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Marine Pollution Bulletin 56 (2008) 613–619

Viewpoint

Biomarkers and environmental risk assessment: Guiding principlesfrom the human health field

Richard Owen a,b,*, Tamara S. Galloway d, Josephine A. Hagger a,Malcolm B. Jones a, Michael H. Depledge c

a Ecotoxicology and Stress Biology Research Centre, School of Biological Sciences, University of Plymouth, Drakes Circus, Plymouth PL4 8AA, UKb Environment and Human Health Programme, Environment Agency, Burghill Road, Bristol, BS10 6BF, UK

c Peninsula Medical School, The John Bull Building, Tamar Science Park, Plymouth, PL6 8BU, UKd School of Biosciences, University of Exeter, Geoffrey Pope Building, Exeter, EX4 4QD, UK

Abstract

Although the potential use of biomarkers within environmental risk assessment (ERA) has long been recognised their routine use isless advanced compared with clinical human health risk assessment, where a number of familiar biomarkers (such as blood pressure andserum cholesterol) are in common usage. We have examined how biomarkers are incorporated into human health risk assessment andhave identified several ‘required elements’. These include identification of the (clinical) assessment endpoint at the outset, rational selec-tion of the biomarker(s) (the measurement endpoint), biomarker ‘validation’ (e.g. QA/QC) and biomarker ‘qualification’ (evidence link-ing the measurement and assessment endpoints). We discuss these elements in detail and propose that their adoption will facilitate theroutine use of biomarkers in environmental risk assessment. Furthermore, our analysis highlights the need for cooperation between thoseworking with biomarkers within human and environmental risk assessment to exchange best practice between common disciplines formutual advantage.� 2008 Elsevier Ltd. All rights reserved.

Keywords: Biomarkers; Environmental risk assessment; Human health; Validation; Qualification

1. Biomarkers in human health risk assessment

Within the field of human health, biomarkers are definedas indicators of normal biological processes, pathogenicprocesses or pharmacological responses to a therapeuticintervention (Biomarkers Definitions Working Group,2001). Biomarkers have been and continue to be used forimproving toxin exposure assessment, including assessmentof internal and biologically effective dose (e.g. cotinine as amarker of tobacco smoke exposure, DNA adducts as a mar-ker of biologically effective dose); for providing an under-standing of the underlying basis of disease; for diagnosis,

0025-326X/$ - see front matter � 2008 Elsevier Ltd. All rights reserved.

doi:10.1016/j.marpolbul.2008.01.022

* Corresponding author. Address: Environment and Human HealthProgramme, Environment Agency, Burghill Road, Bristol, BS10 6BF,UK. Tel.: +44 117 915 6805.

E-mail address: richard.owen@environment-agency.gov.uk (R. Owen).

staging and classification of the extent of disease and predis-ease; to predict and monitor disease outcomes; to identifyvariation in susceptibility to disease; and to direct clinicalintervention for disease outcome prevention; to evaluatethe effectiveness of such intervention (Hulka, 1991).

Biomarkers in clinical human health risk assessment fallinto several classes – exposure (internal dose, biologicallyeffective dose), toxicity and health consequence (biologicalresponse, altered structure and function, disease) and sus-

ceptibility (e.g. genetic polymorphisms) (Fig. 1). While bio-markers of exposure are extremely important (notably inforensics and epidemiology), biomarkers of toxicity, healthconsequence and susceptibility are, arguably, of greatervalue to the clinician in a routine setting. Here, biomarkersare extremely useful for directing early therapeutic inter-vention (i.e. as decision support tools). In this regard,prognostic surrogate endpoints such as biomarkers can

(Toxicant Exposure)

Internal dose

Biologically - effective dose

Biological response

Altered structure and function

Disease

Outcome

Surrogates of Exposure

Biomarkers of Toxicity and Consequence

(including surrogates)

Susceptibility

Fig. 1. Biomarkers of exposure, toxicity and consequence within human health (after Hulka, 1991).

614 R. Owen et al. / Marine Pollution Bulletin 56 (2008) 613–619

substitute for traditional clinical assessment endpoints (e.g.disease and survival), which often have prolonged periodsbefore manifestation (Galloway et al., 2000; Devendraet al., 2004a,b). Many of these latter biomarkers will bevery familiar, for example, the measurement of pulse rate,blood pressure, serum cholesterol and prostate-specificantigens. Indeed, a number of these biomarkers (e.g. arte-rial blood pressure, serum cholesterol) are accepted in aclinical and regulatory context as surrogate clinical end-points for human survival associated with (in this instance)cardiovascular disease (Biomarkers Definitions WorkingGroup, 2001). In human health risk assessment, the aimof such surrogate endpoints is, firstly, to predict clinicalrisk and, secondly, to predict clinical benefit (i.e. reductionin that risk) from, for example, therapeutic intervention(Hilsenbeck and Clark, 1993).

One specific use of biomarkers in this regard is the eval-uation of candidate drugs for chronic disease developmentintervention. Here, biomarkers can provide early, cost-effective assessments of both efficacy and safety at theexploratory stage of drug development prior to the morecostly full stage ‘Phase 3’ assessments (clinical trials)required for a drug registration dossier (Rolan, 1997). Clin-ical trials can be very expensive, with long patient follow uptimes (Lippman et al., 1990) and primary assessment end-point events (e.g. cancer occurrence) that may be veryinfrequent. In this context, surrogate endpoints play a spe-cific role in reducing trial cost and duration (Hilsenbeckand Clark, 1993; Frank et al., 2005).

For the purposes of our comparison, we could consideradverse environmental outcomes as being analogous toclinical outcomes, and therapeutic intervention as beinganalogous to risk management interventions aimed atreducing the risk of such outcomes occurring.

As in the clinical setting, while biomarkers of exposureare of enormous value, biomarkers of toxicity and conse-quence (and indeed susceptibility) may have the greatestpotential use in ERA, notably in linking ecological impactsto pollutant exposure (i.e. ‘source apportionment’ and cau-sality), thereby, justifying specific risk management actionsand evaluation of the success of such actions. With this inmind, it is useful to consider some key ‘required elements’for the use of biomarkers of health consequence in humanhealth risk assessment, with a view to informing the moreroutine use of biomarkers of toxic consequence in ERA.Our preliminary overview points to four important ele-ments: (a) identification at the outset of the primary (clin-ical) assessment endpoint; (b) rational selection of thebiomarker(s) (the measurement endpoint), (c) biomarkervalidation and (d) biomarker qualification. We explorethese in more detail below.

2. Selection, validation and qualification of biomarkers

within human health risk assessment

Central to the use of early surrogate measures such asbiomarkers as substitutes for long-term clinical endpointsin the human health field is a requirement for robust evi-

R. Owen et al. / Marine Pollution Bulletin 56 (2008) 613–619 615

dence showing, firstly, that the biomarkers accurately

predict clinical risk and, secondly, where therapeutic inter-vention is advocated, that this intervention reduces such

risk i.e. delivers clinical benefit. As we will see later on, inthose instances where these ‘basic fundamentals’ have beenmet in ERA (for example some types of endocrine disrup-tion) biomarkers have proven to be extremely powerfultools.

The underlying framework for use of biomarkers in clin-ical human health contexts is outlined in Fig. 2. It beginswith the selection of a clinically meaningful assessment end-

point (a primary, clinical endpoint such as mortality). Thisis followed by rational selection of the measurement

endpoint (here one or more biomarkers), establishing ahypothesis that the biomarker constitutes a step in thepathophysiology of a disease outcome, or is directly corre-lated with that step (Hulka, 1991; Hilsenbeck and Clark,1993; Schatzkin et al., 1993; Rolan, 1997). Underpinningrational selection of the biomarker is good biologicalunderstanding of the causal pathways in the disease pro-cess. For example, an understanding of carcinogenesis,including genomic alterations that progress to dysregulatedproliferation and differentiation, has led to selection ofgenomic, proliferation and differentiation markers for thisdisease outcome (Lippman et al., 1990). At this stage, itis worth reflecting that where such mechanistic understand-ing has been developed in ecotoxicology (e.g. endocrine dis-ruption), biomarkers have been shown to be very powerful

Assessment endpoint selec

Measurement endpoint selec identification of putative biom

Development and characterization

Longitudinal studies

Derivation of risk factor fo a given biomarker respons

Validation

Qualification

Selection

Fig. 2. A conceptual framework for selection, validation and qualification ofHilsenbeck and Clark, 1993; Fleming and DeMets, 1996; Rolan, 1997; Bonass

tools (e.g. imposex in dogwhelks, Gibbs et al., 1988). It alsohighlights that improving understanding of the complexand often multi – factorial aetiology of adverse environ-mental outcomes is important for furthering the develop-ment and use of biomarkers in ERA.

Wagner (2002) provides a useful illustration of how eachof these ‘required elements’ has been addressed in thehuman health field, using the well-known example of totalserum cholesterol. Elevated total serum cholesterol hasbeen shown to constitute an important pathophysiologicalstep leading to coronary atherosclerosis and early mortality(mortality being in this case the primary ‘assessment’ end-point). This mechanistic understanding provides a rationalbasis for selecting total serum cholesterol as a biomarker ofmortality resulting from coronary heart disease. However,a rational basis for selection has not in itself been sufficientfor use of this biomarker in health risk prediction within aroutine clinical setting. To enable this, both performanceevaluation (validation) and robust evidentiary studies (qual-

ification) were required. In the case of total serum choles-terol, qualification was needed to show (a) thatcholesterol was clearly linked to increased risk of develop-ment of coronary atherosclerosis and early mortality and(b) that therapeutic intervention (e.g. by administeringof lipid lowering therapeutic drugs (e.g. statins) reducedthis risk. Studies such as the 4S longitudinal study(Scandinavian Simvastin Survival Study Group, 1994)helped provide this important qualification step. The study

tion

tion: arker(s)

r e

Assay development and optimisation (performance characteristics)

a) Evidence of quantitative association between previously measured markerresponse and subsequent outcome.

b) Evidence that marker and outcome both respond to intervention.

Rational basis for selection

Satisfies criteria for a goodassessment endpoint

biomarkers of toxic consequence (after Suter, 1990; Depledge et al., 1993;i et al., 2001; Bonassi and Au, 2002; Wagner (2002); Wagner et al., 2007).

616 R. Owen et al. / Marine Pollution Bulletin 56 (2008) 613–619

was instrumental in showing that lowering cholesterolsignificantly prolonged life; it reported that patients withcoronary heart disease (CHD) who received the statin Sim-vastin exhibited, over a 5 year follow up period, (a)decreased total and LDL cholesterol and (b) reduced totalmortality and major coronary events. It showed that totalserum cholesterol could be used as a biomarker of conse-quence of CHD-associated mortality and that therapeuticintervention using statins reduced both the assessmentand measurement endpoints (Scandinavian Simvastin Sur-vival Study Group, 1994). These sorts of studies have beenimportant in facilitating the use of biomarkers such asserum cholesterol as routine decision support tools in gen-eral medical practice.

It is clear that the qualification process (also termed‘evaluation’ by the Biomarkers Definitions WorkingGroup, 2001) is an important requirement for inclusionof biomarkers in human health assessment (Wagneret al., 2007). As in ERA, ‘unqualified’ biomarkers of toxiceffects have great potential in, for example, supportinghypothesis generation within exploratory research (Wagneret al., 2007). It is the process of qualification, however, thatallows a surrogate endpoint or biomarker of consequenceto be used both as a (regulatory) health management deci-sion support tool and in the assessment of the outcomes ofintervention (in the case above through prescription oftherapeutic drugs). Indeed, it has been recommended thatonly in those instances where the surrogate endpoint hasbeen rigorously validated and qualified can the primaryclinical assessment endpoint be reliably substituted (Flem-ing and DeMets, 1996). In establishing the predictive valueof such a biomarker, the undertaking of longitudinal fol-low up studies (ideally prospective cohort studies) (Schatz-kin et al., 1993; Fleming and DeMets, 1996; Perera, 2000;Bonassi et al., 2001) has been identified as a key step. Thishas two important functions. Firstly, it demonstrates aclear association between a previously measured biomarkerresponse (the measurement endpoint) and the subsequentoutcome (the assessment endpoint). This eliminates theissue of so-called ‘reverse causality’ i.e. that the marker isinduced by the disease rather than the marker being on acausal pathway that results in the disease (i.e. a distinctionbetween diagnosis and prognosis). Such studies establishthe quantitative relationship between the marker responseand the outcome (dose – response). Secondly, it shows thatthe marker and outcome both respond to intervention (Pre-ntice, 1989; Hilsenbeck and Clark, 1993; Fleming andDeMets, 1996).

While many predictive biomarkers of health conse-quence have been developed in the human health field,far fewer have been rigorously validated and qualified(Fleming and DeMets, 1996; Rolan, 1997). It is in thosecases where powerful longitudinal qualification has beenundertaken that biomarkers have had most widespreaduse in health risk assessment and management e.g. bloodpressure and total serum cholesterol as surrogates for car-diovascular risk.

3. Can the use of biomarkers in human health risk assessment

provide insights for the use of biomarkers in ERA?

As with application of biomarkers in human health,there are also similar classes of biomarkers in ERA. Thiswas recognised as long ago as1994, where ecotoxicologicalbiomarkers where classified into those which signal (pollu-tant) exposure, toxic effect, exposure and effect, and suscep-tibility (latent effect); (Depledge, 1994). When using suchbiomarkers, it is important to acknowledge from the outsetthat the context within which they are used in humanhealth and environmental risk assessment differs. Firstly,the protection goals are different: within ERA the emphasisis on assessing and managing risks to populations, commu-nities and ecosystems, rather than those to individualhuman health. Secondly, biomarkers in ERA have often(but not exclusively) been applied in the specific contextof exposure to hazardous substances and consequent effects(i.e. chemical pollution).

In the specific context of chemical exposure, biomarkersin human health risk assessment have, as in ERA, played arole in both the hazard and exposure components of therisk assessment process. Biomarkers such as chromosomalaberrations have, for example, been used as biomarkers ofboth exposure (e.g. Garaj-Vrhovac and Zeljezic, 2002) andtoxic consequence (in this case many cancers, Perera,2000). However, while such chromosomal aberrations canbe caused by chemical exposure, they do not per se neces-sarily identify the specific stressor(s) that may be responsi-ble for this increased cancer risk (Perera, 2000). Currently,to establish this association, this biomarker must be usedwith either exposure data or surrogates (exposure biomark-ers) to establish a link between increased health risk andchemical exposure. In the human health field it is only inthose instances where the biomarker is toxin specific (e.g.aflatoxin (AFB1) adducts) that it can be used both as amarker of exposure and a qualified biomarker of patholog-ical consequence, allowing the use of a single biomarkerapproach (a similar case in ERA might be imposex andTBT exposure). This has important implications for useof biomarkers in ERA: it highlights the need for a multi-biomarker (effects, exposure) approach, or one using acombination of biomarkers and chemical measures ofexposure to link environmental health outcomes with spe-cific stressors (the multiple response concept (Depledge,1994; Hagger et al., 2006 and references within). One usefulframework for this may be the tiered use of biomarkers andchemistry in toxicity identification and evaluation strategicapproaches (TIE).

As with biomarkers in human health risk assessment, itis arguably those predictive biomarkers of toxic conse-quence and susceptibility that have most potential valuein ERA. While the context within which biomarkers areused in ERA is often quite specific (i.e. chemical pollution),we argue that the framework described above for the use ofbiomarkers in human health risk assessment provides somepotentially important guiding principles that translate well

R. Owen et al. / Marine Pollution Bulletin 56 (2008) 613–619 617

between human and environmental risk assessment‘disciplines’.

In fact, a number of the elements described above havebeen previously alluded to within the context of ERA. Aconceptual framework for the use of early biomarkers oftoxic consequence in ecotoxicology as predictors ofincreased risk of the development of contaminant – inducedpathology was for example postulated by Depledge (1989)and Depledge et al. (1993). In this framework, a goal wasset to identify and characterise a set of putative biomarkersthat lie along pathways from chemical exposure to resultantcontaminant – induced pathology i.e. at various degrees ofproximity to the pathological endpoint. These might indi-cate early departures from homeostasis, then initiation ofcompensatory and non compensatory responses. This hypo-thetical model compares well with that suggested by the Bio-markers Definitions Working Group (2001) where multiplebiomarkers that represent various components of complexdisease pathways can provide a range of surrogate endpointsat differing stages of the disease aetiology and offer an assess-ment of treatment effects. Rational selection, validation andqualification of biomarkers underpin both these models.

There are also some good examples where individual ele-ments of this framework have been discussed (and indeedbeen met) in ERA. For example, from the overview above,the first and foremost requirement in human health riskassessment is to identify the (clinical) assessment endpoint.In clinical medicine assessment, endpoints such as mortal-ity or specific diseases have been reasonably well defined.As mentioned above, in ERA such assessment endpointstend to be at population or ecosystem levels of organisa-tion, with definitions that are perhaps less well establishedand may be aspirational (e.g. ‘good ecological status’).Suter (1990) provided some useful criteria to help in assess-ment endpoint selection within ERA. These include theneed for social and biological relevance, the need to beoperationally defined (i.e. measurable rather than aspira-tional), and the need for accessibility to measurement andprediction. One example of where this approach is beingput into practice in ERA is in the EU, where the aspira-tional assessment endpoint of ‘ecological status’ is beingtranslated into operationally-defined and measurable clas-sification tools under the water Framework Directive(2000/60/EC) (Devlin et al., 2007). A discussion of the suit-ability of current assessment endpoints is beyond the scopeof this paper, but it is clear that identifying the assessmentendpoint is a key first step for facilitating the use of anymeasurement endpoint (biomarker or other) in the riskassessment process (and that this is recognised by ERApractitioners).

A second requirement identified above is the rationalselection of a measurement endpoint or biomarker, in thecontext of the selected assessment endpoint. Informedrational selection needs to be underpinned by good, mech-anistic understanding of how and where the marker fitsinto the aetiology of an adverse environmental outcome.In the context of ERA, one example of where this under-

standing has been developed is vitellogenin (VTG) induc-tion in male fish as a marker of steroid oestrogenchemical exposure and endocrine disruption. This is a par-ticularly useful biomarker for assessing chronic exposure tovery low (ng L�1) levels of oestrogen. The use of VTG isunderpinned by good biochemical and physiological under-standing of (ER) receptor agonism by endogenous andxenoestrogens, the role of the oestrogen responsive element(ERE) and subsequent vitellogenin induction in the liver:there is a rational basis for its selection.

A further characteristic of VTG that makes it attractiveas a biomarker of xenoestrogen – mediated endocrine dis-ruption is its sensitivity and the good dynamic range ofits response. This introduces the issue of biomarker valida-tion: the biomarker (measurement) endpoint must clearlybe measurable (including issues of sensitivity, precision,accuracy, ease of use, cost, etc.), possess appropriate tem-poral dynamics (e.g. biochemical memory) and exhibitlow variability (Depledge, 1994). These considerationsallude to the performance characteristics of the biomarker,including QA/QC issues. In fact, such performance issuesand the validation aspect of biomarkers in ERA are wellrecognised and a number of QA/QC frameworks exist forvalidating biomarkers (e.g. BEQUALM, see Haggeret al., 2006 and references therein).

In addition to exposure, VTG induction may yet proveto be a useful predictive biomarker of toxic consequenceassociated with exposure to oestrogenic chemicals. The bio-logical responses of concern associated with exposure tosuch compounds include gonadal histopathologicalresponses (such as development of oviducts and oocytesin the testes of exposed male fish), associated implicationsto fish reproductive health (e.g. the quality and quantityof sperm production) and (ultimately) the sustainabilityof fish populations through impacts on fecundity. Kiddet al. (2007) reported results of a 7-year exposure and fol-low up study in which additions of the xenoestrogen ethinyloestradiol (at approx 5 ng L�1) were made to an experi-mental Canadian lake for 3 consecutive years and impactson fat head minnow (Pimephales promelas) observed dur-ing the exposure and post-exposure periods. High levelsof VTG induction observed in the fish within 7 weeks ofexposure were subsequently followed a year after additionsbegan by histological changes in the gonad of male fishes,with observation of intersex (ovotestes) by the third yearof oestrogen exposure. Measurements of fat head minnowpopulation size and structure over the 7 years showed adramatic collapse of the fish population in the second sea-son of oestrogen additions which was sustained throughthe third season of additions and 2 years after additionswere ceased. Samples have since been collected to assessVTG responses and fish population recovery in 2006, 3years after cessation of the EE2 additions. As with theScandinavian Simvastin Survival Study described above,this sort of longitudinal cohort study may help to qualifyVTG as a predictor of toxic consequence associated withoestrogenic endocrine disruption (Table 1).

Table 1Status of imposex and vitellogenin with respect to biomarker framework elements

Element

Clearly – definedassessment endpoint

Rational selectionof biomarker

Validation Qualification

Imposex Impacts on gastropodsnail reproduction andpopulation sustainability

Mechanisticunderstanding of TBT –induced endocrinedisruption

VDSI index Validationthrough e.g. BEQUALM

Qualification via longitudinal studies. Bothassessment endpoint and biomarker shown torespond to intervention (TBT ban)

Vitellogenin Impacts on fishreproduction andpopulation sustainability

Mechanisticunderstanding of receptor– mediated endocrinedisruption

Varying degrees of validationfor specific (e.g. ELISA)assays e.g. at OECD level

Preliminary qualification via longitudinalcohort study (e.g. Kidd et al., 2007).

618 R. Owen et al. / Marine Pollution Bulletin 56 (2008) 613–619

Another good example of ‘biomarker qualification’ inERA is the well-known imposex biomarker Vas DeferensSequence Index (VDSI) in Nucella lapillus (dogwhelks) asa marker of organotin (e.g. tributyltin) associated toxicconsequence. As with the serum cholesterol example, it isbriefly worth considering how well VDSI as a biomarkerfits into the framework described above, given its successfulapplication in ERA (Table 1).

The primary assessment endpoint in this example is sus-tainability of ecologically – important, intertidal gastropodsnails. Selection of imposex as a biomarker is underpinnedby good mechanistic understanding: imposex is a phenom-enon where female gastropods develop male sex organs andan increase in the severity of imposex in gastropods leads,ultimately, to reproductive failure as the pallial oviductbecomes blocked, leading to sterilisation and prematuredeath of the female snails (Gibbs and Bryan, 1986). Thus,high levels of imposex (the measurement endpoint) can the-oretically be directly related to declines in the population ofmarine gastropods (the assessment endpoint) throughreproductive failure.

Imposex was recognised as being a specific biomarker ofexposure to organotin compounds in the 1980s, sinceextensive field studies showed that the degree of imposexincreased with proximity to boating centres and correlatedwith body tissue concentrations of tin (including the antifo-ulant tributyltin (TBT) and its degradation product dibu-tyltin (DBT) (Bryan et al., 1986). Subsequent biomarkervalidation and qualification work has established imposexas a good predictor of reproductive failure and ecologicalconsequences due to organotin exposure. The developmentand validation of an imposex index (VDSI) was an impor-tant step: VDSI is a measure of impact which describes thedegree to which a community of the marine gastropod snailNucella lapillus is affected by the imposex condition. Theindex ranges from 0 to 6, where a score of 0 indicated thatthe community is unaffected and a score of 6 indicated thatthe majority of females are sterile due to imposex. Valida-tion (QA/QC) of the VDSI has been extensively carried outunder OSPAR.

In terms of qualification of VDSI, this needed to showthat TBT caused imposex, that a given level of imposexled to a population decline and finally (in a similar manner

to therapeutic intervention in human health risk assess-ment), that removal of TBT caused a reduction in bothimposex and gastropod population recovery. Extensivelaboratory studies (e.g. Bryan et al., 1987; Gibbs et al.,1988) showed unequivocally that TBT caused imposexand that the severity of imposex (measured through theVDSI) was linked to reproductive output and alterationsin populations. Since the ban in 1987 by the United King-dom Government on the use of TBT-based anti-foulingpaints on vessels less than 25 m in length there has beensubstantial evidence that TBT contamination hasdecreased and that there has been recolonisation andrecovery of dogwhelk populations (Bray and Herbert,1998; Evans et al., 1995; Birchenough et al., 2002; Cro-thers, 2003).

VDSI as a biomarker appears to fit well within theframework described above, having been both robustly val-idated and qualified. It is perhaps no co-incidence thatVDSI has been adopted by the Environment Agency ofEngland and Wales, under the Water Framework Direc-tive, to assess the risk of a transitional or coastal waterbody failing to meet Good Ecological Status due to TBTcontamination. This is carried out as part of the pressuresand impacts analysis required by Article 5 of the WaterFramework Directive. This suggests that the following ofthe guiding principles outlined in Fig. 2 may help facilitatethe applied use of biomarkers in ERA.

4. Conclusions

A preliminary overview of the use of biomarkers inhuman health risk assessment highlights a number of ‘guid-ing principles’ and a framework that facilitates their use ina routine, clinical or regulatory setting. These principlesinclude the clear identification of the (clinical) assessmentendpoint, rational selection of the biomarker (the measure-ment endpoint), performance evaluation (validation) andqualification. A number of examples in ERA show thatindividual elements (e.g. validation) are being addressedfor specific biomarkers: however, far fewer examples existwhere all these ‘required elements’ have been systematicallyconsidered. Major gaps in the framework appear to lie inthe rational choice of biomarkers in the context of good

R. Owen et al. / Marine Pollution Bulletin 56 (2008) 613–619 619

assessment endpoints and in the area of biomarker qualifi-cation. These activities are simply academic exercises: interms of qualification the relationship between a given bio-marker response and a meaningful adverse environmentaloutcome has been frequently questioned.

In recognition of the importance of developing an objec-tive process for development, validation and qualificationof biomarkers in the human health field, the US Foodand Drug Agency has recently established a qualificationand review process to facilitate and accelerate acceptanceof biomarkers in a regulatory context. This reflects an aspi-ration to move away from a situation where the ‘validity ofpreclinical and clinical biomarkers has been traditionallysettled by debate, consensus and the passage of time’Goodsaid and Frueh, 2007). Similar guidance and reviewprocesses could accelerate and facilitate the acceptanceof biomarkers within regulatory environmental riskassessment.

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