Link To Webinar Recording:

Preliminary Imidacloprid Pollinator Risk Assessment 

Technical Briefing Webinar Recording

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Public Webinar on Imidacloprid 

Preliminary Pollinator Assessment

Office of Pesticide Programs / Environmental Protection Agency

February 18th, 2016

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• Process

• Assessment details and findings

• Next steps

• Q & A session

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Presentation Outline 
• Imidacloprid is one of the neonicotinoid insecticides 

currently undergoing Registration Review

• This assessment (released January 2016):

Follows Problem Formulation and Preliminary Work Plan (2008) 

and Data Call-In (2010)

Fulfills an EPA commitment to Presidential Pollinator Strategy

• Pollinator Health Task Force (May 2015)

Is located in the public docket available at: 

http://www.regulations.gov/#!docketDetail;D=EPA-HQ-OPP2008-0844

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Process 
Typical Registration Review Process

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Public Comment Opportunities

Open

Docket

Preliminary 

Risk

Assessment

Revised Risk 

Assessment

And Proposed

Decision

Final

Decision
Imidacloprid Registration Review Process

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Public Comment Opportunities

Open

Docket

Preliminary 

Pollinatoronly Risk

Assessment

Preliminary 

Ecological 

and Human 

Health Risk 

Assessment

Final

Decision

Proposed 

Decision
Risk Management

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Regulatory 

Decision

Risk Assessment and Benefits Analysis

Characterization

Risk Management Options

Legal Standards Public Input
• Nitroguanidine-substituted neonicotinoid insecticide

• Mobile

Highly soluble

High tendency to runoff 

• Systemic 

• Mode of action:

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Background

Receptor

Imidacloprid

Overstimulation / 

blockage of 

receptor

Paralysis / death
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Multiple Factors Affecting Honey Bee Health 

Urbanization

Agricultural Practices

Pesticides

Bee Management Practices Nutrition

Honey bee losses: Research has identified multiple factors; no single factor identified as 

“cause”.

Disease/Parasites
Scope of Assessment

• Follows bee risk assessment framework published in 2014

Developed by the Environmental Protection Agency (EPA), 

California Department of Pesticide Regulation (CDPR), and 

Canada’s Pest Management Regulatory Agency (PMRA)

Received independent, peer review in 2012

For this assessment:

• Honey bee (Apis) focus

• Agricultural uses only

Follow-on assessment planned for December 2016:

• All other wildlife

• Non-agricultural uses

• Additional residue data

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• Methods of application:

Direct sprays on crop

Soil

Seed treatment

• Registered uses on variety of crops (including but not 

limited to):

Vegetables (tomatoes, legumes, broccoli, lettuce)

Fruits (apples, citrus, berries)

Cereal grains (corn, wheat, sorghum)

Tree nuts (walnuts, pecans)

Other (cotton)

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Agricultural Uses of Imidacloprid
Exposure Routes 

Exposure routes assessed:

• Contact exposure (direct spray applications only)

Adults only

• Oral exposure by ingestion of contaminated pollen and 

nectar (direct spray/soil/seed applications)

Adults

Larvae

Other routes being considered:

• Guttation/surface water

• Abraded dust from seed treatments

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Risk Assessment Process

Determination of 

Potential Exposure

Tier I

• Screening-level

• Refined

Tier II (Semi-field)

• Tunnel

• Feeding

Tier III (Full-field)
Toxicity Data

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• Considers registrant-submitted AND open literature 

sources

• Focus on survival, growth/development, and 

reproduction)

• Registrant submitted:

Contract laboratory-conducted

GLP, Office of Chemical Safety and Pollution Prevention 

(OCSPP) guidance-compliant

Results and statistical analysis verified by EPA

• Open literature studies:

Evaluation of strengths and limitations 

Supplanted registrant-submitted endpoints in some 

cases

• 100+ studies evaluated
Individual Level Toxicity (Tier I)

• Conducted in lab

• Vary in exposure route, life stage tested, and 

duration

• Data indicate

Adults more sensitive 

than larvae

Oral route more 

sensitive than direct 

contact

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Colony Level Toxicity (Tier II)

• Conducted in field

• Limited dataset in the open literature for evaluating colony level effects to 

Apis

• Consultation with researchers and 

registrant to design a novel chronic colony 

feeding study (CFS)

Registrant-submitted CFS:

• Robust:

 High replication (n=12-24 colonies/trt)

 12.5, 25, 50, 100, and 200 ppb

 Overwintering period

 Pathogen and parasite monitoring

• Spiked sucrose (nectar) for 6 weeks

 Freely foraged for pollen

 Exposure period consistent with bloom duration of some crops (e.g. citrus fruits)

• No Observed Adverse Effect Concentration (NOAEC) = 25 ppb; Lowest Observed Adverse 

Effect Concentration (LOAEC) = 50 ppb in nectar 

 ↓ in-hive pollen provisions, #s of pupae and adults
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CFS Results

12.5 ppb

25 ppb

50 ppb

100 ppb

200 ppb

↓ Adults, ↓ Eggs, ↓ Larvae, ↓ Pupae, 

↓ Pollen, ↓ Honey

> 80% colony mortality post-overwintering

Response variables trended with control

**Further information can be found 

in Section 5.2.1 of the assessment
Risk Characterization

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Considers Multiple Lines of Evidence:

• Determination of exposure

• Individual Level (Tier I) Risk Quotients (screening 

level, refined exposure)

• Colony Level (Tier II) Assessment (nectar)

• Colony Level (Tier III) Assessment

• Incidents

• Hive residue monitoring

• Non-Apis bees 
Risk Characterization

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• Determining Exposure:

 Crop attractiveness

 Agronomic practices
• Individual Level (Tier I) 

 Screening-Level

 “High end,” model-generated exposure estimates

 Individual organism toxicity endpoints 

 Risk estimated for various life stages and durations of exposure

 Refined 

 Nectar/pollen data used for exposure 

 Individual organism toxicity endpoints 

 Risk estimated for various life stages and durations of exposure

 Determination of duration of risk concerns

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Risk Characterization

When residue data are 

available
• Colony Level (Tier II) (nectar)

 Comparison of residues to colony level endpoint (25 ppb)

 Nature of residues over time

 Influence of soil type

 Consideration of bloom duration

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Risk Characterization
• Colony Level (Tier III)

 Available dataset not useful for effects characterization

 Ongoing studies with cotton and pumpkin

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Risk Characterization 
• Reported Incidents

Limited (6) reports for agricultural uses linked to imidacloprid 

exposure 

Lack of reported incidents does not indicate lack of losses in the 

field

• Agricultural Monitoring Studies (seed treatment) 

High frequency of detection, low mean residues in pollen (2 – 3 

ppb) 

• Hive Monitoring Studies (nectar, pollen, wax, bees):

Generally low frequency of detects

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Risk Characterization 
Risk Characterization - Non-Apis 

• > 4,000 species of non-Apis bees in U.S. 

• Differences in biology, ecology expected to lead to different 

exposures vs. Apis

• Relevant to pollinator protection goals (commercial pollination 

services, biodiversity)

Osmia lignaria – Blue orchard bee

Megachile rotundata –

Alfalfa leafcutter bee

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Risk Characterization - Non-Apis

• Tier I risk assessment methods and data currently lacking

 Limited data suggest honey bee is protective of bumble bees 

and solitary species

• Open literature data suggest bumble bees may be 

sensitive at the colony level

 Additional data would reduce this uncertainty

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Honey Bee Risk Determinations –

Foliar Applications

- Root/Tuber Vegetables

- Leafy Green Vegetables

- Brassica Vegetables

- Fruiting Vegetables

- Tobacco

- Globe artichoke

- Legumes

- Pome Fruits

- Stone Fruits

- Berries/Small Fruits

- Tree Nuts

- Herbs/Spices

- Citrus Fruits

- Cotton

Low Uncertain Risk 26
Honey Bee Risk Determinations –

Soil Applications

- Root/Tuber Vegetables

- Bulb Vegetables

- Leafy Green Vegetables

- Brassica Vegetables

- Fruiting Vegetables

- Berries/Small Fruits

- Tobacco

- Globe artichoke - Legumes

- Cucurbit Vegetables

- Citrus Fruits

- Pome Fruits

- Stone Fruits

- Berries/Small Fruits

- Tree Nuts

- Herbs/Spices

- Cotton

Low Uncertain Risk 27
Honey Bee Risk Determinations –

Seed Applications

- Root/Tuber Vegetables

- Bulb Vegetables

- Brassica Vegetables

- Cereal Grains (corn)

- Legumes

- Cereal Grains (nectar 

producers)

- Herbs/Spices

- Oilseed

Low Uncertain Risk 28
Major Assumptions/Uncertainties in Risk 

Assessment

• Colony (Tier II) level (Exposure):

 Risk determinations assumes bees feed continuously on 

treated crop for 6 weeks

 Representativeness of 6 week exposure per CFS

 Long blooming crops (cotton, citrus, strawberry) vs. short blooming 

crops (cherry, blueberry)

Migratory pollination services

• Limited full field colony level (Tier III) data:

 Ongoing studies for cotton and pumpkin 

• Forthcoming residue data:

Reduce uncertainty for several uses

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• Public comment period for 60 days (ends March 15, 2016)

• Follow-on assessment:

Review public comments

Incorporation of additional bee data

Inclusion of non-agricultural uses

Assessment of other taxa (e.g., fish, aquatic invertebrates, plants, 

birds, mammals)

• December 2016 – publish follow-on assessment

Preliminary pollinator assessments for clothianidin, thiamethoxam, 

and dinotefuran

• Consider appropriate risk management strategies:

Risk management discussions with stakeholders 

Risk management options:

 Consideration of risks and benefits

 Likely alternatives

 Potential impact on agricultural production and users

Next Steps
1. USDA. 2015. Attractiveness of Agricultural Crops to pollinating Bees for the 

Collection of Nectar and/or Pollen. United States Department of Agriculture. 

http://www.ree.usda.gov/ree/news/Attractiveness_of_Agriculture_crops_to_

pollinating_bees_Report-FINAL.pdf

2. USEPA. 2012. White Paper in Support of the Proposed Risk Assessment 

Process for Bees. Submitted to the FIFRA Scientific Advisory Panel for Review 

and Comment September 11 – 14, 2012. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2012-0543- 0004

3. USEPA/PMRA/CDPR. 2014. Guidance for Assessing Pesticide Risks to Bees. 

Office of Pesticide Programs, United States Environmental Protection Agency, 

Washington, D.C.; Health Canada Pest Management Regulatory Agency 

Ottawa, ON, Canada California Department of Pesticide Regulation, 

Sacramento, CA. http://www2.epa.gov/pollinator-protection/pollinator-risk- assessment-guidance

4. USEPA. 2016. Preliminary Pollinator Assessment to Support the Registration 

Review of Imidacloprid. Office of Chemical Safety and Pollution Prevention. 

United States Environmental Protection Agency. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2008-0844- 0140

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References
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Q & A Session