OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION

 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

 

PC Code: 024875 

MEMORANDUM DP Barcode: 427622 

DATE: June 26, 2015 

SUBJECT: Response to the Initial 60-Day Public Comment on: “Registration Review: 

Draft Problem Formulation for Environmental Fate, Ecological Risk, 

Endangered Species, and Human Health Drinking Water Exposure Assessments 

for Spiromesifen (2/20/15; PC Code 024875; DP Barcode 422437)” 

TO: Jolene Trujillo, Chemical Review Manager 

Jill Bloom, Team Leader 

Linda Arrington, Branch Chief 

Risk Management and Implementation Branch 5 (RMIBV) 

Pesticide Re-evaluation Division (7508P) 

FROM: Karen Milians, Ph.D., Chemist 

 Andrew Sayer, Ph.D., Biologist 

 Environmental Risk Branch IV 

 Environmental Fate and Effects Division 

 Office of Pesticide Programs 

REVIEWED 

BY: Jim Carleton, Ph.D., Senior Scientist

 Catherine Aubee, Senior Scientist 

 Environmental Risk Branch IV 

 Environmental Fate and Effects Division 

 Office of Pesticide Programs 

APPROVED 

BY: Jean Holmes, DVM, MPH, Branch Chief 

 Environmental Risk Branch IV 

 Environmental Fate and Effects Division 

 Office of Pesticide Programs 

The Environmental Fate and Effects Division (EFED) has reviewed the public comments on the 

Preliminary Work Plan for Registration Review of spiromesifen, including the draft problem 
Page 2 of 3 

formulation1

 for environmental fate, ecological risk, endangered species and human health 

drinking water exposure assessments. Comments were received from Bayer Crop Science and a 

specific comment is addressed in this response. 

In the following section, the specific comment is summarized in italics and is then followed by 

EFED’s response. 

1. Environmental Safety (page 3): 

a) “ Bayer comment : Bayer has additional reports to submit to EPA See appendix 2. 

1. Formulation study, Green algae. EPA Guideline 850.5400. 

2. Formulation study, Lab study with Bombus terrestris (L). EPA Guideline 850.SUPP. 

3. Formulation study, Aquatic field study; Freshwater microcosm. EPA Guideline 

850.1950” 

EFED’s response: 

 EFED acknowledges Bayer’s intention to submit additional reports and will review the 

submission when it is received. 

2. Environmental Safety (page 3: 

b) “The trout ELS (MIRO 45819627) will be amended to include these endpoints. Bayer 

looked into the raw data and the time to hatch and time to swim up data was collected. It 

is unclear how it was omitted from the final report. Bayer is working with the contract 

lab to amend the report and it will be submitted to EPA in 2015.” 

EFED’s response: 

 EFED acknowledges Bayer’s intention to submit additional data on time-to-hatch and 

time-to-swim up and will review the amended report when it is submitted. 

3. Drinking Water (page 4):

a) “BCS considers the total toxic residues (TTR) method previously used by EFED for 

groundwater exposure assessment to be a very conservative screening level type 

approach. In the recent assessments EFED used the lumped DT50 for parent and three 

metabolites along with the Koc of the least soring compound to calculate exposure to 

groundwater. As a refinement option BCS asks EPA to use environmental fate endpoints 

of individual components of the residue of concern (DT50, Koc, formation rate in soils 

studies for each compound separately) in exposure modeling with PRZM-GW to 

calculate concentrations of individual components of the residue and to sum up 

subsequently to obtain realistic worst-case exposure concentration of the TTR.” 

EFED’s response: 

Assumptions employed in drinking water modeling are intentionally conservative in the face of 

data uncertainty and natural variability, and the agency’s regulatory mandate to minimize what 

might be thought of as “type II” or false-negative errors (e.g., failing to detect a problem where 

																																																																		 1 US EPA 2015 Registration Review: Draft Problem Formulation for Environmental Fate, Ecological Risk, and Endangered Species, and Human 

Health Drinking Water Exposure Assessments for Spiromesifen (PC Code 024875; DP Barcode 427622). From: A. Sayer and K. Milians,

Environmental Fate and Effects Division; To: J. Bloom and J. Stokes, Pesticide Re-evaluation Division; 02/20/2015.
Page 3 of 3 

one actually exists) at the expense of type I or false-positive errors. Unfortunately sufficient fate 

information is not currently available to permit modeling of spiromesifen degradates as separate, 

individual entities (degradation studies using the residues of concern as test materials are not 

available). The total toxic residue approach was thus used instead, to represent summed residues 

of concern in ground and surface water. Refinements to this approach may be considered in the 

future, subject to availability of the necessary fate information (degradation rates, sorption 

coefficients) on individual degradates.