                 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                            WASHINGTON, D.C.  20460
                                       
                                       
                                       
              OFFICE OF CHEMICAL SAFETY
AND POLLUTION PREVENTION
                                       
                                August 2, 2012
                                                                PC Code: 117403
                                                 MEMORANDUM 	DP Barcode: 401259

      SUBJECT:	An IR-4 Action - Drinking Water Exposure Assessment for Proposed New Use of Clopyralid on Teff
      
      FROM:		James Lin, Environmental Engineer
                  Environmental Risk Branch II
                  Environmental Fate and Effects Division (7507P)
      		
      THRU:		Brian Anderson, Branch Chief
      			Greg Orrick, Environmental Scientist
                  Environmental Risk Branch II
      			Environmental Fate and Effects Division (7507P)
      
      TO:			Kathryn Montague, Risk Manager
				Michael Walsh, Risk Manager Reviewer 
				Herbicide Branch
                  Registration Division (7505P)
            AND
                  Barbara Madden, Risk Manager
                  Laura Nollen, Risk Reviewer
                  RIMUERB
                  Registration Division (7505P)
     
     This memo presents the drinking water exposure assessment of clopyralid use on teff. The proposed single and seasonal maximum application rate is 1/3 pint of Stinger(R) per acre (0.125 lb a.i./ac) .  This proposed use rate is less than the currently labeled maximum rate of 0.5 lbs a.i./ac, which was assessed in the drinking water exposure assessment dated December 19, 2011 (DP barcode 391398).  Therefore, the drinking water exposure estimates from the 2011 assessment (shown below) should continue to be used for the human health risk assessment.
     
                                     Media
                            Max Concentration (ppb)
                                    Source
                                 Ground water
                                     0.53
                                NAWQA (Oregon)
                             Surface water (acute)
                                      45
       FIRST (non-food crop  -  1 application per year @ 0.5 lb a.i./A)
                            Surface water (chronic)
                                      12
       FIRST (non-food crop  -  1 application per year @ 0.5 lb a.i./A)

