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Environmental Risk Assessment

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On this page:

Janice Villeneuve
Senior Evaluation Officer, Re-evaluation Section 1
Environmental Assessment Directorate

Overview

  • Purpose of Environmental Risk Assessment
  • Data Requirements
  • Low-Risk
  • Risk Assessment Framework
    • Exposure Assessment
    • Hazard Assessment
    • Risk Characterization
  • Risk Mitigation Measures
  • Drinking Water Estimates
  • Toxic Substances Management Policy
  • Common Deficiencies
  • Environmental Case Study

Purpose of Environmental Risk Assessment

  • Evaluate the likelihood that adverse environmental effects may occur or are occurring as a result of exposure to the pesticide (active ingredients and transformation products)
  • Determine whether changes to the use or proposed use of that pesticide are necessary to protect the environment

Data Requirements

  • USC DACO Tables
    • Total of 33 different USCs
    • "CR" - conditional on the potential for exposure
  • Most agricultural pesticides require the studies listed under Use-site Category 14 (USC14)
  • For some USCs, the data requirements are reduced because the potential for exposure is reduced

Low-Risk

  • Risk assessment methods are the same
  • Data requirements may be reduced based on toxicity and exposure information

Risk Assessment Framework

Risk Assessment Framework

Environmental Exposure Assessment

  • Estimates the potential exposure of plants and animals to pesticide residues in water, food, soil and air.
  • Includes information on how often, how long and the amount of pesticide to which an organism may be exposed.
  • Based on environmental fate and transport data as well as modeling and field monitoring information.

Studies to Estimate Exposure

  • Physicochemical properties
    • Solubility, vapour pressure, Kow, pKa, UV-absorption
  • Transformation (Abiotic and Biotic)
    • Hydrolysis, phototransformation, aerobic/anaerobic biotransformation (terrestrial and aquatic)
  • Mobility
    • Leaching, volatilization
  • Field dissipation (DIR2006-01)
    • Fate and mobility in sites representative of use areas in Canada
  • Guideline for Determining Environmental Chemistry and Fate (T-1-225)
  • Harmonization of Environmental Chemistry and Fate Data (DIR2003-03)

Environmental Hazard Assessment

  • Describes the types of effects a pesticide can produce in organisms and how those effects change with varying pesticide exposure levels
  • Based on accepted protocols with surrogate test species
  • Determines effects endpoints and dose response (e.g. LD50, NOEC, EC25)
  • Identify sensitive organisms and predicts adverse effect(s) on non-target organisms.

Terrestrial Species Typically Studied

  • Earthworm
  • Honeybee
  • Beneficial Insects
    • parasitic wasp, predatory mite, ladybird beetle, lacewing, minute pirate bug, ground beetle
  • Birds (Acute and Reproduction)
    • mallard duck
    • bobwhite quail
  • Mammals (Acute and Reproduction)
    • rats, mice (reviewed by HED)
  • Terrestrial vascular plants

Aquatic Species Typically Studied - Freshwater

  • Invertebrates (acute and reproduction)
    • Daphnia magna
  • Fish (acute, early-life stage, life-cycle)
    • rainbow trout
    • bluegill sunfish
  • Algae (acute): 3 species
    • Selenastrum capricornutum
    • Anabaena sp.
    • diatom
  • Vascular plant
    • Lemna gibba

Aquatic Species Typically Studied - Estuarine/Marine

  • Crustacean (Acute and chronic)
    • mysid
  • Mollusk embryo larvae OR shell deposition
  • Fish (acute and chronic)
    • sheepshead minnow
  • Algae (acute)

Risk Characterization

  • Compare the levels of exposure (estimated environmental concentrations -EEC) expected in the environment according to the proposed or actual use pattern to those levels that produce toxic effects in laboratory and field studies
  • When EEC exceeds levels expected to cause effects (level of concern -LOC), measures to mitigate the risk are examined

Risk Characterization - Screening vs. Refined

  • Screening Level Risk Assessment
    • Goal to identify:
      • Pesticides that do not pose a concern
      • Group(s) of organisms that would not be at risk
      • Pesticides that have a potential for concern, and risk needs further characterization
    • Based on conservative scenarios, simple methods
  • Refined Risk Assessment
    • Goal: further characterize the risk using more refined scenarios
    • Tiers of refinement to adequately characterize risk

Risk Characterization

  • Deterministic Method
    • Risk Quotient (RQ) = Exposure/Toxicity
    • RQ ≤ 1: Negligible Concern
    • RQ > 1: Potential for Concern
  • Probabilistic Methods
    • Refined risk assessment
    • Only if sufficient data are available
    • Re-evaluation

Risk Characterization - Terrestrial (Effects Endpoints used)

  • Earthworms
    • LC50 × 0.5 or NOEC
  • Beneficial Insects
    • LR50
  • Birds/Mammals
    • Acute oral LD50x 0.1 OR NOEL
    • Dietary LC50x 0.1 OR NOEC
    • Reproduction NOEC
  • Vascular Plants
    • EC25for most sensitive plant species (seedling emergence or vegetative vigour)

Estimated Environmental Concentrations (EECs) - Terrestrial

  • Screening Level
    • Soil: g a.i./kg soil
    • Application rate: g a.i./ha (beneficial insects/plants)
    • Food Sources: g a.i./kg diet
      • Dosages consumed in contaminated food items estimated using Hoerger and Kenaga (1972) nomogram and modification by Fletcher et al (1994)
    • Inhalation: concentration in air
      • Modelling data - estimated air concentrations
      • Monitoring data - measured air concentrations

Risk Characterization - Terrestrial Screening Level

  • Integrate Exposure and Effect to identify risk using RQ method for all terrestrial organism groups
  • Risk Quotient (RQ) = Exposure/Toxicity
    • RQ ≤ 1: Negligible Concern
    • RQ > 1: Potential for Concern (proceed to refined risk assessment)

Risk Characterization - Terrestrial Options for Refinement

  • More realistic exposure scenario
    • Use pattern
    • Fate/persistence information
  • Consideration of off-target effects from spray drift
  • Specific scenarios
    • Crop-specific scenarios, relevant species, species-specific diets, behaviour of species
  • Additional options for Registered Products/Re-evaluation
    • Additional effects endpoints
    • Data from research and monitoring
    • Incident Reports
    • Probabilistic risk assessments

Risk Characterization - Aquatic Endpoints Used Effects

  • Aquatic plants/Pelagic invertebrates/Benthic invertebrates
    • Acute: EC50 × 0.5
    • Chronic: NOEC
  • Fish
    • Acute: LC50 × 0.1
    • Chronic: NOEC
  • Amphibians (aquatic stages) - use fish endpoints when no amphibian data are available
    • Acute: LC50 × 0.1
    • Chronic: NOEC

Risk Characterization - Aquatic EECs

  • Screening Level Assessment
    • Water: g a.i./L (15 cm forestry uses, 15 cm seasonal water body, 80 cm permanent water body)
      • Conservative assumptions: maximum seasonal rate, shortest application interval, adjust for transformation for multiple applications, direct application
  • Refined Assessment
    • Run off: PRZM/EXAMS
      • Appropriate scenarios are run based on the use pattern identified
    • Drift: EECs resulting from spray drift using the maximum drift deposition for application method

Maximum Drift Deposition Table

Maximum Spray Drift Deposition % Drift at 1 m downwind
Mode of Application Spray Quality (ASAE) Drift (% of applied)
Ground Boom Sprayer Coarse 3%
Ground Boom Sprayer Medium 6%
Ground Boom Sprayer Fine 11%
Airblast - Early Season Fine 74%
Airblast - Late Season Fine 59%
Aerial - Agricultural Crops Coarse 17%
Aerial - Agricultural Crops Medium 23%
Aerial - Agricultural Crops Fine 26%
Aerial - Non-Crops Coarse 60%
Aerial - Non-Crops Medium 60%
Aerial - Non-Crops Fine 44%
Aerial - Forestry Coarse 77%
Aerial - Forestry Medium 85%
Aerial - Forestry Fine 90%

Note: RQs should be calculated for all uses on the label in order to characterize the risk..
For field and aerial applications use a Fine and Medium droplet sizes for insecticides and herbicides,
respectively, unless otherwise stated on the label

Risk Characterization - Aquatic Screening Level

  • Screening level assessment
    • RQ ≤ 1 - no further refinement required
    • RQ > 1 - potential concern, proceed to refined assessment

Risk Characterization - Aquatic Refined

  • Refined risk assessment
    • Drift
      • If RQ = 1 - default buffer zone of 1 m will be assigned
      • If RQ > 1 - appropriate buffer zones will be determined
        • Aerial - AgDISP v.8.15 (2005)
        • Ground - Wolf and Caldwell (2001)
        • Ground - Airblast - Ganzelmeier et al (1995)
    • Run off
      • EECs predicted by PRZM-EXAMS
        • If RQ = 1 - no risk identified for run off
        • If RQ > 1 - potential risk identified for run off; consider further refinements - identify risk mitigation measures

Risk Characterization - Aquatic Additional Options for Refinement

  • Further refinement to modelling inputs to represent more realistic scenarios
  • Other options where sufficient data is available - registered products/re-evaluation
    • Additional toxicity endpoints - species sensitivity distributions
    • Monitoring data/incident reports
    • Probabilistic risk assessment

Risk Mitigation Measures -Examples

  • Reduce number of applications per season
  • Buffer zones to reduce drift to non-target species/sensitive areas
  • Restrict against applications in consecutive years
  • Restrict to ground application (no aerial use)
  • Use decreased application rates (determined in conjunction with efficacy review)
  • Change application conditions (time of day)
  • Choose certain formulation types
  • Require immediate incorporation in soil
  • Restriction of certain uses or entire active ingredient
  • Label advisory statements

Some Areas Requiring Further Development

  • Improved RA methods for birds, mammals and terrestrial plants - currently investigating
  • Probabilistic risk assessment - has been used for re-evaluation

Drinking Water Estimates for Human Health Assessment

  • Drinking water estimates for use in the human health assessment are determined by EAD
    • PRZM/EXAMS -EEC in drinking water from surface run off
    • LEACHM -EEC in drinking water from groundwater sources
    • When sufficient water monitoring data are available, these data are considered in the estimate of drinking water exposure
  • SPN2004-01 (Estimating the Water Component of a Dietary Exposure Assessment)

Toxic Substances Management Policy (DIR99-03)

  • Assesses if active ingredient, transformation product or any other substance within a product are classified as Track 1
    • Track 1
      • CEPA-toxic or equivalent, predominantly anthropogenic, persistent and bioaccumulative
      • Virtual elimination
    • Track 2
      • Does not meet all of the criteria for Track 1
      • Full life-cycle management

Environmental Risk Assessment - Case Study

Spiromesifen

Major transformation product: BSN 2060-enol

Physicochemical Properties
Property Value Interpretation
Water solubility 0.13 mg/L Sparingly soluble
Vapour pressure 1 × 10−6 Pa Not volatile
Henry's law constant 1.9 x 10-7 atm m3/mol Not likely to volatilize from water or moist soil
n-Octanol-water coefficient 4.55 Potential for bioaccumulation
Dissociation constant No pKa between pH 4 and 9 Unlikely to be mobile at ambient pH
UV-vis adsorption λ max = 214 nm Phototransformation in the environment unlikely

Abiotic Transformation: Parent

  • Hydrolysis
    • Half-life: pH 4 = 48 d; pH 7 = 26 d; pH 9 = 4.5 d
      • Not an important route of transformation at pH 4 and 7, but importance increases under basic conditions
  • Soil phototransformation
    • Half-life: 47.2 d
      • Not an important route of transformation
  • Water phototransformation
    • Half-life: 3.6 h
      • An important route of transformation

Biotransformation: Parent

  • Soil: half-life: 2.8-18 d
    • Non-persistent to moderately persistent, depending on soil characteristics
  • Water:
    • Aerobic half-life: 4.1-8 d
      • Non-persistent to slightly persistent
    • Anaerobic half-life: 18 d
      • Slightly persistent
  • Bioaccumulation: BCF 875 - 916
    • Bioaccumulates but readily depurated - bioaccumulation is not a concern

Field Dissipation - Parent

  • Terrestrial field dissipation
    • DT50= 4.5 d
    • Parent is non-persistent under field conditions

Data submitted for transformation product: BSN 2060-enol

  • Water phototransformation
    • Half-life: 16.5 d
      • Not an important route of transformation
  • Adsorption/desorption
    • Kd = 0.0185-0.049 mL/g
      • Very highly mobile
  • Field dissipation
    • DT50= 18 d
      • Slightly persistent

Overall Conclusion - Persistence

  • Parent
    • Terrestrial - non-persistent
    • Aquatic - non-persistent to slightly persistent
  • Transformation product
    • Terrestrial - slightly persistent
    • Aquatic - slightly to moderately persistent

Mobility - Parent

  • Adsorption-desorption - parent was not stable in CaCl2; therefore, study could not be conducted
  • Soil leaching - unaged soil
    • Parent remained in top soil layer -not mobile
  • Soil TLC - Rf = 0.0021 - parent is immobile
  • Overall conclusions considering log K, pKa, and
    mobility studies - parent is not mobile in soil; transformation product is very highly mobile
Screening Level Risk Assessment - Terrestrial Invertebrates
Organisms Study Substance RQ > LOC
Carabid beetle Contact EUP 1.11 Yes
Ladybird Contact EUP 17.5 Yes
Predaceous mite Contact EUP 11.3 Yes
Aphid Contact EUP 74.7 Yes

LOC was not exceeded for earthworm, honeybee, rove beetle, green lacewing

Refined Risk Assessment - Terrestrial Invertebrates
Organisms Refined RQ (10 d foliar t½) > LOC Mitigation
Carabid 0.84 No  
Ladybird 13.3 Yes Label advisory statement
Predaceous mite 8.6 Yes Label advisory statement
Aphid 56.6 Yes Label advisory statement
Screening Risk Assessment - Terrestrial Vertebrates
Organisms Study Substance RQ > LOC
Bird Acute Oral Parent 0.017 No
Bird Dietary Parent 0.03 No
Bird Repro Parent 1.7 Yes
Small Mammal Acute Oral Parent 0.46 No
Small Mammal Dietary 28 d Parent 3.7 Yes
Small Mammal Dietary 90 d Parent 3.7 Yes
Small Mammal Repro Parent 3.1 Yes
Refined Risk Assessment - Terrestrial Vertebrates
Organisms Refined RQ (10 d half-life on plants) > LOC Mitigation
Birds - repro 1.29 Yes The persistence of spiromesifen is low in the environment; therefore, it is unlikely that birds or mammals will be exposed chronically.
Mammals - dietary 2.8 Yes The persistence of spiromesifen is low in the environment; therefore, it is unlikely that birds or mammals will be exposed chronically.
Mammals - repro 2.3 Yes The persistence of spiromesifen is low in the environment; therefore, it is unlikely that birds or mammals will be exposed chronically.
Screening Risk Assessment - Terrestrial Plants
Organism Study Substance RQ > LOC Mitigation
Vascular plants Seedling Emergence and Vegetative Vigour EUP 30.9 Yes Buffer zones for terrestrial habitats
Vascular plants Seedling Emergence and Vegetative Vigour EUP 14.6 Yes Buffer zones for terrestrial habitats
Vascular plants Seedling Emergence and Vegetative Vigour EUP 14.6 Yes Buffer zones for terrestrial habitats
Screening Level Risk Assessment - Aquatic Invertebrates
Organism Exposure Substance RQ > LOC
FW Invert Acute Parent 1.8 Yes
FW Invert Acute EUP 0.009 No
FW Invert Acute enol TP 0.002 No
FW Invert Chronic Parent 324 Yes
FW Invert Chronic EUP 47.6 Yes
FW Invert Chronic enol TP 0.435 No
FW Invert Chronic pop'n study EUP 144.6 Yes
Refined Risk Assessment - Aquatic Invertebrates
Organism Substance Drift/Run off RQ > LOC Mitigation
FW Invert Parent Drift 0.19 No Buffer zones considered
FW Invert Parent Run off 0.011 No Buffer zones considered
FW Invert EUP Drift 5.24 Yes Buffer zones considered
FW Invert EUP Drift 15.9 Yes Buffer zones considered
E-M Invert Parent Drift 0.23 No Not required
E-M Invert Parent Run off 0.49 No Not required
Screening Level Assessment - Aquatic Fish/Amphibians
Organisms Exposure Substance RQ > LOC
FW Fish Acute Parent 48.2 Yes
FW Fish Acute EUP 11.1 Yes
FW Fish Acute TP 0.008 No
FW Fish Chronic Parent 54 Yes
EM Fish Acute Parent 17.5 Yes
Amphibians (based on fish endpoint; 15 cm water body) Acute Parent 256 Yes
Amphibians (based on fish endpoint; 15 cm water body) Acute TP 0.04 No
Amphibians (based on fish endpoint; 15 cm water body) Chronic Parent 287 Yes
Refined Risk Assessment - Aquatic Fish/Amphibians
Organisms Exposure Drift/Run off RQ >LOC Mitigation
FW Fish Acute Drift 5.3 Yes Buffer zone considered
FW Fish Chronic Drift 5.9 Yes Chronic exposure not expected due to chemical properties
FW Fish Acute Run off 0.3 No Not required
FW Fish Chronic Run off 0.02 No Not required
EM Fish Acute Drift 1.9 Yes Buffer zone considered
EM Fish Chronic Run off 0.1 No Not required
Amphibians Acute Drift 28.2 Yes Buffer zone considered
Amphibians Chronic Drift 31.5 Yes Chronic exposure not expected due to chemical properties
Amphibians Acute Run off 0.3 No Not required
Amphibians Chronic Run off 0.06 No Not required
Screening Level Risk Assessment - Aquatic Plants
Organisms Exposure Substance RQ > LOC
FW algae Acute Parent 3.6 Yes
FW algae Acute TP 10.9 Yes
Vascular plants Acute Parent 1.6 Yes
Refined Risk Assessment - Aquatic Plants
Organisms Substance Drift/Run off RQ > LOC Mitigation
FW algae Parent Drift 0.4 No Not required
FW algae TP Drift 1.2 Yes Buffer zone considered
FW algae Parent Run off 0.02 No Not required
FW algae TP Run off 221 Yes Label advisory statement
Vascular plants Parent Drift 0.18 No Not required
Vascular plants Parent Run off 0.01 No Not required

Overall Environmental Mitigation Measures

  • Buffer Zones
    • Ground
      • 2 to 10 m for freshwater habitats
      • 1 m for marine habitats
      • 1 to 2 m for terrestrial habitats
    • Aerial
      • 25 to 350 m for freshwater habitats
      • 1 to 10 m for marine habitats
      • 40 to 45 m for terrestrial habitats
  • Toxicity and run off advisory statements

Common Deficiencies/Problems

  • Studies often not submitted
    • DACO 8.2.3.4.4 - anaerobic soil (only required for USC 14)
    • Oral bee study
    • General information on TPs (Kow, solubility, etc.)
  • Problems with studies
    • Fate studies
      • Major transformation products not identified
      • Studies cut too short - does not allow for determination of TP half-lives
      • Improper sampling periods
      • Inappropriate extraction and analytical methods
      • Desorption not performed using 3 consecutive desorption cycles (as perT-1-255)
    • Toxicity studies (aquatic)
      • Studies conducted above solubility of compound
  • Link in submitted studies/templates to raw data in Excel format

Reference Documents

  • USC DACO Tables
  • PRO2007-02
  • T-1-255
  • DIR2006-01
  • DIR2003-03
  • Pesticide Incident Reporting
  • PRO2005-06
  • SPN2004-01
  • DIR99-03
Date Modified: 2009-01-13

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