1

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

 OFFICE OF 

 PREVENTION, PESTICIDES 

 AND TOXIC SUBSTANCES 

May 14, 2009 

MEMORANDUM

SUBJECT: Response to Comments, Revised Label Table, and Appendices. 

The Special Review and Reregistration Division’s (SRRDs) Response to 

Comments and Attachments on EPA’s Reregistration Eligibility Decision 

(RED) Document for MGK-264 (OPP Docket #OPP-2005-0040). 

FROM: Cathryn O’Connell, Chemical Review Manager 

 Reregistration Branch II 

 Special Review and Reregistration Division 

Through: Margaret Rice, Branch Chief 

 Reregistration Branch II 

 Special Review and Reregistration Division 

TO: Richard P. Keigwin, Jr. 

 Director 

Special Review and Reregistration Division 

This document is EPA’s response to public comments that were directed towards 

product labeling, risk mitigation, or the upcoming registration review process for the 

pyrethroids, pyrethrins, and synergist chemicals. These comments were submitted 

during the post-RED period of the public participation process of the MGK-264 RED. 

The documents responding to public comments on the human health and 

ecological risk assessments can be located in the MGK-264 docket. 

Comments were received from the California Regional Water Quality Control 

Board, California Stormwater Quality Association (CASQA), County Sanitation Districts 

of LA County, MGK Company, as well as individuals. 

The following comments and responses have been grouped by these topic areas: 

(1) water contamination, (2) registration review of pyrethroid chemicals, and (3) other 

comments and (4) labeling changes. A revised label table along with complete 

appendices accompanies this document and reflects the changes to the RED. 
2

Attachments: 

• MGK-264 Revised Label Table 

• Appendix A: Uses Supported for Reregistration 

• Appendix B: Generic Data Requirements Table 

• Appendix C: Technical Support Documents 

• Appendix D: Database Citations 

• Appendix E: EPA’s Acute Toxicity Batching 
3

SRRD’s Response to Public Comments to the 

MGK-264 Reregistration Eligibility Decision 

I. Water Contamination Comments 

Comment: The California Stormwater Quality Association (CASQA) recommended the 

Agency clarify the additional application restrictions for outdoor residential products on 

the label table intended to prevent run-off of pyrethrins into urban sewers and streams. 

CASQA stated the language would more fully meet this intent if modified as stated in the 

comments. 

SRRD Response: Since the MGK-264 RED was finalized, the Agency has finalized PR 

Notice 2008-1 that allows registrants to voluntarily change their environmental hazard 

statements on residential products so users will be able to better understand how to apply 

consumer products to minimize environmental hazards. The statements included in this 

PR Notice are similar to the language that was required in the MGK-264 RED, and the 

intention is the same for both statements, to help consumers use these products correctly 

in order to minimize environmental risks. Therefore, the MGK-264 RED labeling will be 

updated to require the same environmental hazard statements for residential products that 

are included in PR Notice 2008-1. 

Comment: CASQA also stated that professional products for urban use (i.e., products for 

landscaping, rights of way, etc.) should have stewardship language on their labels. CASQA 

included labeling suggestions in their comments. The CA Regional Water Quality Control 

Board, San Francisco Bay Region submitted similar comments. 

SRRD Response: The Agency agrees that MGK-264 products for professional use 

should have language on the labels to prevent the run-off of MGK-264 residues down 

storm drains. Therefore, in addition to the revisions made to the Environmental Hazards 

statements, the following statements have been added to the amended MGK-264 label 

table for end use products primarily intended for occupational use by commercial pest 

control operators. 

Products labeled for use around or near floor drains or sewer drains:

 “Do not apply directly into sewers or drains, or to any area like a gutter 

where drainage to storm sewers, water bodies, or aquatic habitat can 

occur.” 

Comment: The County Sanitation Districts of Los Angels County and the California 

Stormwater Quality Association (CASQA) commented that environmental hazard statements, 

similar to the required outdoor environmental hazard statements, be added to all indoor 

products. The reasons are that there is potential exposure to pyrethroids and synergists 

down the drain after using pet shampoos, discharging of water used to clean surfaces that 

were treated with MGK-264, and washing materials that have been treated in a washing 

machine. The Sanitation Districts and CASQA believe toxicity statements should be added to 

indoor use products, along with statements about consulting with the local sewage treatment 
4

agencies for uses that may result in a discharge down-the-drain, and how to dispose of water 

containing MGK-264. 

SRRD Response: Through various labeling initiatives (some discussed below), OPP 

hopes to reduce the overall amount of MGK-264 discharged into both storm water and 

sewage drainage systems. However, at this time, the Agency does not believe additional 

aquatic environmental hazard statements, similar to the environmental hazard statements 

on outdoor products, is appropriate on indoor use products since local sewage treatment 

plants may not be equipped to deal with many consumer calls. 

II. Registration Review of Pyrethroid Chemicals 

Comment: The California Stormwater Quality Association (CASQA) and the CA 

Regional Water Control Board, San Francisco Bay stated concerns that the pyrethroids 

and synergists are not scheduled for Registration Review until 2010, and mitigation 

would not occur until 2011. They state that this puts municipalities in an untenable 

position because they must comply with the Clean Water Act immediately. CASQA 

requested Registration Review be initiated immediately for the pyrethroids and 

synergists, or a special review be initiated. Additionally, according to the Water Board, 

pyrethroids are anticipated to be the cause of impaired water bodies, listed on the 2008 

303(d) list. 

SRRD Response: The Permethrin, Resmethrin, Cypermethrin, Pyrethrins, Piperonyl 

Butoxide, and MGK-264 Reregistration Eligibility Decisions were signed in 

Spring/Summer 2006, and decisions for non-food pyrethroids, including allethrin 

stereoisomers, tetramethrin, and sumethrin, were completed in 2008. Therefore, the 2010 

date for Registration Review to begin for the pyrethoid, pyrethrins, and synergists (PPS) 

group of chemicals allows time for the risk mitigation and label changes identified in 

these REDs to be incorporated. Further, in the recent PPS REDs, the Agency identified 

a number of limitations in the reregistration of these chemicals, such as no 

urban/residential model available to assess potential ecological risks from residential 

uses; and an inability to assess (or compare) ecological impacts from PPS chemicals as a 

group because a large majority of the pyrethroids were registered after 1984. 

In order to address these limitations and allow the registration review risk assessments to 

be more refined, there are several on-going efforts to prepare for registration review of 

the PPS chemicals including: determine whether the pyrethroids share a common mode 

of action; revise spray drift language for pyrethroid agricultural labels; identify a model 

and appropriate scenarios for use in urban run-off modeling; compile detailed use and 

usage information about the PPS chemicals, both agricultural and residential uses; and 

identify data needs. Additionally, the Agency is coordinating with the California 

Department of Pesticide Regulation (CDPR), which is currently conducting its 

reevaluation of pyrethroids. The reevaluation includes calling in new and additional data, 

which will be useful to the Agency’s Registration Review process of the PPS chemicals 

which begins in 2010 for some chemicals. Therefore, the Agency does not believe it 

would be prudent to initiate the Registration Review of the PPS chemicals any earlier 

than currently scheduled. 
5

Comment: CASQA and the CA Regional Water Control Board, San Francisco Bay 

stated that OPP needs to initiate development of an urban run-off model as soon as 

possible. An empirical model should be used opposed to the mechanistic model OPP 

typically uses. 

SRRD Response: The Agency recognizes the need to identify a screening-level model 

for urban pesticide uses and has begun to discuss the state of urban modeling and the 

potential avenues for future advances internally and with stakeholders. Improvements in 

the resolution of GIS databases may allow better representation of the impervious and 

pervious portions of a typical urban landscape. For example, as it becomes more clear 

which uses are most likely to lead to transport of pyrethroids and synergists to surface 

water, the conceptual model of how urban transport should be simulated will be more 

focused. 

Comment: CASQA commented that U.S. EPA may be generating a “Data Call-In” (DCI) 

for pyrethroids and synergists to provide data for future pyrethroids and synergist reviews. 

They appreciate that U.S. EPA recognizes that data critical to managing risks from 

pyrethroids is currently not available and that EPA intends to require that pyrethroid 

manufacturers provide the needed data. Among data needed for pyrethroids water quality 

management, CASQA believes the following information is high priority: data to support 

urban runoff modeling, application instructions, and aquatic sediment data. In addition, the 

California Department of Pesticide Regulation (DPR) has initiated a data call in process for 

pyrethroids called “re-evaluation”. CASQA anticipates that this process will generate a 

substantial amount of information that would be useful to U.S. EPA. CASQA recommends 

that U.S. EPA coordinate with DPR in developing the DCI. CASQA asks U.S. EPA to 

request, obtain, and review all data submitted to DPR. CASQA stands ready to provide 

formal support for U.S. EPA’s request to review data submitted to DPR. 

SRRD Response: The Agency appreciates the recommendation provided by the CASQA, 

and is in the process of planning for the pyrethroid and synergist Registration Review 

process. As part of the initial phase of registration review a preliminary work plan will 

provide an opportunity for stakeholders to comment on the anticipated data the Agency will 

require in order to complete a risk assessment. Since this will be the first chance to evaluate 

all of the pyrethroids, pyrethrins, and synergists at once it will be a good opportunity to call 

in data necessary to assess the chemicals together. The Agency also recognizes that it needs 

to gain a better understanding of the residential and urban application of pyrethroids, to 

identify an urban run-off model, and more aquatic sediment data. The Agency is continuing 

to coordinate with the CDPR, and the two organizations have continued to share data and 

reviews on these chemicals. 

Comment: CASQA stated U.S. EPA has taken important steps toward protecting water 

quality throughout its various reregistration processes. However, CASQA stated that U.S. 

EPA needs to better integrate surface water quality protection into its pesticide registration 

and regulatory review programs. CASQA stated that coordination between U.S. EPA offices 

in reviewing pesticide ingredients is essential to Clean Water Act implementation; it also 

provides an appropriate method of meeting the Federal Insecticide, Fungicide, and 
6

Rodenticide Act’s goal of preventing unreasonable adverse impacts from pesticide use. The 

CA Regional Water Control Board, San Francisco Bay submitted similar comments. 

SRRD Response: The Office of Pesticide Programs (OPP) agrees that coordination is 

essential between OPP and the Office of Water. In its effort to plan for the upcoming 

registration review of the pyrethroid case of chemicals, OPP has initiated discussions with 

OW to address issues that affect both Offices. 

Comment: The CA Regional Water Control Board, San Francisco Bay Region included 

steps to be taken in the near term in their comments to the Agency. The steps include 

OPP completing a cumulative environmental risk assessment for pyrethroids; completing 

an alternatives assessment that considers both low risk and non-pesticide alternatives; 

completing a cluster assessment for problematic outdoor urban insecticide application; 

and assessing whether urban uses of pyrethroids pose unreasonable risks, taking into 

account the above information and the cost of non-compliance with the Clean Water Act. 

SRRD Response: The Agency appreciates the suggestions provided by the CA Regional 

Water Board, San Francisco Bay Region. As stated above, OPP is in the process of 

planning for the registration review of pyrethroids, pyrethrins, and synergists chemicals. 

As part of its planning effort, OPP is working closely with CA DPR as it conducts its 

reevaluation of pyrethroids, as well as coordinating with EPA’s Office of Water. As the 

planning progresses, OPP will continue to discuss these issues and the feasibility of the 

various assessments with the Water Board and other stakeholders. 

Comment: Various comments from the California Regional Water Quality Control Board, 

California State Water Resources Control Board, and the County Sanitation Districts of LA 

County state that additional data should be called in to help assess the potential ecological 

risks from residential use of MGK-264, and other compounds.

SRRD Response: The Agency appreciates the recommendation provided in the 

comments and is in the process of planning for the pyrethroid registration review process, 

which includes MGK-264. The Agency also recognizes that it needs to gain a better 

understanding of the residential and urban uses of this group of chemicals, to identify an 

urban run-off model, and evaluate more aquatic sediment data. The Agency is 

coordinating with the CDPR, and the two organizations have been sharing data and 

reviews when possible. 

III. Other Comments 

Comment: MGK Company submitted several comments related to data that have 

already been submitted to fulfill some of the listed outstanding data requirements. 

SRRD Response: At the time of the RED these data had not yet been reviewed and 

determined to be acceptable. Registrants may cite these data when responding to the 

Data Call-In. 
7

Comment: The use of metered release devices was limited in the MGK-264 RED to 

areas where children and other sensitive populations may be present like day-care centers 

and schools. MGK Company requests EPA clarify that use of these devices is still 

permitted in kitchens of these sites, just not in any area where children or the elderly may 

be present. 

SRRD Response: The purpose of the RED mitigation to restrict application of metered 

release products was to prevent sensitive populations from being exposed to these 

devices. Other areas of these institutions where children, the elderly, or other sensitive 

populations are not present, which may include kitchens, are not subject to this 

restriction. The Agency has included two labeling statements to clarify how these 

devices may be used. The two statements are copied below and included in the label 

table. 

“Not for use in residential areas.” 

“Do not use in nurseries or rooms where infants, ill, or aged persons are 

present.” 

IV. Labeling Changes: 

Dermal Mitigation 

Based on a review of a 21-day dermal toxicity study which was required in the 

MGK-264 RED, no dermal risk assessments are needed for exposures to MGK-264. All 

dermal mitigation specified in the 2006 RED is no longer required and the label table has 

been revised to reflect these changes. Please see the HED Response to Comments on 

MGK-264 (Donovan, W. and Doherty, J., 3/6/2007) for details. 

Other Changes 

• Due to the proposed revocation of tolerances for food stored in bags, all directions 

for use on “food stored in bags” have been removed from the label table and 

Appendix A. 

• A ventilation statement requiring ventilation for at least 2 hours for total release 

foggers was added that was similar to other ventilation statements required for 

other chemicals with a similar use. If registrants provide data to support different 

ventilation periods this time duration may be changed on a case-by-case basis. 

• In the 2006 RED some label language was developed for metered release systems 

indoors (for barn or industrial type areas). Although the risk assessments were 

complete, some additional uses that did not fit into this category were brought to 

the Agency’s attention after the RED. In order to provide a complete set of label 

instructions for the other kinds of systems being developed, additional labeling is 

included in this label table for indoor misting systems that may be used in 

commercial barns, stables, and animal quarters.