1. Thames Coromandel District Council
Governance Group Meeting – 20 June 2012
Moanataiari Sub-Division Stage 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 Moanataiari and 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.
May 23, 2019

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).
May 23, 2019

4. Stage 1 works - desired outcomes
Confirm hypothesis that Moanataiari soils 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.
May 23, 2019

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.
May 23, 2019

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 – 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).
May 23, 2019

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.
May 23, 2019

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).
May 23, 2019

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.
May 23, 2019

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).
May 23, 2019

11. Additional slides
May 23, 2019

12. NES SCS and HRA Hierarchy
Site Specific HRA
Source:
May 23, 2019

13. What value will we get from Tier 3 HRA?
Source:
May 23, 2019

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
May 23, 2019