Principle Response Curves (PRC)

Populations and communities - Micro- and Mesocosms

resp

onse

+

-Short-term impact Recovery of the communities

time

Control

Low levels

Medium

High

Classification of effects in multispecies-mesocosms

Populations and communities - Micro- and Mesocosms Brock et al. 2001

Class 1: “effect could not be demonstrated”

Class 2: “slight effect”

Class 3: “pronounced short-term effect”

Class 4: “pronounced effect in short-term study”

Class 5: “pronounced long-term effect”

Classification of the observed effects

Populations and communities - Micro- and Mesocosms

Treatment levels (ug ai/L nominal)0.1 0.3 1 3 100

Population responses Insecta 2 2 2 2 2 Macro-Crustacea 1 3 5 5 5 Other macroinvertebrates 1 1 1 5 5 Micro-crustacea 2 3 3 3 4 Other zooplankton (Rotifera) 2 2 2 3 4 Phytoplankton 1 2 3 4 4 Macrophytes 1 1 1 1 1Community responses Community metabolism 1 1 1 1 3 Macro-invertebrates (PRC) 1 3 4 5 5 Zooplankton (PRC) 3 3 4 5 5 Phytoplankton (PRC) 1 2 3 4 5

Taxa used for population responses:Corixidae (Nets)Crangonyx pseudogracilis (ESAS)Tubifex spec. (ESAS)CopepoditesKeratella quadrataNitzschia palea

NOEC Makrophytes: >100 µg/LPhytoplankton: 0,1 µg/LInsecta: <0,1 µg/LZooplankton comm. <0,1 µg/L

NOEAEC: 0,3 µg/L

48 h EC50 Daphnia x 0,01 = 0,011 µg/L

Ecotoxicology

Risk assessment and risk management

Lecture contents

• IntroductionPhenomenons and principles

• Exposure (Environmental chemistry)Chemicals in the environment Classes of chemicals Chemical properties Processes

• Effects on individualsDose-response-relationships Acute and chronic toxicity Toxicity tests Subcellular tests, Biomarker Combined effects

Lecture contents (cont.)

• Effects on populations and communitiesPopulation characteristics Community characteristics Micro- and Mesocosms In situ systems Field studies: ecosystem-effects

• Risk assessment and risk managementFundamentalsLegislationEcological risk assessment (ERA)

Risk assessment and risk management

Fundamentals

Ecological Risk - A Definition

The probability of the occurrence of an adverse effect on individuals, populations, communities or ecosystems

Ecological Risk Assessment - A definition

• changes to ecological systems, lakes, rivers, forests, draining wetlands

• introducing new species, GMOs, chemicals• effects may be local (hazardous waste sites),

regional or global

Ecological risk assessment is the practice of determining the nature and likelihood of effects of our actions on animals, plants and the environment

RISK ASSESSMENT FOR CHEMICALS, What is it?

Scientific process including the following elements

• Hazard identificationidentification of the adverse effects a substance has, the inherent

capacity to cause effects• Effects assessment

definition of the dose response relationship (incidence and severity of effect)

• Exposure assessmentemissions, transformation/degradation rates, movement to estimate

concentration in environmental compartments, varies with time and space

• Risk characterisation estimation of the of the incidence and severity of effects

Risk Management - A definition

Risk Management is a policy-based activity that defines risk assessment questions and endpoints to protect human health and the environment. It takes the scientific risk assessment and incorporates social, economic, political and legal factors that impinge or influence the final decision and selects regulatory actions

Ecological Risk Assessment for Chemicals

Legislative framework: general

Legal Data Requirements

Notification of New Substances NONS (92/32/EEC).

Type of Notification Annual Quantity Cumulative QuantityLevel 2 (1000 t) > 1000 t > 5000 tLevel 1 (100 t) > 100 t > 500 tLevel 1 (10 t) > 10 t > 50 tVII A > 1 t > 5 tVII B > 100 kg and < 1 t > 500 kgVII C > 10 kg and < 100 kg < 500 kg

• Level VII A ecotoxicological requirements beginAcute fish, Daphnia, algae

• Level IProlonged toxicity study with Daphnia magna (21 days)Tests on higher plantsFurther toxicity studies with fishTests for species accumulation: one species, preferably fish

• Level 2Further toxicity studies with fishAdditional toxicity studies with other organisms

Legal Data Requirements

Notification of New Substances NONS (92/32/EEC)

Ecotoxicology & Risk Assessment: Pesticides

EU US Birds and Mammals x xBees x (x)Non-target arthropods x -Earthworms x -Soil micro-organisms x -Non-target plants x xFish x xAquatic Invertebrates x xAquatic plant growth x x

Ecological Risk Assessment

ERA: How it works?

Tiered or stepwise procedure

Tier 1 - protectiveto screen out low risk chemicals, uses, organismsstandard procedures focus risk assessment for tiers 2 and above

Tiers 2 and above - predictiverefine risk assessment by reducing the uncertainty in the effects (toxicity) and/or

exposure assessmentsgenerally done on a case-by-case basis

Ecological Risk Assessment for Chemicals: Tiers

• Tier 1 commonly uses a quotient approach - deterministictoxicity/exposure = x exposure/toxicity = 1/xapply safety factor and determine whether low (acceptable, negligible) risk or

high (unacceptable) risk• Standard procedures exist

ERA: Tier 1

• New and existing substances (EU Council Directives 67/458/EEC, 92/32/EEC, 93/67/EEC, Council regulations 793/93, 1488/94) biocides (EU Directive 98/8/EC) Effect concentration (toxicity - LC/EC50, NOEC)Divide effect concentration by assessment (safety) factor to derive Predicted No

Effect Concentration (PNEC)If PNEC > Predicted Environmental Concentration (PEC) then low risk 1000 is applied to base set data requirements of fish 96 h LC50, Daphnia

Ecological Risk Assessment: Tier 1 for Chemicals

• PesticidesEU (Directive 91/414/EEC)

Toxicity/Exposure (PEC) = Toxicity Exposure Ratio (TER)If TER > trigger, low risk

US EPA (FIFRA)Exposure/Toxicity = Risk Quotient (RQ)If RQ < Level Of Concern (LOC) then low risk

Ecological Risk Assessment: Tier 1 for Pesticides

Pesticides – Risk Assessment: Tier 1 EU Uniform principle

91/414/EEC Annex VI Requirements

….no authorisation shall be granted if …..[TER < Trigger value]

...…unless it is clearly established through an appropriate risk assessment that under field conditions no unacceptable impact on the viability of exposed species occurs…...

Aquatic TER triggersacute = 100, chronic/algal growth = 10

Birds and Mammals, Wormsacute = 10, chronic = 5

Ecological Risk Refinement - Pesticides: Higher Tiers

Tier 1 - worst-case exposure, effects, toxicity, large safety factor to cover uncertainty

If Tier 1 does not indicate low risk….accept mitigation …… or

Tier 2 - reduce uncertainties in the assessmentHow muchSuch that the risk is “acceptable”

Reduction of Assessment Factors to Derive PNEC

TGD in support of Commission Directive 93/67/EEC

At least one short term L(E)C50 from each of 3trophic levels in the base set (fish, Daphnia andalgae)

One long term NOEC (either fish or Daphnia)

Two long-term NOECs from speciesrepresenting two trophic levels (fish and/orDaphnia and/or algae)

Long term NOECs from at least three species(normally fish, Daphnia and algae) representing3 trophic levels

Field data or model ecosystems

1000

100

50

10

reviewed on a caseby case basis

Assessment factor

Ecological Risk Assessment: Calculations at Different Tiers

• Tier 1 - quotient, 3 inputsToxicityExposureSafety Factor

• Tiers 2 and aboveExpressed simply - alter one or more of the inputs

PEC < or > 1PNEC (tox/AF)

Toxicity < or > triggerExposure

Higher Tier ERA: Reducing uncertainty

• Tier 1 limited data set/assumptions, exposure, toxicity, safety factor - UNCERTAINTY

• Refined Risk Assessment REDUCES UNCERTAINTYExposure

Time weighted average concentrationsHigher tier modelling, landscape, satellite images, GIS (Geographic

Information Systems)Toxicity

Further assessment of existing toxicity data e.g. dose response or time to response

Toxicity under environmentally realistic exposures, lab population studies, indoor/outdoor microcosms field studies/monitoring

Safety factorInterspecies sensitivity - SSDsField studies can result in no safety factor

Time/Concentration Response: Modifying PECs

• Which PEC should be used in risk assessment ? • With no additional information use peak for both acute and

chronic riskconservative (appropriate at tier 1)but will often overestimate risk as concentration and time are both

generally important in determining the dose, which in turn givesthe effect

Time/Concentration Response

Interrogation of base-set data can give indication of importance of time

At standard 96 h endpoint toxicity of A an B is the same 2 mg/l

Different profile up to 96 h

Fish LC50 values

0

1

2

3

4

5

6

24h 48h 72h 96hExposure Time

AB

Time/Concentration Response - Modifying PECs Example

Pesticide toxicity to fish, 1000 ug/l to 250 ug/l over 24 to 96 hours

Enters aquatic environment- peak concentration 10 ug/l - dissipates rapidly, 1/2 life 0.5 days

LC50 to Fis

0200400600800

10001200

0hr 24h 48h 72h 96h

Assessment ti

Actual PEC 0 to 96 ho

0

2

4

6

8

10

12

0h 12h 24h 36h 48h 60h 72h 84h 96h

Time

Time/Concentration Response - Modifying PECs -Example

• Initial Risk CharacterisationTER = 96 h LC50 = 250 = 25

initial PEC 10TER < trigger of 100, refine risk assessment or mitigate

• Exposure as initial PEC is clearly worst-case and may overestimate risk

• Provided no latency (need to demonstrate through mode of action/toxicity or experimentally) time weighted average (twa) PECs are more appropriate

Time/Concentration Response - Modifying PECs - twa

PEC(twa) at time t = Co x ((1 - e-(k.t))/k.t)where Co = initial concentration

k = ln(2)/DT50t = elapsed time

Elapsed Time twa conc. (ug/l)24 h 5.448 h 3.472 h 2.496 h 1.8

Actual PEC 0 to 96 ho

0

2

4

6

8

10

12

0h 12h 24h 36h 48h 60h 72h 84h 96h

Time

• Having established lack of latency can use twa PEC• Reluctance to move away from standard assessment times• TER = 96hour LC50 = 250 = 140

96h twa PEC 1.8

• Refined risk assessment demonstrates TER > trigger in 91/414/EECAnnex VI of 100, indicating low risk

Time/Concentration Response - Modifying PECs - twa

Modified Exposures – Changing Toxicity

• Use environmental fate properties of chemical to modify exposure

• Hydrolysis - static system will often reflect environmental exposures compared to flow-through

• Common method is use of sediments in static testsdissipation through adsorption and/or

degradationmimics fate in exposure modelling, not

controlled• Simulate modelled exposure with dosing system

Modified Exposure Studies

• Alternative in risk assessment to use of twa PEC• Does not affect assessment factors (trigger values) or exposure values

used in risk assessment• Produce a time-varying exposure using fate parameters and modify the

effects (toxicity) estimate in risk quotient approach and compare to max PEC

• Will modify results if time to effect long relative to time of dissipation

Modified Exposure Studies

Example: Pyrethroid toxicity in Water-sediment Systems

Water phase application – results on nominal conc. in water phase

72 hour EC/LC50 (ug/l)water water/sediment

Daphnia magna 0.41 1.4Cloeon dipterum 0.25 0.62Asellus aquaticus 0.16 0.62Lepomis macrochirus 0.18 0.69

Reduction in toxicity, caused by adsorption to sediment, reducing exposure

Summary: Time Weighted Average PECs/Modified Exposures

• Alternative approaches modifying exposure (twa) or effects part of the equation

• Whether appropriate can be determined from base set fate and effects data

if time to effect in standard tests is long relative to dissipation time (DT50) , time weighted average or modified exposures may produce mitigated effects result

if time to effect short relative to dissipation time then little difference in results between modified exposures and standard tests would be expected

Ecological Risk Assessment: Summary

• Tier 1 limited data set/assumptions, exposure, toxicity, safety factor - UNCERTAINTY

• Refined Risk Assessment REDUCES UNCERTAINTYExposure

Time weighted average concentrationsHigher tier modelling, landscape, satellite imagery, GIS (Geographic

Information Systems)Toxicity

Further assessment of existing toxicity data e.g. dose response or time to response

Toxicity under environmentally realistic exposures, lab population studies, indoor/outdoor microcosms field studies/monitoring

Safety factorInterspecies sensitivity - SSDsField studies can result in no safety factor

Probabilistic Risk Assessment (PRA), general principle

• Instead of deterministic relations use of probabilisticdistributions => range of values for both the exposure dataand known toxicological effects

Risk assessment and risk management - ERA

Organizational

• See you next week• Oral examen, when?

Prüfungsleistung

• Reproduktion von Wissen (Wiedergeben)Was ist ein LC50?

• Reorganisation von Wissen (Verstehen)Bei was für Situationen sind LC50 Werte anzuwenden?

• Transfer (Anwenden)Gefahr eines Dammbruches, dann gelangt Substanz XY mit 5 µg/L in

angrenzendes Gewässer, 3 d Zeit zur Beurteilung der möglichen Folgen, Was tun?

• Problemlösung (Beurteilen)Wasserwerk hat Probleme mit Organismen in den Leitungen und

möchte diese regelmäßig mit Chemikalien entfernen. Entwicklung eines Untersuchungskonzeptes, insbesondere Festlegung der zu verwendenden Konzentrationen!

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