Methodology for Exposure and Risk Assessment in Complex Environmental Pollution Situations

TL;DR: The relationship between the sources, exposure and effects of contaminants to human and ecological receptors are complex and many times are specific to a particular site, to certain environmental conditions and to a specific receptor as mentioned in this paper.

Abstract: Frequently environmental pollution results from different hazardous substances released in the environment, meaning that contaminated sites may have many different chemical sources and transport pathways. Problems concerning environmental pollution affect mainly physical, chemical and biological properties of air, water and soil. The relationships between the sources, exposure and effects of contaminants to human and ecological receptors are complex and many times are specific to a particular site, to certain environmental conditions and to a particular receptor. Often the methodology for exposure and risk assessment to environmental pollution is translated into sets of assessment questions. These questions are used to meet the needs of assessment, particular important in focusing the assessment during the problem formulation. Risk assessments vary widely in scope and application. Some look at single risks in a range of exposure scenarios, others are site-specific and look at the range of risks posed by a facility. In general, risk assessments are carried out to examine the effects of an agent on humans (Health Risk Assessment) and ecosystems (Ecological Risk Assessment). Environmental Risk Assessment (ERA) is the examination of risks resulting from technology that threaten ecosystems, animals and people. It includes human health risk assessments, ecological risk assessments and specific industrial applications of risk assessment that analyze identified end-points in people, biota or ecosystems.

Summary

1. Introduction

• Environmental risk assessment refers to the quantitative and qualitative evaluation of the risk posed to human health and/or to the environment by the actual or potential presence and exposure to particular pollutants.
• An accurate site-specific assessment requires knowledge of contaminant form and how it enters in the environment; environmental conditions affecting contaminant (meteorological conditions, soil chemistry, water and sediment chemistry, etc.); presence of plants or animals contaminant bioaccumulation; pathways and routes of exposure to human or ecological receptors and the effects of the contaminant in the target receptor (EPA, 2007).
• Risk assessments vary widely in scope and application.
• It includes human health risk assessments, ecological risk assessments and specific industrial applications of risk assessment that analyze identified endpoints in people, biota or ecosystems (Fairman et al., 1998).
• Applied industrial applications have been separated as many of these assessments do not look in isolation at people or ecological systems.

2. Risk Assessment Methodology

• More specifically, an environmental risk assessment is an analysis of the potential for adverse effects caused by contaminants of concern from a site to determine the need for remedial action or to develop target levels where remedial action is required.
• It involves analyzing the sources of a release, the mechanisms of chemical transport and the potential health risks to receptors.
• Often the methodology for exposure and risk assessment to environmental pollution is translated into sets of assessment questions throughout the several stages of risk assessment (planning and problem formulation, exposure analysis and interpretation and risk characterization) (EPA, 2007).
• These questions are used to meet the needs of assessment, particular important in focusing the assessment during the problem formulation.
• Each one of this step will be discussed in detail in the following sections.

2.1. PROBLEM FORMULATION

• In the first step the problem must be formulated and certain tasks must be clear before the assessment proceeds.
• The risk source will generate hazards that may be released into the environment contributing to the transport, transfer and fate processes through the atmosphere, subsoil, underground and superficial aquatic systems, leading to the contamination of new environmental sub-compartments.
• During the problem formulation stage the following planning and scoping activities should also be included (EPA, 2007): Define the geographic scale and scope of the assessment; Identify potentially exposed populations and sensitive subpopulations; Characterize exposure pathways and exposure routes that will represent the conceptual model; Describe how exposure will be assessed;.
• Determine how the hazard and the receptor’s dose-response will be assessed; Describe how risks will be characterized.

2.2. HAZARD IDENTIFICATION

• Hazard identification involves the identification of those agents that could possibly cause harm to the receptor (people, organisms or ecosystems), specifying how this harm could occur.
• The methods by which hazards are identified depend on the nature of the hazard and may include toxicological testing, examination of accident rates and epidemiological studies.
• Brainstorming examinations of a process or a procedure, carried out in a small team with a chairman asking questions, also known as What if technique.
• Fault trees analyses: diagram that illustrates combinations of failures that will cause one specific failure or interest, the “top event”; the root is the main event and possible causes of the event are traced back to several initiating events;.
• For the conceptual model several inputs will be needed in order to gather information about the transport of contaminants and chemicals, the target exposed population and the way exposure changes in time.

2.3. RELEASE ASSESSMENT

• A release assessment involves the identification of the risk potential source to introduce hazardous agents into the environment.
• This may be descriptive or involve the quantification of the release.
• It should identify the types of releases, its mechanism, the amount released, timings and probabilities of the release occurrence and a description of how these attributes might change in space and in time as a result of various actions or events (Fairman et al., 1998).
• The likelihood or probability of a release of hazards in a non-quantitative way may be given by “Expert judgment”; based on the results of the hazard identification.
• The likelihood is divided in different categories in terms of expressions such as: likely, may occur, not likely and very unlikely (Wilcox et al., 2000).

2.4. EXPOSURE ASSESSMENT

• Exposure assessment is probably the most variable aspect of the risk assessment process.
• The exposure assessment step requires the use of monitoring data, exposure modelling techniques and also mapping models.
• The aim of this stage is to produce a complete picture of how, when, and where the exposure occurs or has occurred, by evaluating sources and releases and the extent and pattern of contaminant contact with humans or ecologically relevant biota.
• (days per year and the number of years exposed).

2.5. CONSEQUENCE OR EFFECTS ASSESSMENT

• A consequence assessment analyzes the effects of the release or the production of the hazards to the specified receptors, and it involves quantifying the relationship between specified exposures to the hazard, health and the environmental effects of those exposures.
• The effects observed in ecological systems are much more varied and few defined end-points exist at present.
• The consequence assessment should describe how the effects are elicited, link them to the receptor at greatest risk and evaluate how they change with varying exposure levels.
• Ecotoxicity tests will generate the PNEC values.
• As a check procedure during this step, the authors should be able to answer to these questions:.

2.6. RISK CHARACTERIZATION AND ESTIMATION

• Risk characterization and estimation consists of integrating the results from the release assessment, exposure assessment and consequence assessment to produce measures of environmental risks.
• But if this ratio cannot be reduced to below 1 by refinement of the ratio (by gathering of further information and further testing), risk reduction measures are necessary (Fairman et al., 1998).
• Sometimes a quantitative risk assessment approach can not be carried out (no PEC or PNEC can be properly calculated).
• In these cases, a qualitative risk assessment can be used as an alternative in which the risk characterization shall include a qualitative evaluation of the likelihood that an effect will occur under the expected conditions of exposure.

2.7. RISK EVALUATION

• Risk evaluation represents the evaluation of what risk assessment actually means in practice.
• Risk evaluation deals with the trade-off between the perceived risks and benefits.
• On its turn, the public perception of risk depends on the economic, social, legal and political context in which the affected and/or concerned population lives (Fairman et al., 1998).
• Based on the acceptable level of risk, eventual choices of action are determined to achieve the desired level of risk; if a system has a risk value above the risk acceptance level, actions should be taken to address concerned risks and to improve the system though risk reduction measures.

2.8. UNCERTAINTY

• Uncertainty is inherent to all risk assessments.
• Risks associated with a specific risk source and receptor, under pre-specified surrounding conditions, will be expressed in terms of a range (with a lower and upper bound) rather than a single figure.
• Knowing the uncertainty is also important to ensure that the input of the results into the risk evaluation step is realistic and thus to ensure that appropriate risk management decisions are made (Calewaert, 2006).
• Quantifying all sources of uncertainty is difficult.
• Uncertainty should be assessed for each one of the ERA steps.

3.1. APPROACH OVERVIEW

• This section describes the methodology applied to calculate lifetime cancer incidence risk and non-carcinogenic health effects resulting from exposure to radionuclides and chemicals released from a contaminated site during a certain period of time.
• Food crops (leafy and non-leafy, vegetables, grains, fruits); viii) Vegetation (mainly pasture grass) and ix) Animal products (milk, meet, eggs, etc.) (EPA, 1998).
• Models developed previously were used to estimate radionuclide or chemical concentrations in soil and biota, as well as concentrations in vegetation and in milk, from radionuclide or chemical concentration in air, surface water and groundwater.
• Intake and exposures implicit refer to the various locations of exposure as well as to the fraction of time spent at each location.
• Risks are also summed separately for radionuclides, carcinogenic chemicals and non-carcinogenic chemicals.

3.2. SITE CHARACTERIZATION

• As a reference site to apply the risk assessment methodology, a contaminated site from a former Portuguese uranium mine was selected.
• This mine was located in the central part of Portugal and it was exploited for almost a century, first for radium production (1913-1944) and then for uranium concentrates production (1951-2000).
• The mine is surrounded by small houses and country houses, with most of the local population living in a village within about 2 km from the mine.
• A tailing disposal is located near the mine; the liquid effluents, after neutralization and decantation, were discharged into a streamlet flowing to the Mondego river (Bettencourt et al., 1990).
• The contaminated site represents an area of 13,3 ha and until a very recent past radionuclides and chemicals have been released to the air, soil, surface water and indirectly to groundwater as a result of routine operations, accidents and waste disposal practices.

3.3. ENVIRONMENTAL MEDIA CONSIDERED

• An environmental medium is defined as a discrete portion of the total environment that may be sampled or measured directly such as soil, sediment, groundwater, surface water or air (Rood, 2003).
• Environmental media considered in this study that humans may be exposed or consume are: Air; Groundwater; Soil; Food crops; Animal products.

3.4. EXPOSURE ROUTES

• An exposure route is the manner through which a material of concern comes into contact with a human receptor (Rood, 2003).
• Exposure routes that may be considered in this methodology are: Inhalation; Ingestion; Dermal contact with soil and water; Irradiation from air; water, soil and dry sediments (radionuclides only).

3.5. EXPOSURE PATHWAYS

• An exposure pathway is the course that a substance of concern takes from its source (where it began) to its end point (where it ends), and how people can come into contact with (or get exposed to) it.
• Air (physical transport as advection and dispersion); transfer between media can occur – transport media; Surface soils (transfer between media can occur but transport within the medium is not considered – static medium); Animal products (environmental medium for biota; transport within the media is not considered), also known as Environmental media.
• Ingestion; Inhalation; External radiation; Immersion; Dermal contact, also known as Human exposure routes.
• The intake or exposure from each exposure route is multiplied by an appropriate factor relating intake or exposure to risk.

3.6. CONCENTRATIONS AT POINTS OF EXPOSURE IN EACH ENVIRONMENTAL MEDIA AND EXPOSURE SCENARIO DEFINITION

• As a starting point it is assumed that there are measured or modeled concentrations of radionuclides and chemicals in environmental media.
• Concentrations in air, surface water or groundwater transport media are required.
• The receptor may consume water from a private well; groundwater or surface water may also be used to irrigate crops and livestock; Specific health-effects estimates include: incremental lifetime cancer incidence risk from radionuclides; incremental lifetime cancer incidence risk from chemicals and non-carcinogenic effects from chemicals.

3.7. RISK CALCULATION

• For each of one of these cases the authors will consider only the internal exposure by inhalation and ingestion.
• For internal exposure the total risk will be the sum of the risk by inhalation, soil ingestion, water ingestion and foodstuff ingestion.
• The resulting annual cancer risk from indoor radon inhalation is 2,42 x 10 -4 .
• For a long-term chronic ingestion of radium-226 during 75 years the incremental lifetime cancer risk is of 3,42 x 10 -4 which means an incremental risk of one in ten thousand.
• Inhalation of beryllium may result in rhinitis, tracheobronchitis, pneumonitis and death due pulmonary edema or heart failure.

4. Discussion and Conclusions

• The focus of this study was to exemplify how to apply a risk assessment in some of its components.
• A life expectancy of 75 years was assumed to carcinogenesis effects.
• Radionuclide and chemical concentration in soil, air and groundwater, were needed along with parameters describing the exposure scenario.
• The exposure pathways included in this risk assessment represent some of the exposure pathways that may be present in a contaminated site with radioactive materials and heavy metals; however is not an exhaustive list of potential exposure pathways.

Figures

FIGURE 1: General key tasks in a environmental risk assessment (Fairman et al., 1998).

Full text

111
L. Simeonov and M. Hassanien (eds.),
Exposure and Risk Assessment of Chemical Pollution – Contemporary Methodology, 111-132
© Springer Science+Business Media B.V. 2008
METHODOLOGY FOR EXPOSURE AND RISK ASSESSMENT IN
COMPLEX ENVIRONMENTAL POLLUTION SITUATIONS
MARIA DE LURDES DINIS* AND ANTÓNIO FIÚZA
Geo-Environment and Resources Research Center (CIGAR),
Engineering Faculty, University of Porto, Rua Dr. Roberto Frias,
4465-024, Porto, Portugal
*To whom correspondence should be addressed: mldinis@fe.up.pt
Abstract. Frequently environmental pollution results from different hazardous
substances released in the environment, meaning that contaminated sites may
have many different chemical sources and transport pathways. Problems
concerning environmental pollution affect mainly physical, chemical and
biological properties of air, water and soil. The relationships between the
sources, exposure and effects of contaminants to human and ecological
receptors are complex and many times are specific to a particular site, to certain
environmental conditions and to a particular receptor. Often the methodology
for exposure and risk assessment to environmental pollution is translated into
sets of assessment questions. These questions are used to meet the needs of
assessment, particular important in focusing the assessment during the problem
formulation. Risk assessments vary widely in scope and application. Some look
at single risks in a range of exposure scenarios, others are site-specific and look
at the range of risks posed by a facility. In general, risk assessments are carried
out to examine the effects of an agent on humans (Health Risk Assessment) and
ecosystems (Ecological Risk Assessment). Environmental Risk Assessment
(ERA) is the examination of risks resulting from technology that threaten
ecosystems, animals and people. It includes human health risk assessments,
ecological risk assessments and specific industrial applications of risk
assessment that analyze identified end-points in people, biota or ecosystems.
Keywords: Risk assessment, exposure, hazard and environment.

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1. Introduction
Environmental risk assessment refers to the quantitative and qualitative
evaluation of the risk posed to human health and/or to the environment by the
actual or potential presence and exposure to particular pollutants. The
relationships between the sources, exposure and effects of contaminants to
human and ecological receptors are the basis to risk assessment. Environmental
risk tools are based on models that describe pollutant pathways in open
environmental system and simulate or model the release of a hazard from a
source to the environment. In the context of environmental pollution a site
specific assessment is conducted to inform a decision concerning a particular
location. As generic purpose it may determine appropriate soil cleanup levels at
the site; establish water discharge permit conditions to meet regulation
standards and investigate the need for emission standards for sources of hazard
air pollutants (EPA, 2007). An accurate site-specific assessment requires
knowledge of contaminant form and how it enters in the environment;
environmental conditions affecting contaminant (meteorological conditions, soil
chemistry, water and sediment chemistry, etc.); presence of plants or animals
contaminant bioaccumulation; pathways and routes of exposure to human or
ecological receptors and the effects of the contaminant in the target receptor
(EPA, 2007). Risk assessments vary widely in scope and application. Some
look at single risks in a range of exposure scenarios, others are site-specific and
look at the range of risks originated by a facility (Fairman et al., 1998). In
general, risk assessments are carried out to examine the effects of an agent on
humans (Health Risk Assessment) and ecosystems (Ecological Risk
Assessment). Environmental Risk Assessment (ERA) is the examination of
risks resulting from technology that threaten ecosystems, animals and people. It
includes human health risk assessments, ecological risk assessments and
specific industrial applications of risk assessment that analyze identified end-
points in people, biota or ecosystems (Fairman et al., 1998). Although health
and ecological risk assessment are two different types of risk assessment, both
processes are conceptually similar (in fact, ecological risk assessment was
developed from human health risk assessment), but have a differing historical
development, regulatory and policy priorities. Applied industrial applications
have been separated as many of these assessments do not look in isolation at
people or ecological systems. They look at real situations and they are likely to
include engineering risk assessments as part of the overall environmental risk
assessments and may take an integrated approach to human and environmental
risks (Fairman et al., 1998). Although risk assessment is extensively used in
environmental policy and regulation providing the scientific basis for much
legislation and environmental guidelines, the results of risk assessment are not

113
often universally accepted. This is mainly due to problems concerning the
availability and quality of data used in risk assessment, the interpretation of data
and results of the assessment as well as the treatment of uncertainty (Fairman et
al., 1998).
2. Risk Assessment Methodology
More specifically, an environmental risk assessment is an analysis of the
potential for adverse effects caused by contaminants of concern from a site to
determine the need for remedial action or to develop target levels where
remedial action is required. It involves analyzing the sources of a release, the
mechanisms of chemical transport and the potential health risks to receptors.
Usually risk analysis focus on three categories of risk problem: i) source term
risks: associated with the risk of an event occurrence that may result in a release
to the environment (a landfill liner failure, inappropriate treatment of an
effluent discharged in a stream, etc.); ii) pathway risks: address the likelihood
of a certain exposure of an environmental receptor to a hazard following an
initial release (dispersion of a plume downwind of a stack, movement of a
plume in groundwater towards to a receptor point, etc.); iii) the risks to harm
the receptor that might occur as a result of the exposure (adverse health effects
as a result of exposure to hazard gaseous contaminants or drinking water
polluted).
Often the methodology for exposure and risk assessment to environmental
pollution is translated into sets of assessment questions throughout the several
stages of risk assessment (planning and problem formulation, exposure analysis
and interpretation and risk characterization) (EPA, 2007). These questions are
used to meet the needs of assessment, particular important in focusing the
assessment during the problem formulation.
The planning and problem formulation stage provides an opportunity for
initial consideration of the contaminant characteristics and their chemistry.
These considerations, along with other aspects of the assessment, contribute to
the development of a conceptual model that gives the important elements of risk
assessment. The next step should provide information about the exposure and
the consequence effects. Tools and methods should be used to conduct a
specific analysis of these two processes resulting in a receptor exposure
assessment and a stressor dose-response assessment. Interpretation and risk
characterization involves risk estimation, uncertainty analysis and risk
description. The final step is communicating results to risk managers in order to
carry out the risk management, by the application of the assessment results, to
define management options and communicate them to the interested parties
(EPA, 2007).

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FIGURE 1: General key tasks in a environmental risk assessment (Fairman et al., 1998).
There are several unifying principles underlying all risk assessments but to
carry out a environmental risk assessment, six steps should be followed as
guidelines (Fairman et al., 1998) (Figure 1):
i) Problem formulation (provides initial consideration of contaminant
characteristics and their chemistry);
ii) Hazard identification (what chemicals are present and are they likely
to be toxic?);
iii) Release assessment (sources and rate releases);
iv) Exposure assessment (who is exposed, at what concentration, how
often and for how long?);
v) Consequence or effect assessment (how is it toxic and at what
exposure levels and what is the effect on the receptors);
1. PROBLEM FORMULATION
What need to be assessed?
4. EXPOSURE ASSESSMENT
How does the released material
reach the receptor, at which
intensity, for how long or/how
frequent?
How likely will be the receptor
exposed to the released pollution?
3. RELEASE ASSESSMENT
How often or how likely?
Release to water and air (direct);
Water, air, sediment and biota (indirect).
2. IDENTIFICATION OF
HAZARDS
5. CONSEQUENCE OR
EFFECT ASSESSMENT
What is the effect on the receptors?
8. RISK
MANAGEMENT
7. RISK EVALUATION
How important is the risk to those
concerned, those who create it, and
those who control it?
6. RISK ESTIMATION AND RISK
CHARACTERIZATION
Quantitative or qualitative measure of
risk.
INFLUENCIAL FACTORS
Political, Legal, Economical, Social

115
vi) Risk estimation and characterization (what does the risk assessment
tell us about the situation and what are the risks, quantitative or
qualitative).
Environmental risk assessment is also likely to include a seventh step given
by risk evaluation defining how important is the risk to those affected, those
who create it, and those who control it.
This step has laid down in the European legislation of new and existing
substances (Fairman et al., 1998). The conclusions made in the risk
characterization and/or risk evaluation are used as input for risk management in
order to come up with an answer to which actions should be taken and how
should the remaining risks be handled. Each one of this step will be discussed in
detail in the following sections.
2.1. PROBLEM FORMULATION
In the first step the problem must be formulated and certain tasks must be clear
before the assessment proceeds. These tasks should be based on (EPA, 2007):
“What are we actually attempting to assess? What is the risk source? Is it a
single chemical, an industrial plant or a process such as transportation? Are we
concerned with the production, use or disposal of the hazard?” The risk source
will generate hazards that may be released into the environment contributing to
the transport, transfer and fate processes through the atmosphere, subsoil,
underground and superficial aquatic systems, leading to the contamination of
new environmental sub-compartments.
Also one should be point out the reasons why we are carrying out the risk
assessment; which hazards should we include in the assessment; if it is based on
regulatory standards to determine the “acceptable risk” or if regulatory and
policy frameworks are being used to identify the most relevant end-points
(EPA, 2007). During the problem formulation stage the following planning and
scoping activities should also be included (EPA, 2007):
 Define the geographic scale and scope of the assessment;
 Identify potentially exposed populations and sensitive subpopulations;
 Characterize exposure pathways and exposure routes that will represent the
conceptual model;
 Describe how exposure will be assessed;
 Determine how the hazard and the receptor’s dose-response will be
assessed;
 Describe how risks will be characterized.

Frequently asked questions

Q1. What have the authors contributed in "Methodology for exposure and risk assessment in complex environmental pollution situations" ?

The relationship between the sources, exposure and effects of contaminants to human and ecological receptors are complex and many times are specific to a particular site, to certain environmental conditions and to the particular receptor this paper. 

Q2. What were the parameters needed to describe the exposure scenario?

Radionuclide and chemical concentration in soil, air and groundwater, were needed along with parameters describing the exposure scenario. 

Q3. How many ha of contaminated soil are there?

The contaminated site represents an area of 13,3 ha and until a very recent past radionuclides and chemicals have been released to the air, soil, surface water and indirectly to groundwater as a result of routine operations, accidents and waste disposal practices. 

Q4. What is the current plan for a tailings reclamation scheme?

a rehabilitation plan based on an in-situ reclamation scheme to promote the confinement of the tailings materials is under implementation as well as a wastewater treatment system implemented in the mining area (Nero et al., 2005). 

Q5. How many people are affected by contaminated leafy vegetables?

The total incremental cancer risk incurred by the ingestion of contaminated soil, water, leafy vegetables and milk is 1,81 x 10 -3 , which means an excess risk of one in one thousand mainly due to leafy vegetable ingestion and water ingestion. 

Q6. What is the definition of a release assessment?

A release assessment involves the identification of the risk potential source to introduce hazardous agents into the environment. 

Q7. What are the main sources of uncertainty in the ERA?

Uncertainty can arise from several potential sources (Calewaert, 2006): Uncertainty inherent to methods used in each of the ERA steps: choice ofmodel, assumptions made in used models, uncertainties related to the model structure itself as the lack of confidence that the mathematical model is an adequate representation of the assessment problem; Uncertainty related to the collected data and parameters: gaps inhistoric/recent data, use of data from other situations and extrapolations to fill out gaps, variability of a model parameter from its true heterogeneity over space and time, uncertainty of a model parameter resulting from the lack of information or knowledge about its true value; Uncertainty of the analyst: interpretation of ambiguous or incompleteinformation, human error, uncertainty of how an assessor translates a real or forecasted situation in a given model. 

Q8. What is the hazard quotient for beryllium exposure?

The resulting hazard quotient to quantify the noncarcinogenic health effects incurred by beryllium inhalation is HQ = 0,05 which is inferior to one; the exposure to beryllium in this scenario does not pose any risk. 

Q9. What is the effect of the public perception of risk?

On its turn, the public perception of risk depends on the economic, social, legal and political context in which the affected and/or concerned population lives (Fairman et al., 1998).