1. Ecotoxicology Day 2.
Adam Peters and Graham Merrington
2017

2. What is a ecotoxicology? Endpoints Test principles and interpretation
Hypothesis testing
Regression modelling/curve fitting
Reliability and relevance
2017

3. 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

4. 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

5. Testing? (OECD 201, 202, 203, etc.) 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

6. 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

7. 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

8. 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

9. 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

10. Chronic tests Usually same test species
For deriving longer term thresholds more reliably
Relevant endpoints growth or reproduction
Algae population growth
Daphnia reproduction (# of offspring)
Fish growth (biomass, length) or development
Rotifer population growth
Plant root growth
Molluscs growth (biomass, shell length)
Insect growth (biomass, length)
2016

11. Data Sources 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

12. 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

13. 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 non-standard test conditions, or in natural waters
2017

14. Summary Standardised species Standardised tests Standardised endpoints
Existing regulatory summaries
2017

15. 2016