UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OCT 1 4 2015 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: BEAD Chemical Profile for Registration Review: Warfarin and Warfarin Sodium 

Salts (086002 and 086003) Amended 

FROM: 

THRU: 

TO: 

Colwell Cook, Entomologist~~ Biological Analysis Branch 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief d -. /1 ~ 4- fl "4- J ~ 5 

Biological An_alysis BraPZhYJ- " . /" 

Biological and Economic Analysis Division (7503P) 

Caitlin Newcamp, Chemical Review Manager 

Risk Management and Implementation Branch II 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel date: July 15, 2015 

SUMMARY 

The Biological and Economic Analysis Division (BEAD) Chemical Profile (BCP) provides an 

overview of the pest management role for warfarin and warfarin sodium salt. Information 

provided in this BCP may be used by stakeholders (e.g. users and registrants), OPP risk and 

benefit assessors, OPP risk managers, and the general public during the Registration Review 

process of this pesticide. This amended document corrects the use sites from the earlier version 

(Cook, 2015). 

Warfarin and its sodium salt are anticoagulant rodenticides, first registered in the U.S. in 1950 

and 1954, respectively. There are no current active registrations for warfarin sodium salt. There 

are 13 active end-use product registrations for warfarin; Warfarin is registered for use in 

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controlling rodents (e.g. rats, mice, voles, and moles), in and around homes and buildings, 

agricultural and animal premises, commercial and industrial sites, and transport vehicles. 

Warfarin is formulated as granules, pellets/tablets, microencapsulated pellets, and solution (gel). 

It may be applied in bait stations or by hand, and a syringe is used to apply the gel formulation 

into active underground mole burrows. · 

Warfarin was the first anticoagulant rodenticide to be developed and subsequently is a first 

generation anticoagulant rodenticide. Anticoagulants interfere with the formation of 

prothrombin and thus the blood clotting process. This leads to internal bleeding and death. 

W arfarin, and all the first generation anticoagulant rodenticides, require multiple feeding over 

several days to reach a toxic dose. Because warfarin was the first rodenticide, there are some 

populations of rodents that may demonstrate some level of resistance, but the extent is not known 

(Corrigan, 2001; Heiberg, 2009). 

BEAD has previously assessed rodenticides. Chiri (2006) assessed the pest status of rodents, 

integrated pest management of rodents, and evaluated the use of rodenticide bait. A second 

document in 2006 considered the cost impacts.for the Rodenticide Mitigation Decision (RMD) 

(Chiri, et al., 2006). BEAD (Chiri, et al., 2008) responded to public comments concerning the 

proposed RMD for nine rodenticides. Later that year BEAD published an addendum to the 

impact analysis that determined the amended proposed mitigation of requiring bait stations 

would not impose constraints on rodent control programs but could increase costs to residential 

consumers; although homeowners could switch to less expensive snap traps (Rim, 2008). BEAD 

published an impact analysis of mitigations of the proposed Notice of Intent to Cancel selected 

residential consumer rodenticide products (Cook and Hill, 2011) which reached the same 

conclusion as Rim (2008). 

BEAD has no available usage data for warfarin. General information on why warfarin is · 

selected over other rodenticides; where it is used; how it is applied; and when it is used would be 

helpful for assessments. 

References: 

Chiri, A. A. January 23, 2006. Analysis of rodenticide bait use. BEAD Memorandum to 

SRRD/Kelly Sherman. Located at: http://www.regulations.gov/#!documentDetail;D~EPA-HO- ' 

0 PP-2006-09 5 5-0004. 

Chiri, A. A., J. Becker, and Jin Kim. Sept. 20, 2006. Impact assessment foi; proposed 

· rodenticide mitigation (DP 332577). BEAD Memorandum to SRRD/Kelly Sherman. Located 

at: http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2006-0955-0003. 

Chiri, A. A., J. Becker, and E. Rim. January 3, 2008. Response to comments submitted to 

Docket No. EPA-HQ-OPP-2006-0955, proposed risk mitigation decision for nine rodenticides. 

BEAD Memorandum to SRRD/Kelly Sherman. Located at: 

http://www.regulations.gov/#!documentDetail;D=EP A-HQ-OPP-2006-095 5-0755. 

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Cook, C. 2015. BEAD chemical profile for reregistration review: warfarin and warfarin sodium 

salts (086002 and 086003). BEAD Memorandum to PRD/Caitlin Newcamp, dated July 16, 

2015. 

Corrigan, R. M. 2001. Rodent Control: A Practical Guide for Pest Management Professionals. 

GIE Media, Cleveland. 351 pp. 

Heiberg. A-C. 2009. Anticoagulant resistance: a relevant issue in sewer rat (Rattus norvegicus) 

control? Pest Manag Sci 65(4):444-449. 

Rim, E. May 20, 2008. Addendum to impact assessment for proposed rodenticide mitigation 

(DP 332574). BEAD Memorandum to SRRD/Kelly Sherman. Located at: 

http://www.regulations.gov/#!documentDetai~;D=EPA-HQ-OPP-2006-0955-0754. 

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