UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

FEB 2 3 2016 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

BEAD Chemical Profile for Registration Review of the Second Generation 

Anticoagulant Rodenticides: Brodifacoum (112701 ), Bromadiolone (112001 ), 

Difenacoum ( 119901 ), and Difethialone ( 128967) 

Colwell Cook, Biologist e ~~ Biological Analysis Branch 

Elizabeth Hill, Economist fbf (>.-. \IV\ \~' Economic Analysis Branch lJ' j v-' 

Biological and Economic Analysis Division (7503 

Mark Suarez, Acting Chief \ \ . 

Biological Analysis Branch N \ 

Timothy. 

Economic Kiely, Analysis C~ief Branch ~· .,, \ VV\. 

11 11 l ~ 

Biological and Economic Analysis ivision (750 P) 

I 

TO: Ricardo Jones, Chemical Review Manager 

Risk Management and Implementation Branch I 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel Date: February 10, 2016 

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SUMMARY 

The second generation anticoagulant rodenticides (SGARs) were developed as a result of rodents 

developing resistance to warfarin and other first-generation anticoagulants. The SGARs 

registered in the U.S. include brodifacoum, bromadiolone, difenacoum, and difethialone. 

Brodifacoum was first registered in 1979, bromadiolone was registered in 1980, difethialone in 

1995, and difenacoum in 2007. These compounds are registered for the control of commensal 

rodents and work by interfering with the blood clotting mechanism. The primary use sites for 

these rodenticides are in and near human habitat, as well as in island eradication programs. 

INTRODUCTION 

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

overview of the pest management roles and quantitative usage information for SGARs. The 

BCP includes available public and/or private use and usage data for SGARs and a general 

discussion of biological aspects, intended to describe the role of this chemical in pest 

management. Additional information on use is available in the SOAR Label Data Report 

provided in the public docket for this chemical. Information provided in this BEAD Chemical 

Profile (BCP) may be used by stakeholders (e.g., users and registrants), Office of Pesticide 

Programs (OPP) risk and benefit assessors, OPP risk managers, and the general public during the 

Registration Review process of this pesticide. This document builds upon the data already 

provided in the Label Use Information System (LUIS) reports that BEAD provides to the 

Registration Review teams. The document is based on information and data available to BEAD 

as of January 15, 2016. 

HISTORY OF BEAD ASSESSMENTS FOR SGARs 

The SGARs, brodifacoum, bromadiolone, and difethialone, have been assessed several times by 

BEAD. The registered SGARs were re-registered in 1998 (EPA, 1998), but not all registrants 

agreed to mitigation measures. BEAD conducted several assessments to support the EPA's 2008 

Risk Management Decision·for Ten Rodenticides (RMD) (EPA, 2008), which then included 

difenacoum (Wasem, 2911). BEAD concluded that chemical rodenticides are a critical 

component of rodent management; there is little difference between the performance of the 

rodenticide active ingredients; and rodenticides are generally interchangeable and can be 

considered alternatives to one another for homeowner use (Chiri, 2006; Chiri, et al. 2006; Chiri, 

et al. , 2008). Some registrants did not accept the mitigation from the RMD (EPA, 2008). In 

2011 , Cook and Hill (2011) considered the impact of cancellation of selected consumer 

(homeowner) products in support of the Agency's proposed Notice of Intent to Cancel (EPA, 

2011). Specifically, the mitigation required that SGARs no longer be available in the consumer 

market, that rodenticides must be sold in block form and packaged with a bait station. The 

assessment concluded that the incremental costs would be minimal for consumers having to 

switch from rodenticide products currently available to those that would be in compliance with 

the mitigation. 

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A search of the BEAD database for previous documents for SGARs indicates that there are no 

records of prior Section 18 Emergency Exemption Requests. Recent Section 18 Emergency 

Exemption Requests might suggest that a chemical is important for the uses granted in the 

request; however, a lack of Section 18 Emergency Exemption Requests is not an indication of 

the relative importance of the chemical. 

COMMON FORMULA TIO NS AND APPLICATION METHODS 

The second generation anticoagulant rodenticides are formulated mainly as a solid bait, such as 

pellets, tablets, or blocks. These products must be in locations out of reach of children, pets, 

domestic animals, and nontarget wildlife or in tamper-resistant bait stations. Bait stations are 

mandatory in outdoor, above-ground use. 

USE SITES 

Agricultural Use Sites: 

The SGARs are registered to be used to control rodents in and around agricultural 

buildings/structures, farm equipment, and in uncultivated agricultural areas. 

Non-Agricultural Use Sites: 

The SGARs are registered for use in commercial/institutional/industrial premises/equipment 

(indoor and outdoor), commercial transportation facilities-nonfeed/nonfood, commercial 

transportation vehicles, food processing plant premises (nonfood contact), household/domestic 

dwellings indoor and outdoor premises, and uncultivated nonagricultural areas. They may be 

used around refuse/solid waste containers. Brodifacoum, bromadiolone, and difethialone may be 

used in sewage systems; however, difenacoum is not registered for this use site. 

SGAR USAGE 

The rodenticide market has been impacted by recent EPA regulation in 2011 , limiting the 

availability of SGARs to the general public. Although data are not available on SGAR usage, it 

is known that prior to the 2011 mitigation, brodifacoum was the lead consumer rodenticide, and 

bromadiolone was the lead professional applicator rodenticide (Kline & Company, 2006; Kline 

& Company, 2004). 

BIOLOGICAL ASPECTS RELEVANT TO SGARs 

The SGARs are registered to control primarily commensal rodents, i.e. Norway rats, roof rats, 

and house mouse in residential and commercial settings and in and around agricultural buildings. 

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Anticoagulant rodenticides interfere with the blood clotting mechanism, specifically impacting a 

protein, vitamin K epoxide reductase (Vkor). Vkor converts the vitamin K epoxide back to 

vitamin K, which is an essential cofactor for several blood clotting factors. 

The SGARs are potent enough that rodents may ingest a lethal dose in a single night's feeding; 

however the rodents take nearly a week to die. Therefore, the rodents may obtain doses much 

larger than necessary for control. Rodents with elevated level of anticoagulants are then a hazard 

if consumed by non-target wildlife. 

ROLE OF SGARs IN PEST MANAGEMENT 

Rodents may be both public health pests and agricultural pests. Some rodents may carry 

diseases, or may be injurious to humans. Rodents will consume and contaminate stored food 

supplies; disturb soil through their burrowing activities; damage houses and other structures; and 

prey on native species, including birds that nest on oceanic islands. These animals are adapted to 

live in close proximity to humans and therefore have nearly unlimited food and shelter. 

Rodenticides are a critical component of managing rodent pests. Rodenticide baits are useful for 

reducing rodent numbers, especially when infestations are high. Many municipalities and 

communities have integrated pest management programs that employ a combination of 

sanitation, exclusion, habitat medication, trapping, and baiting (Illinois Department of Public 

Health, 2005 ; Kass, et al. 2009; New York City Department of Health and Mental Hygiene, 

undated; New York City Department of Health and Mental Hygiene, 2011). Homeowners may 

control rodents with a combination of traps (snap or glue), and baits; but SGARs are critical to 

managing rodents in and around agricultural buildings, food manufacturing facilities, and food 

handling establishments. In addition, SGARs are needed by Pest Control Operators. 

Rodenticides are also necessary to remove invasive rats and mice that have been introduced on 

oceanic islands to protect native species (Donlan, et al., 2003 ; Howald, et al., 2007; Department 

of Interior/ National Park Service, 2000). 

INFORMATION THAT MAY BE USEFUL FOR BEAD'S FUTURE WORK ON 

SGARs 

BEAD would be interested in learning about preferences of companies and what drives the 

selection of one SGAR over another SGAR. More details on when and why these SGARs are 

used would be helpful for future BEAD assessments. 

REFERENCES: 

Chiri, A. 2006. Analysis of Rodenticide Bait Use. Memorandum to Kelly Sherman, Special 

Review and Registration Division. 

Chiri, A., Becker, J. and Kim, J. 2006. Impact Assessment for Proposed Rodenticide 

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Mitigation. Biological and Economic Analysis Division, Office of Pesticide 

Programs, U.S. Environmental Protection Agency. Available at: 

http://www.regulati ons. gov /f dmspub 1 ic/ component/main ?main= DocketDetail&d= 

EPA-HQ-OPP-2006-0955. 

Chiri, A. , Becker, J. and Rim, E. 2008. Response to Comments submitted to Docket No. 

EPA-HQ-OPP-2006-0955, Proposed Risk Mitigation Decision for Nine 

Rodenticides. Biological and Economic Analysis Division, Office of Pesticide 

Programs, U.S. Environmental Protection Agency. 

Cook, C. and E. Hill. Oct. 31 , 2011. Impact assessment of the draft notice of intent to cancel 

selected residential consumer rodenticide products to control commensal rodents. Memorandum 

to Russell Wasem, PRD. Available at: http://www.regulations.gov/#!documentDetail;D=EPAHQ-OPP-2011-0718-0013 . 

Department of the Interior/ National Park Service. 2000. Anacapa Island Restoration Plan, 

Final Environmental Impact Statement, Channel Islands National Park, Ventura County, CA; 

Notice of Availability. Available at: 

http://www. federalregister. com/B rowse/Document/usa/na/fr/2000/1 0/ 12/00-2614 3. Accessed: 

February 4, 2016. 

Donlan, C.J., G. R. Howald, B. R. Tershy, D. A. Croll. 2003. Evaluating alternative 

rodenticides for island conservation: roof rat eradication from the San Jorge Islands, Mexico. 

Biological Conservation 114 (1): 29-34. 

EPA. 1998. Rodenticide Cluster R.E.D. Facts. Available at: 

http://archive.epa.gov/pesticides/reregistration/web/pdf/21 OOfact. pdf. 

EPA. 2008. Risk Mitigation for Ten Rodenticides. May 28, 2008. Available at: 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2006-0955-0764. 

EPA. 2011 . Rodenticides. Draft notice of intent to cancel and denial. Available at: 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2011-0718-0017. 

Howald, G. , C. J. Donlan, J. P. Galvan, J.C. Russell, J. Parkes, A. Samaniego, Y. Wang, D. 

Veitch, P. Genovesi, M. Pascal, A. Saunders, and B. Tershy. 2007. Invasive Rodent 

Eradication on Islands. Conservation Biology 21(5):1258-1268. 

Illinois Department of Public Health. 2005. Prevention and Control: Municipal Rodent 

Management. Available at: http://www.idph.state.il. us/envhealth/pcmunicipal rodents.htm. 

Kass, D, W McKelvey, E Carlton, M Hernandez, G Chew, S Nagle, R Garfinkel, B Clarke, J 

Tiven, C Espino, and D Evans. 2009. Effectiveness of an integrated pest management 

intervention in controlling cockroaches, mice, and allergens in New York City public housing. 

Environmental Health Perspectives 117(8):1219-1225. 

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Kline & Company. 2006. Consumer Markets for Pesticides and Fertilizers USA: Rodenticides. 

Kline & Company. 2004. U.S. Professional Pest Management Market: Rodenticides. 

New York City Department of Health and Mental Hygiene. Undated. Preventing rats on your 

property - a guide for property owners and tenets. Publication number EHS6356051-

408.A vailable at: http://www.nyc.gov/html/doh/downloads/pdf/pest/rodent_ control.pdf. 

Accessed: 6/21 /2011 . 

New York City Department of Health and Mental Hygiene. 2011. Who is responsible for 

preventing rats? Available at: http://www.nyc.gov/html/doh/html/rats/responsible.shtml. 

Accessed: 6/21/2011. 

Wasem, R. 2011. Regulatory history of ten rodenticides. Memorandum to Federal Insecticide 

Rodenticide and Fungicide Act Scientific Advisory Panel. Available at: 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2011-0718-0015 . 

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