ComET™ Farfield ModellingComET™ Farfield Modelling

Dr. Dr. Don MackayDon MackayMr. Jon ArnotMr. Jon Arnot

Canadian Environmental Modelling CentreCanadian Environmental Modelling CentreTrent UniversityTrent University

Peterborough, ONPeterborough, ON

www.trentu.ca/cemcwww.trentu.ca/cemc

Slides and Materials

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Two Sources of Human Two Sources of Human ExposureExposure

Nearfield:Nearfield:– Indoor or direct product useIndoor or direct product use

e.g., cleaning agentse.g., cleaning agents

Farfield (focus of this Farfield (focus of this presentation):presentation):– Environmentally mediatedEnvironmentally mediated

e.g., outdoor inhalation, water e.g., outdoor inhalation, water ingestion, foodstuffs, etc…ingestion, foodstuffs, etc…

Estimates of both are desirableEstimates of both are desirable

Which one dominates?Which one dominates?

Varies from substance to substanceVaries from substance to substance

Depends on how the substance is Depends on how the substance is produced and used and its produced and used and its physical/chemical propertiesphysical/chemical properties

Two Sources of Human Two Sources of Human ExposureExposure

HumanPharmacokineticProcesses

Transformationor DestructionProcesses

Migration intoHuman Exposure

Media of Air, Water & Food

Transport & Transformation in Air, Soil,Sediment, Surface & Groundwater,

Vegetation & Domestic Animals

ENVIRONMENTAL FATE PROCESSESProduction, Importation,Consumption & Disposal

Overview:Overview: Objective – Develop and apply a consistent, Objective – Develop and apply a consistent,

transparent, conservative estimation method transparent, conservative estimation method using only available input datausing only available input data

Method – Combine environmental fate model Method – Combine environmental fate model with food web modelwith food web model

Results:Results:– Estimates of concentration in all relevant Estimates of concentration in all relevant

exposure media (e.g., air, water, soil, food)exposure media (e.g., air, water, soil, food)

Assumption (1): Steady Assumption (1): Steady statestate

Steady state (not dynamic)Steady state (not dynamic)

Time (years)

Con

cent

rati

on

Emission starts, then remains constant

Assumption (2):Assumption (2): Use a single environment for all chemicalsUse a single environment for all chemicals

Based on a typical ChemCAN region and Based on a typical ChemCAN region and the EQC evaluative environmentthe EQC evaluative environment

Area – 10Area – 1055 km km22 (i.e., 316 km (i.e., 316 km 316 km) 316 km)

Includes:Includes:– Air, water, soil, sediment, near shore oceanAir, water, soil, sediment, near shore ocean

Dimensions of Evaluative Dimensions of Evaluative EnvironmentEnvironment

AirAir FreshwatFreshwaterer OceanOcean SoilSoil SedimenSedimen

tt

Area Area (m(m22))

1x101x1011

11 1x101x101010 2.8x102.8x1088 9x109x101010 1x101x101010

Depth Depth (m)(m) 10001000 2020 100100 0.20.2 0.050.05

Volume Volume (m(m33))

1x101x1011

44 2x102x101111 2.8x102.8x1011

00

1.8x101.8x1011

00 5x105x1088

Farfield Model vs. EUSESFarfield Model vs. EUSES

Key Similarities:Key Similarities:– Compartment based Compartment based

mass-balance mass-balance modelsmodels

– Level IIILevel III– Fate and exposure Fate and exposure

pathwayspathways– Generally similar, Generally similar,

diffusive and diffusive and advective inter-advective inter-media transfer media transfer processprocess

Key Differences:Key Differences:– Farfield model includes Farfield model includes

regions in Canada and regions in Canada and can be run in ‘batch can be run in ‘batch mode’mode’

– Farfield model includes Farfield model includes media specific half-livesmedia specific half-lives

– Farfield model includes Farfield model includes mechanistic mechanistic bioaccumulation modelsbioaccumulation models

– Fugacity vs. rate constant Fugacity vs. rate constant formulationformulation

Assumption (3):Assumption (3): Organisms selected as representative speciesOrganisms selected as representative species

– Use current “state of the science” bioaccumulationUse current “state of the science” bioaccumulation– Including reported respiration and feeding ratesIncluding reported respiration and feeding rates

Air

Water

Sediment

Soil

Air

Water

Sediment

Soil

‘‘Representative’ Food WebRepresentative’ Food WebVegetationVegetation

Vegetation – leafyVegetation – leafy GameGame

Vegetation – stemVegetation – stem Terrestrial feeding bird (e.g., Terrestrial feeding bird (e.g., pheasant)pheasant)

Vegetation – rootVegetation – root Aquatic feeding bird (e.g., duck)Aquatic feeding bird (e.g., duck)

Vegetation -- fruit/nut/grainVegetation -- fruit/nut/grain Small herbivorous mammal (e.g., Small herbivorous mammal (e.g., rabbit)rabbit)

Freshwater OrganismsFreshwater Organisms Large herbivorous mammal (e.g., Large herbivorous mammal (e.g., deer)deer)

Aquatic invertebrates (e.g., crayfish)Aquatic invertebrates (e.g., crayfish)

Small fish (e.g., perch)Small fish (e.g., perch) Agricultural ProductsAgricultural Products

Large fish (e.g., lake trout)Large fish (e.g., lake trout) Dairy (e.g., milk & cheese)Dairy (e.g., milk & cheese)

Marine OrganismsMarine Organisms EggsEggs

Marine invertebrates (e.g., lobster, Marine invertebrates (e.g., lobster, shrimp)shrimp) BeefBeef

Small fish (e.g., herring)Small fish (e.g., herring) ChickenChicken

Large fish (e.g., halibut, tuna)Large fish (e.g., halibut, tuna) PorkPork

Marine mammal (e.g., seal)Marine mammal (e.g., seal)

Assumption (4):Assumption (4):

Input data:Input data:– Molecular weight, vapor pressure, water Molecular weight, vapor pressure, water

solubility, octanol-water partition solubility, octanol-water partition coefficient, pKacoefficient, pKa

– Environmental half-lives in air, water, Environmental half-lives in air, water, soil and sedimentsoil and sediment

Unit emission rate:Unit emission rate:– 100 kg/h100 kg/h– 3 modes of entry (air, water and soil)3 modes of entry (air, water and soil)

Assumption (5):Assumption (5):

Metabolic transformation rate constant Metabolic transformation rate constant is initially set to be zero in the is initially set to be zero in the bioaccumulation models for organisms bioaccumulation models for organisms of the food webof the food web– Reasonable assumption about metabolic Reasonable assumption about metabolic

transformation in organisms if no data transformation in organisms if no data availableavailable

– If reliable metabolic transformation rate If reliable metabolic transformation rate data are available they can be incorporateddata are available they can be incorporated

Model OutputModel Output Excel spreadsheet – transparent and Excel spreadsheet – transparent and

available to allavailable to all

Unit emission rate – 100 kg/h to air, water Unit emission rate – 100 kg/h to air, water and soiland soil

Aim is priority setting -- to set aside or Aim is priority setting -- to set aside or prioritize for additional considerationprioritize for additional consideration

Matrix Emission ApproachMatrix Emission Approach 100 kg/h to air:100 kg/h to air:

– CCAIR AIR = 100; C= 100; CWATERWATER = 30; C = 30; CFOODFOOD = 5000 = 5000

100 kg/h to water:100 kg/h to water:– CCAIR AIR = 15; C= 15; CWATERWATER = 150; C = 150; CFOODFOOD = 3000 = 3000

If If actualactual emission is emission is 200200 to air: to air:– CCAIR AIR = 200; C= 200; CWATERWATER = 60; C = 60; CFOODFOOD = 10,000 = 10,000

If If actualactual emission is emission is 200200 to air & to air & 300300 to to water:water:– CCAIR AIR = (200/100) = (200/100) 100 + (300/100) 100 + (300/100) 15 = 245 15 = 245– CCWATER WATER = (200/100) = (200/100) 30 + (300/100) 30 + (300/100) 150 = 510 150 = 510

No need to re-run model, just scale the resultsNo need to re-run model, just scale the results

Emission OptionsEmission Options

Ideally, we will use current reliable and real Ideally, we will use current reliable and real data on emissionsdata on emissions

Alternatively, there are a number of options Alternatively, there are a number of options under consideration which will be the subject under consideration which will be the subject of the next talk on emission estimationof the next talk on emission estimation

To Recap: To Recap: – CEMC will provide data on “unit emissions”CEMC will provide data on “unit emissions”– LLG and HC will estimate and apply emission LLG and HC will estimate and apply emission

estimatesestimates

SummarySummary Physical-chemical properties (CEMC)Physical-chemical properties (CEMC) Unit emissions (CEMC)Unit emissions (CEMC) Calculate all exposure concentrations from unit Calculate all exposure concentrations from unit

emissions (CEMC)emissions (CEMC) Scale to desired emission rate (LLG)Scale to desired emission rate (LLG) Recalculate concentrations (LLG)Recalculate concentrations (LLG) Calculate dosages for selected age classes using Calculate dosages for selected age classes using

exposure quantities (e.g., food intake rates) (LLG)exposure quantities (e.g., food intake rates) (LLG) Combine / compare with near field dosages (LLG)Combine / compare with near field dosages (LLG)