UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

							     

								   PC Code: 128008								         	    DP Barcode: D336183,
D341459

Date: August 10, 2007

MEMORANDUM	

SUBJECT:	Drinking Water Assessment for the IR-4 Petition for the Use of
Boscalid on Tropical Fruits and Fresh Herbs, and a Proposed New Use on
Cotton

TO:		Shaja Brothers, Risk Manager

		Minor Use Team, Registration Division (7505P)

		Bryant Crowe, Product Manager

		Fungicide Branch, Registration Division (7507P)

		Christina Swartz, Branch Chief

		Health Effects Division (7509P)

FROM:	Cheryl Sutton, Ph.D., Environmental Scientist

		Environmental Risk Branch IV

		Environmental Fate and Effects Division (7507P)

REVIEWED

BY:		Marietta Echeverria, RAPL

		Environmental Risk Branch IV

		Environmental Fate and Effects Division (7507P)

APPROVED

BY:		Elizabeth Behl, Branch Chief

		Environmental Risk Branch IV

		Environmental Fate and Effects Division (7507P)

The Environmental Fate and Effects Division (EFED) has completed a
drinking water assessment for the Inter-Region 4 (IR-4) petition for use
of boscalid on tropical fruits, and fresh herbs and the proposed new use
on cotton.  The 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) and leaf vegetables (excluding brassica; 2005). 
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); the November 10, 2003
memo, “Risk Assessment for Proposed Uses of Boscalid on Soybeans, Pome
Fruit, and Hops” (DP Barcode 293435/293436); and the May 5, 2005 memo
“Drinking Water Memo for Proposed Uses of Boscalid on Leafy
Vegetables” (DP Barcode 313814).   

Application rates for the proposed new uses are presented below in Table
1 along with information on the maximum use rate (for turf) among all
registered uses to date.

Table 1.  Application rates for the proposed new uses of boscalid and
the maximum use rate for turf.

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)

Tropical fruits and Fresh Herbs	0.29 (2)	0.58	7	0

Cotton (foliar)	0.39 (2)	0.79	7-14	30

Turf (Pristine, Reg. # 7969-198?)	0.35 (6)	2.1	14-21	not applicable



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 tropical fruits, herbs and cotton.  Since the
proposed new uses have lower total maximum use rates than on the
previously approved use on turf, the EDWCs for turf still represent the
maximum exposures and are recommended for use in HED’s risk
assessment.  The values reported here differ slightly from those
reported previously, however, as a percentage crop area (PCA) factor was
not used with turf, as is consistent with EFED’s policy for
non-agricultural crop uses.  The new values of 100.6 ppb (acute) and
29.6 ppb (chronic) are slightly higher than the previously reported
respective values of 87.5 ppb and 25.8 ppb.

Although the single application rate for cotton exceeds the single
application rate for turf, and the application interval for cotton is
shorter, additional modeling (not presented here) indicated that EDWCs
from cotton use are well below (>11X) those determined for turf for both
acute and chronic exposure.  This is in part due to the crop-specific
percent cropped area (PCA) for cotton which is 0.20.

The Estimated Drinking Water Concentrations (EDWC) for boscalid in
surface water and groundwater were calculated using the screening model
FIRST (FQPA Index Reservoir Screening Tool; v.1.1.0; dated 12/12/2005)
and the regression model SCI-GROW (Screening Concentration in Ground
Water, v.2.3; dated 7/29/2003), respectively.    The acute and chronic
surface water EDWCs and groundwater EDWCs determined for the turf use
are presented in Table 2.  The model inputs are presented in Tables 3
and 4.  Output files are presented in Appendices A and B.

Table 2.  Maximum Tier 1 Estimated Drinking Water Concentrations for
boscalid in groundwater and surface water based on turf use at the
maximum rate of 2.1 lb ai/A/year.  

Drinking Water Source (Model Used)	Use/Rate Modeled (lb ai/A)	Maximum
Estimated Drinking Water Concentration (EDWC; ppb)

Groundwater

(SCI-GROW2)	Ground spray/0.35 x 6 applications; annual total of 2.1 
Acute and Chronic	0.63

Surface Water (FIRST)	Ground spray/0.35 x 6 applications; annual total
of 2.1	Acute	100.6

	Ground spray/0.35 x 6 applications; annual total of 2.1 	Chronic	29.6



Table 3.  Input values used for boscalid Tier I surface water modeling
with FIRST.



Depth of Incorporation (inches)	0	Input parameter guidance.	Ground
application 

Method of Application	ground spray	Label	

Solubility in Water (mg/L or ppm)	6	Physical/chemical property data.	

Aerobic Aquatic Metabolism Half-life (days)	stable	MRID 45405214	

Hydrolysis Half-life (days)	stable	MRID 45405205	

Aquatic Photolysis Half-life  @ pH 7 (days)	stable	MRID 45405206	



Table 4.  Input values used for boscalid Tier I groundwater modeling
with SCI-GROW2.

 

Maximum No. of Applications/Year	6	Label	

Appendix A  -  FIRST OUTPUT FILE

									

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

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

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

   UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

            100.613                     29.622

Appendix B  -  SCI-GROW OUTPUT FILE

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 

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

 PAGE   

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OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

