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

PC Code: 114801 DP Code: 405055 September 14, 2012

MEMORANDUM Subject:

From:

Through:

To: Methyloxazolidines Environmental Effects and Fate Registration Review Scoping Document-Office of Pesticide Program's Response to Publ ic Comme nts Zoe Layton, Biologist 

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# ·**~-du-L?** James Breithaupt,

### Agron~isG**~~** _ PatJenn ings, Environmental Engine

# ~o.X~ Risk Assessment and Sci ence Support Branch (RASSB) Antimicrobials Division (7510P) Steven Weiss, Acting Branch Chief 

# st'(,flY Donna Randall , Ecological Risk Assessment Team Leader Risk Assessment and Science Suppo rt Branch (RASSB) Antimicrobials Division (7510P) Seiichi Murasaki , Chemica l Rev iew M anager Regulatory Management Branch II Antimicrobials Division (7510P)

Page 1 of 7This document contains the Risk Assessment and Science Support Branch's (RASSB's) responses to publ ic comments received on the Environmental Effects and Fate Registration Review Scoping Document for methyloxazolidines, specifically d imethy loxazolid ine (DMO). EPA received comments from two parties, The Dow Chemical Company (Dow) and Troy Corporation (Troy), during the public comment period. This document contains responses only to those comments submitted related to the ecological risk assessment. Additionally, the comments may be paraphrased rather than provided 

### verbatim. 1. Comment (Dow and Troy) : Dow and Troy requested that the Ag ency reconsider the request for additional ecological effects and environmental fate data on the degradates of DMO based on the rapid hydrolysis of DMO to 2-a mino-2-methyl -1- propanol (AMP) i n wate r at pH 5, 7, and 9. Agency Response: The Agency acknowledges that DMO is kn own to be hydrolytically unstable and to rapidly degrade to AMP. It is because of this instabi l ity, that the Agency is concerned with AMP and will use studies on this degradate to conduct a thorough risk assessment. In several of the studies submitted to the Agency, due to this known property of the test substance to rapidly degrade in water, the study author stated that the high treatment leve l was not analyzed for the parent substance, however all data were reported in terms of DMO. Further clarification of the methodology and AMP conce ntrations , if AMP was measured, is necessary before upg ra d ing the following studies:
• 850.1400 Fish early life stage toxicity test (freshwater) (AMP)
• 850.1010 Aquatic inverte brate acute toxici ty, freshwater daphnids (AMP)
• 850.1075 Fish acute toxicity (marine/estuarine) (AMP)
• 850.4500 Algal Toxicity Tier II (AMP)--marine diatom 1 Additionally, if the registrants believe , based on scientific evidence, that any studies co nducted with DMO are "essentially equivalent" to studies which wo uld be conducted with AMP, and that the AMP exposure concentration would be stable, the methodo logy and results of these f in dings need to be documented and provided to this agency. Th is includes the methodology of converting DMO to AMP, if applicable, or the measured concentrations reported in AMP, rather than DMO. Providing this documentation cou ld potentially satisfy the request for any equivalent studies co nducted with AMP, including :
• 850.2100 Avian acute oral toxicity test (AMP)
• 850.1075 F ish acute toxicity (freshwater) (AMP)
• 850.1025 Oyster Shell Deposition study (AMP) 2. Comment (Dow) : "An acute mysi d test has been identi fied as a data gap, but the data generated from an acute test with the marine copepod, 

### Acartia tonsa is more conservative as this copepod is very sensitive. This study is available and will be submitted to the Agency."

1 Since the opening ofthis docket, the Agency has posted the availab ility ofFinal Algal Toxicity gu idelines
. The Public 850.5400 guideline has been split and renumbered as 850.4500 Algal Toxicity and 850.4550 Cyanobacteria 

### (Anabaenajlos-aquae). http: //www.epa.gov/ocspp /pubs/frs/publications/Test Guidelines/series850.htm

Page 2 

### of 7

### Agency Response: The Agency will review this acute cope pod toxic ity test once it is received, against acute testing protocols and standards for this species and determine if it provides an acceptable acute LC 50 value and information on the co nce ntration - response re lationship. If the study is found acceptable and it is the lowest acute i nvertebrate value, the Agency would use the study i n the risk assessment in place of the mys id shrimp acute study
. The Agency uses t he most sensitive estuarine/marine acute invertebrate toxicity value to assess acute ri sks to estuarine/marine inverteb rates. Because i t is not possible to test all estuarine/marine invertebrate species the Agency uses ind icator species for perfo rmi ng risk assessments for pesticides
. The species for estuarine/marine invertebrates includes a mollusk species and a shrimp speci es, either from the Mysidae fami ly or the Penaeidae fami ly. Because there may be a need in h igher tier testi ng for a fu ll life cycle test and establishment of an acute-to chronic rat io, the species typically tested of these two shri mp families for pesticides is the mysid (Americamysis bahia}. An examinat ion of the data that has been submitted i nto OPP for A. tonsa shows only two cases where both A. tonsa and mysid data were ava il able. One result had A. tonsa being more sensitive by a ratio of 2 whereas in the other case the mysid was more sensitive by a ra t io of >10. The Agency's interspecies corre lat ion program Web- ICE 2
, while containing data for A. bahia, does not include any data for A. tonsa by which the relative sensitivity of these two species can be evaluated, especially fo r biocides. Without addition al data regarding the relative sensitivity of these two species and no mysid acute data, the Agency will assume that acute toxicity as determined using A. tonsa as compared to the mysid may underestimate acute effects to estuarin e/marine i nverteb rates. Additionally, another problem potentially a rises in regards to assess i ng ch ronic toxicity to estuarine/marine invertebrates. If the registrant bel i eves that A. tonsa is the more sensitive species, the Agency will need to either be able to extrapolate the chron ic toxici ty ofA. tonsa using another estuarine/marine i nvertebrate species acute-to-chronic ratio, for which none currently exists, or have an acceptab le life cycle toxicity study using A. tonsa i n place of the mysid life cycle toxicity test. But to reite rate without info rmati on on the relative sens i t ivity ofA. tonsa compared toA. bahia for AMP, there will be a co ncern that the use ofA. tonsa is potent ially underestimating chro nic risk as compared to the s

tandard indicator species , the mys id. One way of using A. tonsa data without this uncertainty wo uld be to provide an acute mysid test, to de mon strate thatA. tonsa is as sensit ive, or more sensitive, than the mysid. The registrant can then prov ide a l ife cycle test w ith A. tonsa w ith a waiver request for the requ ired mysid life cycle test based on provid i ng a more sensitive species life cycle test or alternatively provide a mysid life cycle test. W ith both acute and chronic life cycle test data for A. bahia an acute-to chronic ratio for the mysid can be calculated which can be applied to the A. tonsa acute data to estimate its chronic endpoint. If the mysid i s foun d to be more sensitive, no life cycle test o r extrapolation of a chron i c A. tonsa value would be needed for t he risk assessment, the assessment would be based on the submitted A. bahia acute and chronic data. The Agency will reta i n the need for both the acute and chronic mysid data but, as described above, the approach is f l exi ble and the indicator species data can be waived when alternative species data is provided which is as sens i t ive, or more sensit ive, than the indicator species. 

### 3. Comment(Dow): "No endpoint exi sts fo r an aquatic plant such as Lemna gibba, however three algal studies are ava i lable that should provide conservative data for this endpoint
." 

### Agency Response : The Agency uses the test results with duckweed , Lemna sp., as an indicator species for effects to floating aquatic rooted vascular p lants. Thi s test includes exposure pathways that non2 http://epa.gov /ceampubl/fchain/webice/ getPredSurr.html?tile=as Page 

### 3 of7vascular plants, like algae, do not possess. Algal species are not always more se nsitive to a substance t ha n the floating rooted vascular plant, Lemna spp. A study with a Lemna spp. is still needed. 4. 

### Comment (Dow): "Algal tier II testing has been identified as a data gap, howeve r, this algal tier II is not needed as th ree algal studies are available for DMO. These studies include two with the freshwater green algae, Pseudokirchneriella subcapitata (formerly known as Selenastrum subcapitata, and the freshwater (sic) diatom, Skeletonema costatum." 

### Agency Response: When aquatic environments will be exposed, the Agency uses a battery of four ind icato r non-vascular plants to eva l uate effects to primary productivity in estuarine/marine and freshwater systems. The Agency was provided w ith, and reviewed (as mentioned above in Agency Response to Comment 1), an algal toxicity tier II study with the marine diatom, Skeletonema costatum. No cyanobacterium study has been submitted. The two studies conducted with the freshwater green algae, Pseudokirchneriella subcapitata, mentioned in response to EPA-HQ-OPP-2012-0007 have also not been provided to the Age ncy at this time; therefore, the following studies are still required:
• 850.4500 Algal Toxicity Tier II (AMP) green algae, Pseudokirchneriel/a subcapitata 3
• 850.4550 Cyanobacteria (Anabaena /los-aquae) Tier II (AMP) 3 5. 

### Comment (Dow): The Agency was asked to reconsider the request for additional environmental ecotoxicity data for DMO degradates base d on the parent degrading to AMP, and the existing DMO and AMP toxicity data. All of the studies discussed in Comment #1 through #4 were identified for reconsidered in addition to the Daphnid chronic toxicity test (AMP), Mysid chronic toxicity test (AMP), and Seedling emergence Tie r II (AMP). 

### Agency Response: A ris k assessment conducted by the Agency includes consideration of the parent and its toxic degradates , not just the parent substance. Therefore, the instabi l ity of DMO does not negate the need for a risk assessment of DMO uses or its degradates. As indicated in the Agency's Response to Comment #1, it is because of DMO's instability, that the Agency is concerned with AMP in the environment and not DMO, and it will use studies on this degradate to conduct the risk assessment. The refore none of the studies are being recons i dered or eliminated on this basis. Additional reasons prov ided by submitters for the req uired studies to be dropped are in identified in Comment #1 through #4, along with the Agency's response . Additionally, the following studies have not been conducted on either the parent compound or the degradate, AMP, and remain necessary in order to conduct an ecological risk assessment (for the mysid chronic study see additional discussion in Agency Response to Comment #2):
• 850.1300 Daphn i d chronic toxicity test (AMP)
• 850.1055 Bivalve acute tox larva l (embryo-larval) (AMP)
• 850.1350 Mysid chronic tox- aquatic invertebrate lifecycle (saltwater) (AMP)

3 Since the opening ofthis docket, the Agency has posted the availability of Fina l Algal Toxicity guidelines
. The Public 850.5400 guideline has been split and renumbered as 850.4500 Algal Toxicity and 850.4550 Cyanobacteria 

### (Anabaenajlos-aquae)
. http: //www.epa.gov/ocspp/pubs/frs/publications/Test Guidelines/series850
.htm Page 

### 4 of7• 850.4225 Seedling emergence, Tier II (AMP) 6
. 

### Comment (Troy): "There is a considerab le amount of data req uested i n t he area of ecological toxicology
. Rather than awaiting the results of the initial acute stud ies all studies including chronic st ud ies are being req uested at this t i me. Lower tier studies such as acute studies should b e requested first, ana lyzed and then the need for higher tie r stud i es can be requested
. As an example Tier I algal tox icity data is requ i red as well as a Tier II a lga l toxicity study." 

### Agency Response: Under the allotted registration review schedule the Agency identifies all data necessary to conduct a risk assessment based on the state of knowledge in terms of both existing fate and effects data at the time of the work plan
. The l i sti ng of all data at one time does not prohibit the registrant from schedul i ng and conducting the required stud ies i n a tiered manner. If a fate or lower t ier effects study results in a higher t ier effects study not be i ng needed , a waiver request a long with the study results support in g that the h igher tier is not needed can be submitted in li eu of the higher tier data , the same as when a reg i stration package is provided fo r a new pesticide or a new use . However, the example of t i ering in regards fo r algal studies provided by Troy is not approp riate in this case . For convent ional agricultural use pesticides an arbitrary limit of 100 ppm has been set as an appropriate lim it i n most aquatic effects gu i del i nes based on experience of agricultu ral use rates, resultant exposure estimates , and an acceptab le safety factor4 ; for aquatic plants a l i m i t i s based on rates applied per acre which is not applicable for antimi crobial use applications. However, for a number of ant i microbia l use patterns whe re modeling of discharge levels to surface waters does not have a long history, t he body of know ledge and experience for establishing an acceptab le li mit to use in a Tier I test does not yet exist
. Note that even in the case of conventional agricultural chemicals, where use rates would result in h igher exposure than what the 100 ppm l i mit is based on (e.g., 1 00,000 times the expected high end exposure)4 e ither a higher l imit i s needed for the study to be acceptable or a Tier II (definitive endpoint) test is needed
. 7
. 

### Comment (Dow) Waivers for the Act ivated Sludge Sorption Isotherm ; Aerobic Aquat ic Metabo l ism; Anaerobic Aquatic Metabol ism (AMP); Ready Biodegradability; Porous Pot Test; Simulation Tests to Assess the Biodegradab i lity of Chemicals Discharged to Wastewater and S

i mulation Test -Ae rob ic Sewage Treatment: A. Activated Sludge Units studies are requested since "[
... ] both DMO an d AMP are readily biodegradable". An examination of the chem ica l st r ucture and a review of information in the Robust Summary for AMP, i ndicates that a high pe rcentage of AMP may be removed by convent ional sewage treatmen t systems. Specifically, the b iodegradation of AMP has been demonstrated in a laboratory ready biodegradability study to remove 89% of the bi ochemical oxygen demand (BOD) in 28 days under ae robi c conditions, us i ng no n-adapted domestic act ivated sludge inoculum (OECD Guideline test 301F)
. The primary removal mechanism was attributed to mineralizati o n . 

### Agency Response: All general environmental fate data requested in the March 16, 2012 memorandum are still requi red. Anaerobic aquat ic (OCSPP 835.4400) and aerobic aquat ic (OCSPP 835.4300) metaboli sm data for the degradate AMP cannot be waived because the only acceptable environmenta l fate data are hydrolys is and photodegradation i n water, which rep resent chemical degradation
.
4 Pesticide Assessment Guidelines S ubdivision E. Haza rd Evaluation : Wildlife and Aquatic Organis ms . Prepa red by Ecological Eff ects Branch, Haza rd Evaluation Divi sion, Offi ce of Pesticide Programs . EPA-540/9-82-024. (see page 18 for di scuss ion of development of cut
-off) http: //nepis
.epa.gov/ Page 5 of 7

### Hydrolysis rapidly forms AMP , but AMP is stable to both hydrolysis and photodegradation in water. Hydrolysis occurs too rapidly for photodegradation to occur . With the possible exception of the Activated Sludge Sorption Isotherm (OCSPP 835.1110), environmental fate studies for wastewater treatment for the degradate AMP are still required. Activated Sludge Sorption Isotherm (OCSPP 835.1110) can be waived if data are provided that demonstrate that the log Kow for AMP is less than 3.0, which would indicate limited potential for sorptio n . Ready Biodegradability (835.31 10) is still required even though the Robust Summary data, presented in a letter dated 8/28/2011 from t he Dow Chemical Company to Mark Townsend, Chief , HPV Chemicals Branch of EPA/OCSPP/OPPT, claim that 89% o f AMP degraded in 28 days in a Ready Biodeg radabil ity study (OECD 301F). As the Agency stated in the Scoping Document for Methyloxazoladines: "
...to be able to give merit to this claim, the Antimicrobials Division would need to review and evaluate the primary references cited in this letter to the Agency. Without reviewing and evaluating these primary references and reaching the same conclusions as those presented, the Agency ant icipates needing environmental fate data from tests including the activated sludge respiration inhibiti on (ASRI) test and depending on the outcome of the ASRI test , either a ready biodegradability test or one of the following simul ation tests : porous pot test, or simulation tests to assess the biodegradability of chemicals discharged in wastewater, or simulation testaerobic sludge treatment: A. Activated Sludge Units." Note that the simulation tests mentioned are conditionally required based on the res ults of the potential for AMP to be demonstrated to readily biodegrade. To reiterate, these si mulation tests and corresponding guideline numbers are the Porous Pot Test (OCSPP 835.3220); Simulation Tests to Assess the Biodegradability of Chemicals Discharged to Wastewater (OCSPP 835.3280); and Simulation TestAerobic Sewage Treatment : A
. Activated Sludge Units (OCSPP 835.3240) for AMP
. 8. Comment (Troy) : The Agency has raised concerns over DMO metabolites and before proceeding with requested studies Troy proposes the use of models such as EFAST o r PRIZM to assess the potential affect of these substances on drinking water and WWTP systems
. Agency Response: The Agency, as explained in the work plan, will use models such as E - FAST to assess the potential affects of these substances on drinking water and WWTP systems as part of the risk assessment. The conduct of the actual risk assessment is not part of the work plan. Additionally, the current status of the envi ronme ntal loa d ing from uses, environme nta l fate , and ecolog i ca l effects data to conduct such an assessment is incomplete at this time-hence the list of data needs. 9. Comments (Troy) : A major piece missing from the analysis of DMO and its metabolite formation is a simple hydrolysis study in an end use that is considered the worst case from an exposure point of view (e.g. metalworking fluid). This type of study was requested of other formaldehyde donor substances and provides a clear picture of the behavior of the substance under conditions of hydrolysis. Before proceeding with additional measurements of formaldehyde in a number of studies we would propose that this study be conducted first utilizing NMR analytical techniques to obtain a clear picture of the form at ion of formalde hyde under various hydrolytic pH conditions. Agency Response: For DMO, the Agency has no objection to the submission of hydrolysis data from End Use products under rea l-world use conditions to address metabolite formation and decline as a result of Page 6 of 7DMO application. These data clearly have the potential to refine any estimates of ecolog ica l and human health exposure and risk because they provide additional i nformation on which the Agency can base its decisions
. The hydro lysis data (OCSPP 835.2120) on the TGAI form of DMO are l im ited to chemical degradation because the test guideline requires sterility to isolate ind ivi dual routes of diss i pation (e.g
. chemica l degradation or microbial metabol i sm). However, data on End Use products do not take the p lace of aq uat ic metabolism studies (OCSPP 835.4300 and 835.4400) which simulate comb i ned chemical and microbial degradation i n surface water and bottom sediment. They also do not necessarily take the place of sewage treatment studies.

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