Proposed Decision Framework for 

Assessing Risks of Pesticides to Honey Bees

U.S. Environmental Protection Agency 1

Keith Sappington, M.S.

Environmental Fate and Effects Division

Office of Pesticide Programs
Outline

1. Attributes of Proposed 

Process

2. Process for Foliar Spray

Applications

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Integrate Available Information

Source & Ecosystem Ecological

Exposure at Risk Effects

Problem Formulation

Applications

3. Process for Soil/Seed 

Treatment Applications

4. Comparison with other 

published risk 

assessment schemes

Planning

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Assessment

Endpoints

Analysis

Plan

Conceptual

Model

Analysis
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Attributes of Proposed Decision Framework

 Three risk assessment ‘tiers’ 

• Tier 1 = screening level assessment (conservative, quantitative, 

individual-level effects)

• Tiers 2 and 3 = increasing information needs (greater realism, refined 

estimates of exposure, risk characterized at colony level)

 Relies largely on guideline studies (and recommends several 

in development)

 Focuses on major (and quantifiable) exposure pathways of 

concern

 Separate process for foliar vs. soil/seed treatment 

applications

 Decisions consider multiple lines of evidence and uncertainty
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Application of Proposed Decision Frameworks

 New vs. existing pesticides 

 Iterative nature of assessments 

 Framework flexibility 

 Future modifications
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1. Details of the product and its use pattern

2a. Is exposure of adult bees a concern? 2b. Is exposure of bee brood a concern?

3a. Calculate Tier 1 screening-level 

EEC for adult contact exposure

Contact Exposure

3b. Calculate Tier 1 screening-level EEC for 

adult oral exposure via pollen and nectar

Oral Exposure

3c. Calculate Tier 1 screening-level EEC 

for larval oral exposure via brood food

Oral Exposure

4a. Calculate Tier 1 screening-level 

RQs for adult contact exposure (RQ 

= EEC/adult acute contact LD50) 

4b. Calculate Tier 1 screening-level 

RQs for adult oral exposure 

(RQ = EEC/adult acute oral LD50 & 

RQ = EEC/adult chronic NOAEC)* 

4c. Calculate Tier 1 screening-level RQs 

for larval oral exposure

(RQ = EEC/larval acute LD50 & 

RQ= EEC/larval chronic NOAEC)* 

No Tier 1 brood 

assessment

6. Refine Tier 1 Exposure Assessment (e.g., using 

available crop residue studies), Recalculate RQs.

Presumption 

of minimal risk

Presumption 

of minimal risk

Risk Assessment 5 a,b,c. Does any RQ exceed LOC? 

Scheme for Foliar 

Spray Application

Tier 1

Y

N

8. Consider Risk Mitigation Options, 

Uncertainties, Other lines of Evidence; Is 

a higher tier assessment needed?

9a. Conduct Tier 2 

Exposure Studies (e..g, 

residues in pollen, nectar)

9b. Conduct Tier 2 ColonyLevel Effect Studies (e..g, 

semi-field, feeding)

10. Evaluate Tier 2 exposure and colony-level 

effect results. Consider uncertainties and other 

lines of evidence. Do results indicate risk?

11. Consider Risk Mitigation Options, 

Uncertainties, Other Lines of Evidence; Is a 

higher Tier assessment needed?

12. Conduct Tier 3 

Field Studies to 

address uncertainties

13. Evaluate Tier 3 field study results. Consider 

risk mitigation options, uncertainties and other 

lines of evidence. Do results indicate risk?

7 a,b,c. Does any RQ exceed LOC? 

Presumption 

of minimal risk

* When tests are sufficiently developed and vetted Presumption of risk Optional

Tier 2

Tier 3
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2a. Is exposure of adult bees a concern? * 2b. Is exposure of bee brood a concern? *

1. Details of the product and its use pattern

5 a,b. Does any RQ exceed LOC? 

6. Refine Tier 1 Exposure Assessment (e.g., using 

available crop residue studies), Recalculate RQs.

Presumption of 

minimal risk*

3a. Calculate Tier 1 screening-level EEC for 

adult oral exposure via pollen and nectar

Oral Exposure

3b. Calculate Tier 1 screening-level EEC for 

larval oral exposure via processed brood food

Oral Exposure

4a. Calculate Tier 1 screening-level RQs for adult 

oral exposure

(RQ = EEC/adult acute oral LD50 &

RQ =EEC/chronic adult NOAEC)**

4b. Calculate Tier 1 screening-level RQs for 

larval oral exposure

(RQ = EEC/larval acute LD50&

RQ= EEC/chronic larval NOAEC)** 

No Tier 1 brood 

assessment

Presumption of 

minimal risk

Risk Assessment 

Scheme for Soil/ 

Seed Treatment 

Application

Y

N

Optional

*Mitigation of risks from abraded seed coatings is 

addressed outside of this process 

** When tests are sufficiently developed

8. Consider Risk Mitigation Options, Other 

Lines of Evidence and Uncertainties; Is a 

higher tier assessment needed?

10. Evaluate Tier 2 exposure and colony-level 

effect results. Consider uncertainties and other 

lines of evidence. Do results indicate risk?

9a. Conduct Tier 2 

Exposure Studies (e..g, 

residues in pollen, nectar)

9b. Conduct Tier 2 ColonyLevel Effect Studies (e..g, 

semi-field, feeding)

11. Consider Risk Mitigation Options, Other Lines of 

Evidence and Uncertainties; Is a higher tier 

assessment needed?

Presumption of 

minimal risk

13. Evaluate Tier 3 field study results. Consider risk 

mitigation options, uncertainties and other lines of 

evidence. Do results indicate risk?

12. Conduct Tier 3 

Field Studies to 

address uncertainties

7 a,b,c. Does any RQ exceed LOC? 

Presumption of risk
Comparison to Other Risk Assessment 

Schemes

• European Food Safety Authority (EFSA 2012) 

• Society of Environmental Toxicology and Chemistry “Pellston” Workshop 

(Fischer and Moriarty 2011) 

• Some Similarities: 

• All involved tiered processes (effects at the individual level, then at the colony level)

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• All involved tiered processes (effects at the individual level, then at the colony level)

• Different schemes depending on application method (foliar spray, soil, seed 

treatment)

• Contact and oral are dominant routes of exposure

• All recognize need for acute and chronic effects to be assessed initially

• Some Differences: 

• Decision “triggers” take various forms (when specified)

• Non-Apis bees are included in EFSA (2012) and Fischer and Moriarty (2011), although 

full implementation will require additional research and test development. 

• Risk conclusions at higher tiers consider multiple lines of evidence, (White Paper); 

other schemes rely on outcome of semi field or field studies