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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
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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
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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.
