Number range CHAPTER**U. S. ENVIRONMENTAL PROTECTION AGENCY**

**Washington, D.C. 20460**

![](media/image1.png){width="0.78125in" height="0.78125in"} OFFICE OF

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

> PC Code: 036501
>
> DP Barcode: 347376
>
> Date: April 28, 2008

**[MEMORANDUM]{.underline}**

Subject: Revised Registration Review Preliminary Problem Formulation for
the Ecological Risk Assessment of Coumaphos

To: Richard Dumas, Acting Branch Chief

> Wilhelmena Livingston, Chemical Review Manager

Mail Code: 7508P

Special Review and Reregistration Division

From: Fred Jenkins, Biologist

> Iwona, Maher, Chemist
>
> Nancy Andrews, Ph.D., Branch Chief
>
> Mail Code: 7507P

Environmental Risk Branch I

Environmental Fate and Effects Division

Attached is EFED's problem formulation document in support of the
coumaphos registration review docket opening. This memorandum outlines
(1) the methods that will likely be used in the ecological risk
assessment of coumaphos, (2) data gaps, and (3) additional data needs.

> **[Registration Review]{.smallcaps}**

**[Registration Review]{.smallcaps}**

**[Ecological Risk Assessment]{.smallcaps}**

**[Problem Formulation for:]{.smallcaps}**

**[Coumaphos]{.smallcaps}**

3-chloro-7-diethoxyphosphinothioyloxy-4-methylcoumarin

![](media/image2.png){width="2.0833333333333335in"
height="2.0833333333333335in"}

**[Prepared By:]{.smallcaps}**

**Fred Jenkins, Biologist**

**Iwona Maher, Chemist**

**Environmental Risk Branch I**

**Environmental Fate and Effects Division**

**Office of Pesticide Programs**

**[Approved By:]{.smallcaps}**

**Nancy Andrews, Ph.D., Branch Chief**

**Environmental Risk Branch I**

**Environmental Fate and Effects Division**

**Office of Pesticide Programs**

April 28, 2008

1.  **. Problem Formulation**

The problem formulation is used to establish the direction and scope of
an ecological risk assessment. According to the Guidelines for
Ecological Risk Assessment (USEPA, 1998), a problem formulation consists
of defining the problem and purpose for the assessment, and developing a
plan for analyzing and characterizing risks. The critical components of
the problem formulation are the selection of the assessment endpoints,
the formulation of both the risk hypotheses and the conceptual model,
and the development of an analysis plan. The analysis plan and
supporting rationale are aimed at determining whether the coumaphos uses
pose an unreasonable adverse risk to non-target organisms including
those federally listed as threatened or endangered (hereafter referred
to as "listed"). The registered uses of coumaphos include an
insecticide/acaricide treatment on livestock and swine bedding for
control of flies, mites, and ticks, and recently approved IR4 (DP
Barcode 315770; Dated: May 16, 2006) for use on bee hives to control
varroa mites and small hive beetles.

**1.1. Integration of Available Information**

The following coumaphos risk assessment related documents are available
in the docket, and will serve as the basis for this problem formulation:

-   Finalization of Interim Reregistration Eligibility Decisions (IREDs)
    and Interim Tolerance Reassessment and Risk Management Decisions
    (TREDs) for the Organophosphate Pesticides, and Completion of the
    Tolerance Reassessment and Reregistration Eligibility Process for
    the Organophosphate Pesticides. Dated: July 31, 2006. EPA
    738-R-00-10.

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-   EFED Drinking Water and Ecological Risk Review for
    Coumaphos (036501) IR-4 Use on Beehives DP Barcode D315770. Dated:
    May 16, 2006

-   Screening Level Aquatic Exposure Assessment for the Use of Coumaphos
    in the Pacific Northwest and California to Treat Cattle via Spray
    and Vat Dips for the Endangered Species (ES) Consultation Package.
    DP Barcode: D303298. Dated: June 6, 2004

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-   US EPA Reregistration Eligibility Decision (RED) for Coumaphos.
    Dated August 1996. EPA 738 R-96-014.

-   EFED Review for Coumaphos RED. Dated: Sep. 19, 1994. (EFED's
    environmental fate and ecological effects sections for the Coumaphos
    1996 RED)

    1.  **Agency Conclusions Based on Previous Coumaphos Ecological
        Assessments**

> The current ecological risk conclusions from the above mentioned
> coumaphos risk assessment documents are as follows:

Avian Acute Risk

-   Coumaphos is expected to pose a significant acute risk to birds.
    Birds may be subject to primary exposure via ingestion of hair and
    skin debris from treated cattle or secondary exposure via ingestion
    of birds killed by the pesticide, and contaminated with pesticide.

Avian Chronic Risk

-   The Agency concluded that avian reproduction studies were not
    required for coumaphos. Such studies may be required when birds are
    likely to be exposed to a pesticide repeatedly or continuously.
    According to the 1996 RED document's assessment of acute risk if
    there were significant coumaphos exposure to birds, they would be
    killed before chronic effects could occur.

Mammalian Acute Risk

-   Coumaphos is not expected to pose a risk to endangered or
    non-endangered mammals because the limited use pattern of coumaphos,
    i.e., treatment of cattle in confined areas, is not expected to
    result in significant exposure.

Aquatic Organism Risk

-   Based on the Agency analysis, coumaphos usage on cattle is expected
    to pose a high acute risk to aquatic invertebrates. Coumaphos is not
    expected to pose chronic or acute risks to endangered or
    non-endangered fish.

EFED will utilize the information provided by the previous risk
assessment documents as a resource for conducting the ecological risk
assessment for the registration review process. The assessment will
include risk estimates from two exposure pathways: the application of
coumaphos to cattle via spray based on registrant submitted data on
wash-off estimates from cowhide, and from application of bioremediated
spent vat-dip solutions to land. Both exposure pathways maybe equally
important for environmental risks, and are discussed in the screening
level aquatic exposure assessment dated June 6, 2004 (D303298).

The indoor use of the coumaphos and the placement of coumaphos-treated
strips in beehives to avoid contact of bees suggest that there are no
complete routes of exposure to surface waters or to the surrounding
non-target terrestrial environment. Therefore, without evident complete
exposure routes to aquatic and non-target terrestrial organisms, there
are no acute or chronic risk concerns and no concerns for effects to
federally listed threatened or endangered species.

**1.2. Pesticide Type, Class, and Mode of Action**

Coumaphos is an insecticide/acaricide. It belongs to the organophosphate
class of pesticides. The toxic mode of action of coumaphos is the
inhibition of acetyl cholinesterase.

**1.3. Stressor Source and Distribution**

The source of the stressor is considered to be combined residues of the
insecticide coumaphos (PC Code 036501; O,O-diethyl
O-3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl phosphorothioate) and its
oxygen analog, coumaphoxon (O,O-diethyl
O-3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl phosphate) from indoor
food and non-food uses.

**1.4. Overview of Pesticide Usage**

Coumaphos was first registered in the United States in 1958 for use as
an insecticide. A dust formulation, the first end-use product, was
registered the following year for the control of insects on cattle.
Currently, coumaphos is registered for the control of insects, mites,
and ticks on livestock and swine bedding, and to control varroa mites,
and small hive beetles in bee hives.

The predominant use of coumaphos is as an insecticide/acaricide to
control insect pest of beef cattle. It is also used for the same
purposes to treat dairy cattle, horses, sheep, and swine. The targeted
insect pests include flies (face fly, horn fly), ticks, lice, mites
(scabies mite) and screw worms. The formulation types of the registered
coumaphos products include the technical grade active ingredient (96%
pure), manufacturing product (25% a.i. dust), end-use products (1% a.i.
dust, 11.6% a.i. and 6.15% a.i. emulsifiable concentrates, and 42% a.i.
flowable concentrate). Coumaphos is applied directly to the livestock.
The equipment used to apply coumaphos includes dip vats, low and
high-pressure hand wands, back rubber/oiler, mechanical dusters, dust
bags and shaker cans. Depending on animals treated and formulation type,
the maximum label application rates range from 0.005 to 0.025 lbs
a.i./gallon for spray or dip, 0.076 lbs a.i./gallon of oil for back
rubbers, 0.000625 to 0.013 lbs a.i./animal for dust, and 0.042 lbs
ai/1,000 sq. ft. of swine bedding. The coumaphos applications are
primarily done during early spring to late summer or during the fly
season. Multiple applications to livestock and livestock areas are
allowed. The use classifications for the two liquid products, the 11.6%
emulsifiable concentrate and the 42% flowable are as Restricted Use
Pesticides (RUPs). All other products have general use classifications.
For details on the maximum application rates, the application equipment,
and coumaphos product names refer to an attached EFED Label Data Report
dated September 13, 2007 (Attachment A: EFED Label Data Report
036501EF).

> **D. Estimated Usage of Pesticide**

This section summarizes the best estimates available for many of the
pesticide uses of coumaphos, based on pesticide usage information for
1990-1999 available to the Agency. A full listing of all uses of
coumaphos, with the corresponding use and usage data for each site
(cattle or other livestock), has been completed and is included in the
"Quantitative Usage Analysis for Coumaphos," dated August 15, 2000,
which is available in the Public Docket. The data, reported on an
aggregate and site basis, reflect annual fluctuations in use patterns as
well as the variability in using data from various information sources.
Approximately 71,000 lbs a.i. of coumaphos is used annually in the
United States. Table 1 provides further detail regarding the annual
usage amounts of coumaphos in the US.

+---------------+---------------------------+--------------------------+
| Table 1.      |                           |                          |
| Coumaphos     |                           |                          |
| Estimated     |                           |                          |
| Usage for     |                           |                          |
| R             |                           |                          |
| epresentative |                           |                          |
| Sites         |                           |                          |
+---------------+---------------------------+--------------------------+
| Site          | Lbs. Active Ingredient    | Percent Livestock        |
|               | Applied                   | Treated                  |
|               |                           |                          |
|               | (Likely Average1)         | (Likely Average)         |
+---------------+---------------------------+--------------------------+
| Cattle        | 59,000                    | 5.1%                     |
+---------------+---------------------------+--------------------------+
| Other         | 12,000                    | 1.3%                     |
| Livestock     |                           |                          |
+---------------+---------------------------+--------------------------+

> ^1^ Likely averages are the EPA's estimates of what the average uses
> are likely to be sources: U.S. Census of Agriculture; State Usage
> Surveys from TX, KS, NY, WY, and NV; State use recommendations;
> USDA,NASS, 2000 and EPA data. Refer to the "Quantitative Usage
> Analysis for Coumaphos," dated August 15, 2000, prepared by OPP
> Biological and Economic Analysis Division.

Table 2 provides more recent summary of the estimates available for
coumaphos usage in California, based on pesticide usage information for
2004-2006 available to the Agency from the California Department of
Pesticide Regulation.

  ----------------------- ----------------------- -----------------------
  Table 2. Coumaphos use                          
  in California from 2004                         
  to 2006                                         

  Year                    Site                    Lbs AI

  2004                    Beehives (all or        15.43735
                          unspec.)                

  2004                    CHECKMITE+              47.1

  2004                    Honey (sugar crop)      0.0125

  2005                    Beehives (all or        0.59993
                          unspec.)                

  2006                    Beehives (all or        3.00378
                          unspec.)                
  ----------------------- ----------------------- -----------------------

By far, the largest use for this insecticide is livestock. This is
largely due to the treatment of livestock entering the US from Mexico as
part of the USDA tick quarantine to prevent Texas cattle fever. The
national livestock information, provided below, is the most recent
available from the USDA. While much of the coumaphos use on livestock
along the border may be in a dip vat application, coumaphos is also used
as a body spray, dust, dust bag, pour-on, oiler scratcher, and ear tag
(USDA/NASS, 2004. Pest Management Strategic Plan for Beef Cattle and
Non-lactating Dairy Cattle - North Central Region).

  -------------- ---------- ----------- -------------- -------------------------
  Table 3.                                             
  Coumaphos                                            
  estimated                                            
  usage on                                             
  Livestock                                            

  Livestock      Year       Total       Application    Rate/Head/Year
                            Applied     Rate           

                            (1,000 lbs) (grams)        (grams)

  All Cattle     1999       58.1        2.3            6.9

                 2006       na          na             na

  Beef Cattle    1999       54.8        2.7            7.4

                 2006       na          na             na

  Dairy Cattle   1999       3.3         0.7            3.1

                 2006       2.3         0.2            7.7

  Sheep          2000       0.63        4              5.8

  References:                                          
  USDA/NASS.                                           
  2000.                                                
  Agricultural                                         
  Chemical Usage                                       
  Cattle and                                           
  Cattle                                               
  Facilities                                           

  USDA/NASS.                                           
  2007.                                                
  Agricultural                                         
  Chemical Usage                                       
  2006 Dairy                                           
  Cattle and                                           
  Dairy                                                
  Facilities                                           
  Summary                                              

  USDA/NASS.                                           
  2001.                                                
  Agricultural                                         
  Chemical Usage                                       
  2001 Sheep and                                       
  Sheep                                                
  Facilities                                           
  -------------- ---------- ----------- -------------- -------------------------

5.  **Environmental Fate Summary**

    1.  **Active Ingredient**

Coumaphos is persistent and moderately mobile to immobile in the soil
environment. It may reach surface water via runoff and dust drift, and
may leach into shallow ground water. The major pathway of coumaphos
degradation appears to be photodegradation in water (half-life 33
hours). Coumaphos is stable to hydrolysis in pH 7, aerobic soil
metabolism, and field dissipation. It appears to be immobile, with K~D~
values ranging from 61 to 298 for parent, and from 91 to 161 for the
degradate chlorferon. During one field dissipation study, its mobility
appeared to be higher than expected from those K~D~ values, which could
be attributed to higher concentrations of spent coumaphos in soil
evaporation pits.

The major coumaphos degradates identified under aerobic conditions were
chlorferon, which reached a maximum of 6.2% of the organosoluble
radioactivity, and 6-hydroxyl-3-methylbenzofuran, the oxygen analog,
which reached a maximum of 0.2% of radioactivity, both recovered at six
months. In addition, the oxygen analog, coumaphoxon, was detected in an
aqueous photodegradation study at a maximum of 10.2% of radioactivity.

The field dissipation study results support the laboratory finding that
coumaphos is persistent. The estimated field dissipation half-lives are
118 and 185 days. Soil samples taken 6 to 12 inches deep contained
coumaphos, however, the soil was not sampled at sufficient depth to
define the extent of leaching. A special retrospective field dissipation
study was conducted to characterize the depth of leaching in disposal
pits and walkways of coumaphos treatment dip vats. On-site disposal of
spent coumaphos in unlined pits was found to result in leaching of
coumaphos, chlorferon, and 40 potasan to the subsurface (72 inches in
the study), and could result in ground-water contamination in areas of
shallow ground water. These compounds may reach ground water, although
there was insufficient depth of soil sampling conducted in the study to
determine if coumaphos and/or its metabolites could have reached the
deep wells that were tested during the study.

Coumaphos is nearly insoluble in water (0.05 mg/l at 25^o^C), and its
vapor pressure of 1x 10^-7^ mm Hg (20^o^C) suggests rather low potential
for volatility from soil and water surfaces. Depending on pH and
concentration the log K~ow~ ranges from 3.85 to 4.04. A supplemental
bioaccumulation in fish study suggests that total coumaphos accumulated,
with a maximum bioconcentration factor of 541X, in whole bluegill
sunfish during 30 days. Accumulated coumaphos residues were depurated
rapidly, with 98% elimination after 1 day in untreated water.

2.  **Coumaphos Degradate**

The residues of concern are coumaphos and its oxygen analog,
coumaphoxon. Coumaphoxon is included in the Health Effects Division
tolerance expression, and was considered in the drinking water
assessment.

Fate and transport data for coumaphoxon are not available. Using a
computer estimation program (EPI version 3.04), the coumaphoxon K~oc~
value was estimated to be 92.3, and water solubility 31.61 mg/l at
25^o^C. It is based on this information assumed that coumaphoxon is
persistent and mobile in the soil environment. Subdivision N aerobic
soil metabolism and batch equilibrium studies are needed for
coumaphoxon. These data are needed to confirm the conservativeness of
those assumptions.

**1.6 Incident Report**

The Agency has received one bird kill that was associated with exposure
to coumaphos. The United States Fish and Wildlife Service reported that
an unknown number of American wigeon were found dead in Washington State
in 1981. The wigeon were in and around ponds adjacent to a feedlot. The
report states coumaphos was the causal agent but did not provide
information on how the chemical was released into the environment.

In 2003, the Minnesota Department of Agriculture submitted to the Agency
a series of eight kills of honey bees that occurred in September, 2002.
In all of these incidents, analysis of bee tissue or pollen, or both,
found residues of coumaphos present. While the source of the coumaphos
exposure was not known, the investigators speculated that the residues
probably resulted from the beekeepers using Checkmite Bee Hive Pest
Control Strips, a coumaphos-containing product that is frequently used
on bee hives to control Vorroa mites. Investigators identified recent
applications of other pesticides, including carbaryl and
zeta-cypermethrin, in nearby agricultural fields, but no clear pattern
emerged in the spatial or temporal pattern of these uses that would
suggest that they were the cause. Furthermore, the residue analysis of
bee tissue and pollen did not detect any carbaryl, zeta-cypermethrin, or
other pesticides. The investigators concluded that insufficient evidence
was available to determine if the exposure to coumaphos played a role in
these bee kills or was merely incidental.

The Agency has received no reports of adverse field effects to plants or
aquatic organisms that have been attributed to the use of coumaphos. The
Agency also has received no incident reports from pesticide registrants
concerning coumaphos contamination of ground or surface water.

A lack of reported incidents does not necessarily mean that such
incidents have not occurred. In addition, incident reports for
non-target plants and animals typically provide information on mortality
events only. Reports for other adverse effects, such as reduced growth
or impaired reproduction, are rarely received (Source: US EPA Coumaphos
incident summary statement for Registration Review; Dated February 20,
2008; Author: Nicholas Mastrota).

5.  **1.7.** **Ecological Effects Summary**

Table 4 provides taxonomic groups and test species typically used to
indicate the potential for ecological effects in screening-level risk
assessments. Within each of these very broad taxonomic groups, an acute
and/or chronic endpoint is selected from the available test data.

+--------------------+------------------------------+-----------------+
| **Table 4.         |                              |                 |
| Taxonomic Groups   |                              |                 |
| and Most Sensitive |                              |                 |
| Test Species       |                              |                 |
| Typically for      |                              |                 |
| Ecological Effects |                              |                 |
| in Screening Level |                              |                 |
| Risk               |                              |                 |
| Assessments.**     |                              |                 |
+====================+==============================+=================+
| **Taxonomic        | **Example(s) of              | **Endpoint      |
| group**            | representative species**     | Used**          |
+--------------------+------------------------------+-----------------+
| Birds^a^           | Bobwhite quail (*Colinus     | Acute,          |
|                    | virginianus*)                | LD~50~/LC~50~   |
|                    |                              |                 |
|                    | Mallard duck (*Anas          | Chronic, NOAEC  |
|                    | platyrhynchos*)              |                 |
+--------------------+------------------------------+-----------------+
| Mammals            | Laboratory rat (*Rattus      | Acute LD~50~    |
|                    | norvegicus*)                 |                 |
|                    |                              | NOAEC           |
+--------------------+------------------------------+-----------------+
| Terrestrial        | Honeybees (*Apis mellifera*) | Acute Oral      |
| insects            |                              | LD~50~          |
+--------------------+------------------------------+-----------------+
| Freshwater fish^b^ | Rainbow trout (*Oncorhynchus | Acute LC~50~    |
|                    | mykiss*)                     |                 |
|                    |                              | Chronic NOAEC   |
|                    | Fathead minnow (*Pimephales  |                 |
|                    | promelas*)                   |                 |
+--------------------+------------------------------+-----------------+
| Freshwater         | Water flea (*carinata*)      | Acute LC~50~    |
| invertebrates      |                              |                 |
|                    | Water flea (*Daphnia magna*) | NOAEC           |
+--------------------+------------------------------+-----------------+
| Estuarine/marine   | Sheepshead minnow            | Acute LC~50~    |
| fish               | (*Cyprinodon variegatus*)    |                 |
+--------------------+------------------------------+-----------------+
| Estuarine/marine   | Mysid shrimp (*Mysidopsis    | Acute LC~50~    |
| invertebrates      | bahia*)                      |                 |
|                    |                              | Acute EC~50~    |
|                    | Eastern oyster (*Crassostrea |                 |
|                    | virginica*)                  |                 |
+--------------------+------------------------------+-----------------+
| Terrestrial plants | Monocots -- N/A              | Seedling        |
|                    |                              | Emergence (Tier |
|                    | Dicots -- N/A                | I or Tier II no |
|                    |                              | EC~25~          |
|                    |                              | estimated)      |
|                    |                              |                 |
|                    |                              | Vegetative      |
|                    |                              | Vigor           |
|                    |                              |                 |
|                    |                              | (Tier I or Tier |
|                    |                              | II no EC~25~    |
|                    |                              |                 |
|                    |                              | estimated)      |
+--------------------+------------------------------+-----------------+
| Freshwater         | Duckweed *(Lemna gibba)*     | Acute EC~25~    |
| vascular aquatic   |                              |                 |
| plants and algae   |                              | NOAEC           |
+--------------------+------------------------------+-----------------+
| Freshwater         | Diatom *(Navicula            | Acute EC~25~    |
| non-vascular       | pelliculosa)*                |                 |
| aquatic plants     |                              | EC~05~          |
+--------------------+------------------------------+-----------------+
| Estuarine/marine   | Diatom *(Skeletonema         | Acute EC~50~    |
| non-vascular       | costatum)*                   |                 |
| aquatic plants     |                              | EC~05~          |
+--------------------+------------------------------+-----------------+

^a^Birds are used as surrogates for terrestrial phase amphibians and
reptiles (US EPA, 2004).

^b^Freshwater fish are used as surrogates for aquatic phase amphibians
(US EPA, 2004).

**1.8. Ecosystems at Risk**

The ecosystems that are predicted to be potentially at risk due to the
use and potentially disposal of coumaphos include: 1) aquatic habitats
in which coumaphos may enter via runoff after a direct application of
bioremendiated vat-dip solution on land and via wash-off from the cattle
hide that may wade in these habitats, and 2) terrestrial ecosystems
where terrestrial animals may come in contact with coumaphos via direct
contact with treated cows, exposure to cow hair with coumaphos residues,
exposure to soil or feed in and around treatment areas, and exposure to
soil on which bioremendiated vat-dip solution was disposed on.

1.  **Receptors**

The aquatic receptors likely to be exposed to coumaphos include fish,
aquatic invertebrates, and aquatic stages of amphibians and plants
inhabiting water bodies that may contain coumaphos washed from treated
cattle wading in these habitats. The sole terrestrial receptors likely
to be exposed to coumaphos are terrestrial animals that may come in
contact with coumaphos via direct contact with treated cows, exposure to
cow hair with coumaphos residues, and exposure to soil or feed in and
around treatment areas.

**1.8.2. Assessment Endpoints**

Assessment endpoints are defined as "explicit expressions of the actual
environmental values that are to be protected." Operationally, the
environmental value is represented by an ecological entity and
associated attributes or characteristics. The assessment endpoints for
this ecological risk assessment will be survival, growth, and
reproduction of aquatic organisms and terrestrial animals that may be
exposed to coumaphos.

Assessment endpoints and toxicity data used to evaluate the assessment
endpoints are identified in Tables 4 and 5.

**1.9. Conceptual Model**

The conceptual model depicts the potential ecological risks associated
with coumaphos uses. The model is generic and assumes that coumaphos can
affect terrestrial and aquatic organisms if environmental concentrations
are sufficiently elevated as a result of coumaphos label uses and
coumaphos disposal. Coumaphos is an insecticide/acaricide used for
external use on animals and animal premises applied as a direct whole
animal or wound treatment to control pests. It can enter the outdoor
environment either as excess material lost during outdoor application,
as material shed, wash off from animals, and during disposal. A diagram
of the conceptual model is presented in Figure 1. The exposure pathway
from disposal of bioremediated vat-dip solution onto land was not
assessed in 1994 EFED's RED Chapter. The disposal of coumaphos
bioremediated dip-vat solution on land maybe equally important for
aquatic and terrestrial exposure as coumaphos washoff into the water
body.

A review of the label provided revealed the following application
restrictions and disposal requirements:

"Do not treat areas such as drinking cups, mangers, or troughs where
livestock feed. Do not contaminate water, food, feedstuff, food or feed
handling equipment, or milk or meat handling equipment."

"The Agency requires that spent dip-vat solution be bioremediated, and
recommends the bioremediation method developed by the USDA. The treated
solution must be transferred to shallow, concrete-lined evaporation
ponds for further degradation. The evaporation ponds must be constructed
to prevent overflow or flooding during wet seasons and must be lined
with reinforced concrete. Dried sludge generated in the evaporation
ponds must not be applied agricultural land and should be disposed
according to solid waste disposal regulations established by your Local
and/or State Environmental Control Agency."

The extent of the exposure can be better understood upon availability of
current coumaphos disposal procedures. There was no mention of the
method of disposal for solution contained within the bioremediation
"evaporation ponds". Two assumptions can be made with regard to the
handling of spent solution. Once in the bioremediation ponds, the level
of solution within the pond is maintained by evaporation and removal and
proper disposal of solids. Alternatively, the liquid is discharged to
water under an NPDES permit or applied to land. Under an NPDES permit,
OPP assumes that precautions have been taken to adequately protect
aquatic life. Because application to agricultural land of a pesticide
product is generally assessed by OPP, therefore, application of
bioremediated coumaphos to agricultural land would be assessed as a
potential exposure pathway.

**Figure 1. Conceptual model of the fate/transport and effects of
coumaphos in the environment.**

**1.10. Risk Hypotheses**

Hypothesis: Non-target terrestrial and aquatic animals and plants are at
risk of direct and indirect effects resulting from labeled uses or/and
disposal of coumaphos.

**1.11. Analysis Plan**

The analysis plan is the final step in the Problem Formulation. During
this step measures of exposure and measures of effect are used to
evaluate the risk hypotheses and are listed in Tables 4 and 5 for a
specific assessment endpoint. The RQ is obtained by dividing the
measures of exposure for a particular assessment endpoint by the
measures of effect for that endpoint.

**1.11.1. Measures of Exposure**

In order to assess exposure to non-target organisms, it is necessary to
have information on the concentration of active ingredient on the hides
of treated cattle, and information on the potential of coumaphos to
wash-off into water when cattle wade into bodies of water. The
registrant has

submitted two studies that address these issues (MRIDs: 42512601 and
42512602). Those studies have been reviewed and found to be acceptable
for use in a risk assessment. Information from those studies will be
incorporated in the registration review risk assessment for both
terrestrial and aquatic non-target organisms.

In addition, current guidance, procedure, or protocols on the
application of the bioremediated vat-dip solution on land are needed. In
previous EFED assessment (D303298), a potential exposure pathway to
bioremediated coumaphos applied to agricultural land was based on
guidance from proposed USDA land farming methods (D230394; D239676,
6/4/98). At that time, uncertainties were associated with the estimated
maximum application rate per acre.

**1.11.2. Measures of Effect**

**[Registrant Submitted Ecotoxicity]{.underline}**

Below is a summary of the ecotoxicity studies submitted by the
registrant.

**Avian Toxicity**

There are nine acceptable avian acute toxicity studies (MRID's 00022923,
112842, and 00160000) and one supplemental simulated field study (Gdln.
71-5; MRID 425126-04). The species tested in the avian acute toxicity
studies include Mallard duck (*Anas platyrhynchos*), Bobwhite quail
(*Colinus virginianus*), Ring-necked pheasant (*Phasianus colchicus*),
and Japanese quail (*Coturnix japonica*). There were 34 species of wild
birds tested in the simulated field study.

The avian acute toxicity studies demonstrated that coumaphos's acute
toxicity to birds ranged from highly to very highly toxic on an acute
oral toxicity basis (acute oral LD~50~ toxicity values ranged from 7.94
ppm - 29.8 ppm), and moderately to very highly toxic on an acute dietary
toxicity basis (acute dietary toxicity values ranged from 85 ppm - 401
ppm).

Based on the Coumaphos 1996 RED document, the Agency concluded that
avian reproduction studies were not required for coumaphos. Such studies
may be required when birds are likely to be exposed to a pesticide
repeatedly or continuously. According to the 1996 RED document's
assessment of acute risk if there were significant coumaphos exposure to
birds, they would be killed before chronic effects could occur.
Currently, there are no available reproductive toxicity studies.

The purpose of the field simulation study was to evaluate the exposure
of wild birds to coumaphos treated cows in an open pen. The field
simulation study was deemed as scientifically sound but did not meet the
requirements for a simulated (pen) field test. The study was classified
as supplemental, because only one study site was used and only 8 cows
were treated. The results indicate that potential pathways of exposure
to birds include direct contact with treated cows, exposure to cow hair,
and exposure to soil or feed in and around treatment areas.

**Mammalian Toxicity**

[]{.mark}

The registrant submitted mammalian ecotoxicity studies testing coumaphos
include a rat acute oral LD~50~ study (MRID 00110597) and a rat two-year
generational reproduction study (MRID 43061701).

The rat acute LD~50~ study demonstrated that coumaphos is highly toxic
to mammals (LD~50~ value of 17 mg/kg). The rat two-year generation
reproduction study demonstrated that cholinesterase inhibition, observed
at 5 and 25 ppm was manifested as dose-related decreases in erythrocyte
(RBC) and plasma cholinesterase (ChE). The RBC ChE was inhibited 31-70%,
relative to concurrent controls, at 5 ppm and 53%-95% at 25 ppm.
Generally, no differences were noted between Day 47 (or 56) and Day 91
ChE levels. Brain levels were biologically significantly inhibited (
30%) in FO and F1 females. In pups, plasma and RBC ChE levels were
inhibited (31%-44%) at 25 ppm on lactation day 21 but not on lactation
day 4. Based on these results, the NOEL and LEL for ChE inhibition were
1 and 5 ppm, respectively. There were no other signs of systemic
toxicity. The NOEL and LEL for systemic toxicity was equal to or greater
than 25 ppm. Reproductive toxicity was not observed in this study.
Consequently, the NOEL for reproductive toxicity was 25 ppm and the LEL
for reproductive toxicity was greater than 25 ppm.

[]{.mark}

[]{.mark}

**Insect toxicity**

[]{.mark}

According to the 1996 RED document for coumaphos, the Agency deemed that
the data requirements for non-target insects testing are not applicable
for the coumaphos use patterns, and no studies were required or
submitted.

**Fish Toxicity**

*Freshwater fish acute toxicity*

There are nine acceptable registrant submitted freshwater fish acute
toxicity studies testing coumaphos, TGAI, (MRID's 40098001, and 112840).
The species tested include

Cutthroat trout (*Oncorhynchus clarki*), Rainbow trout (*Oncorhynchus
mykiss*), Lake trout (*Salvelinus namaycush*), Channel catfish
(*Ictalurus punctatus*), Bluegill sunfish (*Lepomis macrochirus*),
Largemouth bass (*Micropterus salmoides*), and Walleye (*Stizostedion
vitreum v.*).

Based on the results of these studies coumaphos was classified as
moderately toxic to highly toxic to freshwater fish (LC~50~'s range from
0.340 ppm to 5.9 ppm).

*Freshwater fish chronic toxicity*

There is one available freshwater fish early-life stage study using
rainbow trout (*Oncorhynchus mykiss*). The results of this study
demonstrated that chronically exposing the early life-stage of rainbow
trout caused significant effects to growth at a NOEC, and a LOEC of
0.0117 ppm, and 0.0246 ppm, respectively (MRID 43066301).

[]{.mark}

*Marine estuarine fish acute toxicity*

[]{.mark}

There is one registrant submitted marine estuarine fish acute toxicity
test (MRID 40228401) using sheepshead minnow (*Cyprinodon variegates*).
Based on the results of this study, coumaphos is classified as highly
toxic to marine/estuarine fish (LC~50~ = 0.280 ppm).

[]{.mark}

*Marine/ estuarine fish chronic toxicity*

[]{.mark}

Currently, no data have been submitted to the Agency on the chronic
effects of coumaphos to marine/estuarine fish.

[]{.mark}

**Aquatic Invertebrate Toxicity**

*Freshwater invertebrate acute toxicity*

There are six registrant submitted freshwater invertebrate acute
toxicity studies testing coumaphos (MRID's 40098001, 05009242, 05017538,
41778503, and 41778504). These studies test species of water flea and
scud including *Daphnia magna*, *Simocephalus serrulatus*, and *Gammarus
lacustris*. Based on the Agency's review of the studies, three of these
studies were deemed acceptable and three were deemed supplemental. The
results of these studies showed that coumaphos is very highly toxic to
freshwater invertebrates (EC~50~'s range from 0.000074 ppm to 0.000224
ppm).

[]{.mark}

*Freshwater invertebrate chronic toxicity*

There is one registrant submitted freshwater invertebrate chronic
toxicity study (MRID 431166-01). This study is a *Daphnia magna* chronic
toxicity study (Gdln 72-4). Based upon the Agency's review of the study,
the study was deemed as acceptable. This test shows survival as the most
sensitive endpoint. The NOEAC for survival is 0.000037 ppm.

[]{.mark}

*Marine/estuarine invertebrate acute toxicity []{.mark}*

[]{.mark}

There are two registrant submitted marine/estuarine invertebrate acute
toxicity studies testing comaphos's acute toxicity to the pink shrimp
(*Penaeus duorarum*) and eastern oyster (*Crassostrea virginica*). Based
on the Agency's review of these studies, both are deemed as acceptable.
The results of these studies indicate that coumaphos is highly toxic to
very highly toxic to marine estuarine invertebrates (EC~50~ values are
0.002 ppm and 0.290 ppm for the pink shrimp and eastern oyster
respectively). []{.mark}

[]{.mark}

*Marine/estuarine invertebrate chronic toxicity*

[]{.mark}

Currently, there are no marine/estuarine invertebrate chronic toxicity
study data available to the Agency.

[]{.mark}

**Non-target Plant Toxicity**

[]{.mark}

Currently no non-target plant toxicity data have been submitted to the
Agency.

Based on the 1996 RED document for coumaphos, the Agency concluded that
data requirements for non-target plant testing are not applicable for
the coumaphos use patterns, and no studies were required. However the
Agency has currently concluded in this problem formulation that because
cattle with coumaphos treated hides may wade in aquatic water bodies,
the aquatic plants in these water bodies may be exposed to coumaphos
that washes off the hides of these wading cattle. Aquatic plant toxicity
data is needed to evaluate the potential effects that aquatic plants may
experience upon being exposed to coumaphos. The Agency also presumes
that there is a potential that terrestrial plants will be exposed to
coumaphos via the disposal of the dip vat solution. As mentioned in the
Conceptual Model section more information is needed about the method of
disposal of the vat dip solution in order to adequately access the
potential exposure to non-target organisms such as terrestrial plants.

[]{.mark}

[]{.mark}

1.  *Most Sensitive Endpoints of Effects Data*

The following tables 5 and 6 demonstrate the most sensitive endpoints of
all the registrant submitted terrestrial toxicity studies and aquatic
organism toxicity studies respectively. These endpoints will be the
proposed measures of effects that will be used to calculate risk
quotients for the registration review screening level risk assessment of
coumaphos. The proposed measures of effects are however subject to
change based on the results of the Agency's review of coumaphos data
available in the open literature via the ECOTOX database.

+-------------------------+--------------------------------------------+
| **Table 5. Summary of   |                                            |
| terrestrial assessment  |                                            |
| endpoints and proposed  |                                            |
| measures of effects for |                                            |
| the screening level     |                                            |
| risk assessment of      |                                            |
| Coumaphos.**            |                                            |
+=========================+============================================+
| **Assessment Endpoint** | **Measurement Endpoint**                   |
+-------------------------+--------------------------------------------+
| Avian Acute Effects to  | Acute oral LD~50~ = 29.8 mg/kg (MRID       |
| Survival                | 00160000)                                  |
|                         |                                            |
|                         | Acute dietary LC~50~ = 85 ppm (MRID        |
|                         | 112842)                                    |
+-------------------------+--------------------------------------------+
| Avian Chronic Effects   | No data available \*                       |
| to Reproduction,        |                                            |
| Survival, and/or Growth |                                            |
+-------------------------+--------------------------------------------+
| Mammalian Acute Effects | Acute oral LD~50~ 17 mg/kg (MRID 00110597) |
| to Survival             |                                            |
+-------------------------+--------------------------------------------+
| Mammalian Chronic       | NOEAL = 1 ppm (MRID 43061701)              |
| Effects to              |                                            |
| Reproduction, Survival, |                                            |
| and/or Growth           |                                            |
+-------------------------+--------------------------------------------+
| Non-target Beneficial   | No data available \*\*                     |
| Insect Acute Effects to |                                            |
| Survival                |                                            |
+-------------------------+--------------------------------------------+
| Terrestrial Plants      | No data available \*\*\*                   |
| Survival and Growth     |                                            |
+-------------------------+--------------------------------------------+

> \* Note: Based on the Coumaphos 1996 RED document, the Agency
> concluded that avian reproduction studies were not required for
> coumaphos. Such studies may be required when birds are likely to be
> exposed to a pesticide repeatedly or continuously. The assessment of
> acute risk (§A.2.b) indicates that if there were significant exposure
> to birds, they would be killed before chronic effects can occur.
>
> \*\* Note: According to the 1996 RED document for coumaphos, the
> Agency deemed that the data requirements for non-target insects
> testing are not applicable for the coumaphos use patterns, and no
> studies were required or submitted. However, because of the recently
> approved IR4 registration to use coumaphos in honey bee hives to
> control varroa mites and small hive beetles, the Agency will need this
> data to evaluate the potential toxic effects of coumaphos to honey
> bees. This data is needed especially since coumaphos's targeted mode
> of action is to control insect pests. In addition, according to the
> Agency's incident report for coumaphos, there was a bee kill incident
> in which an analysis revealed that the bee's tissue and pollen in this
> incident contained residues of coumaphos. Consequently, the Agency
> needs to determine whether the toxic mode of action will adversely
> affect bees.

\*\*\* Note: Currently no non-target plant toxicity data have been
submitted to the Agency.

> Based on the 1996 RED document for coumaphos, the Agency concluded
> that data requirements for non-target plant testing are not applicable
> for the coumaphos use patterns, and no studies were required.

  -----------------------------------------------------------------------
  **Table 6. Summary of    
  aquatic assessment       
  endpoints and proposed   
  measures of effects for  
  the screening level risk 
  assessment of            
  Coumaphos.**             
  ------------------------ ----------------------------------------------
  **Assessment Endpoint**  **Measurement Endpoint**

  Freshwater Fish Acute    LC~50~ = 280 ppb (MRID 40098001)
  Effects to Survival      

  Freshwater Fish Chronic  NOEAL = 11.7 ppb (MRID 43066301)
  Effects to Reproduction, 
  Survival, and/or Growth  

  Freshwater Invertebrate  LC~50~ = 0.074 ppb (MRID 40098001)
  Acute Effects to         
  Survival                 

  Freshwater Invertebrate  NOEAL = 0.0337 ppb (MRID 431166-01)
  Chronic Effects to       
  Reproduction, Survival,  
  and/or Growth            

  Marine/Estuarine Fish    LC~50~ = 280 ppb (MRID 40228401)
  Acute Effects to         
  Survival                 

  Marine/Estuarine Fish    No data available
  Reproduction and/or      
  Survival                 

  Marine/Estuarine         LC~50~ = 2 ppb (MRID 40228401)
  Invertebrate Survival    

  Marine/Estuarine         No data available
  Invertebrate             
  Reproduction and/or      
  Survival                 

  Aquatic Vascular and     No data available \*
  Non-vascular Plant       
  Survival and Growth      
  -----------------------------------------------------------------------

\* Note: Currently no non-target plant toxicity data have been submitted
to the Agency.

Based on the 1996 RED document for coumaphos, the Agency concluded that
data requirements for non-target plant testing are not applicable for
the coumaphos use patterns, and no studies were required. However the
Agency has currently concluded in this problem formulation that because
cattle with coumaphos treated hides may wade in aquatic water bodies,
the aquatic plants in these water bodies will be exposed to coumaphos
that washes off the hides of these wading cattle. Aquatic plant toxicity
data is needed to evaluate the potential effects that aquatic plants may
experience upon being exposed to coumaphos.

> **1.11.3. Preliminary Identification of Data Gaps for Fate and
> Ecological Assessment**

Environmental fate and transport data for coumaphos are mostly
supplemental; however, support a qualitative characterization of the
properties of coumaphos in the environment. The only missing laboratory
studies are anaerobic soil metabolism study (162-2), aerobic and
anaerobic aquatic metabolism studies (162-3, 162-4). The missing
laboratory studies would be beneficial for a better characterization of
the potential for coumaphos leaching to ground water or remaining in
surface water at concentrations of ecological or human health concern;
however they will not adversely effect the risk conclusions as presented
in the 2004 Screening Level Aquatic Exposure Assessment for the Use of
Coumaphos in the Pacific Northwest and California, nor in the 1996 RED.

In addition, there are no environmental fate data for the coumaphoxon.
Coumaphoxon, oxygen analog of coumaphos, was detected in an aqueous
photodegradation study at a maximum of 10.2% of applied radioactivity.
Coumaphoxon is coumaphos' degradate of concern due to its toxicity being
greater than the toxicity of parent. Therefore, Subdivision N aerobic
soil metabolism and batch equilibrium studies are proposed to be
requested for coumaphoxon.

Table 7, below, identifies fate and ecological studies, which are
missing or are not acceptable, and may be requested to assess risk to
the environment. Coumaphos is an insecticide/acaricide used for external
use on animals and animal premises applied as a direct whole animal or
wound treatment to control pests. It can enter the outdoor environment
either as excess material lost during outdoor application, as material
shed, washoff from animals, and during disposal. The extent of exposure
from bioremediated spent vat-dip solution can be better understood upon
availability of current coumaphos disposal procedure/techniques. If
proven that these routes of expose are minimal or none, the fate studies
for coumaphoxon would be waived.

  ---------------- --------------- ---------------- -------------------------
  **Table 7.                                        
  Preliminary                                       
  Identification                                    
  of Data Gaps for                                  
  Fate and                                          
  Ecological                                        
  Assessment**.                                     

  **Fate and       **Description   **Projected      **Basis for decision**
  Ecological Taxa  of studies**    status of data   
  studies**                        gaps**           

  Aquatic plant    Parent -- Study Proposed to      Refer to information
  toxicity studies was not         request the      provided below
  for guideline    submitted       study            
  850.4400 and                                      
  850.5400                                          

  Anaerobic soil   Parent - Study  Study not        
  metabolism study was not         requested        
                   submitted                        

  Aerobic aquatic  Parent - Study  Study not        
  metabolism study was not         requested        
                   submitted                        

  Anaerobic        Parent - Study  Study not        It will characterize the
  aquatic          was not         requested        potential for coumaphos
  metabolism study submitted       Registrant       leaching to ground water
                                   requested a      or remaining in surface
                                   waiver. Waiver   water. If current
                                   was granted      disposal protocol
                                   under the        fulfills the waiver
                                   condition that   requirement the study is
                                   disposed spent   not needed.
                                   vat-dip on land  
                                   will not exceed  
                                   concentration of 
                                   0.01 ppm in the  
                                   top 6" soil.     

  Aerobic soil     Oxon analog -   Proposed to      To confirm the computer
  metabolism study Study was not   request the      estimated (EPI v. 3.04)
                   submitted       study            DW modeling parameter.

  Batch            Oxon analog -   Proposed to      To confirm the computer
  equilibrium      Study was not   request the      estimated (EPI v. 3.04)
  study            submitted       study            DW modeling parameter.
  ---------------- --------------- ---------------- -------------------------

+-----------------------------------------------------------------------+
| **Fate Data Gaps**                                                    |
|                                                                       |
| **Guideline Number: 835.4100**                                        |
|                                                                       |
| **Study Title: Aerobic Soil Metabolism (Oxygen Analog)**              |
|                                                                       |
| **Guideline Number: 835.1220**                                        |
|                                                                       |
| **Study Title: Batch Equilibrium (Oxygen Analog)**                    |
+-----------------------------------------------------------------------+
| **Rationale for Requiring the Environmental Fate Studies Performed in |
| the Laboratory**                                                      |
+-----------------------------------------------------------------------+
| Depending on how quickly and to what extent coumaphoxon degrades in   |
| soil, and to what extent it is mobile; coumaphoxon may or may not     |
| contribute to ground water and surface water contamination from       |
| cattle washoff and/or disposal of bioremediated spent vat-dip onto    |
| land.                                                                 |
|                                                                       |
| EPA requires a series of individual laboratory studies as well as     |
| field studies to assess the behavior and fate of a pesticide in the   |
| environment. Controlled environmental fate and transport laboratory   |
| studies are used to determine the persistence, mobility, and          |
| bioconcentration potential of a pesticide active ingredient and its   |
| major degradates. Coumaphoxon, coumaphos' oxygen analog, is a         |
| degradate of concern, and therefore one metabolism study and one      |
| mobility study are requested to provide the minimum information on    |
| fate and transport of this degradate. The studies offer information   |
| on how, or by what mechanism, the pesticide degrades, the rate at     |
| which it degradates, where it goes, and what transformation products  |
| are formed. Data from these studies are used as inputs to exposure    |
| models. These models estimate the expected environmental              |
| concentrations of the pesticide and the pesticide's degradates under  |
| various environmental and use conditions. The laboratory studies also |
| help to focus field study design by providing information on which    |
| transformation products are likely to be produced, and thus need to   |
| be tracked, and the environmental media (e.g., soil, sediment, water, |
| air) that should be sampled, including the depth to which             |
| soil/sediment samples should be collected.                            |
|                                                                       |
| The soil microbial metabolism study determines the persistence of the |
| pesticide, in this case its oxygen analog, when it interacts with     |
| soil microorganisms under aerobic conditions. These studies also      |
| identify the significant degradates that result from biological       |
| degradation.                                                          |
|                                                                       |
| The batch equilibrium study determines the mobility of the pesticide  |
| or degradate in soil, the potential to leach into the shallow         |
| groundwater or its availability to surface runoff following rainfall  |
| events.                                                               |
+-----------------------------------------------------------------------+
| **Practical Utility of the Data**                                     |
+-----------------------------------------------------------------------+
| **How will the data be used?**                                        |
|                                                                       |
| -   The **soil metabolism studies** would facilitate a better         |
|     understanding of coumaphos' oxygen analog degradation under       |
|     aerobic (oxygen-rich) conditions in the laboratory, and as an     |
|     input parameter for drinking water modeling and aquatic modeling. |
|                                                                       |
| ```{=html}                                                            |
| <!-- -->                                                              |
| ```                                                                   |
| -   The **batch equilibrium study** would facilitate a better         |
|     understanding of coumaphos' oxygen analog mobility in soil in the |
|     laboratory, and as an input parameter for drinking water modeling |
|     and aquatic modeling.                                             |
|                                                                       |
| -   The soil metabolism studies help to determine how fast the oxygen |
|     analog (coumaphoxon) degrades in the presence of microorganisms   |
|     in different natural soils. They also determine what metabolites  |
|     are formed.                                                       |
|                                                                       |
| **How could the data change the Agency's decision, or impact the      |
| Agency's future decision-making?**                                    |
|                                                                       |
| If data indicate that coumaphoxon degrades slowly in soil, and is     |
| mobile, then coumaphos usage on cattle and/or disposal of             |
| bioremediated cattle dip solution may pose risk to aquatic organisms, |
| and additional use/disposal precautions and/or restrictions may be    |
| necessary.                                                            |
+-----------------------------------------------------------------------+
| **Ecological Toxicity Data Gaps**                                     |
|                                                                       |
| **Guideline Number: 850.4400 (Aquatic Plant Toxicity Test, Tier 1)**  |
|                                                                       |
| **Guideline Number: 850.5400 (Study Title: Algal Toxicity, Tier I)**  |
+-----------------------------------------------------------------------+
| **Rationale for Requiring the Aquatic Plant and Algal Toxicity        |
| Studies**                                                             |
+-----------------------------------------------------------------------+
| Cattle often wade in aquatic water bodies that are located in and     |
| around their pastures. Thus, if cattle with coumaphos treated hides   |
| wade in these water bodies, the aquatic plant and algal inhabitants   |
| of these ecosystems may be exposed to coumaphos that washes off the   |
| hides of these cattle. Currently, there are no aquatic plant or algal |
| toxicity data testing coumaphos that have either been submitted by    |
| the registrant or are available in the open literature. Thus, in      |
| accordance with the 40 Code of Federal Regulations Part 158 aquatic   |
| plant and algal toxicity data for coumaphos are required. In addition |
| based on the Agency's TOXDATA database, very little data are          |
| available which evaluate the toxic effects of other organophosphate   |
| pesticides on aquatic plants and algae. Consequently, the Agency is   |
| very uncertain of the effects that coumaphos may have on aquatic      |
| plants and algae. However, based on available organophosphate aquatic |
| plant and algal toxicity data, naled, an organophosphate insecticide  |
| such as coumaphos, demonstrates significant acute toxicity to algae   |
| and aquatic plants at EC~50~ values as low as 12 ppb (MRID 42529603). |
| Moreover according to an assessment (\"Coumaphos Analysis of Risks to |
| Endangered and Threatened Salmon and Steelhead\", August 1, 2004 by   |
| Jennifer Leyhe) presenting a crude estimation of level of exposure    |
| from loss of coumaphos applied to cattle wading into surface water,   |
| the estimated environmental concentration (EEC) from one cow was      |
| estimated at 0.15 ppb, assuming 50% was wash-off. Thus assuming that  |
| 100 cows would wade in the same water, the EEC would be 15 ppb. This  |
| level of exposure is within the range at which naled caused           |
| significant acute toxic effects to aquatic plants and algae.          |
| Therefore, in order to address the uncertainty regarding the toxic    |
| effects of coumaphos to aquatic plants and algae, the Agency must     |
| obtain aquatic plant and algal toxicity data. This is especially      |
| important considering that 1) aquatic plants and algae may            |
| potentially be exposed to coumaphos concentrations that are within    |
| the range of naled concentrations that cause significant aquatic      |
| plant and algal toxicity, 2) coumaphos may possibly have similar      |
| aquatic plant and algal toxicity to naled because the two chemicals   |
| are in the same chemical class, and 3) aquatic plants and algae are a |
| critical element of healthy aquatic ecosystem, and thus it is very    |
| important to evaluate the potential impact that coumaphos may have on |
| them.                                                                 |
+-----------------------------------------------------------------------+
| **How did the Agency make their decision without the data?**          |
|                                                                       |
| According to the Coumaphos 2006 RED document, the Agency initially    |
| presumed that the registered uses would result in minimal coumaphos   |
| exposure to plants. Consequently, the Agency concluded that no plant  |
| or algal toxicity data were required for coumaphos. The Agency also   |
| presumed in the 2006 RED document that the primary non-target         |
| organisms that would be exposed to coumaphos would include 1) aquatic |
| invertebrates and fish inhabiting water bodies that may encounter     |
| wading cattle with coumaphos treated hides and 2) birds that may be   |
| exposed to coumaphos via direct contact with the hides of coumaphos   |
| treated cattle. However, based upon the Agency's current review of    |
| the registered uses of coumaphos, the Agency has determined that      |
| coumaphos treated cattle that wade in aquatic habitat will also       |
| result in aquatic plant and algal exposure to coumaphos.              |
|                                                                       |
| **How will the data be used?**                                        |
|                                                                       |
| The Agency will use the data to calculate risk quotient calculations  |
| that will determine whether or not aquatic plants or algae exposed to |
| the estimated environmental concentrations of coumaphos are at risk   |
| above the Agency's level of concern. If the risk quotient             |
| calculations from this data demonstrate risk to aquatic plants or     |
| algae that exceed the Agency's level of concern, this data may also   |
| be used to help the Agency to determine a means of mitigating this    |
| risk.                                                                 |
|                                                                       |
| **How could the data change the Agency's decision, or impact the      |
| Agency's future decision-making?**                                    |
|                                                                       |
| If the data reveals that coumaphos poses adverse risks to aquatic     |
| plants or algae that exceed the Agency's level of concern, the Agency |
| may make a decision to mitigate the usage of coumaphos to alleviate   |
| the risks posed to aquatic plants or algae.                           |
+-----------------------------------------------------------------------+

*1.11.3.1 Other Informational Needs*

There is specific information that will assist the Agency in refining
the ecological risk assessment, including any species-specific effects
determinations. The Agency is very much interested in obtaining the
following information:

1.  any current information pertaining to disposal of bioremediated
    cattle dip spent solution (i.e. dried sludge generated in the
    evaporation ponds)

2.  confirmation on the following label information

    a.  sites of application

    b.  formulations

    c.  application methods and equipment

    d.  maximum application rates

    e.  frequency of application, application intervals, and maximum
        number of applications per season

    f.  geographic limitations on use

3.  use or potential use distribution (e.g., acreage and geographical
    distribution of relevant crops)

4.  use history

5.  median and 90^th^ percentile reported use rates (lbs. a.i./acre)
    from usage data -- national, state, and county

6.  application timing (date of first application and application
    intervals) by crop -- national, state, and county

7.  sub-county crop location data

8.  usage/use information for non-agricultural uses (e.g., forestry,
    residential, rights-of-way)

9.  directly acquired county-level usage data (not derived from state
    level data)

    a.  maximum reported use rate (lbs. a.i./acre) from usage data --
        county

    b.  percent crop treated -- county

    c.  median and 90^th^ percentile number of applications -- county

    d.  total pounds per year -- county

    e.  the year the pesticide was last used in the county/sub-county
        area

    f.  the years in which the pesticide was applied in the
        county/sub-county area

10. typical interval (days)

11. state or local use restrictions

12. ecological incidents (non-target plant damage and avian, fish,
    reptilian, amphibian and mammalian mortalities) not already reported
    to the Agency

13. monitoring data

The analysis plan will be revisited and potentially revised depending
upon the data available in the open literature and the information
submitted by the public in response to the opening of the Registration
Review docket.

**1.12. Open Literature**

No open literature fate studies have been found that might provide
useful information in the areas of previously discussed data gaps.

In regards to ecotoxicity data, the Agency uses the ECOTOX database as
its mechanism for searching the open literature for ecological effects
information. ECOTOX integrates three previously independent databases -
AQUIRE, PHYTOTOX, and TERRETOX - into a system which includes toxicity
data derived predominately from the peer-reviewed literature, for
aquatic life, terrestrial plants, and terrestrial wildlife,
respectively. Endpoints from ECOTOX are used to calculate risk quotients
for non-target organisms only if these endpoints are acceptable and are
more sensitive than the most sensitive endpoints produced by the
registrant submitted studies. Currently, the Agency's ECOTOX database
search for coumaphos open literature data is pending completion.

13. **Residues of Coumaphos and Coumaphos Degradates in Water**

Submitted fate and transport data suggest that coumaphos is persistent
and moderately mobile to immobile. If applied to soil coumaphos may
potentially drift off or runoff into surface water, and leach into
shallow ground water. Although, no data were submitted for coumaphoxon,
it is assumed that this degradate of coumaphos is also persistent and
mobile, thus, may potentially runoff into surface water and leach into
ground water resources. In shallow clear waters with good light
penetration, coumaphos will rapidly form coumaphoxon.

Coumaphos waste product, after being bioremediated, could be applied
directly to soils where it would be available for leaching into ground
water, or for direct runoff following a runoff producing rainfall event.
In addition, there is a potential environmental exposure from spray
applications to cattle that subsequently wade into surface water where
material is washed off from direct contact with water, and during rain
events.

On June 6, 2000 EFED provided an estimate of the potential coumaphos and
coumaphoxon environmental exposures from the disposal of bioremediated
vat-dip solution for an FQPA assessment (DP266513). At that time, the
exposure pathway associated with the application of coumaphos to cattle
via spray, that may be equally as important for drinking water
assessment, was not assessed.

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No drinking water concerns exist for coumaphos used in beehives within
the honeybee colony in accordance with the coumaphos product label. The
use of coumaphos impregnated strips, CheckMite+^®^ Pest Control Strip,
within a beehive structure effectively eliminates pathways of exposure
to surface and ground water.

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