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Risk Assessment Methodologies

Ecotoxicity testing protocols 

Ecotoxicity results

Contaminant mobility

Soil property data


Toxicity databases

RA methodologies

Document resources


Problem Identification

Receptor Characterisation

Exposure Assessment

Toxicity Assessment

Risk Characterisation


A broad but established risk assessment methodology is becoming established within the international environmental regulatory community. This methodology applies to ecological risk assessment as well as human health risk assessment. The key assessment components include problem identification, receptor characterisation, toxicity assessment, exposure assessment and risk characterisation. Most methods that are promulgated regard risk management as a separate process. In reality this step can not be divorced from risk assessment.

The following sections describe the ecological risk assessment (ERA) methodologies in four different countries.

Most approaches promote increasing levels of investigation separated by decision steps to evaluate the need for further investigation in light of the cost of remedial actions, assessed ecological impacts, the costs of further investigation, and the regulatory environment.

Benchmark values and underlying ecotoxicolgical criteria associated with this ERA documentation are becoming increasingly available.  The correct interpretation of these data for New Zealand settings requires specialist knowledge.

The field of ERA within the context of site contamination is still developing and there is also much ecological research expertise that can be brought to bear on this subject. However, at the moment, this expertise is only partially used and may be largely unavailable to most site investigators.

New Zealand  

New Zealand's approach to managing site contamination is predicated on the basis of managing the actual and potential adverse effects on the environment, through the Resource Management Act (RMA) 1991.

Since the implementation of the RMA, this has been confirmed through the Government's E2010 strategy and through specific guidance on the management of contaminated sites.

The New Zealand Government has a policy goal of cleaning up contaminated sites to reduce the risk to the environment, people and the economy (E2010, 1994). The approach adopted by the Government is 'promoting an assessment of contaminated sites on the basis of risk, and removing barriers to clean-up (through developing disposal techniques, and establishing a liability framework)' (E2010 1994).

This broad approach is supported through the development of non-statutory guidelines for the management of site contamination:

Lately, however, guideline development has focused on the development of sector-based guidelines for the assessment and management of contaminated sites through:

These documents provide some guidance for risk assessment of sites contaminated by BTEX and CCA. However, they focus on protecting human health within a variety of land-use settings, with little emphasis placed on ecological risk assessment.

Human health criteria for BTEX and CCA for a variety of land- and human-use scenarios are provided in the sector-based guidance. The reader is referred to ANZECC Water Quality Guidelines (1992) to obtain criteria for the protection of aquatic ecosystems. However, no comprehensive terrestrial ecotoxicological or phytotoxicological criteria are established in these guidelines.

Recent Developments

In October 2000, the Australia and New Zealand Environment Conservation Council and the Agriculture and Resource Management Council of Australia and New Zealand produced the Australian and New Zealand Guidelines for Fresh and Marine Water Quality. These guidelines update the 1992 ANZECC Water Quality Guidelines and provide a set of tools for assessing and managing ambient water quality in natural and semi-natural water resources. The guidelines are not mandatory but provide recommendations to guide practice and formulate policy. 

The Ministry for the Environment is currently assessing the effects of organochlorine compounds on New Zealand ecosystems. At the time of this review the results of this assessment were not available, and may only be peripherally relevant to this project.

Useful background information related to the ecotoxicological effects of chlorinated compounds can be found in the following document:

  • Ecotoxicological Risk Assessment of the Chlorinated Organic Chemicals, edited by Carey J, et al (1998). 

This document provides a summary of a SETAC workshop undertaken to assess and characterise risk, to identify risk management options, and to develop strategies that address the ecotoxicology of chlorinated organic chemicals.

Ecological soil screening levels (EcoSSL) are presently being developed by the USEPA to provide values that may be used for initial assessment of contaminated soils.


In early 1999, the National Environment Protection Council released a National Environmental Protection Measure (NEPM) and Impact Statement for the Assessment of Site Contamination. This work followed the efforts of the Australia New Zealand Environment and Conservation Council (ANZECC) and the National Health and Medical Research Council (NHMRC) Contaminated Sites Technical Review Committee that reviewed the ANZECC Guidelines described above.

The NEPM document aims to update and formalise the ANZECC/NHMRC guidelines for the assessment and management of contaminated sites, in relation to policy and technical aspects of soil contamination. The NEPM is broken into several component guidelines, including:

  • investigation levels for soil and groundwater,
  • data collection, sample design and reporting of data,
  • laboratory analysis of potentially contaminated soils,
  • health risk assessment methodology,
  • ecological risk assessment,
  • assessment of groundwater contamination,
  • health-based investigation levels,
  • community consultation and risk communication,
  • protection of health and the environment during assessment of site contamination, and
  • competencies and acceptance of contaminated land auditors and related professionals.

Overall, the NEPM proposes a wide-ranging approach to contaminated site management. In particular, the guideline for ecological risk assessment describes the framework for ecological risk assessment for chemically contaminated soils. It outlines a three-tiered level of assessment, which is consistent in its broadest form with other proposed methodologies. It provides comprehensive technical guidance for initiating and conducting an ecological risk assessment, the significance and derivation of generic soil and site-specific ecological values, data requirements, and risk management outcomes. 

Its major limitation, however, is that it focuses primarily on species living on or visiting the site being exposed to contaminated soil. Off-site impacts are not discussed in any detail. 

United States


The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) 1980 and its subsequent amendments require the USEPA to protect public health and welfare and the environment from the release of any contaminant. As a part of its responsibilities, the USEPA developed the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). The NCP calls for the identification and mitigation of environmental impacts, and for the selection of remedial actions to protect the environment.

As a result of this regulatory framework, the USEPA began to develop ERA from the existing methods available at that time for assessing risk to human health.

Key reports released by the USEPA on ERA include

The Risk Assessment Guidance for Superfund highlights the baseline risk assessment, both human health and environmental (Part A), refinement of preliminary remediation goals (Part B), and the evaluation of remedial alternatives (Part C).

The document was designed to assist managers, site engineers, risk assessors, and others to develop remediation goals that satisfy the 'threshold criteria' of the NCP, to protect human health and the environment, and to develop and use risk information to evaluate remedial alternatives during the feasibility study.

The Ecological Risk Assessment Guidance for Superfund (1997) aims to develop defensible and appropriately scaled site-specific ecological risk assessments for the Superfund programme. It is a comprehensive guidance document aimed at regulatory authorities and risk assessors and contains a full description of the risk assessment process using several examples to demonstrate this process. It contains extensive checklists for ecological sampling and guidance on conducting literature reviews, statistical uncertainty, biological sampling methods, and data analysis. However, at the time of this evaluation it was due for review, in light of the recent publication of the updated guidelines for ERA.

The Guidelines for Ecological Risk Assessment (1998) supersede the 1992 guidelines. They expand upon previous risk assessment guidance, and are designed to help improve the quality of ecological risk assessments at the USEPA, while increasing the consistency of assessments among the Agency's offices and regions.

The 1998 guidelines describe the process of ERA, from problem formulation through to risk characterisation and risk management, in a comprehensive manner.

It should serve as a key reference document for any site investigator wishing to undertake an ecological risk assessment. However, site investigators, site managers and regulators should remain aware of the regulatory environment from which this guideline has been prepared.

In conjunction with the guidance documents, the USEPA has also made available a considerable body of data on exposure factors and toxicology.

The Standard Default Exposure Factors; Supplemental Guidance to Human Health Evaluation Manual 1991 which supplements the Risk Assessment Guidance for Superfund: Human Health Evaluation Manual (Part A, Volume I, 1989) was developed to reduce unwarranted variability in the exposure assumptions used to characterise potentially exposed populations in the baseline risk assessment. The document includes two attachments that cover activity-specific inhalation rates and estimate adult soil ingestion in the commercial/industrial setting.

Considerable additional work has also been undertaken at the Regional level of the USEPA. Key documents from these regions include

These documents generally follow a similar approach to those developed by the USEPA, with some variations to allow for regional issues of concern.

In summary, the work undertaken in developing and refining methodologies for ERA by the USEPA and its regional counterparts has resulted in a significant body of relevant literature and the availability of a substantial quantity of ecotoxicological data to support risk assessments. The guidance documents have been specifically produced to support US legislation, and this is reflected particularly in the level of specifications for how the ERA shall be undertaken and reported on. This should be taken into account when using these guidelines within New Zealand.

Oak Ridge National Laboratory

The Oak Ridge National Laboratory (ORNL) is a multi-programme science and technology laboratory operated for the US Department of Energy by Lockheed Martin Energy Research Corporation. It has undertaken considerable research into ERA and has developed a broad portfolio of guidance documents and ecological screening benchmarks to assist with ecological risk assessments.

Outputs of this programme include

  • a report describing the technical basis, appropriate application and acceptance of ecological screening benchmarks, in particular the ORNL benchmarks
  • toxicological screening benchmark reports containing chemical-specific information covering aquatic and terrestrial fauna and flora, sediment-associated organisms; and soil invertebrates and microbial processes
  • a series of guidance documents covering a range of issues including guidance on performing ecological risk assessments, a range of exposure models, data quality objectives, and guidance on developing preliminary remediation goals (PRGs)
  • examples of completed ecological risk assessments.

The ORNL ecological risk assessment package has strong international credibility and is referred to in some USEPA risk assessment documents. It provides comprehensive technical guidance in identifying contaminants, media, and receptors that may be at risk and may require further investigations. It is aimed at intermediate- to advanced-level practitioners carrying out Phase I site investigations and does not address wider risk management issues.

Benchmark criteria have been developed for a wide range of inorganic and organic contaminants of concern, including metals, organochlorines, and hydrocarbons.

Many of the species for which benchmark criteria are available are not relevant to New Zealand ecosystems. However, the methodology for developing the screening benchmarks could be applied in developing site-specific or New Zealand-specific criteria.


Environment Canada

As a part of its National Contaminated Sites Remediation Programme, Environment Canada has produced a Framework for Ecological Risk Assessment at Contaminated Sites in Canada (1994).

This report is a review of ERA methods and recommends an approach to promote consistency in site assessment and remediation in Canada. The key components of the assessment are: exposure assessment, receptor characterisation, hazard assessment, and risk characterisation.

A tiered approach is considered

  • Level I - screening and characterisation by simple qualitative or comparative methods
  • Level II - derivation of semi-quantitative data including environmental methods and models, with an increased emphasis on data collection and priority issues determined in the Level I assessment
  • Level III - site-specific data and predictive modelling to derive quantitative information on complex ecosystem responses. Chronic effects, interactions between chemicals, and ecosystem-level studies are encompassed in this assessment.

The tiered approach methodology is comprehensively described and broadly follows processes used in human health risk assessment and adopted for ERA. Data requirements of each phase are clearly defined by way of tables and flow charts.

The system is compatible with US tiered approaches and is particularly useful in that many of the regulatory factors that pervade US literature are not as dominant in this report. It is likely to be useful as a base document for site investigators in New Zealand, provided that the Canadian regulatory requirements are recognised.

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