Transcript Slide 1

Thames Coromandel District Council
Governance Group Meeting – 20 June 2012
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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Background sampling had limited value to the sub-division
contamination work – but may be necessary for NES compliance.
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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.
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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.
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Proposed HRA work programme
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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).
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Stage 1 works - desired outcomes
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Confirm hypothesis that Moanataiari soils have reduced bioavailability.
 Lab testing on soils (in vitro), no testing on animals (in vivo).
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Assist design of full scale bioavailability assessment (Stage 3b).
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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.
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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).
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Assist with prioritisation of remediation areas and assist with development of
management options.
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Bioavailability feasibility trial (as presented 2
May 2012)
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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.
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Bioavailability feasibility trial – results so far
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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).
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Stage 2 works – Preliminary HRA and gap
analysis
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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.
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Stage 3a – Detailed HRA
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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).
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Stage 3b work - full scale bioaccessibility assessment
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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.
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International Golder staff involved with project
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New Zealand staff:
 Simon Hunt – Project Director, Environmental Scientist, Risk
Assessor.
 Dr David Bull – Project Manager, Environmental Chemist.
 Carina Worsely – Project Administrator, Environmental Scientist.
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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).
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Additional slides
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NES SCS and HRA Hierarchy
NES SCS
Site Specific HRA
Source:
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What value will we get from Tier 3 HRA?
Source:
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Applicability to Moanataiari
NES applies
250 mg/kg arsenic – Risk Based
Remediation/Management generated by Phase 4
Assessment indicative only
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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