Document ID: EPA-HQ-OPP-2008-0556-0009
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-08-03T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

	

	

OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

MEMORANDUM

										PC Code: 129131

										DP Barcode:  354306

SUBJECT:	Tier 1 Drinking Water Assessment for Fenpyroximate Use on
Tomato, Pepper, Eggplant, Okra, Cantaloupe, and Greenhouse Cucumbers.

FROM:	Wm. J. Shaughnessy, Ph.D.

			Environmental Risk Branch II

			Environmental Fate and Effects Division

TO:		Daniel Rosenblatt, Chief

			RIMUERB

			Registration Division

THROUGH:	Tom Bailey, Ph.D, Chief

			Environmental Risk Branch II

			Environmental Fate and Effects Division

DATE:	November 3, 2008

	The attachment to this memorandum presents the results of a Tier 1
(screening level) drinking water assessment on the use of the contact
miticide fenpyroximate (PC# 129131), and its end-use products FUJIMITE®
5EC and AKARI® 5SC, on tomato, pepper, eggplant, okra, cantaloupe, and
greenhouse cucumber.  The pesticide was registered by the EPA for use on
cotton, grapes, and pome fruit in 2004.  It demonstrates activity
against phytophageous mites of the Tetranychidae, Eriophydae, and
Tarsonemidae families (Order Acari), as well as Homopteran pests such as
Leaf hoppers (Cicadellidae), and mealybugs (Pseudococcidae).  Currently,
the EPA has approved the use of fenpyroximate in ground applications
west of the Mississippi.  Aerial application of fenpyroximate is limited
to use on cotton.

	Questions related to this assessment can be directed to Dr. Tom Bailey
(703) 305-6666   HYPERLINK "mailto:@epa.gov"  (bailey.tom@epa.gov)  or
Dr. Wm. Shaughnessy, (703) 305-6155   HYPERLINK
"(shaughnessy.william@epa.gov)"  (shaughnessy.william@epa.gov) .

Attachment: As stated

Fenpyroximate Use on Tomato, Pepper, Eggplant, Okra, Cantaloupe, and
Greenhouse Cucumbers

Tier 1 Drinking Water Assessment

October 31, 2008

EXECUTIVE SUMMARY

Fenpyroximate [CAS No. 111812-58-9] is a contact miticide formulated as
the emulsifiable concentrate FujiMite® 5% EC, and as the suspension
concentrate Akari® 5% SC.  Since the use of Akari® 5% SC is limited to
indoor environments, exposures to surface and groundwater drinking water
sources are not expected, and therefore, EFED does not assess the
potential risk from this use.

FujiMite® 5% EC is being proposed for use on tomato, pepper, eggplant
(fruiting vegetable subgroup 8), okra, and cantaloupe (subgroup 9A). 
The proposed label specifies either ground or air blast application as a
foliar spray in a minimum of 20 gallons per acre.  The pesticide can be
applied no more than twice per growing season with a total use rate not
to exceed 0.2 lb. a.i./acre.  Other language in the proposed label
specifies that the pesticide should not be applied within one day of
harvest and that it should not be applied through any type of irrigation
system.

Fenpyroximate belongs to the family of pyrazoles, and its mode of action
is to interfere with mitochondrial electron transport.  Fenpyroximate
targets specifically the proton-translocation in NADH:ubiquinone
oxidoreductase enzyme blocking ubiquinone reduction.  This mode of
action blocks cell respiration causing the target pest to lose motor
control and collapse.

The pesticide was registered by the EPA for use on cotton, grapes, and
pome fruit in 2004.  It demonstrates activity against phytophageous
mites of the Tetranychidae, Eriophydae, and Tarsonemidae families (Order
Acari), as well as Homopteran pests such as Leaf hoppers (Cicadellidae),
and mealybugs (Pseudococcidae).  Currently, the EPA has approved the use
of fenpyroximate in ground applications west of the Mississippi.  Aerial
application of fenpyroximate is limited to use on cotton without regard
for location.  

The FIRST and SciGrow models were used to conduct the Tier 1 surface and
ground drinking water assessments.  For the proposed label use rates,
the FIRST model predicted raw surface drinking water acute exposure
concentrations ranging from 1.41 to 8.74 ppb and chronic exposure
concentrations ranging from 0.04 to 0.51 ppb.  The SciGrow model
predicted an acute and chronic groundwater exposure concentration range
of 0.001 to 0.033 ppb.

PROBLEM FORMULATION

This is a Tier I drinking water assessment that uses modeling and
available monitoring data to estimate the ground water and surface water
concentrations of the miticide fenpyroximate in drinking water source
water (pre-treatment) resulting from the use of the miticide on sites
that are highly vulnerable.  This initial tier screens out chemicals
with low potential risk and provides estimated exposure concentrations
for the human health dietary risk assessment.

ANALYSIS

Use Characterization

Fenpyroximate and its end-product FujiMite® 5% EC is being proposed for
use on tomato, pepper, eggplant (fruiting vegetable subgroup 8), okra,
and cantaloupe (subgroup 9A).  The proposed label specifies either
ground or air blast application as a foliar spray in a minimum of 20
gallons per acre.  The pesticide can be applied no more than twice per
growing season with a total use rate not to exceed 0.2 lb. a.i./acre. 
Other language in the proposed label specifies that the pesticide should
not be applied within one day of harvest and that it should not be
applied through any type of irrigation system.

Fate and Transport Characterization

Figure   SEQ Figure \* ARABIC  1 : Chemical Structure of Fenpyroximate
(E-Isomer)

Figure   SEQ Figure \* ARABIC  2 : Chemical Structure of Z-Isomer (M-1)

Figure   SEQ Figure \* ARABIC  3 : Chemical Structure of Parent Acid
(M-3)

Figure 1 above provides the chemical structure for parent fenpyroximate
(tert-butyl
(E)-α-(1,3-dimethyl-5-phenoxypyrazol-4-ylmethyleneamino-oxy)-p-toluate)
.  The parent   SEQ CHAPTER \h \r 1 contains a double bond (i.e., trans)
stereochemistry.  Major degradates include an M-1 cis-isomer (Figure 2)
and the M-3 parent acid (Figure 3).  Other degradates include the M-6
(Figure 4), M-8 (Figure 5), M-11 (Figure 6), and M-16 (Figure 7).  These
degradates are fragments of the parent molecule, are assumed by EFED to
be less toxic than the parent, and therefore, estimates of their
expected environmental concentrations are not provided in this drinking
water assessment.

Figure   SEQ Figure \* ARABIC  4 : Chemical Structure of M-6

Figure   SEQ Figure \* ARABIC  5 : Chemical Structure of M-8

Figure   SEQ Figure \* ARABIC  6 : Chemical Structure of M-11

Figure   SEQ Figure \* ARABIC  7 : Chemical Structure of M-16

Data on photolysis in water show that the parent configuration can be
converted rapidly to the M-1 configuration.  Parent/M-1  SEQ CHAPTER \h
\r 1  isomerization is expected to occur and reach equilibrium rapidly
in the presence of sunlight.  The light-mediated isomerization results
in rotation around the double bond converting some of the parent to the
M-1 stereoisomer.  The chemical formula for the parent/M-1 isomers is
C24H27N3O4.    SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1 The available
physical, chemical, and environmental fate properties of fenpyroximate
parent and the M-1 degradate are listed in Table 1.  The same properties
for the parent, M-1, and M-3 (parent acid) degradates are listed in
Table 2. 

Table 1.  Lower bound input parameters for dissolved parent + M-1 

MODEL INPUT VARIABLE2	INPUT VALUE	COMMENTS

USE application rates

Tomato, Pepper, Eggplant, Okra, Cantaloupe	Kg a.i./ha

0.09	Label Directions

Maximum No. of Applications

All crops	2	Label Directions

Method of application

	Ground Boom (including air blast)	Proposed use labels

Molecular Weight (g/mol)	421.50	http://fao.org

Vapor pressure (mm Hg)	5.6 x 10-8	  HYPERLINK "http://fao.org" 
http://fao.org 

Henry’s Law Constant	2.1 x 10-6	Calculated (VP * MWT)/(760 * Sol)

Application Efficiency (Ecological Effects)	

0.99 	

Per Input Parameter Guidance

Spray Drift (Ecological Effects)	0.01	Per Input Parameter Guidance

Koc (ml/g)	38,215	MRID 44847911

Mean of 7,545, 18,600, 40,000, 40,000, 41,429, 44,000, 44,032, 50,000,
and 58,333 ml/g

Aerobic Soil Metabolic Half-life (days) parent	65	MRID  46158501

Upper 10th Confidence Bound (CB) of mean of  31 and 48 days1

Includes E and Z isomers 

Incorporation depth (cm)

	0	Assumes no incorporation (CAM=1)

Model assumes 4 cm when 0 is inputted

Solubility (mg/L)	  SEQ CHAPTER \h \r 1 0.0147 	  SEQ CHAPTER \h \r 1
MRID 44781016

Aerobic Aquatic Metabolic Half-life (days)

Kbacw in EXAMS	47

	45734202

Upper 10th CB on mean of 20 and 33 days

Parent + M1 (M3 not formed)

Anaerobic Aquatic Metabolism half-life (days)

Kbacs in EXAMS	215	MRID 45649707

Upper 10th cb on mean of 125 and 170 days

Includes Parent, M1, and M3

Photolysis Half-life (days, ppm)	0.75	MRID 44781016

Includes Parent, M1, and M3

Hydrolysis Half-life (days, ppm)

pH 5

pH 7

pH 9			

181

226

221	MRID 44847909

(the aerobic aquatic half-life was used in the modeling)

1 The 2/28/02 Input Parameter Guidance requires that if two or more
metabolism half-lives are available from submitted studies, EFED is to
take them into account by taking the upper 10th confidence bound on the
mean using the formula (mean + standard deviation * tinv0.1, 1
tailed/sqrt (# half-lives).

Table 2.  Upper bound input parameters for dissolved parent + M-1 + M-3 

MODEL INPUT VARIABLE1	INPUT VALUE	COMMENTS

USE application rates

Tomato, Pepper, Eggplant, Okra, Cantaloupe	Kg a.i./ha

0.09	Per labels

M-3 was formed at up to 15 % of applied in the aerobic soil metabolism
study and 50 % of applied in the anaerobic aquatic metabolism study

Maximum No. of Applications

All crops	2	Label Directions

Method of application	Ground Boom	Proposed use labels

Molecular Weight (g/mol)	364.5	Calculated for M-3

Vapor pressure (mm Hg)	6.4 x 10-11	Epi-Suite value for M-3

Henry(s Law Constant	3.4 x 10-12	Calculated

(VP * MWT)/(760 * Sol)

Application Efficiency (Ecological Effects)	

0.99 	

Per Input Parameter Guidance

Spray Drift (Ecological Effects)	0.01 	Per Input Parameter Guidance 

Koc (ml/g)	649	MRID 45649708

Mean of 124, 440, 641, 764, and 1,308 ml/g

Aerobic Soil Metabolic Half-life (days) parent	110	MRID  46158501

Upper 10th Confidence Bound (CB) of mean of 77 and 93 days1

Includes Parent + M-1 + M-3

Incorporation depth (cm)

All uses

	0	Assumes no incorporation (CAM=1) and application to foliage

Model assumes 4 cm incorporation when 0 is inputted

Solubility (mg/L)	  SEQ CHAPTER \h \r 1 0.025	For M-3

  SEQ CHAPTER \h \r 1 MRID 45649708

Aerobic Aquatic Metabolic Half-life (days)

Kbacw in EXAMS	47

	Upper 10th CB on mean of 20 and 33 days

Includes Parent + M-1 (M-3 not detected)

MRID 45734202

Anaerobic Aquatic Metabolism half-life (days)

Kbacs in EXAMS	215	MRID 45649707

Upper 10th CB on mean of 125 and 170 days

Parent + M-1 + M-3

Photolysis Half-life (days, ppm)	0.75	Parent + M-1 + M-3

MRID 44781016 

M-3 detected in minor quantities at few intervals 

Hydrolysis Half-life (days, ppm)

pH 5

pH 7

pH 9			

181

226

221	MRID 44847909

1The 2/28/02 Input Parameter Guidance requires that if two or more
metabolism half-lives are available from submitted studies, EFED is to
take them into account by taking the upper 10th confidence bound on the
mean using the formula (mean + standard deviation * tinv0.1, 1
tailed/sqrt (# half-lives).

Fate in the Terrestrial Environment

Fenpyroximate dissipates in the environment by reversible sorption to
soil, photo degradation in water, and by microbial metabolism.  Parent
fenpyroximate in aqueous solution forms a negatively charged acid M-3;
the acid has shown to be present in soils and in the water phase.  The
major terminal degradates in terrestrial environments include M-3 and
the non-toxic M-8 

Based on laboratory results, the dissipation process of volatility is
not expected to be particularly significant because fenpyroximate parent
has a moderately low vapor pressure 5.6 x 10-8 mm Hg), a moderate
Henry’s Law Constant (2.1 x 10-6 atm m3 mol-1), and a high log Kow
(5.0).  Minimal volatility was observed in the environmental fate
studies because of the tight sorption to soil.  Sorption to soil
increases with increasing clay and organic matter content.  Both
fenpyroximate and M-1 were observed to sorb tightly to soil and sediment
in metabolism and laboratory mobility studies.    

Parent fenpyroximate is stable to sterile hydrolysis and to soil
photolysis.  Aerobic soil metabolism half-lives range from 31-48 days
for the parent and M-1 degradate.  However, the range of 77-93 days for
combined residues was observed in studies with complete material balance
and good degradate identification; therefore, EFED will use the range of
77-93 days for calculating an aerobic soil metabolism half-life for the
parent, M-1, and M-3 combined residues.

Terrestrial field dissipation data that are consistent with laboratory
data have also been provided.  In U.S. studies, the half-lives of parent
+ M-1 + M-3 ranged from 15-43 days.  No leaching was observed in the
field dissipation studies, which is consistent with the results of
laboratory studies.

Fate in the Aquatic Environment 

Based on laboratory fate properties and proposed application methods,
EFED expects fenpyroximate (combined residues) to persist long enough to
become available for transport in runoff events to surface and
groundwater environments.  However, strong sorption to soil (Kd of
75-1365 ml/g) is expected to reduce concentrations of parent
fenpyroximate in water; transport via runoff is likely to include the
parent and M-1 isomer sorbed to sediment.  No data were generated
specifically for the M-1-isomer, but results of laboratory metabolism
indicate that sorption is similar to that of the parent based on
non-extractable residues.  Therefore, soluble and total residues of the
parent and M-1 will be reduced significantly in the water column and in
runoff water.  M-3 is less likely to be found in great amounts in
soil/sediment because both soil and M-3 are negatively charged creating
repulsion from such soils.

Fenpyroximate is stable to sterile hydrolysis and degrades slowly due to
anaerobic aquatic metabolism and aerobic aquatic metabolism with
combined residue half-lives ranging from 125-170 days and 20-33 days,
respectively.  Aqueous photolysis is expected to be negligible because
the parent and M-1 in water will tend to sorb to soil particles and not
be available for degradation.  Also, shading of surface water and
turbidity will reduce photo degradation.  M-1 and M-11 are the major
degradates of this pathway.  Aqueous residues of parent fenpyroximate
and M-1 will bind to sediment, but degradates M-3, M-6 (Figure 4), M-8
(Figure 5), M-11 (Figure 6), and M-16 (Figure 7) will be associated with
surface water instead of sediment.  M-8, M-11, and M-16 are major
terminal degradates in the aquatic environment, but for the purpose of
this risk assessment will not be included because of lower toxicity than
parent, M-1, and M-3 (most toxic).  M-3 and M-8 will also leave treated
fields by runoff into surface water.

Environmental Properties of Degradates

Solubility data for M-3 were available and other properties such as
vapor pressure were estimated using EPI-Suite.  Soil mobility data for
M-3 indicate that sorption is less than for the parent and M-1 due to
the fact that it exists as an anion in soil (which generally carries a
predominantly negative charge) leading to repulsion from the soil and
transport into water.  No specific information about the
chemical/physical properties of M-1 was submitted, but essentially, it
appears to be immobile like parent fenpyroximate.

Drinking Water Exposure Modeling 

The FIRST and SciGrow models were used to conduct the Tier 1 surface and
ground drinking water assessments.  FIRST concentrations (ppb) represent
untreated surface water concentrations.  The one-in-10-year peak day
concentration is used for acute endpoints and the one-in-10-year annual
average concentration is used for chronic endpoints.

SciGrow 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.

EFED provides both a lower bound and an upper bound estimate of aquatic
exposure using the parent + M-1 + M-3 half-lives in the modeling.  The
lower bound of exposure incorporates the properties of the parent
compound and M-1, including the vapor pressure, molecular weight, water
solubility, and sorption to soil.  The upper bound exposure includes the
properties of the M-3 metabolite.  This bracketing was conducted because
the parent + M-1 compounds were tightly sorbed to soil while the M-3 was
present in the water phase in laboratory studies.  These residues of
fenpyroximate were of concern to the Health Effects Division of OPP who
treated them as equally toxic as parent fenpyroximate because of their
intact ring structures (8/12/03 memorandum from HED).

The modeled lower bound acute and chronic surface drinking water
concentrations were estimated to be 1.41 and 0.04 ppb, respectively, for
ground applications of fenpyroximate.  The upper bound acute and chronic
surface concentrations were estimated to be 8.74 and 0.51 ppb,
respectively.  The modeled ground water concentration was estimated to
be 0.001 ppb.  Modeling results are presented in Table 3.

Table 3.  Tier I Estimated Drinking Water Concentrations (EDWCs) for
drinking water assessment based on ground applications of fenpyroximate.

DRINKING WATER SOURCE (MODEL USED)	EXPOSURE CATEGORY	ESTIMATED DRINKING
WATER CONCENTRATION (EDWC) (ppb)

Upper Bound	Lower Bound

Surface Water (FIRST)	Acute	8.74	1.41

	Chronic	0.51	0.04

Groundwater (SciGrow)	Acute and Chronic	0.033	0.001

Monitoring Data 

The US Geological Survey (USGS) National Water Quality Assessment
Program database and other online data sources was searched by EFED for
surface and groundwater monitoring data on fenpyroximate to compare
against modeled results.  No data were found.

CONCLUSIONS

Modeling Results

Surface raw drinking water concentrations estimated by the FIRST model
to range from 1.41 to 8.74 ppb for acute exposures and 0.04 to 0.51 ppb
for chronic exposures.

The SciGrow model yielded an estimated groundwater concentration for an
acute and chronic drinking water exposure ranging from 0.001 to 0.033
ppb.

Uncertainties

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