  	UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

	WASHINGTON, D.C.  20460

     	               OFFICE OF  

          		PREVENTION, PESTICIDES

 AND TOXIC SUBSTANCES 

DP Barcodes: 313814

 PC Code:       128008

 Date:             5/5/2005

SUBJECT:	Drinking Water Memo for Proposed Uses of Boscalid on Leafy
Vegetables

TO:		Daniel Rosenblatt, Risk Manager

Barbara Madden, Risk Manager Reviewer

Registration Division

FROM:	Christopher J. Salice, Biologist

Kevin Costello, Geologist, RAPL

Environmental Risk Branch IV 

Environmental Fate and Effects Division (7507C)

THRU:	Elizabeth Behl, Branch Chief

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507C)

I. Summary

Boscalid (also known as nicobifen or BAS 510 F; PC Code 128008) is a
fungicide belonging to the anilid class of fungicide chemicals, also
known as carboxamide or oxathiin fungicides.  Interregional Research
Project No. 4 (IR-4) has requested registration for the use of boscalid
on leafy vegetables (crop group 4) excluding brassica.  Registrant BASF
was previously granted registration of boscalid for use on turf,
vegetables, canola, fruit and nut crops in the U.S. and Canada (May,
2003) and subsequently for soybeans, pome fruit and hops (Nov, 2003). 
Complete risk assessments for these uses can be found in the May 28,
2003 memo, “EFED Risk Assessment for Section 3 Registration of BAS 510
F (Nicobifen)” (DP Barcode D278387 and others) and the November 10,
2003 memo, “Risk Assessment for Proposed Uses of Boscalid on Soybeans,
Pome Fruit, and Hops” (DP Barcode 293435/293436).   

Boscalid is a persistent compound with low mobility in most soils. The
primary degradation pathway is aerobic soil metabolism, which proceeds
slowly and results in the formation of intermediates which are
relatively rapidly transformed into CO2 or bound soil residues. 
Boscalid is stable to hydrolysis and to photolysis on soil and in water.
 The compound is also not transformed to any significant extent in
either aerobic or anaerobic aquatic systems. 

This memo provides estimated drinking water concentrations (EDWCs) for
the Health Effects Division to use in their dietary risk assessment for
the use of boscalid on leafy vegetables.  Since the proposed new uses
have lower use rates than on the previously approved use on turf, EDWCs
for turf are reported.  The EDWCs the turf use, which reflect corrected
input parameters for the Tier 1 FIRST surface water exposure model, are
87.53 and 25.77 ppb (Appendices A and B).

A Tier I ground water assessment for boscalid has also been performed
for the turf use, based on the EFED screening model SCI-GROW. The
ground-water EDWC for boscalid on turf is 0.63 ppb. The inputs are
attached as Appendix A and results are attached as Appendix C.

II. Introduction

Use Characterization tc \l2 "Use Characterization 

Application of boscalid to the proposed use sites would be as a ground
spray, aerial spray, or through sprinkler irrigation systems. The
maximum application rates (per application), maximum seasonal rates,
application intervals, and pre-harvest intervals for the proposed new
uses are listed below in Table 1.  In addition, the use rate  for turf
is presented as well since it represents the highest use rate for
boscalid and was used in the drinking water assessment.

             	

Table 1: Proposed new label uses for boscalid

Crop Type	

Maximum Rate per Application (lbs a.i./A) and Max. Number of
Applications	

Maximum  Seasonal Application Rate (lbs a.i./A/season)	

Application Interval

(days)	

Pre-Harvest Interval

(days)



Leafy vegetables (except brassica) (Endura)	

0.396(2)	

0.79	

7	

0



Leafy vegetables (except brassica) (Pristine)	

0.395 (2)	

0.79	

7	

0



turf1 (Pristine)	

0.35 (not provided)	

2.1	

14-21	

not applicable

1 Represents highest use rate

Drinking Water Exposure

In the November 2003 risk assessment, EFED performed a drinking water
exposure assessment for the registration of the use of boscalid on
soybeans, pome fruit, and hops. The drinking water assessment detailed
in that memo used the Tier 1 surface-water model FIRST to simulate use
on turf since the turf use still represents the highest annual
application rate (2.1 lb ai/acre) for boscalid.  EFED proposes that the
EDWCs for turf be used for the leafy vegetable assessment as well since
turf application rates are still the highest, even when considering the
currently proposed uses.  EDWCs for the turf use are 87.53 and 25.77
ppb.

Appendix A							

Table A1. FIRST (v1.0) input parameter values and results for boscalid
applied to turf by ground spray.

Parameter	

Value	

Source



Application Rate (lb a.i./A)	

0.35	

Label Maximum



Number of Applications	

6	

Label Maximum



Interval between Applications (days)	

14	

Label Maximum



Organic Carbon Partitioning Coefficient (Koc)	

6551	

Swann et al., 1983



Aerobic Soil Metabolism Half-life (days)	

4012	

MRID#45405208

MRID#45405209

MRID#45643802



Wetted in?	

No	

Standard practice



Depth of Incorporation (inches)	

0	

Ground application



Method of Application	

ground spray	

Label



Percent Cropped Area	

0.87	





Solubility in Water (mg/L or ppm)	

6	





Aerobic Aquatic Metabolism Half-life (days)	

stable	

MRID#45405214



Hydrolysis Half-life @ pH 7 (days)	

stable	

MRID#45405205



Aquatic Photolysis Half-life @ pH 7 (days)	

stable	

MRID#45405206



FIRST Results (EEC for surface water drinking water sources)	

Acute Concentration (ppb):   87.5

Chronic Concentration (ppb): 25.8	



1Represents the lowest Koc for a non-sand soil. 2The aerobic soil
metabolism half-life used in the models represents the 90th percentile
of the upper confidence bound on the mean half-life for four soils.

Table A2.  SCI-GROW2 input parameter values and results for boscalid
applied to turf.

Parameter	

Value	

Source



Maximum Application Rate (lb a.i./A/application)	

0.35	

Label



Maximum Number of Applications per Year	

6	

Label



Aerobic Soil Metabolism Half-life (days)	

407.5	

MRID#45405208

MRID#45405209

MRID#45643802



Organic Carbon Partitioning Coefficient (Koc)	

8211	

Swann et al., 1983



Results (EEC for groundwater drinking water sources)	

0.5708 ug/L (ppb) or 571 ng/L (parts per trillion)	



1Represents the median value.

Appendix B-      FIRST Output

RUN No.   1 FOR boscalid         ON   Turf          * INPUT VALUES * 

   --------------------------------------------------------------------

    RATE (#/AC)   No.APPS &   SOIL  SOLUBIL  APPL TYPE  %CROPPED INCORP

     ONE(MULT)    INTERVAL    Koc   (PPM )   (%DRIFT)     AREA    (IN)

   --------------------------------------------------------------------

   .350(  1.978)   6  14     655.0    6.0   GROUND( 6.4)  87.0    .0

   FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

   --------------------------------------------------------------------

   METABOLIC  DAYS UNTIL  HYDROLYSIS   PHOTOLYSIS   METABOLIC  COMBINED

    (FIELD)  RAIN/RUNOFF  (RESERVOIR)  (RES.-EFF)   (RESER.)   (RESER.) 

   --------------------------------------------------------------------

    401.00        2          N/A       .00-     .00      .00       .00

   UNTREATED WATER CONC (MICROGRAMS/LITER (PPB))    Ver 1.0 AUG 1, 2001

   --------------------------------------------------------------------

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

   --------------------------------------------------------------------

             87.533                     25.771

Appendix C - 	  SCI-GROW Output

                          SCIGROW

                          VERSION 2.3

            ENVIRONMENTAL FATE AND EFFECTS DIVISION

                 OFFICE OF PESTICIDE PROGRAMS

             U.S. ENVIRONMENTAL PROTECTION AGENCY

                        SCREENING MODEL

                FOR AQUATIC PESTICIDE EXPOSURE

 

 SciGrow version 2.3

 chemical:Boscalid

 time is  8/27/2003   8:58:12

 -----------------------------------------------------------------------
-

  Application      Number of       Total Use    Koc      Soil Aerobic

  rate (lb/acre)  applications   (lb/acre/yr)  (ml/g)   metabolism
(days)

 -----------------------------------------------------------------------
-

      0.350           6.0           2.100      8.21E+02      407.5

 -----------------------------------------------------------------------
-

 groundwater screening cond (ppb) =   6.34E-01 

 ***********************************************************************
*

 

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