UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

PREVENTION, PESTICIDES 

AND TOXIC SUBSTANCES 

PC code: 05700 1 

DP Barcode: D29563 1 

MEMORANDUM 

SUBJECT: Response to Comments for MGK-264 Risk Assessment 

TO: Cathryn O'Connell 

Special Review and Reregistration Division (7508P) 

FROM: William P. Eckel, Ph.D. 

Environmental Risk Branch I1 2 

Environmental Fate and Effects Division (7507P) 

THRU: Tom Bailey, Ph.D. - -.._ \>w-- Chief, Environmental Risk BranchW 

Environmental Fate and Effects Division (7507P) 

DATE: January 5,2007 

This memorandum provides EFED's responses to comments on the MGK-264 risk assessment. 

This response is for comments received in October, 2006. Please note that one comment from 

Country Sanitation Districts of Los Angeles County requires a response from SRRD. 

If you have any questions, please contact me (WPE) at 305-645 1. 

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Text Searchable Document
Comment 2 from California Regional Water Quality Control Board 

Comment 3 from Country Sanitation Districts of Los Angeles County 

Comment 

Recommend additionalhevised label language for use 

in drains, shampoos, and professional and consumer 

products. 

Develop urban runoff model that is empirical not 

mechanistic 

Request to include the model in the revised eco 

assessment. 

Improve the sewer discharge model with OW'S 

information 

Identify priorities for MGK-264 DCI and list of data 

gaps. 

Response 

The suggested language appears reasonable. 

EPA has developed residential and impervious 

surface scenarios for the PRZM-EXAMS model to 

address this issue. 

The model may be applied when MGK-264 comes up 

for Registration Review. 

The Down-the-Drain model is part of E-Fast, and was 

developed by OPPT. That office would need to make 

any revisions. Wastewater treatment and sewage 

sludge disposal are the responsibility of the Office of 

Water 

Data to support urban runoff modeling may not be 

necessary given the development of 

residentiaYimpervious surface scenarios for PRZMEXAMS. Data to support "down the drain" 

assessments, especially sewage sludge, are the 

responsibility of the Office of Water and OPPT. 

Surface water monitoring data may be requested after 

the submission of data to fill toxicity and fate data 

gaps. Development of Water Quality Criteria is done 

by the Office of Water. 

Comment 

Disagree with EPA's use of stream dilution factors 

because not all facilities in the country dilution credits 

in the NPDES permits for environmental reasons. 

EPA should use E-FAST to calculate a median surface 

water concentration without dilution factor for use as 

the chronic concentration in the risk analysis. For 

acute concentration, EPA should calculate a surface 

water concentration assuming a local high-end 

scenario appropriate for the pesticide (like using a 

shampoo). 

Develop an improved wastewater discharge 

methodology using April 2006 version of E-FAST. 

Toxicity data for formulated product: acute and 

chronic, freshwater and estuarinelmarine fish, 

invertebrate and whole sediment toxicity tests. This is 

needed to evaluate down-the-drain assessment. 

Response 

"Down-the-Drain" is part of E-Fast, and is 

maintained by OPPT. Any modifications would need 

to be made by that office. 

"Down-the-Drain" is part of E-Fast, and is 

maintained by OPPT. Any modifications would need 

to be made by that office. 

"Down-the-Drain" is part of E-Fast, and is 

maintained by OPPT. Any modifications would need 

to be made by that office. 

Formulated product data is needed to evaluate the 

toxicity of the synergized mixture. 
Comment 4 from MGK Company 

Request that aquatic toxicity label statements be added 

to all labels if the data requested indicates this is 

appropriate. 

Requests to work with OPP and OW to develop 

wastewater discharge methodology for evaluating 

impacts to aquatic organisms from sewer discharges 

during reg-review. 

EPA will evaluate the need for these label statements 

when the needed data are submitted and reviewed. 

SRRD to respond 

Comment 5 from CASQA 

Comment 

MGK does not support use of MGK-264 in wide area 

outdoor uses, so MGK Co. believes the eco risks are 

even less than EPAs current risk assessment. 

Based on use patterns, prior to requiring mixture data, 

look for monitoring data detects of MGK-264 in the 

environment. 

Response 

The actual ecological risks may be lesser or greater 

than stated. There is much uncertainty in the current 

assessment because of the numerous data gaps. 

Mixture data are needed for labeling statements, and 

to determine if monitoring is needed. 

Comment 

Potential negative impact of 

pyrethroids/pyrethrins/synergists to urban creeks. 

Subject 

Ecological 

Response 

EPA acknowledges the 

possibility that MGK-264 may 

synergize other contaminants. 

Further research is needed to 

determine if this is a 

widespread phenomenon.