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Ecotoxicology
Day 2.
Adam Peters and Graham Merrington
2017
1
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What is a ecotoxicology?
Endpoints
Test principles and interpretation
Hypothesis testing
Regression modelling/curve fitting
Reliability and relevance
2017
2
What is a ecotoxicology?
(ECHA 2011, R7b) again
 Typically standardised tests aimed at comparing
different chemicals
 Simple tests on organisms which are readily
cultured in the lab
 Standardised test procedures
 Performance of control animals critical for a valid
test
 Tests usually performed under optimum conditions
for the test species
2017
3
Endpoints?
 What counts as an effect?
 Acute – Mortality
 Chronic – endpoints relating to development, growth,
or reproduction
 What kinds of plants and animals get tested?
 Unicellular green algae
 Water fleas (Daphnia)
 Fish
2017
4
Testing?
(OECD 201, 202, 203, etc.)
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Acute Daphnia test
10 water fleas in plastic cups
Are they alive or not?
Prod with a pencil, does it move?
If it doesn’t move it’s immobilised
» (presumed dead)
 Endpoint is immobilisation
» Assumed equivalent to mortality
2017
5
Results?
 10 Water fleas (Daphnia)
 All alive – no effects
 All dead – 100% effects
» Lethal Concentration LC100, Effective Concentration EC100
 5 dead, 5 alive – 50% effects
» LC50 or EC50
2017
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Statistical Analysis
 ANOVA – Analysis of variance
 Requires replication at each test concentration
level
 Identifies a difference from the control
 Used to identify the highest test concertation with
no effects
» No Observed Effects Concentration (NOEC)
 Lowest test concentration at which a significant
effect was observed
» Lowest Observed Effect Concentration (LOEC)
2016
7
Alternative Approach
 Curve fitting
 Uses data from the entire experiment
 Allows more test concentrations with fewer
replicates for each one
» Same total number of replicates
 Allows calculation of any effect level
» EC10, EC25, EC50, EC90
 EC10 usually treated as equivalent to a NOEC for
PNEC and EQS derivation in Europe
2016
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Test Quality and Standardisation
 Most tests conducted to OECD standard guidelines
 Many also conducted to GLP
 Reliability criteria specific to each test
» Information in test guidelines
 Control performance?
» Minimum performance required for a valid test
» Usually based on endpoint used
 Standardised water chemistry common
» Different for different test species
2016
9
Chronic tests
 Usually same test species
 For deriving longer term thresholds more reliably
 Relevant endpoints growth or reproduction
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Algae
Daphnia
Fish
Rotifer
Plant
Molluscs
Insect
population growth
reproduction (# of offspring)
growth (biomass, length) or development
population growth
root growth
growth (biomass, shell length)
growth (biomass, length)
2016
10
Data Sources
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Study summaries e.g. IUCLID/ECHA
Study reports – if available
Open literature
Other reviews – OECD, ICCA, ESR, NICNAS, ECETOC
» Thresholds may not be directly usable, but data should have
been reviewed and summarised
» Different interpretation of the same data may be required
» NOEC vs EC10 vs EC25, SSD vs deterministic, AF?
2017
11
What Data Counts
 Test data for a species which is not locally or
regionally relevant is taken as being representative
of other untested locally and regionally relevant
species
 Include all reliable and relevant data
 Relevant endpoints should have a direct link to
population viability
» Many behavioural endpoints are not relevant!
2017
12
Non standard tests
 Usually from research laboratories
 Different species and taxonomic groups which
might be required to represent an ecosystem
 Insects, molluscs, plants, worms, etc.
 Can be difficult to assess adequacy of control
performance without guidance
» Difficulties in drawing conclusions about the test
 Could also be standard species under nonstandard test conditions, or in natural waters
2017
13
Summary
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Standardised species
Standardised tests
Standardised endpoints
Existing regulatory summaries
2017
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2016
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