UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

2016 Addendum to the Environmental Fate 

and Ecological Risk Assessment

for Sulfoxaflor Registration

Sulfoxaflor: A 50:50 Mixture of Diastereomer 1 and 2

Prepared by:

Keith G. Sappington. M.S.

Mohammed A. Ruhman, Ph.D.

Reviewed by:

Mah Shamim, Ph.D.

 

United States Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch V

1200 Pennsylvania Ave.

Mail Code 7507P

Washington, D.C. 20460
1

Contents

1. Executive Summary............................................................................................................... 2

2. Risk Assessment Approach................................................................................................... 2

3. Pesticide Exposure Potential of Bees ................................................................................... 3

3.1 Potential for On-Field Exposure ...................................................................................... 5

3.2 Potential for Off-Field Exposure (Spray Drift)................................................................ 5

4. Tier 1 Risk Estimation (Default Exposure)......................................................................... 5

4.1 Summary of Tier 1 Bee Toxicity Data ............................................................................. 6

4.2 On-Field Risk (Contact and Oral Exposure).................................................................... 7

4.3 Off-Field Risk (Contact With Spray Droplets) ................................................................ 7

4.4 Off-Field Risk (Contact With Residues On Foliage)....................................................... 8

4.5 Off-Field Risk from Oral Exposure (Pollen and Nectar)................................................. 9

5. Refined Tier 1 Risk Assessment ......................................................................................... 10

5.1 Off-Field Risk from Oral Exposure (Refined)............................................................... 10

6. Tier 2 Risk Characterization.............................................................................................. 12

7. Ecological Incident Reports................................................................................................ 13

8. Environmental Persistence of Sulfoxaflor in Bee Relevant Matrices............................. 13

9. Uncertainty Associated with Lack of Tier 1 Chronic Data for Bees............................... 15

10. Risk Assessment Conclusions, Assumptions, and Uncertainty.................................... 16

11. Additional Recommended Data...................................................................................... 18

Appendix A. Forager-Collected Pollen and Nectar Residues of Sulfoxaflor and Associated 

Acute Oral RQs From the Cotton Tunnel Study (MRID 48755606)............................................ 19

Appendix B. Bounding Analysis of the Potential for Chronic (Tier 1) Oral Risks to Adult Bees

....................................................................................................................................................... 22
2

1. Executive Summary

This Addendum summarizes the ecological risks associated with the proposed Section 3 

registration of Transform® WG and Closer® SC (active ingredient: sulfoxaflor) for use on various 

crops as a foliar spray and was conducted in accordance to revised labels dated May 5, 2016. The 

revised labels reflect numerous changes relative to the original EFED Section 3 assessment 

(D382619) that include: 1) removal of certain bee attractive crops (e.g., citrus, cotton, cucurbits, 

soybean and strawberry; 2) prohibiting applications before or during bloom (e.g., canola, stone 

fruits, pome fruits, etc.); and 3) prohibiting use on crops grown for seed production (e.g., 

brassica, bulb vegetables, leafy vegetables, etc.). Since the 9th Circuit Court’s decision regarding 

the prior registration of sulfoxaflor concerned the potential risks to bees, this assessment only 

focuses on bees. Potential risks to other taxa are lower or equivalent to that described in the 

previous Section 3 assessment (D382619)2, noting that the new labels contain a lower maximum 

single application rate of 0.09 lb a.i./A (ground or aerial spray) and a maximum annual rate of 

0.266 lb a.i./A among all the proposed uses. 

On-Field Risks to Bees. Based on the proposed labels, acute and chronic risks to bees foraging 

on the treated field are not indicated. Lack of exposure of bees on the treated field is presumed 

since the proposed crops are either considered unattractive to bees, are harvested prior to bloom, 

or involve applications that are prohibited until after the bloom period of the crop. 

Off-Field Risks to Bees. As with any foliar spray application, there is potential drift to areas 

adjacent to the treated field. A spray drift analysis indicates that the spatial extent of acute risks 

beyond the treated field is very limited (<1 – 12 feet beyond the treated field). In the absence of 

chronic Tier 1 data for individual bees, a bounding analysis was conducted using acute-tochronic ratios. This analysis suggests that estimated chronic risks are also spatially limited 

beyond the treated field (2-46 feet, depending on modeling and toxicity assumptions). In addition 

to being spatially limited, available data suggest that the temporal extent of acute and chronic 

risks beyond the treated field is also limited to relatively short periods of time (e.g., half of 

sulfoxaflor degrades in pollen and nectar within 9 days or less based on the vast majority of 

residue data). It is noted that the spray drift analysis is considered conservative due to 

assumptions that plants will be in bloom immediately next to the treated field and that bees will 

obtain 100% of their diet from this spatially limited area.

2. Risk Assessment Approach

Estimating risks to bees associated with the proposed Section 3 use of sulfoxaflor follows the 

Office of Pesticide Programs’ (OPP’s) published guidance entitled: “Guidance for Assessing 

Pesticide Risks to Bees” (USEPA 2014)3

. This guidance presents an iterative, tiered process for 

assessing risks that considers multiple lines of evidence related to exposure and effects of 

pesticides to bees. In summary, this risk assessment process involves:

 2 http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2010-0889-0022 3 USEPA et al. 2014. Guidance for Assessing Pesticide Risks to Bees. https://www.epa.gov/pollinatorprotection/pollinator-risk-assessment-guidance 
3

1. Estimating the potential for exposure of bees to the pesticide for each of the proposed 

uses;

2. Conducting a Tier 1 risk assessment based on default (high-end) exposure estimates for 

those uses where a reasonable potential for exposure exists;

3. Conducting a refined Tier 1 risk assessment based on measured residues in pollen and 

nectar; and,

4. Evaluating risks based on higher-tier (Tier 2 or Tier 3) colony level-effects data (as 

necessary).

3. Pesticide Exposure Potential of Bees

The first step in this process involves a qualitative assessment of the potential for exposure of 

bees to the pesticide. The exposure potential of bees is determined by the application method, 

timing, location (e.g., indoor vs. outdoor), attractiveness of the crop to bees, agronomic practices 

(e.g., timing of harvest), the availability of alternative forage sources and label restrictions 

regarding applications during the crop bloom period. Primary routes of exposure include 

interception of spray droplets (contact) and ingestion of contaminated pollen and nectar (oral).

Based on the labels submitted to the Agency on May 5, 2016, the proposed uses of sulfoxaflor 

involve ground or aerial foliar spray applications with medium or coarser spray nozzles (as 

defined by the American Society of Agricultural and Biological Engineers; ASABE). For each 

of the proposed crops or crop groups, information on their attractiveness to bees, maximum 

application rates, and label restrictions regarding the blooming period is summarized in Table 1.

Information on the crop attractiveness was derived from the U.S. Department of Agriculture 

(USDA 20154

).

 4 USDA. 2015. Attractiveness of Agricultural Crops to Pollinating Bees for the Collection of Nectar and/or Pollen.

http://www.ree.usda.gov/ree/news/Attractiveness_of_Agriculture_crops_to_pollinating_bees_Report-FINAL.pdf
4

Table 1. Summary of Crop Attractiveness to Honey Bees (HB) and Bumble Bees (BB) and Proposed 

Application Rates for Sulfoxaflor

Crop or Crop Group Bee Attractiveness1 and 

Agronomic Practices

Bloom

Restrictions2

Max. Non-Bloom Appl. Rate3

Brassica leafy 

vegetables 

High, but usually harvested 

before bloom (except for 

small acreage used for seed 

production)

Applications 

not allowed 

for seed 

production

CLOSERTM

0.09 x 2 (consecutive) @ 7d 

(0.266)

TRANSFORMTM

0.086 x 2 (consecutive) @ 7d 

(0.266)

Bulb vegetables*

Leafy vegetables 

(except Brassica) and 

watercress

Moderate to High for some 

members, but usually 

harvested before bloom

(except for small acreage used 

for seed production)

Leaves of root and 

tuber vegetables

Root and tuber 

vegetables (1A & 1B)

Pome fruits High (apples require managed 

bee pollination)

Only post 

bloom 

applications 

are allowed

Small fruit vine climbing 

(except fuzzy kiwi fruit) 

and low growing berry 

(except strawberry)

Moderate to High (blueberry, 

blackberry, raspberry require 

managed pollination)

Stone fruits High (cherries require 

managed bee pollination)

Tree nuts and pistachio High (requires managed 

pollination; almond)

Turf Grass (commercial 

only) Not attractive N/A

Ornamentals High (assumed)

Only post 

bloom 

applications 

are allowed

CLOSERTM

0.09 x 2 (consecutive) @ 14 d 

(0.266)

TRANSFORMTM

0.086 x 2 (consecutive) @ 14 d 

(0.266)

Fruiting vegetables and 

okra

Moderate (HB) High (BB)

(managed pollination for seed 

production) 

Only post 

bloom 

applications 

are allowed

CLOSERTM

0.07 x 2 (consecutive) @ 7 d 

(0.266)

TRANSFORMTM

0.071 x 2 (consecutive) @ 7 d 

(0.266)

Potatoes 

(1C and 1D)

Moderate 

(BB only)

Only post 

bloom 

applications 

are allowed

CLOSERTM

0.07 x 2 (consecutive) @ 14 d 

(0.266)

TRANSFORMTM

0.071 x 2 (consecutive) @ 14 d 

(0.266)

Succulent, edible 

podded, dry beans Moderate to High

Barley, triticale, wheat Not attractive N/A 

CLOSERTM

0.043 x 2 / @ 14 d (0.086)

TRANSFORMTM

0.047 x 2 / @ 14 d (0.09)
5

Crop or Crop Group Bee Attractiveness1 and 

Agronomic Practices

Bloom

Restrictions2

Max. Non-Bloom Appl. Rate3

Canola

High

(commercial pollination used 

for hybrid seed production)

Only post 

bloom 

applications 

are allowed

CLOSERTM

& TRANSFORM®

0.023 x 2 @ 14 d (0.046)

1 Bee attractiveness based on USDA (2015) 

2 N/A = bloom application restrictions are not applicable because crop is not considered bee attractive 3 Maximum single application rate in bold (lb a.i./A); max. # of consecutive apps; minimum appl. interval, and 

total annual application rate in parentheses.

* label for CLOSER specifies no more than 3 applications/year and no restrictions on consecutive applications

3.1 Potential for On-Field Exposure 

Based on the information summarized Table 1 and USDA’s assessment of crop attractiveness to 

bees, the proposed uses of sulfoxaflor are not expected to result in significant exposure of 

bees on the treated field. This conclusion is reached based on the following considerations:

1. The crops are not considered attractive to bees (e.g., barley, triticale, wheat, turf 

grass);

2. The crops are harvested before bloom and no application is allowed for seed 

production (e.g., brassica, leafy vegetables, bulb vegetables, root/tubers, leaves of 

root/tubers (except potato); or

3. The crops are attractive but applications are only allowed after bloom (e.g., canola, 

ornamentals pome fruits, potato, stone fruits, tree nuts/pistachio, small fruit vine climbing 

& low growing berry [except strawberry & kiwi], and succulent, edible & podded dry 

beans).

3.2 Potential for Off-Field Exposure (Spray Drift)

The OPP bee risk assessment guidance primarily focuses on exposures and risks of bees on the 

treatment site. However, with outdoor spray applications, there is the potential for off-site spray 

drift and subsequent exposure of bees that may be foraging on blooming plants adjacent to the 

treated site. Therefore, off-site exposure of bees (oral and contact) as a result of spray drift is 

also considered possible for all of the proposed uses of sulfoxaflor.

4. Tier 1 Risk Estimation (Default Exposure)

By design, the initial (default) Tier 1 assessment relies on conservative (high end) estimates of 

exposure via contact and oral routes. For contact exposure, only the adult (forager) life stage is 

considered since this is the relevant life stage for honey bees. Furthermore, toxicity protocols 

have only been developed for acute exposures via the contact route. For the oral route, exposure 
6

estimates for bees are compared to acute and chronic toxicity endpoints for both adult and larval 

bees. These toxicity endpoints are defined by laboratory exposures to groups of individual bees. 

4.1 Summary of Tier 1 Bee Toxicity Data

For sulfoxaflor, the Tier 1 laboratory toxicity database is complete for contact exposure and for 

acute larval and adult oral exposure. Acceptable data are not available for estimating chronic 

effects of sulfoxaflor on larval and adult honey bees. In order to estimate the uncertainty 

associated with the lack of chronic effects data for adult bees, an acute-to-chronic ratio approach 

was used, as described in Section 9. It is noteworthy that larval honey bees are much less acutely 

sensitive to oral exposure (7-d LD50 > 0.2 μg a.i./bee) compared to adults LD50 (48-h): 0.0515

ug a.i./bee. Compared to honey bees, sulfoxaflor appears much less toxic on an acute contact 

basis to bumble bees, but is of similar acute oral toxicity. Details of the Tier 1 toxicity test results 

with sulfoxaflor are found in the previous Section 3 new chemical risk assessment (D382619).

Table 2. Tier 1 toxicity test results for sulfoxaflor and bees

Taxa Species Type of Toxicity

(Purity)(1) Toxicological Endpoint MRID

Terrestrial 

Invertebrates 

Honey bee, adult 

(Apis mellifera)

Acute (contact) TGAI LD50 (72-h): 0.379 ug 

a.i./bee

47832102

(Acceptable)

Acute (contact) TEP: 

GF-2032-SC

LD50 (48-h): 0.130 ug 

a.i./bee

47832419

(Acceptable)

Acute (contact) TEP: 

GF-2372-WG

LD50 (48-h): 0.224 ug 

a.i./bee

47832511

(Acceptable)

Acute (oral) TGAI LD50 (48-h): 0.146 ug 

a.i./bee

47832103

(Acceptable)

Acute (oral) TEP: GF2032-SCLD50 (48-h): 0.0515 ug 

a.i./bee

47832417

(Acceptable)

Acute (oral) 

X11719474

LD50 (96-h): >100 ug 

a.i./bee

47832107

(Acceptable)

Acute (oral) 

X11721061

LD50 (48-h): >104 ug 

a.i./bee 48445809

Acute foliar residue 

(TEP: GF-2372-WG)

24-h aged residue 

mortality: 

14% (0.089 lb ai/A or 

100 g ai/ha) 

15% (0.178 lb ai/A or 

200 g ai/ha)

47832512

(Acceptable)

Acute foliar residue 

(TEP: GF-2032-SC)

3-h aged residue 

mortality: 

4% (200 g ai/ha) 

47832420

(Acceptable)

Honey bee, larvae 

(Apis mellifera)

Acute, single dose 

(TGAI)

LD50 (7-d): >0.2 μg 

a.i./bee 48755602

(Supplemental)

Chronic, repeated 

dose (TGAI)

NOAEC (7-d): 0.02 μg 

a.i./bee; LOAEC (7-d) = 

0.2 μg a.i./bee

48755603

(Supplemental)

Bumble bee, adult 

(Bombus terrestris)

Acute (contact) (TEP: 

GF-2032-SC)

LD50 (72-h): 7.55 μg 

a.i./bee

47832418

(Supplemental)
7

Taxa Species Type of Toxicity

(Purity)(1) Toxicological Endpoint MRID

Acute (oral) (TEP: GF2032-SC)LD50 (72-h): 0.027 μg 

a.i./bee

47832418

(Supplemental)

The most sensitive endpoints shown in bold are used for risk estimation. 

4.2 On-Field Risk (Contact and Oral Exposure)

As discussed previously in Section 3.1, exposure of bees on the treated field is not expected. 

Therefore, the potential for risk to bees potentially foraging for pollen and nectar on the 

treated field is considered highly unlikely.

4.3 Off-Field Risk (Contact With Spray Droplets)

In addition to bees foraging on the treated field, bees may also be foraging on blooming plants 

adjacent to the treated fields. In these situations, bees may become exposed through interception 

of pesticide spray droplets that drift off site during application. In order to estimate the potential 

contact exposure of bees to sulfoxaflor when foraging on plants adjacent to treated fields, 

AgDRIFT (version 2.1.1) was run based on available label information. For ground and aerial 

(non-ULV) applications, the label specifies that only medium or coarser spray nozzles shall be 

used. Furthermore, the label specifies a boom height of <4 ft for ground applications and <10 

feet for aerial applications. For wind speed, the labels prohibit application above a wind speed of 

10 mph. 

Results of AgDRIFT modeling for off-site deposition of spray droplets at the maximum 

proposed application rate of 0.09 lb a.i./A for CLOSERTM are shown in Table 3. Since the drift 

of ground and aerial sprays declines exponentially with distance from the treated field, the 

highest off-field exposures occur at the near edge of treated fields. Based on AgDRIFT modeling 

with the maximum application rate of 0.09 lb a.i./A and the Tier 1 acute contact risk assessment 

presented earlier, the acute risk LOC is exceeded for bees potentially foraging in sites ranging up 

to 2 to 12 feet from the treated field, depending on the application method. For this analysis, 

“medium to coarse” spray nozzles with a median droplet diameter of 341 μm was assumed. 
8

Table 3. Equivalent Sulfoxaflor Application Rates Predicted by AgDRIFT at Various Distances from the 

Application Site for the Maximum Application Rate of 0.09 Lb A.I./A. and Distance from Treated Field 

Beyond Where the Acute Risk Level of Concern for Bees (Contact Exposure) is Exceeded.

Method Droplets Dv0.5 

(μm)

Distance from the field and point estimate of 

application rate (lb a.i./A)

Distance From 

Field Edge 

Where the 

Acute Risk LOC

is Exceeded3

(ft)

10 ft 20 ft 40 ft 80 ft 150 ft

Ground1 M/C 341 0.0041 0.0022 0.0013 0.0007 0.0004 2

Aerial2 M to C 341 0.0205 0.0142 0.0096 0.0053 0.0024 12

Table Notes:

M = medium spray nozzle, C = coarse spray nozzle, (M to C assumes a median droplet diameter of 341 μm) 1 Boom height = 4.2 ft, 2 boom height = 10 ft, wind speed = 10 mph, spray volume 3 gal/A

3 Distance to LOC of 0.4 which equates to an application rate of 0.019 lb a.i./A for CLOSERTM based on a 48-h acute 

contact LD50 of 0.130 μg a.i./bee for (MRID 47832419) and a contact dose of 2.7 μg a.i./bee per 1 lb a.i./A.

Based on the acute contact toxicity of CLOSERTM, the acute risk LOC is met at an application 

rate of 0.019 lb a.i./A. Using all of the application rates of CLOSERTM which exceed this rate, 

the distance from the field edge where the acute risk LOC of 0.4 would be exceeded was 

determined using AgDRIFT (Table 3). The other formulated product (TRANSFORMTM) is

roughly 50% less toxic on an acute contact exposure basis than CLOSERTM; therefore, the 

distances at which the acute contact risk LOC is exceeded will be shorter than those shown in 

Table 4 for CLOSERTM.

Table 4. Distance from the Treated Field Where the Acute Risk LOC (Contact Exposure) is Exceeded for 

Various Application Rates of Sulfoxaflor as Determined by AgDRIFT

Method Droplets Dv0.5 

(μm)

Distance From Field Edge Where the Acute Contact Risk LOC

is Exceeded3 (ft)

0.023 lb ai/A 0.043 lb ai/A 0.07 lb ai/A 0.09 lb ai/A

Ground1 M/C 341 <1 <1 2 2

Aerial2 M to C 341 <1 <1 5 12

Table Notes:

M = medium spray nozzle, C = coarse spray nozzle, (M to C assumes a median droplet diameter of 341 μm) 1 Boom height = 4.2 ft 2 Boom height = 10 ft, wind speed = 10 mph, spray volume 3 gal/A 3 Distance (round to nearest ft) to LOC of 0.4 which equates to an application rate of 0.019 lb a.i./A for 

CLOSERTM based on a 48-h acute contact LD50 of 0.130 μg a.i./bee for (MRID 47832419) and a contact dose of 

2.7 μg a.i./bee per 1 lb a.i./A..

4.4 Off-Field Risk (Contact With Residues On Foliage)

Bees may come into dermal contact with pesticide residues that have deposited onto foliage 

when they are foraging on attractive plants adjacent to the treated field. For sulfoxaflor, data are 
9

available from two studies that examined the toxicity of residues on treated foliage. These 

studies were conducted according to the Office of Chemical Safety and Pollution Prevention 

(OCSPP) test guideline 850.3020, as summarized in the previous Section 3 risk assessment

(D382619). The toxicity of residues on foliage studies assess the toxicity of aged residues on 

treated alfalfa. Based on aged residues of the CLOSERTM formulation (GF-2032-SC) on alfalfa 

after application at 200 g/ha (0.18 lb a.i./A), less than 5% mortality occurred following 3 to 24 

hours of exposure (MRID 47832420). With the TRANSFORMTM formulation (GF-2372-WG) at 

the same application rate, up to 15% mortality occurred following exposure to alfalfa aged from 

3-24 hours (MRID 47832512). Collectively, these studies suggest that aged residues of these 

two sulfoxaflor formulations result in low mortality to honey bees via dermal contact with 

treated foliage, i.e., the compounds exhibit low “residual toxicity”. It is further noted that the 

application rate used in these studies (0.18 lb a.i./A) is double the maximum single application 

rate of sulfoxaflor proposed for this registration (0.09 lb a.i./A). 

4.5 Off-Field Risk from Oral Exposure (Pollen and Nectar)

Bees may also become exposed to sulfoxaflor which has been deposited on (or translocated into)

pollen and nectar of blooming plants adjacent to treated fields. In order to provide an estimate of 

the potential oral exposure of bees to sulfoxaflor when foraging on plants adjacent to treated 

fields, AgDRIFT (version 2.1.1) was run as described previously in Table 4 for the acute contact 

exposures. Based on this AgDRIFT modeling and default (high end) estimates of exposure for 

adult nectar foragers (the highest exposed type of honey bee), the acute risk LOC is exceeded 

from 16 to 361 feet beyond the edge of the treated field, depending on the application rate and 

application method (Table 5). Since these RQ values exceed the LOC using default (high end) 

exposure assumptions, they are refined further in Section 5 using available information on 

residues of sulfoxaflor in pollen and nectar of applicable crops.

Table 5. Distance from the Treated Field Edge Where the Acute Risk LOC Is Exceeded for Adult Nectar 

Foragers (Default, Oral Exposure) as Determined Using AgDRIFT

Method Droplets Dv0.5 

(μm)

Distance From the Treated Field Edge Where the Acute 

Contact Risk LOC is Exceeded3 (ft)

0.023 lb ai/A 0.043 lb ai/A 0.07 lb ai/A 0.09 lb ai/A

Ground1 M/C 341 16 36 66 89

Aerial2 M to C 341 135 210 295 361

Table Notes:

M = medium spray nozzle, C = coarse spray nozzle (M to C assumes a median droplet diameter of 341 μm) 1 boom height = 4.2 ft;; 2 boom height = 10 ft, wind speed = 10 mph, spray volume 3 gal/A; 3 distance (round to nearest ft) to LOC of 0.4 which equates to 0.0007 lb ai/A for default (high end) oral 

exposure.
10

5. Refined Tier 1 Risk Assessment 

The Tier 1 risk assessment summarized in Section 4 reflects default assumptions of exposure 

estimates of honey bees to the pesticide. By design, the initial Tier 1 risk assessment reflects 

simplified, high end estimates of exposure in order to quickly identify uses which pose minimal 

risk to bees. However, LOC exceedances that are based on the default (high end) estimates of 

exposure in Section 4 do not necessarily mean that risk will occur. In such cases, refinement of 

default estimates of exposure may be conducted using more realistic estimates of exposure that 

reflect the residues from actual use patterns of the chemical. Acute contact risks are based on the 

highest measured value of acute contact exposure reported for honey bees in various field trials

based on the work of Koch and Weisser (1997)5

. Currently, EPA does not have standard 

methods for refining screening-level acute contact exposure estimates. For oral exposure, 

refinement of Tier 1 risk estimates is possible based on consideration of different bee castes and 

tasks (each differing in their nectar and pollen consumption rates) and consideration of measured 

values of pesticide residues in pollen and nectar. Section 5.1 presents the findings of the refined 

on-field and off-field risk estimates for acute, oral exposure of bees to sulfoxaflor. As previously 

discussed, acceptable Tier 1 toxicity data are not available from which to estimate chronic 

toxicity of sulfoxaflor to adult or larval honey bees. The uncertainty associated with this lack of 

data is characterized in Section 4.

5.1 Off-Field Risk from Oral Exposure (Refined)

For sulfoxaflor, pollen and nectar residue data are available from multiple studies including a 

field residue study with cotton (MRID 48755606), pumpkin (MRID 48755601), and Phacelia

(MRID 48446601 and 48445806). Maximum reported residues of sulfoxaflor in various plant 

and hive matrices are shown in Table 6. Among the available residue studies, the highest 

residues reported in pollen and nectar resulted from the cotton study. Furthermore, the cotton 

study also included measurements made directly from foraging bees (i.e., pollen collected by 

bees) returning to the hive, which is considered a more representative measure of exposure of 

honey bee colonies compared to the other matrices (e.g., pollen collected directly from flowers)

in which residues were measured. For these reasons, the residue values measured in pollen and 

nectar from foraging bees in the cotton study were considered most appropriate among the 

available data for further refining the estimates of oral exposure of bees to sulfoxaflor. Details of 

these studies are provided in the previous Section 3 risk assessment (D382619). 

 5 Koch, H. and P. Weisser. 1997. Exposure of honey bees during pesticide application under field conditions. 

Apidologie, 28: 439-447.
11

Table 6. Maximum Reported Residues (ppm) of Sulfoxaflor in Plant and Hive Materials from Various 

Field Studies

Application 

Rate (lb 

a.i./A)

Plant 

Pollen

Plant 

Nectar

Plant 

Tissue

Forager 

Nectar*

Forager 

Pollen*

Comb 

Pollen

Comb 

Larvae MRID

Cotton

1 x 0.045 1.26 0.13 0.22 0.03 <0.01

2 x 0.045 2.54 0.05 0.83 0.04 0.01 48755606

2 x 0.089 6.66 0.07 2.78 1.19 0.03

2 x 0.134 c 2.61 1.01 2.23 0.04 0.08

Phacelia

1 x 0.021 0.52b 0.05 0.29 48446601

1 x 0.043 1.48b 0.09 0.81

Phacelia

1 x 0.006 0.06a

48445806

1 x 0.012 0.04a

1 x 0.021 1.76b 0.61a

1 x 0.045 0.23a

1 x 0.088 1.01a

Pumpkin

1 x 0.022 0.08 0.03 0.20b 48755601

1 x 0.089 0.38 0.03 1.27b

a Samples taken 7 days after treatment rather than immediately after treatment

b Whole plant samples in study MRID 48446601, flower samples in study MRID 48445806, leaf tissue in study 

MRIID 48755601.

c Not considered in the current risk assessment since the single application rate (0.134 lb a.i./A) exceeds the 

maximum single rate for the proposed Section 3 (0.09 lb a.i./A).

* Used for refining default estimates of oral exposure of bees to sulfoxaflor. Shaded cells indicate no data are 

available for the applicable matrix.

For the three treatments from the cotton residue study that correspond to currently proposed label 

rates summarized in Table 6 (1 x 0.045, 2 x 0.045 and 1 x 0.089 lb a.i./A), a total of 132 

individual samples of forager-collected pollen and nectar (66 paired samples) were obtained 

during the 10-day exposure during which time the hives remained in the tunnels (Table A-1, 

Appendix A). For each of these 66 paired samples of residues in pollen and nectar, an acute oral 

RQ value was calculated based on consumption rates for adult nectar foragers (highest nectar 

exposure) and adult nurse bees (highest pollen exposure). Of the 132 acute RQ values 

calculated, only 4 exceed the acute risk LOC of 0.4 (Table A-2, Appendix A). The highest acute 

oral RQ value determined from these paired residue values is 0.72 for adult nectar foragers (Day 

1, 1 x 0.045 lb ai/A treatment) and 0.72 for nurse bees (Day 0, 2 x 0.089 lb ai/A treatment). 

These acute oral RQ values slightly exceed the acute risk LOC of 0.4. Notably, the maximum 

acute RQ value for larval bees (0.08) does not exceed the acute risk LOC. 

However, these RQ values assume that bees are foraging on the treated field, which is not 

expected to occur. Therefore, AgDRIFT modeling was conducted to estimate the distance from 

the treated field where the acute risk LOC of 0.4 would be exceeded. Bees may be foraging near 

the edges of these fields due to the presence of weeds or other attractive plants. The maximum 
12

acute oral RQ of 0.72 was assumed to occur at the edge of the treated field. To estimate the 

corresponding reduction in this RQ as a function of distance from the treated field, this RQ was 

multiplied by the proportion of the on-field application rate estimated using AgDRIFT at various 

distances from the treated field edge (see Table 3) for each of the modeling scenarios. The 

results, shown in Table 7, indicate that the acute, oral RQ values for adult bees are below the 

acute risk LOC of 0.4 at less than 1 foot from the edge of the treated field regardless of 

modeling scenario chosen. Notably, the spatial extent to which the acute oral RQ may be 

exceeded adjacent to the treated field appears to be very small relative to the spatial extent of 

floral resources that would likely be available to bees further away from the treated field. 

Table 7. Refined Tier 1 Acute, Oral RQ Values for Honey Bees at Varying Distances Off the Treated 

Field

6. Tier 2 Risk Characterization

The Tier 2 characterization of pesticide risks to bees involves evaluating effects of the pesticide 

on the entire colony. This is important to risk assessment because effects at the individual level 

may not result in similar (if any) effects at the colony level. In addition, evaluating effects at the 

colony level integrates multiple mechanisms by which a toxicant can affect the proper 

functioning of a colony (e.g., behavior abnormalities, navigation, and learning) which may not be 

indicated by individual-level effects data.

As described previously, no acute or chronic risks are expected on the treated fields because of 

lack of exposure based on the lack of crop attractiveness to bees, agronomic practices and label 

restrictions for application only after the bloom period. However, there was exceedance of the 

acute risk LOC of 0.4 at short distances beyond the treated field (up to 12 feet for contact

exposure and about 1 foot for oral exposure) for adult bees. 

Based on label information described earlier, the predicted spray drift application rate of 

sulfoxaflor at 10 feet beyond the field margin would range from 0.005 lb a.i./A (assuming 0.023 

lb a.i./A applied on the field) to 0.021 lb a.i./A (assuming 0.09 lb a.i./A applied on the treated 

field). Furthermore, there would be an expected exponential decline in these application rates 

with increasing distance from the treated field (Table 4). 

Method Droplets Dv0.5 

(μm)

Refined Maximum Acute Oral RQ at Varying 

Distances from the Treated Field 

Distance From the 

Treated Field Edge 

Where the Acute Oral

Risk LOC is 

Exceeded3 (ft)

10 ft 20 ft 40 ft 80 ft 150 ft

Ground1 M/C 341 0.03 0.02 0.01 0.01 0.00 < 1

Aerial2 M to C 341 0.16 0.11 0.08 0.04 0.02 < 1

Table Notes:

M = medium spray nozzle, C = coarse spray nozzle, (M to C assumes a median droplet diameter of 341 μm) 1 boom height = 4.2 ft

2 boom height = 10 ft, wind speed = 10 mph, spray volume 3 gal/A

3 distance (rounded to nearest ft) to LOC of 0.4 which equates to an estimated drift fraction of 56% beyond the 

field edge (i.e., a 56% reduction of the refined on-field RQ of 0.72). 
13

As described in the previous Section 3 risk assessment, a total of 6 Tier 2 semi-field (tunnel) 

studies were submitted as part of the original new chemical registration. In these studies, effects 

observed on mortality, flight activity and behavioral abnormalities were short-lived (3 days or 

less). No sustained effects were observed on parameters such as forager mortality, flight 

activity, behavior abnormalities and hive strength at the application rates predicted at 10 feet or 

more beyond the field margin. It is noted that the application rates predicted within 10 feet of 

the field margin are at the low end of the rates evaluated in the submitted Tier 2 semi-field 

studies and rates at 20 feet are typically below the tested rates. Therefore, exposure considered in 

the Tier 2 tunnel studies are most applicable to regions immediately adjacent to the downwind 

portion of the treated field margin. Short-term effects on brood were not evident compared to 

controls; however, due to deficiencies in the study execution and/or design, the potential effects 

on brood over longer-time periods could not be conclusively determined. 

7. Ecological Incident Reports

According to EPA’s Ecological Incident Information System, one ecological incident was 

reported to EPA on 1/2/2014 that purportedly involved three insecticides: acephate, 

dichrotophos, and sulfoxaflor. A beekeeper in Dunklin County, MO stated from June through 

August, crops (including watermelon) were treated with pesticides, including Bidrin

[dichrotophos], acetate, and sulfoxaflor as well as tank mixes of a variety of chemical products. 

The beekeeper reported that over 1,000 hives were affected by the pesticide use, which is listed 

as “incapacitation” in the EIIS database. There is no information on how many other pesticides 

may have been use, the legality of the use, the timing of pesticide application, presence or 

absence of other potential stressors (e.g., Varroa, Nosema) or data confirming that pesticide 

exposure actually occurred (e.g., residues of pesticides in bees or the hive). Use of the pesticides 

was not confirmed independently. Given the limited information associated with this incident 

report and the apparent application of multiple pesticides, linking these reported effects to any 

one pesticide is not possible. No other incidents potentially associated with sulfoxaflor use over 

the past several years (either from Section 18 emergency uses on cotton, sorghum, alfalfa or 

from the previously registered Section 3) have been reported to the Agency. 

8. Environmental Persistence of Sulfoxaflor in Bee Relevant 

Matrices 

In addition to the spatial scale associated with off-field risks to bees described earlier (e.g., 12 

feet or less beyond the field edge for acute risk), it is also important to consider the temporal 

scale of risks (i.e., how long bees may be exposed to sulfoxaflor). To characterize the temporal 

scale of risk, available data were evaluated on how long it takes for sulfoxaflor residues in pollen 

and nectar to dissipate. Specifically, dissipation half-life values (DT50) were determined for 

sulfoxaflor residues measured in pollen and nectar from the cotton tunnel study (Table 8 and 

Figure 1). The median and 90th percentile DT50 values of sulfoxaflor in cotton pollen and nectar 

are 2.3 and 8.6 days, respectively. These values indicate that sulfoxaflor has a relatively short 

persistence in cotton pollen and nectar.
14

Table 8. Compilation of dissipation half-life values for sulfoxaflor in cotton pollen and nectar

Application Number 1 Application Rate (lb a.i./A) DT50 (days)

Pollen Collected From Plants

1 0.045 < 1

1 0.045 3.3

2 0.045 1

1 0.089 1.3

2 0.089 2.5

1 0.134 n.d.

2 0.134 5.5

Pollen Collected from Forager Bees

1 0.045 4

1 0.045 2.6

2 0.045 1.7

1 0.089 2.3

2 0.089 11.6

1 0.134 1.2

2 0.134 69

Nectar Collected From Forager Bees

1 0.045 2.1

1 0.045 2.1

2 0.045 1.7

1 0.089 2

2 0.089 6.6

1 0.134 8.3

2 0.134 6.9

1 Number refers to the first or second consecutive application (MRID 48755606)
15

Figure 1. Cumulative frequency of DT50 values for sulfoxaflor in cotton pollen and nectar (MRID 

48755606)

Although these data are for only one crop, a similar rapid decline in sulfoxaflor residues is 

observed in Phacelia pollen and nectar (MRID 48476601) where approximately 10% of the 

residues measured on day 0 remained by day 6. DT50 values were not determined because only 

three measures were available over time (days 0, 5 and 6). 

9. Uncertainty Associated with Lack of Tier 1 Chronic Data for 

Bees 

Although the potential for chronic (Tier 1) risks to individual bees foraging immediately adjacent 

to treated fields is not known due to lack of chronic adult Tier 1 data, a bounding analysis was 

conducted to estimate the uncertainty associated with lack of chronic toxicity data. This 

bounding analysis relies on the use of “acute-to-chronic ratios” (ACRs) derived from other 

nicotinic acetylcholine receptor (AChR) agonists to estimate a chronic No Observed Adverse 

Effect Level (NOAEL) for adult bees. The ACR is determined as the ratio of the acute oral LD50

to the chronic oral NOAEC for adult bees. Data for AChR agonists are considered most 

applicable to sulfoxaflor given similarities in the mode of action in insects.

Currently, data from which to derive ACRs for oral exposure of adult bees with AChR agonists 

are available for imidacloprid, clothianidin, and flupyradifurone (Table B-1 of Appendix B). 

The calculated ACR values are 24.4 (imidacloprid), 10.3 (clothianidin) and 2.6 (flupyradifurone) 

with an overall mean ACR of 12.4. Using a mean ACR value of 12.4, a “central tendency” 

estimate of 0.0041 μg a.i./bee/d was determined the adult chronic oral NOAEL. Using the 

maximum ACR of 24.4, an adult chronic oral NOAEL of 0.0021 μg a.i./bee/d was determined 

and was subsequently used for calculating an “upper bound” estimate of chronic risk.
16

The estimated NOAEL of 0.0021 and 0.0041 μg a.i./bee/d were used to calculate upper bound 

and central tendency estimates of chronic Tier 1 risks, respectively, to adult nurse bees and 

nectar foragers. Nurse bees and nectar foragers consume the largest amounts of pollen and 

nectar, respectively, and would provide the greatest estimates of risk. Using each set of daily 

average concentrations sulfoxaflor in cotton pollen and nectar (Table A-1 of Appendix A)

combined with the estimated NOAEL of 0.0021 μg a.i./bee/d, maximum chronic oral RQ values 

of 10.0 (nurse bees) and 8.8 (nectar foragers) are calculated as upper bound estimates of risk6

Similarly, using the mean estimated NOAEL of 0.0041 μg a.i./bee/d and the same set of residue 

data, maximum chronic oral RQ values of 5.1 (nurse bees) and 4.5 (nectar foragers) are 

calculated as central tendency estimates of risk.

However, these chronic oral RQ values assume that bees are foraging on the treated field, which 

is not expected to occur. Therefore, AgDRIFT modeling was conducted to estimate the distance 

from the treated field where the chronic risk LOC of 1.0 would be exceeded. The maximum 

chronic RQ values described previously were assumed to occur at the edge of the treated field. 

To estimate the corresponding reduction in these RQ values as a function of distance from the 

treated field, each RQ was multiplied by the proportion of the on-field application rate estimated 

using AgDRIFT at various distances from the treated field edge (see Table 3) for each of the 

modeling scenarios. This analysis indicates that the potential for chronic (Tier 1) oral risks bees 

foraging adjacent to the treated fields would extend from 2-14 feet beyond the treated field 

assuming a central tendency estimate of the chronic oral NOAEL (Tables B-2 and B-3 of 

Appendix B) and label restrictions on ground and aerial application. Potential chronic oral risks 

to adult bees would extend from 4-46 feet beyond the treated field assuming the lower estimate 

of the chronic NOAEL (0.0021 μg a.i./bee/d; Tables B-4 and B-5 of Appendix B). 

Although not without important caveats, this bounding analysis suggests that chronic Tier 1 risks 

may be of concern over a relatively small distance beyond the treated (2-46 feet, depending on 

modeling and toxicity assumptions). Importantly, the use of an ACR value to estimate chronic 

NOAEL introduces uncertainty into the risk estimate due to the considerable variability observed 

in the ACR values (range: 2.6 to 24.4). However, this bounding analysis is also considered 

highly conservative because it assumes that bees would obtain 100% of their diet from the 

relatively narrow contaminated area beyond the treated fields. Furthermore, the duration of 

exposure is likely to be relatively short based on the relatively short persistence of sulfoxaflor in 

pollen and nectar described previously.

10. Risk Assessment Conclusions, Assumptions, and Uncertainty 

In consideration of multiple lines of evidence described in the previous sections, the following 

risk conclusions are reached for bees.

 6 As indicated in the Agency’s recently published bee risk assessment with imidacloprid, use of daily average 

residues of pesticides is considered appropriate for estimating chronic Tier 1 risks to bees 

https://www.regulations.gov/#!docketBrowser;rpp=25;so=DESC;sb=postedDate;po=0;dct=SR;D=EPAHQ-OPP-2008-0844)
17

1. Acute and chronic risks on the treated field are not indicated. For all of the proposed 

uses, acute and chronic risks to bees are considered low for bees potentially foraging on 

the treated field since significant exposure is not expected. Lack of exposure is presumed 

since crops are considered unattractive to bees, are harvested prior to bloom, or because 

applications are prohibited until after the bloom period of the crop. 

2. The spatial extent of acute risks beyond the treated field is very limited. For all of the 

proposed uses of sulfoxaflor, acute oral and contact risk to bees which may forage 

immediately adjacent to the treated field during (or shortly after) application is limited to 

<1 – 12 feet beyond the treated field. Therefore, a spray drift buffer of 12 feet would be 

expected to mitigate acute risk to bees that may be foraging in this zone adjacent to 

treated fields.

3. A bounding analysis suggests that estimated chronic risks are also spatially limited 

beyond the treated field. A bounding analysis using estimated values of chronic toxicity 

to adult bees suggests that chronic Tier 1 risks may be of concern over a relatively small 

distance beyond the treated (2-46 feet, depending on modeling and toxicity assumptions).

4. Temporal extent of acute and chronic risks beyond the treated field is limited. Data 

on the persistence of sulfoxaflor in pollen and nectar suggests that residues will degrade 

relatively quickly (90% of the half-life values are approximately 9 days or less and 50% 

are approximately 2 days or less). 

A number of assumptions and uncertainties are noted in the preceding risk assessment. These 

include:

1. Off-Field Diet/Forage Habitat. Off-field (Tier 1) risk assessment assumes that bees will 

be foraging in the spray drift zone adjacent to the treated field and that they obtain 100% 

of their diet from blooming plants in this zone. This assumption likely overestimates

exposure and off-field risk because plants will not always be in bloom, and when they are 

in bloom, not all plants will be attractive to bees. Furthermore, honey bees often forage 

opportunistically on a variety of forage sources across the landscape (up to 5 miles from 

the hive). 

2. Residue Profile in Pollen and Nectar. Refined risk estimates for oral exposure used for 

estimating on-field and off-field risks assume that residues of sulfoxaflor in pollen and 

nectar of flowering plants are equivalent to the maximum residues measured in pollen 

and nectar of cotton, which occurred within two days of foliar application. Among the 

three plant species for which residue data are available, the greatest residues in pollen and 

nectar were observed with cotton. Furthermore, foliar applications to cotton were made 

during the blooming period which would tend to maximize residues in pollen and nectar 

for this crop. Since not all plants inhabiting the acute and chronic spray drift zone beyond 

the field edge will be blooming, residues in non-blooming plants will be subject to 

dissipation prior to the bloom period which will lead to reduced residues during bloom

(median foliar dissipation half-life = 2.3 days). However, since the species of plant 

adjacent to the treated field cannot be predicted with certainty, it is possible that 
18

sulfoxaflor residues in cotton could be higher or lower than residues in blooming plants 

adjacent to the treated field immediately following pesticide application. 

3. Lack of Tier 1 Chronic Toxicity Data. No Tier 1 risk assessment was conducted to 

assess chronic exposures because acceptable chronic Tier 1 data are not available for 

sulfoxaflor for adult or larval bees. If sulfoxaflor has a similar toxicity profile as 

imidacloprid in terms to its ACR, then the chronic (Tier 1) risk could potentially extend 

to 46 feet beyond the treated field (aerial applications). If sulfoxaflor has a toxicity 

profile similar to the mean ACR of imidacloprid, clothianidin, and flupyradifurone, then 

chronic (Tier 1) risk could potentially extend up to 14 feet beyond the treated field. It is 

noted that OPP has only recently been requiring chronic Tier 1 bee toxicity data since the 

publication of its bee risk assessment guidance in 2014 as more reliable test protocols 

have been developed for such tests. 

11. Additional Recommended Data

Based on the proposed uses of sulfoxaflor, which are not expected to result in exposure of bees 

on the treated field and are expected to result in very limited off-field exposure, additional data 

pertaining to bees is not requested at this time. It is noted, however, that additional chronic Tier 

1 data would help to reduce uncertainty in the bounding analysis of spray drift for estimating 

chronic risk. These additional Tier 1 data (and possibly higher tier exposure and effects data) 

would likely be needed in the future in order to evaluate any new (proposed) uses of sulfoxaflor 

that result in significant exposure of bees. 
19

Appendix A

Forager-Collected Pollen and Nectar Residues of Sulfoxaflor and 

Associated Acute Oral RQs From the Cotton Tunnel Study (MRID 

48755606).
20

Table A-1. Forager-Collected Pollen and Nectar Residues from the Cotton Tunnel Study (MRID 

48755606) 

Application Rate

(lb a.i./A)

Forager-Collected Pollen

(μg ai/kg)

Forager-Collected Nectar

Day (μg ai/kg)

Pollen Nectar

H1 H2 Average H1 H2 Average

0.045 0 127.40 187.40 157.40 32.67 21.70 27.19

--- 1 122.00 144.80 133.40 126.40 1.51 63.96

--- 2 150.40 52.27 101.34 8.32 2.05 5.18

--- 3 222.30 81.86 152.08 5.00 0.64 2.82

--- 4 120.10 72.60 96.35 5.00 1.29 3.15

--- 5 102.40 33.68 68.04 16.05 0.28 8.16

--- 6 66.40 68.61 67.51 8.05 1.05 4.55

--- 7 18.66 37.63 28.15 3.95 0.82 2.39

--- 8 32.24 55.96 44.10 3.02 0.72 1.87

--- 9 29.88 58.37 44.13 1.93 0.07 1.00

--- 10 49.22 12.63 30.93 1.64 0.16 0.90

0.045 0 225.90 173.00 199.45 9.53 8.68 9.11

--- 1 124.10 224.50 174.30 21.21 16.68 18.95

--- 2 96.70 125.40 111.05 29.71 8.39 19.05

--- 3 143.80 271.50 207.65 15.51 11.23 13.37

--- 4 81.74 32.62 57.18 11.10 3.70 7.40

0.045 5 829.50 192.40 510.95 48.97 44.96 46.97

--- 6 229.10 296.00 262.55 26.46 14.38 20.42

--- 7 271.80 145.00 208.40 41.96 8.70 25.33

--- 8 84.01 146.90 115.46 14.63 7.09 10.86

--- 9 68.00 32.23 50.12 8.03 5.36 6.69

--- 10 55.89 83.13 69.51 6.28 4.55 5.41

0.089 0 2782.00 512.20 1647.10 73.78 2.52 38.15

--- 1 242.60 350.10 296.35 25.94 22.67 24.31

--- 2 250.80 298.60 274.70 11.89 19.33 15.61

--- 3 99.52 116.00 107.76 8.59 3.59 6.09

--- 4 191.90 102.60 147.25 3.94 16.96 10.45

0.089 5 796.60 1146.00 971.30 22.87 21.86 22.37

--- 6 393.60 400.00 396.80 21.97 33.65 27.81

--- 7 320.20 2262.00 1291.10 12.80 19.74 16.27

--- 8 255.20 371.30 313.25 8.85 31.46 20.16

--- 9 113.20 317.00 215.10 5.21 11.54 8.38

--- 10 117.80 1323.00 720.40 10.24 35.52 22.88

H1 = hive 1, H2 = hive 2 (two hives per tunnel); values in bold indicate the paired residue values that 

resulted in the highest acute oral RQ to nectar foragers and nurse bees
21

Table A-2. Acute oral RQ values calculated for Nurse Bees and Nectar Foragers Based on the Cotton 

Tunnel Study (MRID 48755606)

Application Rate

(lb a.i./A)

Nurse Bee 

Acute Oral RQ 

Nectar Forager 

Day Acute Oral RQ

H1 H2 H1 H2

0.045 0 0.11 0.09 0.19 0.12

--- 1 0.37 0.03 0.72 0.01

--- 2 0.05 0.02 0.05 0.01

--- 3 0.06 0.02 0.03 0.00

--- 4 0.04 0.02 0.03 0.01

--- 5 0.06 0.01 0.09 0.00

--- 6 0.03 0.02 0.05 0.01

--- 7 0.01 0.01 0.02 0.00

--- 8 0.01 0.01 0.02 0.00

--- 9 0.01 0.01 0.01 0.00

--- 10 0.01 0.00 0.01 0.00

0.045 0 0.07 0.06 0.05 0.05

--- 1 0.08 0.09 0.12 0.09

--- 2 0.10 0.05 0.17 0.05

--- 3 0.07 0.08 0.09 0.06

--- 4 0.05 0.02 0.06 0.02

0.045 5 0.29 0.16 0.28 0.26

--- 6 0.11 0.09 0.15 0.08

--- 7 0.16 0.05 0.24 0.05

--- 8 0.06 0.05 0.08 0.04

--- 9 0.03 0.02 0.05 0.03

--- 10 0.03 0.03 0.04 0.03

0.089 0 0.72 0.10 0.42 0.01

--- 1 0.12 0.13 0.15 0.13

--- 2 0.08 0.11 0.07 0.11

--- 3 0.04 0.03 0.05 0.02

--- 4 0.05 0.07 0.02 0.10

0.089 5 0.21 0.27 0.13 0.12

--- 6 0.13 0.17 0.12 0.19

--- 7 0.09 0.48 0.07 0.11

--- 8 0.07 0.15 0.05 0.18

--- 9 0.04 0.09 0.03 0.07

--- 10 0.05 0.34 0.06 0.20

H1 = hive 1, H2 = hive 2 (two hives per tunnel); RQ values in bold/shaded cells exceed the 

acute risk LOC of 0.4
22

Appendix B

Bounding Analysis of the Potential for Chronic (Tier 1) Oral Risks to 

Adult Bees
23

Table B-1. Data Considered for Estimation of the Adult Chronic Oral NOAEL for Sulfoxaflor. 

Chemical (IRAC 

Class) [ACR]

Structure MW 

(g/mol)

Kow Vapor 

Pressure

Aerobic 

Soil 

DT50

Acute & Chronic 

Adult Endpoints1

Sulfoxaflor

(4C)

277 6 Low Rapid 

(2-8 d)

LD50 =0.0515 μg 

ai/bee/d (MRID 

47832417)

Estimated Chronic 

NOAEL = 0.0021 -

0.0041 μg 

ai/bee/d 

(using Max ACR 

of 24.4 and mean 

ACR of 12.4, 

respectively)

Imidacloprid

(4A)

(ACR=24.4)

255 3.7 Low 200 d to 

> 1 yr

LD50 =0.0039 μg 

ai/bee/d (MRID 

42273003)

Chronic NOAEL = 

0.00016 μg

ai/bee/d (MRID

49750601) 

Clothianidin

(4A)

(ACR =10.3)

250 1.1 Low > 1 year LD50 =0.0037 μg 

ai/bee/d (MRID

45422426)

Chronic NOAEL = 

0.00036 μg 

ai/bee/d (MRID

48414901)

Flupyradifurone

(4D)

(ACR = 2.6)

288 1.2 Low 35 d- >1 

yr

LD50 =1.2 μg 

ai/bee/d (MRID

48843722)

Chronic NOAEL = 

0.464 μg ai/bee/d 

(MRID 48843762)
24

Table B-2. Upper Bound Estimates of Chronic (Tier 1) Risks to Adult Nurse Bees

Method Droplets Dv0.5 

(μm)

Upper Bound Chronic RQs for Nurse Bees @ spray drift 

distances from the field edge Distance to 

chronic LOC 3 10 ft 20 ft 40 ft 80 ft 150 ft

Ground1 M/C 341 0.46 0.25 0.15 0.08 0.06 5

Aerial2 M to C 341

2.3 1.6 1.1 0.59 0.27 46

Table Notes:

M = medium spray nozzle, C = coarse spray nozzle, (M to C assumes a median droplet diameter of 341 μm)

1 boom height = 4.2 ft, On-Field Chronic RQ of 10.0 estimated using max. ACR of 24.4

2 boom height = 10 ft, wind speed = 10 mph, non-volatile rate 0.09 lb a.i./A, spray volume 3 gal/A

3 distance to LOC of 1.0 which equates to a 10% drift fraction based on a maximum estimated chronic oral RQ of 

10.0 for nurse bees with an estimated chronic adult NOAEL of 0.0021 ug a.i./bee/d.

Table B-3. Upper Bound Estimates of Chronic (Tier 1) Risks to Adult Nectar Foragers

Method Droplets Dv0.5 

(μm)

Upper Bound Chronic RQs for Nectar Foragers @ spray drift 

distances from the field edge s Distance to 

chronic LOC 3 10 ft 20 ft 40 ft 80 ft 150 ft

Ground1 M/C 341 0.40 0.22 0.13 0.07 0.05 4

Aerial2 M to C 341

2.0 1.4 0.94 0.52 0.24

35

Table Notes:

M = medium spray nozzle, C = coarse spray nozzle, (M to C assumes a median droplet diameter of 341 μm)

1 boom height = 4.2 ft, On-Field Chronic RQ of 5.1 estimated using max. ACR of 24.4

2 boom height = 10 ft, wind speed = 10 mph, non-volatile rate 0.09 lb a.i./A, spray volume 3 gal/A

3 distance to LOC of 1.0 which equates to an 11.3% drift fraction based on a maximum estimated chronic oral 

RQ of 8.8 for nectar foragers with an estimated chronic adult NOAEL of 0.0021 ug a.i./bee/d.

Table B-4. Central Tendency Estimates of Chronic (Tier 1) Risks to Adult Nurse Bees

Method Droplets Dv0.5 

(μm)

Central Tendency Chronic RQ for Nurse Bees @ spray drift 

distances from the field edge Distance to 

chronic LOC 3 10 ft 20 ft 40 ft 80 ft 150 ft

Ground1 M/C 341 0.23 0.13 0.07 0.04 0.03 2

Aerial2 M to C 341

1.2 0.80 0.54 0.30 0.14 14

Table Notes:

M = medium spray nozzle, C = coarse spray nozzle, (M to C assumes a median droplet diameter of 341 μm)

1 boom height = 4.2 ft, On-Field Chronic RQ of 4.5 estimated using max. ACR of 24.4

2 boom height = 10 ft, wind speed = 10 mph, non-volatile rate 0.09 lb a.i./A, spray volume 3 gal/A

3 distance to LOC of 1.0 which equates to a 19.6% drift fraction based on a maximum estimated chronic oral RQ 

of 5.1 for nurse bees with an estimated chronic adult NOAEL of 0.0041 ug a.i./bee/d.
25

Table B-5. Central Tendency Estimates of Chronic (Tier 1) Risks to Adult Nectar Foragers

Method Droplets Dv0.5 

(μm)

Central Tendency Chronic RQ for Nectar Foragers @ spray drift 

distances from the field edge Distance to 

chronic LOC 3 10 ft 20 ft 40 ft 80 ft 150 ft

Ground1 M/C 341 0.21 0.11 0.07 0.04 0.03 2

Aerial2 M to C 341

1.0 0.71 0.48 0.27 0.12 11

Table Notes:

M = medium spray nozzle, C = coarse spray nozzle, (M to C assumes a median droplet diameter of 341 μm)

1 boom height = 4.2 ft, On-Field Chronic RQ of 10.0 estimated using max. ACR of 24.4

2 boom height = 10 ft, wind speed = 10 mph, non-volatile rate 0.09 lb a.i./A, spray volume 3 gal/A

3 distance to LOC of 1.0 which equates to a 22% drift fraction based on a maximum estimated chronic oral RQ of 

4.5 for nectar foragers with an estimated chronic adult NOAEL of 0.0041 ug a.i./bee/d.