Toward a new paradigm in Ecological Risk Assessment

Why modelling in ERA?

Marco Vighi

Department of Earth and Environmental Sciences (DISAT)University of Milano Bicocca – Milano - Italy

DISAT

CREAM Open Conference 2013June 10–14, 2013, Leipzig

The first challenge of ecotoxicologyEcotoxicology born in the

second half of the last century to respond to the growing

problems of ecosystem damages due to chemical

emissions.

The first challenge for this new science was producing simple tools for Ecological

Risk Assessment (ERA), capable to provide solutions

for the management of chemicals using the relatively

scarce information realistically available.

The results obtained

These tools represented the basis for international regulations and led to an

increased level of chemical control and to an improvement of environmental

quality.

Traditional ecotoxicological tests and procedures for estimating

environmental concentrations (PECs) and levels safe for the environment

(PNECs) still represent an irreplaceable tool, applicable with a moderate effort

to a large number of chemicals.

The simplified scheme and the need for modelling

Monitoring Modelling

The development of exposure modelling

The most effective tools for predicting chemical exposure in environmental compartments are multimedia models. All multimedia models derive from the

fugacity concept developed by Donald Mackay in the late 1970s.

The original (Level 1) fugacity model allows predicting the

distribution of chemicals in a given environmental scenario (the “Unit

of World”) on the basis of a few physical-chemical properties of the

molecule (S, VP, Kow, T1/2).

Since this simple approach, a huge amount of fugacity-based models have been developed increasing

the complexity and the realism of environmental scenarios.

GIS: GEOGRAPHICAL INFORMATION SYSTEMS

Schematic Approach to territorial characteristic

Reality

Land use

DTM

Urbanised areas

Water streams

Monitoring point

A substantial improvement was determined by the

use of Geographical Information Systems

that allows the detailed description

of complex environmental

scenarios.

The development and refinement of fugacity-based multimedia models allow the reliable prediction of

distribution and fate of chemicals with great detai l…

PECs of pendimethalin in surface water basins of Lombardia

Region

…in space… …and in time.

Peaks of the fungicide pyrimethanil in a river due to runoff corresponding to different rain

events in a six months period after application

pyrimethanil

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

1 501 1001 1501 2001 2501 3001 3501 4001

hours

ng/L

From micro -scale……to global scale.

A box-model representation of the ‘Arctic System’ components and pathways of contaminants (after Macdonald ei al., 2000).

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Schematic diagram of pesticide distribution in the hive ecosystem

(after Tremolada et al., 2011)

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The need for exposure modelling

For several reasons modelling is more effective than monitoring in ERA:

�Monitoring cannot cover all possible exposure situation�Without knowledge on distribution and fate patterns

(modelling) monitotoring provides only puntual data in time and space

�Monitoring is a «a posteriori» approach and does not allow prevention.

Monitoring Modelling

Obviously, experimental data are required to calibrate and

validate models

Nowadays, modelling represents the most important tool for exposure assessment.

Effect modellingThe QSAR approachfrom Hanch analysis to chemiometric methods

The correlation of chemical structure with biological response produced by a set of related drugs is an

impossible problem.

Nevertheless, it is so important and so fascinating that, knowing that noting even approaching a

complete solution is possible, countless investigators have spent their careers on it and countless more will

continue to do so.

Corwin Hansch

QSAR - The Hansch Analysis

Biological System+Toxic substance=Biological Response

Biological Response = f1 (L) + f2 (E) + f3 (S) + f4 (X)

L= lipophylic properties (explaining the uptake)E= electronic properties (explaining the toxicokinetics)S= steric properties (explaining the toxicodynamics)X= additional molecular properties

It was introduced in ecotoxicology since the early 1970s

A perfectly understandable mechanistic meaning

The chemiometric approach

Large toxicity data sets are described using a huge amount of molecular descriptors and elaborated with advanced statistical tools.

Beautiful models are developed with extremely high statistical significance (R2= 0.99….)

BUT…

The mechanistic meaning of chemiometric models is

difficult (sometimes impossible) to understand

Chemiometric tools

Predictive models

Nobody knows whi!

Bioaccumulation models

The number of mispredicted chemicals (false positive or false

negative) is comparable with the old Mackay

equation and with the more complex models.

The original Mackay equation (1982):

Log BCF = Log KOW–1.322

Several new models have been produced recently:

CAESAR ModelMeylan “BCFBAF” model

An attempt was recently made to compare the predictive

capability of the three approaches on three particular

groups of chemicals (unpublished results):

PyrethroidsOrganophosphorusPerfluorinated

The role of QSARs in ERA

QSARs are mentioned in REACH as a potentially powerful tool for

substituting experimental tests for producing ecotoxicological data .

However, there is still some reluctancy in the extensive use of QSARs in ERA,

besides very sinple QSAR equations for narcotics.

The usefulness of QSARs for effect assessment is not comparable to those

of multimedia models for exposure assessment

What can QSARs predict?QSAR models may be suitable for predicting simple

ecotoxicological end points, such as EC50.

Monitoring Modelling Tests QSARs

These endpoints allow estimating a PNEC with officially accepted procedures.

So, a PEC/PNEC ratio may be calculated according with the requirements of chemically-oriented regulations.

Is this enough for an effective

environmental protection?

What has to be protected?

Is a simple PEC/PNEC ratio suitable for this goal?

The objective of environmental

protection is protecting structure and functions

of communities and ecosystems

Indeed, nobody knows what a PEC/PNEC>1 really means in terms of actual ecosystem health

According to van Straalen (2003) the present (and

future) goal of ecotoxicology is providing answers to problems more complex than the simple

dose-response relationships.

The predictive power of ecotoxicology for

describing effects of stress factors at the level of

biological community must be increased.

The new challenge

EXPOSUREASSESSMENT

EFFECTASSESSMENT

RISK CHARACTERISATION

Decades of ecotoxicological research produced excellent

answers to the questions posed by the «original challenges» of

ecotoxicology:Providing simple answers to

complex questions

EXPOSUREASSESSMENT

EFFECTASSESSMENT

RISKCHARACTERISATION

STUDIES ONBIOLOGICAL

SYSTEMS

population dinamicsstructure and functions

of ecosystemsecosystem vulnerabilitysecondary ecological

effects

However, since a long time, the scientific community was aware on

the need for more ecology-based approaches in ERA

STUDIES ONBIOLOGICAL

SYSTEMS

Toward a new paradigm in Ecological Risk Assessment

The old paradigm

Simplifying the system to produce simple

cause-effect relationships

The new paradigm

Understanding and predicting complexity

May ecosystem complexity be accounted for in regulatory approaches?

Even if the guidance documents highlight that the goal for protection are communities and ecosystems, European regulatory tools focused on chemicals (e.g. REACH, PPP Directive) are referred to a “general”

European environment or to more or less standardized environmental scenarios.

In other regulatory tools (e.g. Water Framework Directive, Marine Strategy Framework Directive, Habitat Directive, Soil Framework

Directive) the focus is on ecosystems and not on chemicals.

These tools require a site-specific or region-specific assessment, accounting for the specific responses of ecosystems, their vulnerability

and their particular ecological values

Toward a new paradigm in ERA

In the frame of scientific committees of the European Commission, DG SANCO (SCHER, SCENHIR, SCCS) an opinion has been developed on

Addressing the New Challenges for Risk AssessmentThe ecological subgroup recognised the need for a new paradigm in ERA and

highlighted a number of relevant issues worth to be developed in order to increase its ecological realism.

These issues refer to:

�Improving the realism of exposure assessment

�Improving the realism of effect assessment at higher hierarchical level (community, ecosystem)

�Including the prediction of ecosystem processes (ecological modelling) in ERA

Improvements in exposure assessment

Improvement of modelling approaches:

� Developing models for polar and ionized chemicals as well as for nanomaterials

� Improving the capability to predict time and space variable concentrations in order to account for realistic exposure scenarios

� Developing realistic scenarios with a variation of environmental characteristics to reflect the ecological variability of conditions

� Improving tools for predicting sorption and bioavailability

� Obtain specific organism parameters to extend the applicability of bioaccumulation models in aquatic and terrestrial systems

� Developing models to describe the food web path of chemicals.

The real challenge

Substantial improvements are possible in exposure assessment, such as increasing the realism of environmental scenarios and developing suitable predictive approaches for non traditional

contaminants (e.g. nanomaterials).

Howeverit was the opinion of the working group that the major

challenges refer to effect assessment.

In particular, there is the need for moving from a “general” (national/continental level) assessment to a site-specific

(ecosystem level) assessment.

The new challenges in effect assessmentFrom individual chemicals to multiple stress

Reliable models have been developed for predicting the response to

complex mixtures, but some issues still need to be clarified.The interaction between multiple stressors of different origin poorly known

From simple (constant) exposure to complex variable exposureTesting all possible combinations is impossible . TD/TK models

From single species to complex communitiesBut they are hardly reproducible in controlled conditions

From direct effects to indirect ecological effectsThe consequences of indirect ecological effects on structure and functions

of communities need to be investigated

From «general» scenarios to site-specific assessmentAddressing the vulnerability of different populations, communities and

ecosystems

From taxonomic to functional assessmentImproving trait-based approaches

ERA: the ‘old’ way

ERA: proposal for an ‘improved’ way

EC 2013. SCHER, SCENHIR, SCCS Opinion on

Addressing the New Challenges for Risk Assessment

The need for ecological modellingVery promising tools exist to describe the behaviour of biological

communities and ecosystems, such as trait-based assessment and ecological modelling.

From the OVERALL CONCLUSIONS of:EC 2013. SCHER, SCENHIR, SCCS Opinion on

Addressing the New Challenges for Risk Assessment

However, a big research effort is needed to transfer the knowledge from basic science to practical and regulatory purposes.

In particular, ecological models represent the most logical tool for describing and predicting the behaviour of ecosystems under

stress.

In this sense, they represent the future of ERA and one of the most important priorities for research.

They are already used, but their reliability and soundness for regulatory purposes need to be better proved and validated.

ConclusionsNew ERA science is available or will be made available in the

next future

Substantial ‘ecological’ improvement’ can be made

Not all is ready for use.

An effort is needed for making the new scientific achievements

realistically applicable in ERA

In theory… we have the right paradigm… but, a lot of work must

be done

May CREAM indicate the right way?

The SCHER-SCHENIR-SCCP opinion onAddressing the New Challenges for Risk

Assessmentis available online :

http://ec.europa.eu/health/scientific_committees/environmental_risks/scher_09-13/opinions_en.htm#id9

I would like to thank all contributors to the ecological part of the document:

Colin Brown University of York, UKPeter Calow University of Nebraska, USAFrederik de Laender Ghent University, BelgiumAntonio Di Guardo University of Insubria, ItalyVolker Grimm UFZ Leipzig, GermanyJoop Hermens Utrecht University, The NetherlandsColin Janssen Ghent University, BelgiumRiszard Laskosky Jagiellonian University, PolandMatthias Liess UFZ Leipzig, GermanyDik van de Meent RIVM, The NetherlandsPaul van den Brink Alterra, Wageningen, The NetherlandsNico van Straalen VU University Amsterdam, The Netherlandsand myself

Field ecology is an hard work

Thanks for your attention