December 1, 2014 

Russell Wasem 

Document Processing Desk (DCI/PRD) 

Office of Pesticide Programs 

U.S. Environmental Protection Agency 

One Potomac Yard 

2777 S. Crystal Drive 

Arlington, VA 22202 

Subject: Federal Register, Vol. 79, No. 146; Wednesday July 30, 2014 (Page 44169) 

Preliminary Risk Assessments for Dicrotophos 

EPA-HQ-OPP-2008-0440 

Dear Mr. Wasem, 

AMVAC Chemical Corporation (AMVAC) is submitting these comments in response to US EPA's 

recently released Preliminary Risk Assessment for dicrotophos. AMVAC is the data owner and 

only holder of a technical registration in the US. Additionally, AMVAC holds end use 

registrations and will be defending the use of the product here in the US. We appreciate the 

opportunity to provide additional information and comments to the Agency and look forward 

to discussing the next steps after the Agency has had a chance to review all the comments 

submitted to the docket. 

Dicrotophos is a critical tool for US cotton growers to control pests that would otherwise 

destroy their crop. The National Cotton Council reports that the annual economic activity 

generated by cotton and its products in the U.S. economy is estimated to be in excess of $120 

billion. As pest management issues evolve in cotton, growers need tools that are not only 

effective but also augment their Integrated Pest Management (I PM) and Integrated Resistance 

Management (IRM) programs, and provide a positive economic return. Please see attached 

report (Appendix 1) for a more detailed reporting of the benefits of dicrotophos use in cotton. 

The Agency's Preliminary Risk Assessment addresses several different exposure scenarios but 

we have focused on those the Agency identified as potentially concerning- aggregate riskspecifically drinking water and ecological risk. With respect to drinking water and aggregate 

risk, AMVAC is providing in an attachment specific and general comments concerning the 

Agency's drinking water and aggregate risk assessments (Appendix 2). Our submission focuses 

on the dietary consumption of surface-based drinking water, which has been shown to drive 

the aggregate risk assessment. The acute aggregate risk is acceptable at the 95th percentile for 

all subpopulation groups and information contained in this report indicates that exposure levels 

are likely lower than that calculated by the baseline PRZM/GW modeling reported by the 

Agency. The sub-chronic aggregate risk calculated through Calendex is based on a 21 day 

4695 MacArthur Court, Suite 1200, Newport Beach, CA, 92660 · Phone (949) 260-1200 
steady state exposure period. At the 95th percentile, the Agency calculated sub-chronic-based 

exceedances for certain sub population groups. By applying sensitivity analysis to several 

environmental fate parameters, it can be shown that these exceedances can be reduced 

significantly to levels that would not be of concern through refinement of these 

variables. Although additional modeling efforts may be useful, a substantive database of higher 

tier monitoring data is already available and can be conservatively applied to more accurately 

predict the 21 day average surface water exposure levels. Based on this assessment, there 

would be no sub-chronic exceedances of any of the population subgroups at the 95th 

percentile. On this basis, dicrotophos use on cotton does not pose an aggregate dietary risk of 

concern. AMVAC is continuing the analysis provided for in this document and intends to submit 

a more comprehensive assessment within 90 days of delivery of this response. 

With respect to ecological risk, AMVAC is providing in an attachment specific and general 

comments concerning the Agency's ecological risk assessment (Appendix 3). A review of 

ecological incident reports does not yield any findings of effects from the agricultural use of this 

product in cotton, which strongly suggests the label mitigation measures put in place during the 

RED, have adequately addressed ecological risk. The fact that cotton fields do not provide a 

good source of nutrition to animals is in itself some rationale as to why this use should not 

significantly affect wildlife. While there are some studies that have assessed the potential 

impact of dicrotophos to avian species, AMVAC's review of these studies has determined they 

are flawed in design and therefore do not provide any meaningful data. For this reason, the 

most accurate assessment of ecological risk must be performed using modeling. An 

examination of the baseline modeling reported by EPA has led to refinements based on free 

metabolic rate assessments for certain focal species. A refinement of the foliar dissipation 

default value is also justified in this report. From this effort, risk quotients are estimated to be 

less than 10 for all focal species. AMVAC is continuing the analysis provided for in this 

document and intends to submit a more comprehensive assessment within 90 days of delivery 

of this response. 

AMVAC has provided a response to EPA's aquatic risk assessment within our ecological risk 

assessment document. The EPA has determined that the risk to larger aquatic organisms is 

acceptable; but that there is a low level risk to invertebrates. It is our view that a higher tier 

assessment will demonstrate that the risk to these lower level species is also 

acceptable. AMVAC is continuing the analysis provided for in this document and intends to 

submit a more comprehensive assessment within 90 days of delivery of this response. 

There are some specific issues and corrections AMVAC wishes to address with respect to the 

Preliminary Risk Assessment: 

1. In the July 10, 2014 Transmittal of the Preliminary Environmental Fate and Ecological 

Risk Assessment for the Registration of dicrotophos (Case# 145), page 38 of 102, the 

Agency defines the 33-Day Fish Early Life Stage (ELS) Study (MRID 48482901) as 

"supplemental." Please see attached document (Appendix 4) to clarify the deficiencies 

cited in an effort to upgrade this study to "core." 

4695 MacArthur Court, Suite 1200, Newport Beach, CA, 92660 · Phone (949) 260-1200 
2. In the July 10, 2014 Transmittal of the Preliminary Environmental Fate and Ecological 

Risk Assessment for the Registration of dicrotophos (Case# 145), page 38 of 102, the 

Agency defines the 21-Day Chronic Flow-Through Toxicity Study (Daphnia Magna)(MRID 

44956501) as "supplemental." In May 2014, AMVAC submitted the inadvertent missing 

data from the specified Table 7 and this study should now be considered fully upgraded. 

3. In the July 10, 2014 Transmittal of the Preliminary Environmental Fate and Ecological 

Risk Assessment for the Registration of dicrotophos (Case# 145), page 45 of 102, the 

Agency defines the Tier I Seedling Emergence Study (MRID 48482902) as 

"supplemental." AMVAC will be submitting a document to clarify the deficiencies cited 

in an effort to upgrade this study to "core" within a couple of weeks. 

4. In the July 10, 2014 Memorandum for dicrotophos: Human Health Risk Assessment for 

Registration Review of dicrotophos, the Summary of Toxicological Doses and Endpoints 

and Points of Departure for dicrotophos (page 23 of 92), lists the MRID 4615205 for 

both the Acute Dietary and the Incidental Oral Single Day and it should be listed as MRID 

46153205. 

5. In the July 10, 2014 dicrotophos: Acute and Steady State Aggregate Dietary (Food and 

Drinking Water) Exposure and Risk Assessments to Support Registration Review, the 

Summary of Toxicological Doses and Endpoints for dicrotophos for use in Human Health 

Risk Assessments (page 6 of 20), the MRID for Acute Dietary is listed as 4615205 and 

should be listed as MRID 46153205. Next, on page 17 of 20 of this document, the active 

ingredient "coumaphos" is listed instead of dicrotophos on lines 1 and 2. Finally, 

Section VIII. Results/Discussion paragraphs (page 7) and Section IX. Characterization of 

Inputs/Outputs (page 17) do not match up with their associated charts. Per Russell 

Wasem, via email on August 7, 2014, we believe the charts to contain the correct 

information and the paragraph descriptions to contain incorrect data. 

Again, AMVAC appreciates the opportunity to provide these comments and additional 

information to the Agency and looks forward to the chance to discuss the next steps with the 

Agency. If there are any questions or issues with this response, I can be reached at 949-221-

6146 or via email at KrystaiJ@amvac-chemical.com. 

Kind regards, 

1\.~ Krystal Jenkins, Regulatory Product Manager 

AMVAC Chemical Corporation 

20141201.kj.dicrotophos risk assessment. us 

4695 MacArthur Court, Suite 1200, Newport Beach, CA, 92660 · Phone (949) 260-1200 
Volume 1 of 5- Submission Transmittal Document 

Name and Address of Submitter: 

AMVAC Chemical Corporation 

4695 MacArthur Court, Suite 1200 

Newport Beach, CA 92660 

Regulatory Action: 

Submission of Preliminary Risk Assessment Response for Dicrotophos 

Transmittal Date: 

December 1, 2014 

List of Submitted Studies· 

MRID Number Volume 

Number 

1 of 5 

2 of 5 

3 of 5 

4 of 5 

5 of5 

Company Name: 

Company Official: 

Company Contact: 

EPA Study Title 

Transmittal Document 

AMVAC November 2014 response to EPA's 

Preliminary Environmental Fate and Ecological 

Risk Assessment for the Registration of 

dicrotophos (Case# 145) 

Response to EPA's Preliminary Drinking Water 

Exposure and Acute and Steady State 

Aggregate Dietary Risk Assessments for 

Dicrotophos 

Response to EPA's Preliminary Environmental 

Date and Ecological Risk Assessment for 

Dicrotophos 

Response to the Data Evaluation Record on the 

Fish Early Life Stage Toxicity of Dicrotophos 

Technical to Fathead Minnow 

AMVAC Chemical Corporation 

Krys'tal Jenkins, Regulatory Product Manager 

Krystal Jenkins, Regulatory Product Manager 

949-221-6146 

KrystaiJ@amvac-chemical.com 

Guideline 

Number 

------------

4695 MacArthur Court, Suite 1200, Newport Beach, CA, 92660 ·Phone {949) 260-1200 
Appendix 1 
TITLE: 

AMVAC November 2014 response to EPA's Preliminary Environmental Fate and 

Ecological Risk Assessment for the Registration of dicrotophos (Case #145) 

Author: 

AMVAC Chemical Corporation 

Sponsor: 

AMVAC Chemical Corporation 

4695 MacArthur Court, Suite 1200 

Newport Beach, CA 92026 

Date: 

November 24, 2014 

Page 1 of 6 
NO CLAIM OF CONFIDENTIALITY 

No claim of confidentiality, on any basis whatsoever, is made for any information contained in 

this document. I acknowledge that information not designated as within the scope of FIFRA 

sec. lO(d)(l)(A),(BL or (C) on which pertains to a registered or previously registered pesticide is 

not entitled to confidential treatment and may be released to the public, subject to the 

provisions regarding disclosure to multinational entities under FIFRA lO(g). 

Submitter: Date: 

Typed name of signer: Jon C. Wood 

Director of Registrations 

Typed name of company: AMVAC Chemical Corporation 

Page 2 of6 
STATEMENT OF GLP COMPLIANCE 

This technical document provides information that assesses the benefits of use of dicrotophos. 

The document does not contain any new or original data. Therefore, the requirements of 40 

CFR Part 160 are not appropriate to this document. 

Author: Date: 

I • 

Typed name of signer: Krystal Jenkins 

Regulatory Product Manager 

Typed name of company: AMVAC Chemical Corporation 

Submitter/Sponsor: Date: 

()1-k-~1'/ I 

Typed name of signer: Jon C. Wood 

Director of Registrations 

Typed name of company: AMVAC Chemical Corporation 

Page 3 ofG 
AMVAC November 2014 response to EPA's Preliminary Environmental Fate and Ecological Risk 

Assessment for the Registration of dicrotophos (Case #145) 

AMVAC Chemical Corporation (AMVAC) is submitting this updated benefits analysis as part of our 

response to EPA's Preliminary Environmental Fate and Ecological Risk Assessment for the Registration of 

dicrotophos. These comments are the result of extensive discussions that we conducted with the 

National Cotton Council, University Extension Service personnel, cotton growers and other field experts 

and experienced users of dicrotophos. 

Dicrotophos is a critical product used by cotton growers across the United States to protect their crop 

from pests that would otherwise destroy the crop and/or significantly reduce yield. The National Cotton 

Council reports that the annual economic activity generated by cotton and its products in the U.S. 

economy is estimated to be in excess of $120 billion. As pest management issues evolve in cotton, 

growers need tools that are not only effective but also augment their Integrated Pest Management 

(IPM) and Integrated Resistance Management (IRM) programs, and provide a positive economic return. 

Dicrotophos remains an economical product to growers in times of high production costs and low cotton 

prices. Dicrotophos is a needed option for early season use to provide a foliar alternative to acephate 

for thrips control. Seed treated neonicotinoid insecticides have become a fairly standard treatment for 

growers. This is resulting in confirmed resistance of thrips to thiamethoxam in the mid-south states. 

This increases the need for foliar applied thrips control following seed treated insecticides. Acephate is 

not a preferred option because it has a tendency to flare spider mites while dicrotophos provides 

suppression of this pest. Options for early season control of spider mites are limited. 

In mid-to-late season cotton, the flexibility to manage plant bug and stink bug infestations after first 

bloom is critical since nationally these are two ofthe most damaging pests to cotton and ones with 

which dicrotophos has an excellent performance record. In addition to yield reduction, stink bugs cause 

further economic loss due to reduced lint quality so maintaining the use of Dictrophos is critical. 

Pest Pressure and Control 

For plant bug management programs, it is not uncommon to make eight to ten insecticide applications 

in a growing season. Other key active ingredients used are thiamethoxam, imidacloprid, acephate, 

oxamyl, sulfoxaflor and pyrethroids. Rotation of chemistry is critical to IRM. Dicrotophos has an 

excellent fit after first bloom stage of growth and works well in the rotation plan after neonicotinoid 

insecticides are used. It also has an excellent fit late in the season when a mixed population of plant 

bugs and stink bugs are in the field. 

For stink bug control, it is not uncommon in the Southeastern states to make four to six total insecticide 

applications due to stink bug migration into cotton from corn, soybeans, peanuts and other crops as 

they reach maturity. Common insecticides used to manage stink bugs are dicrotophos, acephate, 

pyrethroids and to a limited degree neonicotinoids. Of the three main species of stink bugs (green, 

Page 4 of6 
southern green and brown}, there is variability in their response to different insecticides. Dicrotophos 

performs very well on all species, but is particularly effective on brown stink bugs compared to other 

insecticides, such as pyrethroids and acephate. The loss of methyl parathion for use on cotton in 2012, 

reduced the options available. Because of the limited insecticide choices available, dicrotophos is a vital 

tool to manage resistance to pyrethroids. 

Application Parameters 

Although, used sparingly overall, dicrotophos is used strategically and is of immense importance to 

cotton growers. The number of total insecticide applications needed for plant and stink bug control is 

fluid and will depend on the circumstance of the year and the location of the crop. The current label for 

dicrotophos allows for use in cotton based on the cotton stage of growth. Early season use (emergence 

to pre bloom) allows for one application for either thrips or flea hoppers. Late season use (first bloom to 

30 days prior to harvest) allows for a total application of no more than 16 fluid oz/acre. 

Early season use is applied at lower rates to effectively control thrips or cotton flea hoppers. In some 

southern states, tobacco thrips have been reported to be resistant to neonicotinoid seed treatments; 

and with this threat to cotton producers, dicrotophos is a key tool for managing early season thrips. In 

terms ofthe economics ofthis early season control, dicrotophos cost is around $4.50/acre compared to 

acetamiprid at $12.00/acre. Use of dicrotophos does not trigger outbreaks of secondary pests, whereas 

acephate, which is also utilized to manage some insect pests, can trigger spider mites and cotton aphids 

particularly. 

For late season use, dicrotophos is essential. It is the only pesticide that can control plant bugs and stink 

bugs in a manner that prevents significant damage to cotton crops, because applications of dicrotophos 

can be made during the critical blooming and boll set period when cotton bolls must be protected. 

Inability to make sufficient applications will reduce effectiveness of the grower's pest management 

program, resulting in reduced yield and cotton fiber quality. Because dicrotophos is more efficacious 

than other chemistries against specific pests at specific times, it is a key component for successful 

implementation of IRM and IPM strategies. 

Aerial Application and Buffers 

Maintaining aerial application is critical for the effective use of dicrotophos to manage both early season 

and late season pests. It is not uncommon for wet field conditions to prevent ground application for 

thrips control, particularly in the Mid-South and Southeastern states. Thrips can cause significant 

damage to young cotton plants in a very short time, therefore growers rely heavily on aerial applications 

when weather prevents ground application. In late season plant bug and stink bug applications, aerial 

application is preferred to avoid crop damage from ground equipment. Wet weather can also be a 

factor in preventing timely applications in the mid to late season as well. 

Leaving an untreated area around a field is not a proven or acceptable IPM practice. Stink bug and other 

pest populations are most often heavier on the border when the pests are migrating into fields from 

other host crops nearby such as corn or peanuts. Buffers would serve as a nursery to create a rapid 

Page 5 ofG 
source for pest reinfestation into the remainder ofthe field as well as neighboring fields. In addition to 

the excessive damage to cotton plants in the border areas, the remainder of the field would incur more 

severe pest pressure and elevated yield losses. Such an approach could escalate the need for more 

frequent insecticide sprays to manage plant bugs and stink bugs. 

Retreatment Interval 

The current restriction on dicrotophos for late season application is a fourteen day retreatment interval 

which allows growers some flexibility while still limiting environmental impact. Any further restriction 

added to this would have serious consequences as it would cause an increase in the use of other 

products that may be more environmentally harmful, especially for pollinators. Brown stink bugs are 

known to be highly mobile and can re-infest a field in as little as two weeks. 

Industry Comments 

The National Cotton Council of America [sent via email on October 23, 2014 to Khue KguyenL the 

Arizona Pest Management Center [sent via email on November 10, 2014 to Khue Kguyen] and the North 

Carolina Department of Agriculture and Consumer Services [submitted to the public docket EPA-HQOPP-2008-0440-0028] all submitted extensive comments describing the critical need for dicrotophos 

with respect to their particular issues, pest pressures, buffers, and reentry intervals. AMVAC has 

carefully reviewed these letters and fully supports the comments. 

Page 6 ofG 
Appendix 2 
STUDY TITLE 

Response to EPA's Preliminary Drinking Water Exposure and Acute and Steady State 

Aggregate Dietary Risk Assessments for Dicrotophos 

TEST GUIDELINE: 

None 

AUTHOR: 

Dick Freedlander, Ph.D. 1 

REPORT COMPLETION DATE: 

November 24,2014 

TECHNICAL SUPPORT: 

Timothy L. Negley 

Christopher Hassinger 

ARCADIS U.S. Inc. 

6723 Towpath Road 

Syracuse, NY 13214 

PROJECT NUMBER: 

AMVAC Report #800-REV-020 

SUBMITTED BY: 

1

AMVAC Chemical Corporation 

4695 MacArthur Court, Suite 1200 

Newport Beach, CA 92660 

TOTAL PAGES: 

34 

NO CLAIM OF CONFIDENTIALITY 

Page 1 of34 
No claim of confidentiality, on any basis whatsoever, is made for any information contained in 

this document. I acknowledge that information not designated as within the scope of FIFRA sec. 

1 0( d)(l )(A), (B), or (C) and which pertains to a registered or previously registered pesticide is 

not entitled to confidential treatment and may be released to the public, subject to the provisions 

regarding disclosure to multinational entities under FIFRA lO(g). 

Company: AMV AC Chemical Corporation 

Company Agent: Dick Freedlander, Ph.D. 

Director of Environmental Sciences 

AMV AC Chemical Corporation 

Signature: ----'~'--------='-------~__:,,._ ___ ==--------

-==:::::::::: 

Date: __ .:__fl_.!.(_z._L/..:........jf"--Z=--D_I L}....l......--____ _ 

Page 2 of34 
GOOD LABORATORY PRACTICE COMPLIANCE 

This study does not fall under EPA FIFRA Good Laboratory Practice (GLP) Standards set forth 

in Title 40, Part 160 ofthe Code of Federal Regulations. 

Submitter: 

Signature: Date: 

Dick Freedlander, Ph.D. 

Director of Environmental Sciences 

AMV AC Chemical Corporation 

Page 3 of34 
TABLE OF CONTENTS 

1.0 SUMMARY ...................................................................................................................................... 6 

2.0 INTRODUCTION ............................................................................................................................ 8 

3.0 GENERAL COMMENTS ................................................................................................................ 8 

3.1 Use Patterns .................................................................................................................................. 8 

3.2 Aggregate Exposure Considerations ............................................................................................. 8 

3.3 EPA's Assessment of Drinking Water Exposure Based on Modeling .......................................... 9 

3.3 .1 Groundwater Modeling ......................................................................................................... 9 

3.3 .2 Surface Water Modeling ....................................................................................................... 9 

3.4 Water Modeling Refinements ..................................................................................................... 10 

3.4.1 Percent Crop Treated .......................................................................................................... 10 

3.4.2 Soil Adsorption ................................................................................................................... 11 

3.4.3 Aerobic Aquatic Metabolism .............................................................................................. 13 

3.4.4 Buffer Zones ....................................................................................................................... 15 

3.5 Surface Water Monitoring Data .................................................................................................. 15 

3.5.1 Dicrotophos Use from 1992 to 2009 ................................................................................... 16 

3.5.2 NA WQA Sampling Sites for Dicrotophos .......................................................................... 17 

3.5.3 NA WQA Sampling Sites with Dicrotophos Detections ..................................................... 18 

3.5.4 Location of Highest Measured Dicrotophos Concentration in NA WQA Data Set ............. 20 

3.5. 5 Discharge Rates vs. Residue Detections at Site of Highest Dicrotophos Concentration .... 21 

3.5.6 Relative Contributions of Drift and Runoff for Dicrotophos Surface Water Concentrations 

22 

3.5. 7 Refinement of Surface Water Exposure and Resulting Aggregate Exposure Risk ............. 23 

4.0 SPECIFIC COMMENTS ................................................................................................................ 27 

4.1.1 EPA memorandum of July 10,2014: (PC Code: 035201; DP Barcode 393772); 

"Dicrotophos: Drinking Water Assessment for Reregistration Review", by Andrew Shelby (Physical 

Scientist) Environmental Risk Branch 6 ............................................................................................. 27 

4.1.2 EPA memorandum of July 10,2014: (PC Code: 035201; DP BarcodeD418103); 

"Dicrotophos: Acute and Steady State Aggregate Dietary (Food and Drinking water) Exposure and 

Risk Assessments to Support Registration Review", by Thurston Morton (Chemist) Risk Assessment 

Branch IV, Health Effects Division (7509P) ...................................................................................... 31 

5.0 REFERENCES USED IN THE ASSESSMENTS ......................................................................... 34 

Page 4 of34 
List of Tables and Figures 

Table 3-1 Calculation of Surface Water Parent Compound EDWCs 

Table 3-2 Calculation of Surface Water Total Toxic Residues EDWCs 

Table 3-3 Sensitivity of Parent Compound EDWCs to Soil Adsorption 

Table 3-4 Sensitivity of Total Toxic Residues EDWCs to Soil Adsorption 

Table 3-5 Sensitivity of Parent Compound EDWCs to Aquatic Metabolism 

Table 3-6 Sensitivity of Total Toxic Residues EDWCs to Aquatic Metabolism 

Table 3-7 Sensitivity of Parent Compound EDWCs to Spray Drift 

Table 3-8 Sensitivity of Parent Compound EDWCs to Spray Drift 

Table 3-9 Dicrotophos Steady State Dietary Exposure forMS at Cotton Maximum Rate 

Table 3-10 Dicrotophos Steady State Dietary Exposure forMS at Cotton Typical Rate 

Table 3-11 Dicrotophos Steady State Dietary Exposure for NC at Cotton Maximum Rate 

Table 3-12 Dicrotophos Steady State Dietary Exposure forMS at Cotton Typical Rate 

Table 3-13 Dicrotophos Steady State Dietary Exposure for TX at Cotton Maximum Rate 

Table 3-14 Dicrotophos Steady State Dietary Exposure for TX at Cotton Typical Rate 

Figure 3-1 Map ofDicrotophos Use from 1992 to 2009 

Figure 3-2 NA WQA Map of Sampling Locations for Dicrotophos Analysis of Surface Water 

Sites 

Figure 3-3 NAWQA Map of Sampling Locations for Detections ofDicrotophos at Surface 

Water Sites 

Figure 3-4 Distribution ofNAWQA Surface Water Concentrations for Dicrotophos 

Figure 3-5 Map Location of Highest Measured Concentration ofDicrotophos within NAWQA 

Surface Water Sampling Sites 

Figure 3-6 Discharge Rate vs. Dicrotophos Residue Concentration at the NA WQA Site of 

Highest Residue Concentration 

Page 5 of34 
1.0 SUMMARY 

The only registered us for dicrotophos is on cotton, which when processed to a food commodity 

contributes very little to the overall dietary burden. Therefore, drinking water is the dominant 

factor in the dicrotophos aggregate risk assessment. 

The EPA has recently determined that the use of groundwater as a drinking water source would 

not yield any exceedances in the aggregate risk assessment. For that reason, this response is 

primarily focused on surface water exposure. 

The EPA has assessed dicrotophos surface water exposure in relation to the compound's acute 

population adjusted dose (aPAD). The Agency has demonstrated that the aPAD is not exceeded 

at the 95th percentile for any of the modeled cotton scenarios. This percentile would be 

appropriate for use within the aggregate risk assessment. Even when considering exposure 

within a sensitivity based analysis, at higher percentiles only one of the sub-population groups 

(all infants, <1 year old) yielded an exposure that was greater than 100% of the aP AD and this 

exposure was associated with the maximum, not the typical application rate. On this basis and in 

recognition of the conservative nature ofthe Agency's baseline analysis, the acute aggregate risk 

for dicrotophos should be deemed acceptable. 

EPA has also conducted a baseline modeling assessment using Calendex for developing a 

conservative estimate of sub-chronic risk. This assessment utilized PRZMIEXAMS modeling 

for determination of the average weekly surface water exposure. The Agency then based its 21-

day exposure using a 3-week rolling average over a year. From this analysis, EPA identified 

exceedances for some population groups at the 95th percentile. The highest exceedance is 

associated with infants (all infants, <1 year old) and the maximum use rate associated with the 

Mississippi use scenario. That exceedance EPA assumes is approximately twice (i.e., 2.1X) the 

acceptable cP AD level. 

Some refinements have been identified in this report that could be pursued within the modeling, 

(e.g., conducting additional soil metabolism studies to eliminate the use of correction factors). 

Further, this document focuses on two effective means for aggregate risk refinement that can be 

immediately implemented. The first being the refinement of the modeling based on the 

provisions of the current dicrotophos label (e.g., established buffer zone requirements) and the 

second being the utilization of higher tier surface water exposure data by further consideration of 

available surface water monitoring data. 

On the first point, information contained within this report indicates that modeled surface water 

contamination would primarily occur through runoff events, although a component of the residue 

would be associated with drift potential. It is recognized that currently there is not an accepted 

modeling approach for translating buffer zones to surface water exposure levels. Nor is there a 

validated approach for refining drift contributions based on drift reduction technology practices 

already in place. Still, it is quite evident that these factors do translate to a significant lowering 

of surface water exposure from chemical application. 

Page 6 of34 
Concerning the second point, the USGS National Water-Quality Assessment Program 

(NAWQA) and the USDA's Pesticide Data Program provide approximately 8,500 samplings of 

agriculturally relevant surface water bodies. This data provides a realistic and more accurate 

assessment of surface water exposure potential to dicrotophos use. Although the Calendex-based 

risk assessment utilizes a weekly average concentration, it would be more appropriate to adopt a 

3-week average concentration in order to match the response time associated with the 

toxicological endpoint. In either case, it is important to recognize that uncertainties associated 

with the determination of the peak water concentrations within the monitoring data become 

much less influential when considering a sub-chronic based exposure. Further, the use of a very 

extensive monitoring database provides an opportunity to examine exposure trends and better 

understand temporal exposure trends. Therefore, by taking advantage of this monitoring 

database, it is possible to more accurately assess surface water exposure in a meaningful and 

more realistic manner. 

Within USDA's Pesticide Data Program, there were a limited number of samplings for 

dicrotophos with only 4 detections from 232 finished water samples and 3 detections from 253 

untreated water samples. These limited detections would suggest there are few incidents of 

dicrotophos getting into water samples. The highest reported concentration was 0.003 ppb, 

which is more than 2 orders of magnitude below EPA's PRZMIEXAMS modeled concentration. 

Within NA WQA, it is immediately evident that dicrotophos exposure is low. EPA has reported 

that within the entire collection of sampling sites, there are only 57 detections (<1% of the 

sampling) with measureable residues. With one exception, all residues are at concentration 

levels that are less than 0.3 ppb, a level that is 2.7X lower than what was predicted for subchronic exposure in baseline modeling conducted by the Agency using PRZMIEXAMS. 

The implications ofthis single >0.3 ppb concentration (i.e., 6.83 ppb) sampling in Washington 

County, Mississippi, was further examined to better understand the implications of this result. It 

was noted that sampling taken on the next day had measured residues that were more than an 

order of magnitude lower. As the Agency has determined that the steady state exposure is 

associated with a 21 day period, it is clear that the average surface water concentration at this site 

would be much lower than the peak concentration. Further, the absence of a relationship 

between discharge rate and residue concentrations at this site, challenges the integrity of this 

aberrant data point. 

Within this report, a very conservative approach was used for refining the 21 day exposure of 

dicrotophos in surface water using the extensive monitoring database. A concentration of 0.3 

ppb from the modeling data, which represents an upper limit or near upper limit (i.e., >99.9 

percentile) in monitoring data expoaure was used to refine the aggregate risk assessment. Under 

these circumstances, there are no exceedances at the 95th percentile in the aggregate risk 

assessment at the maximum use rate. Therefore, this still conservative assessment demonstrates 

that the use of dicrotophos on cotton does not exceed the health-based safety standards of the 

EPA. Further, this assesment does not consider label mitigation factors already in place on the 

current labels that would have a significant bearing on lowering exposure levels even further. 

Page 7 of34 
2.0 INTRODUCTION 

The Environmental Protection Agency (EPA) released their Preliminary Environmental Fate and 

Ecological Risk Assessment (ERA) for the Registration ofDicrotophos in July, 2014. This report 

outlines the preliminary aggregate risk assessment conducted by EPA under the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA) for registration review of dicrotophos. 

Dicrotophos is a systemic broad spectrum organophosphate insecticide with a mode of action 

that interferes with the acetylcholinesterase enzyme (AChE). AMV AC Chemical Corporation 

(AMVAC) currently manufactures two end-use products that contain dicrotophos; Bidrin® 8 

(82% dicrotophos) and Bidrin XP IITM (50.7% dicrotophos + 11.2% bifenthrin). Bidrin 8 and 

Bidrin XP II are only proposed for use on cotton through both aerial and ground application. 

As part of the registration review process, AMV AC has retained ARCADIS to review EPA's 

surface water exposure assessment. The following report has two main sections. Section 3.0 

provides general comments on the approaches used by the Agency in developing their exposure, 

effects, and risk characterization. Section 4.0 contains specific comments on the Agency's report 

that includes typographic errors, data or calculation errors, and other specific comments. 

3.0 GENERAL COMMENTS 

The following general comments address key issues that have been identified within EPA's 

preliminary drinking water exposure and acute and steady state aggregate dietary risk 

assessments for dicrotophos. 

3.1 Use Patterns 

There have been significant changes to the use patterns for dicrotophos since it was first 

registered in the United States. These changes and important mitigation measures adopted on its 

labels have resulted in significant decreases in human population and environmental exposure. 

3.2 Aggregate Exposure Considerations 

There have been significant changes to the use patterns for dicrotophos since it was first 

registered in the United States. The only remaining food use is associated with cotton and the 

only potential exposure through ingestion of dicrotophos residues in cottonseed oil. As there are 

no residential uses, exposure is driven by ingestion of drinking water. Therefore, aggregate 

exposure to dicrotophos is approximately equal to the exposure associated with drinking water. 

Page 8 of34 
3.3 EPA's Assessment of Drinking Water Exposure Based on Modeling 

3.3.1 Groundwater Modeling 

EPA's assessment of groundwater exposure utilizes both maximum and typical use rates 

associated with dicrotophos use on cotton. The Agency has used a total toxic residues (TTR) 

approach in its assessment. However, AMV AC is proposing that this grouping be redefined to 

only consider residues that would be expected to have cholinesterase inhibiting potential. 

Additional information is provided under the "Specific Comments" section of this report. 

The Agency also noted that it has adopted its conservative approach of applying a 6X factor to 

the aerobic aquatic metabolism input parameter due to data deficiencies, rather than due to any 

determination of current data. Although from a policy perspective this is appropriate, it is also 

recognized that this parameter likely exaggerates the degradation rate of dicrotophos under 

aerobic aquatic conditions. 

The PRZM/GW modeling employed by EPA yielded a groundwater concentration of 0.06 ppb, 

which was employed for both acute and chronic risk considerations. This concentration is more 

than 2 orders of magnitude lower than the acute concentration calculated by EPA for surface 

water acute exposure. The concentration in groundwater for chronic exposure is more than 1 

order of magnitude lower than the concentration calculated by EPA for surface water chronic 

exposure. 

The groundwater aP AD is not exceeded at the 95th percentile for any of EPA's modeled cotton 

scenarios. At higher percentiles only one of the sub-population groups (all infants, <1 year old) 

yielded an exposure that was greater than 100% of the aP AD and this exposure was associated 

with the maximum application rate. The groundwater cPAD is not exceeded for any EPA's 

modeled cotton scenarios, even at higher percentiles. On this basis, it can be concluded that 

drinking water associated with groundwater would not pose an aggregate risk concern. 

3.3.2 Surface Water Modeling 

EPA's assessment of surface water exposure also utilizes both maximum and typical use rates 

associated with dicrotophos use on cotton. Again, the Agency has used a total toxic residues 

(TTR) approach in its assessment. The Agency also adopted its conservative approach of 

applying a 6X factor to the aerobic aquatic metabolism input parameter. 

The PRZMIEXAMS modeling employed by EPA yielded a concentration of 12.44 ppb for acute 

risk considerations and 0.8 ppb for chronic risk considerations. 

Based on preliminary baseline modeling, dicrotophos exposure through surface-based drinking 

water would exceed sub-chronic regulatory limits placed on aggregate risk. 

Page 9 of34 
3.4 Water Modeling Refinements 

3.4.1 Percent Crop Treated 

EPA provided surface water EDWCs modeled in PES that accounted for the percent crop treated 

in all cases except for the California scenario. The product is not currently labeled for use in this 

state. For this reason, AMY AC proposes that EPA remove this scenario from its assessment. 

However, as the Agency is currently evaluating a CAuse, we believe that the same factors 

should be applied to all scenarios. 

ARC AD IS has performed calculations in a comparable manner to EPA for all of the scenarios; 

but has also applied the percent crop treated factor to the California scenario. 

Table 3-1 Calculation of Surface Water Parent Compound EDWCs 

0.1 10.84 0.57 0.32 

0.1 10.84 0.58 0.32 

0.1 9.33 0.62 0.32 

Parent 0.1 9.33 0.62 0.32 Compound 

Residues 

0.1 12.01 0.56 0.30 

0.1 12.01 0.56 0.30 

CA Cotton Maximum 0.1 6.90 0.55 0.51 (USEPA)< 

. CA Cotton Maximum 0.1 (ARCADIS) 

1/ Modeling performed in PES utilizing a percent crop treatment factor of 33% 

2/ Shaded values indicate~ 10% change in EDWCs between EPA and ARCADIS 

Page 10 of34 
Table 3-2 Calculation of Surface Water Total Toxic Residues EDWCs 

... Surface Water EDWCs .· · .... _ .... 

Crop Scenario Pro b. 1 Peak I 30-Yr ... · Yearly . Avg . . . 

•••••• 

MS Cotton Maximum .. 0.1 11.03 0.72 0.41 (USEPA) 

••••• ···.· . ·•. 

•••••• MS Cotton Maximum 

••••• 

(ARCADIS) 0.1 11.03 0.72 0.41 

·. 

NC Cotton Maximum 0.1 9.60 0.80 0.41 (USEPA) .. 

Total Nt Cotton Maximum 0.1 9.60 0.80 0.41 Toxic (}\RCADIS) 

Residues 

TXGotton Maximum 0.1 12.44 0.70 0.38 {USEPA) 

TXCotton Maximum 0.1 12.44 0.70 0.38 (ARCADIS) ·_:. 

CACotton Maximum 0.1 7.51 0.70 0.65 (lJSEPA) .. 

.· 

. . . 

.·i!t~j: -- . ·- . 

~·-K~-~i~~;:,\,:. GA Cotton Maximum· ·•·· 0.1 0.23.··- (ARCADIS) .·.··· \;'."?:""""" 

1/ Modeling performed in PES utilizing a percent crop treatment factor of 33% 

2/ Shaded values indicate~ 10% change in EDWCs between EPA and ARCADIS 

3.4.2 Soil Adsorption 

The potential effect on surface water exposure by refining the soil adsorption parameter was 

considered. There are two avenues for such refinement. First, as there does not appear to be a 

correlation between percent organic matter and compound adsorption, individually assessing the 

prevalent soils used for cotton in the use regions would provide for a more refined exposure 

assessment. Because the range of soil properties is diverse, there are unanswered questions 

concerning implementing an effort in this area. Because there are better means for reining 

exposure, there are no plans for initiating studies in this area. 

Second, there is the possibility of refining exposure on the basis of determining the fraction of 

bioavailable residue in the water phase and correcting the Kd value on that basis. There are 

techniques that have been developed for this type of determination such as solid phase microextraction (SPME). Because dicrotophos has some soil binding potential, there is an expectation 

that exposure to bioavailable residue would be lower than would be indicated by the current Kd 

value. 

Page 11 of34 
A sensitivity analysis indicates that a 3X increase in the Kd would lower acute exposure by more 

than 10% in the three major cotton modeling scenarios for TX, MS, and NC. Changes of this 

magnitude would normally be considered small but because the risk exceedances within the 

steady state risk assessment are not so significant, these differences could be meaningful. At this 

time, AMVAC believes that surface water exposure refinement can be better addressed by other 

means described in this report; thus this work is not being initiated at this time. 

The sensitivity analyses as performed by ARCADIS for parent compound and total toxic 

residues (TTR) residues is provided below. 

Table 3-3 Sensitivity of Parent Compound EDWCs to Soil Adsorption 

:, Sensitivity ofParent Compound EDWCs to Increasing ...... 

SoiJ Adsorptioll Coefficient (Kd)11 

swcc Sensitivity 1-in-10 Year Values (ppb)31 % Reduction31 

·Crop Analysis21 

Peak Yearly 

30-Yr 

Peak Yearly 30-Yr 

Scenario Scenario i·. Avg~ Avg. 

Baseline 10.80 0.65 0.35 

MS .,. Kdx3 8.65 0.62 0.19 .:.20.1 -4.1 -9.1 

Cotton 

Kdx10 5.71 0.51 0.26 . ,41-2 -21.8 -25.6 

Baseline 10.00 0.84 0.39 

: 

NC Kdx3 8.22 0.67 0.34 a:" C:.19;9 -12.9 .·· Cotton 

KdxlO 5.61 0.49 0.27 -42.:3 -30.4 

Baseline 13.10 0.96 0.38 

TX Kdx3 11.40 0.73 0.35 ;,fJ • -3.6 -8.0 

Cotton . ::·,; KdxlO 7.82 0.53 0.28 ·q~ ~:~~0~1,\·•· f;jr~~,ij.s c.' 

1/ Modeling performed with Surface Water Concentration Calculator (SWCC) utilizing 

a percent crop treatment factor of 33% 

2/ Baseline Kd = 1.24 ml/g (3X = 3.72 ml/g; lOX= 12.4 ml/g) 

3/ Shaded values indicate<: 10% reduction in EDWCs relative to baseline scenario 

Page 12 of34 
Table 3-4 Sensitivity of Total Toxic Residues EDWCs to Soil Adsorption 

Sensitivity ofTotal Toxic Residue (TTR) EDWCsto Increasing 

· •. ·· • Soil Adsorption Coefficient (Kd)11 •···· 

SWCC •·. Sensitivity 1-in-10 Year Values (ppb)31 ·····% Reduction31 ···• 

Crop.··.·. Analysis21 r-----.-~--"-'---,...•.---+-~~""""T"-.. · .-.~.~ .. ->....-'--. --.--1 

Scenario Scenario 

··•·· Baseline 

TX 

Cotton 

KdX: 10 

Baseline 

Kdx 3 ·•· 

KdxlO 

Baseline 

Kdx3 . . . ··• . 

Kdx.lO··· 

Peak Yearly 30-Yr Peak • Yeai:ly .· · • 30~vr .. Avg. · ... · · ... · .. Avg. 

6.01 0.69 

11.00 1.09 

9.11 0.90 

6.24 0.71 

13.66 0.97 0.49 

12.10 0.96 0.46 . -11.1. -1.3 -6.4 

8.38 0.74 0.38 ; -38.6 

1/ Modeling performed with Surface Water Concentration Calculator (SWCC) 

utilizing a percent crop treatment factor of 33% 

2/ Baseline Kd = 1.24 ml/g {3X = 3.72 ml/g; lOX= 12.4 ml/g) 

3/ Shaded values indicate;::: 10% reduction in EDWCs relative to baseline scenario 

3.4.3 Aerobic Aquatic Metabolism 

As a half-life has not been defined for dicrotophos degradation by aerobic aquatic metabolism, 

the EPA has used the values for the aerobic soil metabolism and applied a correction factor of 

2X. Additionally, because there was limited aerobic soil metabolism data, a correction factor of 

3X was applied for that value. In total, a 6X correction factor was applied. Therefore, EPA 

utilized highly conservative half-life values of 16.2 and 17.4 days for parent and total toxic 

residues as modeling input values for the aerobic aquatic metabolism of dicrotophos. 

As shown in the table below, the elimination of the 6X correction factor for the aerobic aquatic 

metabolism value has a modest effect on acute EDWCs, but a fairly significant effect on the 

chronic EDWCs. Although the reported concentrations do not include 21-day average values, the 

annual values attest to the sensitivity of the parameter. At this time, AMV AC believes that 

surface water exposure refinement can be better addressed by other means described in this 

report; thus this work is not being initiated at this time. 

The sensitivity analyses as performed by ARCADIS for parent compound and total toxic 

residues (TTR) residues is provided below. 

Page 13 of34 
Table 3-5 Sensitivity of Parent Compound EDWCs to Aquatic Metabolism 

Sensitivity of Parent Compound EDWCs to Eliminationof6X Correction Factor 

for Estima1:ingAerobic Aquatic Metabolism Half-life11 · •... 

SWCC Sensitivity 1-in~lOYear Values (ppb)31 ••.•.•.• · ..• ·.• % Reduction31 · ... · 

... · •.. Crop Analysis21 . . .·. 30-Yr .··•.·.. k 30-Yr 

Scenario Scenario Peak Yearly Pea Yearly · · .· .. Avg. ..· .... ·· .... · Avg. 

MS Baseline 10.80 0.65 0.35 

Cotton Baseline/2 8.02 0.26 

NC Baseline 10.00 0.84 0.39 

.. ·Cotton Baseline/2 7.06 0.27 

TX Baseline 13.10 0.76 0.38 

Cotton Baseline/2 8.42 0.26 

1/ Modeling performed with Surface Water Concentration Calculator (SWCC) utilizing 

a percent crop treatment factor of 33% 

2/ Baseline t 112 = 16.2 d (X/2 * X/3 = 2.7 d) 

3/ Shaded values indicate:?: 10% reduction in EDWCs relative to baseline scenario 

Table 3-6 Sensitivity of Total Toxic Residues EDWCs to Aquatic Metabolism 

Sensitivity of Total Toxic Residue (TTR) EDWCs to Elimination of GX Correction 

Factorfor Estimating Aerobic Aquatic Metab()lism Half-life11 

SWCC Sensitivity 1-in:..1o Year Values (ppb)31 

Crop 30-Yr Yearly Analysis21 30-Yr 

Yearly Scenario Scenario ·Peak 

Avg. 

MS Baseline 11.00 0.81 0.43 

Cotton 2.7 d t:l/2 9.14 0.20 0.10 

NC Baseline 11.00 1.09 0.50 

Cotton 2.7 d tl/2 8.25 0.22 0.10 

TX Baseline 13.70 0.97 0.49 

Cotton 2.7 d t:l/2 10.80 0.19 0.10 

1/ Modeling performed with Surface Water Concentration Calculator (SWCC) utilizing 

a percent crop treatment factor of 33% 

2/ Baseline t 112 = 17.4 d (X/2 * X/3 = 2.9 d) 

3/ Shaded values indicate:?: 10% reduction in EDWCs relative to baseline scenario 

Page 14 of34 
3.4.4 Buffer Zones 

The current labels for dicrotophos prohibits product use within 25 feet by ground and 150 feet by 

air to lakes, reservoirs, rivers, permanent streams, marshes, natural ponds, estuaries, and 

commercial fish ponds. Such restrictions would have a significant effect on chemical loading 

into surface water bodies by both runoff and drift. Although there is not an EPA prescribed 

procedure on assessing the effectiveness of buffer zones, there are models available for 

estimating the effectiveness of different size buffer zones. 

Recent approaches by different researchers have incorporated the Vegetative Filter Strip model 

(VFSmod) into EPA's PRZMIEXAMS model. Runoff and erosion predicated by PRZM is 

reduced via the VFSmod prior loading into EXAMS. Calculations can be performed repeatedly 

on a storm event basis. For relatively rapidly degrading pesticides such as dicrotophos, this 

approach has been shown to primarily reduce the longer-term EECs, which for dicrotophos 

yields the exceedances. The acute exposure is less impacted because large rainfall-based runoffevents are not efficiently managed by vegetative filter strips. 

3.5 Surface Water Monitoring Data 

In a drinking water exposure assessment process, conducting baseline modeling using 

conservative parameters is an appropriate initial step. For dicrotophos, this directs further efforts 

towards refining the assessment of surface water exposure. As in most environmental 

assessments, developing actual field data provides a strong basis for refining exposure 

assessments based on modeling and in some cases can improve the reliability of the models. 

In the case of dicrotophos, the USGS National Water-Quality Assessment Program (NAWQA) 

and the USDA's Pesticide Data Program provide approximately 8,500 samplings of 

agriculturally relevant surface water bodies that have been analyzed for dicrotophos. This 

information provides an indication of acute exposure, but more critical to the regulatory needs 

for dicrotophos, it provides reliable data that can accurately assess chronic-based exposures in a 

real world setting. 

The overlap between the areas associated with dicrotophos use (primarily cotton) and the 

monitoring data demonstrates that some of the data appropriately targets surface water bodies 

where the product was used while some of the data is in regions where product use is nonexistent or low. However, even when the data set is paired down to only reflect product use 

areas, there remains a substantial monitoring dataset. 

Page 15 of34 
3.5.1 Dicrotophos Use from 1992 to 2009 

Figure 3-1 Map ofDicrotophos Use from 1992 to 2009 

LEGE I'D 

[=:J stale Bo ... dary Dicrotophos 

O>unty Boundary To1a I Kilograms 

0_1 -3 

'4-131 

132-1035 

~~- 1036- 4890 

- 4891 -159254 

N:llES: 

1_ Data represent USGS E-PEST tJ[gh) eslirm1es at 

a the cotnf:y leveL 

Page 16 of34 

Kilometers 

o 250 roo 

NEWPORT 

NJ.VAC CHEMICAL 

BEACH, CALIFORNIA 

CORP_ 

--

DRINKING WATER ASSESSMENT 

DICROTOPHOS ESllMATED 

USE (1992-2009) 

ARCADIS AGURE 

1 
3.5.2 NA WQA Sampling Sites for Dicrotophos 

Figure 3-2 NA WQA Map of Dicrotophos Surface Water Sampling Locations 

LEGEND 

Dicrotophos Dicrotophos 

Observed Tota I Kilograms 

Slate Boundary 0_1 -3 

O:mnty Boundary 4 - 131 

132-1035 

1036-4890 

-4891-159254 

NOlES: 

1_ Data represent USGS E-PEST (High) e9.irmf.es at 

3the county lellel from 1992 to 2009_ 

2. NAWQA surface water data avai~lefrom 

;D05to 2010. 

Kflometers 

0 250 500 

._ • I 

AMVAC CHEMICAL CORP. 

NEWPORT BEACH, CALIFORNIA 

DRINKtiG WATER ASSESSMENT 

DICROTOPHOS OBSERVATIONS 

VERSUS ESllMATED USE 

FIGURE @ARCADIS X 

The reported detections of dicrotophos correlate reasonably well with areas of high product use 

such as north-east Texas, MS, and GA. 

Page 17 of34 
3.5.3 NA WQA Sampling Sites with Dicrotophos Detections 

Figure 3-3 NA WQA Map of Sampling Locations for Detections of Dicrotophos at Surface 

Water Sites 

lEGEND 

Dicrotaphos Dicrotophos 

) Observed To1a I Kilogr.tms 

state Boundary 0_1 - 3 

Omnty Boundary 4 - 131 

132-1035 

1036-4890 

4891 - 159254 

NOlES: 

1_ Data represent USGS E-PEST ~igh) eslirTDtes at 

cj the county level from 1992 to 2009. 

2. NAWQA surface water data avaiiWie from 

2D051o 2010_ 

Kiometers 

0 250 500 

le • I 

AMVAC CHEMICAL CORP_ 

NEWPORT BEACH, CALIFORNIA 

DRINKING WATER ASSESSMENT 

DICROTOPHOS OBSERVATIONS 

VERSUS ESllMATED USE 

FIGURE 

~ARCADlS X 

As there are some detections outside of the expected boundaries for product use, which indicates 

that there may be some false positives in the survey, which suggests that actual exposure may be 

lower than that indicated by the dataset. 

It is recognized that there is some uncertainty in determining peak water concentrations from 

monitoring data due to limitations in sampling frequency. However, when the objective is set at 

determining an average water concentration over a longer period, monitoring data becomes much 

more rigorous. In the case of dicrotophos, the exposure period associated with the 

toxicologically significant cholinesterase point of departure is reached at 21 days. Monitoring 

data would be expected to provide a reasonable assessment of average concentration values 

within such an extended period. 

Page 18 of34 
A preliminary assessment of the monitoring data indicates that exposure to dicrotophos in 

surface water is very low. Within the entire collection of sampling sites, there are only 57 

detections ( <1% of the sampling) with measureable residues. With one exception, all residues 

are at concentration levels that are less than 0.3 ppb, a level that is 2.7X lower than what was 

predicted for sub-chronic risk in baseline modeling using PRZM/EXAMS. 

Figure 3-4 Distribution of NA WQA Surface Water Concentrations for Dicrotophos 

_r::_._ 

Monitoring from: 112005 to 12/2010 

8,831 results 

. . 99.45% <LOD 

0.65% detected 

1 result >0 .3 ppb 

Futher corroboration that the average 21-day exposure would be at low levels is provided by 

examining the finding at the one site in Washington County., Mississippi, where residues 

exceeded 0.3 ppb. This occurred in a single sampling event. Sampling was also taken on the 

subsequent day and the residue concentration in this sample was more than an order of 

magnitude lower. These findings may be evidence that at higher dicrotophos concentrations are 

very short-lived in the environemnt; therefore they would not have a very significant impact on 

the average 21-day residue concentration. 

Page 19 of34 
3.5.4 Location of Highest Measured Dicrotophos Concentration in NAWQA Data Set 

Figure 3-5 Map Location of Highest Measured Concentration of Dicrotophos within 

NA WQA Surface Water Sampling Sites 

. . -r ,,.,~ ~,~ ,';,Jkoi,.,_;._-., 

'/."·~-m~~ 

.··!1:1 •. ~} 

t .J'tt f..,A ~ -:;)t'.>ltl 

J«H-:-... ;:~·~-trp1 H.l'"tl 

hAdifi~;..:l';Jj_j-, J. 

{ 'i'fh'l !~ .:~-~ 

NAWQA 

Diaotophos Result 

:!iJ; non-detect 

!if detect 

Cropland Data Laye~ 

L.Jeotton 

other wale !Way 

stream 

D 1lkliglHU 

NOl"ES: 

1. CllUon giO'IWBg areas based on USilA. 

Cropland Dala layer-{all} in 2005 

with erimated use..-accuHic:y >95%. 

Page 20 of34 

_, .... · Vrl->.Jd:>ti'·l~H<·· 

''-., YN+N·}U~:<;:j' 

JW,VAC CHEMICAL CORP. 

NEWPORT BEACH, CALIFORNIA 

001\!Ka'lG WA l"ERASSESSIIBIT 

lOCA110N OF MAXIMUM 

DICROlOPHOS RESUlT 

~ARCADIS fiGURE 

X 
3.5.5 Discharge Rates vs. Residue Detections at Site of Highest Dicrotophos 

Concentration 

Figure 3-6 Discharge Rate vs. Dicrotophos Residue Concentration at the NA WQA Site of 

Highest Residue Concentration 

"0 

c: 

c 

u 

Q) 

(4 1008 

'-Q) 

a. 

~ 

Q) 

Q) 

.... 

u 

·.-I 

..c 

::l 

u 

Q) ' 

~ 

'-ttl 

..c: 

u 

~? 

;3 108 

)-

..J 

H 

USGS 07288650 BOGUE PHALIA NR LELAND, MS 

a: 

c 8 ~---=~mmmmwm~--.m .... mmmmmmmmBmmmemmmwm.mmmwmwm~ 

Jul 02 Jul 09 Jul 16 Jul 23 Jul 30 Aug 06 Aug 13 Aug 20 Aug 27 

280~ 200~ 288~ 280~ 208~ 280~ 280~ 200~ 200~ 

--- Daily nean discharge ~ Period of approved data 

http://waterdata.usgs.gov/nwis/dv?cb 00065=on&cb 00060=on&cb OOOlO=on&cb 00095=on 

&format=gif default&site no=07288650&referred module=sw&period=&begin date=2005-

07-0l&end date=2005-08-30 

Further, a more detailed analysis ofthis site by ARCADIS reveals that the peak detection was 

not associated with discharge rates at the sampling site. As demonstrated in the following 

section, dicrotophos surface water concentrations are primarily impacted by runoff. Normally, 

higher discharge rates would promote the movement of residues from fields to surface water 

bodies. The lack of a relationship between these parameters challenges the reliability of the 

analytical result showing the peak detection at this site. Also, the fact that there was only one 

detection of this magnitude and no intermediate detections within a one magnitude range below 

this detection within the entire survey challenges the relevance of this single finding. 

Page 21 of34 
3.5. 6 Relative Contributions of Drift and Runoff for Dicrotophos Surface Water 

Concentrations 

To assess the relative sensitivity of the EDWCs to spray drift and runoff, a sensitivity analysis 

was performed. For this effort, the baseline spray drift fraction of0.016 in the baseline 

assessment was reduced by 50% (0.08) in one scenario and no spray drift was assigned within 

the second scenario. There are only modest decreases in surface water concentrations by 

modifying the drift parameter and the contribution of spray drift to the yearly concentration is 

less than 20%. Although the modeled concentrations do not include 21-day average values, the 

annual values attest to the sensitivity of the parameter and demonstrate that runoff would likely 

be the dominating factor contributing to dicrotophos residues in surface water. 

Table 3-7 Sensitivity of Parent Compound EDWCs to Spray Drift 

Sensitivity of Parent Compound EDWCs to Decreasing Spray. Drift 

.to 50% and 0% of Baseline11 

1-irf-10 Yeai"Values (ppb)31 

Peak 30-Yr Yearly. Avg. 

10.80 0.65 0.35 

10.20 0.59 0.29 

9.54 0.53 

10.00 0.84 0.39 

9.41 0.78 0.33 -6.0 

8.78 0.71 0.26 .,12~~-

13.10 0.76 0.38 

Cotton 

12.40 0.69 0.31 -5.3 

10.80 0.62 0.25 

1/ Modeling performed with Surface Water Concentration Calculator (SWCC) 

utilizing a percent crop treatment factor of 33% 

2/ Per EPA standard baseline drift set to 0.016 for aerial spray application. 

30-Yr 

Avg. 

~18.20 

3/ Shaded values indicate;::: 10% reduction in EDWCs relative to baseline scenario 

Page 22 of34 
I 

Table 3-8 Sensitivity of Total Toxic Residues EDWCs to Spray Drift 

Sensitivity of Total Toxic Residue EDWCs,to Decreasing Spray Drift 

. to 50% and 0% of Baseline11 

swcc Sensitivity 1-in-10 Year Values (ppb)31 % Reduction31 

Crop. Analysis21 . 30-Yr 30-Yr Peak Yearly Peak Yearly Scenario Scenario Avg. Avg. -~ 

.\ MS 

Baseline 11.00 0.81 0.43 

SO% drift 10.30 0.74 0.36 -6.06 -9.15 •. ..c16.40 

Cotton . . . // 

0% Drift 9.64 0.66 0.29 d~.s:· 1:> '-3;:t3 <; ;-12.1 •·•·• 

Baseline 11.00 1.09 0.50 

NC •••••• 50% drift 10.20 1.01 0.42 6.9 -7.7 :-fs.s 

Cottoni 0% Drift 9.50 0.92 0.34 · .. ·7'13.s·•·· n:.·.~~~-s . 1< .:3iA .. Baseline 13.70 0.97 0.49 

TX 50% drift 12.80 0.88 0.40 -6.5 -9.2 '-;t;7.8 

•• Cotton 

•. 0%Drift 11.90 0.80 0.32 i:;..12Jf' ~l~.ti; lt·~~?A 

1/ Modeling performed with Surface Water Concentration Calculator (SWCC) 

utilizing a percent crop treatment factor of 33% 

2/ Per EPA standard baseline drift set to 0.016 for aerial spray application. 

3/ Shaded values indicate~ 10% reduction in EDWCs relative to baseline scenario 

3.5. 7 Refinement of Surface Water Exposure and Resulting Aggregate Exposure 

Risk 

Overall the monitoring data set reflects dicrotophos concentrations of 0.3 ppb or less. By taking 

the conservative step of adopting this value to represent the 21-day average concentration and 

conducting a refined aggregate risk assessment, there are no exceedances associated with the 95th 

percentile sub-chronic risk for any of the three EPA scenarios. It should be noted that these 

calculations represent approximate values as the assessment assumes that all of the exposure is 

due to surface water, when in fact there is a very small contribution by cottonseed oil. However, 

this effect is negligible and does not change the findings of the analysis. 

A comparison ofEPA's steady state dietary exposure analysis based on PRZMIEXAMS 

modeling with that based on conservative use of the NAWQA monitoring data set is provided 

below for maximum and typical use rates in MS, TX, and NC. 

Page 23 of34 
Table 3-9 Dicrotophos Steady State Dietary Exposure forMS at Cotton Maximum Rate 

Results of Steady State Dietary Exposure Analysis for Dicrotophos 

(Food and Drinking Water} MSCottoli Maximum Rate 

·······• .··. •. 

Population Subgroup 

General US Population 

Alllnfants(<1 year old) 

Children 1-2years old 

Children 3"5 years old 

Children 6-12 years old 

Youth 13-19 years old 

Adults 20-49 years old 

Adults 50~99 years old 

Females 13-49 years·old 

PRZM/EXAMS Chronic Water, Conservative NAWQA 

Monitoring Data Water Concentration 0.80 ppb PAD ••·. Concentration 0.30 ppb 95th Percentile 

( mkd) J-,-~.,.--'--~--__,...--..;.;_•-+~.;.;.....,.-9_5t_h,..P_e_r_ce..,..n~t-ile_..,....----l 

Exposure % PAD1; < Exposure %PAD1/ 

•··.··. (mkd) (mkd) •·.·· 

·.. 0.000277 92 0.000104 35 

0.000632 . 210 •( > 0.000237 79 

0.000367 ·, 12.2 > .. i 0.000138 46 

...... 0.000315 105 ;. {;';', 0.000118 39 

0.0003 0.000258 86 0.000097 32 

0.000237 79 0.000089 30 

0.000277 92 0.000104 35 

0.000228 76 0.000086 28 .·.··~-------r------------r-------+-----------~ 

.• 0.000281 93 0.000105 35 

1/ %PAD text that is in bold reflects exceedances 

Table 3-10 Dicrotophos Steady State Dietary Exposure forMS at Cotton Typical Rate 

R«;!sLJits of Steady State Dietary Exposure Analysis for Dicrotophos 

(Food and Drinking Water) · .•, •.. MS Cotton Typical Rate < · ....• Conservative NAWO.A PRZM/EXAMS Chronic Water 

Monitoring Data\fiJater Concentration 0.80 ppb · . 

Population Subgroup PAD 95th Percentile' Concentration 0.39 ppb 

(mkd) 95th Percentile 

Exposure ... Exposure 

••• •••• (mkd) 

% pA[)l/ ... (mkd) % PAD11 

.. 

General U.S. Population . · 0.000206 69 0.000077 26 

All Infants {<1 year old) 0.000399 ·. · .. . i~gi• ~~it ;j?;; 0.000150 49 

Children1-2 years old 0.000262 87 0.000098 33 

Children 3-5 years old 

00~~ 0.000149 76 0.000056 29 

Children 6-12 years old 0.000145 66 0.000054 25 

Youth 13,-19 years old 0.000144 65 0.000054 24 

Adults 20~49 years old 0.000116 69 0.000044 26 

Adults 50-99 years old 0.000228 53 0.000086 20 

Females B--49years old 0.000146 69 0.000055 26 

1/ %PAD text that is in bold reflects exceedances 

Page 24 of34 
Table 3-11 Dicrotophos Steady State Dietary Exposure for NC at Cotton Maximum Rate 

Results ofSteady State Dietary Exposure Analysi$ for Dicrotophos .. . 

,, (Foodand Drinking Water} , NC Cotton Maximum Rate 

,:· . . ... ·. 

Conservative NAWQA PRZM/EXAMSChronic Water Monitoring Data Water 

.,'PAD Concentration 0_80 ppb Concentration 0.30 ppb PopulationSubgroup 95th Percentile (rnkd) '· 95th Percentile 

Exposure < 

%PAD11 Exposure % PAD11 

' {mkd) .·. (mkd) 

General. U.S. Population 0.000265 88 0.000099 33 

Alllnfants(<l year old) 0.00059 :~~ ·<;2oo· .. :;;, 0.000221 75 

Children 1,.2 years old ····· ·, .. 0.000356 \'u i;.e: •[l20. .;> 0.000134 45 

Children 3-5 years old I 0.000302 100 0.000113 38 

Children 6-12 years old 0.0003 0.00025 83 0.000094 31 

Youth 13-19 years old 0.00023 77 0.000086 29 

Adults 20-49 years old 0.000263 88 0.000099 33 

Adults 50-99 years old 0.000215 72 0.000081 27 

Females 13~49 years old 0.000265 88 . 0.000099 33 

l11 %PAD text that is in bold reflects exceedances 

Table 3-12 Dicrotophos Steady State Dietary Exposure forMS at Cotton Typical Rate 

: ,~esults of Steady State Dietary Exposure Analysis for Dicrotophos 

(Food and Drinking Water) NCCotton Typical Rate 

...... . ., Conservative NAWQA . PRZM/EXAMS Chronic Water 

' Concentration 0.80 ppb Monitoring Data Water 

Population Subgroup .·· PAD 95th Percentile Concentration 0.30 ppb 

•••••• 

(mkd) , .. · 95th Percentile 

Exposure .· % PAD11 Exposure % PAD11 

' ····· . 

. , (mkd) : ·' (mkd) -

GeneraiU.S. Population 0.000197 66 0.000074 25 

All Infants (<1 year old) 0.000369 I .. .120.•. ' .,: . 0.000138 45 

Childrenl-2 years old / 0.000251 84 0.000094 32 

Childreh3-5 years old 0.000219 73 0.000082 27 

Children 6-12years old 0.0003 0.000196 65 0.000074 24 

Youth 13-19 years old ,•·•••• ,, 0.000195 65 0.000073 .· 24 

Adults20~49 years old 0.000197 66 0.000074 25 

Adults 50~99 years old ··: 0.000156 52 0.000059 20 

Females 13-49 years old ••••••••••••• .• , •. > 0.000197 66 0.000074 25 

l11 %PAD text that is in bold reflects exceedances 

Page 25 of34 
Table 3-13 Dicrotophos Steady State Dietary Exposure for TX at Cotton Maximum Rate 

' Results of Steady State Dietary Exposure Analysis for Dicrotophos < 

. ,. (Food and Drinking Water) TX Cotton Maximum Rate ..... 

Conservative NAWQA ·, 

PRZM/EXAMS Chronic Water .·· 

Concentration 0.80 ppb Monitoring Data Water 

PAO Concentration 0.30 ppb ··· .. 

Population Subgroup 95th Percentile 

(mkd) '· ... .,· 95th Percentile 

·' Exposure % PAD11 .·.·· 

Exposure % PAD11 

(mkd) 

. ········ .. 

.. (mkd) 

General U.S. Population ·.·· 0.000261 87 0.000098 33 

All Infants (<1 year old) 0.000573 · .. , ..•. . ": ...... 

····. i90·': .; 

0.000215 71 

Children 1-2years old 0.000345 . · ... · ~20 .. k:: 0.000129 45 

Children 3~5years old . 0.000244 81 0.000092 30 

Childrerl6-12 years old 

... 

0.0003 0.000245 82 0.000092 31 

Youth 13-19yearsold ",: 0.000225 75 0.000084 28 

Adults 20-49 years old 0.000259 86 0.000097 32 

Adults50-99years old 0.00021 70 0.000079 26 

Females 13-49years old 0.000264 88 0.000099 33 

1/ %PAD text that is in bold reflects exceedances 

Table 3-14 Dicrotophos Steady State Dietary Exposure for TX at Cotton Typical Rate 

Results ofSteady State Dietary Exposure Analysis for Oicrot()phos ':· .'· 

.. , (Food and Drinking Water) TX .Cotton Typical. Rate · . .·.··':,, 

PRZM/EXAM$ Chronic Water 

Conservative NAWOA ·.·'. ... . . 

Concentration 0.80 ppb Monitor'ingDataWater ., 

Population Subgroup PAD 95th Percentile Concentration 030 ppb 

(mkd) ·,. 95th Percentile 

Exposure % PAD11 Exposure % PAD11 

.... ,. (mkd) (mkd) 

General US Population 0.000197 66 0.000074 25 

Alllnfants(<1year old) 0.00036 . < ';. 

:: 1~{).~:< .·· 0.000135 45 

Children 1-2years old 0.000246 82 0.000092 31 

Children 38years old 

••••• 

0.000217 72 0.000081 27 

Children 6-12years old 0.0003 0.000196 65 0.000074 24 

Youth 13-19 years old ..• ,. 0.000195 65 0.000073 24 

Adults 20-49 years old 0.000196 65 0.000074 24 . . 

Adults 50-,99 years old '· 0.000157 52 0.000059 20 

Females BA9 years old '•• 0.000197 66 0.000074 25 

j1; %PAD text that is in bold reflects exceedances 

Page 26 of34 
4.0 SPECIFIC COMMENTS 

The comments below are specific to inconsistencies, errors, or issues identified in the text of the 

cited documents. Page numbers and paragraph numbers are provided to assist the reviewer in 

locating the specific information, and recommendations are made for adjustments. 

4.1.1 EPA memorandum of July 10, 2014: (PC Code: 035201; DP Barcode 393772); 

"Dicrotophos: Drinking Water Assessment for Reregistration Review", by 

Andrew Shelby (Physical Scientist) Environmental Risk Branch 6. 

1. Within the opening section, 1st pp., EPA states, "Given current uncertainty, the following 

degradates are included in the TTR approach:" 

AMV AC's comment: Several metabolites listed as a component of the residue of 

toxicological concern are not appropriate for inclusion. AMY AC agrees with the 

Agency's approach of including metabolites/degradates formed from dicrotophos for 

which an organophosphate structural component is maintained when there is an absence 

of data concerning the toxicological characteristics of the compound. However, inclusion 

of compounds that do not maintain this structural feature should be excluded. Such 

compounds would not be predicted to inhibit cholinesterase activity, which is the 

mechanism of toxicity that is being considered in the risk assessment. Therefore, even if 

these compounds were to have toxicological properties, combining the residues in an 

assessment for cholinesterase inhibition is not appropriate. Compounds that should be 

excluded from the grouping of residues used for the cholinesterase inhibition-based 

assessment are the ~-oxo-amides SD 6167 and SD11733. 

2. Within the opening section, 1st pp., EPA states, "Based on modeling results, the 

maximum estimated surface water exposure concentrations for total toxic residues of 

dicrotophos and assuming maximum application rates for current uses are: 12.44 11g/L for 

the 1 in 10 year annual peak concentration 0.80 11g/L for the l-in- 10 year annual 

average, and 0.4lllg/L for the 30 year annual average" [Note typographical error with 

inconsistencies in punctuation] 

AMVAC's comment: Aside from our comment concerning the definition of total residues 

of toxicological concern, it is important to note that this assessment is not fully refined 

and does not consider exposure estimates that would be relevant to the current label with 

its associated mitigation measures. Also, within PRZM-EXAMS modeling, the 

important input parameter for aerobic aquatic metabolism utilizes a subjective policybased correction factor to account for limitations in the dataset. This approach should be 

recognized as being highly conservative as there is no data that would indicate that the 

actual half-life would be extended to this extent. For these reasons, the modeling 

described in this document should be referred to as a screening level assessment. 

Page 27 of34 
3. Within the opening section, 1st pp., EPA states, "Based on modeling results, the 

maximum estimated groundwater exposure concentration for total toxic residues of 

dicrotophos is 0.05 (SCIGROW) to 0.06 Jlg/L (PRZM-GW) for acute and chronic 

exposure." 

AMVAC's comment: Aside from our comment concerning the definition of total residues 

of toxicological concern, it is important to note that this assessment is not fully refined 

and does not consider exposure estimates that would be associated with the current label 

and its associated mitigation measures. Also, within PRZM-EXAMS modeling, the 

important input parameter for aerobic aquatic metabolism utilizes a subjective policybased correction factor to account for limitations in the dataset. This approach should be 

recognized as being highly conservative as there is no data that would indicate that the 

actual half-life would be extended to this extent. For these reasons, the modeling 

described in this document should be referred to as a screening level assessment. 

4. Within the section "Fate and Transport Characterization", 1st pp., EPA states, 

"Dicrotophos is relatively more persistent to hydrolysis with a half-life of72 days (MRID 

160823)." 

AMVAC's comment: The Agency might clarify that this half-life is associated with 

neutral pH conditions. 

5. Within the section "Fate and Transport Characterization", 1st pp., EPA states, 

"Dicrotophos is stable to hydrolysis (MRID 160824)." 

AMV AC' s comment: We believe that the Agency is intending to refer to photolysis in 

aqueous solution, not hydrolysis. 

6. Within the section "Drinking Water Exposure Modeling", Table 1., EPA states, "Table 1. 

PRZMIEXAMS input parameter values for dicrotophos. Use on cotton and tree 

injections." 

AMVAC's comment: The use on cotton being modeled is for aerial application and that 

should be reflected in the title. 

7. Within the section "Drinking Water Exposure Modeling", Table 1., EPA states, "(An Rf 

study indicates SD 6167 is likely more mobile than parent dicrotophos [MRID 160829]." 

AMV AC' s comment: The mobility of the ~-oxo-amide SD 6167 SD should be 

considered irrelevant to an exposure assessment for dicrotophos for reasons previously 

stated; thus the note should be removed from the table. 

Page 28 of34 
8. Within the section "Drinking Water Exposure Modeling", Table 1., EPA states, 

"Hydrolysis Half-life (days) 72 (parent) 990 (TTR)" 

AMVAC's comment: The inclusion of the ~-oxo-amide SD 6167 has an effect on the 

half-life value associated with the TTR. For reasons previously stated, it is not 

appropriate to include this compound in the exposure assessment. On day 28 of the 

hydrolysis study utilized in this assessment, residues of this component accounted for 

4.8% of the total radioactive residue in the pH 7 test system. Inclusion of this residue 

yields inappropriate bias in the assessment. 

9. Within the section "Drinking Water Exposure Modeling", Table 1., EPA states, "Aerobic 

Soil Metabolism Half-life (days) 8.1 (parent) 8.7 (TTR)" 

AMVAC's comment: The inclusion of the ~-oxo-amide SD 6167 has an effect on the 

half-life value associated with the TTR. For reasons previously stated, it is not 

appropriate to include this compound in the exposure assessment. Residues associated 

with SD 6167 represent the difference in the values between the assessment for parent 

compound and for TTR. Therefore, inclusion of this residue yields inappropriate bias in 

the assessment. 

10. Within the section "Drinking Water Exposure Modeling", pp.6, EPA states, "The 

modeling of parent only and typical rates is performed for characterization and should be 

considered for quantitative purposes with the caveat that the values are not conservative 

in all cases. For instance, the parent only typical use rate EDWC for cotton in 

Mississippi is 5.85 ppb. However, monitoring data indicate that concentrations of 6.83 

ppb occurred in Mississippi in 2005 when dicrotophos had the same use pattern and rates 

as modeled in this assessment. Though the next highest detection was less than 0.3 ppb, 

one detection is indicative that similar concentrations could occur in other surface waters 

or at the same site at a different time but are not recorded. This monitoring data is 

derived from a targeted effort on the Boque Phalian a cotton predominant watershed, in 

which dicrotophos concentrations were determined approximately every 14 days." 

AMVAC's comment: It is not appropriate to place any significance on a single "high" 

sampling finding amongst a overall NA WQAIPDP database comprised of ca. 8,500 

samples. There are no residues even with the range of an order of magnitude below this 

value, which indicates that this value may be an outlier and may not be reflective of the 

real distribution. What is most notable is the finding that residues of dicrotophos in 

surface water, including waters in targeted sites, produce a consistent pattern of low level 

exposures. This provides strong assurance that there is only low level exposure to 

dicrotophos in drinking water from surface water sources, even without any water 

treatment or conditioning. 

11. Within the section "Drinking Water Exposure Modeling", pp.6, EPA states, "As 

concentrations vary with weather, application patterns and subsequent dissipation, the 

Page 29 of34 
likelihood of capturing the peak concentration diminishes with a sampling interval of 14 

days. Based on an analysis of a more complete monitoring dataset for atrazine, the 

average bias factor on a sampling interval of 14 days for estimating a 60-day rolling 

mean was approximately 4 with a 95% confidence interval of approximately 7 (SAP, 

2012). Due to differences in exposure window and the variability in field conditions, 

these bias factors cannot be directly applied to dicrotophos monitoring data though they 

would likely be higher when estimating an acute concentration and lower for an annual 

average. However, the bias factors illustrate the uncertainty associated with identifying 

6.83 ppb as the highest concentration occurring in dicrotophos use areas. Given these 

uncertainties, the use ofEDWCs derived from typical rates and/or parent only model 

simulations should only be done with caution and the awareness that it may not 

conservatively represent dicrotophos concentrations in all documented instances." 

AMVAC's comment: We agree that the sampling interval associated with field 

monitoring is critical to defining peak concentrations at specific sites. However, when 

the assessment is applied to an extensive survey such as the ca, 8,500 sample as 

associated with the NA WQA/PDP database, a better indication of peak concentration 

levels can be achieved. 

Further, for a compound such as dicrotophos that appears to rapidly dissipate in a water 

compartment, it is likely that the measured chemical concentration in the grab sample 

would be higher than the concentration at the time of exposure to a consumer, although 

this reduction factor has not been defined. We also find that utilizing the atrazine dataset 

for estimating the peak level concentration for dicrotophos is unreliable, especially when 

the bias factor is being applied to a single sampling result. Further, the environmental 

fate attributes and use practices of the herbicide atrazine are different from that of the 

insecticide dicrotophos; so applying surrogate bias factors is not well supported. 

Finally, it is also important to recognize that the fact that the single "high" sample 

concentration of 6.83 ppb appears to be an outlier within the distribution may indicate 

that the finding is attributable to some form of product misuse or a site spill. As indicated 

earlier in this report, there is also a question concerning the integrity of this result as there 

was not the expected correlation between discharge rate and analytical concentration. 

Therefore, without additional information, it is not appropriate to assert any significant 

meaning to this isolated finding. 

Page 30 of34 
4.1.2 EPA memorandum of July 10, 2014: (PC Code: 035201; DP BarcodeD418103); 

"Dicrotophos: Acute and Steady State Aggregate Dietary (Food and Drinking 

wate1~ Exposure and Risk Assessments to Support Registration Review", by 

Thurston Morton (Chemist) Risk Assessment Branch IV, Health Effects 

Division (7509P). 

1. Within the "Executive Summary" section, "Steady State Dietary (Food and Drinking 

Water) Exposure results and Characterization", 2nd pp., EPA states, "An unrefined 

steady state dietary exposure assessment was conducted to estimate the dietary risks 

associated with the registration of dicrotophos. The steady state dietary exposure 

assessment incorporated tolerance level residues and 100% crop treated. The steady state 

aggregate dietary exposure estimates from Calendex are above RED's level of concern(> 

100% of the PAD) for the U.S. population and all population subgroups. Combined 

dietary exposure from food and drinking water is 136% of the PAD for the U.S. 

population and 358% of the PAD for children 1-2 years, the most highly exposed 

population subgroup." 

AMVAC's comment: We have already confirmed with EPA that these values are in error 

and the highest exposed subpopulation group is the all infants (<1 year old). The 

combined dietary exposure from food and drinking water at the 95th percentile for the 

U.S. population ranges from 66 to 92% ofthe PAD, which does not exceed RED's level 

of concern. The combined dietary exposure from food and drinking water at the 95th 

percentile for the all infants (<1 year old) population subgroup ranges from 120 to 210% 

of the PAD, which exceed RED's level of concern. As EPA has indicated, these 

exceedances result in a slight overestimation of exposure as the assessment assumes 

tolerance level residues and 100% crop treated. Also, water exposure is based on a 

screening level assessment of surface water exposure using PRZMIEXAMS that can be 

refined as indicated previously in this document. 

2. Within the "IV. Drinking Water Data" section, 1st pp., EPA states, "This assessment uses 

maximum rates but considers typical rates though monitoring data exceeds the resulting 

EDWCs in some instances." 

AMVAC's comment: The only EDWC exceedance of which we are aware is the single 

NA WQA sample finding of 6.83 ppb out of a database of 8,500 samples. These fmdings, 

especially when considered on the basis a statistical distribution would indicate that the 

PAD would not be exceeded or at most only at a probabilistic level exceeding the 99 .9th 

percentile. 

3. Within the "IV. Drinking Water Data" section, 1st pp., EPA states, "The assessment 

considers a parent only approach but also considers the major degradates as parent in a 

total toxic residue (TRR) approach." 

AMVAC's comment: Within our comments to the EPA memorandum of July 10,2014: 

(PC Code: 035201; DP Barcode 393772); "Dicrotophos: Drinking Water Assessment for 

Reregistration Review", by Andrew Shelby (Physical Scientist) Environmental Risk 

Page 31 of34 
Branch 6, we explained our views for proposing that the total toxic residue definition be 

redefined to exclude metabolites/degradates that do not maintain an organophosphatebased structural functionality. On this basis, the EDWC exceedances overstate exposure. 

4. Within the "N. Drinking Water Data" section, 1st pp., EPA states, "Given current 

uncertainty, he following degradates are included in the TTR approach:" 

AMVAC's comment: The referenced information is not provided. 

5. Within the "VI. CALENDEX-DCID Program" section, 2nd pp., EPA states, "RED's 

steady state assessment considers the potential risk from a 21-day exposure duration 

using a 3-week rolling average (sliding by day) across the year. For this assessment, the 

same food residue values used in the acute assessment were used for the 21-day duration. 

In the Calendex, one diary for each individual in the WWEIA is selected to be paired 

with a randomly selected set of residue values for each food consumed. For the water 

residue values, Calendex incorporates PRZM-EXAMs drinking water residue by 

selecting a year at random from those available in the designated drinking water residue 

file." 

AMVAC's comment: Although the process being used by RED represents a reasonable 

initial screening approach, the availability of a large surface water monitoring database 

that includes targeted sampling provides an opportunity for refining the water exposurebased and aggregate risk assessments. 

6. Within the "VIII. Results/Discussion" section, 2nd pp., EPA states, "For food and 

drinking water, the acute dietary risk estimate is below RED's level of concern at the 

99.91

h percentile of exposure. The acute dietary exposure using DEEM was estimated for 

the U.S. population is 13% of the aPAD and 27% for all infants (<1 yrs old), the most 

highly exposed population subgroup. The steady state aggregate dietary (food and 

drinking water) exposure estimates using Calendex are above RED's level of concern for 

the U.S. population and all population subgroups. Combined dietary exposure from food 

and drinking water is 136% ofPAD for the U.S. population and 358% of the PAD for 

children 1-2 years, the most highly exposed population subgroup." 

AMV AC' s comment: Based on conversations with EPA, we have confirmed that the 

information within this text is incorrect and refers to that of another chemical. 

7. Within the "IX. Characterization of Inputs/Outputs" section, 1st pp., EPA states, "RED 

hass conducted unrefined acute and steady state dietary risk assessments for coumaphos. 

OPs exhibit a phenomenon known as steady state Ache inhibition and for coumaphos a 

steady state endpoint was selected. Although, there are rat data at a shorter period (i.e., 

15 days) than 21 days, exposure assessments of21 days and longer were conducted for 

all routes of exposure (i.e., oral, dermal and inhalation) for all single chemical OP 

assessments using Calendex. Given this, the 21-day and longer exposure assessment is 

scientifically supportable and also provides consistency across the OPs." 

Page 32 of34 
AMVAC's comment: Based on conversations with EPA, we have confirmed that the 

inf01mation within this text is incorrect and refers to that of another chemical. 

8. Within the "X. Conclusions" section, 1st pp., EPA states, "these unrefined analyses 

demonstrate that the requested uses for dicrotophos will not result in acute dietary risk 

estimates that exceed HED' s level of concern for any of the regulated population 

subgroups, including those comprised of infants and children." 

9. AMVAC's comment: The acute dietary risk estimates at the 95th percentile does not 

exceeds the aP AD for any of the subpopulation groups. This would indicate that acute 

aggregate exposure would not of concern. 

Page 33 of34 
5.0 REFERENCES USED IN THE ASSESSMENTS 

ESRI. 2014. ArcGIS Desktop: Release 10. Redlands, CA: Environmental Systems 

Research Institute. 

G.P. Thelin and W.W. Stone. (2013). Estimation of Annual Agricultural Pesticides Use 

for Counties of the Conterminous United States, 1992-2009, Scientific Investigation 

Report 2013-5009. [Online]. Available: 

http:/ /pubs. usgs.gov /sir/20 13/5009/pdf/sir20 135009 .pdf 

USDA 2006. Mississippi Cropland Data Layer for 2005. U.S. Department of Agriculture 

(USDA), National Agricultural Statistics Service (NASS), Research and Development 

Division (RDD), Geospatial Information Branch (GIB), Spatial Analysis Research 

Section (SARS), Washington, D.C. [Online]. Available: 

http:/ /www.nass. usda.gov /research/Cropland/metadata!metadata _ ms05 .htm 

USEPA. 2006. Data quality assessment: Statistical methods for practitioners, EP A/240/B06/003 [Online]. Available: http://www.epa.gov/QUALITY/qs-docs/g9sfinal.pdf 

USEPA. 2013. ProUCL Version 5.0.00 Technical Guide, EPA/600/R-07/041 [Online]. 

Available: http://www.epa.gov/osp/hstl/tsc/ProUCL v5.0 tech.pdf 

USGS. 2009. National Water Quality Assessment (NAWQA) Database. U.S. Geological 

Survey, Washington, DC. [Online]. Available: http:/ /water.usgs.gov/nawqa/about.html 

[Accessed: 18-Nov-2014] 

USGS. 2014. USGS Stream Gage Station ID 07288650 at Bogue Phalia near Leland, MS. 

[Online]. Available: 

http://waterdata.usgs.gov/nwis/nwismap/?site no=07288650&agency cd=USGS 

Page 34 of34 
Appendix 3 
STUDY TITLE 

Response to EPA's Preliminary Environmental Fate and Ecological Risk Assessment for 

Dicrotophos 

TEST GUIDELINE: 

None 

AUTHORS: 

R. Scott Teed1 

Colleen Greer2 

Gillian Manning1 

Dick Freedlander3 

STUDY COMPLETION DATE: 

November 28, 2014 

PERFORMING COMPANIES: 

1 Intrinsik Environmental Sciences, Inc. 

1125 Colonel By Drive 

Carleton University Campus 

CTTC - Suite 2600 

2

Intrinsik Environmental Sciences (US), Inc. 

Ottawa, ON K1 S 5R1 

Cumberland Hall (Pineland) 

41 Campus Drive, Suite 202 

New Gloucester, ME 04260 

PROJECT NUMBER: 

Intrinsik Project #60-60625 

AMVAC Report ##800-REV-021 

PREPARED FOR: 

3 AMV AC Chemical Corporation 

4695 MacArthur Court, Suite 1200 

Newport Beach, CA 92660 

TOTAL PAGES: 

56 

Page 1 of56 
NO CLAIM OF CONFIDENTIALITY 

No claim of confidentiality, on any basis whatsoever, is made for any information contained in 

this document. I acknowledge that information not designated as within the scope of FIFRA sec. 

1 0( d)(1 )(A), (B), or (C) and which pertains to a registered or previously registered pesticide is 

not entitled to confidential treatment and may be released to the public, subject to the provisions 

regarding disclosure to multinational entities under FIFRA 1 O(g). 

Company: AMV AC Chemical Corporation 

Company Agent: Dick Freedlander 

Director Environmental Sciences 

AMV AC Chemical Corporation 

Signature: ---~...__-=----------=-------

Date: \ \ \ 2-55 J z..n \ '-\ ------~---------------

Page 2 of 56 
GOOD LABORATORY PRACTICE COMPLIANCE 

This study does not fall under EPA FIFRA Good Laboratory Practice (GLP) Standards set forth 

in Title 40, Part 160 of the Code of Federal Regulations. 

Submitter: 

Signature: Date: 

Dick Freedlander 

Director 

Environmental Sciences 

AMV AC Chemical Corporation 

Page 3 of 56 
TABLE OF CONTENTS 

1.0 EXECUTIVE SUMMARY ............................................................................................................... 5 

2.0 INTRODUCTION ............................................................................................................................ 7 

3.0 GENERAL COMMENTS ................................................................................................................ 8 

3.1 Use Patterns .................................................................................................................................. 8 

3.2 Selection of Screening-level Effects Metrics ................................................................................ 8 

3.2.1 Birds and Mammals .............................................................................................................. 8 

3.3 Exposure Modeling ....................................................................................................................... 9 

3.3.1 AgDrift ................................................................................................................................ 10 

3.3.2 T-REX ................................................................................................................................. 12 

3.3.3 STIR .................................................................................................................................... 16 

3.3.4 SIP ....................................................................................................................................... l7 

3.4 Supporting Documentation ......................................................................................................... 18 

3.4.1 Refined Deterministic Assessment ..................................................................................... 18 

3.4.2 Incident Reports .................................................................................................................. 21 

3.4.3 Field Studies ........................................................................................................................ 22 

3.5 Conclusions ................................................................................................................................. 23 

4.0 SPECIFIC COMMENTS ................................................................................................................ 25 

5.0 REFERENCES ............................................................................................................................... 41 

List of Tables 

Table 2-1 Summary of risk quotient results for birds and mammals associated with cotton fields .... 20 

List of Appendices 

APPENDIX A Refined Deterministic Total Daily Intake Models for Birds and Mammals that Frequent 

Cotton Fields ............................................................................................................................................... 46 

APPENDIX B EllS Incident Reports for Dicrotophos ............................................................................... 54 

Page 4 of 56 
1.0 Executive Summary 

Dicrotophos is a systemic broad spectrum organophosphate insecticide. It is currently 

manufactured by AMV AC Chemical Corporation (AMV A C) under the trade name Bidrin 8 and 

Bidrin XP II. The current AMV AC label for dicrotophos is limited to use on cotton. Recently, 

the Environmental Protection Agency (EPA), Office of Pesticide Programs provided a screeninglevel ecological risk assessment (ERA) for dicrotophos that looked at environmental fate and risk 

to plants and wildlife (EPA, 2014 ). The ERA is highly conservative and suggests that use of 

dicrotophos in cotton fields may be of concern to birds and mammals (EPA, 2014 ). The Agency 

used a weight-of-evidence approach when drawing these conclusions. The Agency applied the 

highly conservative screening-level toolbox models (e.g. T-REX, T-HERPS, SIP, STIR) and 

reviewed additional information on incident reports and field study results. 

The Agency conclusions in the ERA report (EPA, 2014) suggest there may be risk to birds and 

mammals, and terrestrial invertebrates. Therefore, given the highly conservative assumptions 

used in this screen, a more refined risk characterization is required. In this report, Intrinsik 

Environmental Sciences Inc. (Intrinsik) and AMV AC provide examples of appropriate 

refinements for risk characterization. For example, by substituting the default screening level 

foliar dissipation decline with a more appropriate pattern relevant to dicrotophos; using a more 

refined free metabolic rate (FMR) approach in the total daily intake models in place of the 

baseline food intake rate (FIR) approach used in T-REX; and, by recognizing the metabolic 

patterns associated with dicrotophos, a somewhat more refined deterministic risk assessment is 

provided for several mammalian and avian focus species. These results yielded risk quotients 

that were significantly lower than those calculated by the Agency (EPA, 2014): 

Species Refined Risk T-REX Short 

Quotient (RQ) Grass RQa 

Indigo bunting (Passerina cyanea) 3.0 463.3 

Northern cardinal (Cardinalis cardinalis) 0.9 463.3 

American widgeon (Anas americana) 1.5 65.8 

Female meadow vole (Microtus pennsylvanicus) 5.6 9.8 

Male meadow vole (Microtus pennsylvanicus) 4.1 9.8 

Female deer (Odocoileus virginianus) 1.6 5.2 

Male deer (Odocoileus virginianus) 1.1 5.2 

a - Based on the short grass RQ calculated for the appropnate we1ght class of each of the spec1es l!sted. 

The current set of refinements that are described in this report do not take into account other 

important considerations that would further lower the RQ values. For example, the extent of 

cotton field utilization for foraging by different animal species for which data that are readily 

available in the field studies for dicrotophos. Also, recovery from exposure effects due to 

dicrotophos should be taken into account. As with most acetylcholinesterase inhibitors, exposed 

organisms that do not exceed an exposure concentration that leads to mortality will recover 

rapidly from the exposure. 

A review of the remaining weight of evidence in the Agency's assessment refines the Agency's 

initial assessment. Given that cotton fields do not provide a good source of nutrition to most 

Page 5 of 56 
animal species provides in itself some rationale as to why this use would not impact wildlife. 

Although field studies have been conducted in the past to assess the potential impact of 

dicrotophos use in cotton on avian species, these study results were confounded by the 

concurrent use of many other chemicals of potential toxicological concern, including 

organophosphates that were applied to the same treated fields. The reported incident reports in 

the EllS and the peer reviewed literature suggest that the primary cause of avian and mammalian 

mortality is human error and illegal use of the product. In addition, only one incident was 

associated with cotton use (all other use patterns have been removed from the label) and 

according to the incident database, it was unlikely to be associated with dicrotophos use. 

Overall, refined modeling and important ancillary information provides a basis for concluding 

that dicrotophos use on cotton would not pose an unacceptable ecological terrestrial risk to avian 

and mammalian species. 

Page 6 of 56 
2.0 INTRODUCTION 

The Environmental Protection Agency (EPA) released their Preliminary Environmental Fate and 

Ecological Risk Assessment (ERA) for the Registration ofDicrotophos in July, 2014. In that 

report the Agency outlined their preliminary ecological risk assessment conducted by EPA under 

the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) for registration review of 

dicrotophos. 

Dicrotophos is a systemic broad spectrum organophosphate insecticide with a mode of action 

that interferes with the acetylcholinesterase enzyme (AChE). AMV AC Chemical Corporation 

(AMV AC) currently manufactures two end-use products that contain dicrotophos; Bidrin® 8 

(82% dicrotophos) and Bidrin XP IITM (50.7% dicrotophos + 11.2% bifenthrin). Bidrin® 8 and 

Bidrin XP II are only proposed for use on cotton through both aerial and ground application. 

As part of the registration review process, AMV AC has retained Intrinsik Environmental 

Sciences Inc. (Intrinsik) to jointly review the preliminary ERA for dicrotophos with respect to 

the potential risks to birds and mammals. AMV AC and Intrinsik have a number of comments 

with regard to EPA's preliminary ERA contained in this report. The report has two main 

sections. Section 2 provides general comments on the approaches used by the Agency in 

developing their exposure, effects, and risk characterization. Additional analyses are provided in 

Section 2 for consideration by the Agency. Section 3 contains specific comments on the report 

including typographic errors, data or calculation errors, and other specific comments and 

recommendations. 

Page 7 of 56 
3.0 GENERAL COMMENTS 

The following general comments address key issues that AMV AC and Intrinsik have identified 

within EPA's preliminary ERA. 

3.1 Use Patterns 

There have been significant changes to the use patterns for dicrotophos since it was first 

registered in the United States. AMV AC is currently only supporting use on cotton and has 

implemented significant mitigation measures on the labels. Therefore much of the historical 

information on monitoring data, incident reports, and field study results (EPA, 2014) do not 

provide the proper context for current dicrotophos use. Care must be taken in the use of this type 

of evidence when discussing the potential risk of dicrotophos use on cotton. This is discussed 

further in the report. 

3.2 Selection of Screening-level Effects Metrics 

3.2.1 Birds and Mammals 

The avian effects metrics used by EPA (20 14) were based on past registrant submitted studies. 

For example Shell Research Ltd. submitted a study by Doyle and Elsea (1963) [MRID 

00013439] to the Agency in 1966. The study was conducted with domestic goose (Anser anser), 

a non-guideline species and had the lowest oral dose (LD50) of the studies surveyed. However, 

the dose was administered once via stomach tube and the response was either no effect (0% 

mortality) or 100% mortality at an order of magnitude higher dose (0.385 to 3.85 mg ai/kg bw). 

Estimation of an LD50 with no intervening exposure concentrations is uncertain and dependent 

upon the model used to estimate the dose-response relationship. 

A closer review of the selected acute effect metric for domestic goose used in the assessment 

suggests that there are many deficiencies in the study (Doyle and Elsea (1963)) [MRID 

00013439]. The study did not follow Good Laboratory Practice (GLP), which is a reflection of 

the age of the study. It is unclear from the report whether a standard guideline or protocol was 

followed. Similarly, the study lacks details on study design and conditions, and processing of the 

results. For instance, the tested chemical was not properly characterized. The age, sex and weight 

of the birds were not reported, and it is unknown whether the geese were acclimated prior to 

testing. Basic test conditions such as light intensity, photoperiod and temperature were not 

reported. Moreover, the report did not state whether controls were used. Lastly, the statistical 

procedure for evaluating results was not reported. As a result, this study is insufficient in terms 

of data reporting in accordance with OPP's evaluation guidelines (EPA, 2011a). 

Additionally, the goose study was selected because it appeared to be the most sensitive endpoint 

available. With consideration of using this endpoint for predicting the LD50 for a much smaller 

bird, the Mineau body scaling factor (EPA, 2012a) cannot be calculated since animal weight in 

Page 8 of 56 
the goose study was not reported. Relationships between body weight and toxicity as predicted 

by the Mineau scaling factor for dicrotophos are herein called into question (see Section 2.3.2). 

Stomach tube or oral gavage exposure pathways do not accurately reflect exposure of birds and 

mammals in the field (ECOFRAM, 1999). In gavage studies, the effects of dietary matrices, 

feeding patterns, metabolism, and elimination throughout the day are not accounted for. The fact 

that dietary LD50s are generally much higher than gavage LD50s is attributed to these factors. 

EPA (2014) also presented risk results based on dietary exposures. Typical guideline acute 

dietary studies have a five day exposure period followed by three days of observation. However, 

the toxicity study selected by EPA (20 14) was actually 28 days in length. This is more 

representative of a chronic exposure period and would likely result in a lower LC50. Comparison 

of a five day environmental exposure concentration (EEC) to an effect metric from a 28 day 

chronic effect metric would result in a significant overestimation of risk. 

For chronic exposure, EPA (2014) used the NOEC (1 ppm) from a mallard duck reproduction 

study. The NOEC was based on an 8% reduction in female body weight at the next highest 

treatment level (3 ppm). However, an 8% reduction in female body weight should not be 

considered ecologically relevant as such small changes would reflect natural variability. 

Certainly, minor reductions in body weight in the laboratory are unlikely to be realized in the 

field as birds are mobile and will spatially average their daily exposure. These minor effects on 

body weight are unlikely to result in population level effects particularly as dicrotophos is 

applied only twice a year within 14 days for crop protection, and recovery from 

acetylcholinesterase (AChE) inhibition tends to be rapid (Fleming et al. 1981; Fleming and Grue, 

1981). 

Overall, the avian effects metrics chosen by EPA (20 14) for their preliminary ERA were overly 

conservative, utilized certain studies with important data deficiencies, and not consistent with 

conditions expected in the field. Further, a more recent literature study on starlings provides a 

better basis for calculating dose-based dietary risk (Grue and Shipley, 1984). Within this study, 

the LD50s for sensitive starling nestlings and adults were determined to be 4.92 and 8.37, 

respectively. This study provides sufficient detail for validating the findings. Although there is 

a better basis for assessing dose-based exposure, a more accurate assessment can be developed 

by selecting effects metrics that are dietary-based and demonstrate significant effects beyond 

what would be predicted by natural variability. 

3.3 Exposure Modeling 

EPA used their standard screening-level modeling toolbox to evaluate dicrotophos. These models 

can be found at http://www.epa.gov/oppefedllmode1s/terrestrial/. These models are intended to 

be highly conservative and serve as a screen to determine whether a more refined assessment is 

required. This approach generally uses a comparison of a very sensitive effect metric to peak 

modeled EEC to generate a risk quotient (RQ). Risk quotients are then compared to EPA's levels 

Page 9 of 56 
of concern (LOCs) for threatened and endangered species (listed species) and non-listed species 

to characterize risk. A brief discussion of the models and their parameterization is provided in 

this section. 

3.3.1 AgDrift 

In their preliminary ERA, EPA (2014) uses AgDRIFT® (v.2.1.1) to model potential risk to birds 

and mammals to dicrotophos exposure from spray drift. In this document are a number of 

comments with regard to the spray drift model used to determine buffer distances for protection 

of listed and non-listed species. Empirical data from the Spray Drift Task Force (SDTF) used to 

develop AgDRIFT® for ground spray and orchard airblast were collected in the early 1990s. The 

nozzles and application equipment used in these studies now represent older technology, as they 

have been improved over the last 20 years to reduce drift. The aerial component of AgDRIFT® is 

an earlier version of AgDISP®, which was developed in 2002. Therefore, the built-in equipment 

scenarios represent nozzles and equipment no longer in general practice and used more than a 

decade ago. 

Crop Life America (CLA) submitted comments on the AgDRIFT model and associated guidance 

"Consideration of Spray Drift in Pesticide Risk Assessment" (docket EPA-H Q-0 PP-2013-067 6) 

to the Agency in 2013 (Leggett, 2014). AMVAC agrees with these comments and a summary of 

these comments is provided below: 

• The default scenarios for ground and aerial applications are atypical and offer few or no 

refinement options. Model parameters rarely reflect common agricultural practice for any 

of the application categories described. 

• AgDRIFT® relies exclusively on SDTF data collected over 20 years ago. The SDTF did 

not conduct applicator surveys to determine which application equipment or operating 

parameters were in common use, and instead selected nozzles and sprayers that 

represented the worst-case situation for drift. Thus, the studies were designed to overpredict drift at the time they were conducted. These data are useful in defining what an 

upper-bound of exposure might be, but the distribution of data should not be assumed to 

represent the distribution that would be observed from typical application practices used 

today. 

• Agriculture and Agri-Food Canada (AAFC) have recently produced high quality 

deposition data sets similar to those of the SDTF. AAFC trials were conducted in 2000, 

2004, 2006, and 2011, and included the use of more contemporary application equipment, 

including drift-reducing nozzle technologies. EPA has, so far, not considered these data 

due to the lack of quality assurance/quality control (QA/QC). CLA is committed to 

providing the QA/QC verification necessary for EPA to include the AAFC data in their 

decision making. EPA should include current information and best-available data when 

making registration decisions. 

Page 10 of 56 
• AgDRIFT® fits the SDTF data to a Gaussian curve, which is a weak predictor of the data 

at distance from the field edge. In using the Gaussian model, drift never dissipates 

completely, which is intuitively flawed. 

• SDTF data were combined in broad categories to generate drift curves applicable to all 

products. This eliminates the possibility of factoring in label mitigation options such as 

restrictions of droplet size in ground applications or mitigation by wind speed. Although 

not done in AgDRIFT®, it is possible to use F-test methodologies to determine which 

data sets may be combined to generate appropriate categories. 

• For ground application, AgDRIFT® assumes that the contribution of residues from 

successive passes is additive up to 20 swaths. This assumption needs to be examined 

because it exacerbates the tendency of drift curves to over-estimate drift at farther 

distances off the field. 

• The ability to conduct risk assessments for ground and orchard air-blast applications is 

currently restricted to AgDRIFT® Tier 1 and there is no opportunity to run more refined 

risk assessments at higher tiers. 

• RegDISP is a modification of AgDISP® that predicts spray drift deposition from ground 

applications of pesticides. Spray drift is calculated based on regression equations 

constructed from more recent empirical field data obtained from AAFC in addition to 

older data from the SDTF. The user can choose from the above-mentioned datasets by 

selecting study year, nozzle, boom height, sprayer speed, and wind speed. RegDISP also 

allows users to input regression equations constructed from their own data sets. RegDISP 

has been integrated with AgDISP® so that the user can choose whether to run AgDISP® 

for aerial applications or RegDISP for ground applications. Once a deposition equation 

has been selected, RegDISP estimates deposition as the fraction applied, and the 

deposition and stream assessment tools developed as part of the AgDISP interface can be 

run by the user. RegDISP has been shown to much more accurately predict spray drift 

than AgDRIFT®. 

The use of the AgDRIFT® model produces exaggerated over-predictions of drift for off-site 

movement of dicrotophos spray droplets in air, especially beyond 300 m from the treated field. 

AMV AC recommends that EPA: 

• consider current best available data in estimating drift deposition; 

• evaluate and apply RegDISP for regulatory use; 

• select model input parameters that reflect reasonable label-adherence, instead of worstcase assumptions; 

• provide a complete accounting of all input parameters used in the spray drift model(s); 

Page 11 of56 
• provide a discussion of the uncertainties and limitations of the drift model(s) used; if 

AgDRIFT® is used, conduct the exposure assessment only at distances that have been 

validated using empirical data and are considered acceptable by EPA (2004b, 2005); and 

• consider applying a correction factor to the predicted deposition based on the known 

overestimation of AgDRIFT®. 

3.3.2 Jr-Jll?)( 

The Terrestrial Residue Exposure Model (T-REX) is a wildlife exposure model that is primarily 

used to assess risk to birds and mammals. T-REX (v.1.5) was used to estimate terrestrial EECs 

on food items in the Agency's ERA (EPA, 2014 ). However, T -REX has a number of limitations 

and uncertainties that are listed below and can be addressed through the use of more refined 

modeling as provided in this report. 

• T-REX assumes birds and mammals forage 100% of the time on the treated field and thus 

their complete dietary intake comes from the treated field. This is highly conservative 

because most mobile species will forage on and off the field throughout a given day. This 

reduces the overall exposure experienced by the animal. However in T-REX, the maximum 

possible cumulative daily peak exposure is assumed. 

• The T-REX model conservatively assumes that wildlife obtain 100% of their diet from 

pesticide-treated locations immediately following application. Although this may be 

reasonable for a generic screening, the assumption is not applicable to all wildlife. Sullivan 

and Wisk (2012) illustrated how this assumption is improbable for many threatened and 

endangered birds by compiling foraging habitat data for the 89 listed species found in US 

states or territories. They found that less than 25% of bird species considered occurred 

adjacent to agricultural areas, with the largest percentage (37%) of species found foraging 

solely in forested habitat. 

• Kenaga nomograms (Fletcher et al. 1994; Hoerger and Kenaga, 1972) are the basis of residue 

unit doses (RUDs) in T-REX. They are upper bound values that are derived from data that do 

not reflect current pesticide applications (i.e., nozzles) and are not pesticide-specific. The use 

of these RUDs lead to an overestimate of exposure for dicrotophos in particular when the 

default foliar DT50 of 35 days is applied. Dicrotophos is known to rapidly degrade thereby 

reducing the availability of the pesticide compared to the average values available in T-REX. 

• T -REX assumes the animal eats 100% of a particular feed item (e.g., short grass). This is 

highly conservative because most species eat a varied diet and different feed items will have 

different amounts of residues (e.g., short grass has higher residues than seeds). For the short 

grass diet in particular, the modeled consumption of pesticide residues is much higher than 

the average because very few species subsist solely on short grass. 

Page 12 of 56 
• The size classes considered in T-REX include 20, 100, and 1000 g birds, and 15, 35, and 

1000 g mammals. It is unlikely that grasses (short and tall) and broadleaffoliage alone could 

provide sufficient energy for smaller wildlife species, considering the caloric needs of 

smaller animals on a cal/kg basis, and the time and energy demands of the foraging required 

to meet those needs. This deficiency is mentioned in the T-REX user manual with respect to 

short grass and the smallest weight class of birds and mammals. For threatened and 

endangered bird species, Sullivan and Wisk (2012) found that only one of the 89 threatened 

and endangered species they considered consume primarily grasses at any period in time 

(Hawaiian geese (~ 1500 g), in the winter). Thus, as short grass typically has the highest 

residue unit doses (RUD), exposure is considerably overestimated for birds and mammals 

(whether listed or non-listed). None of the other listed species evaluated by Sullivan and 

Wisk (2012) consumed only grasses and/or broadleaffoliage. 

• Residues are expected to differ among feed item categories. EPA has recognized that 

pesticide residues on terrestrial invertebrates can vary considerably, and have conducted 

refined exposure assessments (e.g., for wildlife consuming earthworms (EPA, 2007; EPA, 

2009a-d)). For realistic dietary exposure estimates, residues should be quantified for flying 

insects, surface and crop-dwelling arthropods, and soil-invertebrates, such as earthworms. 

Ideally, these estimates would be derived with end-use-product-specific data. However, it is 

recognized that ample arthropod residue data for pesticides such as dicrotophos are often 

lacking to derive pesticide-specific RUDs. 

• T-REX uses food intake rates that do not account for the assimilation efficiencies of the 

dietary items (i.e., some foods have higher energy content, which requires less consumption 

to attain required energy for survival). This results in higher food consumption than is 

probable in nature, thus increasing modeled exposure. 

• Food ingestion rate is estimated in T-REX with allometric equations derived from Nagy et al. 

(1987). However, more up-to-date estimates of field metabolic rates are available (Nagy et 

al., 1999) that include numerous bird species (n=95, compared to n=50 in Nagy et al. 

(1987)). Further, T-REX does not account for differences in assimilation efficiencies of the 

dietary items. This is an important consideration as the amount of energy obtained in the diet 

can vary depending on the feed item, which may impact overall food ingestion rates of an 

individual. For example, feeding the same dietary concentration to animals during toxicity 

testing does not necessarily lead to the same exposure for the same receptor species due to 

differences in food ingestion rates among species, body weights and diets. Therefore, average 

body weights and feed consumption should be used to calculate dietary endpoints used for TREX modeling (i.e., units ofmg ai/kg bw/day). 

• T-REX uses allometric scaling to calculate adjusted toxicity values for avian and mammalian 

species. In ecological risk assessments, the toxicity of chemicals to avian and mammalian 

Page 13 of 56 
wildlife is typically based on effects data derived from a limited number of laboratory 

species. Allometric scaling of toxicity data is an approach used by wildlife risk assessors to 

extrapolate toxic effects from species with data (i.e., test species) to species without (i.e., the 

wildlife receptors assessed in the risk assessment process). The use of allometric scaling in 

the interspecies extrapolation of toxicity data is based on the observation that numerous 

physiological processes directly associated with metabolism (e.g., uptake, distribution, 

biotransformation) are related to organismal responses to chemicals and follow a predictable 

relationship with body mass (Travis and White, 1988; Chappell, 1992; Mineau et al., 1996, 

Sample and Arenal, 1999). The slope of the line linking toxicity to body mass is equivocal 

and extrapolations based on body mass raised to the power of 0.6 to 1.5 have been suggested 

for use as toxicity scaling factors among species (e.g., for birds see Mineau et al., 1996; 

Sample and Arenal, 1999; for mammals see Davidson et al., 1986; Travis and White, 1988; 

Chappell, 1992; Sample et al., 1996; Bokkers and Slob, 2007). 

Support for the use of allometric scaling in the calculation of adjusted toxicity values for 

avian and mammalian species is provided in the EPA's T-REX guidance manual (EPA, 

2012a). For birds, acute toxicity test results (LD50) can be modified to an "adjusted LD50" 

following Equation 1 where "x" is EFED's recommended default, the Mineau bird scaling 

factor of 1.15 (Mineau et al., 1996). 

Body l1lGSS Species of Interest 

LD50 Species of lnlerest = LD50TestSpecies ( )

x-1 

Body massTest Species 

Equation 1 

With this scaling factor, sensitivity is inversely related to body size (i.e., smaller birds are 

more sensitive than larger ones). EPA notes that the Mineau scaling factor can be 

replaced by a chemical-specific scaling factor if data are available. A value of 1.0 (a 

slope indicative of no relationship with mass) can be entered if the assessor believes that 

body mass will not influence chemical toxicity. No method for the adjustment of chronic 

avian toxicity data is recommended by EPA (2012a). For mammals, the same equation 

(Equation 1) 1 is used to derive an adjusted toxicity metric with the bird-specific Mineau 

scaling factor replaced by a scaling factor of0.75. The mammalian equation leads to the 

opposite result produced with birds (i.e., smaller mammals are less sensitive than larger 

ones). Unlike for birds, however, EPA-EFED allows for adjustment to chronic 

mammalian toxicity using the same approach except that the acute LD50 term is replaced 

by the chronic no observed adverse effect level (NOAEL ). Mineau et al. (1996) 

1 Readers should note that in T-REX guidance manual the numerator and denominator from Equation 1 are inverted between 

birds and mammals. As a result, the exponents in the equations are different. In birds it is x-1, with x being the Mineau scaling 

factor. With mammals, a value of 0.25 is reported by EPA, which is the resulting value of 1-x, with x being the mammalian 

scaling factor of 0. 7 5. 

Page 14 of 56 
recommended a specific scaling factor of 1.118 for dicrotophos. However, the Agency 

used the default scaling factor of 1.15 in its ERA (EPA, 2014). Use of the scaling factor 

to extrapolate to very large mammals from typically rat toxicity study results is not 

recommended due to the significant uncertainty associated with that extrapolation. 

The application of allometric scaling to pesticide toxicity data is not without its 

drawbacks: allometric scaling is most useful for like chemicals with similar dispositions 

(Davidson et al., 1986; Chappell, 1992) and may not be applicable to wide range of 

chemicals; the use of allometric scaling may not be appropriate for chemicals that 

undergo biotransformation as the toxicity of metabolites may differ from parent 

compounds (Travis and White, 1988; EPA, 20 11a ); and almost all data linking allometric 

scaling to toxicity have done so using acute or sub-chronic data so the relationship to 

chronic data is lacking empirical support (Knopper et al., 2009). Although EPA allows 

for some level of adjustment, this guidance is not always applied in practice for 

pesticides. For example, for two organophosphate pesticides, dimethoate and malathion, 

both of which are transformed in vivo to equally or more toxic oxons, EPA has applied 

generic allometric scaling in their effects determination (EPA, 2008). The inappropriate 

use of allometric scaling can result in erroneous conclusions in risk assessments due to 

unsupported toxicity metrics. Also, and most importantly, dicrotophos, unlike many other 

organophosphates, is an oxon-based species; thus metabolism primarily leads to nontoxic species. Therefore, AMV AC believes that no scaling factor (i.e. scaling factor of 1) 

should be applied for dicrotophos for birds. 

The chronic risk estimation for dicrotophos in the T-REX model is incorrect because this 

model compares peak acute exposure estimates to chronic toxicity NOELs, which is a 

mismatch of toxicity endpoints and EECs. This approach significantly exaggerates the 

potential risk posed by non-persistent compounds such as dicrotophos. Exposure 

durations in chronic avian and mammalian studies are typically greater than 10 weeks 

(EPA, 1998a,b; 2012b). However, such exposures are unrealistic because dicrotophos 

degrades rapidly between applications, making pulse exposures far more relevant than 

maintained chronic exposure. In the absence of realistic pulse exposure toxicity data, 

EPA should consider including chronic averaging in T-REX to account for dicrotophos 

degradation between applications. 

• The use ofNOELs/NOAELs, or NOECs/NOAECs for evaluating chronic risks to non-target 

organisms has many shortcomings, including being very sensitive to study dose selection and 

sample size. It is for this reason and others that the OECD and other jurisdictions (including 

EPA's HED) have moved towards regression analysis to generate acute and chronic effects 

metrics rather than rely on hypothesis testing. 

Page 15 of 56 
• EPA (2014) has stated that dicrotophos is expected to degrade quickly in terrestrial 

environments (EPA, 2014- Section 2.5.2), but used a default degradation half-life of35 days 

in T-REX. Although no foliar dissipation data are readily available, the soil degradation and 

field dissipation half-lives are 2.7 and 2.2 days, respectively. Therefore, use of degradation 

half-life that is more than an order of magnitude longer than other degradation half-lives 

available in the current literature is extremely conservative and overestimates the availability 

of dicrotophos on food items. 

The dislodgeable foliar residue data that are available to the Agency demonstrates that 

residues decline with a half-life established at two different field sites of less than 2.33 days 

(Prochaska, 1978) [MRID 44728501]. It is recognized that these data do not account for the 

possibility of a different decline profile for residues that are not dislodged. Therefore, 

relative abundance of surface based residues versus residues within the target plant system is 

not clearly understood. In spite of a lack of certain information, EPA's designation of a 35-

day foliar half-life for modeling purposes is likely to be highly exaggerated. EPA has 

commented on this point and conducted a sensitivity analysis assuming a three day foliar 

half-life. The Agency determined that there was a 40% reduction in the RQs (e.g., 5.82 to 

3.44); but stated, "However, even if the data were available to reduce the foliar dissipation 

half-life used in the model to three days, all size class and forage class exceedances would 

remain, albeit not as far off-field as for the 35-day half-life assumption." Although this may 

be true, the inclusion of this refinement when combined with other refinements (e.g. free 

metabolic rate (FMR) approach, foraging time in the field, etc.) would significantly lower the 

potential exposure to dicrotophos foliar residues. For example, it is well recognized that 

animals do not utilize a diet comprised fully of short grass; therefore further refinements in 

the risk assessment can be performed, which in combination with a more accurate foliar halflife would yield RQs that are significantly lower. This is illustrated in Appendix A using 

species that are known to be associated with agricultural landscapes where cotton is grown. 

In conclusion, T-REX (v.1.5.2) is highly conservative and overestimates direct dietary exposure 

of terrestrial species. Although T-REX (v.1.5.2) estimates risk for birds and mammals of various 

sizes, each feed item category is not necessarily relevant to every size class. Furthermore, TREX does not account for differences in gross energy and assimilation efficiencies of the dietary 

items of birds and mammals. Therefore, appropriate allometric field metabolic rate (FMR) 

considerations, more realistic diets for bird species that frequent cotton landscapes, and 

appropriate chronic averaging for exposure modeling should be considered in refined modeling 

along with a weight-of-evidence evaluation to develop a refined risk characterization. Many of 

these refinements and recommendations can also be found in the peer reviewed literature (e.g. 

Brain et al. 2014). 

3.3.3 STIR 

The Screening Tool for Inhalation Risk (STIR v.l.O) was used by EPA (2014) to estimate the 

risk to birds and mammals from inhalation of dicrotophos. It was determined that inhalation of 

Page 16 of 56 
dicrotophos poses a potential risk to birds and mammals on an acute exposure basis. However, 

EPA (2014) used an unbounded LC50 (>0.059 mg/L, MRID 46411001) for inhalation of 

dicrotophos by rats in STIR. The use of an unbounded effects metric is entirely inappropriate and 

it is unclear if any effects were observed at the highest test concentration. The true LC50 may be 

orders of magnitude higher than that used by EPA (20 14) in STIR. Additionally, EPA (20 14) 

clearly states that dicrotophos is non-volatile (vapor pressure of 7.0 x10·5 torr and Henry's law 

constant of3 .13 x 10·11 atm-m3 /mol). Therefore, acute risk to birds from inhalation of dicrotophos 

is highly uncertain and likely much lower than that modeled by EPA (20 14 ). 

3.3.4 jiJJ> 

The Screening Imbibition Program (SIP) was used in the assessment as a screen for bird and 

mammal consumption of drinking water that may contain dicrotophos. The results of the SIP 

analysis suggested that dicrotophos exposure in drinking water is a potential concern for both 

birds and mammals. The SIP model employs the following assumptions to derive upper bound 

exposure estimates (EPA, 2010): 

1. The chemical concentration in drinking water is at the solubility limit in water (at 25°C). 

2. The assessed animals obtain 100% of their daily water needs through drinking water. 

3. The daily water need is equivalent to the daily water flux rate as calculated by Nagy and 

Peterson (1988). 

4. The body weight of the assessed bird is equivalent to the smallest generic bird modeled in 

T-REX (i.e., 20 g). This assumption results in the highest ratio of exposure to toxicity for 

the 3 assessed avian body weights ofT-REX (i.e., 20, 100, 1000 g). 

5. The body weight of the assessed mammal is equivalent to the largest generic mammal 

modeled in T -REX (i.e., 1000 g). This results in the highest ratio of exposure to toxicity for 

the 3 assessed mammalian body weights ofT-REX (i.e., 15, 35, 1000 g). 

The assumptions made in the model (1 to 5) are overly conservative and unrealistic. It is highly 

unlikely that drinking water found on a treated field would ever contain a pesticide at its 

solubility limit. For dicrotophos the water solubility used by the Agency was 11,990 mg/L 

[MRID 43603202]. However, this does not take into account the application rate applied (which 

would limit the mass of dicrotophos on the field), dissipation kinetics on the field, and the 

unlikely scenario that applicators would apply dicrotophos just prior to or during a rain event that 

would result in standing water on the field. Further, utilizing the solubility limit for a chemical 

that is highly water soluble is inappropriate as the concentration in the field begins to rival the 

chemical application of a unit area. In addition, birds satisfy some of their water needs by 

oxidative food metabolism and excrete nitrogen as uric acid instead of urea (unlike 

mammals)(EPA, 1993). Lastly, both birds (20 g) and mammals (1000 g) in the weight classes 

evaluated in SIP are highly mobile and are unlikely to get all of the daily drinking water needs 

from one treated field. It is more likely their pesticide intake would be the result of spatial 

averaging from potentially many fields (treated and non-treated) and untreated off field habitats. 

Page 17 of 56 
Therefore, SIP is designed to very significantly overestimate the contribution of drinking water 

to the overall total daily intake of a pesticide for birds or mammals. 

A more reasonable and appropriate approach to deriving conservative drinking water estimates is 

the Pesticide Root Zone Model (PRZM) edge of field predictions at the field edge. These 

estimates are generated by PRZM for use in the Exposure Analysis Modeling System (EXAMs) 

model to estimate water concentrations in the EPA standard pond scenarios. The edge-of-field 

flux estimates provide consideration of the environmental fate properties of a pesticide to predict 

transport and transformation through crop root and unsaturated soil zones. As such they provide 

more reasonable estimates of drinking water as a source of exposure. 

3.4 Supporting Documentation 

3.4.1 Refined Deterministic Assessment 

The Agency's use ofT-REX to conduct mammal and bird screening-level risk assessments 

resulted in an overly conservative risk estimate for these taxa, and indirectly for terrestrial phase 

amphibians and reptiles where birds were used as a surrogate. To demonstrate how more realistic 

assumptions can affect the risk characterization for these taxa, a refined deterministic assessment 

was conducted for birds and mammals that are known to be present in cotton agricultural 

landscapes that include cotton. This refined deterministic analysis was also conducted using an 

FMR approach rather than the FIR approach used in T-REX. Lastly, the refined analysis was run 

with both a 35 day (default) foliar degradation DT50 and a 3 day foliar DT50. The Agency 

performed the same analysis in their dicrotophos ERA (EPA, 2014) although there is clear 

evidence that suggest a 3 day DT50 is more appropriate that the 35 day default value. 

The bird species selected for this analysis include the Indigo bunting (Passerina cyanea), 

Northern cardinal (Cardinalis cardinalis), and American wigeon (Anas Americana). All three 

species are known to be associated with cotton landscapes (Sheeley et al. 1988) and represent 

different body weights and diets. For mammals, the meadow vole (Microtus pennsylvanicus) and 

white-tailed deer (Odocoileus virginianus) were selected both of which are commonly found in 

agricultural landscapes. Details on diets, body weights and other parameters selected are 

provided in Appendix A. 

The conservative, refined deterministic total daily intake (TDI) modeling was carried out to 

estimate acute dicrotophos exposure from use on cotton. The form of a standard TDI model is 

(EPA, 1993): 

k 

TDI = PT *I NFIRi * ci Equation 1 

i=l 

Page 18 of 56 
where, 

PT is the proportion of time in treated fields (unitless) 

NFIRi is the normalized food intake rate (kg food/kg bw/day) 

C is the concentration of dicrotophos in each dietary item (i) (mg/kg) 

Pi is the assumed daily proportion of the i th dietary item by mass 

k is the number of food items in the diet (unitless) 

Measured FIR are typically not available for most wildlife receptors, primarily due to the 

difficulties in measuring intake for free-ranging animals (EPA, 1993). Measured food intake 

rates determined using captive animals should not be used because such animals do not expend 

energy foraging for food and water, avoiding predators, defending territories, etc. (EPA, 1993). 

Thus, food intake rates estimated for captive animals considerably underestimate expected food 

intake rates for free-ranging animals. There are also issues with establishing accurate preconsumption dry and wet weight or volume measurements from stomach content analyses. 

Instead, for most receptors an allometric equation developed from measurements of FMR in freeranging animals best estimates food intake rates. The normalized food intake rate (NFIRi) of the 

lh food item is derived from the normalized FMR using the following equation: 

FEi * NFMR 

NF/Ri = ME· L 

where, 

NFMR is the free metabolic rate normalized to body weight (kcal/kg bw/day) 

MEi (= AEi x GEi) is metabolizable free energy for the k

1

h food item (kcal/kg) 

AEi is the assimilation efficiency of the lh food item (unitless) 

GEi is the gross energy of the lh food item (kcal/kg). 

Equation 2 

The proportion of free energy (FEi) from each dietary item is calculated using Equation 3: 

Equation 3 

The receptor specific parameters used in the exposure modeling are presented in Appendix A. 

Concentrations in feed items were estimated using the generic residue unit doses (RUDs) as 

presented in T-REX vl.5.2. Degradation on feed items was modeled two ways, the first using the 

EPA default 35 day DT50 value for foliar degradation and second using a more realistic 3 day 

Page 19 of 56 
DT50 value. The peak dietary EEC values from T-REX v1.5.2 calculated based on the cotton 

exposure scenario (0.5 lb ail A I 2 applications I 14 day retreatment interval) were used in the 

calculations. 

Details calculations and results of the refined deterministic modeling are provided in Appendix 

A. Table 3-1 summarizes these results and compares the refined modeling results with the TREX v1.5.2 results as indicated in the EPA ERA (EPA, 2014). 

The effects metrics chosen to develop the RQs are from a study by Grue and Shipley (1984). 

Grue and Shipley (1984) examined the sensitivity of European starlings (Sturnus vulgaris) to 

dicrotophos using an oral dose in administered in com oil. The authors examined brain and 

plasma ChE activity and recorded body weight and mortalities for each of the treatment levels. 

The authors determined the 24 hour median LD50 as 8.37 mglkg bw for starling males and 8.47 

mglkg bw for starling females. These LD50's were used in the risk assessment including the 

American wigeon evaluation as the domestic goose study is not considered an acceptable study 

for risk assessment purposes (see Section 2.2.1) 

Table 3-1 Summary of risk quotient results for birds and mammals associated with cotton 

fields 

Body weight Refined T-REX Short Grass RQ (Based 

Species Risk on Closest Bird Body Weight (g) Quotient!' Category ;a 

35 day DTSO (T-REX default) 

Indigo bunting (Passerina cyanea) 14.50 8.7 463.3 

Northern cardinal 44 1.61 463.3 ( Cardinalis cardinal is) 

American widgeon (Anas americana) 756 2.5 65.8 

Female meadow vole 33.8 5.6 9.8 (Microtus pennsylvanicus) 

Male meadow vole 33.8 4.7 9.8 (Microtus pennsylvanicus) 

Female deer 45000 2.7 5.2 ( Odocoileus virginianus) 

Male deer 45000 1.9 5.2 (Odocoileus virginianus) 

3 dayDTSO 

Indigo bunting (Passerina cyanea) 14.50 3.0 463.3 

Northern cardinal 44 0.9 463.3 (Cardinal is cardinal is) 

American widgeon (Anas americana) 756.0 1.5 65.8 

Female meadow vole 33.8 3.8 9.8 (Microtus pennsylvanicu~ 

Male meadow vole 33.8 2.8 9.8 (Microtus pennsylvanicus) 

Female deer 45000 1.6 5.2 ( Odocoileus virginianus) 

Page 20 of 56 
Table 3-1 Summary of risk quotient results for birds and mammals associated with cotton 

fields 

Body weight Refined T-REX Short Grass RQ (Based 

Species Risk on Closest Bird Body Weight (g) Quotienl Categoryt 

Male deer 45000 1.1 5.2 ( Odocoileus virginianus) 

' from EPA (2014) 

h Avian results are based on tbe use of the adult starling LD50 or 8.37 mg/kg bw (Grue and Shipley (1984)) 

As can be seen in Table 3-1 all of the refined deterministic risk quotients with the exception of 

the white-tailed deer are lower than those predicted by T-REX 1.5.2. The higher results for the 

white-tailed deer are due to the mammalian scaling factor. The larger the mammal, the scaling 

factor adjusts sensitivity to make it more sensitive. T -REX only uses a 1000 g large mammal 

weight as one of the three weight classes, so the effect of scaling factor is greater with a 45 kg 

deer than a generic 1 kg mammal. As previously mentioned, there is significant uncertainty 

surrounding the use of the scaling factors for both birds and mammals. 

The refined deterministic analysis uses conservative assumptions and the results indicate that 

exposure is overstated in the Agency's ERA (EPA, 2014 ). A refined exposure assessment yields 

RQs ranging from 3.8 to 0.9 for the focal species assessed. Information contained in this report 

indicates that these values can be further refined and are likely lower than the values herein 

presented. 

3.4.2 Incident Reports 

The ecological incident information system (EllS) evaluation outlines only five terrestrial 

incidents for dicrotophos and two aquatic incidents between 1976 and 2013 (Appendix B). A 

brief discussion of the terrestrial incidents are provided followed by the aquatic incidents. 

One of the reported terrestrial incidents was classified in the EllS as a misuse of the product, 

resulting in the loss of 44 bee hives. Therefore, this incident was not considered further. The 

remaining four incidents occurred with use on rice, watermelon, a disposal site, and an unknown 

site. The use patterns for rice and watermelon have been removed from the label for dicrotophos. 

Information on the disposal site incident is not provided, but it is not a labelled crop use (i.e. 

cotton), and because it is a disposal site, it is likely due to mis-handling or illegal use of a 

product containing dicrotophos. The final terrestrial incident did not have a clear use pattern 

associated with it. However, it was labelled as being highly probable a result of dicrotophos but 

the legality code was 'unknown'. Thus it is uncertain how dicrotophos was applied and to what 

purpose. The end result was the loss of 200 snow geese, a raptor, and a coyote. The fact that this 

incident is isolated indicates that the effect is not likely related to a labeled agricultural use 

managed under good agricultural practices. 

Page 21 of 56 
The incident reports in the EllS do not support a conclusion that there is a potential for direct 

effects from the use of dicrotophos on cotton as none of the incidents were as a result of legal use 

on cotton. EPA points out that the incident databases surveyed do not necessarily capture all 

incidents that may occur with a specific product due to the lack of incident reports, voluntary 

programs that collect the information, under reporting of non-mortality incidents and a general 

lack of resources to track incidents at the state and federal level. However, dicrotophos has been 

in use in the United States since 1956/7. Thus, over a potential period of approximately 68 years, 

the small number of reported EllS incidents and the high uncertainty and legality codes assigned 

to the incidents suggest that mis-use (not following the label) or mis-handling are the primary 

causes of dicrotophos incidents in terrestrial environments. There are several reports in the 

literature that indicate dicrotophos has been intentionally and improperly used for poisoning of 

animals that threaten livestock and agricultural crops (e.g. Flickinger et al. 1984; Mitchell et al. 

1984). In these cases bait was treated with dicrotophos at exceptionally high concentrations that 

would not be present in the environment from legal use. For example in Flickinger et al. (1984) 

rice treated for baiting purposes was analyzed and had concentrations of 210 ppm. 

Discriminating between intentional poisonings and effects due to legal product use requires a 

very thorough investigation that is typically lacking within these incident reports. 

It is well known that illnesses and potent viral infections can lead to animal deaths. Because 

there is typically no autopsy or biochemical/chemical analysis of carcasses in incident reports, 

concluding that isolated incidents are associated with pesticides simply on the basis that animals 

have been found in proximity to chemical use is not sufficient for attributing chemical use to an 

incident. 

In summary, there is no pattern in the incident reporting that would suggest that there are 

relevant detrimental ecological effects to terrestrial species associated with the legal use of 

dicrotophos on cotton. 

3.4.3 Field Studies 

There are two avian field studies available for dicrotophos, reporting results for use on cotton in 

Alabama and Arizona (Palmer et al. 1988 [MRID 40873701]; Sheeley et al. 1988 [MRID 

40917001]). Our review ofthe Alabama field study finds that a meaningful interpretation of the 

study findings cannot be accomplished because of the confounding use of multiple insecticide 

products and significant differences in the use of these chemicals amongst the different control 

and test plots. The finding of residues of dicrotophos in certain carcasses simply connotes some 

level of exposure that may or may not have been lethal. Maintenance insecticides were 

apparently not analyzed within the study scope. Although some of the maintenance insecticides 

used in the study are considered to have lower toxicity according to laboratory studies, any 

chemicals with characteristics of even moderate avian toxicity should not have been included in 

the testing. The effects of some of these moderately toxic chemicals have not been tested in the 

field. Most confounding to any study interpretation is the fact that profenphos (Curacron), 

malathion and methyl parathion, three other organophosphate insecticides, were used on the 

Page 22 of 56 
study plots. The phorphorthioate EPN was also used during the study. This compound that has 

since been cancelled has also been shown to be highly toxic to avian species, especially 

passerines (Hill 1993). For these reasons, no scientifically valid interpretation of the effect of 

dicrotophos within the field study can be made. The study findings can only be assessed in the 

context of relating the effects to a confluence of different agricultural materials. 

Appendix VIII of the study report (Hill, 1993) contains a listing of the maintenance insecticides 

and their timing of use of the individual study plots. 

Hill, E.F. (1993) "Acute and sub-acute toxicology in evaluation of pesticide hazard to avian 

wildlife" Up and Down Procedure Peer Panel Report; Appendix P-3 

http:/ /ntp.niehs.nih. gov /iccvam/ docs/ acutetox docs/udpproc/udpfinO 1 I append/appp3. pdf 

The Arizona study (Palmer et al. 1988) was conducted in a similar manner to that of the Alabama 

study. Both malathion (llb ai/A) and chlorpyrifos (0.7lb ai/A) were used on the test plots at 

signficiantly higher chemical application rates than the test substance dicrotophos (0.2 lb ai/A). 

As we concluded for the Alabama field study, no scientifically valid interpretation of potential 

dicrotophos effects can be made. However, avian effects to the different individual insecticides 

should be no worse than that observed in this study. 

3.5 Conclusions 

The current modeling line of evidence suggests that potential acute and chronic effects to birds 

due to dicrotophos use on cotton are overstated in the EPA preliminary ERA (EPA, 2014 ). The 

highly conservative nature of the screening-level ecological risk assessment conducted by the 

Agency provides a basis for a more refined assessment, which for the currently labeled use of 

dicrotophos on cotton demonstrates that the actual risk is significantly lower once other variables 

are considered in the risk assessment. A refined analysis that examined three bird species found 

in cotton landscapes, and took account actual dietary exposure is provided in this report to 

support this finding. Similarly, the incident report line of evidence provides no data to indicate 

that there is ecological risk to avian species from dicrotophos use on cotton. Instead, it suggests 

that human error through mis-use or mis-handling of dicrotophos is the potential risk factor for 

birds. Unfortunately, the available field studies using dicrotophos were conducted 

inappropriately and provide no useful information for assessing the risk of dicrotophos due to 

potential confounding effects of the other pesticides applied to the study fields during the study. 

For mammals, the preliminary refined assessment for white-tailed deer and meadow vole 

indicate that acute risks are low relative to the results of the highly conservative screening-level 

Page 23 of 56 
model (T-REX) employed by the Agency. Similarly, the EPA also significantly overstated 

chronic effects due to the use of the the use of the predicted maximum residue on short grass and 

comparing to a chronic NOEL effect metric. At a minimum an appropriate chronic EEC should 

be compared to the chronic effect metric to evaluate the potential for chronic adverse effects. 

Particularly as nearly all wildlife in agro-ecosystems tend to forage in edge habitats rather than in 

treated fields (Best et al. 1990, 1995). 

Page 24 of 56 
4.0 SPECIFIC COMMENTS 

The comments below are specific to inconsistencies, errors, or issues identified in the text of the 

EPA report. Page numbers and paragraph numbers are provided to assist the reviewer in locating 

the specific information, and recommendations are made for adjustments. The first set of specific 

comments are on the EPA memorandum (July 10, 2014). The second set of specific comments 

are on the EPA ERA itself (EPA, 2014 ). 

EPA Memorandum of July 10, 2014: (PC Code: 035201; DP Barcode 393746); Transmittal 

of the Preliminary Environmental Fate and Ecological Risk Assessment for the 

Registration of Dicrotophos (Case #145) by Andrew Shelby (Physical Scientist) and Nathan 

Miller (Biologist) Environmental Risk Branch 6. 

1. Under the section "Summary" 1st pp., EPA states, "In terms of its chronic toxicity 

profile, chronic risks exceeding established levels of concern are identified for birds, 

mammals, and aquatic invertebrates for dicrotophos use on cotton." 

AMV AC's comment: While EPA has identified possible chronic risks of concerns, they 

are based on a screening level assessment and AMV AC has herein provided a more 

refined analysis. 

2. Under the section "Basic Uncertainties" 2nd pp., EPA states, "The occurrence of 

monocrotophos, a metabolite of dicrotophos found in a cotton foliar residue study, in 

and/or plant tissue is a considerable uncertainty in the assessment. Monocrotophos is 

known to be more toxic to avian species than dicrotophos on an acute basis, and while 

residues of monocrotophos on foliage are presumed to be lesser (on a mass per volume or 

mass per unit area basis), the enhanced toxicity of this compound may effectively extend 

the time of acute risk LOC exceedances following dicrotophos application." 

AMV AC's comment: The study that we believe EPA is referring to is titled, 

"Dicrotophos and Monocrotophos in Dislodgeable Foliar Residues on Cotton Leaves" 

and is indexed under MRID 44 731002. Our interpretation of this study is that it validates 

our view that monocrotophos is only a very low level foliar metabolite that is rapidly 

degraded in the environment and therefore has a very negligible effect on any risk 

assessments. This study was composed of two field sites and at the site located in 

Washington County, Mississippi. Detectable levels of monocrotophos were only 

measured at two sampling intervals. The first finding was on the day of the 2nd 

application for which the arithmetic mean monocrotophos residue level was less than the 

limit of quantification. The second finding was 4 days after the 3rd application for which 

the arithmetic mean monocrotophos residue level was 0.0145 ppm, less than 2X the limit 

of quantitation .. Because the highest total residues occurred immediately following each 

application, the contribution of monocrotophos during these periods is negligible. Also, 

Page 25 of 56 
the labile nature of the monocrotophos residues would not support a contention that the 

enhanced activity of monocrotophos residues relative to dicrotophos residues would 

extend the time of acute risk LOC exceedances in a meaningful way, given the significant 

differences in concentration between parent and metabolite. 

3. In the title, "Table 1." EPA has labeled the table as, "Risk Resulting from Dicrotophos 

Exposure Presented by Taxon." 

AMV AC's comment: As the ecological risk assessments are envisioned to be refined 

over time, it would be clearer to indicate when a risk table was developed using 

screening-level modeling and when a refined approach is used. On this basis, we propose 

that the title be changed to, "Screening-Level Risk Resulting from Dicrotophos Exposure 

Presented by Taxon". 

The following is a response by AMV AC Chemical Corporation concerning the following EPA 

document: 

EPA's document, "Environmental fate and Ecological Risk Assessment for the Registration 

ofDicrotophos", July 10,2014: (PC Code: 035201); Andrew Shelby (Physical Scientist) and 

Nathan Miller (Biologist) Environmental Risk Branch 6. 

1. Under the section "Executive Summary" 3d pp., EPA states, "Aquatic exposure estimates 

for dicrotophos are presented for the parent compound and total toxic residues (i.e., 

parent dicrotophos plus transformation products: SD 6167, SD 11733, and SD 228001)." 

AMV AC's comment: Although the butanamide degradates SD 6167 or SD 11733 may 

pose some undetermined level of risk to certain aquatic species, these chemicals belong 

to a class of compounds that is distinct from the organophosphates. On this basis, these 

two metabolites should not be included in the aquatic risk assessment for dicrotophos. 

2. Under the section "2.61 Residues of Concern" 1st pp., EPA states, "Dicrotophos readily 

metabolizes to SD 6167 in aerobic soil". And, "Dicrotophos metabolizes to SD 11733 in 

anaerobic soil with concentrations as high as 12.7% of applied radioactivity at study 

conclusion (33 days)." 

AMV AC's comment: When discussing the metabolism or degradation of dicrotophos in 

the context of SD 6167 and SD 11733 formation, it should be clarified that these 

compounds are not organophosphates. One suggestion is to describe the metabolites as 

the oxo-butanamide SD 6167 and the hydroxy-butanamide SD 11733. 

Page 26 of 56 
3. Under the section "2.6.3 Evaluation of Multiple Active Ingredients, Mixture, and 

Formulated Products" 2nd pp., EPA states, "However as these products contain 

bifenthrin, the effects on invertebrates are expected to be enhanced." 

AMVAC's comment: The concentration ofbifenthrin in product mixes is generally low 

and its contribution to the overall toxicity to aquatic invertebrates is uncertain. Generally, 

pesticide mixtures act in an additive fashion (NAS, 2013; Rodney et al. 2013) thus there 

is little reason to believe toxicity would be enhanced beyond what would be expected by 

an additive response. 

4. Under the section "2.6.4 Measures of Exposure" 2nd pp., EPA states, "EECs for 

dicrotophos include degradates of dicrotophos in total toxic residues (TTR) approach. 

These residues include SD 6167, SD 11733, and SD228001." 

AMV AC's comment: For a screening level assessment, this approach may be 

appropriate; however, for a refined assessment, a more accurate assessment would 

consider the oxo-butanamide SD 6167 and the hydroxy-butanamide SD 11733, 

separately. For that reason, it would be appropriate to add an additional statement such 

as, "Because the oxo-butanamide SD 6167 and the hydroxy-butanamide SD 11733 are 

butanamides and not organophosphates, and should not be included in the dicrotophos 

risk assessment. 

5. In Table 1, page 4, EPA indicates that reptiles and terrestrial phase amphibians are at risk 

as birds are used as a surrogate for these organisms. 

AMVAC's comment: In the absence of toxicity data for terrestrial-phase amphibians and 

reptiles, it is standard practice to use endpoints for avian species as a surrogate (EPA, 

2008a). This extrapolation has little, if any, empirical support. That is, the extrapolation is 

made out of necessity due to a paucity of herptile toxicity data, not because of scientific 

justification. Birds and herptiles belong to different taxonomic classes, and therefore, 

have different metabolic rates, diets, respiratory and reproductive systems and ecology in 

general. Many of these factors can be addressed using a more appropriate exposure model 

(T-HERPS) that can account for the lower metabolic rates and thus lower food and 

residue ingestion experienced by a herptile in the field. 

6. Under the section "2.6.4 Measures of Exposure" 61h pp., EPA states, "Drinking water 

exposure alone was determined to be a potential pathway of concern for avian and 

mammalian species on both an acute and chronic exposure basis". 

Page 27 of 56 
AMVAC's comment: As discussed in Section 2.3.4 of this report, the SIP model is 

extremely conservative and does not consider dissipation kinetics, application rates, 

chronic exposure durations, application timing (on days without precipitation events), 

mammalian and avian mobility, and other factors that would result in a significantly more 

realistic exposure scenario. AMV AC recommends that the Agency re-evaluate the use of 

SIP even at the screening level, and conduct a more reasonable, realistic drinking water 

assessment for all pesticide products. 

7. Under the section "3.2.1.3 Monitoring Data" 1st pp., EPA states, "It appears targeted 

monitoring was occurring at the site as 14 samples resulted in 14 detections between the 

days of June 21 and August 24 from 2005 to 2008. Sample frequency varied drastically 

though sampling occurred on consecutive days in some instances including the day 

following the peak detection of 6.83 ppb. The subsequent concentration was 0.17 ppb. 

This rapid reduction in concentration indicates that peak concentrations are highly likely 

to be missed without high frequency monitoring. NA WQA reports 65 detections from 99 

samples in Mississippi indicating dicrotophos use areas are targeted among sampling 

sites. However, targeting monitoring around dicrotophos application and precipitation 

evens is not necessarily occurring and peak detections may be missed." 

AMV AC's comment: It is recognized that there is very limited background data 

concerning the cause of the peak detection in water of 6.83 ppb. As this value is 

significantly out of range of other reported values, it remains a distinct possibility that the 

finding represents some aberration as opposed to a true value. A more thorough 

assessment of the NAWQA data set is contained within AMVAC's response to EPA's 

assessment of water exposure and aggregate risk. 

8. Under the section "3.2.1.3. Monitoring Data" 2nd pp., EPA states, "However, occurrence 

of dicrotophos in groundwater may be expected since total toxic residues are mobile and 

persistent to hydrolysis and anaerobic metabolism." 

AMVAC's comment: Soil dissipation studies do not provide evidence of residues 

occurring at lower soil depths. Also, the EPA has demonstrated through PRZMJGW 

modeling that there is little exposure potential for dicrotophos within groundwater. 

9. Under the section "3.2.1.5. Environmental Degradates" 1st pp., EPA states, "The major 

degradates resulting from the environmental degradation processes are SD 228001, SD 

6167, and SD 11733 (table 3.4)." 

Page 28 of 56 
AMYAC's comment: Information concerning the identity of the compounds should be 

provided in the text. As previously stated, SD 6167 is better described as the oxobutanamide SD 6167 and SD 11733 as the hydroxy-butanamide. 

10. Under the section "3.2.1.2 Aquatic Spray Drift Exposure to Dicrotophos" 1st pp., EPA 

states, "The use of drift reduction technology (DRT) could reduce the distance necessary 

for to prevent exceedances of the LOC but DRT is not currently required on dicrotophos 

labels. Also, "The default ASAE Fine to Medium droplet size distribution was assumed." 

AMY AC's comment: AMY AC Chemical Corporation has labeling provisions that 

prescribes certain drift reduction technology (DRT) measures and would seek that the 

effect of such mitigation be incorporated into the risk assessment. For example, on this 

basis, the default ASAE Fine to Medium droplet size distribution should be modified to a 

coarser droplet size. 

11. Under the section "3 .3. Ecological Effects Characterization" 7th pp., EPA states, "The 

amount of monocrotophos that can form from dicrotophos and the rate of formation and 

decline in and/or on foliage soon after application is uncertain." 

AMY AC's comment: Information concerning the low potential for monocrotophos to be 

formed on foliage surface is evident based on the foliar residue study titled, "Dicrotophos 

and Monocrotophos in Dislodgeable Foliar Residues on Cotton Leaves" and filed under 

MRID 44 731002. The study demonstrates that residues of monocrotophos on cotton 

foliage at two distinct sites remained at very low levels over a 35 day period after 3 

applications. On this basis, the words, "in and/or on foliage" should be modified to "in 

foliage". 

12. Under section "3.3 Ecological Effects Characterization", 5th pp., EPA states "Data that 

pass the ECOTOX screen are evaluated along with the registrant-submitted data, and may 

be incorporated qualitatively or quantitatively into this endangered species 

assessment. ... " 

AMYAC's comment: EPA's Preliminary Environmental Fate and Ecological Risk 

Assessment for the Registration ofDicrotophos (Case #145), is not an Endangered 

Species Assessment, but rather an ERA to evaluate the registration of dicrotophos under 

FIFRA. 

13. Under the section "3.3.1 Aquatic Toxicity Assessment" table 3.11, EPA lists, "Acute/ 

Water flea (Daphnia magna)/Length/21-day NOAEC = 0.0017 mg ai!L LOAEC = 

0.0028 mg ai/L". 

AMY AC's comment: It is not clear whether EPA intended to list the NOEAC and 

LOEAC for reproductive effects, which are 0.0028 and 0.0044 mg ai/L, respectively. 

With respect to length measurements, the NOAEC and LOAEC are 0.00099 and 0.0017 

mg ai/L, respectively. However, the length data do not indicate any trend in effect versus 

concentration; thus we would conclude are not appropriate endpoints for consideration. 

Page 29 of 56 
Although according to the study author, under the employed conditions of statistical 

testing, the vehicle control was determined to be significantly different from the top 3 

dose levels, none of the doses demonstrated a reduction in length of more than 9%. An 

assessment of mean mass provides no further clarity concerning the length measurements 

as there were obvious problems with measurements of the control animals. It is our 

conclusion that the NOAEC and LOAEC associated with the reproduction parameters 

should be relied upon for the chronic risk assessment as there is a clear dose response on 

other parameters and the reproduction results appear to be more reliable. 

14. Under the section "3 .3 .1.2 Toxicity to Freshwater Invertebrates", "Chronic Effects" 1st 

pp, EPA states, "The NOAEC and LOAEC were determined to be 0.0017 mg ai!L and 

0.0028 mg ai/L based on reductions in mean total length" 

AMV AC's comment: Per our response in the previous comment, we propose that the 

reproduction-based NOAEC and LOAEC be utilized for risk assessment purposes. 

15. Under the section "3.3.2 Terrestrial Effects Characterization", "Chronic Effects" 7th pp, 

EPA states, "In Alabama, external and internal dicrotophos residues were detected on 

indigo buntings as high as 17 ppm and 0.51 ppm, respectively. 

AMVAC's comment: Even for the individual avian species of highest residues, the 

measured internal dose level did not exceed the laboratory-based LD5o of 3 mglkg/bw 

associated with the House sparrow (Passer domesticus), another passerine species. There 

is no data to suggest that an external dose of this magnitude would have a detrimental 

effect on avian species. This data indicates that this exposure level would not place this 

avian species at undue risk. 

Sample identification is contained within Table 7 of the report and indicates that the 

sample consisted of skin and feathers. The efficiency of transfer of residues associated 

with the feathers onto the skin is likely not high and the range of concentration associated 

with samples having measured internal residues is consistent with that view. In the 

sample in question that had external residues of 17 ppm, the concentration of residues in 

the associated carcass was only 0.09 ppm. Therefore, there is no evidence that 

dicrotophos residues having toxicological implications occur at high levels. 

16. Under the section "3.3.2 Terrestrial Effects Characterization", "Chronic Effects" 7th pp, 

EPA states, "While neither study design is sufficiently robust for quantitative use in risk 

estimation, anecdotal information contained within the study reports is useful for risk 

characterization." 

AMVAC's comment: We agree with the statement only in that the avian effects due to 

the different individual insecticides, including dicrotophos, should be no worse than that 

observed in this study. On this basis, one can conclude that the overall effects seen in 

both studies are limited. 

Page 30 of 56 
17. Under the section "3.3.2.2 Toxicity to Birds", "Acute and Sub-acute Effects", "Subacute', 2nd pp, EPA states, "Dicrotophos is classified as highly to toxic [Note 

typographical error with words "to toxic" inverted] very highly toxic to birds on a subacute dietary basis." 

AMV AC's comment: Although we do not dispute the EPA's classification on the basis 

of the laboratory studies, the extent of exposure as evident in the two field studies even in 

view of the complications previously discussed, demonstrate that the chemical is not 

highly toxic in the field where there were only limited mortalities noted. 

18. Under the section 4.1.1.1. "Fish and Invertebrates", "Aquatic Invertebrates", 3d pp, EPA 

states, "the chronic LOC (1.0) is exceeded for freshwater and estuarine/marine 

invertebrates for all PRZM scenarios modeled (Table 4.4)." 

AMVAC's comment: AMVAC believes that the chronic risk to aquatic organisms is best 

assessed by considering the extensive NA WQA monitoring data set, which substantiates 

that actual exposure levels would be far lower than that determined from modeling 

efforts. Therefore, although chronic risk as calculated using baseline PRZMIEXAMS 

modeling implies that there is some risk to aquatic organisms, realistic exposures in 

surface waters associated with agricultural areas as evident by monitoring data is very 

low and would not pose a risk of concern to aquatic organisms. 

19. Under the section 4.1.2.1. "Mammals", 1st pp, EPA states, "RQs exceed the acute nonlisted LOC (0.5) by a factor of up to 23X (short grass)." 

AMVAC's comment: Context should be provided on the 23X exceedance factor as this 

maximum is as a result of an exposure scenario that is unlikely to occur in nature (i.e. a 

20 g mammal consuming exclusively short grass). This information has been further 

refined within this document. 

20. Under the section 4.1.2.1. "Mammals", 2nd pp, EPA states, "based on the proposed 

maximum application rates on cotton, there are chronic dose-based exposure concerns for 

mammals of all size classes for the short grass, tall grass, broadleaf plant, fruits/pods, 

arthropods, and [Note typographical error "and and"] with granivore sub-classes. RQs 

exceed the LOC by a factor of up to 915X (short grass)." 

AMV AC's comment: This information has been further refined within this document. 

21. Under the section 4.1.2.2. "Birds", 2nd pp, EPA states, "RQs for acute dose-based 

exposure exceed the acute non-listed species LOC (0.5) for all size classes and foraging 

groups by at least two fold and as much as 926X (small bird, short grass) (Table 4.9)." 

Page 31 of 56 
AMV AC's comment: This information has been further refined within this document. 

22. Under the section 4.1.2.2. "Birds", 3d pp, EPA states, "On a sub-acute basis. [Note 

typographical error as the period punctuation should be a comma] RQs for all size classes 

and foraging groups exceed the acute non-listed species LOC (0.5) by at least two fold 

and as much as 32X." 

AMV AC's comment: This information has been further refined within this document. 

23. Under the section 4.1.2.2. "Birds", 4th pp, EPA states, "On a chronic basis. [Note 

typographical error as the period punctuation should be a comma] RQs for all size classes 

and foraging groups exceed the chronic LOC (1.0) by at least 26X and as much as 422X 

(Table 4.11)." 

AMV AC's comment: This information has been further refined within this document. 

24. Under the section 4.2. "Incident Database Review", 1st pp, EPA states, "A review ofthe 

Ecological Incident Information System [Note typographical error- provide space 

between "Information" and "System"] (EllS) database for incidents involving 

dicrotophos was conducted on December 5, Fischer." 

25. Under the section 4.2. "Incident Database Review", 5th pp, EPA states, "Therefore, the 

weight of the evidence based on the currently available data suggests that direct effects to 

avian and mammalian species are expected from the currently registered use of 

dicrotophos." 

AMV AC's comment: EPA has cited incidents as late as 1976 and has suggested that the 

weight of the evidence forms a basis for assessing direct ecological effects from the 

current registered use. However, the current registered use differs from previous labels 

and agricultural practices in many ways. These exposure mitigation changes, some 

prescribed by EPA, have had a significant impact on reducing environmental concerns 

related to product use. Further and most importantly, there is no evidence of avian 

incidents associated with the current registered use on cotton. 

26. Under the section 4.3.1. "Exposure to Aquatic Organisms", 1st pp, EPA states, 

"Environmental fate data were conservatively represented by using the 90th percentile 

mean of metabolism half-life estimates." 

AMV AC's comment: Our understanding is that EPA did not utilize the 90th percentile 

mean of metabolism half-life estimates as stated, but instead added conservatism to the 

assessment by incorporating a 3X multiplier to the single aerobic and anaerobic 

metabolism half-lives on file and a 6X factor to the aerobic aquatic metabolism half-life. 

Page 32 of 56 
27. Under the section 4.3.1. "Exposure to Aquatic Organisms", 1st pp, EPA states, 

"However, modeling values are only two times larger than the highest reported 

monitoring value and higher monitoring values may be found with more targeted 

monitoring approaches." 

AMVAC's comment: We do not dispute the factual nature of the comment; however, 

the implications of the finding need to be more thoroughly examined. It is important to 

consider that this single value is not representative of the entire very large NA WQA 

dataset where residues are more than an order of magnitude lower for all other samples. 

A more thorough assessment of the NAWQA data set is contained within AMVAC's 

response to EPA's assessment of water exposure and aggregate risk. 

28. Under the section 4.3.1. "Exposure to Aquatic Organisms", 3d pp, EPA states, 

"Concentrations of 0.6 ppb in water trigger the Endangered Species LOC (based on 

Daphnia magna toxicity endpoint of 12.7 ppb). This concentration is achieved at 

distances up to 331 feet from the edge of the field according to AgDrift v 2.1 for aerial 

applications. 

AMVAC's comment: The spray drift assessment using AgDrift v 2.01 is accurate for 

use practices that underlie the model when it was developed. Since the time when this 

data was developed, there have been important advances in reducing drift through 

implementation of more modem, good agricultural practices. For example, changes in 

nozzle specifications have led to coarser droplets that are less prone to drift. On 

AMVAC's Bidrin labels are significant instructions to reduce drift and we believe these 

have dramatically reduced drift. Therefore, the results of AgDrift overestimate exposure 

and risk. Following is the extensive labeling instructions on our Bidrin label for reducing 

spray drift: 

"Spray Drift Requirements 

All aerial and ground application equipment must be properly maintained and calibrated 

using appropriate carriers. 

OBSERVE THE FOLLOWING PRECAUTIONS WHEN SPRAYING IN THE 

VICINITY OF AQUATIC AREAS SUCH AS BUT NOT LIMITED TO LAKES; 

RESEVOIRS; RIVERS; PERMANENT STREAMS; MARSHES OR NATURAL 

PONDS; ESTUARIES AND COMMERCIAL FISHING PONDS. 

Page 33 of 56 
Do not allow spray to drift from the application site and contact people, structures people 

occupy at any time and the associated property, parks and recreational areas, non-target 

crops, aquatic and wetland areas, woodlands, pastures, rangelands, or animals. 

Do not apply by ground equipment within 25 feet, or by air within 150 feet of lakes; 

reservoirs, rivers, permanent streams, marshes or natural ponds, estuaries, and 

commercial fish ponds. 

For aerial applications, the spray boom should be mounted on the aircraft so as to 

minimize drift caused by wingtip or rotor vortices. The minimum practical boom length 

should be used and must not exceed 75% of wing span or rotor diameter. 

Droplet Size 

Use the largest droplet size consistent with good pest control. Formation of very small 

droplets may be minimized by appropriate nozzle selection, by orientating nozzles away 

from the air stream as much as possible, and by avoiding excessive spray boom pressure. 

Spray should be released at the lowest height consistent with pest control and flight 

safety. Applications more than 10 feet above the crop canopy should be avoided. 

Wind Direction and Speed 

Make aerial or ground applications when the wind velocity favors on target product 

deposition (approximately 3 to 10 mph). Do not apply hen wind velocity exceeds 15 mph. 

A void applications when wind gusts approach 15 mph. Wind speed must be measured 

adjacent to the application site on the upwind side immediately prior to application. 

Risk of exposure to sensitive aquatic areas can be reduced by avoiding applications when 

wind direction is towards the aquatic area. 

Do not cultivate within 10 feet of an aquatic area so as to allow growth of a vegetative 

filter strip. 

Low humidity and high temperatures increase the evaporation rate of spray droplets and 

therefore the likelihood of increased spray drift to aquatic areas. A void spraying during 

conditions oflow humidity and/or high temperature. 

Temperature Inversions 

Do not make aerial or ground applications into areas of temperature inversions. 

Inversions are characterized by stable air and increasing temperatures with height above 

the ground. Mist or fog may indicate the presence of an inversion in humid areas. Where 

permissible by local regulations the applicator may detect the presence of an inversion by 

Page 34 of 56 
producing smoke and observing a smoke layer near the ground surface. In conditions of 

low humidity and high temperatures, applicators should use a coarser droplet size." 

29. Under the section 4.3.1.1. "Risks to Aquatic Animals", 2nd pp, EPA states, "the acute 

non-listed species LOC (0.5) for effects to freshwater invertebrates and acute restricted 

use LOC (0.1) for effects to estuarine/marine invertebrates are exceeded, with RQs as 

high as 1.33 and 0.22 for freshwater and estuarine species, respectively. Chronic risk 

LOCs (1.0) are also exceeded: RQs were determined to be as high as 7.2 and 3.97 for 

freshwater and estuarine invertebrates, respectively. " 

AMV AC's comment: The exposure of aquatic organisms is best reflected by the very 

large NA WQA dataset, which indicates that exposure levels in surface water should not 

be detrimental to aquatic species. The EPA's PRZM/GW modeling assessment is 

sufficient to demonstrate that exposure associated with groundwater sources would not 

pose a risk to aquatic organisms. 

30. Under the section 4.3.2. "Exposure to Terrestrial Organisms", 1st pp, EPA states, "The 

spray drift model AgDrift provides helpful bounds which define the spatial extent of risk 

concern resulting from off-field drift at currently registered dicrotophos application 

rates." 

AMV AC's comment: AMV AC proposes that the Agency's statement be further clarified 

by adding information that explains that the AgDrift model is based on a dataset that 

reflects application practices that have since been refined and are included on current 

product labels; therefore the modeling outputs likely exaggerate actual drift concerns; but 

provide a useful screening level assessment. 

31. Under the section 4.3.2.1. "Risks to Mammals", "Cotton Use Pattern", 1st pp, EPA states, 

"Acute upper bound Kenega RQs derived for mammals in the Risk Estimation section of 

this assessment indicate acute listed mammalian risk LOC (0.1) exceedances for alllOOO 

gram granivore mammals (RQ = 0.07). Based on the EEC values from T-REX and the 

LD50 from the available acute rat study, the highest RQ value for 15 gram mammals 

foraging on short grass -the most sensitive size class and forage item combination- is 

11.44. 

AMV AC's comment: This information has been further refined within this document. 

32. Under the section 4.3.2.1. "Risks to Mammals", "Cotton Use Pattern", 2nd pp, EPA 

states, "Dose-based and dietary based chronic RQs exceed the LOC (1.0) for all forager 

types. Dose-based chronic RQs range from 5.82 to 915, and the dietary based chronic 

RQs range from 6.59 to 105. The exceedances for dicrotophos are greater than 915-fold 

(dose-based) and 100-fold (dietary based) for short grass mammalian foragers. These 

exceedances are based on reduced pup survival observed in a three-generation rat 

Page 35 of 56 
reproduction study. Since terrestrial application residues exceed 2 mg ai/kg dietary item 

(i.e., the mammalian reproduction NOAEC) for at least 105 days (fruits/pods/seeds) and 

as many as 250 days (short grass) following the first application of dicrotophos, there is a 

high degree of confidence in the prediction of adverse chronic effects. 

AMY AC's comment: This information has been further refined within this document. 

As this assessment addresses reproductive issues that are indicative of population-based 

effects, it is worthier noting that the baseline risk assessment itself is derived from the 

risk to the most sensitive individual of a group of animals. The use of the NOAEC is not 

population-based as the impact of a small portion of animals is unlikely to cause a 

detrimental effect to the population as a whole. Therefore, we find that EPA's statement 

that it believes that there is a high level of confidence in their prediction of adverse 

chronic effects is overstated. A more appropriate statement would have been that based 

on the Agency's risk assessment, it finds that chronic RQs exceed the regulatory 

standards. 

33. Under the section 4.3.2.1. "Risks to Mammals", "Cotton Use Pattern", 3d pp, EPA states, 

"EECs exceed the mammalian acute non-listed species LOC (0.5) for 164 days after 

application for short grass, assuming a 35-day half-life and two applications of 0.5 lb ai/A 

applied at a 14-day interval (Figure 4.1). With the same model input parameters, EECs 

exceed the mammalian acute non-listed species LOC for 116 to 134 days following 

application for all other forage types except fruits/pods/seeds, where the mammalian 

acute non-listed species LOC is exceeded by 23 days following the first application." 

AMY AC's comment: This information has been further refined within this document. 

34. Under the section 4.3.2.1. "Risks to Mammals", "Cotton Use Pattern", 5th pp, EPA 

states, "To spatially examine the potential risk of spray drift, simulations were performed 

with the program AgDRIFT. It was determined that spray drift EECs yield acute dosebased RQs that exceed the acute listed species LOC (0.1) for short grass even at the 

model limit (997 feet from the treated field). However, spray drift is not of acute dosebased risk concern for listed granivore mammals. Ag DRIFT also indicates that spray 

drift EECs yield chronic dietary RQs that exceed the LOC (1.0) for short grass even at 

the model limit (997 feet from treated field). Even considering the least conservative 

forage class (fruits/pods). [Note typographical error as the period punctuation should be a 

comma] RQs resulting from spray drift EECs would exceed the chronic LOC at least as 

far as 650 feet from the treated field." 

AMY AC's comment: as previously stated, the spray drift assessment using AgDrift v 

2.01 is accurate for use practices that underlie the model. Since the time when this data 

Page 36 of 56 
was developed, there have been important advances in reducing drift through 

implementation of more modem, good agricultural practices. For example, changes in 

nozzle specifications have led to coarser droplets that are less prone to drift. On 

AMVAC's Bidrin labels, these practices are provided to the user and ensure that previous 

concerns relating to chemical drift have been properly mitigated. 

35. Under the section 4.3.2.2. "Risks to Birds", "Cotton Use Pattern", 2nd pp, EPA states, 

"Similar to the mammalian chronic EECs, acute avian EECs are calculated on both a 

dietary and dose basis. For the cotton use, acute dose-based upper bound Kenaga RQs 

exceed the acute non-listed species LOC (0.5) for all size classes and foraging groups. 

Sub-acute dietary and chronic dietary upper bound Kenaga RQs exceed the acute nonlisted species LOC (0.5) and chronic LOC (1.0), respectively, for all forager group types. 

Considering the magnitude of acute non-listed species LOC exceedances, as much as 

926-fold, there is a high degree of certainty that avian species will be adversely affected 

by dicrotophos applied to cotton." 

AMVAC's comment: This information has been further refined within this document. 

Also, it is not clear what the Agency means when it states that there is a high degree of 

certainty that avian species will be adversely impacted by dicrotophos. As stated earlier, 

the chronic risk assessment is more geared towards assessing the impact on individual 

birds, rather than on the species due to the use of the NOAEC as the toxicological 

endpoint. Also, we believe that the Agency is overstating its conclusion based on a 

deterministic, screening level assessment without fully examining the supporting 

evidence (incident reports and field studies) .. 

36. Under the section 4.3.2.2. "Risks to Birds", "Cotton Use Pattern", 3d pp, EPA states, 

"EECs exceed both the avian acute listed species LOC (0.1) and the avian chronic LOC 

(1.0) for 270 days and 320 days, respectively, after first application for short grass, 

assuming a 35-day half-life and two applications of0.5 lb ai/A applied at a 14-day 

interval (Figure 4.2). With the same model input parameter, EECs exceed the avian acute 

non-listed species LOC (0.5) for 140 and 160 days following application for all other 

forage types except fruits/pods/seeds, where the avian acute non-listed species LOC is no 

longer exceeded after day 48. Since terrestrial application residues exceed 0.5 mg ailkg 

dietary item (i.e., the avian reproduction NOAEC) for more than 267 days following the 

first application of dicrotophos for all forager types except consumers of fruits/nuts/seeds 

( dicrotophos residues above the NOAEC through day 180), there is a high degree of 

confidence in the prediction of adverse chronic effects. Even under the less conservative 

T-REX exposure scenario, mean Kenaga acute and chronic RQs exceed the acute listed 

species or chronic LOC for all size classes and forage types. 

AMV AC's comment: This information has been further refined within this document. 

Page 37 of 56 
Also, it is important to place into perspective the timing calculated for achieving an 

acceptable LOC as the shape and slope of the curves have a significant basis on how far 

the acceptable values extend and relatively small overages in the RQ values may occur 

well before the calculated times associated with these values. This is evident for assessing 

the effect of time on achieving an acceptable chronic LOC in EPA's Figure 4.2 Avian 

LOCs Superimposed on Residue Decline Curve. It is also important to note that the 

residue decline curves represent generic upper bound estimates that likely underestimate 

the rate of residue degradation on food items. It is also worth noting that to properly 

assess a sophisticated approach for evaluating the meaning of the time periods associated 

with RQ exceedances, it is important to consider the likely exposure periods of different 

species ofbirds. 

37. Under the section 4.3.2.2. "Risks to Birds", "Cotton Use Pattern", 4th pp, EPA states, 

"To spatially examine the potential risk of spray drift, simulations were performed with 

the spray drift modeling program AgDRIFT. It was determined that spray drift EECs 

yield acute dose-based RQs that exceed the acute listed species LOC (0.1) or short grass 

even at the model limit (997 feet from the treated fields). [Note typographical error with 

unnecessary period] and for all other forage classes at least 730 feet from the treated 

field. Spray drift EECs yield subacute dietary RQs that exceed the acute listed species 

LOC (0.1) for short grass even at the model limit (997 feet from the treated field). [Note 

typographical error with unnecessary period] and for all other forage classes at least 108 

feet from the treated field. Spray drift EECs yield chronic dietary RQs that exceed the 

LOC (1.0) for short grass even at the model limit (997 feet from the treated field). [Note 

typographical error with unnecessary period] and for all other forage classes at least 250 

feet from the treated field." 

AMV AC's comment: As previously stated, the use of AgDRIFT is appropriate for a 

screening level assessment; however, with the implementation of more modem good 

agricultural practices, appropriate labeling provisions have been developed for 

dicrotophos products that address these previous concerns relating to drift associated with 

outdated application procedures. AMVAC believes that current labeling practices relating 

to drift fully address environmental exposure issues. 

38. Under the section 4.3.2.2. "Risks to Birds", "Cotton Use Pattern", 5th pp, EPA states, 

"The STIR model output indicates that inhalation may be an exposure routes of concern 

for avian species. Considering that the available acute mammalian inhalation toxicity 

study used a supersaturated solution and recorded no mortalities, and the exposure to 

droplets in the field would be expected to be of a lesser duration (i.e., less than four 

hours). [Note typographical error with as period should be a comma] inhalation is not 

regarded as the primary route of exposure eliciting observed avian toxicological response. 

Page 38 of 56 
AMV AC's comment: AMV AC agrees with the EPA's statement that inhalation should 

not be regarded as a primary route of exposure. We also believe that in consideration of 

all of the information associated with inhalation exposure, especially the changes in 

application to minimize any fine aerosol spray droplets, that it is appropriate to 

characterize inhalation exposure as an unlikely route of exposure concern. 

39. Under the section 4.4.2. "Effects", 3d pp, EPA states, "An acceptable foliar residue 

toxicity study with honey bees (OCSPP 850.3030) would allow for determination of a 24-

h TR25 . This data would reduce uncertainties surrounding the length of time postapplication that residues of dicrotophos on foliage are toxic to honey bees." 

AMV AC's comment: AMV AC believes that although there is always some value for 

developing additional information, there is already sufficient evidence that dicrotophos 

use on cotton does not yield environmental incidents on honey bees nor is there data to 

indicate any exposure. The Bidrin label also calls for care in terms of not utilizing the 

product when bees are detected in the fields designated for treatment. Also, consideration 

of dislodgeable foliar residue data on cotton as previously described in this document 

provides evidence to support the contention that dicrotophos residues are not persistent 

on foliage. 

40. Under the section 4.4.2. "Effects", 3d pp, EPA states, "A chronic fish study with an 

estuarine/marine species exposed to dicrotophos is not available. While it is uncertain 

whether estuarine/marine species may be more sensitive to dicrotophos exposure of 

chronic duration than freshwater species, available data indicate that estuarine/marine 

species are nearly 14 fold less sensitive to dicrotophos exposure of acute duration than 

freshwater fish species exposed." 

AMVAC's comment: As EPA has determined that the acute risk to freshwater and 

estuarine/marine fish is not of concern and that the chronic risk quotients for freshwater 

fish are all less than 0.001, the development of additional chronic data for the refinement 

of risk to estuarine/marine species is not warranted. 

41. Under the section 5. "Endocrine Disrupting Screening Program", 3d pp, EPA states, 

"Dicrotophos is on List 2. List 2 represents the next set of chemicals for which EPA 

intends to issue test orders/data call-ins in the near future. 

Section 6. "Federally Threatened and Endangered (Listed) Species Concerns". 

AMVAC's comment: AMVAC recognizes the current variability in the approach and 

proposed methods for the conduct ofNational Endangered Species Assessments for 

pesticide products. In 2012, the Services and EPA asked the National Academy of 

Sciences (NAS) to address several areas of concern with regard to how pesticide risk 

Page 39 of 56 
assessments are conducted by EPA and the Services. In the 2013 report entitled 

"Assessing Risks to Endangered and Threatened Species from Pesticides" (NAS, 2013), 

NAS provided a proposed framework for conducting generic endangered species 

assessments under FIFRA with direct consideration of the ESA Section 7 requirement 

(Figure 1). In addition, the NAS panel recommended the use of refined approaches (e.g., 

probabilistic methods, population modeling) when conducting risk assessments for 

endangered species. The EPA, Services and USDA are currently evaluating the NAS 

panel report and are providing fairly regular updates on progress (e.g. Federal Family, 

2013; EPA, 2013; EPA, 2014a; EPA, 2014b). 

One comment on the Agency's description of the process relates to the use of endangered 

species LOCs (Section 6.2- 3rd pp ). The NAS report recommended strongly against the 

use ofLOCs, favoring probabilistic approaches (NAS, 2013). The Agency and Services 

initially responded with a recommendation of use of a one-in-a-million analysis as 

described in the Interim Approach. Thus, use of endangered species LOCs is unlikely in 

the process at this time. 

Recognizing the on-going uncertainty in the ESA process for pesticides, Intrinsik and 

AMV AC will monitor progress in this area and will provide appropriate input as required 

to support dicrotophos. 

42. Appendix D- Appendix D contains the STIR model pages used by EPA in the 

assessment. 

AMVAC's comment: The Agency was not consistent in the application of the Mineau 

scaling factor for dicrotophos of 1.118 for birds in this analysis, but used the default 1.15 

for birds in the T-REX analysis (Appendix C- Table C-2). It is recommended that no 

scaling factor be applied for birds and dicrotophos. 

Page 40 of 56 
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Threatened Delta Smelt (Hypomesus transpacific us) and California Tiger Salamander 

(Arnbystoma califomiense), Central California Distinct Population Segment, and the Federally 

Endangered California Tiger Salamander, Santa Barbara County and Sonoma County Distinct 

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5 Environmental Fate and Effects Division Office of Pesticide Programs Washington, D.C. 

20460 September 29, 2010. 

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exposed to dicrotophos, an organophosphorus pesticide. Pesticide Biochemistry and Physiology 

16:129-135. 

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to organophosphorous pesticides. Arch. Environ. Contam. ToxicoL 10(2):215-29. 

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Environ Toxicol Chern 13(9):1383-1391. 

Page 43 of 56 
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828 

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organophosphate pesticide. Environ. Res. 35, 454-465 

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and F. Korte (Eds.) Environmental Quality and Safety: Chemistry, Toxicology and Technology. 

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( ed). Nova Publishers NJ. 

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Consideration of Spray Drift in Pesticide Risk Assessment: Notice of Availability and Request 

for Comment 79 FR 4691. January 29, 2014 

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extrapolation of acute toxicity in birds. Regul. Toxicol. Pharm. 24: 24-29. 

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Monogr 57: 11-128. 

Nagy, K. and C. Peterson. 1988. Scaling of Water Flux Rate in Animals. University of California 

Press, Berkeley, CA. 

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and birds. Annu Rev Nutr 19: 247-277. 

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Species from Pesticides. National Academy of Sciences. The National Academic Press, 

Washington, DC. 

Page 44 of 56 
Palmer, D.A., H. Krueger, and M. Jaber. 1988. An evaluation of its effects upon wildlife on and 

around cotton fields in southwestern Arizona. MRID 40873 701 

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with Bidrin 8®. Phase 1- Field Investigation. Phase 2- Analytical. Sponsor AMVAC Chemical 

Corporation. 4100 East Washington Blvd., Los Angeles, California. 90023. 

Rodney, S.I., R.S. Teed and D.R.J. Moore. 2013. Determination of Hazardous Concentrations 

with Species Sensitivity Distributions. Version 3, April, 2013. Unpublished study performed by 

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Environment. 

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toxicity data. Bulletin of Environmental Contamination & Toxicology 62:653-663. 

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evaluation of its effects upon wildlife on and around cotton fields in southeastern Alabama. 

[MRID 40917001]. 

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125. 

Page 45 of 56 
APPENDIX A 

Refined Deterministic Total Daily Intake 

Models for Birds and Mammals that Frequent 

Cotton Fields. 

Page 46 of 56 
The bird and mammal assessment conducted by the Agency in the dicrotophos preliminary ERA 

(EPA, 2014) used T-REX as the modeling line of evidence to characterize risk. As mentioned in 

the response document, there are numerous issues with the approach that T-REX used to 

estimate total daily intake from an oral or dietary perspective. A more accurate method to 

determine risk is with the free metabolic rate (FMR) approach where the energy or the diet is 

taken into account rather than simply dietary mass. In addition, modeling with a more realistic 

estimate of the foliar degradation rate than the default 35 d value used by the EPA in T -REX. 

The analyses do not include consideration of time spent foraging in the field, and other factors 

that would significantly reduce exposure. However, the results demonstrate that risk to birds and 

mammals are overstated in the EPA preliminary risk assessment (EPA, 2014). 

Short species descriptions are provided below, followed by the calculations for the refined 

deterministic total daily intake model and results. 

Birds 

Northern cardinal 

The Northern cardinal (Cardinalis cardinalis), order Passeriformes, is 

found throughout the eastern United States and Mexico as well as in 

southern Ontario (Robbins, 1991; Rosenberg et al., 1991). Habitat is 

varied and may include forest edges, shrubby areas, hedgerows in 

agricultural fields, and grasslands (Dow, 1969; Em1en, 1972). Northern 

cardinals feed on soil surface invertebrates (29%), seeds (45%), fruits 

(24%), and some broadleafforage (2%). The mean body weight of adult 

birds is 44 g (Laskey, 1944). 

Indigo bunting 

The Indigo bunting (Passerina cyanea), order Passeriformes, is a small 

migratory song bird that breeds in eastern North America and the 

southwestern United States. The Indigo bunting is a frequently 

observed bird species in agricultural areas in the United States 

(Conover et al., 2014). During the breeding season these birds will 

forage on the ground or in trees or shrubs for small seeds (22%) and 

terrestrial arthropods (12% soil surface invertebrates; 66% foliagedwelling invertebrates). The mean body weight for adult Indigo 

buntings is 14.5 g (Dunning, 1993). 

Page 47 of 56 
American wigeon 

The American wigeon (Anas americana), order Anseriformes, is an 

abundant duck that breeds in northwestern North America. It is a 

dabbling duck, but is known to commonly leave water and graze on 

vegetation in agricultural fields. Its diet consists of small seeds ( 41% ), 

grasses ( 18% ), and broadleaf forage ( 41% ). The mean body weight for 

the American wigeon is 756 g (standard deviation of79.9 g) (Giesy and 

Solomon, 2014). 

Mammals 

Meadow vole 

The meadow vole (Microtus pennsylvanicus) is found throughout North 

America in meadows, lowland fields, grassy marshes, and along rivers 

and lakes (Reich, 1981; Zimmerman, 1965; Getz, 1985; Neuburger, 

1999). This species commonly inhabits agricultural areas including 

pastures, hay and grain fields (Johnson and Johnson, 1982; Burt and 

Grossenheider, 1980). The meadow vole is active both day and night with 

a small home range of <0.1 ha (<1000 m2

) (Boonstra and Rodd, 1983; 

Elbroch and Murie, 1963; Banfield, 1974; Neuburger, 1999). The average 

adult body weight of the meadow vole during the agricultural growing 

season is 33.8 g (based on data collected in Boonstra and Rodd (1983) 

and Brochu et al. (1998)). It feeds mainly on herbaceous matter (averaging by volume 55% dicot shoots, 

32% monocot shoots, 4.5% seeds, 1.3% roots), with some consumption of fungi (5.8%) and insects 

(1.8%) (Lindroch and Batzli, 1984). 

White-Tailed Deer 

White-tailed deer ( Odocoileus virginianus) was selected as a focal species 

because they are large, browsing ruminants (i.e., herbivores) and they are 

the most widely distributed North American mammal (CWS, 1990). 

During the growing season, white-tailed deer consume primarily monocot 

and dicot shoots and leaves, which are likely to have relatively high 

amount of pesticide residues on fields immediately following pesticide 

application. They can survive in a variety of habitats. Ideal conditions 

provide a combination of dense forest and edge environments (Dewey, 

2003). The diet of white-tailed deer varies seasonally with the availability 

of food items. This assessment focused on dietary items of the growing season. In the spring and early 

summer, deer primarily consume leaves, forbs and grasses (Short, 1986; Daigle et al., 2004). When 

present, food crops can make up an important part of the diet (Daigle et al., 2004 ). In late summer, fruits 

become a significant food source. A study performed in Quebec determined the body weights of male and 

female white-tailed deer for different age groups in three separate populations (Lesage et al., 2001). The 

Page 48 of 56 
populations were differentiated by their density and according to various climatic conditions. Body 

weights for adult male white-tailed deer (:2: 2.5 years) ranged from 53 to 116 kg adult female (:2: 2.5 years) 

body weights ranged from 39 to 52 kg. For the exposure analysis, the mean weight of females was 

estimated to be 45 kg (SARA, 2006). 

Page 49 of 56 
Example Calculations for Meadow vole 

The table below provides information on the sample calculations used to derive the total daily intake (mg 

ai/kg bw) for the Meadow vole. The same approach was applied to all of the cotton specific surrogate 

species, with the models appropriately parameterized for those species. The mass of dicrotophos 

associated with the actual meadow vole diet was calculated directly in T-REX vl.5.1 assuming a the 

following use pattern parameters (0.50 lb ai/A, 2 applications, and 14 day interval). The default 35 day 

foliar DT50. 

Parameter Equation Reference I Information 

Exposure 

= 2.514*(body weight (g))0507 Mammalian rodent equation - EPA 

Field metabolic rate (FMR) = 2.514 *(33 .8 g)0 507 1993 

(kcal/day) Body weight - Boonstra and Rodd = 14.98 (1983); Brochu eta!. (1998) 

EPA, 1993 

GE- gross energy (kcal/g) values 

0.63 kcal/g ww (leaves)" 

1.3 kcal/g ww (young grasses) 

4.6 kcal/g ww (seeds) 

0.71 kcal/g ww (roots)b 

1.6 kcal/g ww (average of grasshoppers, 

FMR crickets and beetles) 

IP=l[ (G Ej •AEj)*Pil AE - assimilation efficiency proportion 

Mass of prey consumed per day = 14.98 "'""[0.55*(0.63*0.73) + 0. 73 (green forbs- rabbits, voles, 

(g/day) 0.32*(1.3*0.73) + 0.045*(4.6*0.85) + mice)b 0.013*(0.71 *0.73) + 0.058*(0.63*0.73) + 0.85 (seeds, nuts- voles, mice) 0.018*(1.6*0.87)] 0.87 (insects- small mammals) = 18.94 

p -proportion of diet by mass 

0.55 (dicot shoots) 

0.32 (monocot shoots) 

0.045 (seeds) 

0.013 (roots) 

0.058 (fungi) 

O.Ql8 (insects) 

Mass of dicrotophos assuming a diet 

comprised of 55% dicots (tall grass), EPA, 2012 (T-REX v1.5.2) 32% monocots (short grass), 4.5% = 96.68 (tall grass) (2 applications of0.5 lb/A, using 14- seeds (fruits/ pods/ seeds), 1.3% roots = 210.94 (short grass) day application interval and 35-day (broadleafplants), 5.8% fungi = 13.18 (fruits/ pods/ seeds) foliar degradation rate) (broadleafplants), and 1.8% insects = 118.86 (broadleafplants)a 

(arthropods) = 82.62 (arthropods) ww- wet weight (upper bound T-REX residue values) 

(mglkg ww) 

= Mass of prey consumed per day ( ...L) * day 

l:P [Mass of dicrotophosi ( ~) * Pi] * kgww 

0.001~ g 

Mass of dicrotophos in daily diet = 18.94 g/day*(0.55*118.86 mg/kg ww + 

(mg/day) 0.32*210.9 mg/kg ww + 0.045*13.18 

mg/kg ww+ 0.013*118.86 mg/kg ww+ 

0.058*118.86 mg/kg ww + 0.018*82.62 

mg/kg ww)*0.001 kg/g 

=2.7 

Daily dose for meadow vole = 3.2 mg/kg bw/day-<-- 0.0338 kg 

(mg/kg bw/day) =80.3 

Page 50 of 56 
Parameter Equation Reference I Information 

Exposure 

Effects 

Rat LD50 for dicrotophos (acute) 8 (female) Acute mammal single dose oral LD50 

selected by EPA (Ace. Nos. 261098 & (mg/kg bw) 11 (male) 43893901) 

Female: 

= 8*(350 g +- 33.8 g) 0

•

25 

Rat LD50 scaled to meadow vole body = 14.35 

EPA, 2012 (T-REX v1.5.2) weight (acute) (mg/kg bw) Male: 

= 11 *(350 g +- 33.8 g) 0

•

25 

= 19.73 

' The gross energy of dtcot leaves was used as a surrogate for fungt m the absence of avatlable data for thts feed ttem. 

b The gross energy for roots was calculated using the percent moisture for leaves. 

' Fungi and roots were assumed to have the same AE distribution and residue values as monocot and dicot leaves because no data were available 

for these items. 

Acute 

The RQs for acute exposure of the meadow vole to dicrotophos are: 

RQ(jemales) = 

mg 80.3 kjibw 

mg 14.35 kg bw 

5.6 

mg 80.3 kg bw 

RQ(males) = mg = 4.1 

19.7 kg bw 

Page 51 of 56 
Table A-1 Avian Total Daily Intake Modeling Results 

T-REXShort 

Field metabolic Massofprey Mass of GrassRQ 

Species Body rate(FMR) consumed dicrotoplzos in Daily dose BirdLD50 Risk (Based on 

weight(g) (kcal/day) per day daily diet (mg!kg bw/day) (mg!kgbw) Quotient Closest Bird 

(glday) (mg/day) Body Weight 

Cate}?ory) 

Using a 35-d half-life 

Indigo bunting 

(Passerina 14.50 15.73 9.21 0.62 42.8 4.92/8.37' 8.7/5.1b 463.3 

cyanea) 

Northern cardinal 

( Cardinalis 44 36.13 16.69 0.59 13.4 4.92/8.37' 2.73/1.61b 463.3 

cardinal is) 

American 

wigeon 756 304.06 174.73 16.09 21.3 8.37 2.5 65.8 (Anas 

americana) 

Usina a 3-d half-life 

Indigo bunting 

(Passerina 14.50 15.73 9.21 0.37 25.3 4.92/8.37' 5.1/30b 463.3 

cyanea) 

Northern cardinal 

(Cardinalis 44 36.13 16.69 0.35 7.9 4.92/8.37' 1.6/09b 463.3 

cardinalis) 

American 

wigeon (Anas 756.0 304.06 174.73 9.51 12.6 8.37 1.5 65.8 

americana) 

- Grue and Shipley (1986) reported LDSO values for nestlmgs and adult males for the European starling (Stumus vulgarus). The nestling LDSO was 4.92 mg a~_/kg bw and the adult male LDSO was 8.37 

mgai/kgbw. 

b-Risk quotients for nestlings (higher number) and adults based on differing LDSO values for European starlings. 

Page 52 of 56 
TableA-2 Mammalian Total Daily Intake Model Results 

T-REXShort 

Field Massofprey Mass of LD50scaled GrassRQ 

Body metabolic rate consumed dicrotophos in Daily dose to surrogate Risk (Based on 

Species weight (FMR) per day daily diet (mglkg bw/day) species body Quotient Closest 

(g) (kcal/day) (g!day) (mglday) weight (mglkg Mammal Body 

bw)) Weight 

Category) 

Using a 35-d lzalBife 

Female meadow vole 

(Microtus 33.8 15.0 22.0 3.2 93.4 14.4 5.6 9.8 

pennsylvanicus) 

Male meadow vole 

(Microtus 33.8 15.0 22.0 3.2 93.4 19.7 4.1 9.8 

pennsylvanicus) 

Female deer 

( Odocoileus 45000 3427 7229 954 21.2 2.4 8.9 5.2 

virginianus) 

Male deer 

( Odocoileus 45000 3427 7229 954 21.2 3.3 6.5 5.2 

virginianus) 

Usinf! a 3-d half-life 

Female meadow vole 

(Microtus 33.8 15.0 22.0 1.9 55.2 14.4 3.8 9.8 

pennsylvanicus) 

Male meadow vole 

(Microtus 33.8 15.0 22.0 1.9 55.2 19.7 2.8 9.8 

pennsylvanicus) 

Female deer 

( Odocoi/eus 45000 3427 7229 564 12.5 2.4 5.3 5.2 

virginianus) 

Male deer 

( Odocoileus 45000 3427 7229 564 12.5 3.3 3.8 5.2 

virginianus) 

Page 53 of 56 
APPENDIX B EllS Incident Reports for 

Dicrotophos 

Page 54 of 56 
EHS Pesticide Sununary Report: General Infonnation 

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Page 56 of 56 
Appendix 4 
TITLE: 

Response to the Data Evaluation Record on the Fish Early Life Stage Toxicity of Dicrotophos 

Technical to Fathead Minnow (Pimephales prome/as), EPA MRID Number 48482901 

Author: 

ABC Labs 

Sponsor: 

AMVAC Chemical Corporation 

4695 MacArthur Court, Suite 1200 

Newport Beach, CA 92026 

Date: 

November 6, 2014 

P1 
NO ClAIM OF CONFIDENTIALITY 

No claim of confidentiality, on any basis whatsoever, is made for any information contained in 

this document. I acknowledge that information not designated as within the scope of FIFRA 

sec. lO(d)(l)(A),(B}, or (C) on which pertains to a registered or previously registered pesticide is 

not entitled to confidential treatment and may be released to the public, subject to the 

provisions regarding disclosure to multinational entities under FIFRA lO(g}. 

Submitter: Date: 

Typed name of signer: Jon C. Wood 

Director of Registrations 

Typed name of company: AMVAC Chemical Corporation 

P2 
STATEMENT OF GLP COMPLIANCE 

This technical document provides information that assesses the benefits of use of dicrotophos. 

The document does not contain any new or original data. Therefore, the requirements of 40 

CFR Part 160 are not appropriate to this document. 

Submitter/Sponsor: Date: 

Typed name of signer: Jon C. Wood 

Director of Registrations 

Typed name of company: AMVAC Chemical Corporation 

P3 
better insight 

better outcomes 

www.abclabs.com 

November 6, 2014 

RE: Response to the Data Evaluation Record on the Fish Early Life Stage Toxicity of 

Dicrotophos Technical to Fathead Minnow (Pimephales promelas),' EPA J\1RID 

Number 48482901 · 

INTRODUCTION: 

The document titled 'Data Evaluation Record on the Fish Early Life Stage Toxicity of 

Dicrotophos Technical to Fathead Minnow (Pimephales promelas),' EPA l\.1RJD Number 

48482901, has been reviewed by ABC Laboratories. The study deficiencies and 

conclusion stated in this document are discussed below. Based on its review ofthe EPA 

DER, and EPA's rationale for classifying the study "supplemental," ABC Laboratories is 

providing responses to the issues raised in EPA's review of this study, and believes the 

study should be upgraded to "core." 

STIJDY DEFICIENCIES CITED BY EPA: 

The EPA review cited two study deficiencies in deciding to classify the dicrotophos early 

life stage study "supplemental" rather than core. These deficiencies include: 

1. The redistribution of larvae in the control on day seven violated the assumption of 

independence of replicates. 

On study day 7 (i.e., day 2 post-hatch), all live larvae were counted and released into their 

respe<O-tive replicate growth chamber; however,- larvae from two control replicates were 

inadvertently added to the same replicate growth chamber. The biological observations 

had already been recorded for both replicates prior to the inadvertent pooling of larvae. 

Redistribution was elected by the study authors for these two replicates of the control, 

with larvae divided according to the initial number recorded for each replicate. The 

redistribution of larvae in control replicates is a violation of independence of replicates 

and therefore calls the statistical conclusions and the integrity of the study husbandry into 

question; however, because none of the endpoints were significantly affected that would 

skew the results, the reviewer determined the redistribution did not impact the integrity of 

the study. 

2. Dry weights (24 hours at 60°C) are preferable to wet weights (blotted dry). If the fish 

exposed to the test material appear to be edematous compared to control fish, 

Page 1 of4 

4780 Discovery Drive • Columbia, Missouri 65201 80~~.5227 7200 E. ABC Lane • Columbia, Missouri 65202 

~ : 
determination of dry rather than wet weight is recommended. Since edema was 

observed in treated fish, wet weight measurements in this study are not reliable. 

These deficiencies impact the acceptability of the study. 

EPA's Conclusions: 

The redistribution of fry in control replicates is a violation of independence of 

replicates and, in conjunction with the weight measurement methods (i.e., wet weights in 

lieu of dry weights), calls the integrity of the study conduct into question; however, this 

study provides information useful for risk characterization and is classified as 

SUPPLEMENTAL. No treatment-related effects on egg hatchability, time to start or 

complete hatch, larval survival, or growth were observed during exposure to dicrotophos 

technical at up to 9.88 mg ai/L, the highest mean measured concentration tested. In 

addition, there were no treatment-related clinical signs of toxicity at any exposure leveL 

ABC LABORATORIES RESPONSE: 

Below are ABC Laboratories responses to the study deficiencies cited by EPA and EPA's 

conclusions for ABC Laboratories Inc. Study No. 66150 titled, 'Dicrotophos Technical: 

Early Life-Stage Toxicity Test with the Fathead Minnow, Pimephales promelas, Under 

Flow-Through Test Conditions.' 

Cited Study Deficiencies: 

1. The redistribution of larvae in the control on day seven violated the assumption of 

independence of replicates. 

ABC Laboratories Response: ABC Laboratories agrees that the redistribution of larvae 

on study day 7 did not impact the integrity of the study because none of the endpoints 

were significantly affected that would skew the results. The redistribution was the result 

of a technical oversight at the time hatched fry were released from the egg incubation 

cups. At the time this event occurred, study day 7 (i.e., day 2 post-hatch), all live fry 

were counted and released into their respective replicate growth chamber; however, fry 

from control replicate D were inadvertently added to control replicate C test chamber 

which already contained the fry released into its own respective chamber. The biological 

observations had already been recorded for both of these replicates prior to the 

inadvertent pooling of fry. All fry present in control replicate C, after inadvertent 

pooling, were removed and divided according to the initial number recorded for each 

replicate, with the appropriate number placed in control replicates C & D. After fry were 

separated, the biological observations were performed again for these replicates. Since 

this inadvertent error occurred only with two of the control replicates, redistribution was 

the best alternative for continuing the exposure as well as minimizing the number of 

vertebrates sacrificed forthe study. 

Page 2 of4 

P5 

I I 
It is important to recall the overall design of the diluter and exposure chamber testing 

apparatus. Flows of control dilution water (and test solutions) are first split to the A and 

B replicates and the C and D replicates. The dilution water ot test solution flows to the A 

and B replicates, and the C and D replicates, are subsequently split again, for separate 

flows to each replicate. Therefore, the dilution water and test solution flows to the A and 

B replicates, and the C and D replicates using this test apparatus set-up are more closely 

linked than flows to the A and C replicates, or the B and D replicates. Measurements of 

dilution water flows to these control replicates were within 10% of the mean flow rates, 

and there were no differences between the C and D replicates in terms of key 

environmental factors, such as dissolved oxygen, temperature, or pH, which, if different, 

may have affected fry survival and growth. However, there were no differences between 

the C and D replicates during the study for these key environmental factors. 

ABC Laboratories also notes that this technical error involved only control fish, so there 

was no potential for slightly different exposures to the test material, as might occur in 

replicates from a treatment group. As noted above, there were no differences during the 

study, either before or after day 7, between the control replicates in terms of key 

environmental parameters that could impact fry growth or survival. 

Another key consideration is tha~ this inadvertent mixing of fry from the control C and D 

replicates occurred very early in the study, at the tii:ne the fry were released from the egg 

incubation cups. The key endpoint evaluated at this stage of the study is hatching 

success. There were no significant differences in hatching success between the C and D 

replicates. Effects on the typically more sensitive test endpoints of growth (fry weight 

and length) and overall fry survival were not evaluated until several weeks later, at study 

termination. 

There were also no immediate, or short-term effects on fry survival in either the CorD 

control replicate. On the contrary, observations of the fry in these two replicates 

remained consistent throughout the remainder of the exposure period. 

One of the criteria listed in the DER (Table 1) is that each treatment should include a 

minimum of 20 embryos per replicate cup and a minimum of 30 fish per treatment for 

post-hatch exposure. This criterion would still be met if the two control replicates 

associated with the redistribution of larvae were excluded from the statistical analyses. 

Additionally, the OPPTS 850.1400 test guideline only requires at least two replicates; 

however, studies of this nature conducted at ABC Laboratories routinely utilize four 

replicates per treatment, which increases the statistical power to detect differences 

between the treatment groups and the controls. The fry survival and growth (length and 

weight) data were statistically evaluated against the two control replicates (replicates A & 

B) not associated with the redistribution of larvae. This evaluation con:finned that there 

were no differences between the two sets of control replicates (replicates A and B and 

replicates C and D), and more importantly, confirmed that the NOEC remained 

unchanged for all test parameters. 

Page 3 of4 

P6 
2. Dry weights (24 hours at 60°C) are preferable to wet weights (blotted dry). If the 

fish exposed to the test material appear to be edematous compared to control fish, 

determination of dry rather than wet weight is recommended. Since edema was 

observed in treated fish, wet weight measurements in this study are not reliable. 

ABC Laboratories Response: The fish appearing to be edematous were observed early 

in the study on study days 3, 4, and 5. One edometous fish was observed in the 

0.327 mg/L test group on study day 3. On study day 4 there were two edometous fish in 

the control (replicate C), three edometous fish in the 0.327 mg/L (one in replicate C and 

two in replicate D) test group, and one edometous fish in the 1.21 mg/L (replicate A) test 

group. On study day 5 there was one edometous fish in replicate C of the 1.21 mg!L test 

group. The daily clinical observations beginning with study day 5 (day 0 post-hatch; start 

of the 28-day post-hatch exposure) are presented in the attached appendix. As shown in 

this appendix, all fish surviving at test termination were normal in appearance; therefore, 

blotted wet weight measurements were appropriate at test termination. 

The fish were exposed for four weeks after the last observation of an edometous fish. 

Any fish that were observed as edometous before the 28-day post-hatch period, or on day 

0 of the post-hatch period, either were early mortalities (by day 1 post-hatch) or were 

fully normal in appearance by day 1 post-hatch and throughout the remainder of the posthatch exposure period. If the edometous fish were the mortalities before or at the 

beginning of the post-hatch phase of the study, they clearly had no impact on the fish 

weights recorded at test termination. If the fish reported as edometous on or before day 0 

of the post-hatch period survived until termination, they were normal in appearance 

through the remainder of the study, and therefore edema was clearly not a factor when the 

fish were weighed at test termination. 

Conclusion: 

Based on these cited deficiencies, the study reviewer classified the study as 

SUPPLEMENTAL. However, as described above, the inadvertent mingling of fish from 

two closely linked control replicates early in the study did not result in any trend or effect 

on sensitive test endpoints determined at study termination. The EPA reviewer 

determined that this inadvertent mingling of fish from two control replicates early in the 

study did not impact study integrity. The few edometous fish observed on or before day 

0 of the post-hatch period were not observed at any later time points, and specifically, no 

edometous fish were observed at test termination, so no edematous fish affected the body 

weight measurements taken at test termination. Therefore, ABC Laboratories, based on 

the information provided, believe that the study classification should be upgraded to a 

CORE classification. 

Prepared By: ~JU..... c/. ~~~ Stephen L. Hicks 

Senior Scientist/Study Director 

ABC Laboratories, Inc. 

Page4 of4 

P7 

Dme: ___ O_~~'_AJ._v_· ~v.~;rf----

I 

I 
. . :. ·. .- . ··--

Appendix 

Table 1. Hatched Fry Cumulative Mortality and Clinical Observations 

During the 28-Day Post-Hatch Period of Fathead Minnows 

Exposed to Dicrotophos Technical (ABC Study No. 66150) 

Page 1 of9 

P8 
Table 1. Hatched Fry Cumulative Mortality and Clinical Observations During the 28-Day Post-Hatch Period of Fathead 

Minnows Exposed to Dicrotophos Technical (ABC Study No. 66150) 

Mean Measured Number Da 0 2 Da 1 Da 2 Day3 

Concentration Larvae No. Effects 4 No. Effects 4 No. Effects 4 No. Effects 4 

(mg a.i.IL) Rep. Hatched 1 Dead 3 Dead 3 Dead 3 Dead 3 

Control A 19 0 18 AN 0 19AN 0 17 AN,2B 0 17 AN,2NF 

B 20 0 20AN 0 20AN 0 20AN 0 20AN 

c 19 0 17 AN 2 17 AN 2 14AN; 3 B 2 14AN; 2B; 1 NF 

D 17 0 16AN; 1 B 0 16AN;1B 0 16 AN; 1 B 0 15 AN; 1 B; I NF 

0.327 A 20 0 20AN 0 20AN 0 19 AN; 1 B 0 19 AN; I NF 

B 20 0 19AN 0 20AN 1 19AN 1 19AN 

c 20 1 19AN I 19AN 1 19 AN 1 19AN 

D 18 2 16AN 2 16AN 2 16AN 2 15 AN; 1 NF 

0.590 A 20 0 19AN 1 19AN 1 19AN 2 18 AN 

B 16 0 15 AN; 1 NF 0 16AN 1 15 AN 1 15AN 

c 16 I 14AN 4 12AN 4 12AN 4 12AN 

D 20 0 20AN 0 20AN 0 20AN 0 20AN 

""0 1.21 A 20 1 18 AN 2 17 AN 2 18AN 2 18 AN w B 20 0 19 AN; 1 B 1 19AN I 19AN 1 19 AN 

c 20 0 18 AN; 1 ED; 1 B 1 19AN 2 18AN 2 18AN 

D 19 0 .19AN 0 19AN 0 19 AN 0 19AN 

2.45 A 20 0 20AN 0 20AN 0 20AN 0 20AN 

B 20 0 19AN 0 19AN 0 20AN 0 20AN 

c 20 0 20AN 0 20AN 1 19AN 1 19AN 

D 19 0 19AN 0 19AN 0 19 AN 0 19 AN 

4.94 A 19 0 18AN;1NF 0 18 AN; 1 1 18AN 2 16 AN; 1 NF 

NF 

B 20 0 19AN; 1 B 0 19 AN; 1 B 0 18 AN; 2B 1 19AN 

c 19. 1 17 AN; 1 B 2 17 AN 2 17 AN 2 17 AN 

D 18 0 18AN 0 18 AN 0 18 AN 0 18 AN 

9.88 A !9 0 19AN 1 18AN 1 18 AN 3 16AN 

B 18 0 18AN 0 18 AN 0 18 AN 0 18 AN 

c 20 0 20AN 0 20AN 0 19 AN; 1 B 1 19AN 

D 20 0 18AN;2B 1 19AN 1 18 AN; 1B 1 18 AN; 1NF 1 Cumulative number of hatched larvae during the study. Some larvae had not yet hatched by day 0 post-hatch; therefore, the fry not accounted for on post-hatch observation days were not 

yet hatched. 2 Day 0 post-hatch= Day 5 of test. 3 Cumulative number of dead fish. 4 Effects: AN= appear normal; B =on bottom; ED= edema; NF =not found. 

~Page 2 of9-

.ABC Study No. 66150 
Table 1. Hatched Fry Cumulative Mortality and Clinical Observations During the 28-Day Post-Hatch Period of Fathead 

Minnows Exposed to Dicrotophos Technical (ABC Study No. 66150) (continued) 

Mean Measured Number Da 4 Da 5 Da 6 Day7 

Concentration Larvae No. Effects 2 No. Effects 2 No. Effects 2 No. Effects 2 

(mg a.i.IL) Rep. Hatched Dead 1 Dead 1 Dead 1 Dead 1 

Control A 19 0 18AN,1NF 0 18 AN, 1 NF 0 17 AN, 2NF 0 17AN,2NF 

B 20 1 19AN 3 17 AN 3 17 AN 3 17 AN 

c 19 3 13 AN; 1 B; 2 NF 3 14AN; 1 B; 1 NF 4 13 AN; 1 B; 1 NF 4 13 AN; 2NF 

D 17 2 15 AN 3 14AN 3 14AN 3 14AN 

0.327 A 20 1 19 AN 2 18 AN 2 18AN 2 18 AN 

B 20 2 18 AN 2 18AN 2 18AN 2 18 AN 

c 20 2 18AN 2 18AN 2 18 AN 2 18 AN 

D 18 2 16 AN 2 16AN 3 15 AN 3 15 AN 

0.590 A 20 2 l8AN 2 18AN 2 18 AN 2 18AN 

B 16 1 14AN; 1 NF 1 14AN; 1 NF 1 14AN; 1 NF 1 14AN;1NF 

c 16 4 12AN 4 12AN 4 12AN 4 12AN 

-a D 20 0 20AN 0 20AN 0 20AN 0 20AN ....... 

0 1.21 A 20 2 17AN;1B 3 17 AN 3 17 AN 3 17 AN 

B 20 2 18 AN 2 18AN 2 18 AN 2 18AN 

c 20 3 17 AN 4 16AN 4 16AN 4 16AN 

D 19 0 19AN 0 19AN 0 19 AN 0 19 AN 

2.45 A 20 0 20AN 0 20AN 0 20AN 0 20AN 

B 20 0 20AN 0 20AN 0 20AN 0 20AN 

c 20 1 18AN;1NF 1 19AN 1 19AN 1 19AN 

D 19 0 19AN 0 19 AN 0 19 AN 0 19 AN 

4.94 A 19 2 16 AN; 1 NF 2 16AN;1NF 2 16 AN; 1 NF 2 16AN; I NF 

B 20 1 18AN; 1 NF 1 17AN;1B;1NF 1 17AN;2NF 1 18 AN; 1 NF 

c 19 2 17 AN 2 17 AN 2 17 AN 2 17 AN 

D 18 0 17AN;1NF 0 18AN 0 18AN 0 18 AN 

9.88 A 19 3 16AN 3 16AN 3 16AN 3 16AN 

B 18 0 18 AN 0 17AN;1NF 0 17AN;1NF 0 17AN;1NF 

c 20 1 19AN 1 19AN 2 18 AN 2 18AN 

D 20 1 19AN 1 19AN 2 18 AN 2 18 AN 

Cumulative number of dead fish. 2 Effects: AN= appear no11nal; B =on bottom; NF =not found. 

-Page 3 of 9-

.ABC Study No. 66150 
Table 1. Hatched Fry Cumulative Mortality and Clinical Observations During the 28-Day Post-Hatch Period of Fathead 

Minnows Exposed to Dicrotophos Technical (ABC Study No. 66150) (continued) 

Mean Measured Number Da 8 Da 9 Da 10 Day 11 

Concentration Larvae No. Effects 2 No. Effects 2 No. Effects 2 No. Effects 2 

(mg a.i./L) Rep. Hatched Dead 1 Dead 1 Dead 1 Dead 1 

Control A 19 0 17 AN, 2NF 0 17 AN, 2NF 0 17 AN,2NF 0 17 AN, 2NF 

B 20 3 17 AN 3 17 AN 3 17 AN 3 17 AN 

c 19 4 13 AN; 2NF 4 13 AN; 2NF 4 13AN;2NF 4 13AN;2NF 

D 17 3 14AN 3 14AN 3 14AN 3 14AN 

0.327 A 20 2 18 AN 2 18 AN 2 18AN 2 18AN 

B 20 2 18 AN 2 18 AN 2 18 AN 2 18 AN 

c 20 2 18AN 2 IS AN 2 !SAN 2 !SAN 

D 18 3 15 AN 3 15AN 3 15 AN 3 15AN 

0.590 A 20 2 IS AN 2 18 AN 2 18 AN 2 18 AN 

B 16 1 14AN;INF 1 14AN; 1 NF 1 14AN;1NF 1 14AN; I NF 

c 16 4 12AN 4 12AN 4 12AN 4 12AN 

""C D 20 0 ·20AN 0 20AN 0 20AN 0 20AN _. 

_. 1.21 A 20 3 17 AN 3 17 AN 3 17 AN 3 17 AN 

B 20 2 18AN 2 18 AN 2 18AN 2 18 AN 

c 20 4 16AN 4 16 AN 4 16 AN 4 16AN 

D 19 0 19 AN 0 19 AN 0 19AN 0 19AN 

2.45 A 20 0 20AN 0 20AN 0 20AN 0 20AN 

B 20 0 20AN 0 20AN 0 20AN 0 20AN 

c 20 1 19AN 1 19AN 1 19 AN 1 19 AN 

D 19 0 19 AN 0 19 AN 0 19AN 0 19AN 

4.94 A 19 2 16AN;INF 2 16 AN; 1 NF 2 16AN;INF 2 16AN; 1 NF 

B 20 1 17AN;2NF 1 17AN;2NF 1 17 AN;2NF 1 17 AN;2NF 

c 19 2 17 AN 2 17 AN 2 17 AN 2 17AN 

D 18 0 18 AN 0 18AN 0 . 18AN 0 18 AN 

9.88 A 19 3 16AN 3 16AN 3 16AN 3 16AN 

B 18 0 17 AN; 1 NF 0 17 AN; 1 NF 0 17 AN; 1 NF 0 17AN;INF 

c 20 2 !SAN 2 !SAN 2 18 AN 2 !SAN 

D 20 2 !SAN 2 18 AN 2 18 AN 2 IS AN 

Cumulative number of dead fish. 2 Effects: AN= appear normal; NF =not found. 

-Page 4 of9-

ABC Study No. 66150 
Table 1. Hatched Fry Cumulative Mmiality and Clinical Observations During the 28-Day Post-Hatch Period of Fathead 

Minnows Exposed to Dicrotophos Technical (ABC Study No. 66150) (continued) 

Mean Measured Number Da 12 Da 13 Da 14 Day 15 

Conce~tration Larvae No. Effects 2 No. Effects 2 No: Effects 2 No. Effects 2 

(mg a.i.IL) Rep. Hatched Dead 1 Dead 1 Dead 1 Dead 1 

Control A 19 0 17AN,2NF 0 17 AN,2NF 0 17 AN, 2 NF 0 17AN,2NF 

B 20 3 17 AN 3 17 AN 3 17 AN 3 17 AN 

c 19 4 13 AN; 2NF 4 13 AN; 2 NF 4 13 AN; 2NF 4 13 AN; 2NF 

D 17 3 14AN 3 14AN 3 14AN 3 14AN 

0.327 A 20 2 18AN 2 18AN 2 18AN 2 18 AN 

B 20 2 18AN 2 · 18AN 2 18AN 2 18 AN 

c 20 2 18AN 2 18 AN 2 18 AN 2 18 AN 

D 18 3 15AN 3 15 AN 3 15AN 3 15 AN 

0.590 A 20 2 18 AN 2 18AN 2 18 AN 2 18 AN 

B 16 1 14AN; 1 NF 1 14AN; 1 NF 1 14AN;1NF 1 14AN; 1 NF 

c 16 4 12AN 4 12AN 4 12AN 4 12AN 

'"0 D 20 0 20AN 0 20AN 0 20AN 0 20AN 

...... 

N 1.21 A 20 3 17 AN 3 16AN; 1 NF 3 16AN; 1 NF 3 16 AN; 1 NF 

B 20 2 18 AN 2 18AN 2 18 AN 2 18AN ::· 

c 20 4 16AN 4 16AN 4 16 AN 4 16AN 

D 19 0 19AN 0 19AN 0 19AN 0 19AN 

2.45 A 20 0 20AN 0 20AN 0 20AN 0 20AN 

B 20 0 20AN 0 20AN 0 20AN 0 20AN 

c 20 1 19 AN 1 19AN 1 19AN 1 19AN 

D 19 0 19AN 0 19AN 0 19AN 0 19AN 

4.94 A 19 2 16 AN; 1 NF 2 16 AN; 1 NF 2 16 AN; 1 NF 2 16AN; 1NF 

B 20 1 17 AN; 2NF 1 17 AN; 2NF 1 17 AN; 2 NF 1 17AN;2NF 

c 19 2 17 AN 2 17 AN 2 17 AN 2 17 AN 

D 18 0 18AN 0 18AN 0 18AN 0 18AN 

9.88 A 19 3 16AN 3 16AN 3 16AN 3 16AN 

B 18 0 17AN;1NF 0 17AN;1NF 0 17AN;1NF 0 17 AN; 1 NF 

c 20 2 18 AN 2 18AN 2 18AN 2 18AN 

D 20 2 l8AN 2 18 AN 2 18 AN 2 18 AN 

1 Cumulative number of dead fish. 2 Effects: AN= appear nonnal; NF =not found. 

-Page 5 of 9-

.ABC Study No. 66150 
Table 1. Hatched Fry Cumulative Mortality and Clinical Observations During the 28-Day Post-Hatch Period of Fathead 

Minnows Exposed to Dicrotophos Technical (ABC Study No. 66150) (continued) 

Mean Measured Number Da 16 Da 17 Da;_: 18 Da;_: 19 

Concentration Larvae No. Effects 2 No. Effects 2 No, Effects 2 No. Effects 2 

(mg a.i.IL) Rep. Hatched Dead 1 Dead 1 Dead 1 Dead 1 

Control A 19 0 17 AN, 2NF 0 17 AN,2NF 0 17 AN, 2NF 0 17 AN, 2NF 

B 20 3 17 AN 3 17 AN 3 17 AN 3 17 AN 

c 19 4 13 AN; 2 NF 4 13 AN; 2NF 4 13 AN; 2NF 4 13 AN; 2NF 

D 17 3 14AN 3 14AN 3 14AN 3 14AN 

0.327 A 20 2 18AN 2 18 AN 2 18AN 2 18AN 

B 20 2 18 AN 2 18AN 2 18 AN 2 18AN 

c 20 2 18 AN 2 18 AN 2 18AN 2 18AN 

D 18 3 15 AN 3 15AN 3 15 AN 3 15 AN 

0.590 A 20 2 18 AN 2 18AN 2 18 AN 2 18AN 

B 16 1 14AN; 1 NF 1 14 AN; 1 NF 1 14 AN; 1 NF 1 14AN; 1 NF 

c 16 4 12AN 4 12AN 4 12AN 4 12AN 

'"'0 D 20 0 20AN 0 20AN 0 20AN 0 20AN ....... 

w 1.21 A 20 3 16 AN; 1 NF 3 16 AN; 1 NF 3 16 AN; 1 NF 3 16 AN; 1 NF 

B 20 2 18 AN 2 18 AN 2 18AN 2 18 AN 

c 20 4 16 AN 4 16AN 4 16AN 4 16AN 

D 19 0 19 AN 0 19AN 0 19AN 0 19 AN 

2.45 A 20 0 20AN 0 20AN 0 20AN 0 20AN 

B 20 0 20AN 0 20AN 0 20AN 0 20AN 

c 20 1 19AN 1 19AN 1 19AN 1 19 AN 

D 19 0 19AN 0 19AN 0 19 AN 0 19 AN 

4.94 A 19 2 16AN;1NF 2 16 AN; 1 NF 2 16AN; 1 NF 2 16 AN; 1 NF 

B 20 1 17 AN; 2NF 1 17AN;2NF 1 17 AN;2NF 1 17AN;2NF 

c 19 2 17 AN 2 17 AN 2 17 AN 2 17 AN 

D 18 0 18 AN 0 18 AN 0 18AN 0 18 AN 

9.88 A 19 3 16AN 3 16AN 3 16AN 3 16AN 

B 18 0 17 AN; 1 NF 0 17 AN; 1 NF 0 17AN;1NF 0 17AN;1NF 

c 20 2 18 AN 2 18AN 2 18AN 2 18 AN 

D 20 2 18AN 2 18 AN 2 18 AN 2 !SAN 

Cumulative number of dead fish. 2 Effects: AN= appear nonnal; NF =not found. 

- Pag1~ 6 of9-

ABC Study No. 66150 
Table 1. Hatched Fry Cumulative Mortality and Clinical Observations During the 28-Day Post-Hatch Period of Fathead 

Minnows Exposed to Dicrotophos Technical (ABC Study No. 66150) (continued) 

Mean Measured Number Dar20 Dar21 Da 22 Daz23 

Concentration Larvae No. Effects 2 No. Effects 2 No. Effects 2 No. Effects 2 

(mg a.i.!L) Rep. Hatched Dead 1 Dead 1 Dead 1 Dead 1 

Control A 19 0 17 AN, 2NF 0 17 AN, 2NF 0 17 AN, 2NF 0 ARAN 

B 20 3 17 AN 3 17 AN 3 17 AN 3 ARAN 

c 19 4 13 AN; 2NF 4 13 AN; 2NF 4 13 AN; 2NF 4 ARAN 

D 17 3 14AN 3 14AN 3 14AN 3 ARAN 

0.327 A 20 2 18 AN 2 18 AN 2 18 AN 2 ARAN 

B 20 2 18 AN 2 18 AN 2 18 AN 2 ARAN 

c 20 2 18 AN 2 18AN 2 18AN 2 ARAN 

D 18 3 15 AN 3 15 AN 3 15 AN 3 ARAN 

0.590 A 20 2 18AN 2 18 AN 2 18AN 2 ARAN 

B 16 1 14AN; 1 NF 1 14AN; 1NF 1 14 AN; 1 NF 1 ARAN 

c 16 4 11AN 4 11AN 4 12AN 4 ARAN 

-o D 10 0 lOAN 0 lOAN 0 lOAN 0 ARAN ..... 

..j::o. 1.11 A 10 3 16AN;1NF 3 16AN;1NF 3 16AN;1NF 3 ARAN 

B 10 1 18AN 2 18 AN 1 17 AN 1 C 2 ARAN 

c 10 4 16AN 4 16AN 4 16AN 4 ARAN 

D 19 0 19 AN 0 19AN 0 19AN 0 ARAN 

2.45 A 20 0 lOAN 0 lOAN 0 lOAN 0 ARAN 

B 10 0 lOAN 0 lOAN 0 lOAN 0 ARAN 

c 10 1 19AN 1 19AN 1 19 AN 1 ARAN 

D 19 0 19 AN 0 19AN 0 19AN 0 ARAN 

4.94 A 19 1 16 AN; 1 NF 1 16AN;1NF 2 16 AN; 1 NF 1 ARAN 

B 10 1 17 AN; 2NF 1 .17 AN; 2NF 1 17 AN; 1 NF 1 ARAN 

c 19 1 17 AN 2 16 AN; 1 NF 2 16 AN; 1 NF 2 ARAN 

D 18 0 18AN 0 18 AN 0 18AN 0 ARAN 

9.88 A 19 3 16 AN 3 16AN 3 16AN 3 ARAN 

B 18 0 17AN;1NF 0 17AN;1NF 0 17AN;1NF 0 ARAN 

c 10 1 18 AN 2 18AN 1 18AN 1 ARAN 

D 20 2 18 AN 2 18AN 2 18AN 1 ARAN 

Cumulative number of dead fish. 2 Effects: AN= appear nonnal; C =spinal curvature; NF =not found; ARAN = all remaining surviving fish appear nonnal. 

~Page 7 of 9-

ABC Study No. 66150 

··--------·- -------------·-- . 
Table 1. Hatched Fry Cumulative Mortality and Clinical Observations During the 28-Day Post-Hatch Period of Fathead 

Minnows Exposed to Dicrotophos Technical (ABC Study No. 66150) (continued) 

Mean Measured Number Da 24 Da.J::25 Dax26 Da~27 

Concentration Larvae No. Effects 2 No. Effects 2 No. Effects 2 No. Effects 2 

(mg a.i./L) Rep. Hatched Dead 1 Dead 1 Dead 1 Dead 1 

Control A 19 0 17 AN, 2NF 0 17 AN, 2 NF 0 17 AN, 2NF 0 17 AN,2NF 

B 20 3 17 AN 3 17 AN 3 17 AN 3 17 AN 

c 19 4 13 AN; 2NF 4 13 AN;2NF 4 13 AN; 2NF 4 13AN;2NF 

D 17 3 14AN 3 14AN 3 14AN 3 14AN 

0.327 A 20 2 18AN 2 18 AN 2 18 AN 2 18AN 

B 20 2 18 AN 2 18 AN 2 18 AN 2 18AN 

c 20 2 18AN 2 18AN 2 18AN 2 18 AN 

D 18 3 15 AN 3 15 AN 3 15 AN 3 15 AN 

0.590 A 20 2 1'8AN 2 18AN 2 18AN 2 18 AN 

B 16 1 14AN;1NF 1 14AN; 1 NF 1 14AN;1NF 1 14AN; I NF 

c 16 4 12AN 4 12AN 4 12AN 4 12AN 

-u D 20 0 20AN 0 20AN 0 20AN 0 20AN 

..... 

CJ'1 1.21 A 20 3 16 AN; 1 NF 3 16AN;1NF 3 16 AN; 1 NF 3 16 AN; I NF 

B 20 2 18 AN 2 18AN 2 18AN 2 18 AN 

c 20 4 16AN 4 16 AN 4 16AN 4 16AN 

D 19 0 19AN 0 19AN 0 19 AN 0 19AN 

2.45 A 20 0 20AN 0 20AN 0 20AN 0 20AN 

B 20 0 20AN 0 20AN 0 20AN 0 20AN 

c 20 1 "19AN 1 19AN 1 19AN 1 19AN 

D 19 0 19 AN 0 19 AN 0 19AN 0 19 AN 

4.94 A 19 2 16 AN; 1 NF 2 16 AN; 1 NF 2 16 AN; 1 NF 2 16 AN; 1 NF 

B 20 1 17 AN; 2 NF 1 17AN;2NF 1 17 AN;2NF 1 17AN;2NF 

c 19 2 16 AN; 1 NF 2 16 AN; 1 NF 2 16AN;1NF 2 16 AN; 1 NF 

D 18 0 18 AN 0 18 AN 0 18AN 0 !BAN 

9.88 A 19 3 16AN 3 16AN 3 16AN 3 16AN 

B 18 0 17 AN; 1 NF 0 17 AN; 1 NF 0 17AN;1NF 0 17 AN; 1 NF 

c 20 .2 18 AN 2 18AN 2 18 AN 2 18 AN 

D 20 2 18 AN 2 18AN 2 18 AN 2 18 AN 

Cumulative number of dead fish. 2 Effects: AN = appear nonnal; NF =not found. 

-Page 8 of9-

ABC. Study No. 66150 

----- ~- -- -· .. - ·----·----- . -------·-····· ---- ·--· - ----------------- --- ----·- . ·····-------------- ····--···-·· 
Table 1. Hatched Fry Cumulative Mortality and Clinical Observations During the 28-Day Post-Hatch Period of Fathead 

Minnows Exposed to Dicrotophos Teclmical (ABC Study No. 66150) (continued) 

Mean Measured Number Day 28 

Concentration Larvae No. 2 

(mg a.i./L) Rep. Hatched Dead I Effects 

Control A 19 2 I 7 AN, 2 NF 

B 20 3 17 AN 

C 19 6 13AN;2NF 

D 17 3 14 AN 

0.327 A 20 2 18 AN 

B 20 2 18 AN 

C 20 2 18 AN 

D 18 3 ·15AN 

0.590 A 20 2 .18 AN 

B 16 2 14 AN; 1 NF 

C 16 4 12 AN 

D 20 0 20AN 

~ 1.21 ~ ~~ i 16 ~rl~NF 

C 20 4 16 AN 

D 19 0 19 AN 

2.45 A 20 1 .J9 Al'J; 1NF 

B 20 0 20 AN 

C 20 1 19 AN 

D 19 0 19 AN 

4.94 A 19 3 16AN; 1 NF 

B 20 3 17 AN; 2 NF 

C 19 3 16AN;1NF 

D 18 0 18 AN 

9.88 A 19 3 16 AN 

B 18 1 17AN;1NF 

C 20 2 18 AN 

D 20 2 18 AN 1 Cumulative number of dead fish. Fish counted as not found at test te1mination added to cumulative number of dead. 2 Effects: AN= appear nonnal; NF =not found. 

-Page 9 of 9-

ABC Study No. 66150