Ecological Risk Assessment for Use of Fomesafen

On

Cotton  (DP302766), Snap Beans ( DP314014) 

and Dry Beans (DP314112)

January 2006

 

Table of Contents

  TOC \t "List,1"  1.	Executive Summary	  PAGEREF _Toc125452518 \h  6 

1.1	Nature of Stressor	  PAGEREF _Toc125452519 \h  6 

1.2	Potential Risk	  PAGEREF _Toc125452520 \h  6 

1.3	Endangered Species Assessment	  PAGEREF _Toc125452521 \h  8 

2.	Problem Formulation	  PAGEREF _Toc125452522 \h  10 

2.1	Stressor Source and Distribution	  PAGEREF _Toc125452523 \h  10 

2.2	Environmental Fate Summary	  PAGEREF _Toc125452524 \h  10 

2.3	Mode of Action	  PAGEREF _Toc125452525 \h  11 

2.4	Use Characterization	  PAGEREF _Toc125452526 \h  11 

2.5	Assessment Endpoints	  PAGEREF _Toc125452527 \h  15 

2.5.1	Ecosystems Potentially at Risk	  PAGEREF _Toc125452528 \h  15 

2.5.2	Ecological Effects	  PAGEREF _Toc125452529 \h  15 

2.6	Conceptual Model	  PAGEREF _Toc125452530 \h  15 

2.7	Risk Hypotheses	  PAGEREF _Toc125452531 \h  17 

2.8	Key Uncertainties and Information Gaps	  PAGEREF _Toc125452532 \h 
17 

3.	Exposure Assessment	  PAGEREF _Toc125452533 \h  18 

3.1	Label Application Rates and Intervals	  PAGEREF _Toc125452534 \h  18


3.2 	Aquatic Exposure	  PAGEREF _Toc125452535 \h  19 

3.2.1	PRZM-EXAMS Modeling Inputs and Scenario Selection	  PAGEREF
_Toc125452536 \h  19 

3.2.2	PRZM-EXAMS Modeling Output	  PAGEREF _Toc125452537 \h  20 

3.2.3	Registrant-submitted Aquatic Exposure Modeling	  PAGEREF
_Toc125452538 \h  21 

3.2.4 	SCIGROW Modeling for Ground Water	  PAGEREF _Toc125452539 \h  22 

3.2.5	Soil Accumulation	  PAGEREF _Toc125452540 \h  23 

3.3	Bird and Mammal Exposure (TREX)	  PAGEREF _Toc125452541 \h  24 

3.3	Terrestrial Plant Exposure (TerrPlant & AgDrift)	  PAGEREF
_Toc125452542 \h  26 

3.3.1	TerrPlant	  PAGEREF _Toc125452543 \h  26 

3.3.2	AgDrift	  PAGEREF _Toc125452544 \h  26 

4.	Effects Assessment	  PAGEREF _Toc125452545 \h  28 

4.1	Aquatic Guideline Data	  PAGEREF _Toc125452546 \h  28 

4.2	Aquatic Data from ECOTOX	  PAGEREF _Toc125452547 \h  29 

4.3	Terrestrial Plant Guideline Data	  PAGEREF _Toc125452548 \h  30 

4.4	Avian and Small Mammal Guideline Data	  PAGEREF _Toc125452549 \h  31


4.5	Terrestrial Insect Data	  PAGEREF _Toc125452550 \h  32 

4.6	Terrestrial Data from ECOTOX	  PAGEREF _Toc125452551 \h  32 

4.7	Incident Database Review	  PAGEREF _Toc125452552 \h  32 



5.	Risk Estimation	  PAGEREF _Toc125452553 \h  33 

5.1	Aquatic RQ Summary	  PAGEREF _Toc125452554 \h  33 

5.2	Terrestrial RQ Summary	  PAGEREF _Toc125452555 \h  34 

5.2.1	Terrestrial Plants	  PAGEREF _Toc125452556 \h  34 

5.2.1.1	TerrPlant	  PAGEREF _Toc125452557 \h  34 

5.2.1.2	AgDrift	  PAGEREF _Toc125452558 \h  35 

5.2.2	Avian RQ Summary	  PAGEREF _Toc125452559 \h  37 

5.2.3	Small Mammal RQ Summary	  PAGEREF _Toc125452560 \h  38 

5.2.4.	Terrestrial Insects	  PAGEREF _Toc125452561 \h  39 

6.	Risk Description	  PAGEREF _Toc125452562 \h  39 

6.1	Aquatic Risk	  PAGEREF _Toc125452563 \h  39 

6.2	Terrestrial Risk	  PAGEREF _Toc125452564 \h  40 

6.2.1	Birds and Mammals	  PAGEREF _Toc125452565 \h  40 

6.2.1.1	Application Rate of 0.50 lb ai/A	  PAGEREF _Toc125452566 \h  40 

6.2.1.2	Application Rate of 0.375 lb ai/A	  PAGEREF _Toc125452567 \h  40


6.2.1.3	Application Rate of 0.2 lb ai/A (Alternative)	  PAGEREF
_Toc125452568 \h  41 

6.2.2	Plants and Insects	  PAGEREF _Toc125452569 \h  41 

6.3	Endangered Species	  PAGEREF _Toc125452570 \h  42 

6.3.1	Aquatic Endangered Species	  PAGEREF _Toc125452571 \h  42 

6.3.2	Plants	  PAGEREF _Toc125452572 \h  42 

6.3.3	Birds, Reptiles & Amphibians	  PAGEREF _Toc125452573 \h  44 

6.3.4	Mammals	  PAGEREF _Toc125452574 \h  46 

6.3.5	Probability of Inidividual Effect	  PAGEREF _Toc125452574 \h  46 

 

 

List of Tables

  TOC \t "Table1" \c  Table 1  Endangered Species Occurring in the Same
County as Proposed Crops	  PAGEREF _Toc125451716 \h  8 

Table 2  Label Application Rates and Intervals for Post-Emergent
Fomesafen Use on Snap Beans and Dry Beans1	  PAGEREF _Toc125451717 \h 
18 

Table 3  Label Application Rates and Techniques for Fomesafen Use on
Cotton1	  PAGEREF _Toc125451718 \h  18 

Table 4  Input Parameters for PRZM-EXAMS Modeling of Fomesafen on Cotton
and Soybeans	  PAGEREF _Toc125451719 \h  19 

Table 5  PRZM-EXAMS EECs for Fomesafen at 0.375 lb a.i/A1	  PAGEREF
_Toc125451720 \h  20 

Table 6  PRZM-EXAMS EECs for Fomesafen at  0.50 lb ai/A	  PAGEREF
_Toc125451721 \h  20 

Table 7 1-in-10 year Estimated Environmental Concentrations of Fomesafen
from Cotton in LA.	  PAGEREF _Toc125451722 \h  21 

Table 8 1-in-10 year Estimated Environmental Concentrations of Fomesafen
from Soybeans in NE and MS	  PAGEREF _Toc125451723 \h  21 

Table 9  1 in 10 year Estimated Environmental Concentrations for
Fomesafen from Snapbeans in WI	  PAGEREF _Toc125451724 \h  21 

Table 10  Input Parameters for SCIGROW Modeling for Fomesafen	  PAGEREF
_Toc125451725 \h  22 

Table 11  Bird Dose Estimates	  PAGEREF _Toc125451726 \h  24 

Table 12  Mammal Dose Estimates	  PAGEREF _Toc125451727 \h  25 

Table 13  Terrestrial Plant Exposure	  PAGEREF _Toc125451728 \h  26 

Table 14  Estimated Point Deposition of Fomesafen from AgDrift	

(Tier I, Ground Application, Low Boom, 90% Percentile Estimate)	 
PAGEREF _Toc125451730 \h  27 

Table 15  Estimated Point Deposition of Fomesafen from AgDrift	

(Tier I, Aerial Application, 90% Percentile Estimate)	  PAGEREF
_Toc125451732 \h  27 

Table 16  Acute Aquatic Data from Registrant-submitted Studies	  PAGEREF
_Toc125451733 \h  29 

Table 17  Chronic Aquatic Data from Registrant-submitted Studies	 
PAGEREF _Toc125451734 \h  29 

Table 18  Terrestrial Plant Guideline Data	  PAGEREF _Toc125451735 \h 
30 

Table 19  Avian and Small Mammal Guideline Data from Acute Studies	 
PAGEREF _Toc125451736 \h  31 

Table 20  Avian and Small Mammal Guideline Data from Chronic Studies	 
PAGEREF _Toc125451737 \h  31 

Table 21 Summary of Aquatic RQs	  PAGEREF _Toc125451738 \h  33 

Table 22  Terrestrial Plant Risk Quotients Based on TerrPlant	  PAGEREF
_Toc125451739 \h  35 

Table 23  Required Distance from Application to Fall Below LOC	  PAGEREF
_Toc125451740 \h  35 

Table 24  Avian RQ Summary  0.5 lb ai/A	  PAGEREF _Toc125451741 \h  37 

Table 25  Avian RQ Summary: 0.375 lb ai/A	  PAGEREF _Toc125451742 \h  37


Table 26  Avian RQ Summary  0.2 lb ai/A (alternative)	  PAGEREF
_Toc125451743 \h  37 

Table 27  Small Mammal RQ Summary:  0.50 lb ai/A	  PAGEREF _Toc125451744
\h  38 

Table 28  Small Mammal RQ Summary:  0.375lb ai/A	  PAGEREF _Toc125451745
\h  38 

Table 29 Small Mammal RQ Summary:  0.2 lb ai/A (alternative)	  PAGEREF
_Toc125451746 \h  39 

Table 30  Endangered Plants by Crop and Species	  PAGEREF _Toc125451747
\h  43 

Table 31  Endangered birds potentially at risk from fomesafen	  PAGEREF
_Toc125451748 \h  44 

Table 32  Endangered reptiles and amphibians potentially at risk from
fomesafen	  PAGEREF _Toc125451749 \h  45 

Table 33 Endangered mammals potentially at risk from fomesafen	  PAGEREF
_Toc125451750 \h  46 

 

List of Figures

Figure 1  	Conceptual Model for
Fomesafen………………………………………16

    Figure 2	Soil Accumulation of
Fomesafen………………..……………………...23

Figure 3	Aerial Application of
Fomesafen………………..……………………...36

Figure 4	Ground Application of
Fomesafen……………………………………...36	

List of Maps

	Map 1	Acres of Crops by County,
Cotton………………………………………12

Map 2	Acres of Crops by County, Snap
Beans…………………………………13

Map 3	Acres of Crops by County, Dry
Beans…..………………………………14

Appendices

Appendix A	Environmental Fate Studies

Appendix B	PRZM EXAMS Output

Appendix C	TREX Output

Appendix D	TerrPlant Output

Appendix E	Ecological Effects Data

Appendix F	EIIS Output

Appendix G	RQ Method and LOCs

Appendix H	Endangered and Threatened Species

1.	Executive Summary

This ecological risk assessment addresses the proposed use of fomesafen
(PC Code 123802) on cotton, dry beans, and snap beans.  Fomesafen is
recommended as a pre- or post-emergent herbicide on cotton and a
post-emergent herbicide on dry beans and snap beans. Application rates
and techniques are dependent on geographic regions, soil textural
classification, and application timing.  The methods of application
assessed include aerial spray (0.375 lb ai/A) and ground spray (0.50 lb
ai/A).  An alternative ground spray application rate (0.2 lb ai/A) was
also considered in the assessment. 

As expected for an herbicide, the greatest acute risk associated with
fomesafen use was for non-target terrestrial plants.  Due to the high
toxicity of the compound to terrestrial plants and proposed high
application rates, spray drift buffers will likely have a minimal impact
on reducing risk to non-target plants unless they are extremely wide
(>900 ft for aerial applications, >350 ft for ground applications). 
Another significant concern is the persistence and mobility of fomesafen
in both soil and aquatic environments.  The persistence of fomesafen in
soil is expected to prolong phytotoxic effects to non-target plants. 
Environmental fate properties are also expected to favor fomesafen
movement into ground and surface waters.  Use of these waters for
irrigation may pose a risk to non-target plant species.  

1.1	Nature of Stressor

Fomesafen is an herbicide.  It is applied as a foliar spray (both
pre-emergent and post-emergent) for control of broad-leaved weeds,
grasses, and sedges.  Mode of action is via cellular membrane
disruption.  It is highly persistent in soil (63-527 days, dependent on
soil type) resulting in a potential for accumulation in terrestrial
environments.  The label suggests not planting sensitive crops in a
fomesafen-treated field for a 3-18 month period, due to the persistence
of fomesafen in the soil. Additionally, it is highly mobile, and is
expected to leach into groundwater and be transported from the site via
runoff into surface waters.  Based on physical properties,
bioaccumulation and long-range transport are not expected to be of
concern.  It is extremely toxic to terrestrial plants, especially
dicots, but of fairly low acute toxicity to fish and wildlife.  Some
chronic reproductive effects have been noted in mammals, and may also
occur in birds. No major degradates of toxicological concern have been
identified.

1.2	Potential Risk

Terrestrial Plants

Non-target organisms most at risk from fomesafen use are terrestrial
plants near the use site(s). Disruption of plant communities could have
effects on wildlife communities near the use site.  The composition and
health of plant communities determine quantity and type of wildlife
present.  Plant communities serve both as shelter and food.  

Aerial applications are of particular concern.  Based on modeling
(AgDrift), plants at distances greater than 1000 ft away from the center
of the flight line could be affected.  This may include sensitive and
high-value plant communities such as neighboring agricultural crops,
wetlands, and riparian corridors.  The majority of reported incidents
are damage to crops, either as a result of spray drift or due to
accidental misuse.  

Effects from ground-boom applied treatments do not extend as far, but at
the proposed ground application rate (0.50 lb ai/A), point deposition
from a low boom configuration does not drop below the acute risk level
of concern until 350 ft away from the application source.  Because of
the range of these potential effects, two alternative ground application
rates (0.375 lb ai/A and 0.2 lb ai/A) were also modeled.  These two
rates were selected based on the proposed aerial application rate, and
the AgDrift estimate of herbicide deposition directly below the
application source.  Based on registrant-submitted data, these rates
appear to be efficacious against some nuisance plants (Appendix E). 
Plant acute risk RQs based on these alternative application rates drop
below the level of concern at 250 ft away from the application source
(0.375 lb ai/A) and at 60 ft away from the application source (0.2 lb
ai/A).

Terrestrial Animals

On an acute risk basis, fomesafen is practically non-toxic to birds and
mammals.  Potential risk to birds and mammals is evaluated based on the
estimated pesticide residues on food items.  No acute risk LOCs were
exceeded at any application rate.  The endangered species acute risk LOC
was exceeded for small (15g) and medium (35g) mammals consuming short
grass at the highest proposed application rate (0.50 lb ai/A), and for
small (15 g) mammals consuming short grass at the lower proposed
application rate (0.375 lb ai/A).  Some medium-sized, but no small-sized
endangered herbivorous mammals occur in counties where the proposed
crops (cotton, dry beans, and snap beans) are grown.  Reduction of the
application rate to 0.2 lb ai/A eliminates all acute risk exceedences. 
At all application rates, there are exceedences of the chronic risk LOC
for both birds and mammals.  At the highest application rate, there are
chronic exceedences for organisms consuming short grass, tall grass,
broadleaf plants and small insects (i.e., all herbivores and
insectivores).  Chronic effects noted in the mammal study included a
decrease in the number of young born live, and the number of young
surviving, thus there is a potential for decreased fecundity in wildlife
populations on or near the treated site as a result of fomesafen
application.  The guideline bird study currently available for fomesafen
establishes a chronic no-effects level, but not a lowest effects level. 
Thus, the impact of exceeding the chronic level of concern for birds
cannot be determined with any certainty.  Reduction of the application
rate to 0.2 lb ai/A decreases the exposure enough so only the birds and
mammals consuming short grass exceed the chronic LOCs.

Aquatic Plants and Animals

Fomesafen is practically non-toxic to slightly toxic to aquatic animals.
 No-effects concentrations observed in laboratory toxicity tests for the
most sensitive aquatic plants are higher than expected environmental
concentrations based on modeled uses.  No levels of concern were
exceeded for aquatic animals at any application rate. 

Chemical Properties 

Fomesafen is highly persistent and mobile in soil.  These environmental
fate properties are expected to promote year-to-year accumulation in
soil as well as off-site movement by leaching and runoff.   Because
fomesafen is spray applied, there is a potential for drift onto
non-target plants.  Prolonged phytotoxic effects on non-target plants
are expected based on the persistence of fomesafen.  EFED has no data
from which to determine how long it may be toxic, but the labels
recommend not planting sensitive crops in the use site for 3 to 18
months following treatment.

1.3	Endangered Species Assessment

As an initial screening to determine what endangered species may be
affected by proposed uses of fomesafen, EFED used LOCATES (Ver 2.9.11)
to determine what species are known to occur in counties where the
proposed crops are grown.  Table 1 shows the number of unique species
(i.e., species are counted only once, even if they are affected in
multiple counties).  Although it varies by use, some states contribute
significantly to the total number of species, especially California,
Florida, and Hawaii.  Detailed information is contained in Appendix H.

Table 1  Endangered Species Occurring in the Same County as Proposed
Crops

Taxa	Cotton	Snap Beans	Dry Beans	All Uses

Plants

Monocots	20	62	13	62

Dicots	126	546	164	565

Animals

Amphibians	12	17	10	17

Birds	27	71	28	71

Reptiles	17	29	18	29

Mammals	39	61	42	63



Direct Effects -Plants

To determine what plants may be affected would require a spatial
analysis to identify proximity of the plants to potential use sites. 
EFED does not currently have the data and tools required for this type
of analysis.  Minimizing potential spray drift zones will offer some
protection.

Direct Effects – Animals

Based on categorization of animals into the diet and size classes used
by EFED to develop risk quotients, the list of endangered species
potentially at risk from fomesafen narrowed considerably.  Based on this
categorization, no species are at acute risk.  At the highest
application rate (0.50 lb ai/A), 28 species were identified as
potentially being at risk for chronic effects. At the lower proposed
application rate (0.375 lb ai/A), 23 species were identified as
potentially being at risk for chronic effects.  At the alternative rate
(0.2 lb ai/A), only 5 species appear to be at risk for chronic effects. 
A spatial analysis would assist in evaluating the likelihood of
exposure.

Indirect Effects – Plants

Pesticide-mediated indirect effects to plants are usually the loss of an
important pollinator or dispersal species.  Given the relatively low
toxicity of fomesafen to animals in general, the likelihood of these
types of effects appears to be extremely low.  Some endangered plant
species may require the presence of other non-endangered plant species
to create a suitable habitat.  Fomesafen effects on plant habitat could
constitute an indirect effect, but without detailed information on the
plant’s life history and distribution, EFED is unable to even
qualitatively evaluate this type of effect.

Indirect Effects - Animals

The most likely indirect effect on animals is modification of habitat as
a result of damage to plants.  The habitat modification could include
reduced food supply, reduced locations for nesting or burrowing, and/or
reduced cover for predator avoidance.  EFED is currently unable to
evaluate the likelihood or magnitude of such an effect.

2.	Problem Formulation

Problem formulation provides a strategic framework for the risk
assessment.  By identifying the important components of the problem, it
focuses the assessment on the most relevant chemical properties,
exposure routes, and endpoints.

2.1	Stressor Source and Distribution

Proposed new uses for fomesafen are as a pre-plant, pre-emergence, and
post-emergence, herbicide for use on broadleaf weeds, grasses, and
sedges in snap beans, dry beans, and cotton.  Distributions of these
crops were determined based on AgCensus data.  Source of the stressor
includes application via ground and aerial sprays.  Maps showing these
distributions are shown in the Use Characterization section.  Because
fomesafen is persistent in soil (soil degradation t1/2 = 29-99 weeks at
0.50 lb ai/A application rate, (MRID 00135660)), residual in soil of the
treated field is considered in this risk assessment as a secondary
source.

2.2	Environmental Fate Summary

Major routes of fomesafen dissipation are leaching, runoff, and
microbial degradation.  Because fomesafen is persistent and mobile in
soil, it is expected to move from the application site into groundwater
and surface water.  Additionally, off-site movement of fomesafen is
expected through spray drift from aerial and ground spray.  The high
persistence of fomesafen is expected to contribute to year-to-year
accumulation in terrestrial and aquatic environments. 

Fomesafen is stable to abiotic hydrolysis.  It undergos slow
photodegradation in water

(t1/2= 49 to 289 days).  Fomesafen is persistent (t1/2=9 to 99 weeks) in
aerobic soil and aquatic environments.  However, it degrades rapidly
(t1/2< 20 days) in anaerobic environments.  The major degradation
product of fomesafen is
5-(2-chloro-(,(,(-trifluoro-p-tolyloxy)-N-methylsulphonyl-panthranilamid
e (fomesafen amine).  A minor degradation product is
5-(2-chloro-(,(,(-trifluoro-p-tolyloxy) anthranilic acid (fomesafen
amino acid).   Neither degradate has been identified as a toxicological
concern. 

Fomesafen is expected to be very mobile in soil.  Simple partitioning
coefficients range from 0.51 in loamy coarse sand to 2.45 in sandy clay
loam soil.  Regression analysis indicates fomesafen sorption is not
dependent on soil organic matter content.  Aged soil column leaching
studies indicate degradation products of fomesafen are not mobile in
soils; less than 0.06% of applied radioactivity was detected in the
leachate samples.

Field dissipation studies in NC, IL, MS, AR, AL, TX, LA, SD, MN, KY, IA
and MO indicate fomesafen is moderately persistent to persistent (t1/2=
50 to 150 days ) in surface soils under actual use conditions. 
Fomesafen was detected at depths up to 30 inches in the soil profile. 
Fomesafen amine was the only degradation product identified in field
dissipation studies.  Prospective ground water monitoring in NC
indicates fomesafen moved through the soil profile into medium and deep
ground water.  

Fomesafen has a low potential for bioaccumulation in fish tissues. 
Bioaccumulation factors for fosmesafen were 0.7 for whole fish, 0.2 for
edible tissues, and 5.2 for nonedible tissue.  Bioaccumulated residues
were depurated during a 14-day depuration period.  

2.3	Mode of Action

Fomesafen is a diphenylether.  It disrupts the cell membrane of the
plant (  HYPERLINK "http://www.syngentacroprotection-us.com" 
www.syngentacroprotection-us.com ) by penetrating into the cytoplasm and
causing formation of peroxides and free electrons (  HYPERLINK
"http://www.abcbids.org"  www.abcbids.org ). The specific mode of action
is inhibition of protoporphyrinogen oxidase (  HYPERLINK
http://www.weeds.iastate.edu)  www.weeds.iastate.edu) .  Fomesafen
generally acts quickly, and does not translocate.  It has both foliar
and soil activity.  Other herbicides in this group include aciflourfen,
lactofen, and oxyfluorfen.  

2.4	Use Characterization

Fomesafen is being proposed as a pre-plant, pre-emergence, and
post-emergence herbicide for use on broadleaf weeds, grasses, and
sedges, in snap beans, dry beans, and cotton.   Methods of application
are ground spray (0.5 lb ai/A, cotton) and aerial spray (0.375 lb ai/A,
dry beans, snap beans, and cotton).  Application is limited to once a
year, or in alternate years, depending on location.  Application rates
are regionally specific.  Maps 1, 2, and 3 show the locations of these
crops according to USDA crop data.

Cotton

Cotton is grown in the southern U.S. with the greatest concentrations in
four major areas: the eastern coastal plain (North Carolina to Alabama),
the lower Mississippi River Valley (Arkansa, Tennessee, Mississippi and
Louisiana), Texas (panhandle and hill country), and California (Central
Valley).

Dry Beans

Dry beans are grown primarily in six areas: the upper Great Plains
region (Minnesota, North Dakota), the western central Great Plains
(western Kansas and Nebraska, eastern Colorado), western New York,
central Michigan, Washington’s Yakima Basin, and the California
Central Valley.  USDA classifies dry lima beans as a separate commodity
group, and they are grown primarily in California’s Central Valley. 
For the purpose of this risk assessment, dry lima beans have been
included in the dry bean group.

Snap Beans

Snap beans are grown in a wide variety of locations, although certain
areas do appear to have greater concentrations of snap bean culture than
others. Areas of higher concentration include the eastern coastal plain
in Maryland, Delaware, and New Jersey; Michigan and Wisconsin;
Washington’s Yakima Valley, Oregon’s Willamette Valley, and the
California Central Valley.

 2.5	Assessment Endpoints

Assessment endpoints are selected based on ecosystems typically at risk
from agricultural pesticide applications.  Specific ecological effects
are evaluated based on toxicity information from guideline tests, and
focus on the general categories of survival, growth, and reproduction. 
EFED currently does not assess behavioral or biochemical endpoints.

2.5.1	Ecosystems Potentially at Risk

For typical crop applications, the ecosystem at risk is the field
itself, in terms of organisms that might be sprayed during application,
organisms affected by accumulation of fomesafen in the soil; and the
adjacent aquatic and terrestrial environments affected due to runoff,
spray drift, or groundwater contamination.  In water bodies receiving
runoff from agricultural fields, pelagic and benthic elements are
considered.  Terrestrial organisms assessed include non-target plants,
insects, amphibians, reptiles, birds, and mammals.  Because fomesafen is
an herbicide, potential affects on non-target plants have been addressed
at length.

2.5.2	Ecological Effects

Evaluation of ecological effects focuses initially on direct effects to
the groups of organisms residing in the ecosystems at risk, based on
ratios of the estimated environmental concentration (EEC) to a
designated toxicity endpoint for a surrogate test organism.  If
pre-established levels of concern (LOCs) are exceeded for direct
effects, indirect effects to endangered species (e.g. food chain,
decrease in community diversity) are evaluated based on the group of
organisms exceeding the LOC.

Direct

Direct effects evaluated are the survival, growth, and reproduction of
various taxa of organisms potentially exposed to fomesafen.  Taxonomic
groups evaluated include aquatic plants (algae and vascular), aquatic
invertebrates, aquatic vertebrates, terrestrial plants, terrestrial
invertebrates, birds, and mammals.  Both acute and chronic effects are
considered.

Indirect

When herbicides are applied, indirect effects may include a decline in
primary productivity, or change in composition of plant communities
proximate to the treated area or systems (wetlands and water bodies)
receiving runoff from the site.  If LOCs are exceeded for any taxa,
potential indirect effects to endangered species are assessed.

2.6	Conceptual Model

2.7	Risk Hypotheses

(	Fomesafen deposited on plant surfaces may affect growth, survival, or
fecundity of birds and/or small mammals ingesting the affected
vegetation.

(	Fomesafen accumulating in soil may be toxic to non-target plants.

(	Fomesafen in runoff from treated areas may kill aquatic plants,
aquatic invertebrates, or fish.

(	Fomesafen in runoff from treated areas may reduce populations of
aquatic plants, aquatic invertebrates, or fish, causing changes in the
community.

(	Fomesafen in runoff from treated areas may accumulate in sediments,
resulting in chronic impacts to the benthic community.

(	Fomesafen is expected to move from the application site by leaching
into groundwater and runoff into surface water.  Use of water resources
with fomesafen occurrence as an irrigation source water may adversely
impact non-target plants.

 2.8	Key Uncertainties and Information Gaps

(	Bioavailability of fomesafen to non-target organisms is influenced by
site characteristics.  An effort has been made to examine a variety of
sites typical of areas where it might be used.  Scenarios and input
parameters have been selected to represent conditions where fomesafen is
most bioavailable.  Overall, conditions have been selected to develop a
conservative, screening level estimate.  In some locations and under
some conditions, risk may be overestimated.

(	Fomesafen is sufficiently persistent in soil that it may cause
prolonged phytotoxic effects.  EFED has no specific data to evaluate how
long measurable toxic effects on plants may occur after initial
treatment, thus it is difficult to assess the potential effects of
chronic exposure.

(	Natural genetic variability in wild organisms may affect their
response to fomesafen, and the distribution of species sensitivity is
not well understood.  Risk may be under- or over-estimated by available
toxicity data and use of surrogate taxa.

(	At the time of the risk assessment, terrestrial and aquatic plant data
were available, but had not yet been completely through EFED’s data
evaluation process.  Provisional classification of these data is
supplemental.  Minor changes in the reported toxicological endpoints
(i.e., LC50, EC25, NOAEC) may occur following statistical analysis of
the data according the EFED’s protocols, but these changes are not
expected to affect the risk conclusions.

(	Available avian reproduction studies did not establish LOAECs, and the
NOAEC is set at the highest dose (approximately 50 ppm).  Exceedences of
the chronic LOCs for birds may or may not imply risk.

(	The locations of sensitive and/or valuable plant communities are not
available, thus effects on these communities can only be assessed in a
general, qualitative sense. 

3.	Exposure Assessment

EFED conducted the exposure assessment using standardized exposure
modeling.  The exposure was modeled separately for each proposed
application rate, and in most cases, for each proposed application
method. Two proposed application rates (0.50 lb ai/A for ground
application and 0.375 lb ai/A for aerial application) were modeled for
all routes of exposure.  An alternative application rate (0.2 lb ai/A)
was also modeled for the terrestrial exposures.  

3.1	Label Application Rates and Intervals

Fomesafen is proposed as a pre-plant, pre-emergence, and post-emergence
herbicide for use on broadleaf weeds, grasses, and sedges. The
registrant and IR-4 are petitioning to use the sodium salt of fomesafen,
formulated as REFLEX 2.5 Gallon( (EPA Reg. No. 100-993) and REFLEX 2LC
(EPA Reg. No. 10182-83) on cotton, snap beans, and dry beans.  Regional
label application rates and application intervals for dry beans and snap
beans are shown in Table 2.  Fomesafen can be applied through aerial and
ground spray at a maximum application rate of 0.375 lbs ai/A.

Table 2  Label Application Rates and Intervals for Post-Emergent
Fomesafen Use on Snap Beans and Dry Beans1

Region	States in Region	App Rate (lbs/A)	Application Interval

1	AL, AK, GA, MS, MO, NC, OK, SC, TN, TX	0.375	1 year

2	DE, KY, MD, VA, WV, IL, IN, OH, PA	0.375	2 year

3	CN, IA, ME, MA, MI, NH, NJ, NY, PA, RI, VT, WI	0.312	2 year

4	KS, MI, MN, NE, WI, ND, SD,	0.25	2 year

5	ND, SD, MN	0.170	2 year

1- REFLEX 2.5 Gallon( (EPA Reg. No. 100-993) and REFLEX 2LC (EPA Reg.
No. 10182-83)

Label restrictions for cotton are shown in Table 3. As post-emergent
herbicide, fomesafen can be applied using ground spray at a maximum
application rate of 0.5 lbs ai/A.  

Table 3  Label Application Rates and Techniques for Fomesafen Use on
Cotton1

Application Timing	Application Technique	Max App Rate (lbs/A)

Pre-emergent	Aerial or Ground Spray	0.375

Post-directed	Ground Spray	0.375

Post-emergent	Ground Spray	0.50

1- REFLEX 2.5 Gallon( (EPA Reg. No. 100-993)

3.2 	Aquatic Exposure

Tier II EFED aquatic exposure models use the linked Pesticide Root Zone
Model and Exposure Analysis Model System (PRZM-EXAMS).  PRZM uses the
chemical’s physical and environmental fate properties and the site
characteristics to predict the concentration of pesticide in runoff and
entrained sediment from the field.  EXAMS estimates the concentration of
pesticide in an edge-of-field small water-body receiving runoff from the
field.  The water-body has no outflow with a constant volume (20 million
liters), and is intended to represent an upper-end occurrence
concentration.

3.2.1	PRZM-EXAMS Modeling Inputs and Scenario Selection

The aquatic exposure assessment for fomesafen was conducted to assess
use on soybeans and cotton.  Soybeans were used a surrogate for dry
beans and snap beans, as EFED currently has no standard scenarios for
these crops.  Standard scenarios were selected to assess runoff
potential from vulnerable use sites in MS (soybean and cotton), NC
(cotton), and TX (cotton).  Input parameters for fomesafen were selected
according to EFED Input Parameter Guidance for PRZM/EXAMS1.  Input
parameters are shown in Table 4.

Table 4  Input Parameters for PRZM-EXAMS Modeling of Fomesafen on Cotton
and Soybeans

Parameter	Value	Comments	Source

Application Rate (kg a.i./ha)- Cotton	0.42	Aerial Spray	Label1

Application Rate (kg a.i./ha)- Cotton	0.56	Ground Spray	Label1

Application Rate  (kg a.i/ha)- Soybean	0.42	Aerial Spray	Label1

Molecular Weight  (grams/mole)	420

EPA 2020220

Solubility (mg/L)	1200	@pH= 7; 200c	MRID 45048207

Vapor Pressure (torr)	<7.5x10-7	@ 50oC	HSDB

Henry’s Constant (atm m3/mol) 	7.5 x10-13	Estimated	HSDB

Kd  (L/kg)	0.68	Lowest non-sand Kd	Acc No. 259413

Aerobic Soil Metabolism Half-life (days)	428.8	Upper 90th percentile of
mean2	Acc No. 071059

Acc. No. 00135660

Aerobic Aquatic Metabolism Half-life (days)	115.7 	Upper 90th percentile
of mean3	Acc. No. 72158

Anaerobic Aquatic Metabolism Half-life  (days)	Stable	Conservative
Assumption 	No Data Available

Photodegradation in Water (days)	289	@pH=7	MRID 40451101

Hydrolysis Half-life (days)	Stable	@pH=7	Acc No. 071059

1-Reflect application rates on the REFLEX 2LC, REFLEX 2.5 and REFLEX
labels

2-Calculated from half-lives of 187.6, 630, 57, 693, 349.3, 527.1, 207
days using a mean of 387.84 days and standard deviation of 242.90 days. 

3- Calculated from half-lives of  139.9, 60.9, 92.4, and 115.5 days
using a mean of 102 days and standard deviation of 33.44 days.

3.2.2	PRZM-EXAMS Modeling Output

For aerial applications (Table 5), peak 1 in 10 year estimated
environmental concentrations (EECs)  ranged from 7.5 ppb (soybeans, MS)
to 12.2 ppb (cotton, TX).   Chronic 1-in-10 year (21-day average and
60-day average) EECs ranged from 6.4 ppb (soybean, MS, 60-day average)
to 11.4 ppb (cotton, MS &TX, 21-day average).

Table 5  PRZM-EXAMS EECs for Fomesafen at 0.375 lb a.i/A1

Region	Crop	State	Peak	4 days	21 days	60 days



	(g/L (ppb)

1	Soybean	MS	7.462	7.382	7.133	6.443

1	Cotton	MS	12.102	11.964	11.411	10.115

1	Cotton	NC	9.856	9.728	9.201	8.067

1	Cotton	TX	12.201	12.045	11.437	9.973

1-Concentrations were derived for 0.375 lb ai/A using aerial
applications

Peak 1-in-10 year EECs for ground spray applications (Table 6) ranged
from 10.6 ppb (cotton, NC) to 15.1 ppb (cotton, MS).  Chronic 1 in 10
year (21-day average and 60-day average) concentrations ranged from 8.6
ppb (cotton, MS, 60-day average) to 14.2 ppb (cotton, MS, 21-day
average).

Table 6  PRZM-EXAMS EECs for Fomesafen at  0.50 lb ai/A

Region	Crop	State	Peak	4 days	21 days	60 days



	(g/L

1	Cotton	MS	15.106	14.939	14.249	12.621

1	Cotton	NC	10.609	10.471	9.905	8.680

1	Cotton	TX	14.63	14.445	13.713	11.954

1- Concentrations were derived for 0.50 lb ai/A using ground spray 

3.2.3	Registrant-submitted Aquatic Exposure Modeling

The registrant submitted Tier II PRZM/EXAMS modeling assessments for
fomesafen use on cotton and soybeans (MRID 450482-04, 450482-05,
450482-06).   The modeling scenarios used were developed to assess
fomesafen runoff from vulnerable use sites (Hydrologic D soils) with
high rainfall.  Selected scenarios represent sites in Tensas County, LA
(MRLA 131) for cotton; Leflore, MS (MRLA 131) for soybeans; and Dodge,
NE (MRLA 102B) for soybeans, and Sheboygan, WI (MRLA 95B).  Maximum
application rates were 0.31 lbs for snap beans, 0.5 lbs a.i./A for
cotton, and 0.375 lbs a.i./A for soybeans.  Only ground spray was
considered, although the labels allow aerial spray.  The sources (study
identification numbers) of environmental fate data are not reported. 
Additionally, there are no explanations for selection of the
environmental fate data in the exposure assessment.  Registrant
estimated environmental concentrations of fomesafen in the small water
bodies are shown in Tables 7, 8, and 9.

Table 7 1-in-10 year Estimated Environmental Concentrations of Fomesafen
from Cotton in LA.

Scenario ID	Application Rate	Peak

(ppb)	4-day

(ppb)	21-day

(ppb)	60-day

(ppb)	90-day

(ppb)	Annual Average

(ppb)

Cotton-1	0.25 lbs ai/A post emerg

0.25 lbs ai/A post emerg	14.96	14.85	14.35	13.43	12.61	7.70

Cotton-2	0.17 lbs ai/A pre-emerg

0.25 lbs ai/A post-emerg	13.09	12.99	12.59	12.03	11.33	7.14

Cotton-3	0.25 lbs ai/A pre-emerg

0.25 lbs ai/A pre-emerg	16.26	16.07	15.40	14.96	14.29	8.67



Table 8 1-in-10 year Estimated Environmental Concentrations of Fomesafen
from Soybeans in NE and MS

Application Rate	MLRA	Peak

(ppb)	96-hour

(ppb)	21-day

(ppb)	60-day

(ppb)	90-day

(ppb)	Annual Average

(ppb)

0.25 lbs ai/A in alternate years	NE

(102B)	6.22	6.18	6.07	5.83	5.62	3.49

0.375 lbs ai/A 

every year	MS

(131)	13.32	13.22	12.63	11.67	10.81	5.78



Table 9  1 in 10 year Estimated Environmental Concentrations for
Fomesafen from Snapbeans in WI

Application Rate	MLRA	Peak	4 days	21 days	60 days



(g/L

0.31 lbs a.i./A alternate years	95B 	5.13	5.10	4.97	4.68



3.2.4 	SCIGROW Modeling for Ground Water

Because fomesafen is mobile and persistent in soil, a screening level
groundwater assessment using SCIGROW (ver. 2.3) was conducted to
estimate the concentration of fomesafen in shallow groundwater, which
could potentially be used for crop irrigation.  Input parameters for
SCIGROW are listed in Table 10.  A groundwater monitoring study was
submitted (MRID 42247001), but the shallow groundwater wells were dry
during the study.  Fomesafen was detected in soil porewater at
concentrations of 1 g/L (at 4 months), up to 17g/L (at 1
month).  It was detected at a concentration of 1 g/L in the medium-
to deep-depth wells.

 

Table 10  Input Parameters for SCIGROW Modeling for Fomesafen 

Parameter	Value	Comments	Source

Application Rate (kg a.i./ha)- Cotton	0.56

Label1

Koc  (L/kg)	  68	Estimated2  	Acc No. 259413

Aerobic Soil Metabolism Half-life (days)	387.84	Mean3	Acc No. 071059

Acc. No. 00135660

1-Reflect maximum application rates on the REFLEX 2LC, REFLEX 2.5 and
REFLEX labels

2-Koc estimated using Kd/SOC=Koc; where Kd=0.68 and SOC=1% SOC
percentage

3-Calculated from half-lives of 187.6, 630, 57, 693, 349.3, 527.1, 207
days using a mean of 387.84 days and standard deviation of 242.90 days. 

g/L (at 4 months), up to 17g/L (at 1 month).  It was detected
at a concentration of 1 g/L in the medium- to deep-depth wells.

Because fomesafen is expected to leach to groundwater, EFED has
calculated the maximum application rate of fomesafen from two inches of
irrigation water, using the following equations. This calculation
assumes that two inches (0.167 ft) of irrigation water is required for
optimum plant growth.  The calculations are as follows:

g/L = fomesafen g/A

(fomesafen g/A)/ (106) = fomesafen grams/A*1lb/454 grams=fomesafen
lbs ai/A.

Based on two inches of irrigation and the SCIGROW estimate, the
application rate of fomesafen is estimated at 0.003 lbs ai/A.  Using the
concentrations of 1 mg/L and 17mg/L (from the groundwater study) as
outer bounds, concentrations of fomesafen in irrigation water could
range from 0.0004-0.0077 lbs ai/A.

3.2.5	Soil Accumulation

Because of the persistence of fomesafen in soil, a screening level
assessment was conducted to quantify the accumulation of fomesafen
residues in soil.  A first-order decay model (A=Aoe-kt) was used to
estimate fomesafen soil concentrations. The time period in the model (t)
was set to 730 days to represent alternate years applications.  The
upper 90th percentile of the mean half-life (t1/2=428 days; k=0.00161950
days-1) was used to represent the microbial mediated decay rate of
fomesafen in soil.  The starting concentration (A0 ) was set at the
label recommended application rate of 0.375 lbs ai/A for aerial
applications and 0.5 lbs ai/A for ground applications.  The modeling
scenario assumes that 100% of fomesafen residue is applied to the soil
as recommended for a pre-emergent application.  The model scenario also
assumes that microbial degradation is the only route of dissipation from
the application site. These assumptions are expected to exaggerate
predicted formesafen soil concentrations.

Figure 2 illustrates the fomesafen concentrations in soil reach a
plateau after approximately 10 years regardless of the application rate.
 Application rates of 0.375 lbs/A can theoretically result in a maximum 
fomesafen concentration  of  0.14 mg/kg.  Higher application rates of
0.5 lbs ai/A can theoretically result in a maximum fomesafen
concentration of 0.19 mg/kg.

  

Figure 2 - Estimate of Fomesafen Loading in the Surface Soil (0-15 cm
depth) from alternate year applications of 0.375 lbs/A (solid line) and
0.5 lbs/A (dotted line)  3.3	Bird and Mammal Exposure (TREX)

EFED estimates exposure of birds and mammals using the Terrestrial
Exposure Model (TREX).  TREX uses the Kenaga nomagram to determine
pesticide residues on several categories of food items, then calculates
the potential dose an organism might receive from ingesting contaminated
items using allometric equations.  Dose estimates in the tables 8 and 9
are based on the Kenaga upper bound dose and the assumptions that the
organism exclusively eats one type of food item and forages only in the
treated and/or overspray areas.

For birds, dose estimates for the 0.2 lb ai/A application rate range
from 0.87 mg/kg bwt (1000g frugivores, granivores, and insectivores) to
54.7 mg/kg bwt (20 g herbivores). At the 0.37 lb ai/A application rate,
estimated doses range from 1.64 (1000g frugivores, granivores, and
insectivores) to 102 (1000g fruit and pods).  Dose estimates for the
0.49 lb ai/A application rate range from 2.14 mg/kg bwt (1000g
frugivores, granivores, and insectivores) to 134 mg/kg bwt (20 g
herbivores).

Table 11  Bird Dose Estimates

Feeding Categories	Kenaga Upper Bound Dose (mg/kg bwt)

	Small

(20 g)	Medium 

(100 g)	Large

(1000 g)

0.2 lb ai/A Appllication Rate (Alternative)

Short grass	54.67	31.17	13.96

Tall grass	25.06	14.29	6.40

Broadleaf plants/small insects	30.75	17.54	7.85

Fruits/pods/seeds/large insects	3.42	1.95	0.87

0.375 lb ai/A Application Rate

Short grass	102.5	58.45	26.17

Tall grass	46.98	26.79	11.99

Broadleaf plants/small insects	57.66	32.88	14.72

Fruits/pods/seeds/large insects	6.41	3.65	1.64

0.50 lb ai/A Application Rate

Short grass	133.93	76.38	34.19

Tall grass	61.39	35.01	15.67

Broadleaf plants/small insects	75.34	42.96 	19.23

Fruits/pods/seeds/large insects	8.37	4.77	2.14



For mammals dose estimates for the 0.2 lb ai/A application rate range
from 0.10 mg/kg bwt (1000g granivore) to 45.8 mg/kg bwt (20 g short
grass). At the 0.37 lb ai/A application rate, estimated doses range from
0.19 (1000g granivore) to 85.8 (20 g short grass).  Dose estimates for
the 0.49 lb ai/A application rate range from 0.25 mg/kg bwt (1000g
granivore) to 112 mg/kg bwt (20 g short grass).

Table 12  Mammal Dose Estimates

Feeding Categories	Kenaga Upper Bound Dose (mg/kg bwt)

	Small

(15 g)	Medium 

(35 g)	Large

(1000 g)

0.2 lb ai/A Appllication Rate (Alternative)

Herbivores/Insectivores



	Short grass	45.76	31.63	7.33

Tall grass	20.98	14.50	3.36

Broadleaf plants/small insects	25.74	17.79	4.13

Fruits/pods/seeds/large insects	2.86	1.98	0.46

Granivores

Fruits/pods/seeds/large insects	0.64	0.44	0.10

0.375 lb ai/A Application Rate

Herbivores/Insectivores



	Short grass	85.81	59.30	13.75

Tall grass	39.33	27.18	6.30

Broadleaf plants/small insects	48.27	33.36	7.73

Fruits/pods/seeds/large insects	5.36	3.71	0.86

Granivores

Fruits/pods/seeds/large insects	1.19	0.82	0.19

0.50 lb ai/A Application Rate

Herbivores/Insectivores



	Short grass	112.12	77.49	17.97

Tall grass	51.39	35.52	8.23

Broadleaf plants/small insects	63.07	43.59	10.11

Fruits/pods/seeds/large insects	7.01	4.84	1.12

Granivores

Fruits/pods/seeds/large insects	1.56	1.08	0.25



3.3	Terrestrial Plant Exposure (TerrPlant & AgDrift)

Currently, EFED uses the TerrPlant Model (Version 1.2.1) to evaluate
exposure of terrestrial plants to pesticides applied on agricultural
fields.  In cases where spray drift may be of concern in the risk
assessment EFED also uses the AgDrift model.

3.3.1	TerrPlant

TerrPlant has two basic exposure scenarios.  The first is an adjacent
upland area, which is exposed to the pesticide via drift and dissolved
concentrations in sheet runoff.  The second is an adjacent semi-aquatic
(wetland) area, which is exposed to the pesticide via drift and to
dissolved concentrations in channelized runoff.  Drift is calculated as
a percentage of the application rate (1% for ground, and 5% for aerial,
airblast, or spray chemigation) and is not adjusted for distance from
the application site.  The amount of dissolved pesticide in the runoff
component is estimated based on solubility of the active ingredient. 
TerrPlant estimates are shown in Table 13.

Table 13  Terrestrial Plant Exposure

Application Method	Total Loading (Runoff +Drift) (lb ai/A)	Drift EEC (lb
ai/A)

	Upland areas	Wetland areas	All areas

Use at 0.375 lb ai/A

Aerial	0.0263	0.0938	0.0188

Ground	0.0113	0.0788	0.0038

Use at 0.50 lb ai/A

Aerial	0.0343	0.1225	0.0245

Ground	0.0147	0.1029	0.0049



3.3.2	AgDrift

Because of concerns about effects on non-target plants located in the
overspray or spray drift areas, EFED elected to perform an analysis of
potential deposition of fomesafen using AgDrift modeling software. 
AgDrift was developed using extensive field-measured data sets, and
provides a method of estimating deposition of the compound of concern at
a specified distance away from the application source.  Deposition is
heavily dependent on the method of application and droplet size.  A Tier
I analysis, which is driven primarily by these two variables, was
conducted for both ground and aerial applications.  More sophisticated
(Tier II) analyses also incorporate atmospheric parameters, but were not
deemed necessary for this screening level risk assessment.  Because
terrestrial plants, especially dicotyledons (dicots) are extremely
sensitive to fomesafen, deposition associated with both proposed methods
of application was evaluated.  For ground applications, two alternative
lower rates were also assessed.  The lower alternative rates (0.375 lb
ai/A and 0.2 lb ai/A) were selected based on 1) the lower proposed rate
for aerial application, and 2) the AgDrift predicted deposition of
fomesafen on foliage directly below the application source for the
aerial application rate.  Because the registrant proposed the aerial
rate, EFED presumes it will be efficacious for the target pests. 
Detailed information on input parameters is included in Appendix E.

Point deposition was estimated for both ground (Table 14) and aerial
(Table 15) applications.

Table 14  Estimated Point Deposition of Fomesafen from AgDrift

(Tier I, Ground Application, Low Boom, 90% Percentile Estimate)

Distance from Application Source (ft)	Fraction of Applied	Point
Deposition (lb ai/A)



Proposed Rate

(0.50 lb ai/A)	Alternative Rate

(0.375 lb ai/A)	Alternative Rate

(0.20 lb ai/A)

0	1.02	0.4994	0.3825	0.0999

10	0.0923	0.0452	0.0346	0.0090

20	0.0437	0.0214	0.0164	0.0043

30	0.0291	0.0143	0.0109	0.0029

40	0.0218	0.0107	0.0082	0.0021

50	0.0177	0.0087	0.0066	0.0017

60	0.0149	0.0073	0.0056	0.0015

70	0.0130	0.0064	0.0049	0.0013

80	0.0115	0.0057	0.0043	0.0011

90	0.0104	0.0051	0.0039	0.0010

100	0.0095	0.0046	0.0036	0.0009

150	0.0066	0.0032	0.0025	0.0006

200	0.0051	0.0025	0.0019	0.0005

250	0.0042	0.0020	0.0016	0.0004

300	0.0035	0.0017	0.0013	0.0003

350	0.0030	0.0015	0.0011	0.0003

400	0.0026	0.0012	0.0010	0.0002

450	0.0023	0.0010	0.0009	0.0002

500	0.0021	0.0010	0.0008	0.0002

550	0.0019	0.0009	0.0007	0.0002

600	0.0017	0.0008	0.0006	0.0002



Table 15  Estimated Point Deposition of Fomesafen from AgDrift

(Tier I, Aerial Application, 90% Percentile Estimate)

Distance from Application Source (ft)	Fraction of Applied	Point
Deposition

 (lb ai/A)



Proposed Rate

(0.375 lb ai/A)

0	0.4549	0.1900

100	0.0900	0.0367

200	0.0470	0.1760

300	0.0312	0.1170

400	0.0234	0.0088

500	0.0192	0.0072

600	0.0164	0.0062

700	0.0146	0.0055

800	0.0124	0.0050

900	0.1330	0.0046



4.	Effects Assessment

Toxicity endpoints are established based on data generated from
guideline studies submitted by the registrant, and from open literature
studies that meet the criteria for inclusion into the ECOTOX database
maintained by EPA/ORD.  EFED policy is to use the most sensitive
endpoint for each taxa evaluated.  In aquatic systems, taxa evaluated
include aquatic plants, invertebrates, and fish.  Fish serve as a
surrogate for aquatic-phase amphibians.  Where data are available,
separate endpoints are used for freshwater and estuarine/marine
organisms.  In terrestrial systems, taxa evaluated include birds and
mammals.  Bird endpoints are generally derived from guideline studies on
bobwhite quail and/or mallard duck.  Bird data is used as a surrogate
for reptiles and terrestrial-phase amphibians.  Mammal data is derived
from guideline studies conducted on laboratory rats, mice, or rabbits.

 4.1	Aquatic Guideline Data

Fomesafen was originally registered for use in the 1980s.  Guideline
studies from that time were available for aquatic invertebrates and
fish, both freshwater and marine/estuarine.  Although some of the
studies were conducted on formulated product, and would not be
acceptable under current standards, they were classified as core or
supplemental under the guidelines at the time they were submitted.  When
necessary, endpoints were re-calculated and/or data were converted to
express toxicity on the basis of active ingredient.  Details of
conversion are included in Appendix E.  Aquatic plant data were
submitted by the registrant (upon request by EFED), during the
development of this risk assessment.  Although the Data Evaluation
Review (DER) process has not yet been completed for these studies, they
have been provisionally classifed as Supplemental, and the toxicity data
has been incorporated into the assessment.  Overall, fomesafen is
slightly toxic to practically nontoxic to invertebrates and practically
non-toxic to fish on an acute basis (Table 16).  Chronic data were also
available, and are presented in Table 17.



Table 16  Acute Aquatic Data from Registrant-submitted Studies

Species	LC50 (ppm)	95% C.I. (ppm)	NOAEC (ppm)	Classification

(MRID)

Freshwater Organisms

Green alga1 (Selenastrum capricornutum)	0.12

(biomass)	0.05-0.34	0.02	Supplemental

(46673804)

Technical

Water flea

(Daphnia magna)	376

(practically nontoxic)	323-437	117	Core2, 3

(163169)

Formulation

Rainbow Trout

(Onchorynchus mykiss)	126

(practically nontoxic)	117-135	80	Core2, 3

(103023)

Formulation

Estuarine/ Marine organisms

Marine diatom1 (Skeletonema costatum)	1.51

(biomass)	ND	0.94	Supplemental

(46673806)

Technical

Mysid shrimp

(Mysidopsis bahia)	25

(slightly toxic)	19-38	ND	Core2

(135647)

Technical

Sheepshead minnow

(Cyprinodon varigetus)	>163

(practically nontoxic)	ND	>163	Core2, 3 

(135651)

Formulation

1Provisional data and classification, pending final review.  2Data are
from studies originally reviewed and classified in 1984, some of which
used formulated product.  3For purposes of this risk assessment, test
concentrations were adjusted for percent a.i. if necessary, and
endpoints were re-calculated using TOXANAL software.  ND-not determined.

Table 17  Chronic Aquatic Data from Registrant-submitted Studies

Species	NOAEC (ppm)	LOAEC

 (ppm)	Endpoints Affected	Classification1

(MRID)

Freshwater Organisms

Water flea

(Daphnia magna)	50	100	Reduced growth,

Total # of offspring	Core

(135642)

Formulation

Estuarine/ Marine organisms

Mysid shrimp

(Mysidopsis bahia)	0.7	1.7	Parental mortality	Core

(135648)

Formulation

Sheepshead minnow2

(Cyprinodon varigetus)	12.2	20.1	Reduced larval survival	Core

(135644)

Formulation

1Data are from studies originally reviewed and classified in 1984, some
of which used formulated product.  2For purposes of this risk
assessment, test concentrations were adjusted for percent a.i.  

4.2	Aquatic Data from ECOTOX

The ECOTOX database was accessed, and no toxicity data for fomesafen
were located. 

4.3	Terrestrial Plant Guideline Data

Terrestrial plant guideline studies were submitted during the
development of this risk assessment.  Data are shown below (Table 18),
but are considered provisional pending final data evaluation review. 
Fomesafen is effective, both pre- and post-emergent, against a variety
of plants, although dicots appear to be more sensitive than monocots for
both endpoints.  The product is marketed as a control for broad-leafed
weeds.  In some cases, calculated EC25s were below the concentrations
tested, so a NOAEC was not determined.  The most sensitive endpoint,
used in the risk assessment, is the vegetative vigor EC25 for radish
(0.0016 lb ai/A).

Table 18  Terrestrial Plant Guideline Data

Species	Common name	Class

	EC25 

(lb ai/A)	NOAEC 

(lb ai/A))	Classification1

(MRID)

Vegetative Vigor

Raphanus sativus	Radish	D	0.0016	0.00098	Supplementary

(46673802)

Echinochloa crus-galli	Barnyard grass	M	0.31	0.25

	Seedling emergence

Lycopersicon esculentum	Tomato	D	0.005	ND	Supplementary

(46673801)

Allium cepa	Onion	M	0.089	ND

	1 Provisional classification, pending final data evaluation review.

Efficacy data (MRID 135656, Appendix E) were part of the data package
submitted.  The efficacy data included pre-emergence and post-emergence
treatment of 24 plant species, at two concentrations (0.25 and 1.0 kg
ai/ha).  The two concentrations bracket the currently proposed rates
(0.42 and 0.54 kg ai/ha).  The plant species tested included both
monocots (11 species) and dicots (13 species).  Both crop (7 species)
and non-crop (17 species) plants were evaluated.  With the exception of
soybeans, all plants tested experienced >20% “damage” when treated
pre-emergence, with a significant number (65%) experiencing >80% damage
when treated with the lower concentration (0.25 kg ai/ha).  Applied
post-emergence, fomesafen is slightly less effective, with “damage”
typically in the 0-40% range for monocots and 40-80% range for dicots. 
The report did not specify how damage was quantified.

4.4	Avian and Small Mammal Guideline Data

Guideline studies were available for birds (both dose and dietary), and
small laboratory mammals (dose).  On the basis of both dose and dietary
values, fomesafen is practically non-toxic to birds and slightly toxic
to mammals (Table 19).  Endpoints for female guinea pigs and mallard
ducks were used to develop risk quotients.

Table 19  Avian and Small Mammal Guideline Data from Acute Studies

Species	LC50 (ppm)	95% C.I. (ppm)	NOAEC (ppm)	Classification1

(MRID)

Acute dose

Mallard duck	>5,000

(practically non-toxic)	ND	ND	Core

(163168)

Rat	F 1499

M 1858

(slightly toxic)	(1302-1749)

(1420-2546)	1219

975	Minimum

(164901)

Mouse	F  745

M  766

(slightly toxic)	(512-1286)

(525-1341)	487

312	Minimum

(164901)

Guinea Pig	F  607

(slightly toxic)	ND	244	Minimum

(164901)

Acute dietary

Bobwhite quail	>20,000

(practically non-toxic)	ND	13,333	Core

(103022)

Mallard duck	>20,000

(practically non-toxic)	ND	20,000	Core

(163384)

1Data are from studies originally reviewed and classified in 1984. 

ND-Not determined 

Chronic guideline studies (Table 20) were available for birds (mallard
duck and bobwhite quail) and small laboratory mammals (rat).  Bird
guideline studies did not establish a LOAEC, only determining that there
were no effects at the highest (mean-measured) concentration tested. 
This contributes significant uncertainty to the evaluation of chronic
risk to birds.  The mallard duck NOAEC (46 ppm) is used in the
determination of chronic risk to birds, but it may overestimate the risk
to birds.  In some cases, calculated exposure is near or above the
maximum tested concentration.

Table 20  Avian and Small Mammal Guideline Data from Chronic Studies

Species	NOAEC (ppm)	LOAEC

(ppm)	Endpoint Affected	Classification1

(MRID)

Bobwhite quail	51	ND	None	Core

(135640)

Mallard duck	46	ND	None	Core

(135639)

Rat	250	1000	Number of pups born live, number of pups surviving
Acceptable

(144862)

1Data are from studies originally reviewed and classified in 1984.

ND-Not determined  

4.5	Terrestrial Insect Data

Guideline tests for honeybees were submitted (MRID 135651, Core), as was
a field chronic effects study on earthworms (MRID 135652).  The acute
oral LD50 for honeybees was >50 g ai/bee, and the acute contact LD50
was >100 g ai/bee.  The field test for earthworms included two
applications of fomesafen, applied at one-year intervals.  Fields were
treated with 0.5 kg ai/ha and 5.0 kg ai/ha.  No adverse effects on total
numbers, total weights, or numbers of individual species were noted at
the 0.5 kg ai/ha treatment level.  A significant change in numbers of
one species of earthworm (Allolobophura nocturna) was noted at the
higher treatment level, but authors attributed this to modifications in
grass cover caused by the herbicide treatment rather than direct toxic
effects.

Studies were also submitted  (MRID 135656) for eight species of
invertebrates, from the orders Acarina, Hemiptera, Diptera, Lepidoptera,
Coleoptera, and Nemotoda.  Fomsafen was applied to multiple life stages
at concentrations of 250 and 500 ppm.  The greatest level of mortality
in these tests was 9%.  Aphids (Aphis fabae) experienced mortality rates
of 9% at concentrations of 250 ppm and 500 ppm.

4.6	Terrestrial Data from ECOTOX

The ECOTOX database was accessed, and no toxicity data for fomesafen
were located.

4.7	Incident Database Review

EFED maintains EIIS, a database containing reported incidents of damage
to non-target species caused by pesticide use.  There are a total of 28
reported incidents (Appendix F) for fomesafen, 27 of which are damage to
agricultural crops.  Incidents reported cover a range of 9 years
(1994-2002), but many of them (54%) were reported in 2002.  Corn was the
crop most frequently reported damaged, accounting for 21 out of the 24
cases for which the specific crop was reported.  In some cases (5) the
fomesafen was applied directly to the damaged crop, and the legality was
classified as misuse or accidental misuse.  In other cases (17) the
damaged was caused by drift, legality of application unknown.  The
certainty that the incident was related to fomesafen use was generally
classified as probable.  Other crops damaged included green peas,
cotton, and soybeans under registered use conditions. 

 

There is one report of a fish kill.  In this incident, there was a
report of approximately 200 fish (channel catfish, crappie, largemouth
bass, and redear sunfish) dying following a legal application to a
soybean site.  The certainty of the kill being related to fomesafen
runoff is classified as possible.  Application was in accordance with
registered use. 

5.	Risk Estimation

Risk is estimated by calculating the ratio of the expected environmental
concentration and the appropriate toxicity endpoint.  This value is the
risk quotient (RQ), which is then compared to pre-established levels of
concern (LOC) for each category evaluated (Appendix G).  The highest
EECs and most sensitive endpoints are used to determine the screening
level RQ.  Using these two values theoretically results in a
conservative estimate of risk.  More detailed analyses may be conducted
when LOCs are exceeded.

5.1	Aquatic RQ Summary

No aquatic RQs, either acute or chronic, exceeded LOCs at any of the
proposed application rates (Table 21).  Acute RQs ranged from <0.001
(invertebrates and fish) to 0.13 (freshwater plants, Mississippi cotton
scenario, ground application).  Chronic RQs for fish and invertebrates
were <0.02.  Endangered species RQs for plants were <0.67 for freshwater
plants and <0.02 for saltwater plants.  Fomesafen appears to pose very
low risk to aquatic ecosystems based on the data currently available.

Table 21 Summary of Aquatic RQs

Taxa	Acute RQ	Chronic RQ1	Endangered Species RQ2

Use on Beans at 0.375 lb a.i./A (MS scenario, aerial application)

FW Aquatic Plants	0.06	NA1	0.33 

FW Aquatic Invertebrates	<0.001	<0.001	<0.001

FW Fish	<0.001	NC	<0.001

SW Aquatic Plants	0.01	NA1	0.008 

SW Aquatic Invertebrates	<0.001	0.01	<0.001

SW Fish	<0.001	<0.001	<0.001

Use on Cotton at 0.375 lb a.i./A (MS scenario, aerial application)

FW Aquatic Plants	0.10	NA1	0.53

FW Aquatic Invertebrates	<0.001	<0.001	<0.001

FW Fish	<0.001	NC	<0.001

SW Aquatic Plants	0.01	NA1	0.013

SW Aquatic Invertebrates	<0.001	0.02	<0.001

SW Fish	<0.001	<0.001	<0.001

Use on Cotton at 0.5 lb a.i./A (MS scenario, ground application)

FW Aquatic Plants	0.13	NA1	0.66

FW Aquatic Invertebrates	<0.001	<0.001	<0.001

FW Fish	<0.001	NC	<0.001

SW Aquatic Plants	0.01	NA1	0.016

SW Aquatic Invertebrates	<0.001	0.02	<0.001

SW Fish	<0.001	0.001	<0.001

1 There are no chronic aquatic plants tests. 2  Endangered species RQ
for plants are calculated based on NOAEC.  Endangered species RQ for
animals are calculated in the same way as acute risk values, but
compared to a different LOC.    NA – not applicable, NC – Not
calculated, data not available.

5.2	Terrestrial RQ Summary

Risk quotients for terrestrial plants were calculated using the most
sensitive plant and most sensitive endpoint (radish, dicot, height, EC25
0.0016, NOAEC 0.00098).  Because of the concern for herbicide impacts on
non-target plants RQs were calculated using both EFED’s standard
method, TerrPlant, and also based on an AgDrift estimate of point
deposition.

Terrestrial RQs for birds and mammals were calculated using EFED’s
TREX program, version 1.1.  TREX uses the Kenaga nomagram to estimate
potential chemical residue on food items, calculates exposure by
estimating food consumption via allometric equations (assuming the
organism exclusively consumes contaminated items), and then calculates
RQs based on a weight-adjusted LC50.  RQs were calculated for both
proposed application rates.

5.2.1	Terrestrial Plants

Risk quotients were calculated based on the exposures estimated by both
TerrPlant and AgDrift.  Calculations were made using data from both
types of guideline studies (vegetative vigor and seedling emergence). 
Evaluations were done for both monocots and dicots.  The most sensitive
endpoint was dicot vegetative vigor (EC25=0.0016 lb ai/A, NOAEC=0.00098
lb ai/A).  For the seedling emergence tests, calculated EC05 was
unavailable, and the reported NOAEC was greater than the calculated
EC25, so the EC25 was used as the toxicity endpoint for the endangered
species analysis.

5.2.1.1	TerrPlant

For both proposed uses of fomesafen, ground application at 0.5 lb ai/A
and aerial application at 0.375 lb ai/A, total loading RQs exceeded the
acute plant risk LOC (1) for both monocots and dicots in adjacent
wetland areas but not in upland areas (Table 22).  Drift-based RQs were
exceeded for dicots in all adjacent areas.  LOC exceedences for acute
risk to endangered plants followed the same pattern, but were of greater
magnitude.  RQs based on the two alternative ground application
scenarios (0.375 lb ai/A and 0.2 lb ai/A) were also generated.  At both
these rates, there were no exceedences for monocots.  RQs for both total
loading to wetland areas and drift only exceeded the acute risk and
endangered species acute risk LOCs for dicots.



Table 22  Terrestrial Plant Risk Quotients Based on TerrPlant 

Application Method	Total Loading RQ

(Seedling emergence)	

Total Loading RQ

(Seedling Emergence) 	Drift RQ 

(Vegetative vigor)

	Upland areas	Wetland areas	All areas

	Monocot	Dicot	Monocot	Dicot	Monocot	Dicot

Acute risk

Use at 0.2 lb ai/A (alternative)

Ground	0.07	0.08	0.47	0.53	0.01	2.04 a

Use at 0.375 lb ai/A

Aerial	0.29	0.33	1.05 a	1.19 a	0.06	11.72 a

Ground (alternative)	0.13	0.14	0.88	1.00 a	0.01	2.34 a

Use at 0.5 lb ai/A

Ground	0.17	0.19	1.16 a	1.30 a	0.02	3.06 a

Endangered species acute risk

Use at 0.2 lb ai/A (alternative)

Ground	0.07	0.08	0.47	0.53	0.01	1.25 a

Use at 0.375 lb ai/A

Aerial	0.29	0.33	1.05 a	1.19 a	0.08	19.13 a

Ground (alternative)	0.13	0.14	0.88	1.00 a	0.02	3.83 a

Use at 0.5 lb ai/A

Ground	0.17	0.19	1.16 a	1.30 a	0.02	5.00 a

a Exceeds or equals LOC of 1

5.2.1.2	AgDrift

Figure 3 and 4 show RQs calculated for both aerial- and ground-applied
fomesafen, as does Table 23.  For the proposed aerial application rate,
a distance from the application site where the RQ drops below the LOC
could not be determined.  RQs for ground application were calculated
assuming a low boom.  If a high boom is used, the calculated RQs will
underestimate the risk.  RQs were calculated for the proposed
application rate (0.5 lb ai/A), and two alternative rates (0.375 lb ai/A
and 0.2 lb ai/A).  At the proposed rate, RQs exceed the acute risk LOC
until approximately 350 ft away from the application source.  RQs exceed
the endangered plant species acute risk until approximately 550 ft away
from the source (not shown on graph).  At the alternative rate of 0.375
lb ai/A, RQs clear the acute risk LOC at 250 ft away from the source,
and the endangered plant acute risk at 450 ft.  For a 0.2 lb ai/A rate,
RQs drop below the acute risk LOC at about 60 ft, and the endangered
species LOC at approximately 100 ft.

Table 23  Required Distance from Application to Fall Below LOC

Application Method	Application Rate

(lb ai/A)	Clearance Distance (ft)



Acute LOC	Endangered Species LOC

Aerial	0.375	>900 ft	>900 ft

Ground 

(low boom)	0.5	350	550

	0.375	250	450

	0.2	60	100





5.2.2	Avian RQ Summary

At the proposed application rate of 0.5 lb ai/A, no acute dose- or
dietary-based LOCs are exceeded for birds (Table 24).  Chronic LOCs for
birds in three out of the four food categories (short grass, tall grass,
and broadleaf plants/small insects) are exceeded.

Table 24  Avian RQ Summary  0.5 lb ai/A

Risk quotients based on Kenaga upper bound EECs	Acute dose-based RQs
Acute dietary-based RQs	Chronic RQs

	20g	100g	1000g	All birds	All birds

Short grass	0.05	0.02	0.01	0.01	2.56 c

Tall grass	0.02	0.01	0.00	0.00	1.17 c

Broadleaf plants/small insects	0.03	0.01	0.00	0.00	1.44 c

Fruits/pods/seeds/lg insects	0.00	0.00	0.00	0.00	0.16 c

a exceeds acute risk LOC (0.5)

b exceeds endangered species acute risk LOC (0.1)

c exceeds chronic risk LOC (1.0)

At the proposed application rate of 0.375 lb ai/A, no acute dose- or
dietary-based RQs exceed any LOCs (Table 25).  The chronic LOC is
exceeded for birds consuming the food categories of short grass and
broadleaf plants/small insects.

Table 25  Avian RQ Summary: 0.375 lb ai/A 

Risk quotients based on Kenaga upper bound EECs	Acute dose-based RQs
Acute dietary-based RQs	Chronic RQs

	20g	100g	1000g	All birds	All birds

Short grass	0.04	0.02	0.01	0.00	1.96 c

Tall grass	0.02	0.01	0.00	0.00	0.90

Broadleaf plants/small insects	0.02	0.01	0.00	0.00	1.10 c

Fruits/pods/seeds/lg insects	0.00	0.00	0.00	0.00	0.12

a exceeds acute risk LOC (0.5)

b exceeds endangered species acute risk LOC (0.1)

c exceeds chronic risk LOC (1.0)

At the proposed application rate of 0.2 lb ai/A, no acute dose- or
dietary-based LOCs are exceeded for birds (Table 26).  The chronic LOC
for birds in the short grass food category is exceeded.

Table 26  Avian RQ Summary  0.2 lb ai/A (alternative)

Risk quotients based on Kenaga upper bound EECs	Acute dose-based RQs
Acute dietary-based RQs	Chronic RQs

	20g	100g	1000g	All birds	All birds

Short grass	0.02	0.01	<0.01	<0.01	1.04 c

Tall grass	0.01	<0.01	<0.01	<0.01	0.48

Broadleaf plants/small insects	0.01	0.01	<0.01	<0.01	0.59

Fruits/pods/seeds/lg insects	<0.01	<0.01	<0.01	<0.01	0.07

a exceeds acute risk LOC (0.5)

b exceeds endangered species acute risk LOC (0.1)

c exceeds chronic risk LOC (1.0)

5.2.3	Small Mammal RQ Summary

At the proposed application rate of 0.50 lb ai/A, dose-based RQs exceed
the endangered species LOC for two size classes of mammals (15g and 35
g) consuming short grass (Table 27).  Using the dose-based RQ, chronic
LOC is exceeded for mammals consuming the food categories of short grass
(all weights), tall grass (15g, 35g), and broadleaf plants/small insects
(15g, 35g).  No chronic dietary based-RQs exceed any LOCs.

Table 27  Small Mammal RQ Summary:  0.50 lb ai/A

Risk Quotients based 

on Kenaga 

upper bound EEC	Acute 

dose-based RQs	Chronic 

dose-based RQs	Chronic dietary-based RQs

	15 g	35 g	1000 g	15 g	35 g	1000 g 	All mammals

Short grass	0.13 b	0.11 b	0.06	4.08 c	3.49 c	1.87 c	0.47

Tall grass	0.06	0.05	0.03	1.87 c	1.60 c	0.86	0.22

Broadleaf plants/

small insects	0.07	0.06	0.03	2.30 c	1.96 c	1.05 c	0.26

Fruits/pods/seeds/

lg insects	0.01	0.01	0.00	0.26	0.22	0.12	0.03

Seeds (granivores)	0.00	0.00	0.00	0.06	0.05	0.03	NA

a exceeds acute risk LOC (0.5)

b exceeds endangered species acute risk LOC (0.1)

c exceeds chronic risk LOC (1.0)

At the proposed application rate of 0.375 lb ai/A, no acute dose-based
RQs for mammals exceed any LOCs, although the RQ for small (15g) mammals
consuming short grass equals the endangered species LOC (Table 28). 
Using the dose-based RQ, the chronic LOC is exceeded for mammals
consuming the food categories of short grass (all weights), tall grass
(15g, 35g), and broadleaf plants/small insects (15g, 35g).

Table 28  Small Mammal RQ Summary:  0.375lb ai/A

Risk Quotients based 

on Kenaga 

upper bound EEC	Acute 

dose-based RQs	Chronic 

dose-based RQs	Chronic dietary-based RQs

	15 g	35 g	1000 g	15 g	35 g	1000 g 	All mammals

Short grass	0.10b	0.08	0.05	3.12c	2.67 c	1.43 c	0.36

Tall grass	0.05 	0.04	0.02	1.43 c	1.22 c	0.66	0.17

Broadleaf plants/

small insects	0.06	0.05	0.03	1.76 c	1.50 c	0.80	0.20

Fruits/pods/seeds/

lg insects	0.01	0.01	0.00	0.20	0.17	0.09	0.20

Seeds (granivores)	0.00	0.00	0.00	0.04	0.04	0.02	NA

a exceeds acute risk LOC (0.5)

b exceeds endangered species acute risk LOC (0.1)

c exceeds chronic risk LOC (1.0)

At the alternative application rate of 0.2 lb ai/A, no acute risk LOCs
are exceeded (Table 29).  Chronic dose-based RQs for the 15g and 35g
mammals consuming short grass exceed the LOC.  No chronic dietary
based-RQs exceed any LOCs.

Table 29 Small Mammal RQ Summary:  0.2 lb ai/A (alternative)

Risk Quotients based 

on Kenaga 

upper bound EEC	Acute 

dose-based RQs	Chronic 

dose-based RQs	Chronic dietary-based RQs

	15 g	35 g	1000 g	15 g	35 g	1000 g 	All mammals

Short grass	0.05	0.04	0.02	1.67 c	1.42 c	0.76	0.19

Tall grass	0.02	0.02	0.01	0.65	0.65	0.35	0.09

Broadleaf plants/

small insects	0.03	0.03	0.01	0.80	0.80	0.43	0.11

Fruits/pods/seeds/

lg insects	<0.01	<0.01	<0.01	0.09	0.09	0.05	0.01

Seeds (granivores)	<0.01	<0.01	<0.01	0.02	0.02	0.01

	a exceeds acute risk LOC (0.5)

b exceeds endangered species acute risk LOC (0.1)

c exceeds chronic risk LOC (1.0)

5.2.4.	Terrestrial Insects

EFED currently has no established method for assessing risk to
terrestrial insects  However, fomesafen appears to be of relatively low
toxicity to bees, based on submitted guideline tests.  Non-guideline
field tests on earthworms submitted by the registrant showed that
fomesafen did not have observable adverse effects on total numbers,
total weights, or numbers of individual species at a treatment level of
0.45 lb ai/A.  Decline in the population of one species of earthworms in
the test plots was attributed to the change in plant cover on the plot
as a result of the herbicide application.

6.	Risk Description

The risk description is presented in terms of the type of ecosystem
assessed (aquatic or terrestrial).  Where appropriate, the description
is further subdivided into taxa and application rate.  A separate
section is included to summarize potential effects on endangered
species.

6.1	Aquatic Risk

Based on currently available data, fomesafen appears to be of relatively
low toxicity to aquatic organisms, both animals and plants in freshwater
and estuarine/marine systems.  Both acute and chronic effects were
considered.  Fomesafen may indirectly affect aquatic systems by damaging
plants in adjacent wetland or riparian zones.  Modification of the
vegetation in wetlands or riparian zones could cause decreased
allochthonous input, increased sediment input, destabilization of the
stream bank, or changes in the structural components (plant).  Effects
on waterbody-associated plant communities can be minimized by ensuring
an adequate offset distance is maintained between the application site
and the wetland or riparian zone.  Appropriate distance is dependent on
application rate, application methods, and weather conditions.

6.2	Terrestrial Risk

The terrestrial risk description is divided into two sections:  birds
and mammals; and plants and insects.

6.2.1	Birds and Mammals

Risk characterization for birds and mammals is presented in terms of the
three application rates evaluated.

6.2.1.1	Application Rate of 0.50 lb ai/A

At the proposed application rate of 0.50 lb ai/A, fomesafen poses an
acute endangered species risk to two size classes (15g and 35 g) of
small mammals which consume short grass. Using the chronic dose-based
calculation, there is risk to all size classes of small mammals
consuming short grass, broadleaf plants, or small insects, and to 15g
and 35g small mammals consuming tall grass.  Using chronic dietary-based
calculations, there is no risk to the small mammals. EFED uses both
calculations because it is difficult to extrapolate laboratory
conditions to the wild.  In a case like this, where the LOC is exceeded
by one method of calculation, but not in the other, the interpretation
is still that there is some risk.  Small mammals often forage within a
relatively limited homerange, and may consume a diet comprised
completely of contaminated items.  Effects noted at the LOAEC included
the number of pups born live, and number surviving, thus the
reproduction of affected mammals may decline.  Without a detailed,
site-specific analysis, EFED cannot determine the specific impact
chronic effects will have on small mammal populations at or near the
treatment site. 

At the 0.50 lb ai/A application rate, may be a chronic risk to birds
consuming short grass, broadleaf plants, or small insects, using the
dietary-based calculation (RQ 1.44-2.56).  The chronic bird endpoint is
based on a study that did not determine an LOAEC, so it may overstate
the potential risk for birds.  Oxyfluorfen, a chemical in the same class
as fomesafen, has a chronic NOAEC of 124 mg ai/kg-diet and a LOAEC of
256 mg ai/kg-diet (MRID 46070102) for the more sensitive species,
bobwhite quail.  On an acute dietary basis, oxyfluorfen (LC50 390 ppm)
is more toxic than fomesafen (LC50 20,000 ppm).  The oxyfluorfen chronic
NOAEC is higher than the current NOAEC for fomesafen

6.2.1.2	 Application Rate of 0.375 lb ai/A

The pattern of exceedences for the 0.375 lb ai/A application rate is the
similar to the 0.49 lb ai/A application rate.  The acute RQ for the
small size class (15 g) mammals eating short grass exceeds the LOC. 
Chronic RQs (1.22-3.12) for mammals consuming short grass, tall grass,
broadleaf plants, and small insects also exceeded LOCs, thus there may
be also be a slight risk to these organisms.  Based on exceedences of
the chronic LOC (RQs 1.1-2.0) for birds consuming short grass, broadleaf
plants, or small insects, there may be risk to these organisms.  

6.2.1.3	Application Rate of 0.2 lb ai/A (Alternative)

At the alternative application rate of 0.2 lb ai/A, the only the chronic
dose-based RQs for small mammals of the 15g (RQ=1.67) and 35g (RQ=1.42)
size classes consuming short grass exceed LOCs.  The chronic
dietary-based RQ for small mammals consuming short grass (RQ=0.19) does
not exceed the LOC.  Examples of small mammals consuming short grass
include rabbits and some mice.

6.2.2	Plants and Insects

The non-target organisms of greatest concern for fomesafen are plants in
the overspray and spray drift zones. Based on available data, effects on
terrestrial insects do not appear likely.  Fate data do not indicate
fomesafen is likely to bioaccumulate, or be subject to long-range
atmospheric transport.  It is, however, persistent in soil, and may
affect plants growing in the soil of treated fields or overspray areas
for an extended period (approximately a year) following application. 
Because of the persistence, it is also likely to accumulate in fields
repeatedly treated with fomesafen, even if the field is only treated in
alternate years.  The theoretical maximum concentration occurs in about
10 years if the field is treated in alternate years.  Maximum residual
concentration for an application rate of 0.375 lb ai/A is 0.29 lb ai/A,
and for an application rate of 0.5 lb ai/A is 0.38 lb ai/A These
concentrations are greater than the seedling emergence EC25s of the most
sensitive dicot (tomato, EC25 0.005 lb ai/A) and the most sensitive
monocot (onion, EC25 0.089 lb ai/A).   Shallow groundwater used for
irrigation of agricultural fields could potentially contain sufficient
fomesafen to affect some crops. Based on estimated concentrations
delivered to a field receiving 2 inches of irrigation water
(0.0004-0.0077 lbs ai/A, based on application rate of 0.5 lb ai/A to
field), sensitive crop species such as radish (EC25 0.0016 lb ai/A,
vegetative vigor) could be affected.  How long fomesafen will persist in
the groundwater is not well defined. 

Plants potentially affected by fomesafen include crops in neighboring
fields, hedgerows, riparian zones and wetlands.  Using AgDrift (Tier 1),
EFED was unable to calculate the distance required for the acute plant
risk to fall below the LOC for aerial applications, with toxicity
predicted to occur at least to 900 ft beyond the application source. 
Fomesafen has the potential to adversely affect plant communities of
concern beyond the edges of the treated field.  These effects can be
minimized by use of ground application methods, and lower application
rates.

Because fomesafen is an herbicide, it may affect the primary
productivity, community composition, and/or structure of herbaceous
communities located near the margins of the treated fields.  EFED has no
data with which to evaluate the potential effect on woody plants,
although given the mode of action for fomesafen (cell membrane
disruption), woody plants may be more resistant.  However, modifications
to the plant community may have significant effects on the populations
of animals dependent on those communities.  Based on the currently
proposed application rates (0.50 lb ai/A, ground; fomesafen should not
be used within 350 ft of non-target plant communities of concern, or 600
ft of endangered plant species for ground applications.  EFED cannot
estimate a “no-effect” distance for the currently proposed aerial
application rate (0.375 lb ai/A).  Based on available data, a
“no-effect” acute risk offset would be >1000 ft for aerial
applications.  Using the alternative rate of 0.2 lb ai/A and a ground
application method, the effect on nearby non-target plant communities
would be considerably lessened.  At 60 ft away from the application
source, the RQ drops below the acute risk LOC, and at 100 ft away from
the application source, the RQ drops below the endangered species acute
risk LOC.

6.3	Endangered Species 

For a screening level risk assessment, EFED determines what endangered
species may be affected by using the LOCATES database to search for
organisms which are present in the same county as the crop being
assessed.  Potential direct effects are evaluated based on taxa which
have RQs that exceed the LOC.  For terrestrial organisms, evaluation of
potential effects is also based on the organism’s size and diet. 
Organisms at risk for indirect effects include ones whose:

habitat may have been significantly altered by the action, or

primary food source may have been affected.

6.3.1	Aquatic Endangered Species

No aquatic endangered species are at risk for direct effects from
fomesafen.  Indirect effects to aquatic organisms are possible, based on
potential effects on riparian and wetland plant communities.  EFED
requires greater spatial detail to evaluate the exposure and impact of
fomesafen to aquatic ecosystems containing endangered species. 
Magnitude of effect would be correlated to application method and rate,
and composition of the plant community of concern. 

6.3.2	Plants

Direct Effects

Terrestrial plants are the taxa most at risk for direct effects from
application of fomesafen especially the dicots.  Table 30 shows how many
endangered plants are known to occur in counties where the crops
proposed for registration are grown.  This represents a list of
potential impacts, but the likelihood of effects cannot be better
estimated without a detailed spatial analysis.  A more detailed list is
in Appendix H.  The states of greatest concern, based on number of
species potentially affected are California (all proposed crops), Hawaii
(snap beans), North Carolina (cotton), and Texas (cotton).  A species
list is included in Appendix H.



Table 30  Endangered Plants by Crop and Species

State	Cotton	Snap Beans	Dry Beans

	Monocot	Dicot	Monocot	Dicot	Monocot	Dicot

Alabama	3	9	0	0	0	0

Arizona	1	9	1	4	1	4

Arkansas	0	2	0	0	0	0

California	7	51	6	153	10	107

Colorado	0	0	1	3	1	3

Connecticut	0	0	0	1	0	1

Florida	0	3	0	0	0	0

Georgia	2	9	0	0	0	0

Hawaii	0	0	22	233	0	0

Idaho	0	0	0	2	0	2

Iowa	0	0	2	1	2	1

Kansas	1	1	0	0	0	0

Maine	0	0	1	1	1	1

Michigan	0	0	2	2	2	2

Minnesota	0	0	1	2	1	2

Mississippi	0	2	0	0	0	0

Missouri	0	2	0	0	0	0

Nebraska	0	0	1	2	1	2

New Mexico	0	5	0	1	0	1

New York	0	0	1	3	1	3

North Carolina	2	14	1	1	1	1

North Dakota	0	0	1	0	1	0

Oregon	0	0	0	3	0	3

Pennsylvania	0	0	1	0	1	0

South Carolina	3	10	0	0	0	0

South Dakota	0	0	1	0	1	0

Tennessee	0	5	0	0	0	0

Texas	2	17	1	4	1	4

Utah	0	0	0	1	0	1

Washington	0	0	0	1	0	1

Wyoming	0	0	0	2	0	2

Virginia	0	3	0	0	0	0



Indirect Effects

Pesticide-mediated indirect effects to plants are usually the loss of an
important pollinator or dispersal species.  Given the relatively low
toxicity of fomesafen to animals in general, the likelihood of these
types of effects appears to be extremely low.  Some endangered plant
species may require the presence of other non-endangered plant species
to create a suitable habitat.  Fomesafen effects on the habitat plants
could constitute an indirect effect, but without detailed information on
the plant’s life history and distribution, EFED is unable to even
qualitatively evaluate this type of effect.

6.3.3	Birds, Reptiles & Amphibians

Direct effects (Birds)

A search was conducted on LOCATES to determine what endangered birds are
reported to occur in the same counties in which cotton, dry beans, and
snap beans are grown.  A total of 71 bird species were reported.  These
organisms were sorted by dietary habits and size classes to determine
which were in categories with exceedences of the LOCs.  A full list of
specific organisms and reasons why they were not retained as a species
of concern is included in Appendix H.  A total of 12 species (Table 31)
remained in categories potentially at direct risk from fomesafen. 

Table 31  Endangered birds potentially at risk from fomesafen

Species

Size class	0.5

lb ai/A	0.375

lb ai/A	0.2

lb ai/A

Common name	Latin name

A	C	A	C	A	C

Invertivores

Gnatcatcher, Coastal California	Polioptila californica californica	S

*

*



Vireo, Least Bell’s	Vireo bellii pusilus	S

*

*



‘Akepa, Hawaii	Lexops coccineus coccineus	S

*

*



‘Akepa, Maui	Lexops coccineus ochraceaus	S

*

*



Elepaio, Oahu	Chasiempis sandwichensis ibidis	S

*

*



Flycatcher, Southwestern willow	Empidonax traillii extimus	S

*

*



Creeper, Hawaii	Oreomystis mana	S

*

*



Po’ouli	Melamprosops phaesoma	S

*

*



Plover, 

Western snowy	Charadrius alexandrinus nivosus	S

*

*



Sparrow, San Clemente Sage	Aphispiza belli clementeae	S

*

*



Warbler, Bachman’s	Vermivora bachmanii	S

*

*



Millerbird, Nihoa	Acrocephalus familiaris kingi	S

*

*



Duck, Laysan	Anas laysanensis	M

*

*



A- Acute, C-Chronic, * - risk

Direct effects (Reptiles and Amphibians)

A search was conducted on LOCATES to determine what endangered reptiles
and amphibians are reported to occur in the same counties in which
cotton, dry beans, and snap beans are grown.  A total of 29 reptiles and
17 amphibians were reported.  These organisms were sorted by dietary
habits to determine which were in categories with exceedences of the
LOCs. Amphibians with no terrestrial phase were excluded.  A full list
of specific organisms and reasons why they were not retained as a
species of concern are listed in Appendix H.  A total of 20 species
(Table 32) remained in categories potentially at direct risk from
fomesafen.  Further refinement of potential risk will require spatially
explicit analysis.

Table 32  Endangered reptiles and amphibians potentially at risk from
fomesafen

Species

Size class	0.50

lb ai/A	0.375

lb ai/A	0.2

lb ai/A

Common name	Latin name

A	C	A	C	A	C

Herbivores

Tortoise, Desert	Gopherus agassazii	NA

*

*

*

Tortoise, Gopher	Gopherus polyphemus	NA

*

*

*

Invertivores

Frog, 

California red-legged	Rana aurora draytonii	NA

*

*



Frog, 

Chiricahua leopard	Rana chiricahuensis	NA

*

*



Frog, 

Dusky gopher 	Rana capito sevosa	NA

*

*



Frog, 

Mountain yellow-legged	Rana muscosa	NA

*

*



Lizard, 

Blunt-nosed leopard	Gambelia silus	NA

*

*



Salamander, 

California tiger	Ambystoma californiense	NA

*

*



Salamander, 

Cheat Mountain	Plethodon nettingi	NA

*

*



Salamander, 

Desert slender	Batrachoseps aridus	NA

*

*



Salamander, 

Flatwoods	Ambystoma cingulatum	NA

*

*



Salamander, 

Red hills	Phaeognathus hubrichti	NA

*

*



Salamander, 

Santa Cruz long-toed	Ambystoma macrodactylum croceum	NA

*

*



Salamander, Shenandoah	Plethodon shenandoah	NA

*

*



Salamander, 

Sonora tiger	Ambystoma tigrinum stebbinsi	NA

*

*



Skink, 

Blue-tailed mole	Eumeces egregious lividus	NA

*

*



Skink, sand	Neosops reynoldsii	NA

*

*



Toad, 

Arroyo Southwestern	Bufo californicus	NA

*

*



Toad, Houston	Bufo hustonensis	NA

*

*



Turtle, Bog 

(northern population) &

(southern population)	Clemmys muhlenbergii	NA

*

*



Acute, C-Chronic, * - risk, NA – Not applicable (allometric equations
used for birds are not expected to be applicable to reptiles)

Indirect Effects (Birds, Reptiles and Amphibians)

The most likely indirect effect on birds, reptiles, and amphibians is
modification of habitat as a result of damage to plants.  The habitat
modification could include reduced food supply, locations for nesting or
burrowing, and/or reduced cover for predator avoidance.  EFED is
currently unable to evaluate the likelihood or magnitude of such an
effect.

6.3.4	Mammals

Direct effects

A search was conducted on LOCATES to determine what endangered mammals
are reported to occur in the same counties in which cotton, dry beans,
and snap beans are grown.  A total of 63 mammals were reported.  These
organisms were sorted by dietary habits and size classes to determine
which were in categories with exceedences of the LOCs. A full list of
specific organisms and reasons why they were not retained as a species
of concern are listed in Appendix H.  A total of 13 species (Table 33)
remained in categories potentially at direct risk from fomesafen. 

Table 33 Endangered mammals potentially at risk from fomesafen

Species

Size class	0.50

lb ai/A	0.375

lb ai/A	0.2

lb ai/A

Common name	Latin name

A	C	A	C	A	C

Herbivores

Mouse, 

salt marsh harvest	Reithrodontomys raviventris	M	*	*

*

*

Rabbit, pygmy	Brachylagus idahoensis	M	*	*

*

*

Vole, Amargosa	Microtus californicus scirpensis	M	*	*

*

*

Vole,

Florida salt marsh	Microtus pennsylvanicus dukecampbelii	M	*	*

*

*

Vole, 

Hualapai Mexican	Microtus mexicanus hualpaiensis	M	*	*

*

*

Mountain beaver,

Point Arena	Aplodontia rufa nigra	L

*

*



Prairie Dog, Utah	Cynomys parvidens	L

*

*



Rabbit,

Riparian brush	Sylvilagus bachmani riparius	L

*

*



Invertivores

Bat, 

Hawaiian hoary	Lasiurus cinerus semotus	S

*





Bat, Indiana	Myotis sodalis	S

*





Bat, 

Ozark big-eared	Corynorhinos (=Plecotus) townsendii ingens	S

*





Bat, 

Virginia big-eared	Corynorhinos (=Plecotus) townsendii virginianus	S

*





Shrew, Buena Vista Lake Ornate	Sorex ornatus relictus	S

*





A- Acute, C-Chronic, * - risk

Indirect Effects (Mammals)

The most likely indirect effect on mammal is modification of habitat as
a result of damage to plants.  The habitat modification could include
reduced food supply, locations for nesting or burrowing, and/or reduced
cover for predator avoidance.  EFED is currently unable to evaluate the
likelihood or magnitude of such an effect.

Probability of Individual Effects

Toxicity data available for birds and mammals does not support
evaluation of potential individual mortality based on a probit
dose-response relationship.  Estimations based on the default slope of
4.5, and the endangered species LOC of 0.1 produce an estimated 1 in
294,000 chance of individual mortality.  The confidence in estimated
event probabilities based on this dose response relationship and the
listed species LOC is low.

References

Websites

   HYPERLINK "http://www.syngentacroprotection-us.com" 
www.syngentacroprotection-us.com , accessed November 7, 2005.   
HYPERLINK
"http://www.syngentacropprotection-us.com/prod/herbicides/flexstar" 
http://www.syngentacropprotection-us.com/prod/herbicides/flexstar 

www.abcbirds.org, accessed November 7, 2005.  
http://www.abcbids.org/pesticides/appendix_2.htm  

  HYPERLINK "http://www.weeds.iastate.edu"  www.weeds.iastate.edu ,
accessed November 7, 2005.  

http://  HYPERLINK "http://www.weeds.iastate.edu/reference/siteofaction"
 www.weeds.iastate.edu/reference/siteofaction   

Appendix A

Summary of Environmental Fate Studies

Appendix B

Aquatic Exposure Assessment

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Appendix C

Terrestrial Animals Exposure and Risk Quotients 

TREX Output

Appendix D

Terrestrial Plant Exposure and Risk Quotients

TerrPlant  and AgDrift Output

Appendix E

Ecological Effects Data

Appendix F

Incident Database Report

EIIS Output



Appendix G

Risk Quotient Method and Levels of Concern

Appendix H

Threatened and Endangered Species

LOCATES Output

1 Guidance for Selecting Input Parameters in Modeling the Environmental
Fate and Transport of Pesticides. Version II, 2/28/02.

 PAGE   1 

 PAGE   2 

 PAGE   1 

Soil 

invertebrates

Soil accumulation, leaching and runoff

Terrestrial 

plants

Aquatic 

plants

invertebrates

vertebrates

Attribute

Change

Habitat integrity

Reduced cover

Community change

Food chain

Reduction in primary productivity

Reduction in prey

Shift in community composition

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Terrestrial 

insects

Mammals

Birds

Receptors

Spray drift

Direct application

Runoff

Source

Stressor

Fomesafen applied to crop

Figure 1 - Conceptual Model for Fomesafen

Figure 3 – Aerial Application of Fomesafen

Figure 4 – Ground Application of Fomesafen

 

 

