Responding to Soil Contamination in the Moanataiari Subdivision

And when the NES does and does not apply

May 2012

Messages of this presentation:

• Managing human health risk remains the key issue• Until triggered, the NES does not apply to ongoing

lawfully established activities, regardless of the soil contamination until there is a change in use, subdivision, earthworks

• To more valuably inform of risk and appropriate response, health risk assessment work is required

• In the meantime, health risk is being managed within the guidelines issued by the MoH and WDHB

What is the NES?• A regulation under the Resource Management Act,

1991• National Environmental Standard for Assessing and

Managing Contaminants in Soil to Protect Human Health (NES)– NZ Regulation in force since 1 January 2012– Purpose – a planning tool to ensure:

• Identification and assessment of land affected by contaminated soil• Appropriate assessment of contaminated land at the time of land being developed,

subdivided, or disturbed; and,• If necessary, remediation or contaminant containment to make land safe for human use

– Reflects NZ government policy

on acceptable increased risk• Acceptable risk level is 1 in 100,000

– Developed Soil Contaminant Standards (SCS) for priority contaminants

How does the NES apply to Moanataiari?

• The NES– Only triggered if the land is subdivided, developed

or disturbed– Unless triggered, cannot require remediation to

be undertaken, even if the land is unfit for its current use

– Once triggered, consents may be required to undertake activities/land use

Acceptable Risk Level

• Contaminants in soil can have adverse effects on human health

• Based on a number of factors, including the reference health standard:– Estimated daily amount that can be taken into the

body without exceeding an acceptable risk level• The arsenic concentration in soil for a

standard residential scenario that gives rise to this dose is 20 mg/kg (SCS for arsenic)

What is a Soil Contaminant Standard

• The SCS is a New Zealand risk based standard to protect human health that: (NES or otherwise) – Serves to indicate whether there is a potential risk to human

health– When exceeded, serves as conservative clean-up targets for

many situations, i.e., where further investigation or site-specific risk assessment is not warranted or economic

– Informs on-site management actions to address human health risk issues

– Triggers further investigation to better assess the risk and/or determine site-specific criteria as a Tier 2 assessment

How was arsenic SCS derived?• Arsenic is considered a non-threshold contaminant

(cancer causing)• Up to date methodology used that is not inconsistent

with other countries• Uses New Zealand derived criteria:

SCS (Soil ingestion) = RHS x ED x 106

IR adj x EFWhere:RHS = Reference health standard (mg/kg BW/day)ED = Life time exposure (days) IR adj = Age adjusted ingestion rate (mg/day) EF = Exposure frequency (days/year)

Arsenic SCS Assumptions

• Assumptions– Contaminants are 100% bioavailable • Only a (as yet unknown) fraction of arsenic in the soil

will be absorbed and able to harm health

– 10% produce consumption for standard residential scenario• Not all households grow their own food

Current situation

• The detailed site investigations on individual properties completed

• Total arsenic and lead concentrations in the soils on Moanataiari exceed the SCS

• These soils also exceed soil guideline values for thallium

• The NES has not been triggered for these properties

What's next?• Undertake a Tier 2 Health Risk Assessment

– The criteria that can be altered are limited – Test the assumptions, especially bioavailability

• Trial underway

– Develop site specific soil values for Moanataiari

• Long term management of risks to human health– Consider the community’s expectations– Understand options to remediate/mitigate or manage the risks

to health– Determine methods for monitoring and maintaining any health

protection measures.

END

References• Resource Management (National Environmental Standard for Assessing

and Managing Contaminants in Soil to Protect Human Health) Regulations 2011 (http://www.legislation.govt.nz/regulation/public/2011/0361/latest/DLM4052228.html?search=ts_regulation_contaminants_resel&p=1&sr=1)

• Users' Guide: National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health (http://www.mfe.govt.nz/publications/rma/users-guide-nes-for-assessing-managing-contaminants-in-soil/)

• Methodology for Deriving Standards for Contaminants in Soil to Protect Human Health (http://www.mfe.govt.nz/publications/hazardous/deriving-standards-for-contaminants-in-soil/index.html)

• Toxicological Intake Values for Priority Contaminants in Soil (http://www.mfe.govt.nz/publications/hazardous/toxicological-intake-values-for-priority-contaminants-in-soil/index.html)