Charge Questions

SAP on Rodenticide NOIC – Nov. 29 – Dec. 1, 2011

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EPA’s draft Notice of Intent to Cancel (NOIC) proposes to cancel 20 rodenticide 

products and EPA’s draft Notice of Denial proposes to deny 4 rodenticide products. The 

products are all subject to this action because they cause unreasonable risk to humans, 

pets, and/or non-target wildlife when used by residential consumers. In the 2008 Risk 

Mitigation Decision for Ten Rodenticides (RMD), EPA determined that the unreasonable 

risks owing to primary exposure of children, pets, and non-target wildlife could be 

mitigated through the use of tamper-resistant bait stations reasonably expected to not 

release rodenticide bait except for bait removed by target rodents and minor quantities of 

crumbs created by target rodent, and the unreasonable risks owing to secondary exposure 

of non-target wildlife could be mitigated through the elimination of the active ingredients 

brodifacoum, difethialone, bromadiolone, or difenacoum.

1

 All references to 

“conforming” or “non-conforming” in these charge questions refer to whether a product 

conforms to these two risk mitigation measures as described in the RMD. Please 

consider whether the data currently available adequately supports the Agency’s analyses 

and conclusions.

Risks to Humans

1. Does the Agency’s analysis of the mammalian toxicity studies and human incident 

reports provide a reasonable basis for concluding that exposure to warfarin, 

brodifacoum, difethialone and/or bromethalin can cause health effects in individuals 

who ingest these rodenticides? Are the adverse effects described in the children’s 

incident reports [e.g., anemia, melena (bloody stool), hematemesis (vomiting of 

blood)], credible consequences of exposure to these active ingredients? Please 

provide the basis for your conclusions.

2. The human incident report summarizes a number of data and information sources 

used in the analyses and reviews conducted. Based on the incident report analysis, 

EPA has concluded that there are a large number of rodenticide exposure incidents 

that involve children less than 6 years old. While exposure generally results in no 

clinical harm to children, the exposures to rodenticides have the potential to result in 

severe outcomes and/or require medical care or follow-up. Does the SAP concur with 

the EPA’s conclusions regarding the extent of exposures, potential severity of effects, 

and degree of risks posed to humans? Are the conclusions reached reasonably 

supported by the data analysis? Please explain the basis of your position.

3. Based on the human incident report, EPA concludes that the use of conforming 

rodenticide products will reduce the risk rodenticides pose to humans by reducing the 

opportunity for exposure. Is it reasonable to expect that limiting consumer use to 

conforming rodenticide products will generally reduce the opportunity for exposure 

of humans to commensal rodenticide products? Please provide the basis for your 

conclusions.

 1 The RMD also included other risk mitigation measures not at issue here.
Charge Questions

SAP on Rodenticide NOIC – Nov. 29 – Dec. 1, 2011

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Risks to Pets

4. The pet incident report summarizes a number of data and information sources used in 

the analyses and reviews conducted. The EPA concludes that there is a high 

frequency of reported pet incidents involving rodenticides, many of which result in 

severe outcomes; this conclusion is further supported by the information reported in 

the open literature as well as the characterization of primary acute risk. Does the SAP 

concur with EPA’s conclusions of the risks posed to pets by non-conforming 

rodenticide products? Are the conclusions reached reasonably supported by the data 

analysis? Please explain the basis of your position.

5. The pet analysis has relied on the assessment of risks to wildlife from primary 

exposure as one line of evidence to characterize primary acute risk to pets from nonconforming rodenticide products. Is it reasonable to conclude that risks to pets are 

similar to risks to non-target mammalian wildlife, assuming comparable exposures? 

Please explain the basis of your conclusions.

6. Based on the pet incident report, EPA concludes that the use of conforming 

rodenticide products will reduce the opportunity for exposure of pets to rodenticides. 

Is it reasonable to expect that limiting consumer use to conforming rodenticide 

products will generally reduce the opportunity for exposure of pets to commensal 

rodenticide products? Please provide the basis for your conclusions.

Risks to Wildlife

7. The EPA has conducted a deterministic risk assessment to evaluate the risks of acute 

toxicity to non-target mammals and birds from primary exposure to non-conforming 

rodenticide products. In its assessment, EPA calculated risk quotients on an acute 

oral dose and acute dietary exposure basis for birds and mammals and further 

characterized the opportunity for exposure at lethal levels based on factors including 

the number of days required to feed and the mass of pesticide required to be 

consumed to reach lethal thresholds. Using the best available data, EPA made 

assumptions relative to toxicity, accumulation, and clearance of the pesticides that are 

material to the exposure and effects modeling in the deterministic primary risk 

assessment. 

a. Please comment on the reasonableness of the following aspects of EPA’s primary 

exposure deterministic risk assessment: 

• Selection of toxicity endpoints for species common to all assessed 

chemicals in light of the incomplete overlap across available data sets; 

• The use of allometric toxicity scaling approaches for birds; 
Charge Questions

SAP on Rodenticide NOIC – Nov. 29 – Dec. 1, 2011

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• The reliance on mammalian first order liver or plasma elimination half 

lives to estimate whole body wildlife (birds and mammals) elimination 

rates for anticoagulants and bromethalin, respectively;

• The use of the time required and the consumption of rodenticide mass 

required to reach lethal thresholds as a means of comparing the relative 

risks of acute mortality following consumption of rodenticide bait; 

b. In addition, does the Panel concur with EPA’s analysis and conclusion that use of 

non-conforming rodenticide products (i.e., not in bait stations) can cause adverse 

effects to non-target wildlife? Please provide a basis for your conclusions. 

 

c. Is it reasonable to expect that placing rodenticide products in tamper resistant bait 

stations with formulations expected to remain in the bait station will generally 

reduce the opportunity for primary exposure of wildlife to commensal rodent 

control products? Please provide a basis for your conclusions.

8. The EPA has conducted a deterministic risk assessment to evaluate risks of acute 

toxicity to non-target mammals and birds from secondary exposure to nonconforming rodenticide products. In its exposure estimate, EPA used both calculated 

theoretical contamination levels in prey and available empirical data. EPA also 

characterized the secondary exposure risk using secondary feeding studies and factors 

including the number of contaminated animals required to be consumed to reach 

lethal exposure thresholds. For these analyses, using the best available data, EPA 

made assumptions relative to toxicity, accumulation, and clearance of the pesticide 

that are material to the exposure and effects modeling in the deterministic secondary 

exposure risk assessment. 

a. Please comment on the reasonableness of the following aspects of EPA’s 

secondary exposure deterministic risk assessment: 

• The use of theoretical body burden calculation together with empirical 

whole body residue data to produce a reasonable range of estimated 

exposures for secondary exposure pathways; 

• The use of the number of prey items required to reach lethal thresholds as 

a means of comparing the relative risks across the assessed rodenticides of 

acute mortality following consumption of contaminated prey; 

• The conclusion that the results of predator / scavenger feeding studies are 

consistent with the findings of the deterministic secondary risk 

assessment;

• The use of a standardized set of avian toxicity endpoints (i.e., species 

tested across all the assessed chemicals) in light of information on 

diphacinone suggesting that raptors may be more sensitive than the 

surrogate avian species used in the risk assessment. 

b. Does the Panel concur with EPA’s analysis and conclusion that consumption of 

living or dead rodents poisoned by brodifacoum or difethialone presents a greater 
Charge Questions

SAP on Rodenticide NOIC – Nov. 29 – Dec. 1, 2011

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opportunity for adverse effects to non-target wildlife compared with the 

rodenticides warfarin, diphacinone, chlorophacinone, or bromethalin? Please 

provide a basis for your conclusions. Does the Panel concur that cancellation of 

products containing brodifacoum and difethialone sold to residential consumers 

will reduce the opportunity for secondary exposure for wildlife to rodenticides? 

Please provide a basis for your conclusions. 

9. Incident data demonstrate that rodenticide use can result in wildlife mortality, and 

that such wildlife mortalities occur in urban and suburban areas. Based on this 

incident data, EPA has concluded that consumer use of rodenticides in urban and 

suburban areas may be a significant contributor to the wildlife mortalities attributable 

to rodenticides. The EPA also determined that both primary and secondary 

poisonings have been documented. 

a. As part of its analysis of incidents, EPA analyzed the available incident data in 

order to associate incidents with specific land use categories, i.e., agricultural, 

urban, suburban areas. In performing this analysis, EPA relied on the information 

in incident reports identifying associated habitat or on the address reported for the 

incident and then used remote sensing information to assign a land use category 

with the incident. Please comment on the reasonableness of this approach to 

using location information to support the conclusion that use of the commensal 

rodenticides addressed in the draft NOIC causes wildlife mortalities in urban and 

suburban areas, as well as rural areas. 

b. EPA analyzed the available incident data in order to differentiate primary and 

secondary wildlife mortality. For this analysis, EPA relied on information on the 

dietary requirements of the moribund species and any identified gut contents 

when available. Does the Panel find this approach a reasonable way to evaluate 

the occurrence of primary and secondary toxicity as causes of wildlife mortality? 

Please provide the basis for your conclusions.

Efficacy of Conforming Rodenticide Products

10. EPA requires registrants of commensal rodent control products to demonstrate that 

their products meet criteria for efficacy. The registrants of conforming rodenticide 

products have submitted such data to EPA, and EPA has determined that their 

products meet these criteria. Do the meeting of these efficacy performance criteria

and EPA’s analysis of the effectiveness of conforming rodenticide products 

reasonably support conclusions that conforming rodenticide products provide 

effective options for chemical control of commensal rodents by nonprofessional 

users? If you conclude that conforming rodenticide products do not provide effective 

options for chemical control of commensal rodents by nonprofessional users, please 

discuss to what extent the following requirements affect the availability to consumers 

of effective options for control of commensal rodents:
Charge Questions

SAP on Rodenticide NOIC – Nov. 29 – Dec. 1, 2011

Page 5 of 5

• The requirement that rodenticides sold to residential consumers must include 

tamper-resistant bait stations;

• The requirement that rodenticides sold to residential consumers must be in 

forms (e.g. bait blocks) which are reasonably expected to remain within the 

bait station; and 

• The requirement that rodenticides sold to residential consumers not contain 

the active ingredients brodifacoum, difethialone, bromadiolone, or 

difenacoum.

Please provide the basis for your conclusions.

11. Are conforming rodenticide products containing the active ingredients warfarin, 

diphacinone, chlorophacinone, or bromethalin, along with non-chemical rodent 

control methods available to consumers and other options, capable of providing 

effective control of commensal rodents? Please provide the basis for your 

conclusions.