UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF           

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

     PC code: 121001

DP Barcode: D313456, D314420

MEMORANDUM

SUBJECT:	Drinking Water Assessment for Sethoxydim: Proposed Uses on
Buckwheat, Okra, Borage, Dill, Root Vegetables, and Turnip Greens

TO:		Daniel Rosenblatt RM05

Registration Division (7505C)

		

FROM:	William P. Eckel, Ph.D.

Environmental Risk Branch II

Environmental Fate and Effects Division (7507C)

THRU:	Tom Bailey, Ph.D.

Chief, Environmental Risk Branch II

Environmental Fate and Effects Division (7507C)

DATE:	March 3, 2006

	This memorandum addresses your request for a drinking water assessment
(DWA) for the new uses of Sethoxydim proposed by the Interregional
Research Project 4 (IR-4).  This includes turnip greens (D314420) and
buckwheat, okra, borage, dill, and root vegetables (D313456).

	A Tier 1 DWA (D312559) was completed on February 7, 2005 for the
Reregistration Eligibility Decision (RED).  The maximum use rate modeled
in the 2005 DWA was 4 applications of 0.47 lb active ingredient (a.i.)
per acre.  According to our reading of the IR-4 submissions, the
proposed new uses are at application rates and frequencies lower than in
the 2005 DWA.  The maximum proposed new use rates are on okra (3
applications of 0.3 lb a.i./acre or 1.1 lb total per season) and
buckwheat, borage and dill (each 2 applications of 0.47 lb a.i./acre). 
Thus, the previous DWA still provides the highest estimated drinking
water concentrations (EDWCs).  These EDWCs should be used in the present
risk assessment.

	The EDWCs from the 2005 DWA are as follows: ground water, 1.5 ppb;
surface water acute, 130 ppb; and surface water chronic, 16 ppb.  All
EDWCs are for total sethoxydim residues including degradates of concern.

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