UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

PC Code: 128976

DP Barcodes: D346559

MEMORANDUM					DATE: 14 February 2008

							

	

SUBJECT:	Drinking Water Exposure Assessment for New Uses of Uniconazole
(PC Code 128976) on Ornamental Plants and Fruiting Vegetables in Shade
Houses, Lath Houses and Greenhouses

FROM:	Mark Corbin, Senior Environmental Scientist

		Environmental Risk Branch 3

		Environmental Fate and Effects Division (7507P)

THRU:	Tom Bailey, Acting Branch Chief

Environmental Risk Branch 3

		Environmental Fate and Effects Division (7507P)

TO:		Edward Scollon, Ph.D, Toxicologist

		Risk Assessment Branch 2

		Health Effects Division (7509P)

		Shaja Brothers

		Risk Integration, Minor Use, and Emergency Response Branch

Registration Division (7505P)

This memorandum transmits the Environmental Fate and Effects
Division’s (EFED) drinking water exposure assessment for uniconazole. 
Uniconazole is a plant growth regulator (PGR) used principally on
ornamentals in greenhouses.  This new use assessment is being conducted
in response to the new use request from IR-4 to add ornamentals and
fruiting vegetables in shade houses and lath houses as approved uses. 
EFED has completed a drinking water exposure assessment because shade
houses and lath houses are considered outdoor uses (Figure 1).  

Figure 1. Photograph of a shadehouse facility.

Uniconazole was assessed at seasonal maximum application rates of 0.0.09
pounds per acre (lbs/acre) for the IR-4 request for use on bedding
plants and woody ornamentals, 0.036 lbs/acre for use on bulb crops,
0.026 lbs/acre for use on azaleas, and 0.018 lbs/acre for use on
fruiting vegetables.  All of these uses are restricted to greenhouses,
shade houses, and lath houses.  Analysis of USDA Agriculture of Census
(AgCensus) data indicates that outdoor nurseries are predominantly
located in Washington, Oregon, California, and Florida although lesser
acreages are present in many states (Figure 2).

Figure 2. Outdoor Nursery Acreage (USDA AgCensus 2002)

Typically, EFED relies on an integrated approach for conducting exposure
assessments that relies on an analysis of both monitoring data and
modeling.  In the case of uniconazole, no monitoring data are available.
 Therefore, this assessment relies solely on modeling.  EFED has
conducted a screening level drinking water assessment using EFED’s
Tier I models for drinking water from groundwater (Sci-Grow) and surface
water (FIRST).  A summary of the environmental fate parameters used in
this assessment are presented in Table 1 below.  

The modeling strategy for this assessment focuses on parent uniconazole.
 The principal conazole degradate (1,2,4-triazole) has not been included
in this assessment but has been assessed separately previously
(D320682).  Other degradates identified in environmental fate studies
are
E-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazole-1-yl)-1-pentene-3-on
e (7KE),
Z-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazole-1-yl)-1-pentene-3-on
e (7KZ),
1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazole-1-yl)-pentan-3-ol
(7SA),
1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazole-1-yl)-pentan-3-one
(7SK),
1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazole-1-yl)-1,2-epoxypentan-
3-ol (7EP), and CO2. All identified degradates were detected at
percentages of applied less than 5%.  These degradates have not been
previously identified as being a concern for toxicity by HED and have
not been included in this exposure assessment.

  SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1 The appropriate FIRST input
parameters were selected from the environmental fate data submitted by
the registrant and in accordance with US EPA-OPP EFED water model
parameter selection guidelines, Guidance for Selecting Input Parameters
in Modeling the Environmental Fate and Transport of Pesticides, Version
2.3, February 28, 2002.  These parameters are summarized in Table 1 
Results of FIRST modeling are presented in Table 2.  

Table 1.  GENEEC2 Input Parameters for Uniconazole for Aquatic
Ecological Exposure Assessment

Model Parameter	Value	Comments	Source

Aerobic Soil Metabolism (t ½)	1170 days	3x single value of 390 days1
MRID 40345428

MRID 40573602

Aerobic Aquatic Degradation (t ½)	2340 days	2x aerobic soil metabolism
value due to lack of data1

	Aqueous Photolysis (t ½)	Stable	No data

	Hydrolysis 	Stable

MRID 40345427

MRID 40573601

Kd	13.0

(lowest non-sand Kd)	Koc model not appropriate	MRID 40345428

MRID 40573602

MRID 40724301

Water Solubility	8.4 mg/l

Product Chemistry

Application Efficiency	99 % for ground

default value

Percent Cropped Area (PCA) Adjustment Factor	0.87



Spray Drift Fraction	6.4 % for ground

default value

1- From “Guidance for Chemistry and Management Practice Input
Parameters for Use in Modeling the Environmental Fate and Transport of
Pesticides” dated February 28, 2002.

The results of both model runs are presented separately in Table 2.  

Table 2.  Results of FIRST modeling for uniconazole use on sweet corn,
popcorn, and field corn

Use Site	Application Rate (lbs/acre)	Number of Applications

(interval)	Peak EEC (ppb)	Annual Average EEC (ppb)

Bedding Plants & woody ornamentals	0.09

(12.8 oz/gal)	1	3.1	1.5

Bulb Crops	0.036

(5.1 oz/gal)	1	1.3	0.6

Azaleas	0.026

(3.8 oz/gal)	1	0.9	0.4

Fruiting Vegetables	0.0181

(2.6 oz/gal)	1	0.6	0.3

1 - Using fruiting vegetable rate as an example: Apply Uniconazole at
maximum of 2.6 fl oz product/gallon water.  Assuming uniconazole is
0.004 lbs a.i./gallon = 0.00003125 lbs a.i./fl oz product = 0.00008125
lb a.i./gallon water.  Apply 2 quarts of final solution to 100 square
feet bench top = 0.0000406 lb a.i./100 sq ft = 0.018 lb a.i./acre.

Finally, Sci-Grow modeling was conducted for both use scenarios to
provide an estimate of the potential loading of uniconazole to
groundwater.  Sci-Grow modeling relied on similar model inputs.  The
results are summarized in Table 3.  

Table 3.  Results of Sci-Grow modeling for uniconazole use on
ornamentals and fruiting vegetables

Use Site	Application Rate (lbs/acre)	Number of Applications

(interval)	Annual Average EEC (ppb)

Bedding Plants & woody ornamentals	0.09

(12.8 oz/gal)	1	0.076

Bulb Crops	0.036

(5.1 oz/gal)	1	0.030

Azaleas	0.026

(3.8 oz/gal)	1	0.020

Fruiting Vegetables	0.0181

(2.6 oz/gal)	1	0.015



Uniconazole is a member of the conazole class of fungicides which have
been shown to degrade to 1,2,4-triazole, which has been shown to be a
concern for human health risk assessments completed previously in OPP. 
Although not specifically identified in any of the limited number of
environmental fate studies reviewed for uniconazole, 1,2,4-triazole is
expected to be a degradation product of uniconazole.  A drinking water
exposure assessment has been previously completed for 1,2,4-triazole
(D320682) by EFED dated February 28, 2006.  This assessment included 13
registered triazole-derivative fungicides and associated uses although
uniconazole was not included.  The EEC associated with 1,2,4-triazole in
the 2006 assessment were derived from parent application rates and
conversion factors substantially higher than those associated with
uniconazole and thus are considered protective for this assessment.  The
maximum EEC for 1,2,4-triazole predicted was 41 ppb for 1 in 10 year
annual peak exposure, 11 ppb for the 1 in 10 year annual mean exposure,
and 2.7 ppb for the 1 in 10 year annual mean exposure.  The maximum
predicted EEC from Sci-Grow for acute and chronic exposure in
groundwater was 1.1 ppb.

Attachment A

MODEL OUTPUTRUN No.   1 FOR uniconazole      ON   bed plants    * INPUT
VALUES * 

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

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

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

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

   .090(   .090)   1   1      13.0    8.4   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.) 

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

   1170.00        2          N/A       .00-     .00   ******   2340.00

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

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

              3.121                      1.483

   RUN No.   2 FOR uniconazole      ON   bulb crop     * INPUT VALUES * 

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

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

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

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

   .036(   .036)   1   1      13.0    8.4   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.) 

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

   1170.00        2          N/A       .00-     .00   ******   2340.00

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

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

              1.248                       .593

   RUN No.   3 FOR uniconazole      ON   azaleas       * INPUT VALUES * 

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

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

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

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

   .026(   .026)   1   1      13.0    8.4   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.) 

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

   1170.00        2          N/A       .00-     .00   ******   2340.00

   UNTREATED WATER CONC (NANOGRAMS/LITER (PPTr))    Ver 1.0 AUG 1, 2001

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

            901.692                    428.398

   RUN No.   4 FOR uniconazole      ON   fruit veg     * INPUT VALUES * 

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

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

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

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

   .018(   .018)   1   1      13.0    8.4   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.) 

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

   1170.00        2          N/A       .00-     .00   ******   2340.00

   UNTREATED WATER CONC (NANOGRAMS/LITER (PPTr))    Ver 1.0 AUG 1, 2001

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

            624.248                    296.584

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