  SEQ CHAPTER \h \r 1 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

		WASHINGTON, D.C. 20460

 					                                               OFFICE OF	         
     

PREVENTION, PESTICIDES

             AND TOXIC SUBSTANCES	

PC Code: 099050

DP BARCODE: 303582 

MEMORANDUM					June 21, 2005

SUBJECT:	Tier I Drinking Water Exposure Assessment for Acetamiprid on
Cucurbit, Stone Fruit, and Tree Nut Crop Groups.

TO:		Akiva Abramovitch, Risk Manager

		Registration Division (7505C)

		

		Kim Kosick

		Health Effects Division (7509C)	

FROM:	Greg Orrick, EPS

		ERB4/EFED (7507C)

THRU:	Betsy Behl, Chief

		ERB4/EFED (7507C)

	This memo provides Tier I estimated drinking water concentrations
(EDWCs) of acetamiprid in surface water and in groundwater in support of
human health risk assessment.  EDWC values are based on the current
acetamiprid use patterns of maximum application rate, citrus fruit and
tree nut, which represent or exceed application rates proposed for
cucurbit, stone fruit, and tree nut use patterns.  Table 1 lists the
EDWC values.  The acute and chronic surface water EDWCs were calculated
with the screening mechanistic model FIRST v1.0 (Aug. 1, 2001).  The
groundwater EDWC used for both acute and chronic risk assessment was
generated with the screening regression model SCI-GROW v2.3 (Jul. 29,
2003).

Table 1.  Tier I EDWCs in surface water and groundwater based on maximum
use patterns for acetamiprid.

Drinking Water Source	Maximum Use Pattern	Exposure	EDWC

Surface water	Citrus fruit	Acute	20.1     ppb



Chronic	  4.9     ppb

Groundwater	Tree nut	Acute & Chronic	  1.6     ppt

	

	Concentrations of degradates of acetamiprid are not estimated, as the
Health Effects Division has not found any degradates to be of toxic
concern  (personal communication, Jun. 21, 2005).  Monitoring data of
acetamiprid are not available.  If the conservative EDWCs in this memo
result in dietary risk exceedances, contact Greg Orrick (703-305-6140)
of Environmental Risk Branch IV to request a refined Tier II risk
assessment.

	For surface water assessment, the maximum application rate for citrus
fruit was used, which represents the highest label rate (i.e., 0.25 lb
a.i./A, applied twice at 7-day intervals) for a single application to
any crop.  Note that while the highest label rate for a seasonal
application to citrus fruits is 0.55 lb a.i./A, the modeled application
rate is equal to only 0.50 lb a.i./A due to limitations imposed by the
indivisibility of 0.55 by 0.25 upon both application and modeling. 
Input parameter values modeled in FIRST are listed in Table 2.  The
FIRST input/output file is presented in Attachment 1.

Table 2.  FIRST input parameter values for acetamiprid applied to citrus
fruit by aerial spray.

Input Parameter	Value	Justification	Quality1	MRID

Application rate (lb a.i./A)	0.25	Label	N/A	N/A

Number of applications	2	Label	N/A	N/A

Application interval (days)	7	Label	N/A	N/A

Percent cropped area	0.87	Default	N/A	N/A

KOC (mL/g)	164	Represents the lowest KOC for a non-sand soil.	Good
44651883

Aerobic soil metabolism half-life (days)	4.99	Represents the 90th
percentile of the upper confidence bound on the mean non-linearly
regressed aerobic soil metabolism half-life for four soils.	Good
44651879 44651881

Wetted in?	No	Label	N/A	N/A

Application method	Aerial spray	Label	N/A	N/A

Solubility in water (ppm)	4250	Product chemistry study	Very good
44651811

Aerobic aquatic metabolism

half-life (days)	135	Represents the 45-day half-life from a single study
multiplied by 3 to account for uncertainty.	Fair	44988513

Aqueous photolysis half-life at pH 7 (days)	34	Represents the longest
half-life from a single study.	Fair	44988509

1.  Quality descriptors reflect parameter value reproducibility and the
quality and abundance of the studies used to generate them.

	For groundwater assessment, the maximum application rate for tree nut
was used, which represents the highest label rate (i.e., 0.72 lb
a.i./A/season, applied in four applications of 0.18 lb a.i./A) for a
seasonal application on any crop.  Input parameter values modeled in
SCI-GROW are presented in Table 3.  The SCI-GROW input/output file is
located in Attachment 2.

Table 3.  SCI-GROW input parameter values for acetamiprid applied to
tree nut.

Input Parameter	Value	Justification	Quality1	MRID

Application rate (lb a.i./A)	0.18	Label	N/A	N/A

Maximum number of applications per year	4	Label	N/A	N/A

Organic carbon partitioning coefficient (KOC; mL/g)	251	Represents the
median KOC for four soils and one sediment.	Good	44651883

Aerobic soil metabolism half-life (days)	3.16	Represents the median
value of four aerobic soil metabolism half-lives generated by non-linear
regression.	Good	44651879 44651881

1.  Quality descriptors reflect parameter value reproducibility and the
quality and abundance of the studies used to generate them.ATTACHMENT
1:   FIRST Input/Output File (Jun. 20, 2005 13:18)

   RUN No.   1 FOR Acetamiprid      ON   Citrus        * INPUT VALUES *

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

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

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

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

   .250(   .345)        2       7          164.0   4250.0       
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.) 

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

      4.99               2                       N/A                    
34.00- 4216.00   135.00                130.81

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

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

                      20.067                                   4.901

 

ATTACHMENT 2:   SCI-GROW Input/Output File (Jun. 20, 2005 13:29) 

 

SciGrow version 2.3

chemical:Acetamiprid

time is  6/20/2005  13:29:12

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

  Application      Number of       Total Use     Koc      Soil Aerobic

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

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

      0.180                  4.0                0.720       2.51E+02    
  3.2

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

 groundwater screening cond (ppb) =   1.61E-03 

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