2

EFED Response #1:

EFED agrees that the use of modern nozzles that incorporate spray-drift reduction technology and

produce courser sprays would reduce spray drift, and would result in shorter distances from the fields 

where the spray drift exposure exceeds the EC05. However, all applicators are not using nozzles with 

spray-drift reduction technology. Some applicators are expected to use nozzles that produce very fine to 

fine droplets, which is the default setting for ground spray in the AgDrift model. All product labels 

would need to be modified to require the use of nozzles designed for reduced spray drift, or specify 

limits on the allowable coarseness of the ground spray, before it would be appropriate to change the 

default droplet-size parameter used in the AgDrift model to generate spray drift estimates for a 

quantitative risk assessment.

Likewise, EPA’s policy is to base the analysis on the upper 90th percentile spray drift deposition values. 

This differs from the analysis that DAS presents, which was based on the 50th percentile. EPA’s policies 

on the use of input parameters for modeling pesticide spray drift are described in the EFED 

memorandum of December 20, 2013 entitled Guidance of Modeling Offsite Deposition of Pesticides via 

Spray Drift for Ecological and Drinking Water Assessments.

In DAS’s spray drift modeling for flumetsulam, they make use of spray drift data collected by 

Agricultural and Agri-Food Canada. While EFED has evaluated the spray drift deposition data 

submitted by Crop Life America (i.e., the “Canadian data” or “Wolf data”), issues with the completeness 

of data prevent EFED from using the information for quantitative purposes. EFED is in the process of 

evaluating all spray drift data that have been submitted to the Agency and developing a policy for the 

use of existing and future deposition data in the conduct of its assessments. Until this policy has been 

formalized, EFED will continue to use methods developed in its Guidance on Modeling Offsite 

Deposition of Pesticides Via Spray Drift for Ecological and Drinking Water Assessments document in 

the quantitative assessment of spray drift, while using supplemental data submitted to the Agency for 

characterization purposes. The only exception would be for spray drift deposition data, generated 

specifically for the active ingredient/formulated product being assessed. Such data could be used for 

quantitative purposes, if found to be acceptable by the Agency.

DAS Comment #2: Frontrow Herbicide (62719-299) has been cancelled

Frontrow Herbicide (62719-299) should not be included in the list of registered products discussed in 

the use profile because Dow Agroscience has submitted a cancelation notice for this product.

EFED Response #2:

EFED defers to the Registration Division on the current registration status of this product. 
3

DAS Comment #3: The use profile table was corrected to reflect current labels

DAS marked several corrections to the information provided in Table 2.5 (Summary Use Profile for 

Flumetsulam). While this table appears in the Human Health section of the PRA, DAS indicates that 

some of the errors also occur in Table 3 of the section on ecological risk and need to be corrected.

EFED Response #3:

Table 3 in the preliminary ecological risk assessment portion of the PRA differs from Table 2.5 of the 

human health section. Table 2.5 gives the maximum application rates for every registered product, 

whereas Table 3 only lists the maximum application, on any label, per crop and application timing. 

Some of the information in Table 3 is based on labels of products of companies other than DAS. Also, 

Table 3 does not attempt to list the use restrictions and limitations in the details given in Table 2.5. After 

review of the corrections that DAS made to Table 2.5, we did not find that any corrections were needed 

for Table 3 of the preliminary ecological risk assessment.

DAS Comment #4: Recommends quantitative use of monitoring data

In reference to the discussion of monitoring data on pages 28-30, DAS claim that the monitoring data 

shows convincing evidence that the high end of flumetsulam concentrations in the aquatic environment 

is less than 1 μg/L. They disagree that these monitoring data should only be considered as qualitative 

information in the ecological risk assessment.

EFED Response #4:

EFED does and will consider monitoring data, but without sufficient additional ancillary information,

monitoring data by itself is often difficult to interpret. The frequency of sampling in monitoring 

programs is generally insufficient to determine the peak concentration. Additionally, monitoring data

frequently does not provide adequate information concerning the surrounding land use or pesticide use 

at or upstream, flow rates, or with a hydrologic connection to the monitoring site.

DAS Comment #5: Reported IC50 for green algae is not correct.

DAS notes that the 5-day IC50 that the risk assessment reports for a green algae toxicity study (MRID 

41931743) was 3.21 μg a.i./L, whereas the result reported in the study report was 4.93 μg a.i./L, and the 

same endpoint was previously reported in another EPA document as 3.31 μg a.i./L.

EFED Response #5:

The IC50 endpoint value reported in the risk assessment, 3.21 μg a.i./L, is the IC50 endpoint that was 

reported in the DER. The endpoint value of 3.31 that was reported in a previous EPA document appears 
4

to be a typographical error. In reviewing the DER for this study, we became aware that the data were 

analyzed by EPA using probit analysis, a method that is not appropriate for analyzing cell count data. 

This explains why the 5-day IC50 reported in the original DER differed from that reported in the study 

report. EPA therefore reanalyzed the cell count data using the CETIS software and applying a weighted 

nonlinear regression method for analyzing continuous data (Bruce and Versteeg, 1992). The 5-day IC50

calculated by CETIS was 4.76 μg a.i./L, which is similar to the value reported in the study report (4.93 

μg a.i./L).

EPA policy is to use the 4-day (96-hr) IC50 to calculate RQs for risk to nonvascular plants. CETIS was 

therefore used to analyze the 4-day cell count data reported in this study. The 4-day IC50 was 

determined to be 3.52 μg a.i./L. Correcting the algal toxicity RQs using the correct 4-day IC50 value 

(3.52 μg a.i./L) would reduce the RQ values for nonvascular plants by only a factor of 1.1. This would 

have little effect on the RQ values and would not change any of the risk conclusions for nonvascular 

plants. The DER for this study has been revised to report the correct 4-day IC50.

DAS Comment #6: Additional data are provided to calculate the NOAEL for terrestrial plants

DAS notes that a footnote to Table 17 states that the EPA was not able to calculate the NOAEL for a 

non-guideline seedling emergence study (MRID 43485801) because the study report did not report 

summary data for the endpoint at a replicate level. DAS claims that replicate data for this endpoint were

provided in Appendix K of the study report. They have submitted a copy of these data to EPA via mail, 

and requests that it be used to calculate the NOAEL values. They request that the NOAEL values be 

used in the risk assessment rather than the EC05 values.

EFED Response #6:

The replicate data provided by DAS allows EPA to calculate NOAEL values for the seedling emergence 

study conducted with flumetsulam and four other pesticides (MRID 43485801). The NOAEL values are 

somewhat higher than the IC05 values that were used in the risk assessment. Recalculating the RQs with 

the NOAEL values therefore decreases the RQ values for listed species. It does not affect the RQs 

calculated for nonlisted plant species, which are based on the IC25 values. It also does not affect results 

of the calculations done with AgDrift to determine the distance from the edge of the field where the 

spray drift exposure exceeds the toxicity endpoint. Since that analysis was for spray drift only, it used 

toxicity results only from the vegetative vigor study, not from this seedling emergence study.

The RQs for listed plant species were calculated based on the most sensitive monocot species, sorghum, 

and the most sensitive dicot species, canola (also called rapeseed). Plant weight was the most sensitive 

endpoint for both species. The newly calculated NOAEL and LOAEL values for sorghum and canola, as 

well as the previously calculated EC05 values, are given in the table below.
5

Species and endpoint NOAEL LOAEL EC05

Sorghum(monocot), plant weight 0.00223 lb a.i./A

(2.5 g a.i./ha)

0.000568 lb a.i./A

(5.0 g a.i./ha)

0.000568 lb a.i./A

Canola (dicot), plant weight 0.0000697 lb a.i./A

(0.0781 g a.i./A)

0.000139 lb a.i./A

(0.156 g a.i./A)

0.0000452 lb a.i./A

The new NOAEL values are greater than the IC05 values by a factor of 3.93 for sorghum and by a factor 

of 1.54 for rapeseed. Therefore, the listed RQs for listed monocot species decrease by a factor of 3.93, 

and the RQs for listed dicot species decrease by a factor of 1.54. This change is not enough to reduce 

any of the RQs for listed dicots to below the LOC of 1. For monocot species, the RQ for exposure to 

listed upland plants from post-emergence ground applications on soybeans is decreased below the LOC, 

while all of the other RQs, including all RQs for wetland species, still exceed the LOC. Therefore, 

recalculating the RQs using the NOAEC values in place of the IC05 values do not change any of the risk 

conclusions for listed species of plants except for upland monocot species associated with postemergence use of flumetsulam on soybean. It is noted, however, that the RQ for preplant/pre-emergent 

use of flumetsulam on soybean is still above the LOC, and thus the overall risk conclusion for listed 

upland monocots associated with soybeans does not change.

Since the changes in the RQs related to the change of these toxicity endpoints does not alter the overall 

risk conclusion for any use site, the preliminary risk assessment document will not be modified based on 

this change. However, the DER for this study has been revised to include the newly calculated NOAEC 

and LOAEC values.

DAS Comment #7: The assumptions of the TerrPlant Model are unrealistic and overly-conservative

DAS presents several criticisms of the assumptions used in the TerrPlant model to estimate exposure to 

nontarget plants. They propose alternative assumptions and calculations for estimating exposure which 

they claim are more realistic. They then present results from a modified tier 1 risk assessment for 

terrestrial plants, and a refined tier 2 risk assessment

EFED Response #7:

We agree that the TerrPlant Model provides upper bound estimates of off-site exposure to terrestrial 

plants. EFED is currently developing a more refined tier II terrestrial plant exposure model to address 

this issue. The comments that DAS submitted concerning recommended refinement of the terrestrial 

plant exposure model have been forwarded to the team developing this new model. However, until this 

new model is completed, has undergone peer review, and QA/QC review, EFED will continue to rely on 

the TerrPlant model for conducting quantitative exposure assessments for risk to nontarget terrestrial 

plants.
6

Comments from Minnesota Department of Agriculture

The Minnesota Department of Agriculture (MDA) submitted monitoring data for flumetsulam. Data sets 

were provided which give results of analysis for flumetsulam residues in samples of surface water and 

ground water collected in Minnesota during 2011 through 2013. In the surface water monitoring, 

flumetsulam was detected in 7 out of 375 (1.9%) of the samples. Detected flumetsulam concentrations 

ranged from 0.0508 to 0.101 μg/L. In the ground water monitoring, flumetsulam was detected in 16 out 

of 600 (2.7%) of the samples. Detected flumetsulam concentrations ranged from 0.0535 to 0.137 μg/L. 

The limit of detection for both the surface and ground water analysis was 0.050 μg/L.

EFED Response:

EFED appreciates the MDA making their monitoring data available to us. The information submitted by 

Minnesota reports the date of sampling and indicates a relatively low limit of detection, but without 

information concerning the surrounding land use or pesticide use at or upstream from the monitoring 

site, as well as other relevant ancillary data, further analysis is limited.

REFERENCES

Bruce, R.D. and D.J. Versteeg. 1992. A statistical procedure for modeling continuous toxicity data. 

Environ. Toxicol. Chem. 11:1485-1495.