OFFICE OF CHEMICAL SAFETY
AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENC Y
WASHINGTON, D.C. 20460

Date: November 13, 2015

PC Code: 129092

DP Barcodes: D427655

MEMORANDUM

SUBJECT: Review of Comments on Addendum to the Ecological Risk Assessment for Fenoxaprop-p-ethyl

TO: Miguel Zavala, Chemical Review Manager Tracy Perry, Team Leader Kelly Sherman, Branch Chief Risk Management and Implementation Branch III

Pesticide Re-evalua tion Division (7505P)

FROM: Thomas Steeger, Ph.D., Senior Science Advisor Chuck Peck, Environmental Fate Scientist

Environmental Risk Branch IV

Environmental Fate a nd Effects Division (7507P) Office of Pesticide Programs

THROUGH: Jean Holmes, D.V.M., Branch Chief Katrina White, Ph.D., Risk Assessment Process Leader

Environmental Risk Branch IV

Environmental Fate a nd Effects Division (7507P) Office of Pesticide Programs

The Environmental Fate and Effects Division (EFE D) has reviewed comments from the technical registrant, Bayer CropScience, on the Addendum to the Ecological Risk Assessment written in support of the proposed Interim Registration Re view decision for fenoxaprop-p-ethyl (FPE; PC Code 129092). Below is a brief summary of each comment followed by EFED’s response.

 The registrant asserts that contrary to what is stated in the A ddendum, Bayer did not recommend the use of root length or weight as an appropriate measure for effects in nontarget plant testing given the high variabili ty of measures of root and/or radicle length/weight in such studies.

EFED concurs with the registrant’s assertion that they did not r ecommend the use of root length or weight as an appropriate measure of effects in non-target terrestrial pl ant testing. Rather, the2 registrant recommended the use of shoot length and weight, which is consistent with the measurement endpoints identified in the Office of Chemical Safety and Pollution Prevention

Guideline 850.4100 1 for examining the effects of pesticid es on seedling emergence and seedling growth. The guideline specifies that shoot length and shoot biomass (dry weight) of surviving seedlings are measured for determining a no-obse rved-adverse effect concentration (NOAEC) and

a lowest-observed-adverse e ffect concentration (LOAEC).

 Bayer agreed with EFED’s use of a chronic di etary-based no-observed- adverse effect level (NOAEL) of 9 mg/kg/day based on the rat 2-generation study and concurred with the Agency’s characterization that the use of this endpoint is co nservative and would likely overestimate any potential risk.

EFED appreciates Bayer’s recogni tion that the chronic mammalia n NOAEL is appropriate for use

in risk assessment.

 The registrant asserts that the minimum reapplication inte rvals (MRIs) of 159 days or longer used to estimate terrestrial risk using the T-REX were inappropr iate to represent a chronic exposure scenario. According to the registrant, mammals exposed for 150+ days following initial application are in different life stages and treated crops have been harvested leading to turnover of plant material in-field. Bayer furt her noted though that specific to FPE, the foliar dissipation half-life (5.6 days) used in T-RED coupled with the long MRIs result in minimum residues by the tim e of the second application and that when the MRI is placed into context and when c oupled with the conservative NOAEL of 9 mg/kg/day, chronic risk is unlikely.

As summarized in Table A1 of the Addendum, MRIs ranged fr om 14 days to a maximum of 285 days. The long MRIs are intended to account for labe ls where the reapplication interval is either not specified or is vague. The long MRIs are al so designed to account for applications that may occur to a field after the growing season, as allo wed for on the label. The T-REX model (v 1.5.2)

is intended as a screen and the uses modeled indicate that even with an MRI of 14 days, risk quotient (RQ) values exceed the level of concern (LOC) for chronic risk to mammals. The registrant is correct in noting that with the folia r dissipation half-life of 5.6 days used for modeling FPE in T-REX, residues by 150+ days would likely be low; however, based on multiple applications and the extended MRI, RQ values exceed chronic risk LOCs for mammals. The

footnote to Table A1 indicates that when multiple reapplicati on intervals are used, the second interval represents an application that occurs out side the growing season, but still represents the potential for exposure. Therefore, while the regist rant is correct in noting that treated crops would have likely been harvested leading to turnover of plant material in-f ield, the labels do not specify this practice and residues may remain on in-f ield plant materials which represent potential exposure route for mammals, particularly small mammals feeding on short grasses.

 Bayer expressed appreciation for EPA’s willingne ss to review the non-target plant studies. However, Bayer disagreed with the non-defi nitive NOAEC (<0.081 lbs ai/A) identified for

1 USEPA. 2012. Ecological Effects Test Guidelines OCSPP 850.4100: Seedling Emergence and Seedling Growth. Office of Chemical Safety and Pollution Prevention. (7101). EPA 712-C-012. January 2012.3 tomato based on shoot dry weight in a seedling emergence study (MRID 473334-23 2 ) since the determination was based on empirical rather than statistical significance.

The Agency’s determination regardin g the biological relevancy of th e magnitude of ef fect reported for tomatoes in the seedling emergence study was not based alone on the low variance surrounding

the measurements in the treatment and c ontrol, but on the magnitude of effect, i.e ., 16.9% decrease

in biomass relative to controls. While the study was at Tier II for corn, other plants were tested using a limit treatment of 0.18 mg ai/ kg. When the magnitude of an e ffect is uncertain with respect to its biological versus statistical significant, Agency reviewers would typically look at higher

treatment levels to determine whether the eff ect appeared to be concentration dependent. However, in a limit test, no additional treatment levels available to put the single measurement endpoint into context; therefor e, the non-definitive endpoint (<0.081 lbs ai/A) is still considered

best available information.

 With respect to a Tier II ve getative vigor study (MRID 412769-07 3 ), Bayer agreed with the Agency’s inhibitory response leve l for 25% of the species tested (IR 25 ) values for corn, oat and ryegrass; however, they disagreed w ith the NOAEC reported for each of these three species. According to Bayer, the endpoint us ed to establish the NOAEC appear to be generated from nonstandard data calculations.

In Addendum Table A2 , the NOAEC for corn and ryegrass are reported as <0.00480 and <0.0480 lbs ai/A, respectively, while the va lue for oats is reported as non-a pplicable (NA). These results are consistent with what is reported in the data evaluation record (DER) except for corn where the DER reports a NOAEC of <0.0006 lbs ai/A based on plant height. Based on the limited information provided in the DER and after reviewing the actual study report, the measurement endpoint, i.e

., plant height, is consistent with current guidelines. While the DER also presents the results of visual phytotoxicity ratings, these ratings and there statistical significance were not used to set the

NOAEC.

 With respect to a vegetative vigor study (MRID 473334-24 4 ), Bayer disagreed with the NOAEC value reported in the Addendum for lettu ce. According to the registrant, the percent inhibition of dry weight for lettuce wa s not found statistically significant up to the highest level tested (0.081 lbs ai/A).

In Addendum Table A2 , the NOAEC for lettuce from the Tier II vegetative vigor study is reported as 0.041 lbs ai/A. The registrant is correct in noting that according to the DER, the NOAEC for lettuce is 0.081 lbs ai/A; howev er, the NOAEC value for carrot re ported in Addendum Table A2 is 0.081 lbs ai/A, while that re ported in the DER is 0.041 lbs ai /A based on reductions in root

2 Roshon, Roxana. 2001. Ecotoxicological Ev aluation of Fenoxaprop-P-Ethyl + Mefenpyr-Die thyl Emulsifiable Concentrate (120 + 33 g/L) (Puma ® 120 Super), Terrestrial Plant Seedling Emerge nce. Unpublished study performed by ESG In ternational Inc., Ecotoxicity Laboratory , Specialty Chemicals Division, Guelph Ontari o, Canada. Laboratory report number B003326. Study sponsored by Aventis CropScience Canada Co. , Regina, Saskatchewan, Canada. Study comp leted May 31, 2001. (MRID 473334-23)

3 Chetram, R.S. 1989. Tier II. Vegetati ve Vigor. Nontarget Phytotoxicity Study. HOE-04630 Study No. LR89-14A. Performed by Pan

Agricultural Labs., Inc., Madera, CA (MRID 412769-07).

4 Roshon, R. 2001. Ecotoxicological Evaluation of Fenoxaprop-P-Et hyl + Mefenpyr-Diethyl Emulsifiable Concentrate (120 + 33 g/l) (Puma ® 120 Super), Terrestrial Plant Vegetative Vigor. Unpublished study performed by ESG Interna tional Inc., Ecotoxicity Laboratory, Spec ialty Chemicals Division, Guelph Ontario, Canada. Laborator y report number B003327. Study sponsored by Aventis CropScience Canada Co., Regina, Saskatchewan, Canada. Study completed May 31, 200I. (MRID 473334-24)4 length. Therefore, while the regist rant is correct with respect to lettuce, the most sensitive NOAEC

for dicots of 0.041 lbs ai/A used for risk assessment remains the same.

EFED appreciates the comments provided by Baye r CropScience regarding the Addendum to the Ecological Risk Assessment written in support of the proposed Interim Registration Review decision for FPE. However, the comments do not affect the risk assessment conclusions.