A practical approach to account for the bioavailability of metals Bruce Brown WCA Environment REPRESENTING Eurometaux November 25 th 2010

Slide 2 Metals EQSs are Evolving Existing methods based on total concentrations are poor predictors of potential environmental risk Need to monitor dissolved metals Biotic Ligand Models (BLMs) developed which predict toxicity extremely well BLMs appear complicated to implement – but are not!

Slide 3 Why bother to account for bioavailability? Many new metals EQSs are based on high bioavailability Wide scale failure of EQSs derived for metals if only considering face-value comparison with monitoring data. Enables resources and money to be focussed at those sites at real risk of harm

Slide 4 Perceived practical limitations when using biotic ligand models (BLMs) in the WFD Complexity of models Input hungry Resource intensity Practical difficulties How to use the outputs?

Slide 5 Solutions to the practical problems of implementing bioavailability in a regulatory frameworks Development of screening tools – only 3 inputs for Cu, Ni, Zn – DOC, pH and Ca) Tiered compliance assessment for metals Full automation possible within laboratory analytical system e.g. UK Outputs can be expressed as either bioavailable metal or site specific EQS

Slide 6 Screening Tools Comparison of Ni screening tool performance against NiBLM performance (all concentrations in µg dissolved Ni l -1 ) data from sites across the England and Wales (n ≈ 112).

Slide 7 Limited input data Output 1: Bioavailability-based PNEC Output 2: Site-specific risk characterization

Slide 8 The Tiered Approach

Slide 9

Slide 10 Nickel - Great Britain (n = 183) 1. Comparison with generic (100% bioavailable) EQS 2. Use of screening tool FAIL Pass Percentage pass rate = 97 % (n =122) (n = 61) (n =6) (n =116)

Slide 11 Nickel - France (n = 249) 1. Comparison with generic (100% bioavailable) EQS 2. Use of screening tool FAIL Pass Percentage pass rate = 95 % (n =29) (n = 220) (n =12) (n =17)

Slide 12 Nickel - Austria (n = 1779) 1. Comparison with generic (100% bioavailable) EQS 2. Use of screening tool FAIL Pass Percentage pass rate = 91 % (n =646) (n = 1133) (n =158) (n = 488)

Slide 13 Data Requirements Typically DOC, pH & Ca as minimum Potential need for guidance on best practice for producing DOC data? Can estimate DOC from dissolved Fe or UV absorbance but adds uncertainty

Slide 14 DOC Estimation by UV

Slide 15 Summary Accounting for metal bioavailability provides a robust metric by which to assess potential risks – and is linked to biology! Bioavailability can be applied within a tiered approach Simplified screening tools are available that: –Process large numbers of samples –Have only 3 inputs (in the case of Cu, Ni and Zn) –Fully automated Accounting for bioavailability does NOT present significant practical challenges Some changes to routine monitoring requirements probably needed e.g. Dissolved metals and DOC Implementation Guidance next year?