-OPP-2009-1012 and

opening a public comment period regarding its proposed conditional registration of "HeiQ AGS-20". ICTA

intends on fully participating in the comment process and welcomes this and any other opportunities to

communicate with the agency on this topic.

We write at this time to respectfully request a 30-day extension of the September 11, 2010 deadline for

public comment to October 10, 2010. As the agency and FIFRA Scientific Advisory Panel have both

recognized, this is an important issue and as such the agency should gather as much information as 

possible about its next steps from all interested parties. We recognize that the agency chooses to act 

promptly on the matter, however between now and September 11th is a very problematic time for 

many interested parties due to legislative recess, seasonal transitions of staff, and vacation/holiday 

schedules. In light of these circumstances we are concerned that the current deadline will not be 

sufficient for some parties to provide comment. The proposed registration and broader nanosilver issue 

present many complicated legal and scientific issues and meaningful public input will require a 
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substantial amount of time and effort. The requested extension is necessary to provide interested 

parties an appropriate opportunity to develop meaningful comments on the agency’s proposed action.

Response: The public comment period was from August 12, 2010 through September 13, 2010. There 

was no statutory requirement for public comment on the Decision Document. However, to provide 

transparency in Agency decision making, the document was posed to the Pesticides Public Regulatory 

Docket to provide an opportunity for public comment. Postings to the public docket are sent via an 

automated email service, which can be accessed by going to 

http://www.epa.gov/oppfead1/cb/csb_page/form/form.html.

Comment 31: Dr. Maria Powell, NanoCEO (9/7/2010 EPA-HQ-OPP-2009-1012-0049)

Firstly, I would like to thank the agency for circulating a memorandum announcing the posting of 

documents to Docket Number EPA-HQ-OPP-2009-1012 and opening a public comment period regarding 

the proposed conditional registration of HeiQ AGS-20. 

However, I (and my organization's members) find the extremely short period of time provided for public 

comment problematic. Moreover, this is a very difficult time for many people--many of whom take 

vacations in August or are busy with other summer-to-fall transitions. It is also a hard time for other 

interested parties such as university and government scientists and policymakers, due to legislative 

recess, seasonal transitions of staff, and vacation/holiday schedules. 

The registration of a nanosilver product is an extremely important issue for public and environmental 

health, and as you know involves complex scientific, economic, political, and ethical issues. It is 

absolutely critical that enough time be provided for all the stakeholders--citizens, scientists, 

policymakers, etc--to read and review the information provided on the docket, discuss this information, 

and provide comments and questions to the docket that can be considered by the agency in deciding 

whether to grant conditional approval to this product. 

Citizens and other stakeholders have relevant information to bring to this discussion, and will also bear 

any public health and environmental consequences of silver released from products treated with HeiQ 

nanosilver materials. Not allowing them adequate time to review the issues and comment, is not a truly 

democratic decision-making process. 

We hope the agency will support democracy and citizen engagement in science and policymaking 

regarding nanosilver and other risk issues. Please extend the comment period for another 30 days, to 

October 10, 2010. 

Response: The public comment period was from August 12, 2010 through September 13, 2010. There 

was no statutory requirement for public comment on the Decision Document. However, to provide

transparency in Agency decision making, the document was posed to the Pesticides Public Regulatory 

Docket to provide an opportunity for public comment. Postings to the public docket are sent via an 
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automated email service, which can be accessed by going to 

http://www.epa.gov/oppfead1/cb/csb_page/form/form.html.

Comment 32: M. Griffin (9/7/2010 EPA-HQ-OPP-2009-1012-0050)

We are very much interested in submitting comments. As this is a cross agency topic we respectully 

request that an extension be granted to the deadline for these comments.

Thank you

Response: The public comment period was from August 12, 2010 through September 13, 2010. There 

was no statutory requirement for public comment on the Decision Document. However, to provide 

transparency in Agency decision making, the document was posed to the Pesticides Public Regulatory 

Docket to provide an opportunity for public comment. Postings to the public docket are sent via an 

automated email service, which can be accessed by going to 

http://www.epa.gov/oppfead1/cb/csb_page/form/form.html.

Comment 33: Wenonah Hauter, Food and Water Watch (9/8/2010 EPA-HQ-OPP-2009-1012-0051)

Food & Water Watch would like to thank the agency for circulating its memorandum announcing the 

posting of documents to Docket Number EPA-HQ-OPP-2009-1012 and opening a public comment period 

regarding its proposed conditional registration of “HeiQ AGS-20.”

Food & Water Watch intends on fully participating in the comment process. However, between now and 

September 11th is a very problematic time for many interested parties due to legislative recess 

vacation/holiday schedules, and demands created by pressing food safety issues like the massive recall 

of eggs due to salmonella contamination. In light of these circumstances we are concerned that the 

current deadline will not be sufficient for some parties to provide comment. Therefore, we write at this 

time to respectfully request a 30-day extension of the September 11, 2010 deadline for public comment.

Response: The public comment period was from August 12, 2010 through September 13, 2010. There 

was no statutory requirement for public comment on the Decision Document. However, to provide 

transparency in Agency decision making, the document was posed to the Pesticides Public Regulatory 

Docket to provide an opportunity for public comment. Postings to the public docket are sent via an 

automated email service, which can be accessed by going to 

http://www.epa.gov/oppfead1/cb/csb_page/form/form.html.

Comment 34: Caroline Cox, Center for Environmental Health (9/13/2010 EPA-HQ-OPP-2009-1012-0052)

The following new research demonstrates an important public health hazard relevant to the use of 

nanosilver antimicrobials:

Laura K. Braydich-Stolle, et al. Silver Nanoparticles Disrupt GDNF/Fyn kinase Signaling in Spermatogonial 

Stem Cells TOXICOLOGICAL SCIENCES 116(2), 577–589 (2010).
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In view of the significant health issues, registration of nanosilver products at this time is inconsistent 

with EPA's mandate to protect human and environmental health.

Response: The Agency has reviewed the cited study and concluded that it does show that nanosilvers of 

different sizes and coatings can get inside of virally transformed cells when added directly to the cells in 

vitro, resulting in reduced cell viability. This study suggests the potential for an effect of nanosilvers on 

male fertility, but did not address whether or not nanosilvers actually reach the testis when

administered to test animals via different routes of exposure or if the ability of such males to reproduce 

is adversely affected. 

The Agency has reviewed the literature and is aware of only two studies in which the ability of silver 

from nanosilver to reach the testis was measured. The Agency cited these in the screening-level risk 

assessment. These are a 90-day study via the inhalation route (Sung et. al., Toxicol. Sci., 2009, 108(2): 

452) and a 28 day study via the oral route (Kim et al., Inhal. Toxicol., 2008, 20:575). Silver was found only 

in the testis of animals to which nanosilver was administered via the oral route. The only anticipated 

oral exposures to HeiQ's product are incidental oral exposures (from children sucking on treated fabric). 

Since these oral behaviors are generally restricted to very young children, the Agency does not consider 

the oral route to be a likely route of exposure for persons of reproductive age. However, the Agency is 

still requiring HeiQ to conduct an in vivo guideline 870.3650 combined repeated dose toxicity study via 

the oral route that includes reproductive and developmental endpoints. This study will include detailed 

histopathological examination of the male gonads to assess spermatogenesis, as well as assessment of 

reproductive function and effects in offspring.

Comment 38: Jo Anne Shatkin, CLF Ventures (9/13/2010 EPA-HQ-OPP-2009-1012-0056)

1. CLF Comment: An additional occupational exposure scenario that OPP should evaluate includes

professional laundering and dry cleaning of treated fabrics. Nanosilver particles may be released to 

water, solvents or air during commercial laundering, with potential occupational dermal and inhalation 

exposures to treated fabrics.

Response: 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. The final Decision Document contains an estimate of 

the dose of nanosilver that a consumer might receive when drying AGS-20 treated textiles. This estimate 

supports the expectation of lower exposure from laundry drying when compared to dermal and oral 

contact to AGS-20 treated textiles. EPA is requiring HeiQ to perform an attrition study to confirm the 

assessment of exposure to nanosilver during laundry drying of AGS-20 treated textiles.
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2. CLF Comment: ...recently published another study (Kim et al. 2010) with different nanosilver material, 

lasting 90 days instead of 28, and in a different species of rat. This additional study (which is not 

referenced by EPA) also determined a similar No Observable Adverse Effect Level of 30 mg/kg to the one 

used as the basis for the POD.

Response: The work by Kim et al. (Part. Fibre Toxicol. 2010, 7:20) and the repeated-dose toxicity and 

inflammatory responses in mice by oral administration of silver nanoparticles by Park et al. (Environ. 

Toxicol. Phar. 2010, 30:162) were made available after the Decision Document was prepared. The 

Agency incorporated the findings of these studies into the final version of the Decision Document.

3. CLF Comment: If, based on well designed and validated protocols that consider a breadth of water 

quality types and conditions, those additional exposure studies suggest low exposure and hence do not 

warrant detailed evaluation of toxicity for this product...

Response: The Agency agrees that unnecessary animal testing is to be avoided and have proposed that 

further testing only be conducted if textiles treated with HeiQ AGS-20 are found to release nanoscale 

silver particles.

4. CLF Comment: ...OPP should require labeling of fabrics containing nanosilver.

Response: Consumers will be informed where there are marketing claims provided by product 

advertising.

Comment 42: Olga V. Naidenko, Environmental Working Group (9/13/10 EPA-HQ-OPP-2009-1012-0060)

1. EWG Comment: EPA puts public health at unnecessary risk by approving nanomaterials for use in 

consumer products in the absence of the basic health and safety data the agency requires for 

antimicrobials (EPA 2010b).

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

registration under FIFRA section 3(c)(7)(A). This application contained the required data regarding AGS20 product identity and composition, physical and chemical properties, and health effects. HeiQ 

submitted short-term acute animal toxicity testing data for AGS-20 as detailed in the Decision 

Document. These data demonstrated that AGS-20 did not cause abnormalities or mortalities in test 

animals after administration by oral, dermal, and inhalation routes, was moderately to non-irritating in 

skin and eye testing, and was not a skin sensitizer based on dermal testing. Furthermore, HeiQ 

submitted five studies covering the amount of silver released from and the efficacy of AGS-20 treated 

textiles, the occupational exposures to AGS-20, and potential impacts to wastewater treatment. Thus, 

the base-line safety testing of AGS-20 was performed. 

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. 

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 
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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.

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

derived from the AGS-20 nanosilver-silica composite along with maximum values for risk uncertainty 

factors, EPA was 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 manufactured treated with 

AGS-20. Thus, the Agency concluded that use of AGS-20 will not cause unreasonable adverse effects on 

the environment during the period when newly required data are being developed.

2. EWG Comment: Risks to human health and the environment will be defined by cumulative exposures 

to HeiQ AGS-20 and other nanosilver-containing consumer products already on the market. Ignoring 

cumulative exposures, as EPA proposed with the AGS-20 conditional approval, could jeopardize human 

health.

Response: The Project on Emerging Nanotechnologies (PEN) has compiled an inventory of all consumer 

products reported by their manufacturers to contain nanomaterials. Based on the information PEN has 

compiled, nanosilver is the most common nanoscale material currently used in consumer products. 

Approximately a quarter of the identified consumer nanomaterial products are claimed to contain 

nanosilver. Nanosilver products are sold in the U.S. and in foreign markets such as Asia, Europe, 

Australia, and South America. As discussed in the Market Equity section, four registered antimicrobial 

products have recently been identified by the registrants as containing nanosilver. In addition, FDA has 

allowed the sale of bandages treated with nanosilver to control post-operative infections in surgical 

wounds and the sale of catheters and other devices, which may come in contact with human tissues, 

treated with nanosilver to control the growth of microorganisms. While EPA does not have data to 

quantify relative exposure to nanosilver from these products vs. HeiQ’s product, given the number of 

other uses for silver in the market, EPA thinks it is reasonable to expect that nanosilver exposure 

resulting from the multiple consumer products and FDA uses is likely to be considerably higher than the

consumer exposure that would result from wearing textile products treated with AGS-20. 

3. EWG Comment: Nanosilver pesticide registrants, including the HeiQ Company and past registrants of 

similar approved products, should addresses outstanding data gaps on the potential toxicity of these 

materials. Until these gaps are filled, EPA cannot ensure that nanoparticles antimicrobials are safe for 

widespread use in consumer products.

Response: The Agency respectfully disagrees. Using conservative assumptions which overestimate the 

dose of nanosilver that could potentially be derived from the AGS-20 nanosilver-silica composite along 

with maximum values for risk uncertainty factors, EPA was able to determine that for the period of 

conditional registration, there is a low probability of adverse risk to children and the environment from 
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textiles manufactured treated with AGS-20. Thus, the Agency concluded 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 plans to issue data call-ins for the existing nanosilver containing 

pesticides. 

Comment 43: Jennifer Sass, NRDC (9/13/10 EPA-HQ-OPP-2009-1012-0061)

1. NRDC Comment: The registrant has had sufficient time to generate and submit required data 

Response: 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 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.

2. NRDC Comment: ...AGS-20 may cause “unreasonable adverse effects on the environment” The special 

considerations of the impact of these exposures on children and infants must be incorporated into 

EPA‟s assessment of these unique materials. Because EPA has failed to consider or evaluate these 

exposures, the Agency may not make the required safety finding under FIFRA. When considering lifestage related sensitivities to nanoparticle toxicity, the elderly also represent a vulnerable subpopulation.

Response: EPA calculated conservative estimates for the risk to children and workers potentially 

exposed to AGS-20 based on toxicity data available for similar nanosilver compounds available in the 

scientific literature. One conclusion of this process was that a child wearing an AGS-20 treated t-shirt 

would be exposed to nanosilver at a level that was, at a minimum, 1,000 times lower than the no 

observed adverse effects dosage. Thus, the Agency did consider and evaluate exposures to children as 

part of its finding that AGS-20. Although these 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. 

3. NRDC Comment: Use of the pesticide is not in the public’s interest. ...EPA has not explained why 

consumers need antimicrobial textiles. 

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand.
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With this registration there exists the potential for a decrease in the net amount of silver entering the 

environment as compared to the currently registered silver-salt based material preservatives. For 

example, Geranio et al. (2009, Environ. Sci. Technol., 43:8113) 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. We have reviewed the 

registered silver containing pesticides and found for commercially available products (Simoncic and 

Tomsic, 2010, Textile Research Journal, 80:1721) that the amount of silver allowed in textiles ranges 

from 0.03 to 40 mg/g. If the pending conditional registration for HeiQ were approved, it would restrict 

the amount AGS-20 to between 0.01 to 0.1 mg/g as silver, which is on the low end of the spectrum for 

registered silver containing products. HeiQ has recently submitted confidential testing results comparing 

AGS-20 treated fabric to fabric treated with other silver-based pesticides demonstrating AGS-20’s 

antimicrobial effectiveness at reduced silver loading.

4. NRDC Comment: Compared with silver, nanosilver releases more ions and is therefore more toxic, 

more biologically active, more deadly to microbes, and more persistent in the environment.

Response: The decision document states that “As the size of silver particles decreases...the potential for 

releasing silver ions increases, due to the increasing unit of surface area...” However, the other factor to 

consider is that of release rate. The rate of silver ion release from conventional silver salts is greater 

than from a comparable amount of silver nanoparticles. This fact is inherent in the decision document 

statement that “...larger amounts of [conventional] silver [have] to be added to an article in order to 

provide sufficient lifetime of activity for antimicrobial treatment.” The slower rate of silver release from 

nanosilver particles means that a smaller amount of AGS-20 would be required to achieve the same 

level of antimicrobial activity over a comparable time period. Thus, it is the reduced amount of 

nanosilver, as compared to conventional silver salts, that would lead to a lower environmental silver 

exposure.

5. NRDC Comment: EPA bemoans the high costs of regulatory requirements, including new data 

generation, on the registrants and even frets that these regulatory costs may “discourage technology 

providers from pursuing the development of beneficial new applications of nanotechnology in the field 

of pesticides.” (Decision Doc at 30). This argument is presented without any supporting data, or even 

“guesstimates” of the actual costs and benefits of this “innovative” technology.

Response: The Agency stated that “...meeting regulatory requirements can add costs and delay the 

marketing of new products” in the proposed Decision Document. This statement was removed from the 

final Decision Document. No economic analysis has been performed to quantify these costs and delays.

6. NRDC Comment: In addition, EPA does not appear to have a reliable tracking system to identify when 

required data for a conditional registration are still missing, identify and sort data that has been 

received, review the data and record the Agency staff conclusions, and incorporate the incoming data 

into the chemical assessment and product registrations in a timely and appropriate manner that reflects 

any hazards identified in the data.
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Response: The pesticide program does not currently have an information technology system designed 

for tracking or managing conditional registration actions. In the absence of such a system, the program 

has utilized the Office of Pesticide Programs Information Network (OPPIN) to provide some minimal 

reporting capacity. OPPIN has some limited codes allowing identification of regulatory actions as 

conditional registrations. OPP is in the process of sunsetting and replacing the OPPIN data system. As 

the new IT system is designed, the upgrades will include tools to improve the identification, tracking, 

reporting and program management of conditional registrations.

7. NRDC Comment: EPA has overused conditional registrations, as they now represent the majority of 

active registrations. The EPA Office of Pesticide Programs (OPP) has over 16,000 pesticide product active 

registrations (that is, currently registered). Of these, over 11,000 (68%) are conditionally registered.

Response: The OPP program has used the term ‘conditional registration’ to cover both actions intended 

by Section 3(c)(7) of FIFRA, and other activities outside that section of the statute. While the latter 

activities, such as requiring label changes, are legitimate program actions, OPP has been imprecise in its 

use of the term “conditional registration.” It is likely that most of the of the registration decisions 

described in OPPIN as conditional registrations may not, in fact, have been registration actions taken 

under 3(c)(7). In the future, OPP needs to be more careful to eliminate potential confusion with the 

actions that meet the Section 3(c)(7) conditional registration criteria. 

Over the past decades, OPPIN identifies approximately 1,400 registration actions which meet the FIFRA 

Section 3(c)(7)(B) and (C) criteria. This is less than 2% of the approximately 90,000 registration decisions 

in OPPIN. This indicates that, as statutorily intended, this authority for conditional registrations for 

registering new uses or new ingredients has been used in relatively narrow circumstances. Our analysis 

indicates that for the overwhelming majority of these conditional registrations the conditions of the 

registration have been satisfied in a timely fashion (See 

http://www.epa.gov/pesticides/regulating/conditional-registration.html). OPP’s review of the data 

submitted for these conditional registrations has not justified a change in either the initial risk 

assessments or the risk management label conditions. Therefore, our use of conditional registrations has 

not resulted in greater risk to human health or the environment. This validates the quality of the safety 

finding that preceded the issuance of the conditional registrations.

Comment 44: Maria Powell, Nanotechnology Citizen Engagement Organization (9/13/10 EPA-HQ-OPP2009-1012-0062)

1. NanoCEO Comment: We want to note that the public comment period on this docket was much too 

short for the members of our organization to review documents adequately and write comments, 

especially at this time of the year when many people are on vacation. Not providing adequate time for 

public to comment on critical environmental and public health decisions is not supportive of citizen 

engagement or democratic decision making.

Response: There was no statutory requirement to provide a public comment period for the HeiQ 

Decision Document. However, to provide transparency in Agency decision making, the document was 
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posed to the Pesticides Public Regulatory Docket to provide an opportunity for public comment. 

Postings to the public docket are sent via an automated email service, which can be accessed by going to 

http://www.epa.gov/oppfead1/cb/csb_page/form/form.html.

2. NanoCEO Comment: ...once emitted from all these products, it will continue to circulate in the 

environment, releasing silver ions over time under different conditions and environmental contexts, and 

bioaccumulate in organisms, including humans, over time. 

Response: The rate at which silver nanoparticles transform into ionic silver determines the length of 

time that these particles will reside in the environment. Although there are studies reporting that silver 

nanoparticles 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, silver nanoparticles 

are 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 silver 

nanoparticles react 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 silver nanoparticle 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, silver nanoparticles are anticipated to partition to biosolids during wastewater 

treatment but may also be released in the effluent. Thus, there is the potential for silver nanoparticles 

to reside or persist in the environment for a significant period of time where these particles are most 

likely to be associated with sediments. 

To verify the expectation that the silver in AGS-20 will form stable complexes under environmental 

conditions, EPA is requiring HeiQ to conduct a dissolution kinetics study to measure the rate and form of 

silver released from AGS-20 in simulated natural water.

3. NanoCEO Comment: There is insufficient evidence supporting the widespread assumption that silver 

is “innocuous” to humans, and considerable evidence refuting it. Numerous experimental studies 

suggest that silver can affect mammalian cells in many of the same ways it affects non-mammalians at a 

range of doses—binding, interacting, and interfering with DNA, proteins and enzymes, altering 

membrane ion transport and membrane integrity, causing oxidative stress and cytotoxicity, significant 

immune responses, and more.

Response: The no observable adverse affects level (NOAEL) of 30 mg/kg/day used in the Proposed 

Decision Document, which was revised to 0.5 mg/kg/day in the Final Decision Document, was based on 

enzyme and liver abnormalities. In no way does the Agency support the notion that silver is “innocuous” 

to humans. 

4. NanoCEO Comment: Most puzzlingly, regulatory standards to this day are primarily based on a small 

number of very old and limited studies—in particular, Gaul and Staud (1935) and Hill and Pillsbury 

(1939). We find it highly troubling that these two reports, one of which was an extremely limited study 
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on syphilis patients, continue to be the basis for health standards on silver currently, especially in light of 

the increasing uses of silver and nanosilver ubiquitously in commerce and the highly sophisticated 

methodologies and technologies that are currently available to scientists and risk assessors to study 

silver/nanosilver’s risks to humans. NanoCEO Comment: Regardless, we know that nano-sized forms of 

silver are more potent than larger forms of silver in releasing silver ions because of their higher surfaceto-volume ratio; indeed, this is why they are promoted and marketed as more potent antimicrobials. 

The proposed decision document for the registration of HeiQ AGS-20 states this clearly (p.3, p. 29).

Response: These studies were not used in evaluating the nanosilver found in AGS-20. Instead, recent 

work using contemporary toxicity techniques that evaluated a range of effects were used in determining 

the nanosilver dose that is thought not to cause any effects. The studies used to evaluate the toxicity of 

nanosilver involved dosing animals with nanosilver particles and evaluating a wide range of effects on 

the animals in the Proposed Decision Document. The Agency presented results from two toxicity studies 

performed with nanoscale silver. One was a 28-day rat feeding study using 60 nm diameter nanosilver 

(Kim et al., Inhal. Toxicol., 2008, 10:575), which reported liver toxicity as well as effects on blood and 

systemic distribution of silver in rat tissues. The second study was a 90-day rat inhalation study 

completed with 18 to 19 nm diameter nanosilver particles (Sung et al., Toxicol. Sci., 2009, 108:452), 

which found toxic effects in the liver and lungs. There are two more recent studies that were

incorporated into the Final Decision Document. One involved 90-day rat feeding study using 60 nm 

diameter nanosilver (Kim et al., Particle and Fibre Toxicology 2010, 7:20) and the other is a 28-day 

mouse feeding study (Park et al., Environ. Tox. and Pharm., 2010, 30:162). 

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. 

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.

5. NanoCEO Comment: On a more practical level, the fact that nanosilver materials can be more readily 

incorporated into a wide variety of materials and products than larger forms of silver—and therefore are 

being incorporated into an incredibly wide range of consumer products and industrial materials—will 

undoubtedly result in increasing levels of silver being released from these materials and emitted into 

homes, workplaces, and air, water, soil, waste, etc. Many forms of silver (nano and not-nano) will end 

up in wastewater, sewage plant effluents, and sewage sludge, which is then often spread on agricultural 

land and food crops. This will clearly increase human and environmental exposures well beyond 

previous uses of silver.
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Response: EPA has already registered a number of silver-based antimicrobial products for use as 

materials preservatives in textiles. 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 require larger amounts of silver to be added to textiles in 

order to provide a sufficient lifetime of activity for antimicrobial treatment. Therefore, 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. As a result of this information, with this registration there 

exists the potential for a decrease in the net amount of silver entering the environment as compared to 

the currently registered silver-salt based material preservatives.

6. NanoCEO Comment: The EPA claims that one of the rationales for giving the HeiQ silver product 

conditional approval is its benefits to the public. What benefits is the EPA referring to? We have not 

seen any study showing that coating textiles with nanosilver reduces the rate of human illnesses. To the 

contrary, by disrupting healthy microbial balances on and in the human body, and by increasing 

microbial resistance, these widespread uses of nanosilver are more likely to increase than decrease 

human illnesses. Using silver/nanosilver ubiquitously and building microbial resistance to silver will 

make it impossible to use silver in serious burn and wound situations where it may be necessary to 

prevent and/or treat serious infections. We are very surprised that the EPA has apparently accepted the 

misleading marketing claims of companies promoting unnecessary uses of a potent antimicrobial for 

non-life threatening, primarily aesthetic uses.

Response: With this registration there exists the potential for a decrease in the net amount of silver 

entering the environment as compared to the currently registered silver-salt based material 

preservatives. For example, Geranio et al. (2009, Environ. Sci. Technol., 43:8113) 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. We have 

reviewed the registered silver containing pesticides and found for commercially available products 

(Simoncic and Tomsic, 2010, Textile Research Journal, 80:1721) that the amount of silver allowed in 

textiles ranges from 0.03 to 40 mg/g. If the pending conditional registration for HeiQ were approved, it 

would restrict the amount AGS-20 to between 0.01 to 0.1 mg/g as silver, which is on the low end of the 

spectrum for registered silver containing products. HeiQ has recently submitted confidential testing 

results comparing AGS-20 treated fabric to fabric treated with other silver-based pesticides 

demonstrating AGS-20’s antimicrobial effectiveness at reduced silver loading.

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

increasing use of silver, such as silver nanoparticles 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 
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of wound dressings that release sublethal levels of silver over a long period of time allowing bacterial to 

develop resistance.

In terms of environmental impact, a recent study involved releasing 1 mg/L of silver nanoparticles 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 silver nanoparticles.

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

nanoparticles 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.

7. NanoCEO Comment: After outlining several key ways throughout the supporting and decision 

documents in which the HeiQ product could cause adverse effects to workers and to other vulnerable 

populations (children, elderly, etc), the EPA nevertheless goes on to conclude that the product will not 

cause unreasonable adverse effects. Is this to imply that that these vulnerable, more at-risk populations 

don’t matter? Or that it is “reasonable” to take the chance of harming them?

Response: These more at-risk populations do matter, which is why the Agency evaluated the impact to 

children. The outcome of this evaluation is that it is unlikely that children will receive a dose of 

nanosilver by wearing or chewing on clothing treated with AGS-20 which would cause adverse effects.

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. 

8. NanoCEO Comment: If there is no monitoring, how will the EPA actually know whether or not there 

are adverse effects in four years?

Response: The Agency is requesting that additional product specific testing be performed to verify the 

literature studies used in the screening-level risk assessment (see Appendix A of the Decision 

Document). If at any time during testing of AGS-20 the Agency receives information indicating there is a 

significant difference between the toxicity of AGS-20 and the literature studies, then the Agency will 

take action to remove AGS-20 from the marketplace.
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9. NanoCEO Comment: As citizens we depend on our government agencies to protect us from harmful 

toxins in the environment and in commerce. Clearly, in this case, the EPA is more interested in 

protecting and benefiting the corporate interests involved with silver/nanosilver, not in protecting 

and/or benefiting the public and the environment. We are saddened and disheartened by this as citizens 

in a purported democracy.

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. Using conservative 

assumptions which overestimate the dose of nanosilver that could potentially be derived from the AGS20 nanosilver-silica composite along with maximum values for risk uncertainty factors, EPA was 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 manufactured treated with AGS-20. Thus, the Agency 

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

the period when newly required data are being developed.

10. NanoCEO Comment: The HeiQ nanosilver product should be fully tested for human and 

environmental safety before it goes on the market.

Response: The Agency respectfully disagrees. Using conservative assumptions which overestimate the 

dose of nanosilver that could potentially be derived from the AGS-20 nanosilver-silica composite along 

with maximum values for risk uncertainty factors, EPA was 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 manufactured treated with AGS-20. Thus, the Agency concluded that use of AGS-20 will not 

cause unreasonable adverse effects on the environment during the period when newly required data 

are being developed.

Comment 45: Dr Gemma Buckland, Humane Society International (9/13/10 EPA-HQ-OPP-2009-1012-

0063)

1. HSI Comment. The implication of such changes is not fully understood, so risk assessment cannot rely 

on existing toxicity data for the bulk material. The UK Royal Society and Royal Academy of Engineering 

have stated that nanomaterials should be treated as new chemicals from a risk point of view.

Response: The studies on bulk silver were not used in evaluating the nanosilver found in AGS-20. 

Instead, recent work using contemporary toxicity techniques that evaluated a range of effects were used 

in determining the nanosilver dose that is thought not to cause any effects. The studies used to evaluate 

the toxicity of nanosilver involved dosing animals with nanosilver particles and evaluating a wide range 

of effects on the animals in the Proposed Decision Document. The Agency presented results from two 

toxicity studies performed with nanoscale silver. One was a 28-day rat feeding study using 60 nm 

diameter nanosilver (Kim et al., Inhal. Toxicol., 2008, 10:575), which reported liver toxicity as well as 

effects on blood and systemic distribution of silver in rat tissues. The second study was a 90-day rat 

inhalation study completed with 18 to 19 nm diameter nanosilver particles (Sung et al., Toxicol. Sci., 

2009, 108:452), which found toxic effects in the liver and lungs. There are two more recent studies that 
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were incorporated into the Final Decision Document. One involved 90-day rat feeding study using 60 nm 

diameter nanosilver (Kim et al., Particle and Fibre Toxicology 2010, 7:20) and the other is a 28-day 

mouse feeding study (Park et al., Environ. Tox. and Pharm., 2010, 30:162). 

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. 

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.

2. HSI Comment. Existing in vivo toxicity test methods display inherent uncertainties surrounding their 

use1

Response: In addition to using standard whole animal toxicity tests, the Agency is requesting an in vitro 

micronucleus (MN) assay. Thus, the Agency is using cell-based assays to evaluate the toxicity of AGS-20.

. These include the difficulties of extrapolating test data between species, genders and breeds of 

animals including humans (due to anatomical, physiological, biochemical, metabolic and 

pharmacological differences). With a new field such as nanomaterials, the full range of potential 

toxicities is not known. Using standard animal toxicity tests, which are little more than “black box” 

methods, would risk overlooking novel unwanted effects. Human cell-based assays, in contrast, would 

allow the study and elucidation of a range of molecular and cellular mechanisms of toxicity. For 

example, human cell culture assays can be used to monitor the oxidative stress responses of cells 

exposed to nanoparticles.

3. HSI Comment. It is therefore not appropriate to release products that still require information 

regarding their safety. Indeed, the FIFRA SAP report itself (EPA, 2010) noted that the “hazard profile of 

nanosilver may differ from other forms of silver” and it is “especially challenging to determine that there 

is no release of nanomaterials from a substrate under the current state of science and available 

measurement standards”.

Response: While the Agency does not have sub-chronic toxicity testing for products that contain 

nanoscale silver, there are results in the scientific literature for the toxicology of nanosilver. The studies 

used to evaluate the toxicity of nanosilver involved dosing animals with nanosilver particles and 

evaluating a wide range of effects on the animals in the Proposed Decision Document. The Agency 

presented results from two toxicity studies performed with nanoscale silver. One was a 28-day rat 

feeding study using 60 nm diameter nanosilver (Kim et al., Inhal. Toxicol., 2008, 10:575), which reported 

liver toxicity as well as effects on blood and systemic distribution of silver in rat tissues. The second 

study was a 90-day rat inhalation study completed with 18 to 19 nm diameter nanosilver particles (Sung 

 1 Langley G (2004). Chemical Safety and Animal Testing: A Regulatory Smokescreen? 35 pp. London: BUAV.
December 1, 2011

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et al., Toxicol. Sci., 2009, 108:452), which found toxic effects in the liver and lungs. There are two more 

recent studies that were incorporated into the Final Decision Document. One involved 90-day rat 

feeding study using 60 nm diameter nanosilver (Kim et al., Particle and Fibre Toxicology 2010, 7:20) and 

the other is a 28-day mouse feeding study (Park et al., Environ. Tox. and Pharm., 2010, 30:162). 

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. 

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.

4. HSI Comment. EPA-HQ-OPP-2009-1012-0005. ...we also noted a number of methodological variations 

in the protocols used for the standard toxicology tests, such as use of a carrier other than water without 

explanation, and a failure to monitor body weight changes of treated animals.

Response: As stated in the Acute Toxicity Review the use of PEG300, a polyethylene glycol often used in 

medical settings, instead of water was deemed acceptable since PEG300 has low toxicity. Also, body 

weights of test animals were recorded; however, body weight changes were not calculated. These 

studies were reviewed by EPA and deemed acceptable even though there were minor deviations in 

experimental protocol.

5. HSI Comment. EPA-HQ-OPP-2009-1012-0010. The studies performed do not confirm whether 

nanoparticles dissociate from the textiles due to the insufficient magnification used in the study.

Response: The work by Geranio et al. (2009, Environ. Sci. Technol., 43:8113) was used to estimate the 

release of nanosilver from textiles. The Agency assumed that all silver released in the study was in the 

form nanosilver. For the risk assessment, the Agency evaluated the case where up to 35% of the 

nanosilver in the textile treated with AGS-20 would be transferred to the skin of child or to a child during 

chewing of the textile. 

6. HSI Comment. EPA-HQ-2009-1012-0008. The researchers do not explore the release of embedded 

silver particles and omit exploration of the environmental fate of nanosilver particles. 

Response: The work cited in this document was not used by the Agency in evaluating the proposed 

registration of HeiQ AGS-20.

7. HSI Comment. EPA-HQ-2009-1012-0012. There appears to be occupational inhalation exposure, yet 

the study is not clear on the routes of exposure or on the endpoints useful for assessment. Omitting 
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these data does not provide a full picture as to the life-cycle of the product and overlooks potential 

areas of risk.

Response: Based on this work, the Agency is requiring that engineering controls be used when mixing, 

loading, and applying AGS-20 powder along with requiring personnel to use personal protective 

equipment.

8. HSI Comment. EPA-HQ-2009-1012-1015. The efficiency of the nanosilver socks displays limitations 

considering that 50% of the nanosilver is reported to leach out as AgCl during the first wash. Not only 

does this raise issues on product description and efficacy but this also highlights environmental fate 

concerns. Regardless of the toxicity level of AgCl, releasing an increased amount into the environment

may have consequences which have not been addressed in this study. 

Response: The study by Impelliteri et al. (J. Environ. Qual., 2009, 38:1528) was not performed on AGS-20 

treated textiles and was only presented as a study which informed the understanding that nanosilver, 

after exposure to oxidizing agents, could exist as insoluble silver chloride in the environment.

9. HSI Comment. EPA-HQ-2009-1012-0011 highlights that nanosilver is more toxic to nitrifying bacteria 

than regular silver ions; thus, if nanosilver particles are released at any stage from the product, the 

ensuing effects should be researched.

Response: There is the potential for silver nanoparticles 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. Once entrained in the biosolids, the silver nanoparticles 

could serve as a long term source of ionic silver which may 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. Although this result suggests that the silver in AGS-20 would not be expected to 

negatively impact wastewater treatment systems, it is unclear if the 26 day test period was sufficient 

time to evaluate this impact given that the rate of ionic silver released from AGS-20 is unknown. 

There are contradictory reports in the scientific literature regarding the impact of silver nanoparticles 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. 

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. 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.
December 1, 2011

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While there are reports suggesting the potential for silver nanoparticles 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) 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.

10. HSI Comment. EPA-HQ-2009-1012-0020. Registration of HeiQ AGS-20 is apparently “within the 

public interest”; however, the urgency of the need for this product remains to be seen when there are 

clear safety ambiguities and data gaps. It is important to treat all nanosilver products equally; the fact 

that some nano-products are already on the market and have not submitted data to the same degree as 

the HeiQ AGS-20 suppliers identifies registration errors and not an automatic licence for HeiQ AGS-20 

registration. A level playing field needs to be created for nano-products –– one that ensures safety to 

consumers and the environment. 

Response: EPA evaluates antimicrobial products to determine if they will perform their intended 

function without causing unreasonable adverse effects on the environment. EPA does not generally 

consider the need for nonpublic health pesticides unless the risks from use of such pesticide are of 

concern and such risks may not be mitigated to acceptable levels. Where the risks are not of concern, 

generally the need for the nonpublic health pesticide is determined by consumer demand. The Agency 

plans to issue data call-ins for the existing nanosilver containing pesticides.

11. HSI Comment. Nanomaterials in consumer products should also be viewed on a case-by-case basis 

due to the differences in properties that nanomaterials can display when differences in handling, 

preparation, use in mixtures etc exist for the same nanomaterial. Evidence already exists suggesting 

current regulatory testing approaches are not scientifically robust regarding the safety testing of 

nanomaterials and it is therefore germane that nano-specific approaches are in place before testing can 

be implemented. The overall production levels of nanomaterials and market volume should also be 

taken into consideration and not just the specific level of nanomaterial in a product.

Response: 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.
December 1, 2011

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12. HSI Comment. For such a new and potentially exciting field there are also concerns and dangers of 

the technology developing faster than the science. Therefore, the issues of transparency regarding 

information on testing methods and procedures have particular pertinence for public perception and 

understanding. It is essential for transparency to exist in order for full stakeholder understanding and 

ultimately consumer and environmental safety. 

Response: The Agency is committed to transparency during the decision making and testing process to 

the extent that information is not claimed to be business confidential. An example of this commitment 

to transparency was posting the HeiQ Decision Document to the Pesticides Public Regulatory Docket for 

public comment for which there was no statutory requirement to do so. Postings to the public docket 

are sent via an automated email service, which can be accessed by going to 

http://www.epa.gov/oppfead1/cb/csb_page/form/form.html.

13. HSI Comment. Currently employed animal test methods are not suitable for nanomaterial testing 

and represent a scientifically inappropriate testing approach. HSI and its sister organizations would like 

to urge the EPA to ensure efforts are channeled into creating a toxicity testing strategy akin to the 

National Research Council’s “Toxicity Testing in the 21st Century: A Vision and Strategy”2

Response: The Agency is working to advance the 21st Century toxicity testing approaches as described 

in the NRC document. For example, in addition to using standard whole animal toxicity tests, the Agency 

is requesting an in vitro micronucleus (MN) assay. A larger scale effort is being undertaken through 

EPA’s ToxCastTM program where in vitro methods are being developed and validated for the screening of 

nanoscale materials. Thus, the Agency is using cell-based assays, which are part of 21st Century toxicity 

testing, and developing new in vitro methods to evaluate the toxicity of nanoscale materials.

, relying on 

high-throughput, advanced techniques with direct human and environmental relevance.

 2 National Research Council (2007). Toxicity Testing in the 21st Century: A Vision and a Strategy, 146pp. 

Washington, DC: National Academy Press.