Document ID: EPA-HQ-OPP-2008-0258-0007
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-03-04T05:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

                                                                     
OFFICE  OF 

                                                                 
PREVENTION, PESTICIDES AND

                                                                   
TOXIC SUBSTANCES

PC Code: 268800

DP Barcode: D349254

September 3, 2008

MEMORANDUM

SUBJECT:	Drinking Water Assessment for the IR-4 Registration for the New
Uses of      Dimethomorph for New Uses on Ginseng, Lima Beans, Grapes
and Turnip     Greens for Use in Human Health Risk Assessment

TO:		Sidney Jackson, Risk Manager Reviewer

		Daniel Rosenblatt, Branch Chief

		Risk Integration Minor Use and Emergency Response Branch

		Registration Division (7505P)

AND:		William Drew, Chemist

		Registration Action Branch II

		Registration Division (7505P)

		Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

THROUGH:	Mah Shamim, Branch Chief

		Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

This memo presents the Tier I Estimated Surface Drinking Water
Concentrations and Estimated Ground Water Concentrations (EDWCs) for
Dimethomorph, calculated using the Tier I aquatic models FIRST and
SCI-GROW, respectively, for use in the human health risk assessment.  It
was found that broccoli (representative of brassica head and stem) is
still the use with the major exposure and the highest percent crop area
(PCA), and, therefore, the drinking waters assessment results do not
change from the previous ones.  The previous Drinking Waters Assessment
(DWA) still applies. An electronic copy of the previous assessment is
attached.

The Estimated Drinking Water Concentrations (EDWCs) for dimethomorph
were calculated based on a maximum application rate of 1.4 lb
a.i./A/season.  The acute drinking water concentration in surface water
is 81.1 ppb of dimethomorph, based on applications of the chemical to
broccoli.  The cancer/chronic surface drinking water concentration is
24.7 ppb (based on applications to broccoli).  The SCI-GROW generated
EDWC is 0.264 ppb of dimethomorph, which is recommended for use, both
for acute and chronic exposures.  Table I provides a summary of the Tier
I modeled drinking water concentrations.  Should there be a need for
additional refinements, the EFED can perform a Tier II aquatic
assessment, for surface waters.

Data Gaps and Uncertainties:

There are uncertainties in this assessment related to the mobility
studies.  Three studies are available, but two of them were conducted
with foreign soils.  They indicated more mobility than the study
conducted with domestic soils.  Furthermore, the metabolism studies
showed high levels of nonextractable residues.  At this time, it appears
that there are no terrestrial field dissipation studies, to confirm what
happened in the laboratory.

Table 1.  Maximum Tier I Estimated  Drinking Water Concentrations
(EDWCs) for drinking water  risk assessment based on aerial application
of dimethomorph.

DRINKING WATER SOURCE (MODEL USED) 	USE (rate modeled)	MAXIMUM ESTIMATED
DRINKING WATER CONCENTRATION (EDWC) (ppb) 

Groundwater             (SCI-GROW)	Broccoli  (1.4 lb a.i./A)	Acute and
chronic	0.264

Surface water        (FIRST)	Broccoli  (1.4 lb a.i./A)	Acute	81.1

	Broccoli  (1.4 lb a.i./A)	Chronic	      24.7

Use Characterization

Table 2 is an updated summary of all agricultural use patterns for
dimethomorph.  The highlighted uses are the proposed new ones under IR-4
petition.  The bolded and underlined use is the one modeled (also with a
special border).  The use information was obtained from the proposed
label for ACROBAT® 50WP Fungicide, and the proposed label for Forum™
Fungicide.

Table 2.  Summary use information for dimethomorph, based on ACROBAT®
50WP Fungicide label (EPA Reg. No. 241-410), containing 50.0% a.i. and
Forum™ Fungicide label (EPA Reg. No. 241-427), containing 43.1% a.i.

Use	Single App. Rate (lb a.i./A)	No. of Apps.	Seasonal App. Rate (lb
a.i./A)	Interval Between Apps. (day)	App. Method	Incorpo-ration Depth
(in)

Bulb Vegetable (Garlic, leek, onion, shallot)	0.2	5	1.0	5	Ground,
aerial, chemigation	0

Cucurbit vegetable (chayote, cantaloupe, Chinese waxgourd, citron melon,
cucumber, gherkin, edible gourd, momordica spp., muskmelon, pumpkin,
squash, winter watermelon, summer squash)	0.2	5	1.0	5	Ground, aerial,
chemigation	0

Fruiting vegetable group (except tomato) (eggplant, ground cherry,
pepino, pepper, tomatillo)	0.2	5	1.0	5	Ground, aerial, chemigation	0

Leafy brassica greens	0.2	5	1.0	7	Ground, aerial, chemigation	0

Hops	0.2	3	0.6	10	Ground, aerial, chemigation	0

Lettuce (head and leaf)	0.2	5	1.0	5	Ground, aerial, chemigation	0

Potato	0.2	5	1.0	5	Ground, aerial, chemigation	0

Taro	0.2	5	1.0	7	Ground, aerial, chemigation	0

Tobacco	0.25	4	1.0	5	Ground, aerial, chemigation	0

Tomato-Non-staked	0.2	5	1.0	5	Ground, aerial, chemigation	0

Tomato-Staked	0.2	5	1.0	5	Ground, aerial, chemigation	0

Brassica, head and stem, subgroup 5A (broccoli, Brussels sprouts,
cabbage, Chinese cabbage {napa}, Chinese mustard, cauliflower, cavalo
broccolo, kohlrabi	0.2	7	1.4	7	Ground, aerial, chemigation	0

Ginseng	0.2	5	1.0	7	Ground, chemigation	0

Lima beans	0.2	5	1.0	7	Ground, aerial, chemigation	0

Grape and Grape raising	0.2	5	1.0	7	Ground, aerial, chemigation*	0

Turnip greens	0.2	5	1.0	7	Ground, aerial, chemigation	0

*Do not apply West of the Rocky Mountains.

COPY

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

                                                                     
OFFICE  OF 

                                                                 
PREVENTION, PESTICIDES AND

                                                                   
TOXIC SUBSTANCES

PC Code: 268800

DP Barcode: D328740

April 26, 2006

MEMORANDUM

SUBJECT:		Drinking Water Assessment for the IR-4 registration for the
new uses of         dimethomorph for use on brassica head and stem
subgroup 5A.

TO:			Barbara Madden, Risk Manager Reviewer

			Daniel Rosenblatt, Risk Manager

			Registration Division (7505P)

AND:			John Redden, Team Leader

			Technical Review Branch

			Registration Division (7505P)

 

FROM:		José Luis Meléndez, Chemist

			Environmental Risk Branch V

			Environmental Fate and Effects Division	

THROUGH:		Karen Whitby, Acting Branch Chief

			Environmental Risk Branch V

			Environmental Fate and Effects Division (7507P)

This memo presents the Tier I Estimated Surface Drinking Water
Concentrations and Estimated Ground Water Concentrations (EDWCs) for
Dimethomorph, calculated using the Tier I aquatic models FIRST and
SCI-GROW, respectively, for use in the human health risk assessment.

The Estimated Drinking Water Concentrations (EDWCs) for dimethomorph
were calculated based on a maximum application rate of 1.4 lb
a.i./A/season.  The acute drinking water concentration in surface water
is 81.1 ppb of dimethomorph, based on applications of the chemical to
broccoli (representative of brassica head and stem).  The cancer/chronic
drinking water concentration is 24.7 ppb (based on applications to
broccoli, highest application rate).  The SCI-GROW generated EDWC is
0.264 ppb of dimethomorph, which is recommended for use, both for acute
and chronic exposures.  Table I provides a summary of the Tier I modeled
drinking water concentrations.  Should there be a need for additional
refinements, the EFED can perform a Tier II aquatic assessment, for
surface waters.

COPY

EXECUTIVE SUMMARY 

Dimethomorph’s full chemical name is (E,Z)
4-[3-(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)-1-oxo-2-propenyl]
morpholine, CAS# 110488-70-5, and PC code 268800.  The CAS# for the E
diatereoisomer is 113210-97-2.  The CAS# for the Z diastereoisomer is
113210-98-3.  Its’ structure has three rings, two of which are
phenyl-type rings (refer to structure in Appendix D).

Dimethomorph is a systemic fungicide which protects plants from molds,
as well as killing molds on plants and preventing their spread. It is a
cinnamic acid derivative and a member of the morpholine chemical family.
 It’s mode of action is the inhibition of sterol (ergosterol)
synthesis.  It is a mixture of two isomers (E and Z) but only the Z
isomer has fungicidal activity. It is available as a wettable powder. 
The use proposed in this IR4 (Interregional Research Project No. 4) is
brassica head stem and stem subgroup 5A.  It is to be applied as a
foliar spray.

This is a Tier I screening drinking waters assessment using Tier I
aquatic models SCI-GROW and FIRST, and maximum application rates for
dimethomorph, with minimum interval between applications.  It was found
that the worst case scenario was brassica head and steam group
(represented by broccoli) for dimethomorph, with the highest seasonal
application rate, and the highest PCA.  There were no major degradates
observed in the aerobic soil metabolism study; therefore, no degradates
were modeled in this exercise.  Should additional refinements of the
assessment are needed, the EFED can schedule a higher Tier analysis.

There are uncertainties in this assessment related to the mobility
studies.  Three studies are available, but two of them were conducted
with foreign soils.  They indicated more mobility than the study
conducted with domestic soils.  Furthermore, the metabolism studies
showed high levels of nonextractable residues.  At this time, it appears
that there are no terrestrial field dissipation studies, to confirm what
happened in the laboratory.

The proposed use involved in this action is for the following IR4
tolerance petition:  brassica head and stem, subgroup 5A.  It includes
broccoli, Chinese broccoli, Brussels sprouts, cabbage, Chinese cabbage
{napa}, Chinese mustard, cauliflower, cavalo broccoli and hohlrabi
(refer to highlighted section of Table 2 for additional details).

Table 1.  Maximum Tier I Estimated  Drinking Water Concentrations
(EDWCs) for drinking water  risk assessment based on aerial application
of dimethomorph.

DRINKING WATER SOURCE (MODEL USED) 	USE (rate modeled)	MAXIMUM ESTIMATED
DRINKING WATER CONCENTRATION (EDWC) (ppb) 

Groundwater (SCIGROW)	Broccoli  (1.4 lb a.i./A)	Acute and chronic	0.264

Surface water

(FIRST)	Broccoli  (1.4 lb a.i./A)	Acute	81.1

	Broccoli  (1.4 lb a.i./A)	Chronic	 24.7

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PROBLEM FORMULATION

This is a Tier I drinking water assessment that uses modeling to
estimate the groundwater and surface water concentrations in drinking
water source (pre-treatment), resulting from pesticide use on sites that
are highly vulnerable. This initial tier screens out chemicals with low
potential riskand allows OPP to focus resources on more refined risk
assessments for chemicals which potentially present more significant
risks. This drinking water assessment will report potential exposure
concentrations for the human health dietary risk assessment and provide
a clear and transparent description of how those concentrations were
determined. 

ANALYSIS

Use Characterization

Table 2 is a summary of all agricultural use patterns for dimethomorph. 
The highlighted use is the proposed new one under IR4 petition.  The use
information was obtained from the current label for ACROBAT® 50WP
Fungicide, and the proposed label for the same product.

Table 2.  Summary use information for dimethomorph, based on ACROBAT®
50WP Fungicide label (EPA Reg. No. 241-410), containing 50.0% a.i., and
50.0% inerts.  SEQ CHAPTER \h \r 1 

USE	SINGLE APP RATE      (lb a.i./A)	NO. OF APPS.	SEASONAL APP. RATE (lb
a.i./A)	INTERVAL BETWEEN APPS. (days)	APP. METHOD	INCORPORATION DEPTH
(inches)

Bulb Vegetable (Garlic, leek, onion, shallot)	0.2	5	1.0	5	Ground,
aerial, chemigation	0

Cucurbit vegetable (chayote, cantaloupe, Chinese waxgourd, citron melon,
cucumber, gherkin, edible gourd, momordica spp., muskmelon, pumpkin,
squash, winter watermelon, summer squash)	0.2	5	1.0	5	Ground, aerial,
chemigation	0

Fruiting vegetable group (except tomato) (eggplant, ground cherry,
pepino, pepper, tomatillo)	0.2	5	1.0	5	Ground, aerial, chemigation	0

Leafy brassica greens	0.2	5	1.0	7	Ground, aerial, chemigation	0

Hops	0.2	3	0.6	10	Ground, aerial, chemigation	0

Lettuce (head and leaf)	0.2	5	1.0	5	Ground, aerial, chemigation	0

Potato	0.2	5	1.0	5	Ground, aerial, chemigation	0

Taro	0.2	5	1.0	7	Ground, aerial, chemigation	0

Tobacco	0.25	4	1.0	5	Ground, aerial, chemigation	0

Tomato-Non-staked	0.2	5	1.0	5	Ground, aerial, chemigation	0

Tomato-Staked	0.2	5	1.0	5	Ground, aerial, chemigation	0

Brassica, head and stem, subgroup 5A (broccoli, Brussels sprouts,
cabbage, Chinese cabbage {napa}, Chinese mustard, cauliflower, cavalo
broccolo, hohlrabi	0.2	7	1.4	7	Ground, aerial, chemigation	0

ACROBAT® 50WP Fungicide is a wettable powder.  It may be applied by
ground methods, chemigation, or aerially.  There are no buffer zone
restrictions in this label.  Usually the maximum seasonal application
rate is 1.0 lb a.i./A.  For the proposed new use (IR4 petition), the
maximum seasonal application rate is 1.4 lb a.i./A.  Thorough coverage
is required to obtain maximum benefit and minimize the potential for
resistance.

The use pattern selected for drinking water modeling was the proposed
new use (brassica head and stem), and the representative crop was
broccoli.  It was selected because it involves the maximum application
rate, and hence, the maximum exposure.  Furthermore, it has the maximum
PCA (the default of 0.87).  

Fate and Transport Characterization

Table 3 provides a detailed summary of physical/chemical and
environmental fate/transport properties of dimethomorph, including
measured parameters, values, data sources, and comments.   

Table 3.  Summary of physical/chemical and environmental fate and
transport properties of dimethomorph.  SEQ CHAPTER \h \r 1 

PARAMETER	VALUES (s) (units)	SOURCE	COMMENT

  Chemical Name
4-[3-(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)-1-oxo-2-propenyl]morpholin
e

(EZ)-4-[3-(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)acryloyl] morpholine
–	CAS name

IUPAC name

  Molecular Weight	387.86	–	–

  Solubility (20ºC)	E isomer: at pH 5 13 mg/L, at pH 7 12 mg/L, at pH 9
11 mg/L

Z isomer: at pH 5 6 mg/L, at pH 7 6 mg/L, at pH 9  5 mg/L	--	–

  Melting Point	127-148ºC	Tomlin (ed.)	Z isomer169.2-170.2ºC E
isomer135.7-137.5ºC

  Bulk Density	1318 Kg/m3	Tomlin (ed.)	--

  Solubility (20-23ºC)     (g/L)	Acetone: 15 (Z), 88 (E); cyclohexanone
27(Z); dichloromethane 315 (Z); dimethylformamide 40 (Z), 272 (E);
hexane 0.02 (Z), 0.04 (E); methanol 7 (Z); toluene 7 (Z)	Tomlin (ed.)	_

  Vapor Pressure (20ºC)	E isomer 7.3 x 10-9 mmHg

Z isomer 7.5 x 10-9 mmHg	Tomlin (ed.)	–

  Henry’s Law Constant	2.06-2.13 x 10-10 atm-m3/mole	--	Estimated from
vapor pressure and water solubility.

  pKa (20ºC)	Not available	--	–

  Octanol-Water Partition   Coefficient 

  Kow, at 20º	479	Tomlin (ed.)	log KOW = 2.68

  Hydrolysis Half-life 

  (pH 4, 7, 9 [70 or        90ºC])	stable	MRID: 43917226.	Stable at all
pHs for a period of 10 weeks.

  Aquous Photolysis Half-   life 

  (pH 5)	t1/2  = 50-56 days	MRID: 43917227.	Value corresponds to 12 hour
photocycle in midsummer, uncorrected half-life with continuous
irradiation was 25-28 days.

  Soil photolysis half-    life	t1/2  = 75 days	MRID: 43917228.
Continuous irradiation with a xenon arc lamp.

  Aerobic Soil Metabolism   Half-life	t1/2  = 66 days

t1/2  = 117 days

	MRID: 43917229, 43917230.	Study yielding a half-life of 66 days was
deemed supplemental.  Both studies were performed with foreign soils
(British, German).  

  Anaerobic Soil           Metabolism

  Half-life	DT50 ~ 5-10 days

DT50 < 20 days

t½ = 26.2 and 25.7 days	MRID 43917231, 43917232, 44780201	Supplemental
studies; system was dosed with Lucerne meal when the flasks were made
anaerobic.  Other study also supplemental.

  Anaerobic Aquatic        Metabolism   

  Half-life	<1 day

<1 day

	MRID: 43917233.	Supplemental studies.

  Aerobic Aquatic          Metabolism 

  Half-life	      Not Available	NA	-- 

  Organic Carbon           Partition

  Coefficient (KOC)	566, 402, 290, 515, 377, 388, 316, 1588, 1158, 1485,
787 mL/gOC

	MRID: 46235734, 43917235, 44780202.	Various foreign soils, two soils
tested twice (once in each study).  The last four readings were
performed with domestic soils (acceptable).

  Soil Partition           Coefficient (Kd)	4.47, 11.67, 2.09, 4.94,
8.51, 2.72, 3.03, 15.7, 10.1, 19.0, 11.9

mL/g

  Terrestrial Field        Dissipation 

  Half-life	Not available	NA	-- 

The major routes of dissipation of dimethomorph appear to be metabolism,
which is moderate (66-117 days aerobic and around 26 days anaerobic). 
Another possible route of dissipation is leaching, since 5 out of the 11
Kd values were less than 5.  Based on the FAO mobility classification,
the KOC values range from moderately mobile to slightly mobile. 
Dimethomorph can reach adjacent bodies of water via spray drift or
through runoff dissolved in the water or partly adsorbed to eroding
particles depending on the properties of the soil.  Dimethomorph has
some potential to be persistent, however there are uncertainties in the
database that do not allow one to reach concrete conclusions.

One aspect of dimethomorph is that the diastereoisomer that is active is
the Z one.  In the last anaerobic soil metabolism and in the aqueous
photolysis studies, it was observed that there was conversion of the E
isomer to the Z isomer (the one that is active). This phenomenon could
have an impact in the assessments if the Z isomer is more toxic than the
E isomer.

There is also uncertainty with respect to the formation of
transformation products.  In the aerobic soil metabolism no major
transformation products were detected but large amounts of unextracted
material were observed.  In the last anaerobic soil metabolism study
(supplemental), two transformation products were observed:  p-desmethyl
dimethomorph and m-desmethyl dimethomorph.  No information on any other
transformation product could be gathered and no degradation pathway
could be traced for dimethomorph.

There is also uncertainty with respect to two mobility studies that were
deemed supplemental because they were conducted with foreign soils. 
These studies yielded smaller Kd‘s and KOC‘s than the study
conducted with domestic soils.

Dimethomorph is not likely to bioaccumulate substantially in fish or
other aquatic organisms as indicated by its low octanol/water partition
coefficient (479).

Table 4.  Summary of degradate formation from degradation of
dimethomorph

STUDY TYPE	SOURCE	DEGRADATE and MAXIMUM CONCENTRATION

p-desmethyl dimethomorph  (% applied)	m-desmethyl dimethomorph (%
applied)	DEG3 (% applied)

  Hydrolysis	  MRID: 43917226.	--	–	–

  Aqueous Photolysis	  MRID: 43917227.	--	--	–

  Soil Photolysis	  MRID: 43917228.	--	--	–

  Aerobic Soil         Metabolism	  MRID: 43917230,         43917229.	--
–	–

  Anaerobic Soil       Metabolism	MRID: 43917231,   43917232.	Observed
Observed 	--

  Aerobic Aquatic      Metabolism	Not Available	--	–	–

  Anaerobic Aquatic    Metabolism 

	MRID: 43917233.	--	–	–

  Terrestrial Field    Dissipation	Not Available	--	–	–

Drinking Water Exposure Modeling

  SEQ CHAPTER \h \r 1 

Models

SCI-GROW (Screening Concentration in Ground Water) is a regression model
used as a screening tool for ground water used as drinking water. 
SCIGROW was developed by regressing the results of Prospective Ground
Water studies against the Relative Index of Leaching Potential (RILP). 
The RILP is a function of aerobic soil metabolism and the soil-water
partition coefficient.  The output of SCI-GROW represents the
concentrations that might be expected in shallow unconfined aquifers
under sandy soils, which is representative of the ground water most
vulnerable to pesticide contamination likely to serve as a drinking
water source.  (Ref. 2)

FIRST (FQPA Index Reservoir Screening Tool) is a screening model
designed by the Environmental Fate and Effects Division (EFED, 2001a) of
the Office of Pesticide Programs to estimate the concentrations found in
drinking water from surface water sources for use in human health risk
assessment.  As such, it provides upper bound values on the
concentrations that might be found in drinking water due to the use of a
pesticide.  FIRST is a single event model (one runoff event), but can
account for spray drift from multiple applications.  Spray drift
(resulting in direct deposition of the pesticide into the reservoir) is
assumed to be 16% of the applied active ingredient for aerial
application, 6.3% for orchard air blast application, and 6.4% for other
ground spray application.  FIRST is hardwired to represent the Index
Reservoir, a standard water body used by the Office of Pesticide
Programs to assess drinking water exposure (Office of Pesticide
Programs, 2002).  It is based on a real reservoir (albeit not currently
in active use as a drinking water supply), Shipman City Lake in
Illinois, that is known to be vulnerable to pesticide contamination. The
single runoff event moves a maximum of 8% of the applied pesticide into
the reservoir.  This amount can be reduced due to degradation on the
field and the effects of binding to soil in the field.  FIRST also uses
a Percent Cropped Area (PCA) factor to adjust for the area within the
watershed that is planted to the modeled crop.  The default agricultural
PCA is 0.87.  (Ref. 3 and 4)

For volatile and semi-volatile compounds, Tier I modeling will tend to
over-estimate EDWCs because there are no parameters in SCI-GROW and
FIRST that explicitly take into account volatility (ie., no vapor
pressure input).  Therefore, in reality, more of the compound will be
volatilizing than Tier I can account for.  If drinking water levels of
concern are exceeded for over-estimated Tier I EDWCs, Tier II modeling
will be able to refine these EDWCs by including volatility
considerations.

Modeling Approach and Input Parameters

Table 5 provides the input parameter values used for modeling of
dimethomorph using SCI-GROW.  Table 6 provides the input parameter
values used for modeling of dimethomorph using FIRST.  As indicated
earlier, no degradates were included in the modeling because none
exceeded 10% of the applied in the aerobic soil metabolism study.

There were three batch equilibrium studies yielding 11 Kd‘s and
KOC‘s.  Two studies were conducted with foreign soils and yielded
lower K values than the study conducted with domestic soils.  The lowest
non-sand Kd was selected (as opposed to the KOC).   Of the two
solubilities (one for the Z and for the E isomers), the highest one was
selected.  Since there was no aerobic aquatic metabolism data and the
chemical is stable to hydrolysis, twice the input for the aerobic soil
metabolism was used.  In general, the EFED guidance for the selection of
input parameters for FIRST and SCI-GROW was used.  The new version of
FIRST V1.1.0 was utilized.

The Percent Cropped Area (PCA) used in this drinking water assessment
was 0.87.  It is the default value for “other crops” for which there
is no PCA.  It is also the maximum PCA available.

Table 5. SCI-GROW (v2.3) input parameter values for dimethomorph use on
broccoli1.

PARAMETER (units)	VALUE(S)	SOURCE	COMMENT

Maximum Application Rate (lb a.i./A)	0.2	Label ACROBAT® WP Fungicide.
–

Number of Applications per Year	7	Label ACROBAT® WP Fungicide.
Represents most-conservative scenario with the maximum number of
applications.

Organic Carbon Partition Coefficient (Koc; mL/g)	515	MRID: 43917234,
43917235, 44780202.	Median value out of 11 available.  It is noted that
there is more than a five-fold difference in the range. 

Aerobic Soil Metabolism Half-life (days)	91.5	MRID: 43917229, 43917290.
Average value of two available (117 and 66 days)

1 Parameters are selected as per Guidance for Selecting Input Parameters
in Modeling the Environmental Fate and Transport of Pesticides; Version
II, February 28, 2002.

  SEQ CHAPTER \h \r 1 Table 6. FIRST (v1.0) input parameter values for
dimethomorph use on broccoli1.

PARAMETER (units)	VALUE(S)	SOURCE	COMMENT

Application Rate (lb a.i./A)	0.2	Label ACROBAT® WP Fungicide.	–

Number of Applications	7	Label ACROBAT® WP Fungicide.

	Interval between Applications (days)	7	Label ACROBAT® WP Fungicide.

	Percent Cropped Area (decimal)	0.87	Proposed label.	National default.

Soil Partition Coefficient [Kd; (mL/g) or KOC (mL/gOC)]	3.03	MRID:
43917234, 43917235, 44780202.	Represents the lowest non-sand Kd value
among eleven values ranging from 2.09 to 19.0 mL/g. 

Aerobic Soil Metabolism Half-life (days)	147	MRID: 43917229, 43917230.
Represents the 90th percentile of the upper confidence bound on the mean
of two half-life values:  117 and 66 days; mean 91.5 days, std. dev,
25.5

Wetted in?	No	Label ACROBAT® WP Fungicide.	–

Depth of Incorporation (inches)	0	Label ACROBAT® WP Fungicide.	–

Method of Application	Aerial spray	Label ACROBAT® WP Fungicide.	–

Solubility in Water @ 20 OC, unbuffered (mg/L or ppm)	12	_	At pH 7 the
solubility of the Z isomer is 12 mg/L and the E isomer is 6 mg/L; the
maximum value was used.

Aerobic Aquatic Metabolism Half-life (days)	294	     MRID:      
43917229,     43917230	No aerobic aquatic metabolism data are available
and the pesticide is hydrolytically stable.  2X the aerobic soil
metabolism half-life input value is used.

Hydrolysis Half-life @ pH 7 (days)	0	MRID: 43917226.	Stable. 

Aquatic Photolysis Half-life  @ pH 7 (days)	56	MRID: 43917227.	–

1 Parameters are selected as per Guidance for Selecting Input Parameters
in Modeling the Environmental Fate and Transport of Pesticides; Version
II, February 28, 2002

Modeling Result

Table 7.  Maximum Tier I Estimated Drinking Water Concentrations (EDWCs)
for drinking water risk assessment based on aerial application of
dimethomorph.

DRINKING WATER SOURCE (MODEL USED) 	USE (rate modeled)	MAXIMUM ESTIMATED
DRINKING WATER CONCENTRATION  (EDWC)  ( ppb) 

Groundwater (SCIGROW)	Broccoli (1.4 lb a.i./A)	Acute and Chronic	0.264

Surface water  (FIRST)	Broccoli (1.4 lb a.i./A)	Acute	81.1

	Broccoli (1.4 lb a.i./A)	Chronic	            24.7

SCI-GROW concentration (ppb) represents the groundwater concentration
that might be expected in shallow unconfined aquifers under sandy soils.
Output is used for both acute and chronic endpoints.

FIRST concentrations (ppb) represent untreated surface water
concentrations. 

The peak day concentration (over 30 years) is used for acute endpoints
and the annual average concentration (over 30 years) is used for chronic
endpoints. 

The estimated concentrations provided in this assessment are
conservative estimates of concentrations in drinking water.  If dietary
risks require refinement, higher tiered crop-specific and
location-specific models and modeling scenarios can be utilized.

Monitoring Data

Monitoring data usually provide different kinds of information than
modeling (e.g., monitoring reflects current use pattern, underestimates
frequency of occurrence, often misses peaks, inputs cannot be adjusted
as modeled ones can, usually done for purposes other than characterizing
exposure from a particular pesticide), and, consequently, tend to
complement the modeling rather than refine it.  In general, a useful
interpretation of monitoring values requires in-depth assessment of the
data, which is beyond the scope of a Tier I assessment.  

Drinking Water Treatment

There are no data available on the effects of water treatment on the
possible increasing dissipation and/or the transformation into products
that may be less or more toxic than the parent. (Ref. 6) 

CONCLUSIONS 

In this assessment it has been assumed that the reported value is the
total dimethomorph (Z + E isomers).  The results yielded an acute
estimated surface water concentration of 81.1 ppb and a cancer/chronic
drinking water concentration of 24.7 ppb.  The groundwater EDWC,
suitable for acute and chronic exposure is 0.264 ppb.

Several uncertainties surround the environmental fate database utilized
in this assessment.  Several of the studies were deemed supplemental and
discrepancies were observed as described earlier in the summary of the
environmental fate.

APPENDIX A.  References

Policy Establishing Current Versions of Exposure Models and
Responsibility for Model Maintenance (11/06/2002)

SCIGROW: Users Manual (11/01/2001, revised 08/23/2002)

FIRST Users Manual (08/01/2001)

FIRST: A Screening Model to Estimate Pesticide Concentrations in
Drinking Water (05/01/2001)

Guidance for Selecting Input Parameters in Modeling the Environmental
Fate and Transport of Pesticides, Version II (02/28/2002) 

  SEQ CHAPTER \h \r 1 6	The Incorporation of Water Treatment Effects on
Pesticide Removal and Transformations in Food Quality Protection Act
(FQPA) Drinking Water Assessments  (10/25/2001)

Tomlin, CDS (ed.) The Pesticide Manual-World Compendium, 11th edition,
British Crop Protection Council, Surrey, England 1997, p. 416

Food and Agriculture Organization of the United Nations.  FAO PESTICIDE
DISPOSAL SERIES 8.  Assessing Soil Contamination: A Reference Manual. 
Appendix 2.  Parameters of pesticides that influence processes in the
soil.  Editorial Group, FAO Information Division: Rome, 2000 [  
HYPERLINK "http://www.fao.org/DOCREP/003/X2570E00.htm" 
http://www.fao.org/DOCREP/003/X2570E00.htm  ]

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:Dimethomorph

 time is  4/19/2006  11:47:19

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

  Application      Number of       Total Use    Koc      Soil Aerobic

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

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

      0.200           7.0           1.400      5.15E+02       91.5

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

 groundwater screening cond (ppb) =   2.64E-01 

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

 

Appendix C.  FIRST Output File

   RUN No.   1 FOR Dimetomorph      ON   Broccoli      * INPUT VALUES * 

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

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

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

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

   .200(  1.271)   7   7       3.0   12.0   AERIAL(16.0)  87.0      .0

   FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

   METABOLIC  DAYS UNTIL  HYDROLYSIS   PHOTOLYSIS   METABOLIC  COMBINED

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

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

    147.00        2          N/A     56.00- 6944.00   294.00    282.06

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

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

             81.144                     24.736

Appendix D.  Molecular Structure of Dimethomorph

 PAGE   

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