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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
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)
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
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
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
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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