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Thames Coromandel District Council

Governance Group Meeting – 20 June 2012. Thames Coromandel District Council. Moanataiari Sub-Division Stage 3 - Human Health Risk Assessment and Bioavailability Feasibility Trial. Key comments from 2 May 2012 Governance Meeting.

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Thames Coromandel District Council

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  1. Governance Group Meeting – 20 June 2012 Thames Coromandel District Council MoanataiariSub-DivisionStage 3 - Human Health Risk Assessment and Bioavailability Feasibility Trial

  2. Key comments from 2 May 2012 Governance Meeting • Background sampling had limited value to the sub-division contamination work – but may be necessary for NES compliance. • Site specific human risk assessment (HRA) provides a way of assessing the current and future scenarios for Moanataiariand will assist in generation of remediation criteria and management/remediation options. • A bioavailability feasibility assessment will assist in understanding the risk from the oral ingestion exposure route – particularly for pica child ingestion of soil. • If trial indicates that bioavailability is likely to be high (80-100%), then a site specific HRA likely to be close to NES SCS. If the indicative bioavailability is low (10-20%), this will increase the risk threshold and therefore derived remediation criteria will be higher than NES.

  3. Proposed HRA work programme • Current thinking that the lower levels of contamination recorded in west and central areas of sub-division may be safe and pose no risk – but need thorough/detailed HRA to support this hypothesis. • Develop revised soil acceptance criteria for sub-division (based on HRA). • HRA to dovetail with/assist T&T mitigation/remedial option planning and development work programme. • Proposed HRA work programme to be undertaken in a stepwise manner (ensure cost effectiveness) and meet TCDC timelines. • Stage 1 Works - Bioavailability Feasibility Study. • Stage 2 - Preliminary Human Health Risk Assessment and Gap Analysis. • Stage 3a - Detailed Human Health Risk Assessment. • Stage 3b - Detailed Bioavailability Study (if favourable results from Stage 1 works).

  4. Stage 1 works - desired outcomes • Confirm hypothesis that Moanataiarisoils have reduced bioavailability. • Lab testing on soils (in vitro), no testing on animals (in vivo). • Assist design of full scale bioavailability assessment (Stage 3b). • Provision of public health information – high (>80 %) level of bioavailability recorded (which is counter to current theoretical assumption) provide information to assist with immediate management of public health risks. • Assist Stage 2 and 3 HRA work – understanding whether soil particle size is a critical exposure factor because of possible enrichment in the finer soil fraction (or vice versa) – i.e. total metal concentrations (soils that pass a 2 mm sieve) versus metal concentrations for the finer soils (less than 250 µm). • Assist with prioritisation of remediation areas and assist with development of management options.

  5. Bioavailability feasibility trial (as presented 2 May 2012) • What the feasibility trial entails. • Review PDP and T&T sampling work. • Select 20 T&T samples across the subdivision for bioavailability assessment. • Analyse 20 screened soil samples for bioavailability assessment of arsenic and lead. Additional metals analysis (manganese, iron, calcium, phosphorous) and soil pH will assist interpretation. • If results favourable, suggest a more in depth bioavailability assessment for use in HRA. • NES SCS for arsenic and lead will be re-calculated using bioavailability values to demonstrate how this influences the risk criteria. • Provide value for money as it could be applied across wider Thames area.

  6. Bioavailability feasibility trial – results so far • Soils selected and prepared in the lab (Hills in Hamilton). • < 2 mm soils analysed for lead, arsenic, manganese, iron, phosphorous and pH. Initial results:- • Lead 10.5 – 1,420 mg/kg • Arsenic 26 – 670 mg/kg • Manganese 250 – 3,000 mg/kg • Iron 16,400 – 61,000 mg/kg • Phosphorous 124 – 2,200 mg/kg • pH 3.5 – 7.5 • < 250 µm soils currently undergoing bioaccessibility extraction and lead and arsenic analysis. • Initial results should be available from the lab 22 June 2012. • Draft report available 6 July 2012 (or sooner).

  7. Stage 2 works – Preliminary HRA and gap analysis • Develop a HRA conceptual site model (CSM) – utilise T&T property audits etc. • Identify key contaminant exposure routes. • Likely – soil ingestion, vegetable/fruit consumption. • Possible – indoor dust, roof water, others? • Review T&T contamination data QA/QC and spatial distribution – verify/confirm acceptable for HRA. • Review NES SCS exposure assessment criteria/parameters – consider options to vary input parameters and substitute with site specific criteria (some of these issue will test policy issues) – such as consumption of home grown vegetables, human exposure parameters etc. • Identify gaps in current data – such as possible indoor dust testing, vegetable/fruit testing, additional soils testing (to address/firm up spatial distribution), roof tank water testing. • Generate initial / revised preliminary soil acceptance criteria for residential (adult/child) and maintenance worker land uses – based on HRA CSM, T&T contamination data, Stage 1 bioavailability data, documented/literature dust/vegetable/fruit concentrations, etc. • Consider sensitivity of input parameters. • Aim to complete work by 27 July 2012 – meet TCDC timelines.

  8. Stage 3a – Detailed HRA • Undertake thorough HRA to support the proposed management approach - needs to be robust and able to under go significant peer review / scrutiny. • Assume residential land use (adult and child risk criteria) and maintenance worker. • Undertake additional works identified in Stage 2 gap analysis to support Stage 3a HRA. • Undertake detailed bioavailability study (Stage 3b) to support Stage 3a works – if appropriate (based on Stage 1 works).

  9. Stage 3b work - full scale bioaccessibility assessment • Additional soil sampling and analysis of sub-division soils. • Arsenic, lead, pH, iron, total organic carbon, cation exchange capacity, manganese, calcium and phosphorus, particle size distribution. • Working through where the lab testing should be performed – balancing cost, NZ focus / up skilling of local lab / QA & QC issues. • Up skill NZ lab and bring in certified reference material to improve QA/QC. • University of South Australia (local, but expensive). • North American labs (cheaper than Australia, but significant distance to ship samples, good QA/QC). • Undertake some analysis in NZ and ship < 250 µm sample portion to North America for testing.

  10. International Golder staff involved with project • New Zealand staff: • Simon Hunt – Project Director, Environmental Scientist, Risk Assessor. • Dr David Bull – Project Manager, Environmental Chemist. • Carina Worsely – Project Administrator, Environmental Scientist. • International staff: • Toxicologists – Dr. Peter Di Marco and Len Turczynowicz (Australia). • Bioavailaibility Specialists – Sue Robinson (USA) and Thersa Repuso-Subang (Canada). • Risk Assessors – Dr. Carolyn Brumley and Sarah McKiernan (Australia).

  11. Additional slides

  12. NES SCS and HRA Hierarchy NES SCS Site Specific HRA Source:

  13. What value will we get from Tier 3 HRA? Source:

  14. Applicability to Moanataiari 250 mg/kg arsenic – Risk Based Remediation/Management generated by Phase 4 Assessment indicative only NES applies 100 mg/kg arsenic – NES Compliance Point (derived background for Moanataiari) indicative only NES doesn’t apply 20 mg/kg arsenic – NES Residential SCS 5 mg/kg – Waikato arsenic background mean from MfE (2011) Methodology for Deriving Standards for Contaminants in Soil, Appendix 6

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