UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

December 13 , 2012

SUBJECT: Responses to the 60

-Day Public Comments on the Product Chemistry , Environmental Fate, and Ecological Effects Scoping Document in Support of Registration Review of Poly(hexamethylene

-biguanide) hydrochloride.

FROM:

THRU:

TO: PC Code: 111801 DP B arcodes: 405762 Decision Nos.: 459677 Registration Nos.: Petition No(s).: NA Regulatory Action: Response to 60- Day Public Comments Risk Assessment Type: Single Case No.: 3122 chemical TXRNo.:NA CAS No.: 32289

-58-0 /27083-27-8 MRID Nos.: None 40 CFR: None Najm Shamim, Ph.D. , Chemist

# ~i1a- 

# _**a/~ F~**  Srinivas Gowda, M

. S. Microbiologist 1 Pat Jennings , Environmental Engineer 

## rl**~ \1\..--~**  j r-· r -PDonna Randall, M.S., Senior Effects Scientist

### ~ 

## (/l/**~** Risk Assessment and Science Support Branch (RASSB) Antimicrobials Division (751 OP) Steven Weiss, Branch Chief

# ~**tt/~** Risk Assessment and Science Support Branch (RASSB) Antimicrobials Division (7510P) Rebecca von dem Hagen, Chemical Review Manager Regulatory Management Branch II Antimicrobials Division (751 OP) The Office ofPesticide Programs' Antimicrobial Division (AD) has reviewed the public comments received on the Poly(hexamethylenebiguanide) Registration Review, Case # 3122 (Docket ID Number EPA

- HQ

- OPP

- 2012

- 0341). Comments were received from the Bay Area Clean Water Agencies (BACWA); the California Stormwater Quality Association (CASQA); the Tri-TAC (the Technical Advisory Committee for the CASQA, the California Water Environment Association and the League ofCalifornia Cities); and the San Francisco Bay Water Qualit y
1Control Board (SFBWQB). Common comments from multiple submitters were compiled and summarized rather than provided verbatim.
1. 

### Comment: (BACWA, CASQA, SFBWQB, Tri-TAC) The PHMB risk assessment should evaluate sewer and stormwater exposure pathways for the swimming pool use. Discharge from pools to surface water from storm drains is a major pathway in pesticiderelated TMDL. 

### Agency's RespoJ se: The Agency has not previously assessed the potential for environmental exposures from the discharge oftreated swimming pool water. In most cases, pesticides used in pools for the purpose of disinfection are dissipated in the process ofproviding the Resticidal effect (e.g., chlorine-based treatments). However, for more persistent

### chemic~ls, such as PHMB, the Agency has determined that such an assessment should be included in the registration review assessment. A statement will be added to the FWP to clarify that the risk assessment will include evaluation ofdischarge from swimming pool use. 2. 

### Comment: (BACW A , CASQA, Tri-TAC) Enclosed informational materials that should assist EPA with development of a modeling scenario for swimming pools. 

### Agency's Response: The information enclosed on swimming pools will be reviewed and used to inform decisions on development of a modeling scenario for swimming pools.
3. 

### Comment: (BACW A, CASQA, SFBWQB, Tri-TAC) Urban storm drainage conveyance systems also have distinct physical characteristics that rapidly convey water and pollutants from use sites to receiving waters. To correctly evaluate the environmental risks ofPHMB released in swimming pool discharges, these discharges must be modeled as distinct events, rather than on the basis oflong-term averages. 

### Agency's Response: A scenario used to estimate environmental exposure concentrations from storm drain discharge will at a minimum consider peak exposure conditions.
4. 

### Comment: (BACWA, CASQA, SFBWQB , Tri

-TAC) The PHMB risk assessment should evaluate storm water exposure pathways for leaching ofPHMB from paints or coatings on exterior surface structures or facades. Submitted attachments providing results of laboratory and field studies on leaching ofbiocides from facades. 

### Agency's Response: The Agency appreciates the information documenting that use sites like walls on the exteriors ofbuilding treated with paints containing biocides like titanium dioxide and nanosilver could contaminate the storm drains and wastewater streams. The Agency agrees that PHMB use in exterior architectural paints and coatings can result in releases to surface water from leaching and wash offfrom rain, building wash water or irrigation overspray contacting these surfaces. A statement will be added to the FWP identifying that the risk assessment will include evaluation of leaching from use in architectural paints applied to facades and other exterior surfaces.

2

### 5. Comment: (BACW A, Tri

-TAC) Other PHMB uses listed in the Summary Document that should be incorporated into Down

-The

-Drain modeling include surface sanitizers and disinfectants for residential, commercial, hospital, veterinary and industrial settings; janitorial products for wet mopping; impregnated sponges; fabric treatments; and cleaning products for pet kennel and sleeping quarters. 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. Janitorial and other cleaning products often are concentrates that require mixing with water. Lefto er portions ofcleaners are commonly poured down drains. Impregnated sponges and fabric washing will inherently result in discharges to wastewater treatment facilities. Agency's Response: The Agency agrees that the modeling plan for PHMB should be amended to include discharges to wastewater treatment plants from PHMB uses, including but not limited to: swimming pools and spas (as discussed in Response #1); surface sanitizers and disinfectants for residential, commercial, hospital, veterinary and industrial settings; janitorial products for wet mopping; impregnated sponges; fabric treatments ; and cleaning products for pet kennel and sleeping quarters. The AD will examine these uses in the ecological risk assessment for PHMB. 

### 6. Comment: (BAOWA, Tri-TAC) EPA also needs to modify the modeling scenarios listed in the Scoping document (pp. 20-21) to account for releases ofPHMB not only during product formulation, but also during product use. For example, the OECD Emission Scenario Documents on Coatings (No. 20) and Adhesives (No. 22) provide only for emissions during product formulation

. However, certain product uses, such as caulking in shower stalls , could also release PHMB to wastewater treatment plants. Agency's Response: The Agency agrees that the modeling scenarios listed in the scoping document should account for both releases ofPHMB during product formulation and during in

-service rse ofthe product. The Agency is working to develop conceptual models for formulation and in

-service use of antimicrobial pesticides that will identify all potential pathways ofexposure to environmental media and to develop exposure scenarios for those exposure pathways that are determined to be ofpotential concern. 

### 7. Comment: (BACWA, Tri-TAC) Would like to learn more about the cooling tower scenario to be used for PHMB. On the basis ofthe reference provided in the docket, we are uncertain whether the cooling tower use scenario reasonably accounts for likely PHMB discharges from cooling water systems into municipal wastewa ter treatment plants. Municipal wastewater treatment plants receive cooling water discharges not only from power plants, but also from industrial facilities, office complexes, and even large commercial and residential buildings , all ofwhich commonly have water

-based cooling systems. Our past experience with tributyltin cooling water additives taught us that for some biocides , eJ en one or two users among dozens or hundreds ofcooling towers in our service areas can challenge our ability to comply with our NPDES permits.

3Agency's Response: The Agency is developing scenarios for recirculating and oncethrough cooling towers and will be making these publicly available once a thorough review is completed

. The scenario for recirculating cooling towers is adapted from Generic Scenarios developed by the Chemical Engineering Branch of EPA/OCSPP/OPPT. The approach for the once-through cooling tower scenario will employ the probabilistic dilution model (PDM) option ofthe General Population and Ecological Exposures from Industrial Releases Module ofEPA/OPPT's Exposure and Fate Assessment Screeing Tool (E

-FAST) to determine the number ofdays of exceedance ofconcentrations ofconcern (COCs) for species selected to represent freshwater fish, freshwater invertebrates and aquatic plants would be exceeded downstream offacilities with once-through cooling tower uses, such as steam electric power plants. 

### 8. Comment: (BAd w A, CASQA, SFBWQB, Tri

-TAC) The work plan should be refined by incorporating specific problem formulations, risk hypotheses, conceptual models and analysis plans similar to those that appear in most Environmental Fate & Effects Division (EFED) environmental assessment work plans. Agency's Response: The Agency agrees that a key purpose ofwork plans for antimicrobial pesticides undergoing registration review is to complete the problem formulation phase ofthe risk assessment process which is described in chapter 3 ofthe Agency's "Guidelines for Ecological Risk Assessment" (EPA/630/R

-95/002F)

. The Antimicrobials Division (AD) also believes that additional refinements to future work plans such as conceptual models and analysis plans similar to those tha t appear in most EFED environmental assessment work plans would help provide clarit y to the public on the environmental risk assessments AD plans to perform. Beginning with the work plan for

### para-tertiary amylphenol, which was published earlier this year, the AD changed the format and scope oftheir work plans and began incorporating the key elements ofthe problem formulation phase ofecological risk assessment 

### (i.e. , selecting assessment endpoints, developing conceptual models, and preparing an analysis plan) into this and all future work plans for antimicrobial pesticides undergoing registration review. The work plan for PHMB preceded this change and these changes will not be made to historic work plans which includes the existing PHMB work plan

. 

### 9. Comment: (BACWA, CASQA, SFBWQB, Tri

-TAC) Disagree with the Agency's proposal to waive acute and chronic toxicity tests for estuarine and marine species. These data are necessary because the use offreshwater species data to estimate effects on marine/estuarine species in an acute-to-chronic ratio (ACR) approach is not scientifically justified. In fact, this approach is not approved by EPA

- the EPA OW doe s not allow fresh water ACRs to be used in the development of salt water quality criteria. Finally, available aquatic toxicity data are insufficient to justify extrapolating data f rom freshwater species to marine/estuarine species

. Agency's Response: The PHMB wor k plan does not waive acute toxicity data for estuarine /marine species. In the PHMB environmental fate and effects scoping document and work plan acute data is required for an estuarine /marine fish, shrimp, and mollusk

4species for both TGAis. Regarding the OW not using ACRs derived from freshwater species to calculate chronic values for saltwater species the OW guidance for development ofnational criteria1

, which is Appendix H ofthe Water Quality Standards Handbook cited by commentors, states: "

...Even though absolute toxicities might be different in fresh and salt waters, such relative data as acute-chronic ratios and bioconcentration factors often appear to be similar in the two waters. When data are available to indicate tha t these ratios and factors are probably similar, they are used interchangeably

..." (page 7 ofthe criteria development guideline) and the guidance for calculation of an ACR for use in deriving a saltwater chronic value provides for two ofthe three required ACRs being from freshwater species (page 13 ofthe criteria developm ah ent guideline). The Agency does recognize, that given PHMB does not have a structural alog to verify that ACRs for freshwater and saltwater species in this case will not differ, at least one chronic saltwater study with the more sensitive estuarine /marine acute fish or shrimp will be required to provide confirmation. The need for an additional saltwater ACR in this case would be a higher tier requirement and is only needed if findings indicate that ACRs for freshwater and saltwater differ. 10. Comment: (BACWA, CASQA, SFBWQB, Tri-TAC) Registrants should be required to develop environmental chemistry analysis methods. The analytical methods for commodity residue measurements that registrants are required to develop lack sufficient analytic sensitivity to evaluate pesticides at environmentally relevant concentrations for environmentally relevant matrices , such as water column, sediment, wastewater effluent and biosolids. Such analytical methods exist for very few pesticides. Surface water quality monitoring programs , which include surveillance monitoring conducted by state and federal agen9ies , and compliance monitoring conducted by local agencies subject to NPDES stormwater and wastewater permits, need analytical methods for pesticides with sufficiently low detection limits that are practicable in commercial and government analytical laboratories. Where such methods do not exist, public agencies sometimes are forced to develop them at public expense. We believe it is more efficient and equitable for the manufacturer to develop these methods at the time ofinitial registration ofits product. We request that EPA adopt the approach used by the DPR to specify pesticide analysis method development during the registration review process. Agency's Response: For environmental fate and effects assessments the Agency requests registrants to provide chemistry analysis methods that meet the data quality objectives of the laboratory study or field study for which the analytical method is needed. Additionally environmental chemistry methods used to generate data associated with a field or monitoring study must include results of a successful confirmatory method trial by an independent laboratory

. At this time the Agency is not planning to ask registrants to develop additional laboratory analytical methods not connected with conduct of studies supporting the risk assessment.

1 http: //water

.epa.gov/scitech /swguidance /standards/criteria/aglife/upload/85guidelines

.pdf
5

### 11. Comment: (BAOWA, CASQA, SFBWQB, Tri

-TAC) Monitoring data would be invaluable for registration review, and we urge EPA to require registrants to conduct monitoring for their products in the environment, particularly in urban creeks and municipal wastewater. California DPR has required registrants to conduct a one-time survey ofthe concentrations ofeight pesticides (not including PHMB) in wastewater influent, effluent and biosolids. EPA should issue similar requirements for other pesticides where water monitoring data are lacking. 

### Agency's Response: Monitoring is a higher tier refinement for a risk assessment and such studies are required where information is needed to address a specific risk concern that cannot be answered using information from a lower tier study or model and/or to reduce uncertainty for the decision being made. This approach ensures that the data quality objectivd and resultant study design of such a monitoring study including type and number oflocations, media to be monitored, and frequency ofmonitoring provide robust information for the intended use ofthe data in the risk assessment. At this time, the Agency believes the data requested, which does not include any environmental monitoring, will provide a robust risk assessment. Ifat the conclusion ofthe risk assessment decision makers identify that the uncertainties for uses rise to a level of needing refinement to address label changes or mitigation the decision to require monitoring may be reconsidered at that time. 

### 12. Comment: (BAQWA, SFBWQB, Tri

-TAC) We request that documents for PHMB registration revief be modified to indicate OPP's intent to work with OW and a timeline by which it will utilize the outcomes ofthe common effects assessment methodology project. 

### Agency's Response: Currently the Agency does not have a fixed timeframe but are actively working with OW and ORD on follow

-up actions that will advance the harmonized methodologies discussed at the SAP. The Agency's web page www.epa.gov/oppefedl /cwa fifra effects methodology/scope.html will be updated as the effort progresses. A statement addressing this effort will be added to the scoping document. 

### 13. Comment: (BACWA, SFBWQB, Tri

-TAC) Modeling Average Periods: To facilitate integration with OW regulatory programs, we request that the work plan be modified to provide exposure estimates for time periods consistent with those used by OW, in addition to the time periods ordinarily used by OPP. 

### Agency's Response: The Agency has agreed to harmonize with the OW in regard to utilizing a common database for the purpose ofderiving effects endpoints for pesticides. AD continues to evaluate exposure and risk quotients consistent with the following documents: USEPA. 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum, Office ofResearch and Development, Washing, D .C. EPA/630/R-95/002F. April1998

. http: //cfuub.epa.gov/ncea/cfm/recorddisplay.cfm?deid=30759

6USEPA, 2004. Overview ofthe Ecological Risk Assessment Process in the Office of Pesticide

### Progr~s**.** U.S

. Environmental Protection Agency, Office ofPrevention, Pesticides and Toxic Substances, Office ofPesticide Programs, Washington, D.C. January 23, 2004 

### 1 14. Comment: (BAGWA, SFBWQB, Tri-TAC) We encourage EPA to use DPR sales data for PHMB,

### whic~ indicate that over 35,000 pounds ofPHMB were sold in 2010. These data are more

### use~l than pesticide reporting data, because most PHMB products are used by entities (residents and pool maintenance companies) that are not required to report pesticide usage. 

### Agency's Response: The Agency agrees that when sales data for a pesticide are available, these should be used whenever they are available to prevent underestimates of pesticides that may potentially be released to the environment. Some states, however, do not have sales data available for all their registered pesticides and the best available data on amounts used · n those states must be used in lieu of sales data. 

### 15. Comment: (BACWA, Tri-TAC) Because data in the supplemental studies cited (Scoping Document, pp. 10-11) indicate that PHMB poses a threat to the treatment process, we request that EPA seek to obtain all data necessary to complete a careful review of PHMB's potentia;l impacts on wastewater facilities and their critical microorganisms. Based on EPA's description ofthe sludge respiration inhibition test from the 1970s as being "supplemental", we are not confident that EPA has the information necessary for a thorough quantitative risk assessment. IfEPA has any scientific questions about the supplemental study's estimate that sludge respiration is not inhibited at PHMB concentrations less than 40 mg/L, we request that EPA require a sludge respiration inhibition test (EPA OPPTS Guideline 850.6800). 

### Agency's Response: The Agency agrees with the commenter that an Activated Sludge Respiration Inhibition (ASRI) test should be conducted following current Agency guidelines (OECD 209, OCSPP 850.3300). Upon reexamination ofthe 1970s study the Agency has concluded that this study which was characterized as supplemental does not provide adequate information that can be used to ascertain a dose-response curve ofthe relationship between concentration ofPHMB and respiration inhibition effects to activated sludge microorganisms. Although a quantitative assessment ofrisks to activated sludge microorganisms is not currently within the scope ofecological risk assessments for antimicrobial pesticides, consideration ofpotential adverse effects to wastewater treatment plant microorganisms is included in conceptual models. An important application ofinformation that can be obtained from a dose-response curve of the relationship between concentration ofPHMB and respiration inhibition effects to activated sludge microorganisms exposed to PHMB is discussed in the Agency response to comment 17. 1

7In conclusion, the Agency will require an ASRI test to be performed according to either OECD 209 or OCSPP 850.3300 and will include this additional data requirement in the final work plan for PHMB. 16. Comment: (BACW A, Tri

-TAC) Encourage EPA to consider available open literature, if any, to assess the potential for wastewater treatment process interference. Agency's Response: To assess the potential for wastewater treatment process interference, the Agency uses results from an acceptable ASRI test performed according to OECD 209 or OCSPP 850.3300 guidelines. An ASRI test performed according to these guidelines would be expected to provide results that would be adequate to develop a dose

-response relationship between concentration ofPHMB and respiration inhibition effects to activated sludge microorganisms exposed to PHMB. In the absence of an acceptable ASRI test, the Agency would review open literature for information on the potential for wastewater treatment plant interference as a result ofPHMB entering wastewater treatment plants. 17. Comment: (BACWA, Tri

-TAC) In designing its process interference risk assessment, EPA should use a quantitative approach. Quantification ofrisks will provide the basis for future risk management. Wastewater facility operators would benefit from specific guidance on how to calculate how much PHMB-containing pool water may be safely discharged to a wastewater collection system each day. This would ideally be a "maximum allowable headworks loading" formula that would provide a simple formula to calculate the maximum daily quantity ofPHMB

-containing pool water that can be discharged while protecting the treatment facility microorganisms and preventing interference with the treatment process. Agency's Response: Using the dose

-response curve from an Activated Sludge Respiration Inhi9ition Study (ASRI) study, plant operators can select a respiration inhibition percent that would be considered to be an upper bound that would be adequately protective to prevent interference with the treatment process and determine from this plot a corresponding concentration ofPHMB that must not be exceeded. This concentration along with wastewater trea tment plant influent flow data can be used as the basis ofa formula to calculate the maximum daily amount ofPHMB

-containing pool water that can be discharged while protecting the activated sludge microorganisms and preventing interference with the treatment process. The Agency is planning to provide guidance on performing such calculations

. 18. Comment: (BACWA, Tri-TAC) With approximately fifty percent ofwastewater treatment costs allocated to biosolids handling, there is particular concern that pesticide residues in biosolids may impact biosolids management options, especially land application to agricultural areas. Therefore, we urge the OPP, Water (Offices of Wastewater Management and Science and Technology), and Research and Development to work together to develop a methodology that evaluates potential impacts ofpesticides to biosolids land application whenever Down-The-Drain assessments indicate that pesticides would partition into biosolids.



### 8

### Agency's Response: An Intra

-Agency Biosolids Workgroup was convened in early 2012. This workgroup includes members from OPP, and OW Offices ofWastewater Management and Science and Technology who are working in consultation with members ofEPA's Office ofResearch and Development. Two key purposes ofthis workgroup are to develop criteria for determining whether a pesticide that is released down

-the-drain might have the potential to partition to biosolids and subsequently lead to exposures ofpotential concern to humans and ecological organisms from land

-application ofbiosolids and to develop a screening

-level model that can be used to estimate potential exposures ofhumans and ecological organisms to chemical substances in biosolids that are land applied. 

### 19. Comment: (BACWA, Tri

-TAC) It should be noted that such evaluations (i.e., of potential impacts ofpesticides to biosolids land application whenever Down-the

-Drain assessments indicate that pesticides would partition into biosolids (refer to topic introduced in Comment 18)) should focus on fate, transport, and toxicity factors specifically applicable to the biosolids matrix. The existing OPP guidelines for the study ofchemicals 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. 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 850.31 00). 

### Agency's Res onse: Assessing toxicity to microbes and worms is generally not within the scope ofthe Agency's current risk assessment methodologies. For instance, in the current version ofthe Biosolids Core Risk Assessment Model (BCRAM) developed by EPA's Office ofWater, pathways ofecological exposure to chemicals in biosolids that are considered include contact with water, soil, and sediment and ingestion of contaminated aquatic and terrestrial species. Although uptake ofchemicals in biosolids by the soil invertebrate community as a result ofcontact with soil is considered, this methodology does not consider toxicity to microbes and worms. In addition, assessment oftoxicity to microbes and worms is not within the scope of ecological risk assessment for conventiona l pesticides. Although the Agency occasionally receives data on toxicity to earthworms, the Agency does not require such data and does not quantitatively assess risk based on this information. The Agency does , however, use this information in characterizing risks to conventional pesticides.
At this time , the Agency has no plans to require registrants to conduct studies such as a soil microbial community toxicity test (OPPTS Guideline 850.3200) or an earthworm subchronic toxicity test (OPPTS Guideline 850.31 00). 

### 20. Comment: (BACWA, Tri-TAC) Supports the AD's intention to estimate environmental concentra tions from wastewater discharges using theE

-FAST model's Down

-The

-Drain module

. However, there are concerns with the way that E-F AST has been set up and used



### 9by OPP. Support OPP's previously stated plan to work with EPA's Office ofWater and stakeholders to refine the way E-F AST is used. Agency's Response: To obtain the full context ofthis comment, the Antimicrobials Division reviewed the comment, "Publicly Owned Treatment Works (POTW) Removal Efficiency and Improvements ofMethodology About EFAST2" presented in the memorandum, "Response to Public Comments on the EFED Registration Review Problem Formulation for Bifenthrin" dated December 22,2010 (EPA

-HQ-OPP-2010- 0384

-0034). The approach that the AD presented in its work plan and plans to use in its ecological risk assessment for PHMB is not the same as that EFED presented in problem formulations for conventional pesticides, such as bifenthrin. Bifenthrin belongs to a class of chemicals, synthetic pyrethroids, which have been detected in surface waters, aquatic sediments, and biosolids throughout the United States

. Consequently, the approach for problem formulation EFED proposed for bifenthrin is designed for a higher tier exposure and risk assessment than the approach for problem formulation for PHMB, which is designed for a screening level exposure and risk assessment. For antimicrobial pesticides that have uses and environmental fate characteristics that may result in releases to domestic wastewater treatment plants, AD performs a screening

-level assessment using the Down

-the

-Drain module ofE

-FAST to determine potential concerns for exposure of aquatic organisms to an antimicrobial pesticide and/or its degradates. When results from this screening level aquatic exposure and risk assessment indicate a potential concern for aquatic organisms exposed to an antimicrobial pesticide and/or its degradates downstream ofdomestic WWTPs, AD requires data on antimicrobial pesticides and/or their degradates that will provide information on potential removal ofpesticide during wastewater treatment, toxicity to activated sludge microorganisms, and acute and measurement endpoints for aquatic organisms

. Wastewater treatment plant studies may include:

• Activated Sludge Respiration Inhibition (ASRI, OECD 209) or Modified ASRI test (850

.3300); • Ready biodegradability (GLN 835.3110), or Porous Pot Test (GLN 835.3220), or Simulation Tests to Assess the Biodegradability ofChemicals Discharged to Wastewater (GLN 835.3280), or Simulation Test- Aerobic Sewage Treatment: A. Activated Sludge Units (GLN 835.3240) • Activated Sludge Sorption Isotherm (GLN 835.1110) The results ofthe Activated Sludge Respiration Inhibition Test (ASRI) determine which ofthese biodegradation tests are required. Ifthe ASRI test EC 5

### o is less than or equal to 20 mg/L, then either the Biodegradation in Activated Sludge Study or the Porous Pot Test is required

. Ifthe ASRI test EC 50 is greater than 20 mg/L, then the applicant must choose either: (i) Ready Biodegradability or (ii) Biodegradation in Activated Sludge or the Porous Pot Test. Ifthe antimicrobial passes the ready biodegradability study, then no further testing is required. If, however, the antimicrobial fails the ready biodegradability study, then the Biodegradation in Activated Sludge or the Porous Pot study is required.
10Data from these tests would then be used to refine the screening level exposure and risk assessment. The AD is working to develop a tiered approach for using E

-FAST to assess exposures and risks to ecological organisms and to develop a plan to distribute this approach for review and comment.

11