### UNITED STATES ENVIRONMENTAL PROT E CTION AG E NCY



### W AS I--I fNGTON D

. C

. , 20460

PC Code: 086002

DP Barcode: 426576

Date: 12 / 8

/ 2015



## MEMORANDUM

Subject:

To :

From :

Reviewed:

Throu g h: 

### Registration Review -Preliminar y Problem Formulation fo r Ecological Risk

, Environmenta l Fate

, and Drinking Water Assessmen t s for Warfarin.

Cait lin Newcam p , C h em ical Review Ma na ge r Nei l Ande r son , Branch Ch i ef

Ri s k Management and Implement at ion Branch I

Pe st icide Re-evaluation Di vision (7508 P)

Office of P est i c i de Pro gra ms

Elizabeth Dono van , M.S. Bio l ogist 

# 2.J1---**~** I brahim Abdel-Saheb

, Ph.D.

, Chemist

## ~-**~~** Environmental Ri sk Branch 6

Env i ronmental F ate and Effects Divi s i on (7507P)

Office of P est icide Programs

Michael Wagman

, Biologist 

# Jii/ #**~~** 

# .. ,**~** 

# / 

# 0

William Eckel

, Ph.D.

, Senior

# sl~ce**A~sor V~f** **~** Mon i ca Wait

, RAPL**~** 

## W**~** 

## \ 2-/ &'" /\ 

### 5 

### Env i ronmental Risk Branch 6

Environmental Fate and Effec ts Divi s i o n (7507)

Office of Pestic id e Pro grams

Mark Co r bin

, Branch Ch i ef

Env i ronmental Ri s k Bra n ch 6

E nvironm en tal Fate and Effects Divisi o n (7507)

Office of P estic ide Program s

The Environ m e ntal Fate and Effects Di v i s i o n (EFED) has completed the preliminary problem

formulat i on for the eco l ogical risk

, environme ntal fate

, and drinking water assessments to b e conducted as part of the r eg i strat ion review of the rodent i c id e warfarin.

T h e prob l em fonnulation draws on informat i on from both o p en li tera tur e and st udi es submitted

b y the tec hnic a l registrants. This document is intended to provide an overview of what is currently known r e ga r ding th e e n v ir onmenta l fate and eco lo g ic a l effects associated w i th warfar in

P

age 1 of 51

### Page 2 of 51 

### and outlines uncertainties regarding attributes of the parent compound and its transformation products . It describes the preliminary ecological risk hypothesis and the processes that will be used during the completion of drinking water and ecological risk assessments in support of registrati on review

. This document also recommends studies that should be included in a data
call

- in (DCI) to address uncertainties surrounding the environmental fate and potential ecolog ical
effects of warfarin

.

### Page 3 of 51 

# Preliminary Problem Formulation for the Environmental Fate and Ecological Risk , Endangered Species
, a nd Drinking

Water Assessment s in Support of the R eg istration Review of
Warfarin

Warfarin
4

- hydroxy

- 3

- (3

- oxo
- 1

- phenylbutyl)chromen

- 2

- one (CAS 81

- 81

- 2) (PC Code 086002)

Environmental Risk Branch V I Environmental Fate and Effects Division
Elizabeth Donovan

, M.S., Biologist
Ibrahim Abdel

- Saheb , Ph.D. Environmental Scientist

Reviewed by: Michael Wagman

, Biologist William Eckel, Ph.D., Senior Science Advisor
Monica Wait

, RAPL
Mark Corbin , Branch Chief U. S. Environmental Protection Agency Office of Pesticide Programs 1200 Pennsylvania Ave., NW
Mail Code 7507P Washington, DC 20460

### Page 4 of 51 

### Table of Contents

1 Executive summary

................................ ................................ ................................ ................. 5

2 Introduction

................................ ................................ ................................ ............................. 5
3 Use Characterization

................................ ................................ ................................ ............... 6
4 Conc lusions from Previous Risk Assessments

................................ ................................ ....... 7
4.1 Endangered Species Assessments

................................ ................................ ........ 7
4.2 Reregistration Eligibility Decision

................................ ................................ ....... 7
4.3 Drinking water assessment

................................ ................................ ................... 8
5 Environmental Fate and Transport

................................ ................................ .......................... 9
5.1 Transformation Products

................................ ................................ .................... 10
6 Receptors

................................ ................................ ................................ ............................... 10
6.1 Toxicity Summary

................................ ................................ .............................. 10
6.2 Secondary Toxicity

................................ ................................ ............................ 12
6.3 Incident Database Review

................................ ................................ .................. 15

7 Exposure Pathways of Concern

................................ ................................ ............................ 16
8 Analysis Plan

................................ ................................ ................................ ........................ 16
8.1 Stressors of Concern

................................ ................................ ........................... 16
8.2 Measures of Exposure

................................ ................................ ........................ 17
8.3 Measures of Effect

................................ ................................ ............................. 24

9 Endangered Species Assessment

................................ ................................ .......................... 24
10 Endocrine Disruptor Screening Program

................................ ................................ .............. 25

11 Preliminary Identification of Data Gaps

................................ ................................ ............... 25

11.1 Fate

................................ ................................ ................................ ..................... 25

11.2 Effects

................................ ................................ ................................ ................. 27

12 References

................................ ................................ ................................ ............................. 32 Appendix A: Su mmary of Ecotoxicity Data for Warfarin

................................ ............................ 43 Appendix B. Screening Level Models to Evaluate Potential Importance of Drinking Water a nd Inhalation Exposure Pathways

................................ ................................ ................................ ...... 48 Appendix D. Wildlife Mortality Incidents Attributed to Use of Warfarin

................................ .. 51

### Page 5 of 51 

# 1 Executive summary

The Environmental Fate and Effects Division (EFED) has completed the preliminary problem formulation for the ecological risk, environmental fate, and drinking water assessments to be conducted as part of the registration review of warfarin . The problem formulation describes the methods planned to be used dur ing the completion of drinking water and ecological risk assessments in support of registration review and provides an overview of the environmental fate, ecological effects, and potential risks associated with the use of warfarin as well as
uncertainties unique to risk assessment of warfarin

. This document also identifies additional studies that would be beneficial to the conduct of an ecological risk assessment.

Data needs for ecological effects are:

• Avian acute oral toxicity test (850.2100), one passerine species

• Avian reproduction toxicity (850.2300), for an upland game bird ( e.g., bobwhite quail ( Colinus virginianus )) and waterfowl species ( e.g., mallard duck ( Anas platyrhynchos ))

.

• Earthworm Subchronic Toxicity Test (850.3100), one species

.

Dat a needs for environmental fate are :

• Environmental Chemistry Method s and Associated Independent Laboratory Validations : Water & Soil (850.6100)



# 2 Introduction

Warfarin is a first generation coumarin anticoagulant rodenticide

. It uncouple s oxidative phosphorylation depressing hepatic synthesis of prothrombin and clotting factors VII, IX and X

an d cause direct damage to capillary permeability. The ultimate effect is widespread internal hemorrhage (World Health Organization, 2010). The warfa rin chemical case historically included both warfarin (PC code 086002) and its sodium salt (PC code 086003), but there are currently no active products registered under the sodium salt.

Anticoagulants are vitamin

- K antagonists that disrupt normal blood

- cl otting mechanisms and induce capillary damage. Typically, death is delayed for four to ten or more days after a lethal dose is ingested, and animals may continue to feed and move about until shortly before death. Death results from hemorrhage, and expose d animals may exhibit behavior that may make them more susceptible to predation (Cox and Smith, 1992). This may result in secondary exposure to predatory animals. Warfarin is metabolized by vertebrate animals that have eaten bait, but some is sequestered in various body tissues for days or weeks. First generation anticoagulants tend to be less toxic and persistent in biological tissue than second generation anticoagulant rodenticides and usually require several days of consecutive feedings to deliver a le thal dose

.

EFED evaluated the most recent ecological risk assessments for warfarin in association with the updated toxicity, exposure, and usage information to determine if sufficient data are available and if further updates are needed to support registr ation review. In addition, EFED considered

### Page 6 of 51 

### the latest Agency science policies and risk assessment methodologies. The structure of warfarin
and its sodium salt , as well as the chemical names and other identifiers can be found in the chemical identity tabl e in Section 5 of this document.



# 3 Use Characterization

T here is no national level usage data for for warfarin ( 086002 )

. Table 1 lists the maximum use
patterns (application rates, number of reapplications, etc.) for the labeled use sites for warfarin.
The table is based on the Label Us ag e Report Package created by the Biological and Economics Analysis Division ( BEAD ) in support of Registration Review (USEPA, 2015).

There ar e currently 23 Section 3 labels for warfarin. Warfarin is formulated as gra nules, pellets/tablets, microencapsulated pellets and gel solution. The target pests include: Norway rat ( Rattus norvegicus ), black rat ( R. rattus ), house mouse ( Mus musculus ), meadow vole ( Microtus pennsylvanicus ), pine vole ( M. pinetorum ), montane vole ( M. montanus), Eastern mole ( Scalopus aquaticus ), star

- nosed mole ( Condylura cristata ), hairy

- tailed mole ( Parascalops
breweri ), coast mole ( Scapanus orarius ), broad

- footed mole ( S. latimanus ), Townsend’s mole ( S.
towsendii ), and deer and white

- footed mouse ( P eromyscus spp.). Concentrations in bait are
0.025% warfarin.

Table 1. Label Use Information for warfarin based on BEAD’s summary report

Use Single Max Application Rate Application

Methods

Agricultural/Farm Premises; Agricultural/Farm Structures/Buildings and Equipment; Airports/Landing Fields; Commercial/Institutional/Industrial/Equipment (Indoor); Commercial/Institutional/Industrial/Equipment (Outdoor); Commercial/Transportation Facilities

- Nonfeed/Nonfood; Household/Domestic Dwellings ; Household/Domestic Dwellings Indoor Premises; Household/Domestic Dwellings Outdoor Premises; Nonagricultural Outdoor Buildings/Structures; Public Buildings/Structures (Vert. Pest Control); Ships and Boats 0.00025 lb/placement Bait station/ By hand

Animal Burrows, Harborages or Dens of Plague Reservoir hosts 0.00025 lb/placement Bait station/ Gel syringe/ By hand Automobiles, Taxis, Limousines, Recreational Vehicles, & Tires; Commercial/Institutional/Industrial floors; Commercial Transportation
Vehi cles (All or Unspecified); Railroad Boxcars; Wide Area/General Indoor Treatment; Wide Area/General Outdoor Treatment (Public Health use) 0.00025 lb/placement Bait station

Golf Course Turf; Ornamental Lawns and Turf 0.00021 lb/placement Bait station/
Gel s yringe

### Page 7 of 51 

# 4 Conclusions from Previous Risk Assessments

The Agency has conducted previous ecological risk assessments on warfarin that serve as a basis for this problem formulation. They are briefly summarized below.



## 4.1 Endangered Species Assessments

An endangered species risk assessment for San Fran c isco Bay Species was completed for
warfarin in 2011 (USEPA 2011) to address potential risk to the Salt marsh harvest mouse (SMHM) ( Reithrodontomys raviventris ), and Alameda Whipsnake (AW) ( Masticophis late ralis euryxanthus ) for which warfarin was alleged to be of concern in a complaint made by the Center for Biological Diversity against United States Environmental Protection Agency on May 30, 2007 (Case No: 07

- 2794

- JCS)

. Based on the best available informat ion, the Agency made a

“ May Affect, and Likely to Adversely Affect” determination for the SMHM and AW from the
uses of warfarin . Additionally, the Agency determined that there was the potential for modification of designated critical habitat for the AW fr om the use of warfarin

.



## 4.2 Reregistration Eligibility Decision

The Reregistration Eligibility Decision (RED) for warfarin was published in 199 1 (USEPA,
199 1 ). The RED found that all uses of warfarin were eligible for reregistration with additional
restricti ons, such as expanded label language regarding use of protective bait stations, consistent label formats for residential use patterns, and restricted use of the 1% tracking powder
formulations.



## 4.3 Comparative Risk Assessment

“Potential Risks of Nine Rodenticides to Birds and Nontarget Mammals: a Co mparative Approach” (USEPA 2004 ) evaluated primary and secondary exposure of warfarin , among other rodenticides, to birds and mammals. Th e assessment determined that the greatest risk of
warfarin use to non

- target animals is via primary and secondary exposure to mammals. Risk associated with primary and secondary exposure to birds is not of concern. The 2004 assessment also specified a number of factors contributing to uncertainty in assessing anticoagulan t rodenticides. Those factors that contributed the most uncertainty were: (1) missing data, including acute, chronic, and secondary toxicity as well as data regarding retention of some active ingredients in the liver, blood, and other body tissues; (2) th e variable quality and quantity of existing data on metabolism and retention times in rodents and non

- target species; (3) specific use information by formulation, including typical amounts applied by use site, seasonally, and annually; distances applied fr om buildings; amounts used in rural versus urban areas; use by Certified Applicators versus homeowners and other non

- certified applicators; and other such relevant information; (4) information on the number and species of birds and non

- target mammals frequ enting baited areas and the likelihood of their finding and consuming bait or poisoned primary consumers in the various use areas; (5) methods to determine liver concentration(s) and total body burdens of rodenticide that would corroborate death or even if

### Page 8 of 51 

### such a cause

- effect relationship is appropriate (e.g., the “threshold of toxicity” concentration); (6) not accounting for the impacts of sub

- lethal effects on reproduction and non

- target mortality (e.g., clotting abnormalities, hemorrhaging, stress factor s including environmental stressors, such as adverse weather conditions, food shortages, and predation); (7) not accounting for bioaccumulation of repeated sub

- lethal exposures to bait or poisoned rodents utilized as food by predators and scavengers; and ( 8) lack of incident reporting.



## 4.4 Risk Mitigation Decision and Notice of Intent to Cancel

In 2008, EPA released the Risk Mitigation Decision for Ten Rodenticides (RMD) (EPA 2008,
Docket ID EPA

- HQ

- OPP

- 2006

- 0955 at www.regulations.gov ). Warfarin products we re included
in the list of ten rodenticides addressed in the 2008 document. The focus of th e decision was:

1) T o minimize children’s exposure to rodenticide products used in homes by requiring that all rodenticide bait products marketed to general and residential consumers be sold only with bait stations, with loose bait (e.g., pellets and meal) as a prohibited bai t
form. 2) To reduce wildlife exposures and ecological risks, by requiring sale and distribution limits intended to prevent general consumers from purchasing residential use bait products containing four of the ten rodenticides that pose the greatest risk to wildlife (the second generation anticoagulants

– brodifacoum, bromadiolone, difenacoum, and difethialone). Moreover, bait stations will be required for all outdoor, above

- ground uses of these second generation anticoagulants.

EPA updated its previous ris k assessment findings conducted in support of the May 2008 RMD through the application of additional effects and exposure data, use of additional exposure modeling, and quantitative risk assessment techniques for the four rodenticides subject to the
Notice of Intent to Cancel (NOIC) (brodifacoum, difethialone, warfarin and bromethalin) and for two rodenticides that are likely alternatives (i.e., active ingredients included in products with

RMD

- compliant registrations for commensal rodent control, specifical ly, chlorophacinone and
warfarin ; bromethalin has both compliant and non

- compliant registrations). To support the NOIC, EPA conducted an extensive assessment of the potential for primary and secondary
effects of the rodenticides under evaluation. This wor k was brought before the Science Advisory Panel (SAP) in 2011 for review; meeting materials are available under docket number EPA

- HQ

OPP

- 2011

- 0718 at www.regulations.gov

.



## 4.5 Drinking W ater A ssessment s

Warfarin is applied as a bait ; it tends to bind to organic matter, and little is expected to partition
or runoff into drinking water sources; therefore, this route of exposure was not assessed during reregistration

. D ue to the limited use pattern (bait applications only) and the relatively low environmental exposure of warfarin, no drinking water assessment is anticipated during registration review unless use rate s increase significantly or if a new use is proposed in the
future.

### Page 9 of 51 

# 5 Environmental Fate and Transport

Table 2 summari zes the physicochemical properties of warfarin based on data available in open literature. Warfarin is considered moderately mobile in the environment (based on FAO 2000 mobility classification) and persistent in groundwater (USEPA, 2006). Volatilization from moist soil surfaces is not expected to be an important route of dissipation given an estimated Henry's
Law constant of 2.8 X 10

- 9 atm

- cu m/mole. Wafarin in soluble (17 mg/L). If released into water, warfarin is expected to adsorb to suspended solids and sediment based upon the Koc. Volatilization from water surfaces is not expected to be an important route of dissipation based upon this compound's estimated Henry's Law constant. An estimated bioconcentration factor ( BCF ) of 24x suggests a low poten tial for bioconcentration in aquatic organisms. With respect to abiotic routes of degradation, warfarin is stable to hydrolysis with a half

- life (pH 7, 25 °C) of 16 years (Hazardous Substances Data Bank, HSDB).

Warfarin absorbs UV radiation to approximat ely 330 nm (Gore et al., 1971) and may therefore be susceptible to direct photolysis in the environment; however, no data were found concerning the possible photolysis rate.

With respect to biotic routes of degradation, warfarin (sodium salt) was consider ed stable with only13% degradation over a 28

- day incubation period using activated sludge (Brorson et al., 1994).

Warfarin was not detected (detection limit of 0.001 ppb) in the 84 water samples which were analyzed (Kolpin et al., 2002).

In California, g roundwater samples were collected from 1231 sites between May 2004 and March 2010 and analyzed for a broad suite of water quality constituents, including pharmaceutical compounds (warfarin included). The sites were located in 28 study units that represent a reasonably complete sampling of the range of hydrogeologic conditions and land

- use patterns encountered in
California. Seven compounds were not detected in groundwater samples in this study: albuterol, cotinine; dehydronifedipine, diltiazem, diphenhydra mine, thiabendazole, and warfarin ( Miranda and
Belitz, 2011 

### )

.

### Page 10 of 51 Table 2 . Physical

- chemical Properties of Warfarin

Study Value and units Source

CAS Number 81

- 81

- 2 ASTER

SMILES Code c(ccc1C(O)=C2C(

- c(ccc3)cc3)CC(=O)C)cc1OC2=O ASTER

Molecular weight 308.33 ASTER Hydrolysis 16 years (pH 7, 25 o C) Ellington 1989 Solubility 17 mg/L at 20 o C Tomlin (ed.). 1997 Biodegradation Not readily biodegradable with only a 13% degradation (COD reduction) over a 28

- day incubation period. Warfarin is reduced by
Nocardia and Arthrobacter s p

p

. to the alcohol. Brorson et al . (1982)

Organic carbon Partition Coefficient (K
oc ) 701 

### L/kg oc (estimated) Lyman et al ., 1990 Based on measured log

K ow of 2.70, and a regression

- derived equation Vapor pressure 1.16X10

- 7 mm Hg at 21 0 C Hartley D, Kidd H,
eds.1983 Henry’s law constant 2.8X10

- 9 atm

- cu m/mole Calculated

Octanol

- water partition coefficient (K
ow ) 2.70 Hansch et al .; 1995



### Warfarin has the potential to move offsite through food consumption by target species, which travel away from the application site. Other than direct consumption of bait and secondary poisoning, other routes of environmental exposure are expected to be min imal. Although,
warfarin is moderate ly adsor bed , movement of residues by means of leaching through the soil profile to an aquatic environment is possible . Further, warfarin is unlikely to volatilize, unlikely to move offsite due to method of application (mainly in bait stations), and due to the relatively low application rates (maximum of 0.003 lb a.i./placement), unlikely to runoff or leach substantially.



## 5.1 Transformation Products

Warfarin is reduced by Nocardia and Arthrobacter spp. to the alcohol

.



# 6 Receptors

6.1 Toxicity Summary

Table 3 provides a summary of the taxonomic groups and the surrogate species tested to characterize the potential acute and chronic ecological effects of warfarin

. In addition, the table provides a preliminary overview of the potential acute toxicity of warfarin by providing the acute toxicity classifications. No ecotoxicity data are available for any degradates of warfarin

.

### Page 11 of 51 

### Warfarin is slightly toxic to birds on an acute oral basis, moderately toxic to birds on a subacute dietary exposure basis, and very highly toxic to mammals on an acute oral and subacute dietary exposure basis. Studies evaluating chronic toxicity of warfarin to birds and mammals have not
been sub mitted to the Agency. In addition, data on the toxicity of warfarin to terrestrial invertebrates and terrestrial plants have not been submitted to the Agency.

Technical grade warfarin is classified as moderately toxic to freshwater fish and invertebrates on an acute exposure basis. Acute estuarine/marine fish and invertebrate data as well as chronic exposure effect s data to warfarin for fish and invertebrates have not been submitted to the Agency. In addition, no toxicity data for aquatic plants were sub mitted to the Agency.

Table 3 . Most Sensitive Test Species Evaluated for Assessing Potential Ecological Effects of
Warfarin

.

Taxonomic Group Study Type Tested Species Toxicity Endpoint Acute Toxicity
Classification/
NOAEC most
sensitive endpoint(s) MRID and
Classification

Birds 1 Acute oral (primary
bait consumer) Anas platyrhynchos ( Mallard) LD 50 = 621 mg/kg

- bw Slightly toxic 00248782 (Acceptable)

Dietary Colinus virginianus (Northern bobwhite) LC 50 = 625 mg/kg

- diet Moderately toxic. 15 day study, most deaths days

3

- 7, one day 10 00153365 (Acceptable)

Chronic No data

Mammals Acute oral (single dose) Laboratory Rat LD 50 = 3.0 mg/kg

- bw Very highly toxic 05002272 (Acceptable)

Dietary (5

- day exposure) Laboratory Rat LC 50 = 4.41 ppm Very highly toxic.
Observed 14 days, mortalities days 3

- 9 Teeters 1981 (TMN 126) 4 (Supplemental)

Chronic No data

Terrestrial
invertebrates Acute

contact No data

Freshwater
fish 2 Acute Rainbow trout (Oncorhynchus mykiss) 96

- hr LC 50 > 16 mg/L 3 00156284 (Acceptable)

Chronic No data

Freshwater
invertebrates Acute Water flea ( Daphnia magna) 48

- hr LC 50 > 17 mg/L Slightly toxic 3 00153368 (Acceptable)

Chronic No data

Estuarine/
marine fish Acute and
Chronic No data

Estuarine/
marine
invertebrates Acute and
Chronic No data

### Page 12 of 51 Table 3 . Most Sensitive Test Species Evaluated for Assessing Potential Ecological Effects of
Warfarin

.

Taxonomic Group Study Type Tested Species Toxicity Endpoint Acute Toxicity
Classification/
NOAEC most
sensitive endpoint(s) MRID and
Classification

Terrestrial plants Seedling

emergence No data

Vegetative vigor No data

Aquatic plants and algae Vascular No data

Non

vascular No data

1 Birds represent surrogates for terrestrial

- phase amphibians and reptiles.

2 Freshwater fish are used as surrogates for aquatic

- phase amphibians.

3 Not acutely toxic below the reported level of solubility in distilled water (17 mg/L)

4 Teeters, W.R. (1981) Warfarin technical: Toxicity to Laboratory Rat: Test No. 126. (U.S. Environmental Protection Agency, Pesticides Regulation Div., Agricultural Research Center, Animal Biology Laboratory, unpublished report.)



## 6.2 Secondary Toxicity

In the available studies, birds and mammals were exposed to warfarin in whole or ground carcasses, which were usually those of rats or mice, or in fortified meat. Most prey animals were fed treated bait, although some were dosed orally. Mortality was inclu ded as a measurement endpoint in all studies. Some studies also reported signs of toxicosis ( e.g., bleeding, prolonged
blood

- coagulation time, abnormal behavior, or regurgitation) in surviving test animals. Although exposure scenarios, test species, and th e number of test animals varied among the studies, collectively these studies provide useful information to characterize secondary hazards from
short

- term exposure. Though these types of secondary exposure studies provide information on the potential effec ts from warfarin exposure that may occur under field conditions, it is often not possible to quantify the level of exposure (rodenticide residues in primary consumers or food consumption by secondary consumers) or the sensitivity of the exposed animals to the
rodenticide.

The few studies available for warfarin indicate that there are few adverse secondary effects for birds at the concentrations that were tested (50 or 500 mg a.i. kg

- bait). In a review of the open literature warfarin studies examining secon dary effects to birds (4 studies) , 2 (5%) out of a total
of 25 individuals died; no adverse signs were reported in the survivors ( Table 4 ). Test species

were tawny owl ( Strix aluco ), black

- billed magpie ( Pica pica ), barn owl ( Tyto alba ), and
Eurasian buzzard ( Buteo buteo ). Laboratory studies for secondary toxicity to mammals suggest
that warfarin is more toxic to mammals than birds . In 7 studies, 9 (9%) of 100 individuals died after eating warfarin

- treated rodents ( Table 5 ). Dead animals included 3 min k, 3 least weasels ( Mustela nivalis ), and 3 dogs while raccoons and European ferrets did not exhibit any mortality or other adverse toxic symptoms typically associated with warfarin

.

### Page 13 of 51 Table 4 . Observed Effects of Warfarin on Birds Consuming Contaminated Carcasses

Predator/scav enger species Prey offered to birds No. prey offered daily per bird No. days birds exposed No. birds exposed No. birds

dead No. survivors with signs of

warfarin toxicity a Referenc e (MRID)

Tawny owl Mice fed bait for 3 days 1 every other day 90

28 4

2 c 0

0 0

0 Townsend et al.
1981

Black

- billed

magpie Rats fed 0.05% bait c
for 4

- 7 days Ad libitum 5 14 0 0 Mach 1997

Barn owl Rats fed 0.005% bait c 4 total 5

- 7 4 2 nr Lee 1994 b

Eurasian
buzzard Rat/mouse Ad libitum 18 1 0 nr Telle 1955 b

a eb = external bleeding; ih = internal hematoma; bl = bleeding (unspecified); ct = increased blood coagulation time; nr = not reported

b Cited in US EPA (2004) Potential Risks of Nine Rodenticides to Birds and Nontarget Mammals: a Comparative Approach

c rat and mouse registered baits in the U.S. are 0.025% a.i. and 0.054% a.i

### Page 14 of 51 Table 5 . Observed Effects of Warfarin on Mammals Consuming Contaminated Carcasses

Predator/scav enger species Prey offered to

mammals No. prey offered daily per

mammal No. days

mammals exposed No.

mammals exposed No.

mammals

dead No. survivors with signs of

warfarin toxicity a Reference (MRID)

Mink Nutria fed 0.025% bait for at least 7 days Ad libitum 8

- 15 3 3 No survivors Evans and Ward
1967 b

Mink Rabbits fed 25 or 67 mg a.i./kg bait c for 5
weeks Ad libitum 28 50 0 0 Aulerich et al
1987

Least weasel Mice fed 0.001% bait, 0.005% bait,
Or 0.02% bait for 3 days c Ad libitum 90
29

- 90

12

- 57 2

2

2 0

1

2 2 (ct) 1 (ct)
No survivors Townsend et al.
1984

European

ferret Prairie dogs fed 0.05%
bait c for 15 days 1 7 10 0 0 Carlet and Mach
1997

MRID#
44995003

European

ferret Prairie dogs fed 0.05%
bait c for 15 days Ad libitum 5 10 0 0 Mach 1998

MRID#
44820001

Racoon Rats fed 0.025% bait for 5 days 1

3 5
5 8

10 d 0

0 0

0 EPA 1982

Dog (domestic) Nutria fed 0.025% bait for at least 7 days Ad libitum 8

- 16 3 1 2 (eb/ct) Evans and Ward
1967 b

Dog (domestic) Mice fed 0.025% bait, 0.05% bait,
Mice dosed with 2.5 mg a.i., 10 mg a.i., 40 mg a.i. 4

- 10

10

1

1

1 56
56
56
25

17 4

1

1

1

1 0

0

0

1

1 0

0

0
No survivors
No survivors Prier and Derse
1962 b

a eb = external bleeding; ih = internal hematoma; bl = bleeding (unspecified); ct = increased blood coagulation time; nr = not reported

b Cited in US EPA (2004) Potential Risks of Nine Rodenticides to Birds and Nontarget Mammals: a Comparative Approach

c rat and mouse registered baits in the U.S. are 0.025% a.i.

d the 10 test animals i ncluded the 8 individuals from the first trial plus 2 additional untested individuals

### Page 15 of 51 

## 6.3 Incident Database Review

A thorough incident collection and analysis for all anticoagulant rodenticides was completed in

2013 . A summary of the 10 warfarin wildlife incidents reported with a certainty classification of

“ possible ”

, “ probabl e” , or “ highly probable ” is included in Table 6

. These classifications mean that, at a minimum, there was supporting evidence ( e.g ., hemorrhaging) and/or residue da ta to indicate that the wildlife involved in the incident were adversely affected by exposure to an anticoagulant rodenticide and/or an independent wildlife specialist, based on findings of a necropsy examination and toxicological analysis, identified an a nticoagulant rodenticide as the cause of death in the incident report. The reported avia n species include a bobwhite quail and carnivore/scavenger birds that include the bald eagle, peregrine falcon, great horned owl, and Cooper’s hawk . The reported mammal ian species include squirrels.

Although most of the reported wildlife incidents involve animals found dead, there are several rodenticide incidents that involve incapacitated animals (most of which died after being found). They demonstrate that animals exposed to rodenticides may be incapacitated in ways that would almost certainly make them more vulnerable to predators and accidental deaths ( e.g., car or window strikes). If an animal dies due to predation or an accident, their death may not necessarily be attributed to a pesticide, even if it is a contributing factor.

Table 6. Wildlife Mortality Incidents for Warfarin Reported in the EIIS Database

Incident

ID Year Legality Certainty State Land Use Generic Species (Number Affected) Comments

CEE

- TV

# 61108 1998 N/R Probable NY N/R Cooper’s Hawk (1) Warfarin detected in liver at 0.73

ppm

I003350

- 001 1995 N/R Probable NY Residential Bald Eagle (1) Warfarin detected in liver at 1.4 ppm. Second year male diagnosed with warfarin
intoxication. Gross pathology

hemorrhage in alimentary canal.

I004169

- 001 1981 Registered Possible VA Agricultura

l Bobwhite Quail (3) Gross pathology found lesions in
the birds consistent with warfarin poisoning; no analytical data were included in the report.

I006306

- 016 1986 N/R Highly
Probable NJ N/R Peregrine Falcon (1) Warfarin detected in the liver at 1.48 ppm

I008146

- 001 1998 Registered

Use Probable NY N/R Great
Horned Owl (1) Warfarin detected in liver at 0.73

ppm

I011130

- 001 2000 N/R Probable GA Agricultura

l Bald Eagle (1) Chemical residues were found in the gut contents, or bait material and biological or biochemical
evidence

### Page 16 of 51 Table 6. Wildlife Mortality Incidents for Warfarin Reported in the EIIS Database

Incident

ID Year Legality Certainty State Land Use Generic Species (Number Affected) Comments

I013810

- 014 1971 N/R Probable NY N/R Squirrel (1)

--

R000

- 02

- 054 1981 N/R Probable NY N/R Squirrel (1) Warfarin detected in the liver at 0.22 ppm. Gross pathology

pallor of muscle and/or internal organs, inter

- and intramuscular hemorrhages, hemorrhage and/or serum in pericardial sac.



# 7 Exposure Pathways of Concern

The environmental fate properties and use patterns of warfarin indicate th at non

- target consumption of bait, consumption of individuals that have consumed bait, represent potential transport mechanisms of warfarin to terrestrial organisms.

Drinking water and inhalation exposure pathways were screened using the SIP (Screening Imbibition Program) and STIR (Screening Tool for Inhalation Risk) screening methods SIP and
STIR are described in detail at: http://www2.epa.gov/pesticide

- science

- and

- assessing

- pesticide

risks/models

- pesticide

- risk

- assessment#terrestrial

. The drinking water pathway was found not to be an exposure pathway of potential concern for acute risks to birds due to low solubility of
warf arin relative to toxicity

. However, the drinking water pathway is an exposure pathway of potential concern for acute risks to mammals. Chronic risks to mammals and birds cannot be excluded because there is insufficient data on chronic toxicity. The inhala tion exposure pathway
was found not to be an exposure pathway of concern for birds due to the low volatility of
warfarin

. SIP and STIR results are presented in Appendix B

.



# 8 Analysis Plan

8.1 S tressors of Concern

8.1.1 Ecological Risk Assessment

For this registrati on review, t he stressor of ecological concern for terrestrial organisms is the parent compound, warfarin

.

### Page 17 of 51 

### 8.1.2 Drinking Water Assessment

A d rinking water assessment isn’t expected to be conducted during the r egistration review because
b ait is contained in stations, and therefore not available for runoff

.



## 8.2 Measures of Exposure

Bait is contained in stations, and therefore not available for runoff, thus exposure of aquatic environment is unlikely. A vailable toxicity data indicates that warfarin is not toxic t o aquatic receptors up to the limit of solubility. In addition, the use pattern is baits only and not large scale
broadcast treatments. For these reasons, EFED does not expect to conduct a quantitative aquatic risk assessment during registration review.

For the warfarin registration review risk assessment , it will be assumed that terrestrial animals could be exposed in two different pathways. Animals may directly consume bait (primary consumption), or animals may consume contaminated carcasses either kil led or scavenged by the consumer (secondary consumption). Both approaches and the expected exposure levels are detailed below. It is important to note that these methods differ from what is typically done in
EFED risk assessments , but they are appropriate for warfarin based on the use parameters and environmental exposures described previously and consistent with other EFED risk assessments
for rodenticides

.

8.2.1 Estimating Primary Terrestrial Exposure

EFED’s exposure assessment for the rodenticides differs from that for most other pesticides. For a rodenticide, the bait itself is the potential food item of concern. Thus, the amount of active ingredient in the formulated bait is used as an estimated env ironmental concentration ( EEC )

. This information is used to estimate the amount of grain bait that birds and mammals of various sizes need to consume to obtain a dose expected to be lethal to 50% of the individuals in the population (i.e., LD 50 

### dose). Est imates of food

- ingestion rates (g dry matter per day) are determined from established allometric equations presented in the Wildlife Exposure Factors
Handbook (USEPA 1993). The concentration of warfarin in grain bait is also used to estimate
initial dietar y exposure (mg a.i. per kg in bait) which in turn is used to calculate avian and mammalian dietary RQs.

8.2.1.1 Expected Warfarin Accumulation through a Single Feeding on Bait

Exposure through bait consumption will be calculated using two methodologies. For the first method, warfarin exposure is calculated as mg a.i./kg

- bwt, where kg

- bwt is the kilograms of the consuming individual for three standard weight classes of passeriforms and rodents. Exposure (food dry weight consumption) estimates were derived usin g allometric equations from USEPA (1993). The allometric equations for passeriform birds and rodent mammals were used as these would best approximate those individuals with high potential for consuming grain and they

### Page 18 of 51 

### would give the most conservative exposu re estimates. Food dry weight was converted to wet weight assuming the bait contained 10% water, similar to the assumption that seeds for wildlife consumption contain 10% water (USEPA 1993). Formulas for calculation of dose estimates are provided in Table 7 , and warfarin exposure estimates (on a dose basis) are provided in Table 8

. RQs are generated by dividing these exposure estimates of warfarin (mg a.i./kg

- bwt) for a given weight class by the most conservative toxicity endpoint for the relevant taxa scal ing adjusted for the default body weights. RQs using these exposure estimates were generated for acute bird and mammal (using LD 50 

### data) non

- targets.

Table 

### 7

. Formulas for Calculation of Daily Warfarin Intake based on Consumption of Bait.



### Passeriform bird food intake (g, dry weight ): FI (g dry

- wt/day) = 0.398 * Wt(g) 0.850



### Rodent mammal food intake (g, dry weight ): FI (g dry

- wt/day) = 0.621 * Wt(g) 0.564



### Food intake (g, wet weight ): FI (g wet

- wt/day) = FI (g dry

- wt/day) / 0.90

Warfarin intake (mg a.i./kg

- bwt/day) = FI (g wet

- wt/day) * mg a.i./kg

- bait / Wt(g)

Where: Wt(g) = weight (in grams) of the bird or mammal consumer

mg a.i./kg

- bait = 50 or 100 depending on warfarin concentration in bait

Table 

### 8

. Expected Daily Warfari n Intake for Default Bird and Mammal Weights based on Consumption of Bait. Weight

(g) Food intake (g dry

wt/day) Food intake (g wet

wt/day) Warfarin intake (mg a.i./kg

- bwt/day)

Bait concentration = 250 mg a.i./kg

- bait

Passeriform
Birds* 20 5.1 5.6 63.5

100 19.9 22.2 49.9

1000 141.2 156.9 35.3

Rodent
Mammals 15 2.9 3.2 47.7

35 4.6 5.1 32.9

1000 30.6 34.0 7.6 *surrogate for reptiles and terrestrial

- phase amphibians



### 8.2.1.2 Expected Warfarin Accumulation through Multiple Feedings on
Bait

Available data on the retention times for warfarin are provided in Table 9

. In contrast to the other anticoagulants, warfarin is extensively metabolized

, and the major route of excretion is in

### Page 19 of 51 

### the urine. Meehan (1984) states that approximately half the warfarin consumed by a rat remains in the body after 6 hours, suggesting that up to 50% may be eliminated in this time period. EPA (1982) noted that only 7.6% of the warfarin consumed in bait by 11 rats remained in the carcass
after a 5

- day feeding perio d. Ford (1993; cited in Poché and Mach 2001) reported a half

- life of 42 hours in the gastro

- intestinal tract, which supports the conclusion that a portion of the consumed warfarin dose is rapidly eliminated from the body. However, there is evidence that

wa rfarin residues that are not excreted though urine and fecal matter may accumulate in various body tissues, especially the liver. Though warfarin concentrates in the liver, measurable amounts have also been found in the adrenal glands, lungs, bone marrow, kidneys, and lymph nodes (Machlin 1984).

Vandenbroucke et al. (2008) orally dosed groups of mice with 5,985 μg a.i./mouse wafarin, which is approximately one

- half of the LD 50 

### dose. Warfarin was then assayed in liver tissue and blood plasma from euthanize d mice at various times up to 21 days after dose administrations. The study authors estimated the elimination half

- life of warfarin in liver tissue to be 66.8 days
and the half

- life in blood plasma to be 14.9 days.

Fisher et al. (2003) orally dosed 20 ra ts by gastric intubation with a single dose of 1.0 mg a.i./kg warfarin. Rats were monitored for 5 days after dosing for symptoms of anticoagulant poisoning. Groups of six or seven rats were euthanized at week 1, 18, and 24. The livers were removed
post

- mor tem for analysis of warfarin residue by HPLC. Warfarin elimination half

- life in rat liver tissue was estimated to be 26.2 days.

The discrepancies between the half

- lives estimated in Vandenbroucke et al. (2008) and Fisher et al. (2003) may be partially a result of the different test organisms as there is some indication that elimination times for warfarin may vary among species. For example, O’Brien et al. (1987; cited in Eason et al. 2001) found comparatively rapid clearance of warfarin in pigs, with

conc entrations declining to very low levels after approximately 30 days. In addition, Wantabe et al. 2010 examined the differences in metabolism of warfarin in birds in order to study differences in species sensitivities to this rodenticide. Liver samples from domestic chickens ( Gallus gallus ), osteriches ( Struthio camelus ), mallard ducks ( Anas platyrhunchos ), snowy owls ( Bubo
scandiacus ) and a great horned owl ( B. virginianus ) were used to measure the metabolism of warfarin to its hydroxylated degradates. Resu lts of the study indicated that owls had the lowest metabolism of warfarin. Therefore, relative to the other species tested, owls may have a limited ability to detoxify warfarin. This could potentially lead to increased warfarin sensitivity in owls,
relati ve to EPA's typical test species (e.g., mallard ducks).

Half

- life values for blood plasma also vary greatly among species. Breckenridge et al. (1985) intravenously dosed male New Zealand white rabbits with 20 μmol/kg warfarin. Blood samples
were taken at regular intervals and analyzed for wafarin concentration. The study authors reported a plasma elimination half

- life for warfarin of 5.6 hours in rabbits.

### Page 20 of 51 Table 

### 9

. Retention of Warfarin in Blood and Liver

Rodenticide Species Dose (mg a.i./kg) # doses Blood t 1/2 a (days) Liver
retention a,b (days) Reference (MRID)

Warfarin Mouse 5985 μg/mouse 1 14.9 66.8 (t 1/2 ) Vandenbroucke et al.
2008

Warfarin Rat unknown unknown 0.7 (male)

1.2 (female) NA Pyrola 1968 f

Warfarin Rat 1.0 1 NA 26.2 (t 1/2 ) Fisher et al. 2003 (48190801)

Warfarin Rabbit unknown unknown 0.2 NA Breckenridge et al
1985 f

Warfarin Possum unknown unknown 0.5 NA Eason et al. 1999 d

Warfarin Pig unknown unknown NA 30

- 40 O’Brien et al 1987 f

a t 1/2 for plasma and liver is the elimination half

- life

b liver retention is expressed as either the time period for which residues persist or as the elimination half

- life

c the elimination half

- life of 350 days is for a single oral dose of 0.02 or 0.15 mg a.i. /kg; elimination was not biphasic

d the elimination half

- life of 128 days is the terminal phase for a single oral dose of 0.35 mg a.i./kg; elimination was biphasic

e Cited in US EPA (2004) Potential Risks of Nine Rodenticides to Birds and Nontarget Mammals : a Comparative Approach

f cited in Eason et al. 2001



### As indicated previously, warfarin typically causes mortality several days after ingestion, which may allow target animals consume bait for several days before dying. This can lead to doses that far exceed the lethal dose. A compound that accumulates in body tissues may pose greater risk t o primary and secondary consumers, especially if repeated sublethal exposure results in the accumulation of a lethal dose or if additional exposures occur before the lethal dose has taken its effect ( i.e., leading to a dose that is beyond what is sufficien t to cause mortality).

Cumulative rodenticide doses for animals consuming bait for six consecutive days were also calculated using formulae in Table 10 . This analysis assumed that 100% of the daily diet of the animals is represented by the rodenticide ba it and that they eliminate the warfarin with a half

- life
of 66.8 days based on the highest definitive liver half

- life value ( Table 9 )

. In the formula, the variable “C” represents the concentration of the pesticide in the bait. The elimination rate constant (k) was calculated using the estimated warfarin half

- life (t 1/2 

### = 66.8 days), and food intake (FI) was calculated according to the all ometric equation for each taxonomic group ( Table

7 ). The resulting cumulative body burden concentrations of warfarin are presented in Table 1 1

. Different half

- life assumptions based on available data may be used to further characterize risk in
the assessme nt.

### Page 21 of 51 Table 

### 1 0 . Formulas for Calculation of Warfarin Body Burden based on Consumption of Bait for Six Consecutive Days.



## C FI e D D k

t t 

## * * ) 1 ( 

## + = −

− 

# ( )

2 / 1 

## 2 ln t k =

Table 

### 1 1 . Calculated warfarin body burden in avian and mammalian consumers
of bait after six days of exposure Body weight (g) Bait concentration = 250 mg a.i./kg

- bait

Passerine Generic Bird

20 371.2 330.0

100 291.6 189.9

1000 206.4 85.0

Rodent Generic Mammal

15 

### 278.7 212.1

35 192.8 182.4

1000 

### 44.7 100.5



### 8.2.1.3 Expected Warfarin Exposure based on Bait Concentration

The second exposure method for primary consumption of bait results in a diet concentration of
250 mg a.i./kg

- bait (concentrations of warfarin as packaged in bait). RQs are calculated using this estimate of dietary con centration and the LC 50 

### (mg a.i./kg

- diet) available from dietary toxicity studies. RQs using these exposure estimates were generated for acute bird and mammal (using LC 50 

### data) non

- targets.

8.2.2 Estimating Secondary Terrestrial Exposure

Secondary exposure analysis (from consumption of contaminated individuals ) requires consideration of residues in tissues of target and non

- target organisms that are commonly consumed by predators and scavengers. Moreover, it is important to know how long the residue persists in body tissues. Residue concentrations for non

- target animals fed warfarin are available in open literature. Design and methodology vary among studies, adding unknown variability to the results and analysis. Pending development of additional methods and testing requirements for such studies, these tests provide the best data available.

The determination of warfarin intake by individuals consuming warfarin poisoned animals or carcasses is calculated in a manner similar to the appro ach for individuals consuming bait ( Section 8.2.2.1 ). Empirical residue data are used instead of bait concentration of warfarin ( Table 1 1 ). Warfarin body burdens in carcasses collected from field and laboratory studies were determined in mammals, after exposure to warfarin bait. Data are available for a variety of
small

- and medium

- sized mammalian granivores and omnivores. No data were identified for other exposed taxonomic groups ( e.g., birds and reptiles). For all studies, it was assumed the

concent rations were reported using wet weights of the mammals.

### Page 22 of 51 

### In laboratory studies, mean warfarin residues in mammalian carcass ranged from 0.038 to 104 mg a.i./kg

- bw. The relatively high mean residue values are most likely a result of the study design where Aulerich et al . (1987) fed rabbits low doses of warfarin bait for an extended period of time. This study indicates that mammals consuming small amounts of warfarin bait over an extended period are able to survive poisoning, perhaps because they are capab le of building a tolerance to warfarin in this situation, or because they become more effective at metabolizing the compound. This study also suggests that these mammals have the potential to accumulate large amounts of warfarin residue ( 82

- 104 mg a.i./kg

- bw, Table 1 2 ) which may make them significantly more toxic to secondary consumers than a mammal that consumed a single lethal dose. Because of the lack of data on warfarin residues in birds, terrestrial

- phase amphibians and reptiles, it is assumed the ma mmalian body burden data would be relevant for all the evaluated taxonomic groups. Since the registered bait blocks contain 0.025% (250 mg a.i/kg

- bait), the low dose values found in the majority of the residue studies, aside from the Aulerich data, likely do
not reflect true field conditions either. For th e registration review assessment, the body residue level of 2.95 mg a.i./kg

- carcass (Townsend et al . 1984) will be used because the bait concentration used in the Towsend et al. study (200 mg a.i./kg bait ) is the closest approximation of the concentration found in the registered warfarin baits. Different assumptions of body residue levels in primary consumers based on the available data may be used to further characterize risk
in the assessment.

Table 1 

### 2 . Warfarin Residue Levels in Mammalian Primary Consumers.

mg ai/kg
bait Target species Site Sample size Days exposed Mean whole

carcass residue (mg a.i./kg

- bw) Reference

200 a Mouse Laboratory 17 3 2.95 ± 0.26 (SE) Townsend et a l.
1984

67 a Rabbit Laboratory Not reported 35 104 Aulerich et al . 1987

50 a Mouse Laboratory 62 3 1.63 ± 0.1 (SE) Townsend et a l.
1981

50 a Mouse Laboratory 18 3 1.58 ± 0.1 (SE) Townsend et a l.
1984

25 a Rabbit Laboratory Not reported 35 82 Aulerich et a l. 1987

10 a Mouse Laboratory 15 3 0.42 ±0.04 (SE) Townsend et al

. 1984



### Warfarin exposure through carcass consumption is calculated as mg a.i./kg

- bwt, where kg

- bwt is the kilograms of the consuming individual for three weight classes of birds and mammals. For this analysis, bird weight classes of 50, 1000, and 2000 g individuals and mammal weight classes of 50, 1000, and 3000 g individuals are used to better represe nt the larger size of carnivores and scavengers relative to the full range of bird and mammal weights. The measured maximum body burden in the prey is then used to estimate rodenticide exposure in the secondary consumer using the general food intake allome tric equations described in Section 8.2.1 above. Secondary

consumers are assumed to be mammals weighing 50g, 1000g, or 3000g, or birds weighing 100g, 1000g, or 5000g. For example, American kestrels range from 100

- 150g, red

- tailed hawks range
from 900

- 1000 g and bald eagles range from 4000

- 5000g (Dunning 1984). Exposure (food dry

### Page 23 of 51 

### weight consumption) estimates are derived using the generic bird and mammal allometric equations from (EPA 1993). Food dry weight was converted to wet weight assuming the consumed p rey/carcass contained 68% water (USEPA 1993). Formulas for calculation of dose estimates are provided in Table 1 3 , and warfarin exposure estimates (on a dose basis) are provided in Table 1 4 . RQs using these exposure estimates w ill be generated for bird s an d
mammal s (using LD 50 

### data).

Table 1 

### 3

. Formulas for Calculation of Daily Warfarin Intake for Birds and Mammals based on Consumption of Carcasses.



### Bird food intake (g, dry weight ): FI (g dry

- wt/day) = 0.648 * Wt(g) 0.651



### Mammal food intake (g, dry weight ): FI (g dry

- wt/day) = 0.235 * Wt(g) 0.822



### Food intake (g, wet weight ): FI (g wet

- wt/day) = FI (g dry

- wt/day) / 0.32

Warfarin intake (mg a.i./kg

- bwt/day) = FI (g wet

- wt/day) * 2.95 mg a.i./kg

- carcass / Wt(g)

Where: Wt(g) = weight (in gram s) of the bird or mammal consumer

Table 1 

### 4

. Expected Daily Warfarin Intakes for Carnivorous Bird s and Mammals based on Consumption of Contaminated Carcasses Weight (g) Food intake (g dry

- wt/day) Food intake (g wet

- wt/day) Warfarin intake (mg a.i./kg

- bwt/day) 1

Birds* 50 8.3 25.8 1.55

1000 58.2 181.7 0.55

2000 91.3 285.4 0.43

Mammals 50 5.9 18.3 1.10

1000 68.7 214.7 0.64

3000 169.5 529.8 0.53 *surrogate for reptiles and terrestrial

- phase amphibians

1 See Table 14 for derivation.



### The second exposure method for consumption of contaminated carcasses results in a carcass
concentration of 2.95 mg a.i./kg

- carcass (maximum measured concentration of warfarin in carcasses). RQs using these exposure estimates will be generated for bird s and mammal s (using

LC 50 

### data) exposures.

8.2.3 Estimating Additional Environmental Exposures

Screening level calculations suggest that the drinking water pathway and inhalation pathways will not pose significant risks to birds and mammals ( Appendix B ). If additional information indicates there may be concerns, these pathways will be re

- evaluated at the time of the risk

assessment.

### Page 24 of 51 

### No monitoring data in surface water, in groundwater or in air were found from the USGS NAWQA program ( http://water.usgs.go v/nawqa ), the California Department of Pesticide Regulation CDPR ( http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm ) or from the USEPA STORET program. Water monitoring programs such as these generally monitor for agricultural pesticides and typically d o not include analysis for rodenticide s such as warfarin

. If water monitoring data are identified at the time the risk assessment is conducted , these data will be used for additional exposure characterization



## 8.3 Measures of Effect

Toxicity data presented in Section 6 of this problem formulation will be used to calculate risk quotients. Any additional information submitted by the registrant or found in the open literature prior to conduct of the risk assessment wi ll also be considered. The open literature studies are identified using EPA’s ECOTOXicology database ( ECOTOX) (USEPA, 2007), which employs a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, and
wildlife. The evaluation of both sources of data can also provide insight into the direct and indirect effects of pesticides on biotic communities from loss of species that are sensitive to the chemicals and from changes in structure and functional characteristics o f the affected
communities.



# 9 Endangered Species Assessment

Consistent with EPA’s responsibility under the Endangered Species Act (ESA), the Agency will evaluate risks to federally listed threatened and endangered (listed) species from registered uses of p esticides in accordance with the Joint Interim Approaches developed to implement the recommendations of the April 2013 National Academy of Sciences (NAS) report, Assessing Risks to Endangered and Threatened Species from Pesticides

. The NAS report outlines recommendations on specific scientific and technical issues related to the development of pesticide risk assessments that EPA and the Services must conduct in connection with their obligations under the ESA and FIFRA. EPA will address concerns s pecific to warfarin in connection with the development of its final registration review decision for warfarin

.

In November 2013, EPA, the U.S. Fish and Wildlife Service, National Marine Fisheries (the Services), and USDA released a white paper containing a summary of their joint Interim Approaches for assessing risks to listed species from pesticides. These Interim Approaches were developed jointly by the agencies in response to the NAS recommendations, and reflect a common approach to risk ass essment shared by the agencies as a way of addressing scientific
differences between the EPA and the Services. Details of the joint Interim Approaches are contained in the November 1, 2013 white paper

, Interim Approaches for National

- Level Pesticide Endangered Species Act Assessments Based on the Recommendations of the National Academy of Sciences April 2013 Report.

### Page 25 of 51 

### Given that the agencies are continuing to develop and work toward implementation of t he Interim Approaches to assess the potential risks of pesticides to listed species and their designated critical habitat, this ecological problem formulation supporting the Preliminary Work Plan for warfarin does not describe the specific ESA analysis, in cluding effects determinations for specific listed species or designated critical habitat, to be conducted during registration
review. While the agencies continue to develop a common method for ESA analysis, the planned risk assessment for the registratio n review of warfarin will describe the level of ESA analysis completed for this particular registration review case. This assessment will allow EPA to focus its future evaluations on the types of species where the potential for effects exists, once the
sci entific methods being developed by the agencies have been fully vetted. Once the agencies have fully developed and implemented the scientific methods necessary to complete risk assessments for listed species and their designated critical habitats, these me thods will be applied to subsequent analyses of warfarin as part of completing this registration review.



# 10 Endocrine Disruptor Screening Program

Warfarin was not included in the first group or the second group of chemicals issued an order to
conduct Tier 1 EDSP testing. For additional information the EDSP program, visit http://www2.epa.gov/endocrine

- disruption/endocrine

- disruptor

- screening

- program

- edsp

overview

.



# 11 Preliminary Identification of Data Gaps

11.1 Environmental Fate

Since the data used in this assessment were derived from open literature and were not based on

USEPA

- guideline studies, warfarin’s persistence and mobility have not been fully
characterized. Should the use rate incr ease significantly or if a new use is proposed in the future, guideline studies may be necessary for a better understanding of warfarin’s persistence and mobility.

### Page 26 of 51 

### Available Environmental Fate Data for Warfarin.

OCSPP
Guideline Data Requirement Submitted Studies (MRID) Study
Classification Are data needed
for risk
assessment? Current Additional Data

Need

835.2120 Hydrolysis (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data

are not necessary for risk
assessment at this time.

835.2240 Aqueous photolysis (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data are not necessary for risk
assessment at this time.

835.2410 Soil photolysis (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data are not necessary for risk
assessment at this time.

835.4100 Aerobic soil
metabolism (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data are not necessary for risk
assessment at this time.

835.4200 Anaerobic soil
metabolism (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data are not necessary for risk
assessment at this time.

835.4300 Aerobic aquatic
metabolism (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data are not necessary for risk
assessment at this time.

835.4400 Anaerobic aquatic
metabolism (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data are not necessary for risk
assessment at this time.

### Page 27 of 51 

### Available Environmental Fate Data for Warfarin.

OCSPP
Guideline Data Requirement Submitted Studies (MRID) Study
Classification Are data needed
for risk
assessment? Current Additional Data

Need

835.1230
835.1240 Adsorption/ desorption and leaching (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data are not necessary for risk
assessment at this time.

835.6100 Terrestrial field dissipation (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data are not necessary for risk
assessment at this time. Storage Stability Study (TFD) (None) (N/A) No

850.1730 Fish
bioconcentration (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap was
not identified as these data are not necessary for risk
assessment at this time.

Environmental Chemistry
Method: Water

850.6100 Analytical
method in water and independent laboratory
validation (None) (N/A) Yes Enforcement analytical methods are being routinely requested in registration review for use by state lead agencies.

Environmental Chemistry
Method: Soil Analytical
method in soil and independent laboratory
validation (None) (N/A) Yes Enforcement analytical methods are being routinely requested in registration review for use by state lead agencies.



## 11.2 Ecological Effects

Tables 15 and 16 identify ecological effects studies by MRID that offer data for each guideline requirement, as well as study classifications and whether or not further data are needed in order to support risk assessment.

Currently, i nadequate data are available to further characterize the differential toxicity among bird species. In addition, there is evidence of different or multiple modes

- of

- action of
rodenticides in different taxa. Additional toxicity data on a wider range of speci es or data exploring mode

- of

- action would be beneficial to better understand the natural variation and to improve confidence in the assessment of risk to non

- target species.

No data are available to assess the effects of long

- term, low

- dose exposure of w arfarin on avian reproduction (OCSPP 850.2300) or survival. Avian reproduction data are available for another registered anticoagulant rodenticide, chlorophacinone that highlights the potential for effects from long

- term, low

- dose exposure

. For chlorophacinone, m allard ducks exposed to dietary
concentrations for five days had an LC 50 

### = 172 mg/kg

- diet (MRID 41513103); however, nine of

### Page 28 of 51 

### 16 (56%) adult females died exhibiting symptoms of anticoagulant poisoning during the avian reproduction study eat ing a diet containing only 0.96 mg a.i./kg

- diet (MRID 489904002). EFED recommends that additional data on effects of long

- term low

- dose exposure of warfarin to birds through extended exposure dietary studies and avian reproduction studies be requested.

N o data are available to assess of the toxicity of warfarin to terrestrial invertebrates. EFED does
not have concerns for warfarin exposure to pollinators such as bees and butterflies, as expected exposures would be low. Warfarin is not applied as a spray; therefore, expected exposure on plants, including flowers, would be low. Pollinators would not be expected to feed on live animals or carcasses that may have been contaminated with warfarin

. Warfarin exposure to terrestrial invertebrates may occur if indi viduals feed on the bait, feed on live animals
contaminated with warfarin residues, or feed on carcasses with warfarin residues. No terrestrial invertebrate incidents have been reported for warfarin

.

The earthworm LC 50 

### values for bromadiolone, a second g eneration rodenticide, at 24 h and 48 h were 145.70 μg/cm 2 

### and 25.03 μg/cm 2 

### , respectively, and at 14 d and 28 d were 449.958 mg/kg

soil and 105.593 mg/kg

- soil , respectively (Liu et al. 2015). Incidences of terrestrial invertebrates consuming bait containing an anti

- coagulant rodenticide and subsequently excreting it have been documented (Fisher et al. 2007; Hernandez

- Moreno et al. 2013). Toxicity of warfarin to terrestrial invertebrates is unk nown; however, there is evidence to suggest that toxicity may
occur and that the exposure pathway for secondary exposure is complete. EFED is not requesting the full suite of pollinator protection studies as outlined in recent guidance , at this time ( http://www2.epa.gov/pollinator

- protection/pollinator

- risk

- assessment

- guidance ). However, EFED does request an earthworm toxicity study for warfarin and any existing da ta that demonstrate toxicity, or lack of toxicity, to warfarin for terrestrial invertebrates.

Although they are technically considered data gaps, EFED does not recommend requesting terrestrial plant, aquatic plant, chronic fish, or chronic aquatic inver tebrate toxicity data for
warfarin at this time since these data would not be expected to change the conclusions of th e registration review risk assessment. There remains uncertainty in the level of risk for each of these taxonomic groups given the missing data; however, the expected exposures for the currently registered use pattern s will be relatively low:

• Terrestrial plants

- No data are available to assess of the toxicity of warfarin to terrestrial plants; however, exposure to plants is also expected t o be low since there is no spray application and the material is applied as a formulated bait or a treated grain.
Warfarin binds strongly to organic material (i.e., the formulated bait or grain) and little is expected to be available for runoff or leaching . No plant incidents have been reported
for warfarin

.

• Aquatic plants

– No data are available to assess the toxicity of warfarin to aquatic plants; however, aquatic exposure is also expected to be low since there is no spray application
and the material is applied as a formulated bait or a treated grain. Warfarin binds strongly to organic material (i.e., the formulated bait or grain) and little is expected to be available for runoff or leaching. No aquatic incidents have been reported for warfarin

.

### Page 29 of 51 

### • Chronic fish and aquatic invertebrates

– No data are available to assess the chronic toxicity of warfarin to fish and aquatic invertebrates; however, aquatic exposure is expected to be low since there is no spray application and the material is applied as a
formu lated bait or a treated grain. Warfarin is moderately acutely toxic to fish and invertebrates, and chronic effects would not be unexpected. However, warfarin binds strongly to organic material (i.e., the formulated bait or grain) and little is expected to be available for runoff or leaching for this proposed use. No aquatic incidents have been reported for warfarin

.

Table 1 

### 5 . Available ecological effects data for terrestrial organisms exposed to warfarin and remaining data gaps.

OCSPP
Guideline Data Requirement Submitted Studies (MRID) Study
Classification Are data
needed for
risk
assessment? Current Additional

Data Need

850.2100 Avian oral toxicity 00156284 acceptable Yes Data are requested for
avian acute oral with passerine species 00153369 acceptable

00248782 acceptable

05005716 supplemental

850.2200 Avian dietary toxicity 00153365 acceptable No

--

00117979 supplemental

00161724 acceptable

00156283 supplemental

00153366 acceptable

00157812 acceptable

00156285 acceptable

850.2300 Avian reproduction (None) (N/A) Yes Data are requested for avian reproduction toxicity testing an upland game bird species and a waterfowl species

.
Non

guideline Avian inhalation (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap
was not identified as
these data are not necessary for risk
assessment at this time.

### Page 30 of 51 Table 1 

### 5 . Available ecological effects data for terrestrial organisms exposed to warfarin and remaining data gaps.

OCSPP
Guideline Data Requirement Submitted Studies (MRID) Study
Classification Are data
needed for
risk
assessment? Current Additional

Data Need

850.3020 Honey bee acute contact toxicity (None) (N/A) No Additional data on toxicity to terrestrial
invertebrates other than honey bee may be useful
for risk assessment but are not required at this
time.

850.3030 Honey bee residue on foliage (None) (N/A) No Data have not been
submitted to fulfill these guidelines. Data gaps
were not identified as
these data are not necessary for risk
assessment at this time. OECD TG

213 Acute oral toxicity to adult honey bees (None) (N/A) No

OECD TG

237 Acute oral toxicity to larval honey bees (None) (N/A) No

Non

guideline Chronic oral toxicity to adult honey bees (None) (N/A) No

Non

guideline Chronic oral toxicity to larval honey bees (None) (N/A) No

Non

guideline Field trial of residues in pollen and nectar (None) (N/A) No

OECD
Guidance 75 Semi

- field testing for pollinator (None) (N/A) No

850.3040 Field testing for pollinator (None) (N/A) No

850.3100 Earthworm Subchronic Toxicity

Test (None) (N/A) Yes Data are requested for earthworm toxicity.

850.4100 Seedling Emergence and Seedling Growth (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap
was not identified as
these data are not necessary for risk
assessment at this time.

850.4150 Vegetative Vigor (None) (N/A) No Data have not been
submitted to fulfill this guideline. A data gap
was not identified as
these data are not necessary for risk
assessment at this time.

### Page 31 of 51 Table 1 

### 6 . Available ecological effects data for aquatic organisms exposed to warfarin and remaining data gaps.

OCSPP
Guideline Data Requirement Submitted
Studies (MRID) Study
Classifications Are data

needed to

conduct

risk
assessment? Current Additional Data

Need

850.1010 Freshwater
invertebrate acute toxicity 00153368 Acceptable No

--

850.1025
850.1035
850.1045
850.1055 Saltwater
invertebrate acute toxicity (None) (N/A) No Data have not been submitted to fulfill this guideline. A data gap was not identified as these data are not necessary for risk
assessment at this time.

850.1075 Freshwater fish acute toxicity 00156284 Acceptable No

--

00156287 Acceptable

850.1075 Saltwater fish acute toxicity (None) (N/A) No Data have not been submitted to fulfill this guideline. A data gap was not identified as these data are not necessary for risk
assessment at this time.

850.1300 Freshwater
invertebrate life cycle (None) (N/A) No Data have not been submitted to fulfill this guideline. A data gap was not identified as these data are not necessary for risk
assessment at this time.

850.1350 Saltwater
invertebrates life cycle (None) (N/A) No Data have not been submitted to fulfill this guideline. A data gap was not identified as these data are not necessary for risk
assessment at this time.

850.1400 Freshwater fish early

- life stage (None) (N/A) No Data have not been submitted to fulfill this guideline. A data gap was not identified as these data are not necessary for risk
assessment at this time.

850.1400 Saltwater fish early

- life stage (None) (N/A) No Data have not been submitted

to fulfill this guideline. A data gap was not identified as these data are not necessary for risk
assessment at this time.

850.1500 Fish life cycle (None) (N/A) No Data have not been submitted to fulfill this guideline. A data gap was not identified as these data are not necessary for risk
assessment at this time.

850.4400 Aquatic plant Toxicity Test using Lemna (None) (N/A) No Data have not been submitted to fulfill this guideline. A data gap was not identified as these

### Page 32 of 51 

# 12 References

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850.4500 Algal toxicity (None) (N/A) No Data have not been submitted to fulfill this guideline. A data gap was not identified as these data are not necessary for risk
assessment at this time.

850.4550 Cyanobacteria (None) (N/A) No Data have not been submitted to fulfill this guideline. A data gap was not identified as these data are not necessary for risk
assessment at this time.

### Page 33 of 51 

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## Warfarin Fate/Chemistry Bibliography

161

- 1 Hydrolysis

MRID Citation Reference

44995009 DER not
located Mach, J. (1999) Project Summary Entitled Measurement of Hydrolysis Rate
Constants for Evaluation of Hazardous Waste Land Disposal: Volume 1. Data on 32 Chemicals. Unpublished study prepared by Genesis Laboratories, Inc. 13 p.



## 161

- 3 Photodegradation

- soil

MRID Citation Reference

44995011 DER not
located Mach, J. (1996) Photodegradation Studies on Soil Using Field Rodent Bait (0.025%) in Colorado. Unpublished study prepared by Genesis Laboratories,

### Page 36 of 51 Inc. 17 p.



# Non Guideline Selections

5001951 2076482 biodegradation Pohl, L.R., G.W. Elmer, E. Haddock, J.M. Neil, W.F. Trager (1973) Reduction of Warfarin by Saccharomyces cerevisae sic cerevisiae Lloydia 36(4): 434.

5002206 2076483 Preis, S. (1957) The Resolution of Warfarin 3 (A

- Acetonylbenzyl) 4

- Hydroxycounarir): Doc toral Thesis. Madison, Wis., University of Wisconsin. (Available from: University Microfilms International, Ann Arbor, MI).

5002527 2076484 methodology Leahy, J.S. Waterhouse, C.E. (1960) The Quantitative Determination of Low Concentrations of Warfarin in Agueous Solution. Analyst 85: 492

- 494.

5002786 2076485 Buckelew, Jr., A.B., A. Chakravarti, W.R. Burge, Thomas, Jr., V.M., M. Ikawa (1972) Effect of M ycotoyins and Coumarins on the Growth of Facillus Megaterium from Spores. Journal of Agricultural and Food Chemistry 20(2):
431

- 433.

5002981 2076486 Bosmann (1971) Macromolecular Synthesis: Effects of Vitamin K and Warfarin on Macromolecular Synthesis in Escherichia ocli. Life Sciences, Part II 10(2): 61

- 69.

5004340 2076487 Leach, H., C.P. Jones (1971) Special Techniques in Clinical Analytical Toxicology: II Fluorescence Spectroscopy. Annals of Clinical Biochemistry 8(3): 83

- 92.

5005014 2076488
Residue analysis Schlegelmilch, R., G. Hornawsky (1968) Tcyikogisch

- chemische
Nachweismethode fuer Warfarin in Material tierischer Berkunft und Futtermitteln. Toxicological Chemical Method of Detecting Warfarin in Material of Animal Origin and in Feeding Stuffs. A rchiv fuer Experimentelle Veterinaermedizin 22(1): 215

- 217.

5005018 2076489
Detection in air Giuran, V. (1972) Consideratii asupra determminarii spectrofotometrice
directe in ultraviolet a varfarinei din aer . Direct spectrophotometric Determination in Ultraviolet Light of Warfarin in the Air. Igiena. Hygiene. XXI(8): 481

- 488.

5005670 2075490 analytical
method Richardson, J.H., M.E. Ando (1977) Sub part per trillion detection of polycyclic aromatic hydrocar bons by laser induced molecular fluorescence. Analytical Chemistry 49(7) 955

- 959.

5005706 2076491
Detection in air Benchey, ? (1975) Chromatogranic separation a dn spectrophotometric determination of the rodenticide ratron in air. Higiena Zdraveopazvane. Hygiene and Sanitation XVIII(1): 90

- 94.

20866 Ralston Purina Company (19??) Determination of Warfarin by Ultra

- violet Spectroscopy. Undated method TSD

- 2. (Unpublished study received Dec 5,
1974 under 602

- 252; CDL:028547

- B)

20867 Ralston Purina Company (19??) Determination of Warfarin by High Pressure Liquid Chromatography. Undated method TSD

- 1. (Unpub

- lished study received Dec 5, 1974 under 602

- 252; CDL:028547

- C)

5002456 Billings, T.J.; Hanks, A.R.; Colvin, B.M. (1976) High

- performance liqui d chromatographic determination of warfarin. Journal of the Association of Official Analytical Chemists 59(5):1104

- 1108.

### Page 37 of 51 5002550 Mundy, D.E.; Quick, M.P.; Machin, A.F. (1976) Determination of warfarin in animal relicta and feedingstuffs by high

- pressure liquid chromatography with confirmation of identity by mass spectrometry. Journal of Chromatography 121(2):335

- 342.

5002715 Lau

- Cam, C.A. (1978) Thin

- layer chromatography of coumarins of medicinal and phytochemical interest on buffered layers. Journal of Chromatography 151(3):391

- 395.

5019781 Mitchell, L.C. (1958) Separation and identification of chlorinated organic pesticides by paper chromatography_ XI_ A study of 114 pesticide chemicals: technical grades produced in 1957 and reference standards. J ournal of the Association of Official Agricultural Chemists 41(4):781

- 816.

44995010 Mach, J. (1999) Environmental Fate Data for Warfarin Summarized by a Reference Entitled Handbook of Environmental Fate and Exposure Data for Organic Chemicals. Unpublish ed study prepared by Genesis Laboratories, Inc. 15 p.



## Warfarin EcoEffec ts Bibliography

71

- 1 Avian Single Dose Oral Toxicity

MRID Citation Reference

156284 2056028 Beavers, J. (1985) An Acute Oral Toxicity Study in the Bobwhite with Warfarin: Final Report: Project No. 205

- 103. Unpublished study prepared by Wildlife International Ltd. 16 p.

ACC 248782 2056009 Shapiro, R. (1982) Avian Single Dose Oral LD50. Report No. T

- 2488. Product Safety Labs (Agri

- Pharm), 725 Cranbury Road, East Brunswick, NJ.

Acc. No. 248782.

5005716 2056041 Grolleau, G.; Paris, G. (1975) Essais d'intoxication du canard col

- vert~Anas platyrhynchos~L_ a l'aide du coumafene et du chlorophacinone _ ?Trials of intoxication of green collared duck,~Anas platyrhynchos~L_ with coumaphene and chlorophacinone_| Annales de Zoologie

-- Ecologie Animales 7(4):553

- 556.

153369 2056033 Fletcher, D. (1985) Acute Oral Toxicity Study with Technical War

- farin in Bobwhite Quail: Final Report: Study No. 85 QD 56. Un

- published study prepared by Bio

- Life Associates, Ltd. 41 p.



## 71

- 2 Avian Dietary Toxicity

MRID Citation Reference

### Page 38 of 51 117978 2056007 Roth, R.; Shapiro, R. (1982) Avian Dietary LC50 Study with Mallard Ducks: ?Wincon|: Report No. T

- 2390. (Unpublished study re

- ceived Sep 3, 1982
under 3282

- 32; prepared by Nutrition Inter

- national, Inc., submitted by D

Con Co., Inc., Montvale, NJ; CDL:248782

- D)

117979 2056008 Roth, R.; Shapiro, R. (1982) Avian Dietary LC50 Study with Bob White Quail: Report No. T

- 2402. (Unpublished study received Sep 3, 1982 under

3282

- 32; prepared by Nutrition International, Inc., submitted by D

- Con Co., Inc., Montvale, NJ; CDL:248782

- E)

153 365 2056023 Fletcher, D. (1985) 15

- Day Dietary LC50 Study with Technical War

- farin in Bobwhite Quail: Study No. 85 QC 55. Unpublished study prepared by Bio

Life Associates, Ltd. 40 p.

153366 2056024 Fletcher, D. (1985) 19

- Day Dietary LC50 Study with Tec hnical War

- farin in Mallard Ducklings: Study No. 85 DC 56. Unpublished study prepared by Bio

Life Associates, Ltd. 41 p.

156283 2056027 Beavers, J. (1985) A Dietary LC50 Study in the Bobwhite with War

- farin: Final Report: Project No. 205

- 101. Unpublish ed study prepared by Wildlife International Ltd. 20 p.

156285 2056029 Beavers, J. (1985) A Dietary LC50 Study in the Mallard with Warfar

- in: Final Report: Project No. 205

- 102. Unpublished study pre

- pared by Wildlife International Ltd. 16 p.

157812 2056034 Shapiro, R. (1986) Avian Dietary LC50 Study with Mallard Ducks: Wincon (Warfarin): Report No. T

- 5513. Unpublished study pre

- pared by Wildlife International, Ltd. 31 p.

40818001 DER not
located Fletcher, D. (1988) Warfarin Technical: Acute Dietar y LC50 Study in Bobwhite Quail: Project ID: BLAL No. 87 QC 93. Unpublished stu

- dy prepared by Bio

- Life Associates, Ltd. 35 p.

161724 2056035 Shapiro, R. (1983) Avian Dietary LC50 Study with Bob White Quail: Wincon... Warfarin: Report No. T

- 3239. Unpubli shed study pre

- pared by Product Safety Labs. 8 p.



## 71

- 3 Wild mammal toxicity

MRID Citation Reference

2471 ? 2056049 Crabtree, D.G.; Robison, W.H. (19??) Warfarin and its effect on some wildlife species. Pages 167

- 173,~In~Seventeenth North American Wildlife Conference. N.P. (Also~In~unpublished sub

- mission received May 30, 1972 under unknown admin. no.; submit

- ted by Velsicol Chemical Corp., Chicago, Ill.; CDL:230307

- G)



## 71

- 5 Simulated or Actual Field Testing

MRID Citation Reference

### Page 39 of 51 40077201 2056037 Christopher, M.; Balasubramanyam, M.; Purushotham, K. (1984) Toxi

- city of three anticoagulant rodenticides to (male hybrid leg

- horns). A. Angew.
Zool. 71:275

- 281.

44820001 DER not
located

invalid in
reviews Mach, J. (1998) Secondary Hazard Study Using Warfarin

- Killed Prairie Dogs (Cynomys ludovicianus) Fed to Domestic Ferrets Mustela putorius furo): Lab Project Number: 96013. Unpublished study prepared by Genesis Laboratories, Inc. 64 p.

44995003 DER not
located Mac h, J.; Carlet, L. (1997) Secondary Hazard Study Using Warfarin

- Killed
Black

- Tailed Prairie Dogs (Cynomys ludovicianus) Fed to Domestic Ferrets (Mustela putorius furo): Lab Project Number: N97001. Unpublished study prepared by Genesis Laboratories, Inc. 18 p.

44995004 2076444 Mach, J.; March, K. (1997) Secondary Hazard Study Using Warfarin

- Killed
Black

- Tailed Prairie Dogs (Cynomys ludovicianus) Fed to Black

- Billed Magpies (Pica pica): Lab Project Number: N97003. Unpublished study prepared by Genesis Laboratories, Inc. 21 p.



## 72

- 1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

117976 2056005 Shapiro, R. (1982) Static Acute Bioassay for the Toxicity of Wincon ... to Bluegill Sunfish ...: Report No. T

- 2387. (Unpublished study received Sep 3,
1982 under 3282

- 32; prepared by Nutrition International, Inc., submitted by

D

- Con Co., Inc., Montvale, NJ ; CDL:248782

- B)

117977 2056006 Shapiro, R. (1982) Static Acute Bioassay for the Toxicity of Wincon ... to Rainbow Trout ...: Report No. T

- 2392. (Unpublished study received Sep 3,
1982 under 3282

- 32; prepared by Nutrition In

- ternational , Inc., submitted by

D

- Con Co., Inc., Montvale, NJ; CDL:248782

- C)

153363 2056019
2056020 McAllister, W.; Bowman, J.; Cohle, P. (1985) Acute Toxicity of Technical Warfarin to Bluegill Sunfish (Lepomis macrochirus): Report #33306. Unpublished study prepare d by Analytical Bio

- Chemistry Laboratories, Inc. 54 p.

153364 2056021
2056022 McAllister, W.; Bowman, J.; Cohle, P. (1985) Acute Toxicity of Technical Warfarin to Rainbow Trout (Salmo gairdneri): Study No. 33304. Unpublished study prepared by Analytical Bio

- Chemistry Laboratories, Inc. 55 p.

156286 2056030 McAllister, W.; Cohle, P. (1984) Acute Toxicity of Warfarin Techni

- cal to Rainbow Trout(Salmo gairdneri): Report No. 32461. Unpub

- lished study prepared by Analytical Bio

- Chemistry Labs, Inc. 53 p.

156287 2056031 McAllister, W.; Cohle, P. (1984) Acute Toxicity of Warfarin Techni

- cal to Bluegill Sunfish(Lepomis macrochirus): Report No. 32460. Unpublished study prepared by Analytical Bio

- Chemistry Labs, Inc. 53 p.

40098001 2049421 U.S. Fish and Wildlife Service, Columbia National Fishery Research Laboratory (19??) Warfarin. (Unpublished study) Catfish study

No MRID 2056046 U.S. Environmental Protection Agency (1975) Biological Laboratories Report

- Rainbow Trout Acute Toxicity, April 2 8.

### Page 40 of 51 

## 72

- 2 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

117975 2056004 Shapiro, R. (1982) Static Acute Bioassay for the Toxicity of Wincon ... to Daphnia magna: Report No. T

- 2391. (Unpublished study received Sep 3,
1982 under 3282

- 32; prepared by Nutrition In

- ternational, Inc., submitted by

D

- Con Co., Inc., Montvale, NJ; CDL:248782

- A)

153368 2056025 Forbis , A.; Georgie, L.; Burgess, D. (1985) Acute Toxicity of Tech

- nical Warfarin to Daphnia magna: Report #33305. Unpublished study prepared by Analytical Bio

- Chemistry Laboratories, Inc. 44 p.

156288 2056032 Forbis, A.; Georgie, L.; Burgess, D. (1984) Acute Toxicity of War

- farin Technical to Daphnia magna: Report No. 32462. Unpublished study prepared by Analytical Bio

- Chemistry Labs, Inc. 38 p.



# 141

- 1 Honeybee Toxicity

18842 2056003 Atkins, Jr., E.L., L.D. Anderson, E.A. Greywood (1969) Effect of Pestic ides on Apiculture: Project No. 1499; Research Report CF

- 7501. (Unpublished Study Received May 8, 1971 under 1F1174; Prepared by Univ. of California

Riverdale, Dept. of Entomology, Submitted by Ciba Agrochemical Co., Summit, NJ; CDL: 090973

- B).



# Non Guideline Selections

2459 0r 27031
or 29649 2056010
2056011
2056048 Papworth, D.S. (1958) A review of the dangers of warfarin poisoning to animals other than rodents. Royal Society of Health Journal 78(? ):52

- 60. (Also~In~unpublished submission received Fe b 7, 1963 under unknown admin. no.; submitted by McLaughlin Gormley King Co., Minneapolis, Minn.; CDL:221990

- D)

2469 2056002 Evans, J.; Ward, A.L. (1967) Secondary poisoning associated with anticoagulant

- killed nutria. Journal of the American Veterinary Medical Association 151(7):856

- 861. (Also~In~unpublished sub

- mission received May 30, 1972 under unknown admin. no.; submit

- ted by Velsicol Chemical Corp., Chicago, Ill.; CDL:230307

- E)

2838 Referenced but

no DER Hein, L.; Koch, R.; Krieger, C.H. (1952) Tomorin, Cumopyrin, War

- farin and the Methoxy Derivative of Warfarin: Biological Studies. (Unpublished study including second progress report, received Mar 17, 1952 under unknown admin. no., prepared by Wisconsin Alumni Research Foundation, submitted by Ciba

- Geigy Corp., Greensboro, N.C.; CDL:104673

- B)

2839 Referenced but

no DER Hein, L.; Derse, P.; Krieger, C.H. (1952) Warfarin and Tomorin Biological Studies: Fourth Progress Report. (Unpublished study received Feb 20, 1952 under unknown admin. no.; pre pared by Wisconsin Alumni Research Foundation, submitted by Ciba

- Geigy Corp., Greensboro, N.C.; CDL:104665

- A)

5988 2056038 Brock, E.M. (1965) Toxicological feeding trials to evaluate the hazard of

### Page 41 of 51 secondary poisoning to gopher snakes, Pituophis cate

- ? nifer ?. Copeia ? (2):244

- 245. (Also In unpublished submis

- sion received Apr 23, 1976 under

6704

- 78; submitted by U.S. Dept. of Interior, Fish and Wildlife Service, Washington, D.C.; CDL:224031

- L)

31300 DER not
located

- more of a report on
incidents Hay ne, D.W.; Copple, H.; Thornton, G.W.; et al. (1976) (Letters Concerning Toxicity to Dogs following Accidental Ingestion). (Unpublished study received Mar 20, 1980 under 876

- 184; prepared in cooperation with North Carolina State Univ., Institute of Statisti cs and others, submitted by Velsicol Chemical Corp., Chicago, Ill.; CDL:242305

- A)

5001730 Open lit Warkany, J. (1976) Warfarin embryopathy. Teratology 14:205

- 209.

5001784 Open lit Jennings, D.S. (1972) Warfarin poisoning in pigs ?letter| Veterinary Rec ord 90(4):110.

146380 2056017 Beck, L. (1980) Primary Eye Irritation. Zoecon Rat and Mouse Bait: Project
No. 1596

- B. Unpublished Study Prepared by Elars Bioresearch Laboratories,

Inc.

5001952 2056039 Phillips, D., J. Rowe (1976) Warfarin: A Question of Balance. New Scientist 70(1001): 400

- 401.

5001953 2056040 Phillipson, J., D. Wood (1970) Poisoning Grey Squirrels: A Threat to Wildlife? New Scientist 70(1001): 398

- 400

5006274 2056042 Zatsepin, V.G., D.F. Trakhanov, N.I. Nikiforov (1977) Izuchenie toks ichnosti deratizatsionnykn yaooy glya pushnykh zverei. Study on Toxicity of Oeratization Poisons to Fur

- bearing animals. All Union Scientific Research Institute of Veterinary Sanitation 57: 127

- 132.

5006278 2056043 Telle, H.J. (1954) Neue Rattenekaempfu ngsmittel

– New Rodenticides Deutscne Gesundheitswesen 9(24): 769

- 771.

5008022 205044 Fowler, M.E. (1975) Toxicities in Exotic and Zoo Animals. Veterinary Clinics of North America 5(4): 685

- 698.

5009867 2056045 Uyeda, S. (1956) Bird Problems with use of Warfarin Cats. Pages 19

- 20. In Hawaiian Sugar Technologists Report No. 15. Honolulu, Hawaii: Hawaiian Sugar Technologists.

143276 2056012 Lorgue, G. (1984) Comparative Toxicity in the Pig after Repeated Oral Inge stion of Brodifacoum, Bromadiolone and Warfarin. Unpublished
Translation of Toxicities Comparees Chez le Porc Par Ingestions Orales Repetees de Brodifacoum, Bromadiolone et coumafene Prepared by Lyon National Veterinary School Laboratory of Toxicology. Lip ha Report No. 85

- 012.

146377 2056013 Beck, L. (1980) Rat Acute Oral Toxicity. Zoecon Rat and Mouse Bait: Project
No. 1596

- D. Unpublished Study Prepared by Elars Bioresearch Laboratories,

Inc.

146378 2056014 Beck, L. (1980) Acute Dermal Toxicity. Zoecon R at and Mouse Bait: Project
No. 1596

- C. Unpublished Study Prepared by Elars Bioresearch Laboratories,

Inc.

146379 2056015 Beck, L. (1980) Acute Dermal Irritation. Zoecon Rat and Mouse Bait: Project
No. 1596

- A. Unpublished Study Prepared by Elars Bioresearc h Laboratories,

Inc.

### Page 42 of 51 148098 2056016 Shapiro, R. (1985) Letter Sent to S. Palmateer Dated July 1, 1985; Antidotal Effect of Warfarin used in Avian Toxicology Studies Performed for the d

- Con Co., Inc.: (Antidotal Effect of Vitamin K in the Basal Diets to Counteract or Modify the Effects of Warfarin in Avaian Wildlife Studies). Prepared by Product Safety Labs.

### Page 43 of 51 

# Appendix A : Summary of Ecotoxicity Data for Warfarin

Table A

- 1. Aquatic Toxicity Profile for Warfarin

Assessment Endpoint Tested Species Toxicity Value (95% CI)
Used in Risk Assessment Acute
Classification Reference (MRID)

Freshwater Organisms

Acute Toxicity to
Fish and Aquatic

- phase Amphibians Rainbow trout (Oncorhynchus mykiss) 96

- hr LC 50 > 16 mg/L Slightly toxic 00156284

Bluegill sunfish ( Lepomis
macrochirus ) LC 50 > 17 mg/L Slightly toxic 00156287

Acute Toxicity to Aquatic
Invertebrates Water flea ( Daphnia magna) 48

- hr LC 50 > 17 mg/L Slightly toxic 00153368



### Table A

- 2. Avian Acute Oral Toxicity Studies

Rodenticide/

Species %
a.i. LD50, mg/kg (95% CI) Probit slope (95% CI) Average Body Weight (day=0) Study length
and Time to

death and (study length) MRID/
Reference and
classification Comments

Northern bobwhite quail 100 >2000 156284, acceptable

### Page 44 of 51 

### Table A

- 2. Avian Acute Oral Toxicity Studies

Rodenticide/

Species %
a.i. LD50, mg/kg (95% CI) Probit slope (95% CI) Average Body Weight (day=0) Study length
and Time to

death and (study length) MRID/
Reference and
classification Comments

Northern bobwhite quail 100 > 2150 153369, acceptable

Mallard duck Tech. 621 248782, acceptable

Mallard duck 10 120 5005716, supplemental Not conducted with technical

Chicken (domestic) 942 Bai and
Krishnakumari 1986 , have paper, not reviewed

### Page 45 of 51 

### Table A

- 3. Avian Acute Dietary Toxicity Studies

LC50 dietary
Rodenticide/

Species % a.i. LC50, mg/kg (95% CI) Probit slope (95% CI) Average Body Weight (day=0) Time to death and (study length) MRID/Referen
ce and
classification Comments

Northern bobwhite quail 100 625 NA 33 g 15 day study, most deaths days
3

- 7, one day 10 153365, acceptable fed a diet described as ‘vit K

- deficient (meaning no vit K in feed supplement), very ‘flat’ dose response curve

Northern bobwhite quail Tech. 3000 117979, supplemental

Northern bobwhite quail 100 3900 161724, acceptable

Northern bobwhite quail 100 6690 (2537, 551690) 1.1 (0.3, 1.9) 21 g 15 day study, deaths from day

3

- 9 156283, supplemental, fed standard diet, contained 8.8 mg/kg of synthetic Vit K (menadione sodium bisulfate), may have been sufficient to mitigate effects of warfarin

Mallard duck

100 890 NA 19 day study, deaths from day
3

- 16 153366, acceptable, fed a diet described as ‘vit K

- deficient (meaning no vit K in feed supplement), very flat dose response curve

Mallard duck Tech. 1726 157812, acceptable

Mallard duck 100 > 5000 156285, supplemental



### Table A

- 4. Mammalian Acute Oral Toxicity Studies

Rodenticide/

Species % a.i. LD50, mg/kg (95% CI) Probit slope (95% CI) Average Body Weight (day=0) Time to death and (study length) MRID/Refer

ence and
classification Comments

Laboratory

rat 100 3.0 (male) 196 MRID 05002272 (Gaines 1960)

GS 0011

- 107, Acceptable
also included in Gaines 1969

Laboratory

rat 2.5

- 5.0(females) 00143093 mortality was not monotonic

– suggestive of study issues.

### Page 46 of 51 

### Table A

- 4. Mammalian Acute Oral Toxicity Studies

Rodenticide/

Species % a.i. LD50, mg/kg (95% CI) Probit slope (95% CI) Average Body Weight (day=0) Time to death and (study length) MRID/Refer
ence and
classification Comments

Laboratory

rat 35.7
41.9 EPA 1982 Beltsville report (variation in warfarin), not reviewed

Laboratory

rat NA 512 (male) <10 (female) NA 200 14 day
observation
Deaths 1

- 10 days 00146977 Animals fed lab chow Male value originally 450

- 680, now calculated with binomial
estimate

Cat 100 < 2.5 1.75

- 3.30 kg went to 14 days
mortalities btw

1

- 10 days 00002461 (Acceptable) Only 2 cats per dose level, 1974 study. (100% mortality at 2.5) (Til et al 1974)



### Table A

- 5. Mammalian Acute Dietary Toxicity Studies

Rodenticide/

Species %
a.i. LC50, mg/kg (95% CI) Probit slope (95% CI) Average Body Weight (day=0) Time to death and (study length) MRID/Reference
and classification Comments

Laboratory rat (Albino) 98 4.41 (3.43

- 5.64) 5.4 (2.8, 8.0) 60

- 74g Observed 14 days, mortalities days 3

- 9 Teeters 1981 (TNM 126) Supplementa1

Laboratory rat (Albino) 98 5.43 (4.23

- 7.00) 5.1 (2.8, 7.5) 91

- 120g Observed 14 days, mortalities days 3

- 10 Teeters 1981 (TNM 68) Supplementa1

Laboratory rat (Albino) 98 5. 91 (4.66, 7.51) 5.9 (3.9, 8.8) 61

- 75 g Observed 14 days, mortalities days 3

- 9 Teeters 1981 (TNM 122) Supplementa1

Laboratory rat (Albino) 98 6.03 (4.45

- 8.20) 3.6 (2.0, 5.3) 81

- 116 g Observed 14 days, mortalities days 4

- 9 Teeters 1981 (TNM 50) Supplementa1

Mink 11.7 (9.2, 15.0) 2.0 Aulerich et al. 1987 (E039689) Not in comparative

### Page 47 of 51 

### Table A

- 5. Mammalian Acute Dietary Toxicity Studies

Rodenticide/

Species %
a.i. LC50, mg/kg (95% CI) Probit slope (95% CI) Average Body Weight (day=0) Time to death and (study length) MRID/Reference
and classification Comments

Black

- tailed prairie dogs 99 97.6 (23.7, 185.1) 1.38 (0.5, 2.3) > 675 g and 775 g for

adult
females and

males, respectively 15

- day feeding exposure, observed

total 25 days.
Mortalities from 8

- 22 days E66881 Mach et al. 2002, Qualitative NEED TO B E SURE CAN FIND REVIEW

### Page 48 of 51 

# 13 Appendix B. Screening Level Models to Evaluate Potential Importance of Drinking Water and Inhalation Exposure Pathways

SIP ( Screening Imbibition Program, v1.0) Inputs and Conclusions
Table 1. Inputs

Parameter Value

Chemical name Warfarin

Solubility (in water at 25 o C; mg/L) 17

Mammalian LD 50 (mg/kg

- bw) 3
Mammalian test species laboratory rat
Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg

- bw) 0
Mammalian test species
Body weight (g) of "other" mammalian species

Avian LD 50 (mg/kg

- bw) 621
Avian test species mallard duck
Body weight (g) of "other" avian species
Mineau scaling factor 1.15

Mallard NOAEC (mg/kg

- diet) 0
Bobwhite quail NOAEC (mg/kg

- diet) 0
NOAEC (mg/kg

- diet) for other bird species 0
Body weight (g) of other avian species
NOAEC (mg/kg

- diet) for 2nd other bird species
Body weight (g) of 2nd other avian species

### Page 49 of 51 Table 2. Mammalian Results

Parameter Acute Chronic
Upper bound exposure (mg/kg

- bw) 2.9240 2.9240
Adjusted toxicity value (mg/kg

- bw) 2.3075 0.0000
Ratio of exposure to toxicity 1.2672 0.0000

Conclusion* Exposure through drinking water alone is a potential

concern for mammals Due to insufficient data, risk cannot be precluded

Table 3. Avian Results

Parameter Acute Chronic
Upper bound exposure (mg/kg

- bw) 13.7700 13.7700
Adjusted toxicity value (mg/kg

- bw) 322.4390 0.0000
Ratio of exposure to acute toxicity 0.0427 0.0000

Conclusion* Drinking water exposure alone is NOT a potential
concern for birds Due to insufficient data, risk cannot be precluded

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. Therefore, when aggregated with other routes ( i.e ., diet, inhalation, dermal), pesticide exposure through drinking water may contribute to a total exposure that has potential for effects to non

- target animals.

### Page 50 of 51 

### Welcome to the EFED

Screening Tool for Inhalation Risk This tool is designed to provide the risk assessor with a rapid method for determining the potential significance of the inhalation exposure route to birds and mammals in a risk assessment.



# Input

Application and Chemical Information

Enter Chemical Name warfarin

Enter Chemical Use rodent control
Is the Application a Spray? (enter y or n) n If Spray What Type (enter ground or air) air
Enter Chemical Molecular Weight (g/mole) 308.33
Enter Chemical Vapor Pressure (mmHg) 1.16E

- 07
Enter Application Rate (lb a.i./acre) 0.025

Toxicity Properties

Bird

Enter Lowest Bird Oral LD 50 (mg/kg bw) 621
Enter Mineau Scaling Factor 1.15
Enter Tested Bird Weight (kg) 1.58

Mammal

Enter Lowest Rat Oral LD 50 (mg/kg bw) 3

Enter Lowest Rat Inhalation LC 50 (mg/L) 0.005
Duration of Rat Inhalation Study (hrs) 4
Enter Rat Weight (kg) 0.35

### Page 51 of 51 

# Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 1.92E

- 03

Maximum 1

- hour Vapor Inhalation Dose (mg/kg) 2.42E

- 04

Adjusted Inhalation LD 50 4.16E+00

Ratio of Vapor Dose to Adjusted Inhalation LD 50 5.82E

- 05 Exposure not Likely Significant

Maximum Post

- treatment Spray Inhalation Dose (mg/kg) not applicable

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD 50 not applicable not applicable



### Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 1.92E

- 03

Maximum 1

- hour Vapor Inhalation Dose (mg/kg) 3.04E

- 04

Adjusted Inhalation LD 50 2.98E

- 01

Ratio of Vapor Dose to Adjusted Inhalation LD 50 1.02E

- 03 Exposure not Likely Significant

Maximum Post

- treatment Spray Inhalation Dose (mg/kg) not applicable

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD 50 not applicable not applicable