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 Comments 

Zoe Layton, Biologist tjy _/\\ ~ · ~-du-L? James Breithaupt, Agron~isG ~~ _ 

PatJennings, Environmental Engine ~o.X~ Risk Assessment and Science Support Branch (RASSB) 

Antimicrobials Division (7510P) 

Steven Weiss, Acting Branch Chief st' (,flY 

Donna Randall, Ecological Risk Assessment Team Leader 

Risk Assessment and Science Support Branch (RASSB) 

Antimicrobials Division (7510P) 

Seiichi Murasaki, Chemical Review Manager 

Regulatory Management Branch II 

Antimicrobials Division (7510P) 

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This document contains the Risk Assessment and Science Support Branch's (RASSB's) responses to public 

comments received on the Environmental Effects and Fate Registration Review Scoping Document for 

methyloxazolidines, specifically dimethyloxazolidine (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 Agency 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-amino-2-methyl-1-propanol (AMP) in water at pH 5, 7, and 9. 

Agency Response: The Agency acknowledges that DMO is known to be hydrolytically unstable and to 

rapidly degrade to AMP. It is because of this instability, 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 level was not analyzed for the parent substance, 

however all data were reported in terms of DMO. Further clarification of the methodology and AMP 

concentrations, if AMP was measured, is necessary before upgrading the following studies: 

• 850.1400 Fish early life stage toxicity test (freshwater) (AMP) 

• 850.1010 Aquatic invertebrate acute toxicity, freshwater daphnids (AMP) 

• 850.1075 Fish acute toxicity (marine/estuarine) (AMP) 

• 850.4500 Algal Toxicity Tier II (AMP)--marine diatom1 

Additionally, if the registrants believe, based on scientific evidence, that any studies conducted with 

DMO are "essentially equivalent" to studies which would be conducted with AMP, and that the AMP 

exposure concentration would be stable, the methodology and results of these findings need to be 

documented and provided to this agency. This includes the methodology of converting DMO to AMP, if 

applicable, or the measured concentrations reported in AMP, rather than DMO. Providing this 

documentation could potentially satisfy the request for any equivalent studies conducted with AMP, 

including: 

• 850.2100 Avian acute oral toxicity test (AMP) 

• 850.1075 Fish acute toxicity (freshwater) (AMP) 

• 850.1025 Oyster Shell Deposition study (AMP) 

2. Comment (Dow): "An acute mysid test has been identified 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 of this docket, the Agency has posted the availability of Final 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 

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Agency Response: The Agency will review this acute cope pod toxicity test once it is received, against 

acute testing protocols and standards for this species and determine if it provides an acceptable acute 

LC50 value and information on the concentration-response relationship. If the study is found acceptable 

and it is the lowest acute invertebrate value, the Agency would use the study in the risk assessment in 

place of the mysid shrimp acute study. The Agency uses t he most sensitive estuarine/marine acute 

invertebrate toxicity value to assess acute risks to estuarine/marine invertebrates. Because it is not 

possible to test all estuarine/marine invertebrate species the Agency uses indicator species for 

performing risk assessments for pesticides. The species for estuarine/marine invertebrates includes a 

mollusk species and a shrimp species, either from the Mysidae family or the Penaeidae family. Because 

there may be a need in higher tier testing for a full life cycle test and establishment of an acute-tochronic ratio, the species typically tested of these two shrimp families for pesticides is the mysid 

(Americamysis bahia}. An examination of the data that has been submitted into OPP for A. tonsa shows 

only two cases where both A. tonsa and mysid data were available. 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 rat io of >10. The 

Agency's interspecies correlation program Web-ICE2

, 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 for biocides. Without additional 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 estuarine/marine invertebrates. 

Additionally, another problem potentially arises in regards to assessing chronic toxicity to 

estuarine/marine invertebrates. If the registrant believes that A. tonsa is the more sensitive species, the 

Agency will need to either be able to extrapolate the chronic toxicity of A. tonsa using another 

estuarine/marine invertebrate species acute-to-chronic ratio, for which none currently exists, or have an 

acceptable life cycle toxicity study using A. tonsa in place of the mysid life cycle toxicity test. But to 

reiterate without information on the relative sensitivity of A. tonsa compared to A. bahia for AMP, there 

will be a concern that the use of A. tonsa is potentially underestimating chronic risk as compared to the 

standard indicator species, the mysid. One way of using A. tonsa data without this uncertainty would be 

to provide an acute mysid test, to demonstrate that A. tonsa is as sensitive, or more sensitive, than the 

mysid. The registrant can then provide a life cycle test w ith A. tonsa with a waiver request for the 

required mysid life cycle test based on providing a more sensitive species life cycle test or alternatively 

provide a mysid life cycle test. With both acute and chronic life cycle test data for A. bahia an acute-tochronic 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 is found to be more sensitive, no life cycle test or extrapolation of a 

chronic 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 retain the need for both the acute and 

chronic mysid data but, as described above, the approach is flexible and the indicator species data can 

be waived when alternative species data is provided which is as sensitive, or more sensitive, than the 

indicator species. 

3. Comment(Dow): "No endpoint exists for an aquatic plant such as Lemna gibba, however three 

algal studies are available 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 plants. This test includes exposure pathways that non2 http://epa.gov/ceampubl/fchain/webice/getPredSurr.html?tile=as 

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vascular plants, like algae, do not possess. Algal species are not always more sensitive to a substance 

t han 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, however, this algal tier II 

is not needed as three 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 

indicator non-vascular plants to evaluate 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 Agency at this time; therefore, the following studies are still required: 

• 850.4500 Algal Toxicity Tier II (AMP) green algae, Pseudokirchneriel/a subcapitata3 

• 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 based 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 Tier II (AMP). 

Agency Response: A risk assessment conducted by the Agency includes consideration of the parent and 

its toxic degradates, not just the parent substance. Therefore, the instability 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. 

Therefore none of the studies are being reconsidered or eliminated on this basis. Additional reasons 

provided by submitters for the required 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 Daphnid chronic toxicity test (AMP) 

• 850.1055 Bivalve acute tox larval (embryo-larval) (AMP) 

• 850.1350 Mysid chronic tox- aquatic invertebrate lifecycle (saltwater) (AMP) 

3 Since the opening of this docket, the Agency has posted the availability of Final 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 

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• 850.4225 Seedling emergence, Tier II (AMP) 

6. Comment (Troy): "There is a considerable amount of data requested in t he area of ecological 

toxicology. Rather than awaiting the results of the initial acute studies all studies including 

chronic studies are being requested at this t ime. Lower tier studies such as acute studies should 

be requested first, analyzed and then the need for higher tier studies can be requested. As an 

example Tier I algal toxicity data is required as well as a Tier II algal 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 listing of all data at one time does not 

prohibit the registrant from scheduling and conducting the required studies in a tiered manner. If a 

fate or lower t ier effects study results in a higher t ier effects study not being needed, a waiver 

request along with the study results supporting that the higher tier is not needed can be submitted 

in lieu of the higher tier data, the same as when a registration package is provided for a new 

pesticide or a new use. However, the example of tiering in regards for algal studies provided by Troy 

is not appropriate in this case. For conventional agricultural use pesticides an arbitrary limit of 100 

ppm has been set as an appropriate limit in most aquatic effects guidelines based on experience of 

agricultural use rates, resultant exposure estimates, and an acceptable safety factor4; for aquatic 

plants a limit is based on rates applied per acre which is not applicable for antimicrobial use 

applications. However, for a number of antimicrobial use patterns where modeling of discharge 

levels to surface waters does not have a long history, t he body of knowledge and experience for 

establishing an acceptable limit 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 higher exposure than what 

the 100 ppm limit is based on (e.g., 100,000 times the expected high end exposure)4 either a higher 

limit is needed for the study to be acceptable or a Tier II (definitive endpoint) test is needed. 

7. Comment (Dow) Waivers for the Activated Sludge Sorption Isotherm; Aerobic Aquatic 

Metabolism; Anaerobic Aquatic Metabolism (AMP); Ready Biodegradability; Porous Pot Test; 

Simulation Tests to Assess the Biodegradability of Chemicals Discharged to Wastewater and 

Simulation Test -Aerobic Sewage Treatment: A. Activated Sludge Units studies are requested 

since "[ ... ] both DMO and AMP are readily biodegradable". 

An examination of the chemical structure and a review of information in the Robust 

Summary for AMP, indicates that a high percentage of AMP may be removed by 

conventional sewage treatment systems. Specifically, the biodegradation of AMP has been 

demonstrated in a laboratory ready biodegradability study to remove 89% of the 

biochemical oxygen demand (BOD) in 28 days under aerobic conditions, using non-adapted 

domestic activated sludge inoculum (OECD Guideline test 301F). The primary removal 

mechanism was attributed to mineralization. 

Agency Response: All general environmental fate data requested in the March 16, 2012 memorandum 

are still required. Anaerobic aquatic (OCSPP 835.4400) and aerobic aquatic (OCSPP 835.4300) 

metabolism data for the degradate AMP cannot be waived because the only acceptable environmental 

fate data are hydrolysis and photodegradation in water, which represent chemical degradation. 

4 Pesticide Assessment Guidelines Subdivision E. Hazard Evaluation: Wildlife and Aquatic Organisms. Prepared 

by Ecological Effects Branch, Hazard Evaluation Division, Office of Pesticide Programs. EPA-540/9-82-024. (see 

page 18 for discussion of development of cut-off) http://nepis.epa.gov/ 

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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 

sorption. Ready Biodegradability (835.3110) 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% of AMP degraded in 28 days in a Ready 

Biodegradability 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 inhibition (ASRI) test and depending on the outcome of the ASRI test, either a ready 

biodegradability test or one of the following simulation 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 results of the 

potential for AMP to be demonstrated to readily biodegrade. To reiterate, these simulation 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 or 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 environmental loading from uses, environmental fate, and ecological 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 formation of formaldehyde 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 real-world use conditions to address metabolite formation and decline as a result of 

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DMO application. These data clearly have the potential to refine any estimates of ecological and human 

health exposure and risk because they provide additional information on which the Agency can base its 

decisions. The hydrolysis data (OCSPP 835.2120) on the TGAI form of DMO are limited to chemical 

degradation because the test guideline requires sterility to isolate individual routes of dissipation (e.g. 

chemical degradation or microbial metabolism). However, data on End Use products do not take the 

place of aquatic metabolism studies (OCSPP 835.4300 and 835.4400) which simulate combined chemical 

and microbial degradation in surface water and bottom sediment. They also do not necessarily take the 

place of sewage treatment studies. 

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