UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

PC Code: 016331 

DP Barcode: 426301 

MEMORANDUM 

DATE: 

SUBJECT: 

TO: 

FROM: 

Through: 

March 24, 2015 

Response to Comments Submitted by Sumitomo Chemical Company Regarding 

the Proposed Decision Document and Environmental Fate and Ecological Risk 

Assessment for Momfluorothrin 

Julie Chao, Risk Manager Reviewer 

Kahle Davis, Product Manager Team 3 

Marietta Echeverria, Branch Chief 

Invertebrate - Vertebrate Branch 1 

Registration Division (7505P) A1iJ 

3 _ z..{- / 5 

Nathan Miller, Biologist tJ/:-7~ Environmental Risk Branch VI 

Environmental Fate and Effects Division (7507P) u 

_IA. d I '"3:}{-\) Mark 

Monica 

Corbin, 

Wait, 

Branch 

Risk Assessment 

Chief 

Process Leader 

~ 

~ W ~ 3 /Z l'/ \ S 

Environmental Risk Branch VI 1' 

Environmental Fate and Effects Division (7507P) 

In response to the "Environmental Fate and Ecological Risk Assessment for the Section 3 New 

Chemical Registration of the Pyrethroid Insecticide Momfluorothrin" (Document ID EPA-HQOPP-2013-0478-0014 in www.regulations.gov ), Sumitomo Chemical Company ("Sumitomo") 

provided comments during the public comment period (EPA-HQ-OPP-2013-0478-0018). The 

purpose of this memorandum is to address those comments and respond to technical/sciencerelated questions and comments as they pertain to the data reviews and the ecological risk 

assessment document. In summary, EFED does not concur with Sumitomo's comments 1, 2, 3, 

and 5 pertaining to data acceptability. Comment 4 will be addressed separately by the Health 

Effects Division. EFED appreciates the editorial corrections identified in comments 6 and 7 and 

will incorporate these suggestions within any future momfluorothrin risk assessments. 

Page 1of5 
Page 2 of 5

Sumitomo Comment 1. Midge lifecycle data evaluation record: The 49-day midge lifecycle 

test (MRID 49019968) is described as "Supplemental" because of the statistically significant 

difference for development rate. However, the study is considered "Acceptable" (NOEC = 0.035 

mg/kg) as the following reasons:

 The study was conducted according to the international test guidelines and the results 

were appropriately evaluated using the appropriate control (solvent control in this 

case).

 The development rate of solvent control (0.0367) was faster than that of control (0.0343) 

and the solvent control (i.e., better performance) were used for evaluation (i.e., 

conservative analysis).

 The results of the definitive test are consistent with the preliminary range-finding test 

(i.e. emergence rate is the most sensitive parameter rather than development rate and 

EC50 of emergence rate would lay down 0.03-0.75 mg/kg).

EPA Response: EFED classified MRID 49019968 supplemental, for qualitative use only, 

because it does not establish a definitive no-effect endpoint suitable for use in risk 

assessment. From the DER: 

For midge emergence, based on time weighted average concentrations, the NOAEC was 

established to be 0.030 mg a.s./kg and the LOAEC was established to be 0.073 mg a.s./kg. 

The EC50 for percent emergence was calculated to be 0.14 mg/kg, with corresponding 95% 

confidence intervals of 0.10 to 0.17 mg/kg, using the probit method. The NOAECs for male, 

female, and male-female combined development rate data were established to be < 0.013, 

0.03, and < 0.013 mg/kg, respectively (LOAECs of 0.013, 0.073, and 0.013 mg/kg, 

respectively). Male development rate was not promoted by more than 10% in comparison to 

the negative control [Note that EFED policy is to make statistical comparisons to the 

negative control (USEPA, 2008)], and solvent interference may have contributed to the 

reported significance at all treatment concentrations, considering an Equal Variance t TwoSample Test which determined development rate in the solvent control to be significantly 

promoted compared to the negative control. Since no concentration tested resulted in > 50% 

promotion (or inhibition) of development rate, the EC50 values were empirically estimated to 

be > 0.17 mg/kg, the highest concentration statistically analyzed.

NOAEC: < 0.013 mg a.s./kg

LOAEC: 0.013 mg a.s./kg

Most sensitive endpoint: Male development rate, combined male-female development rate

Sumitomo Comment 2. Aquatic nonvascular plant data evaluation record: The 96-hour 

aquatic non-vascular plant study (MRID 49019991) is described as "Supplemental" because of 

potential interference from the co-solvent. However, the study is considered "Acceptable" (96hrIC50 >4.8 mg/L) as the following reasons.

 The study was conducted according to the international test guidelines and the results 

were appropriately evaluated using the solvent control (OECD test guideline 201 says 
Page 3 of 5

that "When solvents are used to prepare the test solutions, the solvent controls rather 

than the controls without solvents should be used in calculation of percent inhibition").

 As stated in the report, no significant difference was detected between control and solvent 

control for any endpoints.

 The 96hr-IC50 value (i.e., >4.8 mg/L) are not changed if the control or solvent control is 

used for the evaluation.

 The results of the definitive test are consistent with the preliminary range-finding test.

EPA Response: EFED classified MRID 49019991 supplemental, for qualitative use only, 

because the study design did not employ four replicates per treatment level as stipulated in 

the guideline, and a solvent effect confounds interpretation of treatment response. Further, 

undissolved test substance was observed at the highest treatment concentration which makes 

the true exposure concentration for that treatment level uncertain. As the [study design]

adheres to the OECD guidelines, which stipulates that three replicates are sufficient, this does 

not affect the acceptability of the study in the PMRA’s perspective. However, the PMRA 

agrees with the EPA that the other noted deficiencies influence the usefulness of the study.

EPA Classification: Supplemental, for qualitative use only

PMRA Classification: Acceptable

IC50: Could not be determined

Most sensitive endpoint: N.A.

NOAEC: 0.37 mg a.i./L

Most sensitive endpoints: Cell density

Sumitomo Comment 3. Avian reproduction study data evaluation record: Classification of 

supplemental should be corrected to acceptable because there was no effect on birds treated with 

the test item in the reproduction study with bobwhite (MRID 49019979).

EPA Response: EFED does not concur with Sumitomo’s assertion that there was no effect 

on birds treated with the test item in this avian reproduction test. The Executive Summary of 

the DER for MRID 49019979 explains the basis for the study classification: 

“This study, while scientifically sound, is classified as supplemental because it does not 

establish a definitive overall no-effect concentration. Adult female weight gain was 

significantly reduced compared to the control at the lowest test concentration; therefore, the 

concentration response relationship for female weight gain resulting from dietary exposure to 

momfluorothrin cannot be determined. 

NOAEC: < 241mg a.s./kg diet

LOAEC: 241 mg a.s./kg diet

Most sensitive endpoint: Female weight gain”
Page 4 of 5

Because of the significant effects to female weight gain, EFED does not concur with 

Sumitomo, and no changes will be made to the study classification within the risk 

assessment. 

Sumitomo Comment 4. Two generation rat reproduction study: Comments were submitted in 

regards to the appropriate NOAEC and LOAEC from the two generation rat reproduction study 

(MRID 49020018).

EPA Response: EFED concurs with Sumitomo’s comments, as confirmed by the Health 

Effects Division’s review of this study. The two generation rat reproduction study NOAEL 

and LOAEL should have been reported as 500 mg/kg diet and 1500 mg/kg diet respectively, 

based on significantly decreased body weights in both sexes of the F1 and F2 pups. Future 

momfluorothrin risk assessments will reflect the correct endpoints and exposure duration.

Sumitomo Comment 5. Avian acute oral toxicity test with zebra finch data evaluation 

record: Two birds [were] replaced due to [regurgitation]. However, one was replaced only 7 

minutes after dosing and the other was replaced 40 minutes after dosing. And the replaced birds 

were adequately observed during rest of test period. Therefore, we consider it not appropriate 

to classify the study to supplemental based on these events.

In this context, the following should be corrected.

Page 41 4.3.2 Effects Uncertainties

1st sentence in 3rd paragraph: “a NOAEC” should read “a LD50”, and “at the lowest dose 

tested” should read “in the two treatment”.

EPA Response: EFED does not concur with Sumitomo’s assertion. The Executive 

Summary of the DER for MRID 49019973 explains the basis for the study’s classification: 

“The 14-day acute oral toxicity of momfluorothrin (S-1563) to the zebra finch (Poephila 

guttata) was determined in the laboratory, with groups of 10 birds per treatment exposed to 0 

(negative control), 292, 486, 810, 1350, and 2250 mg a.s./kg bodyweight. The study authors 

replaced two birds (one in the 292 mg ai/kg bw treatment, and one in the 486 mg ai/kg bw 

treatment) that regurgitated the dose during the test. EFED treats these replaced birds as 

mortalities [(USEPA, 2012)]. The 14-day LD50 was estimated to be above 2250 mg

a.s./kg bw, the highest dose applied. The no-mortality and the no-observed-adverse-effectlevels (NOAEL) were less than the lowest dose tested (i.e., < 292 mg a.s./kg bw).

LD50: > 2250 mg a.s./kg bw

NOAEL: < 292 mg a.s./kg bw

This study is classified as supplemental because of replacement of birds that regurgitated in 

the 292 and 486 mg ai/kg bw treatments, but is considered suitable for quantitative use in risk 

assessment.”
Page 5 of 5

Sumitomo Comment 6. Summary table of submitted terrestrial toxicity studies for 

momfluorothrin in Appendix B of the ecological risk assessment: We consider it appropriate 

to add tables for rats acute dermal toxicity study (MRID 49020098) and rats chronic toxicity test 

(MRID 49020020) to Table 2 of page 56 of the risk assessment.

EPA Response: These studies were omitted from the summary table of Appendix B as they 

are not routinely considered for ecological risk assessment but rather by the HED’s human 

health risk assessment.

Sumitomo Comment 7. Other minor comments: Sumitomo comments that the adult honey 

bee acute contact toxicity endpoint reported in the EFED risk assessment as 0.2 μg a.i./bee 

should instead be reported as 0.21 μg a.i./bee. Table numbering and other editorial corrections 

are presented.

EPA Response: EFED does not agree with the assertion that the toxicity endpoint for the 

adult honey bee acute contact toxicity study is erroneously reported, but concurs with the 

other proposed Sumitomo corrections regarding spelling, table numbering, and phenothrin/dphenothrin active ingredient identification. While the study authors reported a contact LD50

of 0.21 μg a.i./bee, EFED’s independent statistical analysis using the data provided by the 

laboratory via the study report established a different LD50 threshold than was reported by the 

study author. In the statistical analysis appended to the DER (MRID 49019985), the 48-hour 

acute contact LD50 is identified as 0.201 μg a.i./bee, with 95% lower and upper confidence 

limits of 0.171 and 0.233 μg a.i./bee, respectively.

Corrections to table numbering and minor editorial comments will be addressed in any future 

momfluorothrin risk assessments.

References:

USEPA. 2008. Guidance for the Use of Dilution-Water (Negative) and Solvent Controls in 

Statistical Data Analysis for Guideline Aquatic Toxicology Studies. Memorandum from Donald 

Brady, Director, to the Environmental Fate and Effects Division. September 25, 2008.

USEPA. 2012. Guidance for Use When Regurgitation is Observed in Avian Acute Toxicity

Studies with Passerine Species. Memorandum from Donald Brady, Director, to the 

Environmental Fate and Effects Division. April 9, 2012. Available online at:

http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/terrestrial_biology_te

ch_team/tbtt_regurg_acute_passerine.htm