POPs Risk Assessment. RISK ASSESSMENT Module 2 – Risk Assessment Overview of the course This module introduces POPs Risk Assessment, including Quantitative

POPs RiskPOPs Risk

AssessmentAssessment

RISK ASSESSMENTRISK ASSESSMENTModule 2 – Risk AssessmentModule 2 – Risk Assessment

Overview of the course Overview of the course This module introduces POPs Risk Assessment, including Quantitative Risk Assessment and tiered methodologies.This module introduces POPs Risk Assessment, including Quantitative Risk Assessment and tiered methodologies.

ContentsContentsRisk Assessment (RA)Risk Assessment (RA)Quantitative Risk Assessment (QRA)Quantitative Risk Assessment (QRA)

Conceptual Site Model (CSM)Conceptual Site Model (CSM)Tier 1Tier 1Tiers 2 & 3Tiers 2 & 3

Exposure AssessmentExposure AssessmentToxicity AssessmentToxicity Assessment

Risk CharacterisationRisk Characterisation

Learning outcomesLearning outcomesUnderstand how risk assessment methodologies can be applied to POPs.Understand how risk assessment methodologies can be applied to POPs.Appreciate how a tiered system can be used to understand risk to a population.Appreciate how a tiered system can be used to understand risk to a population.

Pre-requisitesPre-requisitesIntroduction to POPs – Chapter 1 of the manual or e-learning Module 1Introduction to POPs – Chapter 1 of the manual or e-learning Module 1

Follow-on CourseFollow-on CourseRehabilitation and RemediationRehabilitation and Remediation

Download the course as a pdfDownload the course as a pdf

Related information Related information Chapter 5 of the ManualChapter 5 of the Manual

Approximate time for this moduleApproximate time for this module 45 mins – 1 hour45 mins – 1 hour

RISK ASSESSMENTRISK ASSESSMENT

IntroductionIntroductionAs you learnt in module 1, the As you learnt in module 1, the principle exposure routes are:principle exposure routes are:

bio-accumulationbio-accumulation inhalation of dust or vapour inhalation of dust or vapour dermal contactdermal contact drinking polluted waterdrinking polluted water


IntroductionIntroduction

Therefore there is a limited set of exposure mechanisms Therefore there is a limited set of exposure mechanisms of POPs to humans. The risk assessment approach has 2 of POPs to humans. The risk assessment approach has 2 stages:stages:

1.1. To quantify the tolerable intake of POPs from an To quantify the tolerable intake of POPs from an individual compound and from multiple compoundsindividual compound and from multiple compounds

2.2. To assess the amount of POPs that an individual, within a To assess the amount of POPs that an individual, within a population, is exposed to from various sources. population, is exposed to from various sources.

This Risk Assessment methodology can be applied to the This Risk Assessment methodology can be applied to the quantification of health and environmental risks from quantification of health and environmental risks from POPs. On the basis of the risk assessment a rehabilitation POPs. On the basis of the risk assessment a rehabilitation strategy and programme of works may be initiated.strategy and programme of works may be initiated.

RISK ASSESSMENTRISK ASSESSMENTRisk Assessment – IntroductionRisk Assessment – Introduction

There are various methodologies, There are various methodologies, backed by modelling systems, backed by modelling systems, available to assess the risks from available to assess the risks from exposure to contaminants.exposure to contaminants.

These mainly rely on assessing These mainly rely on assessing toxic and excess carcinogenic risk toxic and excess carcinogenic risk to a theoretical population as a to a theoretical population as a result of a source concentration result of a source concentration migrating via a potential exposure migrating via a potential exposure pathway. The mechanism is pathway. The mechanism is termed termed Source-Pathway-Source-Pathway-Receptor. Receptor.

The complete link between the The complete link between the source, pathway and receptor is source, pathway and receptor is known as a ‘pollutant linkage’. known as a ‘pollutant linkage’.


Risk Assessment – MethodologyRisk Assessment – MethodologyThe modelling of environmental and human The modelling of environmental and human population risk is termed Quantified Risk population risk is termed Quantified Risk Assessment (QRA) and can be undertaken at a Assessment (QRA) and can be undertaken at a number of levels or Tiers, depending on how number of levels or Tiers, depending on how complex or site specific the modelling is. complex or site specific the modelling is.

International practice is:International practice is:Tier 1 – using simple scientific or economic/political Tier 1 – using simple scientific or economic/political

screening values.screening values.Tier 2 – a theoretical, generic, population predictive Tier 2 – a theoretical, generic, population predictive

level.level.Tier 3 – a single at risk population predictive level. Tier 3 – a single at risk population predictive level.


Risk Assessment – Main ProblemsRisk Assessment – Main Problems

The main problems are:The main problems are:

That only a very limited spectrum of the possible exposure That only a very limited spectrum of the possible exposure pathways can actually be modelled.pathways can actually be modelled.

Food chain uptake of POPs is the most sensitive pathway, Food chain uptake of POPs is the most sensitive pathway, but modelling population bio-accumulation is not advanced but modelling population bio-accumulation is not advanced and experimental data is sparse.and experimental data is sparse.

The movement of POPs contaminated soils and sediments The movement of POPs contaminated soils and sediments on both a local and regional scale occurs making it a diffuse on both a local and regional scale occurs making it a diffuse rather than a point source. Careful attention is needed rather than a point source. Careful attention is needed from a modelling perspective.from a modelling perspective.

RISK ASSESSMENTRISK ASSESSMENTQuantitative Risk Quantitative Risk

Assessment (QRA)Assessment (QRA)

Quantified Risk Assessment Quantified Risk Assessment offers a repeatable, offers a repeatable, reproducible and widely reproducible and widely available methodology to available methodology to assess the environmental assess the environmental risks associated with risks associated with exposure to POPs. exposure to POPs.

Some widely used tools are:Some widely used tools are: US EPA approved - US EPA approved - Risk Based Risk Based

Corrective Action Toolkit for Corrective Action Toolkit for Chemical Releases (E2081-00)Chemical Releases (E2081-00)

For source contaminant For source contaminant migration within fractured and migration within fractured and porous media, soils and rocks, porous media, soils and rocks, an applicable tool is an applicable tool is MODFLOW 2000MODFLOW 2000..

QRACSMTier 1Tiers 2 & 3Exposure AssessmentToxicity

RISK ASSESSMENTRISK ASSESSMENTQuantitative Risk Assessment:Quantitative Risk Assessment:Conceptual Site Model (CSM)Conceptual Site Model (CSM)

A conceptual site model is the A conceptual site model is the first stage, the preliminary stage, first stage, the preliminary stage, of risk assessment. of risk assessment. This determines whether there This determines whether there are any potentially unacceptable are any potentially unacceptable risks associated with an area of risks associated with an area of land. land. It involves the first qualitative It involves the first qualitative assessment encompassing hazard assessment encompassing hazard identification and assessment, identification and assessment, where a hazard is any property or where a hazard is any property or situation, in this case a POP, situation, in this case a POP, which may lead to harm, of which may lead to harm, of human health, ecosystems, etc.human health, ecosystems, etc.Example: Example: US EPA SCEM BuilderUS EPA SCEM Builder (the Site Conceptual Exposure (the Site Conceptual Exposure Model Builder).Model Builder).


RISK ASSESSMENTRISK ASSESSMENTQuantitative Risk AssessmentQuantitative Risk AssessmentCSM – MethodologyCSM – Methodology

For a specific site data can/should For a specific site data can/should be collected:be collected:

Identify hazards posed by the Identify hazards posed by the POPs sources.POPs sources.

Any field or literature evidence of Any field or literature evidence of pathways and potential receptors. pathways and potential receptors.

This information is put together This information is put together and forms the and forms the Conceptual Site Conceptual Site Model.Model.

The hazard can then be assessed. The hazard can then be assessed. This overview is a simplification of This overview is a simplification of reality that aims to identify the reality that aims to identify the key potential sources, pathways key potential sources, pathways and receptors and their and receptors and their interactions or linkages.interactions or linkages.

It may be a text description, a It may be a text description, a table, a drawing or a computer table, a drawing or a computer model.model.



Quantitative Risk Quantitative Risk AssessmentAssessment

CSM – ExampleCSM – Example

Using the example shown in the picture below, an example CSM is as follows:



Quantitative Risk Quantitative Risk Assessment:Assessment:

CSM – ExampleCSM – Example

SourceSource PathwayPathway ReceptorReceptor

PrimaryPrimary SecondarySecondary TransportTransport ExposureExposure

Underground Underground petrol tankpetrol tank

Soil plumeSoil plumeLeaching to water Leaching to water tabletable

AquiferAquifer

Leaching, Leaching, groundwater groundwater transporttransport

Inhalation of Inhalation of vapoursvapours

Residential offsite Residential offsite propertyproperty

Drum store of Drum store of pesticidepesticide

Surface Surface soilsoil

Particulates by Particulates by windwind

Inhalation of dustInhalation of dust Comm. onsiteComm. onsite

Wind & direct Wind & direct contactcontact

Soil Ingestion, Soil Ingestion, dermaldermal

Comm. onsiteComm. onsite


RISK ASSESSMENTRISK ASSESSMENTQuantitative Rik AssessmentQuantitative Rik AssessmentCSM – Pollutant LinkagesCSM – Pollutant Linkages

Pertinent questions to ask:Pertinent questions to ask:

Do sources identified in the Do sources identified in the Conceptual Site Model link Conceptual Site Model link through an identified path, to a through an identified path, to a receptor? receptor?

Is there the potential for the Is there the potential for the pathway to exist and thus link the pathway to exist and thus link the source and receptor? source and receptor?

At this stage these are potential At this stage these are potential pollutant linkages. pollutant linkages.

These will require modelling to see if These will require modelling to see if they become potential they become potential relevantrelevant or or significant pollutant linkagessignificant pollutant linkages..The pollutant linkages can be The pollutant linkages can be sorted as posing an unacceptable sorted as posing an unacceptable or acceptable risk.or acceptable risk.


RISK ASSESSMENTRISK ASSESSMENTQuantitative Quantitative Risk AssessmentRisk Assessment::CSM – CSM – Unacceptable PollutantUnacceptable PollutantLinkagesLinkages

Significant Pollutant Linkages can Significant Pollutant Linkages can be input into a Tier 1 screening. be input into a Tier 1 screening. They become They become UnacceptableUnacceptable Pollutant Linkages, i.e. pose a risk Pollutant Linkages, i.e. pose a risk to the population, when the to the population, when the exposure exceeds the screening exposure exceeds the screening values set at Tier 1.values set at Tier 1.

Tier 2 or 3 assessments can be Tier 2 or 3 assessments can be undertaken where Unacceptable undertaken where Unacceptable Pollutant Linkages can be found.Pollutant Linkages can be found.

This identification of linkages will This identification of linkages will help the definition of intrusive help the definition of intrusive investigation, sampling and investigation, sampling and analyses, and will therefore analyses, and will therefore determine the financial costs. determine the financial costs.

Receptors identified within the Receptors identified within the Conceptual Site Model will Conceptual Site Model will determine the sensitivity of determine the sensitivity of further assessment.further assessment.


RISK ASSESSMENTRISK ASSESSMENTQuantitative Risk AssessmentQuantitative Risk AssessmentTier 1Tier 1

The identified hazard, in this case The identified hazard, in this case the source concentration, is the source concentration, is compared against a national or compared against a national or international standard or international standard or guideline value e.g.guideline value e.g.

EU Drinking Water StandardsEU Drinking Water Standards World Health Organisation World Health Organisation

Guidelines for Drinking Water Guidelines for Drinking Water QualityQuality

Example: The source concentration of Example: The source concentration of POPs in soil, air or water being POPs in soil, air or water being compared against a standard compared against a standard protective of human health or protective of human health or possibly aquatic life/livestock possibly aquatic life/livestock drinking waters.drinking waters.

Note: Many POPs are banned Note: Many POPs are banned internationally so no standards or internationally so no standards or guideline values have been set.guideline values have been set.


RISK ASSESSMENTRISK ASSESSMENTQuantitative Risk Assessment:Quantitative Risk Assessment:Tiers 2 & 3Tiers 2 & 3

The procedure for Tiers 2 and 3 is The procedure for Tiers 2 and 3 is identical, but the populations are identical, but the populations are different. different. See definition of tiers.See definition of tiers.

Site characterisation is carried Site characterisation is carried out, and data collected for the out, and data collected for the CSM, the pollutant linkages can CSM, the pollutant linkages can be quantified in detail. This be quantified in detail. This involves:involves:

Exposure AssessmentExposure Assessment

Toxicity AssessmentToxicity Assessment


RISK ASSESSMENTRISK ASSESSMENTQRA: Tiers 2 & 3:QRA: Tiers 2 & 3:Exposure AssessmentExposure Assessment

Analysis of laboratory and Analysis of laboratory and field data will allow field data will allow identification of the potential identification of the potential POPs hazards at the site in POPs hazards at the site in question, in terms of human question, in terms of human health or ecological effects. health or ecological effects. The hazard will not constitute The hazard will not constitute a risk unless the population is a risk unless the population is exposed and the duration of exposed and the duration of exposure identified.exposure identified.

Therefore the data required are:Therefore the data required are:

I.I. source of source of contaminationcontamination

II.II. environmental media environmental media data e.g. surface soils, data e.g. surface soils, groundwater, air etc…groundwater, air etc…

III.III. points of exposurepoints of exposureIV.IV. routes of exposure e.g. routes of exposure e.g.

taking into account taking into account transporttransport

V.V. receptor populationreceptor population



QRA: Tiers 2 & 3:QRA: Tiers 2 & 3:

Exposure Exposure AssessmentAssessment

1. Analyse Laboratory Data for Constituents of Concern (COCs)

2. Identify Transport Mechanisms Involved.

3. Identify chemical specific factors which are likely to affect transport.

4. Identify transformation and degradation rates

5. Identify the abiotic site-specific environmental parameters likely to affect chemical transport and exposure

6. Identify Points of Exposure (POE)

Key steps involved are:



Chemical and Physical Chemical and Physical ParametersParameters

The chemical and physical The chemical and physical properties of contaminants properties of contaminants (POPs) can be assessed and (POPs) can be assessed and identified, which determine identified, which determine the transport, the transport, bioaccumulation or bioaccumulation or environmental fate of POPs. environmental fate of POPs.

Online databases can be used, Online databases can be used, e.g.e.g.

EPA Superfund Chemical Data EPA Superfund Chemical Data MatrixMatrixFor physical and toxicological For physical and toxicological informationinformation

EPA CHEMFATE databaseEPA CHEMFATE databaseFor mobility informationFor mobility information


RISK ASSESSMENTRISK ASSESSMENTQRA: Tiers 2 & 3:QRA: Tiers 2 & 3:Exposure AssessmentExposure Assessment Important Chemical and Physical Important Chemical and Physical

ParametersParametersI.I. Chemical Name Including CAS Chemical Name Including CAS

No.No.II.II. Concentration and what the Concentration and what the

chemical is used for.chemical is used for.III.III. Physical Properties: e.g. Physical Properties: e.g.

Solubility, Vapour Pressure, Solubility, Vapour Pressure, Melting Point, etc…Melting Point, etc…

IV.IV. Chemical Properties: Flash Chemical Properties: Flash Point, FlammabilityPoint, Flammability

V.V. Toxicological Properties: e.g. Toxicological Properties: e.g. Acute Toxicity, Genotoxicity, Acute Toxicity, Genotoxicity,

VI.VI. Ecotoxicological Properties: Ecotoxicological Properties: Acute Toxicity, Chronic Acute Toxicity, Chronic Toxicity, Sub-Chronic ToxicityToxicity, Sub-Chronic Toxicity

VII.VII. Bioaccumulation potentialBioaccumulation potentialVIII.VIII. Carcinogenic potencyCarcinogenic potency



QRA: Tiers 2 & 3:QRA: Tiers 2 & 3:Exposure AssessmentExposure Assessment Exposure DataExposure Data

The routes of exposure are The routes of exposure are considered at this point. considered at this point. This is the consideration of This is the consideration of all intake pathways. As all intake pathways. As stated previously this may stated previously this may involve drinking water, involve drinking water, food chain uptake via meat food chain uptake via meat and crops, direct ingestion and crops, direct ingestion of soil and dermal contact.of soil and dermal contact.The example on the next The example on the next page shows the exposure page shows the exposure pathways for bio-pathways for bio-accumulation.accumulation.



QRA: Tiers 2 & 3:QRA: Tiers 2 & 3:

Exposure Exposure AssessmentAssessment

Exposure Data ExampleExposure Data Example

CROPS

Air

Soil leaching to GW/SW

Surface Water

Groundwater

CROPS

CATTLE/SHEEP

FISH

DRINKING WATER

Dairy Products

Meat

HUMANS

GRASS


RISK ASSESSMENTRISK ASSESSMENTQRA: Tiers 2 & 3:QRA: Tiers 2 & 3:Exposure AssessmentExposure AssessmentTransport mechanismsTransport mechanisms

Having thoroughly identified Having thoroughly identified the primary source media, the primary source media, e.g. air, soil, groundwater, e.g. air, soil, groundwater, surface water, which will surface water, which will contribute to transport of contribute to transport of contaminants, it is necessary contaminants, it is necessary to determine the transport to determine the transport mechanisms.mechanisms.

The main transport pathways The main transport pathways are:are:

Migration of dust in air Migration of dust in air dependant on particle size dependant on particle size and wind speedand wind speed

Migration of suspended Migration of suspended solids/sediments in surface solids/sediments in surface runoffrunoff

Migration of suspended Migration of suspended solid/sediments in surface solid/sediments in surface waterwater

Migration of colloids to Migration of colloids to groundwater and laterally in groundwater and laterally in groundwatergroundwater

Attenuation to sediments, soil Attenuation to sediments, soil matrix.matrix.



The previous steps are normally The previous steps are normally input to a model to determine the input to a model to determine the variation of concentration over variation of concentration over time at the receptors, e.g. time at the receptors, e.g. groundwater, air, etc… groundwater, air, etc…

This leads to the identification of This leads to the identification of the the Exposure FactorsExposure Factors::

Exposure frequencyExposure frequency - the - the amount of time an individual or amount of time an individual or organism is in contact with POPs organism is in contact with POPs contaminated medium.contaminated medium.

Exposure durationExposure duration – how long – how long the population has been exposed the population has been exposed to POPs or is likely to be exposed.to POPs or is likely to be exposed.

Contact RateContact Rate – – this is the this is the amount of POPs contaminated amount of POPs contaminated material contacted or ingested material contacted or ingested per unit time.per unit time.


RISK ASSESSMENTRISK ASSESSMENTQRA: Tiers 2 & 3:QRA: Tiers 2 & 3:Toxicity AssessmentToxicity Assessment

From the determined From the determined exposures the toxicity exposures the toxicity assessment is undertaken to assessment is undertaken to calculate the lifetime excess calculate the lifetime excess risk.risk.

This step involves assessing This step involves assessing the potential harm to human the potential harm to human health from the identified health from the identified contaminants (POPs) in soil by contaminants (POPs) in soil by comparing exposure comparing exposure information against information against health health criteria, criteria, which is a threshold which is a threshold value, e.g.value, e.g.

In the UK – Tolerable Daily In the UK – Tolerable Daily Intakes (TDIs)Intakes (TDIs)

Elsewhere – Acceptable Daily Elsewhere – Acceptable Daily Intake (ADI)Intake (ADI)


RISK ASSESSMENTRISK ASSESSMENTQRA: Tiers 2 & 3:QRA: Tiers 2 & 3:Toxicity AssessmentToxicity Assessment

Tolerable daily intake is an estimate of the amount of a contaminant, Tolerable daily intake is an estimate of the amount of a contaminant, expressed on a body weight basis, that can be ingested daily over a expressed on a body weight basis, that can be ingested daily over a lifetime without appreciable health risk.lifetime without appreciable health risk.

In this definition ‘tolerable’ should be taken to mean ‘permissible’ rather In this definition ‘tolerable’ should be taken to mean ‘permissible’ rather than ‘satisfactory’.than ‘satisfactory’.


RISK ASSESSMENTRISK ASSESSMENTQRA: Tiers 2 & 3:QRA: Tiers 2 & 3:Toxicity AssessmentToxicity Assessment Non-threshold substancesNon-threshold substances

In the case of carcinogens or In the case of carcinogens or non-threshold substances, they non-threshold substances, they are first classified on a weight-are first classified on a weight-of–evidence approach. of–evidence approach.

The result is that each chemical The result is that each chemical is placed into one of the is placed into one of the following five categories:following five categories:

AA Human CarcinogenHuman CarcinogenBB Probable Human Probable Human CarcinogenCarcinogen

B1B1 indicates indicates limited human evidence.limited human evidence.

B2B2 sufficient sufficient evidence in animals, inadequate evidence in animals, inadequate or no evidence in humans.or no evidence in humans.

CC Possible Human Possible Human CarcinogenCarcinogenDD Not Classified as a Not Classified as a Human CarcinogenHuman CarcinogenEE Evidence of Non-Evidence of Non-carcinogenicity in carcinogenicity in HumansHumans

The excess lifetime risk is The excess lifetime risk is calculated based upon dose-calculated based upon dose-response relationship.response relationship.



Risk CharacterisationRisk Characterisation

Tier 2 and 3 assessment Tier 2 and 3 assessment quantifies the risk in terms of quantifies the risk in terms of excess risk to health. Example, a excess risk to health. Example, a 1% average increase in risk over 1% average increase in risk over a lifetime for a population.a lifetime for a population.

Once the risk of the POP has been Once the risk of the POP has been calculated, its impact on the calculated, its impact on the population under risk can be population under risk can be evaluated.evaluated.

This process involves an assessment This process involves an assessment of the pollutant linkages, the of the pollutant linkages, the amount that the risk is exceeded amount that the risk is exceeded and the possible measures that and the possible measures that could be put in place given the could be put in place given the concentration of the source POP concentration of the source POP and the calculated risk level. and the calculated risk level.

The level of risk that is considered The level of risk that is considered acceptable may be based on acceptable may be based on socio-political judgements. For socio-political judgements. For excess cancer risk values of excess cancer risk values of between 10-4 and 10-6 are between 10-4 and 10-6 are generally considered.generally considered.


RISK ASSESSMENTRISK ASSESSMENTLimitations in Risk Limitations in Risk Assessment ModellingAssessment Modelling

Most models make assumptions Most models make assumptions which give rise to highly which give rise to highly conservative predictions. This conservative predictions. This precautionary approach can lead precautionary approach can lead to unnecessary actions using up to unnecessary actions using up scarce resources that could be scarce resources that could be better applied elsewhere.better applied elsewhere.

The use of risk modelling must be The use of risk modelling must be seen as an attempt to quantify seen as an attempt to quantify environmental risk and as an aid environmental risk and as an aid to decision making, rather than a to decision making, rather than a definitive process of measuring definitive process of measuring likely risks and quantifying likely risks and quantifying effects. effects.

True assessment of risks of POPs True assessment of risks of POPs (or any other contaminant), on a (or any other contaminant), on a population requires a detailed population requires a detailed medical study and long term medical study and long term monitoring.monitoring.


Documents

POPs Risk Assessment. RISK ASSESSMENT Module 2 – Risk Assessment Overview of the course This module introduces POPs Risk Assessment, including Quantitative