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OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

 

PC Code: 128965

DP Barcode: 398044, 396054

Date: February 7, 2012

MEMORANDUM

SUBJECT: Drinking Water Assessment for the Etofenprox Label Amendment

TO: Andrew Ertman, Risk Manager Reviewer

Barbara Madden, Risk Manager

Minor Use Team

Registration Division (7505P)

Kristin Rury, Biologist

Paula Deschamp, Branch Chief 

Risk Assessment Branch III

Health Effects Division (7509P)

FROM: Chuck Peck, Environmental Engineer

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

REVIEWED

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

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

APPROVED

BY: Marietta Echeverria, Branch Chief

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

This memo is in response to a request for drinking water estimates based on an IR4 request to 

remove the cropland and pastureland application restrictions from the ZenivexTM E4 Ready to 

Use (RTU) (EPA Reg. No. 2724-807) and ZenivexTM E20 (EPA Reg. No. 2724-791) labels, both 

of which contain the active ingredient etofenprox. ZenivexTM E4 RTU and ZenivexTM E20 are

insecticides used in ultra low volumes to control mosquitoes, non-biting midges, and biting and 

non-biting flies. The labels have been amended to allow application over agricultural areas prior 

to or following harvest for the control of adult mosquitoes within or adjacent to these areas. 

In January 2010, EFED conducted a drinking water assessment which included a quantitative 

assessment of the proposed use on mound-building ants and a closer evaluation of all currently 

labeled outdoor uses (DP Barcode 370749, 371459). In the 2010 assessment, the highest surface 
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water source drinking water concentrations occurred for a modeled co-occurrence of use on rice 

and vector control. Estimated groundwater concentrations were several orders of magnitude less 

than those in surface water. The results from the previous assessment are provided in Table 1. 

As the amendment to the proposed label does not increase the maximum application rates, EFED 

recommends using the estimated drinking water concentrations from the January 2010 

assessment. It should be noted that EFED has reviewed a new aqueous photolysis study 

submitted for etofenprox (MRID 48353301) and, while the half-life has been reduced, the 

estimated drinking water concentrations were not impacted.

Table 1. Total Residue EDWCs of Etofenprox in Surface Water and Ground Water for Current Uses Based 

on the Maximum Use Patterns, Rice and Outdoor Foggers.

Source Use (modeled rate) 1-in-10-year 

Peak Exposure 

(μg/L)

1-in-10-year 

Annual Mean 

Exposure (μg/L)

30-year Mean 

Exposure (μg/L)

Surface water Rice & vector control

(0.45 lbs a.i./A/year)B

1.4 1.2 <1.2

Surface water Rice (0.27 lbs a.i./A/year) 1.0 1.0 <1.0

Ground water Outdoor fogger (0.52 lbs a.i./A/year) 3.0 x 10-3 3.0 x 10-3 <3.0 x 10-3

A Proposed uses include a proposed use for mound-building ant control and a proposed label amendment 

for the current outdoor structural use.

B These EDWCs represent an upper bound on co-occurrence between use on rice and vector control use.