Regional Scale Ecological Risk Assessment - Chapter 2 potx

Our working definition of a regional-scale risk assessment is: A risk assessment deals at a spatial scale that contains multiple habitats with multiple sources of multiple stressors affe

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for Regional Risk Assessment 15

What Do You Care about and Where? 18

to the Management Goals 19

of Management Goals, Sources, and Habitats 20

Receptors and to the Assessment Endpoints 20

Habitat to Allow the Calculation of Relative Risk to the Assessment Endpoints 22Step 6 Calculate the Relative Risks 23Integrating Ranks and Filters 23

of the Relative Rankings 24

Investigation to Reduce Uncertainties and to Confirm the Risk Rankings 26Step 9 Test the Hypotheses Listed in Step 8 27

L1655_book.fm Page 11 Wednesday, September 22, 2004 10:18 AM

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12 REGIONAL SCALE ECOLOGICAL RISK ASSESSMENT

Step 10 Communicate the Results in a Fashion that Portrays the Relative Risks and Uncertainty in a Response to the Management Goals 27Overview of the Relative Risk Model Studies 28References 34

INTRODUCTION

Since 1997 the relative risk model (RRM) proposed by Wiegers and Landis(Landis and Wiegers 1997; Wiegers et al 1998) has been used at a variety sites togenerate regional risk hypotheses on a variety of scales These scales have rangedfrom an urban watershed a few square kilometers in size, to a Brazilian rain forest,and to coastal marine areas The studies also incorporate multiple sources of multiplestressors with a variety of endpoints that exhibit a spatial and temporal distribution.The purpose of this chapter is to define regional risk assessment, present the RRM,and to briefly summarize the scope and results of the studies conducted up until thefall of 2003

REGIONAL RISK ASSESSMENT DEFINED

Ecological risk assessment calculates the probability of an impact to a specifiedset of assessment endpoints over a defined period of time In the risk assessment ofchemicals, exposure and effects are estimated and the probability of the intersection

of those functions calculated Impacts typically considered are mortality, chronicphysiological impacts, and reproductive effects Most often these risk assessmentsdeal with single chemicals in such classic cases as pesticides, herbicides, organicsolvents, metals, polychlorinated biphenyls, and dioxins Most often the risk assess-ments dealt with only one or a few biological endpoints

During the 1990s there was an effort to expand ecological risk assessment tomore accurately reflect the reality of the structure, function, and scale of ecologicalstructures Hunsaker, O’Neill, Suter and colleagues (Hunsaker et al 1990; Suter1990; O’Neill et al 1997) formulated the idea of performing regional risk assess-ments at a landscape scale There have been attempts to perform risk assessmentbased upon the classical U.S Environmental Protection Agency (USEPA) paradigm,but each has had limitations (Cook et al 1999; Cormier et al 2000) imposed by arisk assessment framework originally designed for single chemicals and receptors

A principal difficulty is the incorporation of the spatial structure of the environmentand the inherent presence of multiple stressors

We (Landis and Wiegers 1997; Wiegers et al 1998) adopted a definition thatnaturally incorporates multiple stressors, historical events, spatial structure, andmultiple endpoints Our working definition of a regional-scale risk assessment is:

A risk assessment deals at a spatial scale that contains multiple habitats with multiple sources of multiple stressors affecting multiple endpoints and the characteristics of the landscape affect the risk estimate Although there may only be one stressor of concern, at a regional scale the other stressors acting upon the assessment endpoints are to be considered.

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INTRODUCTION TO THE REGIONAL RISK ASSESSMENT 13

FRAMEWORK OF THE RELATIVE RISK MODEL

The framework for the RRM for regional risk assessment was outlined by Landisand Wiegers (1997) Ecological risk assessment (EcoRA) methods traditionallyevaluate the interaction of three environmental components: stressors released intothe environment, receptors living in and using that environment, and the receptorresponse to the stressors (Figure 2.1a) Measurements or estimates of exposure andeffect quantify the degree of interaction between these components At a singlecontaminated site, especially where only one stressor is involved, the connection ofthe exposure and effect measurements to the assessment endpoints can be relativelysimple However, in a regional multiple stressor assessment, the number of possibleinteractions increases dramatically Stressors arise from diverse sources, receptorsare often associated with a variety of habitats, and one impact may lead to additionalimpacts A complex background of sets of natural stressors and effects further cloudsthe picture

Expanding an assessment to cover a region requires consideration of larger-scaleregional components: sources that release multiple stressors, habitats where themultiple receptors live, and the multiple impacts to the assessment endpoints (Figure2.1b) The three regional components are analogous to the three traditional compo-nents, but the emphasis is on location and groups of stressors, receptors, and effects.Traditional risk assessment estimates the level of exposure and effect to calculaterisk However, exposure and effect cannot be directly measured unless a specificstressor and a specific receptor are identified At a regional level, stressors andreceptors can be represented as groups: a source as a group of stressors, a habitat

as a group of receptors, and an ecological impact as a group of receptor responses.These combinations involve the use of a variety of distinctly different measurements

Figure 2.1 Comparison of traditional risk assessment to regional relative risk assessment.

ranked exposures

ranked effects

Locations of Multiple Stressors

Locations of Multiple Receptors

Locations of Multiple Responses

(a) Traditional Risk Assessment Components

(b) Regional Relative Risk Assessment Components L1655_book.fm Page 13 Wednesday, September 22, 2004 10:18 AM

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For example, the measurement of a polychlorinated organic compound will results

in units, mg/L, distinctly different from the occurrence of an invasive species, number

of organisms/m2 Yet both can be present within the area of study Impacts can besimilarly varied, mortality may have to be combined with a decrease with theoccurrence of nonindigenous species It is very intractable to attempt to combinemeasurements taken with distinctly different units

However, it is possible to combine these measurements based on the ment of ranks In this manner a concentration of a chemical that may cause a highdegree of mortality can be combined with an invasion of a new species that willalter a small amount of habitat The criteria for setting ranks are discussed later, butthe crucial feature is that this approach allows the evaluation of multiple stressorsbeing derived from multiple sources impacting a variety of species in a variety ofhabitats in a variety of locations

establish-Relative regional assessment identifies the sources and habitats in differentlocations of the site, ranks their importance in each location, and combines thisinformation to predict relative levels of risk The number of possible risk combina-tions resulting from this approach depends on the number of categories identifiedfor each regional component For example, if two source types (e.g., point dischargeand fish waste) and two habitat types (e.g., the benthic environment and the watercolumn) are identified, then four possible combinations of these components canlead to an impact If in addition we are concerned about two different impacts (e.g.,

a decline in the sport fish population and a decline in sediment quality), eight possiblecombinations exist

Each identified combination establishes a possible pathway to a risk in theenvironment If a particular combination of components interacts or affects another,then they can be thought of as overlapping When a source generates stressors thataffect habitats important to the assessment endpoints, the ecological risk is high Aminimal interaction between components results in a low risk If one componentdoes not interact with one of the other two components, no risk exists For example,

a discharge piped into a deep water body is not likely to impact salmon eggs, whichare found in streams and intertidal areas In such a case, the source component (aneffluent discharge) does not interact with the habitat (streams and intertidal areas),and no impact would be expected (i.e., harm to the salmon eggs) This is analogous

to the overlap among the stressor, receptor, and hazard in conventional risk ment Impact 1 may also be due to the overlap of several sources of stressors withseveral habitats, all altering the risk Integrating these combinations demonstratesthat impact 1 is actually the result of several combinations of sources and habitats

assess-To fully describe the risk of a single impact occurring, each possible route to theimpact needs investigation

Integration of these routes is not always a simple matter and is again facilitated

by the use of ranks Often, measurements of various exposure and effect levelscannot be added together to determine the overall impact to the assessment endpoint.For example, a decline in wild salmon populations can result from a combination

of eggs in the spawning grounds being exposed to chemicals and increased predationwhen the juveniles migrate out of the port However, chemical exposure to the eggsmay also influence growth of the juvenile fish Smaller fish are less able to avoid

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predation, and mortality from predation may increase beyond what would beexpected if the effect to the eggs was not considered

The RRM regional approach is a system of numerical ranks and weighting factors

to address the difficulties encountered when attempting to combine different kinds

of risks Ranks and weighting factors are unitless measures that operate under

2

measurements exist that are additive For example, there is little meaning in addingtoxicant concentrations to counts of the number of introduced predators in order todetermine the total risk in a system However, knowing that a particular region hasboth the highest concentrations of a contaminant and the most introduced predators

is useful in a decision-making process

The next sections take this basic approach and describe the steps in conducting

a regional relative risk assessment, from problem formulation to risk communication

THE 10 STEPS OF THE RELATIVE RISK MODEL FOR REGIONAL RISK ASSESSMENT

The previous reviews of the application of the RRM have led to the formulation

of ten procedural steps that formalize the process The process can also generatethree specific outputs useful in the decision-making process

The procedural steps are

1 List the important management goals for the region What do you care about and where?

2 Make a map Include potential sources and habitats relevant to the management goals.

3 Break the map into regions based upon a combination of management goals, sources, and habitats.

4 Make a conceptual model that links sources of stressors to the receptors and to the assessment endpoints.

5 Decide on a ranking scheme to allow the calculation of relative risk to the assessment endpoints.

6 Calculate the relative risks.

7 Evaluate uncertainty and sensitivity analysis of the relative rankings.

8 Generate testable hypotheses for future field and laboratory investigation to reduce uncertainties and to confirm the risk rankings.

9 Test the hypotheses listed in Step 8.

10 Communicate the results in a fashion that portrays the relative risks and uncertainty

in a response to the management goals.

These ten steps correspond to the portions of the ecological risk assessmentthe initial segments of the framework, especially problem formulation These initialsteps largely determine the success of the risk assessment Steps 4, 5, and 6 areclosely related and do not fit cleanly into conventional framework The conceptual

different limitations than measurements with units (e.g., mg/L, individuals/cm ) (Figure2.2) In a complex system with a wide range of dissimilar stressors and effects, few

framework as depicted in Figure 2.3 The first four steps of the RRM correspond to

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Figure 2.2 The application of ranks and filters in the RRM scheme.

high discharge or activity from the source in the subarea

low discharge or activity from the source in the subarea

no sources of this type

in the area4

large amount of the habitat in the subarea

moderate discharge or activity from the source

in the subarea

moderate amount of the habitat type in the subarea

small amount of the habitat type in the subarea

no habitats of this type

the source is unlikely to occur

or be transported into the habitat

1Scalar Exposure Combination

the source is likely to occur

or be transported into the habitat

source habitat

B

0the impact is unlikely to occur in the

habitat or because of the source

1

Scalar Effect Combination

source habitat source habitat

the impact is likely to occur in the

habitat or because of the source

impact

C

Sum of ranks for each possible combination of sources and habitats

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model is based upon knowledge of source–stressor–habitat–effects linkages mination of the ranking scheme incorporates a large quantity of data generated onthe amounts of stressors, habitats, and what knowledge is available on potentialoutcomes Once the conceptual model and ranking scheme are established the actualcalculation is straightforward Analysis of uncertainty and sensitivity and generation

Deter-of testable hypotheses are the more difficult steps that most closely correspond torisk characterization Testing the hypotheses corresponds to the verification step andshould be incorporated whenever possible

Step 10 corresponds to risk communication and is comprised of three outputs

1 Maps of the risk regions with the associated sources, landuses, habitats, and the spatial distribution of the assessment endpoints.

2 A regional comparison of the relative risks, their causes, the patterns of impacts

to the assessment endpoints, and the associated uncertainty These regional parisons and estimates of the contribution of each source and stressor create a spatially explicit risk hypothesis.

com-3 A model of source–habitat–impact that can be used to ask what-if questions about different scenarios that are potential options in environmental management.

These outputs summarize the data and provide risk assessments and a tool forthe examination of different risk scenarios These outputs facilitate communicationand decision making for the environmental managers The next section describeseach of the ten steps and the three outputs

Figure 2.3 Relationship of the ten steps in the RRM to the classic ecological risk assessment

paradigm.

Problem Formulation

Risk Characterization

Risk Communication

Decision Maker

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The first four steps are critical to performing a regional ecological risk assessmentand are the foundation of a useful risk assessment that can be applied to the decision-making process and to long-term environmental management These steps shouldinvolve close interaction with all of the interested parties The parties include theregulators, the regulated community, the stakeholders comprised of private citizensand nongovernmental organizations, and the risk assessors There are likely to beenvironmental managers in the first three groups who will be involved in the decision-making process The risk assessors need to clearly understand the decision-makingneeds of each of the other groups, communicate the strengths and limitations of therisk assessment process, and attempt to translate management goals stated in non-scientific terminology to features that can be quantified and evaluated In this inter-action the role of the risk assessor is clearly not decision making, but scientific andtechnical support At times the decision makers may need to know that a particulargoal is not part of ecological reality, or that the field of science is not sufficientlyadvanced to provide predictive measures However, the interaction is critical if asuccessful risk assessment is to occur

Step 1 List the Important Management Goals for the Region

What Do You Care about and Where?

The management goals are the key to the rest of the risk assessment Regionalrisk assessments are most effective when they target the decision-making needs andgoals of environmental managers It is important to identify difficult or even con-flicting goals Decisions must be identified early in the process Without identifying,discussing, and resolving these issues, the assessment results will not appear to beuseful to managers, and in fact may not be usable for the decisions at hand.There are four sets of interactions among the regulated community, the regula-tors, and the interested stakeholders in the decision-making process Interactionamong these three groups is expected in three forms First, each will interact withthe other two parties in a bipartite fashion Second, all three parties must interact atthe same time to clearly define the management and decision options in order toanswer basic questions about the future management of the area Third, there arealso interactions between the three groups and the risk assessment team

The role of the risk assessment team is critical In some instances the desireduncertainty reduction is not possible due to resource limitations (Suter 1993), andsome management goals are unattainable as well While a goal may be to restorethe balance of nature or to return the system to a pristine state, given our currentunderstanding of ecological systems, neither of these goals is attainable (Landis andMcLaughlin 2000) However, stakeholders envision the restoration of certain eco-logical resources to within usable limits, and these goals can be quantified andengineered

The management goals for the fjord of Port Valdez and the Codorus Creekwatershed in Pennsylvania were derived from public meetings with representatives

of the various stakeholder groups These groups included the regulated community,the regulators, interested stakeholders, and the risk assessors

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In some instances, such as the Willamette–McKenzie risk assessment, a similarprocess may already have been performed by the appropriate stakeholder groups

In the Willamette–McKenzie study the values were derived from the WillametteValley Livability Forum, a group established by the governor of Oregon with acharge of establishing management goals for the ecological services provided bythe Willamette River and its tributaries The process was driven by consensus forthe period up to 2050 The management goals for fisheries are shown in Table 2.1

The first column lists the goals as defined by this group The second column is thequantitative measure that we used to define this goal In some areas there are conflictswhere two desired goals appear incompatible, but the goal of the risk assessmentteam is to be as inclusive as possible

As this process is completed the management goals are then placed into a spatialcontext with the appropriate sources and habitats

Step 2 Make a Map Include Potential Sources and Habitats Relevant

to the Management Goals

As an example we will use the map-making process for the Cherry Point study,but all of the studies to date incorporate a similar process First, the potential sourceswithin the study area are located, characterized, and placed on a map that includesthe critical topological features of the system The boundaries are set by the man-agement goals of the decision makers, but also take into account the life history ofthe various endpoints Habitat information is also plotted for the endpoints underconsideration Maps can be produced in a variety of ways; the Port Valdez studyutilized conventional maps scanned into a computer and the additional informationwas added in a graphics program Subsequent studies have made extensive use ofgeographical information systems (GIS) that have distinct advantages and disadvan-tages The advantages are clearly the ability to display and analyze geographical

Table 2.1 Examples of Stakeholder Values for Two Sites of Regional-Scale

Risk Assessments Willamette–McKenzie River, OR Codorus Creek, PA

River water is usable as source of drinking

water

Fish from river are palatable and safe to eat

There are sufficient numbers of desirable fish

to support an active recreational and

commercial fishery

Summer steelhead populations

Spring chinook salmon populations

River sustains thriving populations of native fish

Floodplain protection and enhancement for

natural functions and values

Floodplain management for human health and

safety

Water quantities sustain human communities

Maintain reservoirs for fishing, boating, and

windsurfing

Protective water quality for aquatic ecological receptors and humans during contact or consumption

Adequate water supply for drinking and waste discharge

Self-sustaining native and nonnative fish populations in the watershed

Adequate food availability for aquatic species Available recreational land and water resources

Adequate stormwater control and treatment

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information in a variety of formats Unfortunately, not all spatial data are in digitalform, digital data can often be expensive when it does exist, and digital data arekept in a variety of projections which take time to combine Uncertainty related togeographical information is also an issue that will be discussed in Step 7

The next step is to combine management objectives, source information, andhabitat data into geographically explicit portions that can be analyzed in a relativemanner

Step 3 Break the Map into Regions Based upon a Combination

of Management Goals, Sources, and Habitats

The next step is the creation of risk regions that delineate the boundaries of theareas for which risks will be calculated This map is the basis of the rest of theanalysis because risks are all relative based upon the delineated regions The map

is also based upon possible pathways of exposure in a spatial sense to the locationswhere habitat can be found for the assessment endpoints In this regard it may bevery important to follow fate of the water, groundwater, soil, and air within thelandscape to ensure that appropriate sources, stressors, and habitats are incorporatedinto a risk region The chapters that follow in this text provide a variety of methods

of deriving risk regions

Step 4 Make a Conceptual Model that Ties the Stressors to the

Receptors and to the Assessment Endpoints

The conceptual model delineates the potential connections between sources,stressors, habitat, and endpoints that will be used in each risk region An example

of such a conceptual model for hypothetical regional-scale mining and smelting site

heavily forested area along a major river, with dams, transportation corridors, andother activities occurring in the same region The conceptual model is an extension ofthe basic framework for a regional risk assessment with sources providing stressorsinto particular habitats In this instance the habitats are broadly defined as terrestrialand aquatic to capture the exposure pathways and location within the region of ourendpoints There are numerous interconnected endpoints both to show the valuedecosystem components and to illustrate the interdependence and potential indirecteffects

In cases (such as this illustration) where metals can be assumed to be the principalcontaminant, it is important to incorporate all of the confounding stressors Theshaded boxes (Figure 2.4) highlight the conceptual model if only metals were beingconsidered However, all of the endpoints are also being impacted by other stressors

as well A metals-only assessment would take the endpoints and the metals out ofcontext

A well-constructed and informative conceptual model places the site, the sors, the habitats, and the effects into a regional context Such a construction caneliminate some stressors due to the lack of exposure pathways and lead to theinclusion of confounding factors outside the original scope of the assessment

stres-L1655_book.fm Page 20 Wednesday, September 22, 2004 10:18 AM

is presented in Figure 2.4 and was constructed by E Hart Hayes The site is in a

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INTRODUCTION TO THE REGIONAL RISK ASSESSMENT

-South Red-backed Voles

-Columbia Ground Squirrel -Horse -Cow -Chicken

-Erosion -Sedimentation

Change Water Temperature Blockage to Fish

Surface Water Ground Water Soil

Air

Soil Macroinvertebrates

Sedimentation Disturbance to Wildlife

-Black Bear -Black-capped Chickadee -Deer Mouse -Red Squirrel -American Crow

-Coyote -Dusky Shrew -Red-tailed Hawk -American Robin

-Osprey -River Otter -Belted Kingfisher

Contaminants

-Chemicals of Concern -Other (dioxins, PAHs, etc)

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Step 5 Decide on a Ranking Scheme for Each Source, Stressor, and

Habitat to Allow the Calculation of Relative Risk to the Assessment Endpoints

This step changes data into nondimensional ranks so that effects due to thevarious stressors to the various endpoints can be compared (Table 2.2) Each sourceand habitat is ranked between subareas to indicate whether it is high, moderate, orlow within the context of the region Ranks are assigned using criteria specific tothe study region The criteria are based typically on the size and frequency of thesource and the amount of available habitat Ranks are assigned for each source andhabitat type, generally on a two-point scale from 0 to 6 where 0 indicates no habitat

or source and 6 is the greatest amount

There are different means of determining the criteria for ranks In some instancesthere may be adequate concentration response and fate of the stressor data available

to assign ranks to a particular source For an effluent containing one nonpersistentcompound, below an EC10 could be zero, EC10 to EC30 could be low, EC30 toEC50 medium, and greater than an EC50 could be high Typically, that type of data

is not available for most stressors arising from a source

In the chapters that follow there are many examples of ranking schemes withthe criteria listed in the accompanying tables In the case of the Port Valdez scenario

to show all the variables included in the risk assessment In some instances clusteringalgorithms (Codorus Creek, Squalicum Creek, Cherry Point, etc.) were used todetermine natural breaks for the ranking criteria The details are presented in thefollowing chapters

Table 2.2 Example of Ranking Criteria for Stressors for Codorus Creek, PA

Coverage Criteria Ranks Example — Risk Region 1 Rank Scores

Landuse

Industrial % Industrial

< 1

< 1–2 2–16

6 (high)

4 (medium)

2 (low)

70% Slope > 8%, 25% Slope 3–8%, 5% Slope 0–3

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