A Health Investigation Level (HIL) refers to the level at which a substance’s concentration will trigger further investigation and evaluation to determine the risk to public health. HILs are used in assessments of existing contamination and are intended to prompt an appropriate site-specific assessment when they are exceeded.
HILs are specified in the National Environment Protection Measure (NEPM) (Assessment of Site Contamination).
What is the NEPM (Assessment of Site Contamination)? The National Environment Protection Measure (NEPM) 1999 was developed under the Commonwealth National Environmental Protection Council Act 1994. The Act established the National Environment Protection Council (NEPC) to ensure that people enjoy the same level of protection from pollution, wherever they live in Australia. The NEPC makes measures in writing, known as national environment protection measures. The measure for assessing site contamination provides a nationally consistent approach which ensures sound environmental management practices by regulators, site assessors, environmental auditors, landowners, developers and industry. The NEPM is available from the NEPC via www.nepc.gov.au.
Why do auditors adjust an HIL? It is very common for HILs to be adjusted to make them relevant for the situation to which they are being applied.
What occurred in relation to 50 Fraser St’s HIL? The recently completed independent environmental audit for 50 Fraser St, Diamond Creek included a Human Health Risk Assessment (HHRA), which used the NEPM process to adjust the HIL for arsenic, drawing on site-specific information. This information includes the type (species) of arsenic present, the future use of the site (such as low density residential), and an assessment of arsenic’s oral bioavailability (the percentage absorbed by the body when ingested).
Based on the auditor’s assessment, the HIL for arsenic for low density residential properties in proximity to 50 Fraser Street Diamond Creek has been adjusted from 100 milligrams per kilogram (mg/kg) to 400 mg/kg.
This means that an arsenic reading in Diamond Creek below 400 mg/kg is not of concern for human health. This level considers the most vulnerable members of the community, children and elderly, and gives protection for long term or chronic exposure.
This adjustment as part of the HHRA has been verified by the environmental auditor and reviewed by EPA.