				

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES



  SEQ CHAPTER \h \r 1 								PC Code 	129099

				DP Barcode	D367105

Date                  August 4, 2009 

MEMORANDUM

SUBJECT:	Tier I Estimated Environmental Concentrations of Imidacloprid
for the Use in the Human Health Risk Assessment, Registration of a New
Product for Seed Treatment, Sepresto 75WS, and New Use on Bulb
Vegetables (Crop Group 3) for GAUCHO 550SC

FROM:	José L. Meléndez, Chemist

		Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)  

THROUGH:	Mah T. Shamim, Branch Chief

		Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

		

TO:		Kable Davis, Risk Manager Reviewer

		Venus Eagle, Risk Manager #1

		Insecticide-Rodenticide Branch

		Registration Division (7505P)

AND:		Jennifer R. Tyler, Risk Assessor

		Dana Vogel, Branch Chief

		Registration Action Branch I

		Health Effects Division (7509P)

This memo presents the Tier I Estimated Surface Drinking Water
Concentrations and Estimated Ground Water Concentrations (EDWCs) for
Imidacloprid, calculated using the Tier I aquatic models FIRST and
SCI-GROW, respectively, for use in the human health risk assessment.  It
was found that caneberries and citrus are still the uses with the major
exposure, with an application rate of 0.5 lb a.i./A, and the highest
percent crop area (PCA=0.87), 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 imidacloprid
were calculated based on a maximum application rate of 0.5 lb
a.i./A/season.  The acute drinking water concentration in surface water
is 36.0 ppb of imidacloprid, based on applications of the chemical to
citrus.  The cancer/chronic surface drinking water concentration is 17.2
ppb (based on applications to citrus).  The SCI-GROW generated EDWC is
2.09 ppb of imidacloprid, 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:

The environmental fate database is substantially complete.  An aerobic
aquatic metabolism (Guideline No. 835.4300) study has been required.

Table 1.  Maximum Tier I Estimated  Drinking Water Concentrations
(EDWCs) for drinking water  risk assessment based on ground application
of imidacloprid (for additional details, refer to Attachment A).

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

Groundwater             (SCI-GROW)	Citrus  (0.5 lb a.i./A)	Acute and
chronic	     2.09

Surface water        (FIRST)	Citrus  (0.5 lb a.i./A)	Acute	    36.0

	Citrus  (0.5 lb a.i./A)	Chronic	    17.2



Use Characterization

Table 2 is a summary of all agricultural use patterns for imidacloprid
in the proposed labels.  Uses were arranged according to crop groups. 
The uses shaded gray are the proposed new ones under Pesticide Amendment
for GAUCHO 550SC (new use added to the label), or Registration
Application for Sepresto 75WS (a proposed new product for seed
treatment, containing imidacloprid and clothianidin as active
ingredients).  The use information was obtained from the proposed labels
for GAUCHO® 550SC (EPA Reg. No. 264-827) and Sepresto 75WS (EPA Reg.
No. 264-XXX, Proposed New Product).

From Table 2 it is noted that of the new uses, only bulb vegetables
(Crop Group 3-07, e.g. onion & garlic) could involve the highest use
rate for a single application at 0.5 lb a.i./A, applied foliarly.  This
rate was assessed for caneberries, using FIRST, in memorandum dated
4/13/07 from R.D. Parker to J.R. Tyler and B. Madden (Attachment A). 
Therefore, a new assessment is not required.

Table 2.  Summary use information for imidacloprid, including proposed
(shaded gray) and current (not shaded) uses [labels for GAUCHO® 550SC
(EPA Reg. No. 264-827) and Sepresto 75WS (EPA Reg. No. 264-XXX,
Proposed)].

PURPOSE/ SOURCE	USE	a.i.  oz/ 1000 seed	APP. RATE max. lb a.i./
A/applic.	APP. RATE lb. a.i./     A/season	LABELED METHODS OF
APPLICATION4	COMMENTS

Sepresto 75WS	Root & Tuber veg. (CG 1)	0.00525	0.305	0.5	Seed treatment

	GAUCHO 550SC	Root veg.         (CSG 1B except sugarbeet + kava)	N/A
0.38	0.38	Seed treatment, soil, foliar

	GAUCHO 550SC	Tuberous & Corm veg.      (CSG 1C)	N/A	0.38	0.38	Seed
treatment, soil, foliar

	GAUCHO 550SC	Sugarbeet       (CA only)	N/A	0.18	0.18	Seed treatment,
soil

	Sepresto 75WS	Potato Seed pieces	N/A	0.092	0.092	Seed treatment	0.35 oz
prod/100 lb seed; 7.7 oz prod/A2

GAUCHO 550SC	Potato &     Potato Seed  Piece Treatment	NA	0.31	0.31	Seed
treatment, soil, foliar

	Sepresto 75WS	Leafy Greens veg. (CSG 4A)	0.0094	0.0256	0.5	Seed
treatment

	GAUCHO 550SC	Leafy veg.   (CSG 4A plus watercress)	N/A	0.38	0.38	Seed
treatment, soil, foliar

	Sepresto 75WS	Brassica (Cole) Leafy veg (CG 5)	0.01387	0.0387	0.5	Seed
treatment

	GAUCHO 550SC	Brassica (Cole) Leafy veg (CG 5)	N/A	0.38	0.38	Seed
treatment, soil, foliar

	Sepresto 75WS	Fruiting veg.  (CG 8)	0.00581	0.000358	0.5	Seed treatment

	GAUCHO 550SC	Fruiting veg.  (CG 8) (except pepper & okra)	N/A	0.38	0.38
Seed treatment, soil, foliar	Additional use for planthouses

	Pepper & Okra	N/A	0.5	0.5



Sepresto 75WS	Cucurbit veg. (CG 9)	0.011	0.0459	0.5	Seed treatment

	GAUCHO 550SC	Cucurbit veg. (CG 9)	N/A	0.38	0.38	Seed treatment, soil,
foliar	Addl use for planthouses

Sepresto 75WS	Bulb veg. (CG 3)	0.0024	0.06410	0.5	Seed treatment

	GAUCHO 550SC	Bulb veg.       (CG 3-07)	N/A	0.5	0.5	Seed treatment,
soil, foliar

	Sepresto 75WS	Cereal Grain (CG 15 w/o rice)	N/A	0.031	0.031	Seed
treatment	2.0 oz/100 lb seed; 2.6 oz/A1

GAUCHO 550SC	Cotton	N/A	0.33	0.5	Seed treatment, soil, foliar	Max. 6
applics. a.i./ season

GAUCHO 550SC	Peanut	N/A	0.38	0.38	Seed treatment, soil, foliar

	GAUCHO 550SC	Tobacco	N/A	NS	0.5	Soil, foliar	Max. 1.2 oz prod/ 1000
plants

GAUCHO 550SC	Greenhouse veg. (cucumber & tomato)	N/A	NA	NA3	Foliar	0.6
oz product/ 1000 plants

GAUCHO 550SC	Globe Artichoke	N/A	0.5	0.5	Seed treatment, soil, foliar

	GAUCHO 550SC	Herbs (CS 19A)	N/A	0.38	0.38	Seed treatment, soil, foliar

	GAUCHO 550SC	Leafy Petiole veg. (CSG 4B)	N/A	0.38	0.38	Seed treatment,
soil, foliar

	GAUCHO 550SC	Legume veg.  (CG 6 except   dry soybean	N/A	0.38	0.38	Seed
treatment, soil, foliar

	GAUCHO 550SC	Strawberry	N/A	0.5	0.5	Soil, foliar	Do not use both app.
methods in the same season.

	Use Post-Harvest	N/A	0.38	0.38	Soil, foliar

	NA = Not Available; N/A = Not Applicable; NS = Not Specified; For
GAUCHO 550SC, seed treatment is in the field at planting or shortly
thereafter.

1. Seeding rate 131 lb seeds/A for wheat (representative crop); Source: 
 HYPERLINK "http://www.uky.edu/Ag/Wheat/seedrate.html" 
http://www.uky.edu/Ag/Wheat/seedrate.html  

2. Seeding rate 1600-2200 lb seeds/A 

Source:   HYPERLINK
"http://aggie-horticulture.tamu.edu/extension/vegetable/cropguides/potat
o.html" 
http://aggie-horticulture.tamu.edu/extension/vegetable/cropguides/potato
.html  

3. Greenhouse uses are not assessed by EFED.

4. General instructions for GAUCHO 550SC:  Aerial applications of GAUCHO
550SC are not allowed.  The product may be applied with ground equipment
or via chemigation.  Applications of GAUCHO 550SC should direct product
into the seed or root zone of crop.  Broadcast foliar applications are
only recommended to seedling flats or trays, or where product is
intended to be washed from foliage to soil prior to drying on foliage.

5. Carrots, representative crop, source for approximate seeding rate:  
HYPERLINK "http://pmep.cce.cornell.edu/piap/carrot96/agpractices.html" 
http://pmep.cce.cornell.edu/piap/carrot96/agpractices.html  - and  
HYPERLINK
"http://aggie-horticulture.tamu.edu/extension/vegetable/cropguides/carro
t.html" 
http://aggie-horticulture.tamu.edu/extension/vegetable/cropguides/carrot
.html  (23000 seeds/oz and 2-2.5 lb seeds/A => 920,000 seeds/A; app rate
for carrots 0.00525 oz/1000 seeds  => 0.30 lb a.i./A)

6. Lettuce, representative crop, source of approximate seeding rate:  
HYPERLINK "http://www.ipmcenters.org/cropprofiles/CP_form.cfm" 
http://www.ipmcenters.org/cropprofiles/CP_form.cfm     (ultimately,
43000 plants/A => 0.025 lb a.i./A

7. Same source as above (6).  In CA about 44,000 plants cabbage /A =>
0.0038 lb a.i./A

8. Same source as above (6):  In FL, maximum plant density of tomatoes
is around 4,840/A; for tomatoes, the max. application rate is 0.00116 oz
a.i./1000 seed => 0.00035 lb a.i./A (note, transplants are not
considered)

9. Same source as above (6), in FL, cucumbers maximum plant population
is 21,780/A => 0.015 lb a.i./A

10. Onions, representative crop, source for approximate seeding rate:  
HYPERLINK "http://www.ag.ndsu.edu/pubs/alt-ag/onions.htm" 
http://www.ag.ndsu.edu/pubs/alt-ag/onions.htm    (8000 seeds/oz and 2-4
lb/A => 512000 seeds/A; app. rate for onions 0.0020 oz a.i/1000 seeds.
=> 0.064 lb a.i./A)



	

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