Comment Letter
September 7, 2012 Wanda Henson Office of Pesticide Programs (OPP) U.S. Environmental Protection Agency (EPA) 1200 Pennsylvania Ave., NW. Washington, DC 20460–0001 Subject:
Nanosilver Registration Review, Case # 5042 (Docket ID Number EPA–HQ–OPP– 2011-0370)
Dear Ms. Henson: On behalf of the Bay Area Clean Water Agencies (BACWA), we thank you for the opportunity to comment on the registration review for nanosilver. BACWA’s members include fifty-five publicly-owned wastewater treatment facilities and collection system agencies serving 6.5 million San Francisco Bay Area residents. We take our responsibilities for safeguarding receiving waters seriously and are very concerned about discharges of pesticides into wastewater systems that may compromise receiving water quality, effluent quality, biosolids reuse, and compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. BACWA’s Interest in Nanosilver Registration Review BACWA and our colleagues in the wastewater sector have been actively engaged in issues related to silver and nanosilver for many years. For your review, we have enclosed several letters to EPA detailing our concerns about silver and nanosilver pesticides and a report from a wellrespected San Francisco Bay Area scientist, Dr. Samuel Luoma, that explores risks of nanosilver in the context of the history of silver water pollution in the San Francisco Bay Area. 1 BACWA is specifically interested in this registration review for nanosilver because we believe all the use patterns noted in the Environmental Summary (“Nanosilver: Summary of Environmental Fate and Ecotoxicity Data for Registration Review,” pp. 2-3) may result discharges of nanosilver to wastewater treatment plants. While little is known about the fate and effects of nanosilver, we do know that silver is highly toxic to aquatic life at low concentrations, is persistent, and can bioaccumulate in some aquatic organisms, such as clams. Wastewater agencies have noted with some alarm that new product lines containing nanosilver
1
BACWA (2009). Comment Letter on Nanosilver Petition. Tri-TAC (2009). Comment Letter on Silver Registration Review. Tri-TAC (2011). Comment Letter on Nanomaterials Policy. Luoma, S. N. (2008). Silver Nanotechnologies and the Environment: Old Problems or New Challenges? Woodrow Wilson International Center for Scholars, Project on Emerging Nanotechnologies. Publication PEN 15.
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are quickly expanding, as detailed in EPA’s recently released case study on nanosilver. 2 Use of nanosilver products could substantially increase the total quantity of silver discharged to wastewater facilities, potentially increasing environmental concentrations and therefore environmental risks. Ignoring these risks could be extremely costly for the environment and the wastewater community. Below we have outlined questions, concerns and requests we have regarding nanosilver and the nanosilver registration review process. Address Data Gaps Before Registration The EPA nanomaterials case study on nanosilver disinfectants reveals numerous outstanding scientific questions related to the environmental fate, risks and toxicity of nanosilver. 3 In fact, EPA states that, “Efforts thus far to assess nanomaterial impacts on environmental and human health demonstrate that data gaps…currently impede carrying out assessments and generally restrict evaluations to limited aspects of specific nanomaterials” (p.7-26). BACWA believes these questions and many other issues should be resolved before EPA allows nanosilver products to be used. We concur with our colleagues at Tri-TAC, who, in a recent letter to EPA, 4 requested that EPA answer the following questions, which may be appropriately addressed through registration review data requirements. • • • • • •
•
What quantities of nanomaterials and metallic ions are now being used as antimicrobial agents in commercial products, both those registered and not registered by EPA? What percentage of metallic nanomaterials will be converted to the ionic form prior to and during the wastewater treatment process? What fraction of nanomaterials and metallic ions will end up in the treated wastewater and what fraction will end up in the biosolids? What is the anticipated removal efficiency of nanomaterials in wastewater treatment plants? What quantities and concentrations of nanomaterials and metallic ions will be released to wastewater treatment plants and the natural environment from the cumulative total of these products being marketed and registered? What affect does nanosilver have on biological wastewater treatment processes such as those used in municipal wastewater treatment plants? To what extent could nanosilver reduce treatment effectiveness, increasing releases of other pollutants into surface waters? If it is shown that nanomaterials partition to biosolids, what impacts will that impart on the beneficial use of biosolids?
2
EPA Office of Research and Development (2012). Nanomaterial Case Study: Nanoscale Silver in Disinfectant Spray. 3 Ibid. 4 Tri-Tac (2010). Comment Letter on Draft Nanomaterials Case Study on Silver (Docket ID Number EPA-HQORD-2010-0658).
2
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In addition, BACWA also asks that EPA address the following questions. •
•
•
How do nanoparticle characteristics, particularly surface coatings, affect the environmental fate and toxicity of nanoparticles? Recent studies show that both particle size and surface coating affect the environmental fate, toxicity, and bioavailability of nanosilver. 5,6 Are nanoparticles able to deliver silver ions to new environmental locations, perhaps within organisms that take them up? For example, filter-feeding organisms have been shown to be more sensitive to nanosilver, 7 maybe because they are ingesting and accumulating the particles. What is the potential for nanosilver to accumulate in aquatic and terrestrial food chains? Recent research indicates that gold nanoparticles biomagnify in a terrestrial food chain. 8
Develop Robust Analysis Plan and Conceptual Model In the recent past, EPA has made progress in its assessment plans so that they better evaluate uses resulting in discharges to wastewater treatment facilities; however, the nanosilver registration review docket does not provide the level of detail often included in most OPP environmental risk assessment work plans. For example, the docket primarily focuses on HeiQ formulations, and does not address risks, data gaps or data requirements pertaining to other registered uses beyond fabric treatments; it also does not include critical elements such as problem formulations, risk hypotheses, conceptual models and analysis plans. BACWA encourages EPA to develop a more robust and informative assessment plan for nanosilver that is consistent with other pesticide registration review dockets. For a strong example of an environmental risk assessment work plan, the Antimicrobials Division may look to the Environmental Fate & Effects Division’s (EFED’s) Registration Review Problem Formulation for Bifenthrin (Docket ID Number EPA–HQ–OPP–2010–0384). To illustrate the need for more in-depth risk assessment work planning, we have enclosed a side-by-side comparison of the nanosilver registration review environmental work plan document versus the bifenthrin registration review environmental work plan document. 9 Evaluate All Use Patterns for Environmental Exposures While we appreciate the Antimicrobial Division’s recognition in the Environmental Summary that nanosilver in treated fabrics may be discharged to wastewater treatment plants (p. 7), 5
Judy, J.D., et al. (2012). Bioavailability of Gold Nanomaterials to Plants: Importance of Particle Size and Surface Coating. Environmental Science and Technology, 46 (15): 8467–8474. 6 Huynh, K.A. and K.L. Chen (2011). Aggregation Kinetics of Citrate and Polyvinylpyrrolidone Coated Silver Nanoparticles in Monovalent and Divalent Electrolyte Solutions. Environmental Science and Technology, 45 (13): 5564–5571. 7 Griffitt, R.J., et al. (2008). Effects of Particle Composition and Species on Toxicity of Metallic Nanomaterials in Aquatic Organisms. Environmental Toxicology and Chemistry, 27 (9): 1972–1978. 8 Judy, J.D., et al. (2011). Evidence for Biomagnification of Gold. Environmental Science and Technology, 45 (2): 776–781. 9 Comparison of Nanosilver and Bifenthrin Registration Review Environmental Risk Documents.
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BACWA requests that EPA evaluate all use patterns (pp. 2-3) for potential environmental exposures. To illustrate how current uses may result in exposures in the aquatic and terrestrial environments, we have enclosed a conceptual model 10 that incorporates uses presented in the Environmental Summary, and a table 11 describing how specific product use patterns can cause environmental exposures. Below, we provide our concerns about use patterns more generally. Fabric Treatments. EPA states that further environmental fate studies may be required of the HeiQ registrant if studies show that nanosilver is released from fabric treatments. There is already evidence that fabrics treated with nanosilver release nanosilver as they are washed. 12 EPA also states that nanosilver fabric treatments will not likely impact wastewater treatment operations due to the current low volume of use (Environmental Summary, p. 7). However, once registered, sales of nanosilver-treated clothing may grow without any further regulatory action or evaluation by EPA; therefore, greater volumes of nanosilver may be released to wastewater treatment facilities, posing increasing environmental concentrations. Swimming Pools. Our concerns related to swimming pool uses are described in the enclosed letter to the EPA 13 regarding the registration review for another pesticide used in swimming pools, polyhexamethylenebiguanide (PHMB). Materials Preservatives. EPA needs to account for releases of nanosilver during product use, such as from any frequently cleaned or washed items. Dental Unit Water Line Cleaner. With regard to nanosilver used in dental unit water line cleaner, we believe EPA should evaluate both direct discharge of water line cleaners to the sanitary sewer as well as via a dental amalgam separator pretreatment unit. In the San Francisco Bay Area, many wastewater facilities require dental offices to use amalgam separators that pretreat wastewater to remove dental amalgam. Given that nanosilver may be more reactive than other forms of silver, it is important to ensure that nanosilver does not adversely impact the proper operation of amalgam separators, such as inadvertently releasing amalgam captured by the separator. Hard Surface Disinfectant. Whenever any indoor surface is sanitized or disinfected, it is likely that it will eventually be rinsed, washed or wiped down in the near future, likely down an indoor drain that flows to a wastewater treatment facility. We ask EPA to closely all potential exposures from hard surface disinfectants, especially those formulations that are concentrated cleaning products requiring mixing with water, as mixing may result in spills of concentrated product down drains. In addition, leftover portions of cleaners are commonly poured down drains.
10
Nanosilver Conceptual Model. Nanosilver Product Wastewater-Related Environmental Exposures. 12 Geranio, L, M. Heuberger and B. Nowack (2009). The Behavior of Silver Nanotextiles during Washing. Environmental Science and Technology, 2009, 43 (21), pp. 8113–8118; Kemikalieinspektionen (KEMI) (2011). Antibacterial substances leaking from the clothes by washing. The analysis of silver triclosan and triclocarban in textiles before and after washing. Sweden, Swedish Chemicals Agency. 13 BACWA (2012). Comment letter on PHMB Registration Review (Docket ID No. EPA–HQ–OPP–2012-0341). 11
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Evaluate Potential Impacts to Wastewater Treatment Facilities Given that all uses listed in the Summary Document may potentially discharge nanosilver to wastewater treatment plants, BACWA requests that EPA conduct a thorough evaluation of nanosilver’s impacts on these facilities. It is EPA’s responsibility to ensure that nanosilver uses will not result in exceedances of water quality standards, impacts to biosolids management options, nor interference with the microorganisms that are crucial for effective wastewater treatment. Protect Water Quality. Under the Clean Water Act, wastewater facilities are subject to NPDES permits, which include toxicity limits and may also include numeric effluent limitations for silver. Exceeding these limitations has serious consequences; in addition to the potential for adverse environmental impacts, the costs of non-compliance with Clean Water Act requirements can mount quickly. If either toxicity limits or numeric effluent limits are exceeded, wastewater agencies in California may be subject to mandatory minimum penalties, administrative civil liabilities, fines and other enforcement actions. In addition, agencies typically are required to develop source control programs to reduce the source of the pollutant. If toxicity limits are exceeded, staff must be deployed to identify the cause and source of toxicity. Both may involve extensive sampling, costly laboratory fees and significant staff resources. The cost of a toxicity identification evaluation (TIE) can vary widely from $10,000 to well over $100,000. Because silver does not degrade in wastewater treatment, if nanosilver were the source of toxicity, the only proven way to manage it is to prevent it from entering wastewater influent in the first place The California State Water Board is currently considering a regulatory proposal that would move toxicity from a narrative standard to a numeric standard. Exceedances would not only trigger the expensive test described above, but would also be subject to both fines and citizen lawsuits. In addition, when surface water bodies become impaired by pollutants, wastewater facilities may be subject to additional requirements established as part of Total Maximum Daily Loads (TMDLs). Indeed, a number of TMDLs have been adopted or are in preparation to address pesticide-caused water quality impairments in California. The cost to wastewater facilities and other dischargers to comply with TMDLs can be up to millions of dollars per water body per pollutant. It is therefore imperative that EPA exercise its regulatory authority to fully assess the potential for nanosilver to impact water quality and restrict uses so that water quality impacts are prevented. Process Interference. In modern wastewater treatment plants, microorganisms do the basic work of removing fecal matter and dissolved organics in sewage, reducing biological and chemical oxygen demand as well as suspended solids prior to discharge to receiving waters. If a pesticide enters a treatment plant in sufficient quantities, it is possible it could harm these crucial microorganisms, causing “process interference,” or a plant “upset” where wastewater is no longer able to be treated properly before discharge. In the case of a plant upset, microorganisms may either be impaired or killed, such that treatment does not occur for hours, days, or even weeks, resulting in impacts to water quality, fish and wildlife, as well as NPDES permit
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violations. NPDES permit violations are not only costly to wastewater agencies, but the cost to the aquatic environment is immeasurable. Recent research indicates that impacts to wastewater treatment by nanoparticles may be significant. For example, a recent screening environmental risk assessment indicates nanosilver poses potentially significant risks to wastewater treatment and were the greatest risk among all types of environmental releases of nanosilver. 14 In addition, a 2010 Water Environment Research Foundation report 15 and two journal articles showed that nitrifying bacteria are especially susceptible to inhibition by silver nanoparticles and that nutrient removal may be impaired. Biosolids Assessment. BACWA appreciates EPA’s recognition that nanosilver may partition to biosolids. In the 2002-2003 Clean Water Act biennial review for toxic pollutants in sewage sludge, EPA identified silver for further risk evaluation to determine whether it should be regulated in biosolids. 16 The resulting risk assessment is being conducted for land application, incineration, and surface disposal. With approximately fifty percent of wastewater treatment costs allocated to biosolids handling, and about sixty percent of biosolids applied to agricultural land, 17 BACWA’s members are particularly concerned that pesticide residues in biosolids may impact biosolids management options, especially land application to agricultural areas. For biosolids that are incinerated, we are concerned that nanosilver may concentrate in ash, thereby impacting ash reuse or disposal options, or due to its small particle size, be released to the environment through air emissions. Because studies have consistently demonstrated that nanomaterials partition into biosolids during wastewater treatment, 18 we believe that EPA must require environmental fate data for all use patterns and require field studies that identify the impacts, if any, to biosolids management options including land application, incineration and surface disposal. A recent model by Gottschalk et al (2009) conservatively predicted increases of silver nanoparticles in sludge treated soil from 2.3 to 7.4 μg/kg between 2008 and 2012. Currently, little is known about the bioavailability and toxicity of nanosilver in land-applied biosolids; if the presence of nanosilver in biosolids prevented beneficial reuse at landfills or on agricultural land, 14
Gottschalk, F. et al. (2010). Possibilities and Limitations of Modeling Environmental Exposure to Engineered Nanomaterials by Probabilistic Material Flow Analysis. Environmental Toxicology & Chemistry, 29(5): 1036–1048. 15 WERF (2010). Impact of Silver Nanoparticles on Wastewater Treatment; Choi, O., K. K. Deng, et al. (2008). "The inhibitory effects of silver nanoparticles, silver ions, and silver chloride colloids on microbial growth." Water Research 42(12): 3066-3074; Choi, O. and Z. Hu (2008). "Size dependent and reactive oxygen species related nanosilver toxicity to nitrifying bacteria." Environmental Science & Technology 42(12): 4583-4588. 16 See p. 8 of EPA’s Biennial Review of 40 CFR Part 503 As Required Under the Clean Water Act Section 405(d)(2)(C), 2005 Biennial Review Period, January 2006. Available at http://water.epa.gov/scitech/wastetech/biosolids/upload/2009_09_09_biosolids_BR2005_Summary_Final.pdf 17 North East Biosolids and Residuals Association (NEBRA) (2007). A National Biosolids Regulation, Quality, End Use and Disposal Survey. Final Report. http://www.nebiosolids.org/uploads/pdf/NtlBiosolidsReport-20July07.pdf 18 Benn, T. M. and P. Westerhoff (2008). Nanoparticle silver released into water from commercially available sock fabrics. Environmental Science & Technology, 42(11): 4133-4139. Kiser, M. A., P. Westerhoff, et al. (2009). Titanium Nanomaterial Removal and Release from Wastewater Treatment Plants. Environmental Science & Technology, 43(17): 6757-6763. Gottschalk, F., T. Sonderer, et al. (2009). Modeled environmental concentrations of engineered nanomaterials (TiO(2), ZnO, Ag, CNT, Fullerenes) for different regions. Environmental Science & Technology 43(24): 9216-9222.
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wastewater treatment agencies would have to spend at least an additional $100 million annually to manage their biosolids. Rising management costs would translate to higher costs to ratepayers nationwide, placing an undue economic burden on the public that could be avoided by a robust pesticide registration review process. Again, EPA must work to better understand the impacts of nanosilver on biosolids management. To this end, BACWA urges the Offices of Pesticide Programs (OPP), Water (Offices of Wastewater Management and Science and Technology), and Research and Development to together develop a methodology that evaluates potential impacts of pesticides to biosolids land application whenever the EFAST Down-The-Drain module assessments indicate that pesticides would partition into biosolids. The existing OPP guidelines for the study of chemicals in the terrestrial environment could be modified to address biosolids-amended soil systems. In addition, the evaluation should include an analysis of bioaccumulation, toxicity to microbes, and toxicity to worms and other terrestrial invertebrates. This will entail requiring the registrant to conduct the studies such as a soil microbial community toxicity test (OPPTS Guideline 850.3200) and an earthworm subchronic toxicity test (OPPTS Guideline 850.3100). It should be noted that such evaluations should focus on fate, transport, and toxicity factors specifically applicable to the biosolids matrix, and not merely done on pure chemical compounds or pot studies. Such studies are important to accurately quantify fate, exposure, and risk from the use of pesticides that will likely partition into biosolids if discharged to wastewater treatment facilities. Because there is so much uncertainty regarding fate and transport of nanoparticles, sufficient research must be conducted to answer the question of whether nanosilver may have adverse human or environmental impacts. This registration review process is the appropriate venue for that assessment. Evaluate Risks of Final Products When reviewing products containing nanoscale pesticides, it is important for EPA to evaluate the environmental risks associated with the final product that is sold to the consumer, including any carrier material. For example, nanoscale pesticides are used in products like treated wood and fabrics that are not ordinarily labeled as pesticides. In some of these products, the nanoscale material is created during the treatment of the material. 19 In addition, EPA should also evaluate the impacts of disposal of products treated with nanosilver, particularly products that consumers would not normally consider as hazardous, such as clothing, wipes, toilets, urinals, glassware, etc. California’s hazardous waste standard for total silver content is 500 parts per million (ppm). 20 Require Registrants to Develop Practical Environmental Chemical Analysis Methods To detect pollutants, local, state and federal surface water quality monitoring programs need analytical methods with sufficiently low detection limits that are practicable in commercial and 19
For an example where the consumer product manufacturing process creates a nanoscale pesticide with properties that differ from those of the individual input materials, see Borkow, G., and J. Gabbay (2004). Putting copper into action: copper impregnated products with potent biocidal activities. FASEB Journal 18: 1728-1730. 20 California Code of Regulations, Title 22, Chapter 11, Article 3.
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government analytical laboratories. There are no such methods for nanoparticles, though it is especially important to have sufficiently sensitive analytical methods for environmentally relevant matrices such as surface water, sediments, and wastewater influent, effluent and biosolids. We believe that the manufacturer, at the time of registration of its product, should be responsible for development of these methods. BACWA requests that EPA require the registrants to develop water, sediment, soil, wastewater, and biosolids methods for nanosilver with appropriate method detection limits. We concur with CASQA’s recommendation to consider drawing from California Department of Pesticide Regulation’s specifications for pesticide analysis method development. Water Quality Monitoring Data In the Summary Document, EPA has noted that there are no impairments listed nor TMDLs developed for nanosilver (p. 11). This statistic is not surprising, given that there are no practical chemical analysis methods for nanosilver. However, it is notable that there are seventy-nine 303(d) listings 21 and sixty-two TMDLs for silver. 22 We encourage EPA to require registrants to develop appropriate analytical methods and then to conduct monitoring for their products in the environment, including in municipal wastewater. Investigate Cumulative Impacts of Nanosilver Products with Silver Products BACWA is concerned that toxicity related to nanosilver could be additive with other forms of silver pesticides, including silver nitrate, silver chloride, and colloidal and ionic silver. While nanosilver is likely to display different fate and effects characteristics than these forms of silver, silver does not degrade in the environment. To better understand whether nanosilver and other forms of silver pesticides could pose a cumulative impact, we urge OPP to employ the DownThe-Drain module of the EFAST module to quantify potential environmental concentrations of both nanosilver and silver; where there is insufficient data for the Down-The-Drain module, we urge EPA to require this data from the registrant. Why Pesticide Registration & Review Process Must Prevent Water Quality Impacts It is essential that pesticide regulatory processes adequately consider impacts to wastewater treatment processes, wastewater effluent and biosolids, so that such impacts are prevented before they result in impairments to water quality, management issues with biosolids, and/or violations of NPDES permit requirements. Due to strict silver effluent limits in discharge permits, wastewater agencies have implemented pollution prevention programs to identify and reduce silver discharges to sanitary sewer systems. These programs have been very successful in reducing wastewater influent and effluent silver concentrations. However, widespread use of pesticide products that release silver into 21
See http://ofmpub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=706 See http://ofmpub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=706&p_pollutant _group_name=METALS%20%28OTHER%20THAN%20MERCURY%29
22
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wastewater systems could greatly increase silver concentrations in wastewater influent and effluent, leading to adverse effects on California waterways. Due to its small particle size, nanosilver may have unique impacts on biological treatment processes and on the ecosystems receiving wastewater effluent and biosolids. Now is the time to identify the environmental impacts of nanosilver and develop appropriate regulations. Failure to do so could lead to environmental impacts, fines and compliance costs to wastewater facilities. It is EPA’s responsibility in the pesticide registration process to obtain the data necessary to fully evaluate whether nanosilver uses would cause adverse environmental impacts, and then to restrict uses so that the impacts are prevented. Thank you for your consideration of our comments. If you have any questions, please contact BACWA’s Project Manager, Melody LaBella, at (925) 229-7370 or [email protected]. Sincerely,
James M. Kelly Executive Director Enclosures 1. Nanosilver Conceptual Model. 2. Nanosilver Product Wastewater-Related Environmental Exposures. 3. Comparison of Nanosilver and Bifenthrin Registration Review Environmental Risk Documents. 4. BACWA (2009). Comment Letter on Nanosilver Petition (Docket Number EPA-HQOPP-2008-0650). 5. Tri-TAC (2009). Comment Letter on Silver Registration Review (Docket Number EPA– HQ–OPP–2009–0334). 6. Tri-TAC (2011). Comment Letter on Nanomaterials Policy (Docket ID Number EPA– HQ–OPP–2010–0197). 7. EPA Office of Research and Development (2012). Nanomaterial Case Study: Nanoscale Silver in Disinfectant Spray. 8. Tri-Tac (2010). Comment Letter on Draft Nanomaterials Case Study on Silver (Docket ID Number EPA-HQ-ORD-2010-0658). 9. Luoma, S. N. (2008). Silver Nanotechnologies and the Environment: Old Problems or New Challenges? Woodrow Wilson International Center for Scholars, Project on Emerging Nanotechnologies. Publication PEN 15. 10. Judy, J.D., et al. (2012). Bioavailability of Gold Nanomaterials to Plants: Importance of Particle Size and Surface Coating. Environmental Science and Technology, 46 (15): 8467–8474. 11. Huynh, K.A. and K.L. Chen (2011). Aggregation Kinetics of Citrate and Polyvinylpyrrolidone Coated Silver Nanoparticles in Monovalent and Divalent Electrolyte Solutions. Environmental Science and Technology, 45 (13): 5564–5571.
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12. Griffitt, R.J., et al. (2008). Effects of Particle Composition and Species on Toxicity of Metallic Nanomaterials in Aquatic Organisms. Environmental Toxicology and Chemistry, 27 (9): 1972–1978. 13. Judy, J.D., et al. (2011). Evidence for Biomagnification of Gold. Environmental Science and Technology, 45 (2): 776–781. 14. Geranio, L, M. Heuberger and B. Nowack (2009). The Behavior of Silver Nanotextiles during Washing. Environmental Science and Technology, 2009, 43 (21), pp. 8113–8118. 15. Kemikalieinspektionen (KEMI) (2011). Antibacterial substances leaking from the clothes by washing. The analysis of silver triclosan and triclocarban in textiles before and after washing. Sweden, Swedish Chemicals Agency. 16. BACWA (2012). Comment letter on PHMB Registration Review (Docket ID No. EPA– HQ–OPP–2012-0341). 17. Gottschalk, F. et al. (2010). Possibilities and Limitations of Modeling Environmental Exposure to Engineered Nanomaterials by Probabilistic Material Flow Analysis. Environmental Toxicology & Chemistry, 29(5): 1036–1048. 18. WERF (2010). Impact of Silver Nanoparticles on Wastewater Treatment. 19. Choi, O., K. K. Deng, et al. (2008). "The inhibitory effects of silver nanoparticles, silver ions, and silver chloride colloids on microbial growth." Water Research 42(12): 30663074. 20. Choi, O. and Z. Hu (2008). "Size dependent and reactive oxygen species related nanosilver toxicity to nitrifying bacteria." Environmental Science & Technology 42(12): 4583-4588. 21. Benn, T. M. and P. Westerhoff (2008). Nanoparticle silver released into water from commercially available sock fabrics. Environmental Science & Technology, 42(11): 4133-4139. 22. Kiser, M. A., P. Westerhoff, et al. (2009). Titanium Nanomaterial Removal and Release from Wastewater Treatment Plants. Environmental Science & Technology, 43(17): 67576763. 23. Gottschalk, F., T. Sonderer, et al. (2009). Modeled environmental concentrations of engineered nanomaterials (TiO(2), ZnO, Ag, CNT, Fullerenes) for different regions. Environmental Science & Technology 43(24): 9216-9222. 24. Borkow, G., and J. Gabbay (2004). Putting copper into action: copper impregnated products with potent biocidal activities. FASEB Journal 18: 1728-1730. cc: Steve Bradbury, Director, U.S. EPA Office of Pesticide Programs Jed Costanza, U.S. EPA U.S. EPA Office of Pesticide Programs, Antimicrobials Division Joan Harrigan-Farelly, Director, U.S. EPA U.S. EPA Office of Pesticide Programs, Antimicrobials Division Lance Wormell, U.S. EPA Office of Pesticide Programs, Regulatory Management Branch II Mark Hartman, Branch Chief, U.S. EPA Office of Pesticide Programs, Regulatory Management Branch II Philip Ross, U.S. EPA Office of General Counsel Amber Aranda, U.S. EPA Office of General Counsel Sriniva Gowda, U.S. EPA Office of Pesticide Programs, Risk Assessment and Science Support Branch
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Nader Elkassabany, Branch Chief, U.S. EPA Office of Pesticide Programs, Risk Assessment and Science Support Branch Kirk Scheckel, US EPA National Risk Management Research Laboratory Land Remediation and Pollution Control Division Rick P. Keigwin, Jr., U.S. EPA Office of Pesticide Programs, Pesticide Re-Evaluation Division Betsy Southerland, Director, U.S. EPA Office of Water, Office of Science and Technology Randy Hill, Acting Director, U.S. EPA Office of Water, Office of Wastewater Management Nancy Woo, Acting Director, Water Division, U.S. EPA Region 9 Debra Denton, U.S. EPA Region 9 Patti TenBrook, Life Scientist, U.S. EPA Region 9 Syed Ali, California State Water Resources Control Board Tom Mumley, California Regional Water Quality Control Board, San Francisco Bay Region Janet O'Hara, California Regional Water Quality Control Board, San Francisco Bay Region Daniel McClure, California Regional Water Quality Control Board, Central Valley Region Tessa Fojut, California Regional Water Quality Control Board, Central Valley Region Marylou Verder-Carlos, California Department of Pesticide Regulation Nan Singhasemanon, California Department of Pesticide Regulation Kelly D. Moran, Urban Pesticides Pollution Prevention Project Greg Kester, California Association of Sanitation Agencies Chris Hornback, Senior Director, Regulatory Affairs, National Association of Clean Water Agencies
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Nanosilver Product Wastewater-Related Environmental Exposures Product Silver Algaedyn
Use Swimming pool algaecide
ASAP-AGX and ASAP AGX-32
Hard surface disinfectant, controls odor-causing bacteria in dental water lines and bacteriostat
H2PRO
Controls odor causing bacteria in dental water lines Preservative in a wide variety of commercial and consumer products
Additive SSB
HeiQ AGS-20 and HeiQ AGS20U
Materials preservative for household textiles, apparel, and outdoor fabrics
Exposure Scenarios Swimming pools are emptied for maintenance about once every 2-7 years on average. In cold areas, pools are partially emptied each fall to prevent damage from freezing. When the pool is emptied, the nanosilver flows out along with the water. Pool water may be discharged to the sewer system (where it flows to a municipal wastewater treatment plant), to a gutter (where it flows to a storm drain) or into landscaping (which may include food-growing gardens).
Filter backwashing occurs regularly. Nanosilver may be discharged to sewers or storm drains from filter backwashing. Cleaning preserved materials transfers nanosilver to cleaning water and cleaning materials (sponges, mops, cloths) that are subsequently washed. Dental water line discharges, cleaning water and water from washing sponges, mops, and cloths are discharged to sewers, where the water flows to municipal wastewater treatment plants. Dental water lines discharge to sewers, where water flows to municipal wastewater treatment plants. Cleaning preserved materials transfers nanosilver to cleaning water and cleaning materials (sponges, mops, cloths) that are subsequently washed. Cleaning water and water from washing sponges, mops, and cloths are discharged to sewers, where it flows to municipal wastewater treatment plants. Leaches out of fabrics when washed. Washing machines discharge to sewers, where water flows to municipal wastewater treatment plants.
Environmental exposure pathways: Nanosilver particles (and any silver degradation products) may be transferred to biosolids (sewage sludge), effluent, or recycled water. Municipal wastewater treatment plant effluent flows into rivers, estuaries, or the ocean. In some cases, it may pass through freshwater or saltwater wetlands in the
final phase of treatment or upon discharge. Rivers receiving wastewater discharges may be sources of drinking water. Biosolids (sewage sludge) may be landfilled, incinerated (generating waste ash), or further treated prior to use as fertilizer in agriculture or urban gardens.
Recycled water may be used for irrigation, toilet flushing, groundwater recharge, or even as an input to drinking water systems.
It is unclear how the particle coating affects the fate of nanosilver that is transported in particle form.
Comparison of Nanosilver and Bifenthrin Registration Review Environmental Risk Documents Bifenthrin Nanosilver
Topic Purpose Review of available data Statement of ecological risk hypothesis Plan for risk evaluation and characterization Stressor source and distribution Summary of environmental chemistry data Description of mechanism of action Overview of pesticide usage Overview of pesticide use patterns Environmental fate & transport Receptors Aquatic and terrestrial effects data summary Identification of ecosystems potentially at risk Conceptual model Risk hypothesis Conceptual model diagram Analysis plan Stressors of concern Measures of exposure Measures of effect Integration of exposure and effects Assessment methods Preliminary identification of data gaps Data Request Data request justification tables Readability Summary Table of contents Document text can be searched
X X X X X X X X X X
X (HeiQ AGS-20 only) X X (HeiQ AGS-20 only)
X (HeiQ AGS-20 aquatic toxicity only)
X X X X X X X X X X X X
X (HeiQ AGS-20 only) X (HeiQ AGS-20 only)
Nanosilver Registration Review, Case # 5042 (Docket ID Number EPA–HQ–OPP– 2011-0370)
Dear Ms. Henson: On behalf of the Bay Area Clean Water Agencies (BACWA), we thank you for the opportunity to comment on the registration review for nanosilver. BACWA’s members include fifty-five publicly-owned wastewater treatment facilities and collection system agencies serving 6.5 million San Francisco Bay Area residents. We take our responsibilities for safeguarding receiving waters seriously and are very concerned about discharges of pesticides into wastewater systems that may compromise receiving water quality, effluent quality, biosolids reuse, and compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. BACWA’s Interest in Nanosilver Registration Review BACWA and our colleagues in the wastewater sector have been actively engaged in issues related to silver and nanosilver for many years. For your review, we have enclosed several letters to EPA detailing our concerns about silver and nanosilver pesticides and a report from a wellrespected San Francisco Bay Area scientist, Dr. Samuel Luoma, that explores risks of nanosilver in the context of the history of silver water pollution in the San Francisco Bay Area. 1 BACWA is specifically interested in this registration review for nanosilver because we believe all the use patterns noted in the Environmental Summary (“Nanosilver: Summary of Environmental Fate and Ecotoxicity Data for Registration Review,” pp. 2-3) may result discharges of nanosilver to wastewater treatment plants. While little is known about the fate and effects of nanosilver, we do know that silver is highly toxic to aquatic life at low concentrations, is persistent, and can bioaccumulate in some aquatic organisms, such as clams. Wastewater agencies have noted with some alarm that new product lines containing nanosilver
1
BACWA (2009). Comment Letter on Nanosilver Petition. Tri-TAC (2009). Comment Letter on Silver Registration Review. Tri-TAC (2011). Comment Letter on Nanomaterials Policy. Luoma, S. N. (2008). Silver Nanotechnologies and the Environment: Old Problems or New Challenges? Woodrow Wilson International Center for Scholars, Project on Emerging Nanotechnologies. Publication PEN 15.
BACWA Comments on Nanosilver Registration Review (Docket ID Number EPA–HQ–OPP– 2011-0370) p. 2
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are quickly expanding, as detailed in EPA’s recently released case study on nanosilver. 2 Use of nanosilver products could substantially increase the total quantity of silver discharged to wastewater facilities, potentially increasing environmental concentrations and therefore environmental risks. Ignoring these risks could be extremely costly for the environment and the wastewater community. Below we have outlined questions, concerns and requests we have regarding nanosilver and the nanosilver registration review process. Address Data Gaps Before Registration The EPA nanomaterials case study on nanosilver disinfectants reveals numerous outstanding scientific questions related to the environmental fate, risks and toxicity of nanosilver. 3 In fact, EPA states that, “Efforts thus far to assess nanomaterial impacts on environmental and human health demonstrate that data gaps…currently impede carrying out assessments and generally restrict evaluations to limited aspects of specific nanomaterials” (p.7-26). BACWA believes these questions and many other issues should be resolved before EPA allows nanosilver products to be used. We concur with our colleagues at Tri-TAC, who, in a recent letter to EPA, 4 requested that EPA answer the following questions, which may be appropriately addressed through registration review data requirements. • • • • • •
•
What quantities of nanomaterials and metallic ions are now being used as antimicrobial agents in commercial products, both those registered and not registered by EPA? What percentage of metallic nanomaterials will be converted to the ionic form prior to and during the wastewater treatment process? What fraction of nanomaterials and metallic ions will end up in the treated wastewater and what fraction will end up in the biosolids? What is the anticipated removal efficiency of nanomaterials in wastewater treatment plants? What quantities and concentrations of nanomaterials and metallic ions will be released to wastewater treatment plants and the natural environment from the cumulative total of these products being marketed and registered? What affect does nanosilver have on biological wastewater treatment processes such as those used in municipal wastewater treatment plants? To what extent could nanosilver reduce treatment effectiveness, increasing releases of other pollutants into surface waters? If it is shown that nanomaterials partition to biosolids, what impacts will that impart on the beneficial use of biosolids?
2
EPA Office of Research and Development (2012). Nanomaterial Case Study: Nanoscale Silver in Disinfectant Spray. 3 Ibid. 4 Tri-Tac (2010). Comment Letter on Draft Nanomaterials Case Study on Silver (Docket ID Number EPA-HQORD-2010-0658).
2
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In addition, BACWA also asks that EPA address the following questions. •
•
•
How do nanoparticle characteristics, particularly surface coatings, affect the environmental fate and toxicity of nanoparticles? Recent studies show that both particle size and surface coating affect the environmental fate, toxicity, and bioavailability of nanosilver. 5,6 Are nanoparticles able to deliver silver ions to new environmental locations, perhaps within organisms that take them up? For example, filter-feeding organisms have been shown to be more sensitive to nanosilver, 7 maybe because they are ingesting and accumulating the particles. What is the potential for nanosilver to accumulate in aquatic and terrestrial food chains? Recent research indicates that gold nanoparticles biomagnify in a terrestrial food chain. 8
Develop Robust Analysis Plan and Conceptual Model In the recent past, EPA has made progress in its assessment plans so that they better evaluate uses resulting in discharges to wastewater treatment facilities; however, the nanosilver registration review docket does not provide the level of detail often included in most OPP environmental risk assessment work plans. For example, the docket primarily focuses on HeiQ formulations, and does not address risks, data gaps or data requirements pertaining to other registered uses beyond fabric treatments; it also does not include critical elements such as problem formulations, risk hypotheses, conceptual models and analysis plans. BACWA encourages EPA to develop a more robust and informative assessment plan for nanosilver that is consistent with other pesticide registration review dockets. For a strong example of an environmental risk assessment work plan, the Antimicrobials Division may look to the Environmental Fate & Effects Division’s (EFED’s) Registration Review Problem Formulation for Bifenthrin (Docket ID Number EPA–HQ–OPP–2010–0384). To illustrate the need for more in-depth risk assessment work planning, we have enclosed a side-by-side comparison of the nanosilver registration review environmental work plan document versus the bifenthrin registration review environmental work plan document. 9 Evaluate All Use Patterns for Environmental Exposures While we appreciate the Antimicrobial Division’s recognition in the Environmental Summary that nanosilver in treated fabrics may be discharged to wastewater treatment plants (p. 7), 5
Judy, J.D., et al. (2012). Bioavailability of Gold Nanomaterials to Plants: Importance of Particle Size and Surface Coating. Environmental Science and Technology, 46 (15): 8467–8474. 6 Huynh, K.A. and K.L. Chen (2011). Aggregation Kinetics of Citrate and Polyvinylpyrrolidone Coated Silver Nanoparticles in Monovalent and Divalent Electrolyte Solutions. Environmental Science and Technology, 45 (13): 5564–5571. 7 Griffitt, R.J., et al. (2008). Effects of Particle Composition and Species on Toxicity of Metallic Nanomaterials in Aquatic Organisms. Environmental Toxicology and Chemistry, 27 (9): 1972–1978. 8 Judy, J.D., et al. (2011). Evidence for Biomagnification of Gold. Environmental Science and Technology, 45 (2): 776–781. 9 Comparison of Nanosilver and Bifenthrin Registration Review Environmental Risk Documents.
3
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BACWA requests that EPA evaluate all use patterns (pp. 2-3) for potential environmental exposures. To illustrate how current uses may result in exposures in the aquatic and terrestrial environments, we have enclosed a conceptual model 10 that incorporates uses presented in the Environmental Summary, and a table 11 describing how specific product use patterns can cause environmental exposures. Below, we provide our concerns about use patterns more generally. Fabric Treatments. EPA states that further environmental fate studies may be required of the HeiQ registrant if studies show that nanosilver is released from fabric treatments. There is already evidence that fabrics treated with nanosilver release nanosilver as they are washed. 12 EPA also states that nanosilver fabric treatments will not likely impact wastewater treatment operations due to the current low volume of use (Environmental Summary, p. 7). However, once registered, sales of nanosilver-treated clothing may grow without any further regulatory action or evaluation by EPA; therefore, greater volumes of nanosilver may be released to wastewater treatment facilities, posing increasing environmental concentrations. Swimming Pools. Our concerns related to swimming pool uses are described in the enclosed letter to the EPA 13 regarding the registration review for another pesticide used in swimming pools, polyhexamethylenebiguanide (PHMB). Materials Preservatives. EPA needs to account for releases of nanosilver during product use, such as from any frequently cleaned or washed items. Dental Unit Water Line Cleaner. With regard to nanosilver used in dental unit water line cleaner, we believe EPA should evaluate both direct discharge of water line cleaners to the sanitary sewer as well as via a dental amalgam separator pretreatment unit. In the San Francisco Bay Area, many wastewater facilities require dental offices to use amalgam separators that pretreat wastewater to remove dental amalgam. Given that nanosilver may be more reactive than other forms of silver, it is important to ensure that nanosilver does not adversely impact the proper operation of amalgam separators, such as inadvertently releasing amalgam captured by the separator. Hard Surface Disinfectant. Whenever any indoor surface is sanitized or disinfected, it is likely that it will eventually be rinsed, washed or wiped down in the near future, likely down an indoor drain that flows to a wastewater treatment facility. We ask EPA to closely all potential exposures from hard surface disinfectants, especially those formulations that are concentrated cleaning products requiring mixing with water, as mixing may result in spills of concentrated product down drains. In addition, leftover portions of cleaners are commonly poured down drains.
10
Nanosilver Conceptual Model. Nanosilver Product Wastewater-Related Environmental Exposures. 12 Geranio, L, M. Heuberger and B. Nowack (2009). The Behavior of Silver Nanotextiles during Washing. Environmental Science and Technology, 2009, 43 (21), pp. 8113–8118; Kemikalieinspektionen (KEMI) (2011). Antibacterial substances leaking from the clothes by washing. The analysis of silver triclosan and triclocarban in textiles before and after washing. Sweden, Swedish Chemicals Agency. 13 BACWA (2012). Comment letter on PHMB Registration Review (Docket ID No. EPA–HQ–OPP–2012-0341). 11
4
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September 7, 2012
Evaluate Potential Impacts to Wastewater Treatment Facilities Given that all uses listed in the Summary Document may potentially discharge nanosilver to wastewater treatment plants, BACWA requests that EPA conduct a thorough evaluation of nanosilver’s impacts on these facilities. It is EPA’s responsibility to ensure that nanosilver uses will not result in exceedances of water quality standards, impacts to biosolids management options, nor interference with the microorganisms that are crucial for effective wastewater treatment. Protect Water Quality. Under the Clean Water Act, wastewater facilities are subject to NPDES permits, which include toxicity limits and may also include numeric effluent limitations for silver. Exceeding these limitations has serious consequences; in addition to the potential for adverse environmental impacts, the costs of non-compliance with Clean Water Act requirements can mount quickly. If either toxicity limits or numeric effluent limits are exceeded, wastewater agencies in California may be subject to mandatory minimum penalties, administrative civil liabilities, fines and other enforcement actions. In addition, agencies typically are required to develop source control programs to reduce the source of the pollutant. If toxicity limits are exceeded, staff must be deployed to identify the cause and source of toxicity. Both may involve extensive sampling, costly laboratory fees and significant staff resources. The cost of a toxicity identification evaluation (TIE) can vary widely from $10,000 to well over $100,000. Because silver does not degrade in wastewater treatment, if nanosilver were the source of toxicity, the only proven way to manage it is to prevent it from entering wastewater influent in the first place The California State Water Board is currently considering a regulatory proposal that would move toxicity from a narrative standard to a numeric standard. Exceedances would not only trigger the expensive test described above, but would also be subject to both fines and citizen lawsuits. In addition, when surface water bodies become impaired by pollutants, wastewater facilities may be subject to additional requirements established as part of Total Maximum Daily Loads (TMDLs). Indeed, a number of TMDLs have been adopted or are in preparation to address pesticide-caused water quality impairments in California. The cost to wastewater facilities and other dischargers to comply with TMDLs can be up to millions of dollars per water body per pollutant. It is therefore imperative that EPA exercise its regulatory authority to fully assess the potential for nanosilver to impact water quality and restrict uses so that water quality impacts are prevented. Process Interference. In modern wastewater treatment plants, microorganisms do the basic work of removing fecal matter and dissolved organics in sewage, reducing biological and chemical oxygen demand as well as suspended solids prior to discharge to receiving waters. If a pesticide enters a treatment plant in sufficient quantities, it is possible it could harm these crucial microorganisms, causing “process interference,” or a plant “upset” where wastewater is no longer able to be treated properly before discharge. In the case of a plant upset, microorganisms may either be impaired or killed, such that treatment does not occur for hours, days, or even weeks, resulting in impacts to water quality, fish and wildlife, as well as NPDES permit
5
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September 7, 2012
violations. NPDES permit violations are not only costly to wastewater agencies, but the cost to the aquatic environment is immeasurable. Recent research indicates that impacts to wastewater treatment by nanoparticles may be significant. For example, a recent screening environmental risk assessment indicates nanosilver poses potentially significant risks to wastewater treatment and were the greatest risk among all types of environmental releases of nanosilver. 14 In addition, a 2010 Water Environment Research Foundation report 15 and two journal articles showed that nitrifying bacteria are especially susceptible to inhibition by silver nanoparticles and that nutrient removal may be impaired. Biosolids Assessment. BACWA appreciates EPA’s recognition that nanosilver may partition to biosolids. In the 2002-2003 Clean Water Act biennial review for toxic pollutants in sewage sludge, EPA identified silver for further risk evaluation to determine whether it should be regulated in biosolids. 16 The resulting risk assessment is being conducted for land application, incineration, and surface disposal. With approximately fifty percent of wastewater treatment costs allocated to biosolids handling, and about sixty percent of biosolids applied to agricultural land, 17 BACWA’s members are particularly concerned that pesticide residues in biosolids may impact biosolids management options, especially land application to agricultural areas. For biosolids that are incinerated, we are concerned that nanosilver may concentrate in ash, thereby impacting ash reuse or disposal options, or due to its small particle size, be released to the environment through air emissions. Because studies have consistently demonstrated that nanomaterials partition into biosolids during wastewater treatment, 18 we believe that EPA must require environmental fate data for all use patterns and require field studies that identify the impacts, if any, to biosolids management options including land application, incineration and surface disposal. A recent model by Gottschalk et al (2009) conservatively predicted increases of silver nanoparticles in sludge treated soil from 2.3 to 7.4 μg/kg between 2008 and 2012. Currently, little is known about the bioavailability and toxicity of nanosilver in land-applied biosolids; if the presence of nanosilver in biosolids prevented beneficial reuse at landfills or on agricultural land, 14
Gottschalk, F. et al. (2010). Possibilities and Limitations of Modeling Environmental Exposure to Engineered Nanomaterials by Probabilistic Material Flow Analysis. Environmental Toxicology & Chemistry, 29(5): 1036–1048. 15 WERF (2010). Impact of Silver Nanoparticles on Wastewater Treatment; Choi, O., K. K. Deng, et al. (2008). "The inhibitory effects of silver nanoparticles, silver ions, and silver chloride colloids on microbial growth." Water Research 42(12): 3066-3074; Choi, O. and Z. Hu (2008). "Size dependent and reactive oxygen species related nanosilver toxicity to nitrifying bacteria." Environmental Science & Technology 42(12): 4583-4588. 16 See p. 8 of EPA’s Biennial Review of 40 CFR Part 503 As Required Under the Clean Water Act Section 405(d)(2)(C), 2005 Biennial Review Period, January 2006. Available at http://water.epa.gov/scitech/wastetech/biosolids/upload/2009_09_09_biosolids_BR2005_Summary_Final.pdf 17 North East Biosolids and Residuals Association (NEBRA) (2007). A National Biosolids Regulation, Quality, End Use and Disposal Survey. Final Report. http://www.nebiosolids.org/uploads/pdf/NtlBiosolidsReport-20July07.pdf 18 Benn, T. M. and P. Westerhoff (2008). Nanoparticle silver released into water from commercially available sock fabrics. Environmental Science & Technology, 42(11): 4133-4139. Kiser, M. A., P. Westerhoff, et al. (2009). Titanium Nanomaterial Removal and Release from Wastewater Treatment Plants. Environmental Science & Technology, 43(17): 6757-6763. Gottschalk, F., T. Sonderer, et al. (2009). Modeled environmental concentrations of engineered nanomaterials (TiO(2), ZnO, Ag, CNT, Fullerenes) for different regions. Environmental Science & Technology 43(24): 9216-9222.
6
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September 7, 2012
wastewater treatment agencies would have to spend at least an additional $100 million annually to manage their biosolids. Rising management costs would translate to higher costs to ratepayers nationwide, placing an undue economic burden on the public that could be avoided by a robust pesticide registration review process. Again, EPA must work to better understand the impacts of nanosilver on biosolids management. To this end, BACWA urges the Offices of Pesticide Programs (OPP), Water (Offices of Wastewater Management and Science and Technology), and Research and Development to together develop a methodology that evaluates potential impacts of pesticides to biosolids land application whenever the EFAST Down-The-Drain module assessments indicate that pesticides would partition into biosolids. The existing OPP guidelines for the study of chemicals in the terrestrial environment could be modified to address biosolids-amended soil systems. In addition, the evaluation should include an analysis of bioaccumulation, toxicity to microbes, and toxicity to worms and other terrestrial invertebrates. This will entail requiring the registrant to conduct the studies such as a soil microbial community toxicity test (OPPTS Guideline 850.3200) and an earthworm subchronic toxicity test (OPPTS Guideline 850.3100). It should be noted that such evaluations should focus on fate, transport, and toxicity factors specifically applicable to the biosolids matrix, and not merely done on pure chemical compounds or pot studies. Such studies are important to accurately quantify fate, exposure, and risk from the use of pesticides that will likely partition into biosolids if discharged to wastewater treatment facilities. Because there is so much uncertainty regarding fate and transport of nanoparticles, sufficient research must be conducted to answer the question of whether nanosilver may have adverse human or environmental impacts. This registration review process is the appropriate venue for that assessment. Evaluate Risks of Final Products When reviewing products containing nanoscale pesticides, it is important for EPA to evaluate the environmental risks associated with the final product that is sold to the consumer, including any carrier material. For example, nanoscale pesticides are used in products like treated wood and fabrics that are not ordinarily labeled as pesticides. In some of these products, the nanoscale material is created during the treatment of the material. 19 In addition, EPA should also evaluate the impacts of disposal of products treated with nanosilver, particularly products that consumers would not normally consider as hazardous, such as clothing, wipes, toilets, urinals, glassware, etc. California’s hazardous waste standard for total silver content is 500 parts per million (ppm). 20 Require Registrants to Develop Practical Environmental Chemical Analysis Methods To detect pollutants, local, state and federal surface water quality monitoring programs need analytical methods with sufficiently low detection limits that are practicable in commercial and 19
For an example where the consumer product manufacturing process creates a nanoscale pesticide with properties that differ from those of the individual input materials, see Borkow, G., and J. Gabbay (2004). Putting copper into action: copper impregnated products with potent biocidal activities. FASEB Journal 18: 1728-1730. 20 California Code of Regulations, Title 22, Chapter 11, Article 3.
7
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government analytical laboratories. There are no such methods for nanoparticles, though it is especially important to have sufficiently sensitive analytical methods for environmentally relevant matrices such as surface water, sediments, and wastewater influent, effluent and biosolids. We believe that the manufacturer, at the time of registration of its product, should be responsible for development of these methods. BACWA requests that EPA require the registrants to develop water, sediment, soil, wastewater, and biosolids methods for nanosilver with appropriate method detection limits. We concur with CASQA’s recommendation to consider drawing from California Department of Pesticide Regulation’s specifications for pesticide analysis method development. Water Quality Monitoring Data In the Summary Document, EPA has noted that there are no impairments listed nor TMDLs developed for nanosilver (p. 11). This statistic is not surprising, given that there are no practical chemical analysis methods for nanosilver. However, it is notable that there are seventy-nine 303(d) listings 21 and sixty-two TMDLs for silver. 22 We encourage EPA to require registrants to develop appropriate analytical methods and then to conduct monitoring for their products in the environment, including in municipal wastewater. Investigate Cumulative Impacts of Nanosilver Products with Silver Products BACWA is concerned that toxicity related to nanosilver could be additive with other forms of silver pesticides, including silver nitrate, silver chloride, and colloidal and ionic silver. While nanosilver is likely to display different fate and effects characteristics than these forms of silver, silver does not degrade in the environment. To better understand whether nanosilver and other forms of silver pesticides could pose a cumulative impact, we urge OPP to employ the DownThe-Drain module of the EFAST module to quantify potential environmental concentrations of both nanosilver and silver; where there is insufficient data for the Down-The-Drain module, we urge EPA to require this data from the registrant. Why Pesticide Registration & Review Process Must Prevent Water Quality Impacts It is essential that pesticide regulatory processes adequately consider impacts to wastewater treatment processes, wastewater effluent and biosolids, so that such impacts are prevented before they result in impairments to water quality, management issues with biosolids, and/or violations of NPDES permit requirements. Due to strict silver effluent limits in discharge permits, wastewater agencies have implemented pollution prevention programs to identify and reduce silver discharges to sanitary sewer systems. These programs have been very successful in reducing wastewater influent and effluent silver concentrations. However, widespread use of pesticide products that release silver into 21
See http://ofmpub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=706 See http://ofmpub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=706&p_pollutant _group_name=METALS%20%28OTHER%20THAN%20MERCURY%29
22
8
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wastewater systems could greatly increase silver concentrations in wastewater influent and effluent, leading to adverse effects on California waterways. Due to its small particle size, nanosilver may have unique impacts on biological treatment processes and on the ecosystems receiving wastewater effluent and biosolids. Now is the time to identify the environmental impacts of nanosilver and develop appropriate regulations. Failure to do so could lead to environmental impacts, fines and compliance costs to wastewater facilities. It is EPA’s responsibility in the pesticide registration process to obtain the data necessary to fully evaluate whether nanosilver uses would cause adverse environmental impacts, and then to restrict uses so that the impacts are prevented. Thank you for your consideration of our comments. If you have any questions, please contact BACWA’s Project Manager, Melody LaBella, at (925) 229-7370 or [email protected]. Sincerely,
James M. Kelly Executive Director Enclosures 1. Nanosilver Conceptual Model. 2. Nanosilver Product Wastewater-Related Environmental Exposures. 3. Comparison of Nanosilver and Bifenthrin Registration Review Environmental Risk Documents. 4. BACWA (2009). Comment Letter on Nanosilver Petition (Docket Number EPA-HQOPP-2008-0650). 5. Tri-TAC (2009). Comment Letter on Silver Registration Review (Docket Number EPA– HQ–OPP–2009–0334). 6. Tri-TAC (2011). Comment Letter on Nanomaterials Policy (Docket ID Number EPA– HQ–OPP–2010–0197). 7. EPA Office of Research and Development (2012). Nanomaterial Case Study: Nanoscale Silver in Disinfectant Spray. 8. Tri-Tac (2010). Comment Letter on Draft Nanomaterials Case Study on Silver (Docket ID Number EPA-HQ-ORD-2010-0658). 9. Luoma, S. N. (2008). Silver Nanotechnologies and the Environment: Old Problems or New Challenges? Woodrow Wilson International Center for Scholars, Project on Emerging Nanotechnologies. Publication PEN 15. 10. Judy, J.D., et al. (2012). Bioavailability of Gold Nanomaterials to Plants: Importance of Particle Size and Surface Coating. Environmental Science and Technology, 46 (15): 8467–8474. 11. Huynh, K.A. and K.L. Chen (2011). Aggregation Kinetics of Citrate and Polyvinylpyrrolidone Coated Silver Nanoparticles in Monovalent and Divalent Electrolyte Solutions. Environmental Science and Technology, 45 (13): 5564–5571.
9
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September 7, 2012
12. Griffitt, R.J., et al. (2008). Effects of Particle Composition and Species on Toxicity of Metallic Nanomaterials in Aquatic Organisms. Environmental Toxicology and Chemistry, 27 (9): 1972–1978. 13. Judy, J.D., et al. (2011). Evidence for Biomagnification of Gold. Environmental Science and Technology, 45 (2): 776–781. 14. Geranio, L, M. Heuberger and B. Nowack (2009). The Behavior of Silver Nanotextiles during Washing. Environmental Science and Technology, 2009, 43 (21), pp. 8113–8118. 15. Kemikalieinspektionen (KEMI) (2011). Antibacterial substances leaking from the clothes by washing. The analysis of silver triclosan and triclocarban in textiles before and after washing. Sweden, Swedish Chemicals Agency. 16. BACWA (2012). Comment letter on PHMB Registration Review (Docket ID No. EPA– HQ–OPP–2012-0341). 17. Gottschalk, F. et al. (2010). Possibilities and Limitations of Modeling Environmental Exposure to Engineered Nanomaterials by Probabilistic Material Flow Analysis. Environmental Toxicology & Chemistry, 29(5): 1036–1048. 18. WERF (2010). Impact of Silver Nanoparticles on Wastewater Treatment. 19. Choi, O., K. K. Deng, et al. (2008). "The inhibitory effects of silver nanoparticles, silver ions, and silver chloride colloids on microbial growth." Water Research 42(12): 30663074. 20. Choi, O. and Z. Hu (2008). "Size dependent and reactive oxygen species related nanosilver toxicity to nitrifying bacteria." Environmental Science & Technology 42(12): 4583-4588. 21. Benn, T. M. and P. Westerhoff (2008). Nanoparticle silver released into water from commercially available sock fabrics. Environmental Science & Technology, 42(11): 4133-4139. 22. Kiser, M. A., P. Westerhoff, et al. (2009). Titanium Nanomaterial Removal and Release from Wastewater Treatment Plants. Environmental Science & Technology, 43(17): 67576763. 23. Gottschalk, F., T. Sonderer, et al. (2009). Modeled environmental concentrations of engineered nanomaterials (TiO(2), ZnO, Ag, CNT, Fullerenes) for different regions. Environmental Science & Technology 43(24): 9216-9222. 24. Borkow, G., and J. Gabbay (2004). Putting copper into action: copper impregnated products with potent biocidal activities. FASEB Journal 18: 1728-1730. cc: Steve Bradbury, Director, U.S. EPA Office of Pesticide Programs Jed Costanza, U.S. EPA U.S. EPA Office of Pesticide Programs, Antimicrobials Division Joan Harrigan-Farelly, Director, U.S. EPA U.S. EPA Office of Pesticide Programs, Antimicrobials Division Lance Wormell, U.S. EPA Office of Pesticide Programs, Regulatory Management Branch II Mark Hartman, Branch Chief, U.S. EPA Office of Pesticide Programs, Regulatory Management Branch II Philip Ross, U.S. EPA Office of General Counsel Amber Aranda, U.S. EPA Office of General Counsel Sriniva Gowda, U.S. EPA Office of Pesticide Programs, Risk Assessment and Science Support Branch
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Nader Elkassabany, Branch Chief, U.S. EPA Office of Pesticide Programs, Risk Assessment and Science Support Branch Kirk Scheckel, US EPA National Risk Management Research Laboratory Land Remediation and Pollution Control Division Rick P. Keigwin, Jr., U.S. EPA Office of Pesticide Programs, Pesticide Re-Evaluation Division Betsy Southerland, Director, U.S. EPA Office of Water, Office of Science and Technology Randy Hill, Acting Director, U.S. EPA Office of Water, Office of Wastewater Management Nancy Woo, Acting Director, Water Division, U.S. EPA Region 9 Debra Denton, U.S. EPA Region 9 Patti TenBrook, Life Scientist, U.S. EPA Region 9 Syed Ali, California State Water Resources Control Board Tom Mumley, California Regional Water Quality Control Board, San Francisco Bay Region Janet O'Hara, California Regional Water Quality Control Board, San Francisco Bay Region Daniel McClure, California Regional Water Quality Control Board, Central Valley Region Tessa Fojut, California Regional Water Quality Control Board, Central Valley Region Marylou Verder-Carlos, California Department of Pesticide Regulation Nan Singhasemanon, California Department of Pesticide Regulation Kelly D. Moran, Urban Pesticides Pollution Prevention Project Greg Kester, California Association of Sanitation Agencies Chris Hornback, Senior Director, Regulatory Affairs, National Association of Clean Water Agencies
11
Nanosilver Product Wastewater-Related Environmental Exposures Product Silver Algaedyn
Use Swimming pool algaecide
ASAP-AGX and ASAP AGX-32
Hard surface disinfectant, controls odor-causing bacteria in dental water lines and bacteriostat
H2PRO
Controls odor causing bacteria in dental water lines Preservative in a wide variety of commercial and consumer products
Additive SSB
HeiQ AGS-20 and HeiQ AGS20U
Materials preservative for household textiles, apparel, and outdoor fabrics
Exposure Scenarios Swimming pools are emptied for maintenance about once every 2-7 years on average. In cold areas, pools are partially emptied each fall to prevent damage from freezing. When the pool is emptied, the nanosilver flows out along with the water. Pool water may be discharged to the sewer system (where it flows to a municipal wastewater treatment plant), to a gutter (where it flows to a storm drain) or into landscaping (which may include food-growing gardens).
Filter backwashing occurs regularly. Nanosilver may be discharged to sewers or storm drains from filter backwashing. Cleaning preserved materials transfers nanosilver to cleaning water and cleaning materials (sponges, mops, cloths) that are subsequently washed. Dental water line discharges, cleaning water and water from washing sponges, mops, and cloths are discharged to sewers, where the water flows to municipal wastewater treatment plants. Dental water lines discharge to sewers, where water flows to municipal wastewater treatment plants. Cleaning preserved materials transfers nanosilver to cleaning water and cleaning materials (sponges, mops, cloths) that are subsequently washed. Cleaning water and water from washing sponges, mops, and cloths are discharged to sewers, where it flows to municipal wastewater treatment plants. Leaches out of fabrics when washed. Washing machines discharge to sewers, where water flows to municipal wastewater treatment plants.
Environmental exposure pathways: Nanosilver particles (and any silver degradation products) may be transferred to biosolids (sewage sludge), effluent, or recycled water. Municipal wastewater treatment plant effluent flows into rivers, estuaries, or the ocean. In some cases, it may pass through freshwater or saltwater wetlands in the
final phase of treatment or upon discharge. Rivers receiving wastewater discharges may be sources of drinking water. Biosolids (sewage sludge) may be landfilled, incinerated (generating waste ash), or further treated prior to use as fertilizer in agriculture or urban gardens.
Recycled water may be used for irrigation, toilet flushing, groundwater recharge, or even as an input to drinking water systems.
It is unclear how the particle coating affects the fate of nanosilver that is transported in particle form.
Comparison of Nanosilver and Bifenthrin Registration Review Environmental Risk Documents Bifenthrin Nanosilver
Topic Purpose Review of available data Statement of ecological risk hypothesis Plan for risk evaluation and characterization Stressor source and distribution Summary of environmental chemistry data Description of mechanism of action Overview of pesticide usage Overview of pesticide use patterns Environmental fate & transport Receptors Aquatic and terrestrial effects data summary Identification of ecosystems potentially at risk Conceptual model Risk hypothesis Conceptual model diagram Analysis plan Stressors of concern Measures of exposure Measures of effect Integration of exposure and effects Assessment methods Preliminary identification of data gaps Data Request Data request justification tables Readability Summary Table of contents Document text can be searched
X X X X X X X X X X
X (HeiQ AGS-20 only) X X (HeiQ AGS-20 only)
X (HeiQ AGS-20 aquatic toxicity only)
X X X X X X X X X X X X
X (HeiQ AGS-20 only) X (HeiQ AGS-20 only)
