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RISC (Risk Assessment Model for Soil and Groundwater Applications) is relatively widely established in New Zealand among environmental risk assessors. RISC models the fate and transport of contaminants in steady state and transient modes. The moel is intuitive to use, and relatively simple.

The present version (3.0) evaluates human health risk only. However the updated RISC model will incorporate both aquatic and terrestrial ecological risk assessment by modelling contaminant concentrations at key receptor areas, and comparing these values with specific acceptance criteria. However, in developing the new version, the developers have highlighted particular difficulties associated with modelling the fate and transport of metals in soils.

Landcare Research and the model developers have discussed incorporating NZ-specific toxicity and soils data into the model.  

The main advantages with RISC are that the risk assessment approach (for human health risk assessment) is relatively widely accepted, the model is able to incorporate NZ specific data, and that investigators are relatively familiar with the software.

Review of RISC


The DSS software is produced by the American Petroleum Institute (API), and is used to estimate human exposure, carcinogenic risk, and non-carcinogenic effects from underground and above ground releases of petroleum products.

API's Risk and Exposure Assessment Decision Support System (DSS), Version 2.0, calculates carcinogenic risks to, and non-carcinogenic effects on, human receptors along six exposure pathways: 

  • ingestion of water
  • dermal absorption while bathing
  • inhalation while showering
  • inhalation of soil emissions
  • dermal contact with soil
  • soil ingestion

Risk assessments can be conducted for numerous petroleum hydrocarbons, petroleum product additives, chlorinated hydrocarbons, and metals.

As with Version 1.0, Version 2.0 of the DSS incorporates a number of fate and transport models for easy calculation of receptor point concentrations. Exposure, carcinogenic risk, and non-carcinogenic effects (hazard indices) are calculated using procedures consistent with those described in EPA guidance. DSS input data is via KnowledgePro for Windows, with output files from the DSS in EXCEL. Built-in EXCEL macros permit easy viewing and printing of risk assessment results in a number of convenient and illustrative formats.

New features incorporated into Version 2.0 of the DSS are designed to make the software easier to use, and to increase the modelling options available to the user. These new features include: 

  • New API VADSAT vadose zone/saturated zone contaminant fate and transport model
  • Upgraded SESOIL vadose zone model (allows modelling of additional soil layers)
  • Upgraded AT123D saturated zone model (allows user adjustment of time steps)
  • Improved AT123D source zone coordinate system
  • New module allows importation of concentration/time series data from external model runs

The database in Version 2.0 provides physical/chemical and toxicological property data for 86 petroleum hydrocarbons, petroleum product additives, chlorinated hydrocarbons, and metals. It can also be modified by the user..

The API-DSS software requires Microsoft EXCEL version 5.0 for Windows.

Review of API-DSS


CalTOX is a Multimedia Total Exposure Model for Hazardous Waste Sites developed by the California Department of Toxic Substances Control, Human and Ecological Risk Division.

It is Excel spreadsheet-based software that aids in assessing risk posed by some hazardous materials in the environment. A multimedia exposure assessment tool simulates leaching of contaminants from a waste disposal facility or contaminated site.

CalTOX predicts the concentrations of a contaminant at a given receptor and its principle application is for assessing human health risks. Its application to ecological risk assessment is somewhat limited.

The model incorporates a comprehensive database covering physical characteristics, and fate and transport data. Additional parameters can be added to databases, if required. BTEX and metals already included in the database.

The site characteristics database is limited at present, although further site data can be readily added. These site scenarios could be incorporated as New Zealand region-specific physical data, including soils data).

The principal limitation with the models is that terrestrial fauna are not included, and onsite terrestrial flora are modelled to calculate contaminant concentrations for human ingestion.

Review of CalTOX


SimpleBOX is developed by the National Institute of Public Health and the Environment (RIVM). It is a nested multi-media model that determines contaminant concentrations through the following compartments:

  • Air
  • Two water compartments
  • Sediment
  • Three soil compartments
  • Two vegetation compartments.

It uses contaminant concentrations as input and computes both steady state and time-dependent (transient) concentrations as outputs.

As for the CalTOX model, the principal limitation with the SimpleBOX model is that terrestrial and aquatic fauna are not incorporated into the model. However contaminant concentrations in water bodies and sediments can be evaluated against ecological benchmark criteria providing a limited ERA capability if required.

Review of SimpleBOX

Risk Based Corrective Action (RBCA)

The Risk Based Corrective Action (RBCA) process assesses subsurface contamination associated with hydrocarbon releases.

RBCA integrates USEPA risk assessment procedures, with site investigation and remedial actions to determine cost-effective measures for protection of human health and environmental resources. Its use as an integral part of the USEPA risk assessment approach has meant that some states have developed state-specific RBCA based models.

RBCA is regularly used for human health and qualitative aquatic ecological risk assessments only by leading and experienced risk assessment consultants in New Zealand. The model is intuitive to use and flexible in its applications to contaminated sites. Due to its greater complexity it takes more time to understand how it functions, particularly its transient modelling functions.

The supporting database is in EXCEL and can be easily modified or updated. However, NZ-specific data for example can not be 'hardwired' into the model and would need to be manually inputted.

Newly developed RBCA Chemical Releases software incorporates aquatic ecosystem risk assessment by modelling fate and transport of contaminants to, and within the water column, and these values may be compared to database benchmark values, or user specified input. The model also simulates the concentrations of contaminants in fish, in order to assess the human health risk from ingestion. Sediment concentrations are not included in the model.

The principal drawback with RBCA, in spite of its wide acceptance in the US for human health risk assessment, is that it is not widely used in New Zealand. In particular, we consider that regulatory agencies in NZ would not generally be familiar with this model.

The RBCA Tool Kit for Chemical Releases is a comprehensive modelling and risk assessment and characterisation software package for Tier 1 and Tier 2 RBCA evaluations for chemical release sites. The RBCA Tool Kit for Chemical Releases expands on Groundwater Services, Inc (GSI's) Tier 2 RBCA Spreadsheet System and meets the requirements of the ASTM Standard Guide for Risk-Based Corrective Action (ASTM, 1998). The Tool Kit combines contaminant transport models and risk assessment tools to calculate baseline risk levels and derive risk-based cleanup standards for a full array of soil, groundwater, surface water and air exposure pathways.

Review of RBCA

Refer to: http://www.gsi-net.com/


EcoFATE is an ecosystems-based environmental and ecological risk assessment model for chemical emissions from point and non-point sources in freshwater and marine aquatic ecosystems, including lakes, rivers and marine inlets.

EcoFATE is used to assess the cumulative impact of chemical inputs in terms of contaminant concentrations in water, sediment and biota of an entire ecosystem. It interprets these concentrations in terms of exceedance of environmental criteria and standards, potential for toxic effects in biota of the ecosystem and risks to human beings exposed to contaminated fish products or contaminated water

EcoFATE comprises a combination of an environmental fate, food-web bioaccumulation, toxicological hazard, and human health risk assessment models, that are integrated to directly relate chemical emissions to concentrations, toxic effects and human health risks. Each of the models is based on best available knowledge of the mechanisms of chemical distribution, toxicity and risk. The assessments can be done on a time-dependent and time-independent (ie. steady-state) basis.

The model is very easy to use and flexible and has the potential to be used in conjunction with risk assessment models focussing on onsite effects. The principal limitations with the EcoFATE model are the large amount of data required, and a thorough understanding of the complexities of fate and transport of contaminants in the aquatic environment is required to adequately use the model.

Review of EcoFATE


AQUARISK is a Tier 1 and Tier 2 ecological risk assessment software package under development at the Australian Nuclear Science and Technology Organisation (ANSTO).

A beta version of the model was presented at the Contaminated Site remediation conference held in Perth. The model presented was functional and relatively simple to use, however it may be limited in its application in that it covers aquatic ecological risk assessment only. Current ANZECC water quality guideline values are included in the model as default values. In a Tier 1 analysis, chemicals of potential concern are compared to guideline value, ie a hazard quotient approach.

In Tier 2 and 3 analyses, a log-normal distribution of the data is developed, and compared to dose response data (using an appropriate end point) to quantify specific ecological risk.

The major benefit of AQUARISK is that it will allow chemical speciation and hence bioavailability, and is therefore consistent with the draft revision of the ANZECC water quality guidelines (1998)

A terrestrial ERA component is not envisaged at this stage.

RAMAS Ecotoxicology

RAMAS Ecotoxicology is used to help undertake population-level ecological risk assessments for environmental contaminants. It carries out ecological risk assessments for two broad systems

  • structured single populations
  • food chains

The model is used to manage variability and uncertainty, express results as ecological risks. In each case, a model of population dynamics and toxicant kinetics is constructed using a Windows interface, and linked to bioassay data. Parameters can be specified as scalars, intervals or distributions, to take account of environmental variability and ignorance.

Monte Carlo simulations are then used to predict future population trajectories, and calculate the risk of adverse events such as extinctions or algal blooms.

Review of RAMAS

Refer to: http://www.ramas.com/


RIP is a PC-based software program developed by Golder Associates. It probabilistically simulates the release, transport, and fate of contaminants within engineered and/or natural environmental systems.

Although originally developed to simulate the long-term performance of radioactive waste disposal facilities, the software can be readily applied to more commonly encountered environmental problems, such as contaminant release from landfills and/or hazardous waste sites, and contaminant fate and transport in wetlands, lakes and other complex ecosystems. The software can also be used to simulate complex fate and transport processes within biological systems (e.g., physiologically-based pharmacokinetic modelling).

The transport pathways used in the model can consist of multiple transport and storage media (e.g., groundwater, surface water, air, soil), and both advective and diffusive transport mechanisms can be directly simulated. Transport processes incorporate solubility constraints and partitioning of contaminants between the media present in the system, and can include the effects of complex chemical reactions and decay processes.

It can also model biological transport of contaminants, and like physical transport pathways, is can include any number of transport and storage media (e.g., blood, tissue) which can be linked by a variety of transport mechanisms.

The output produced by RIP consists of predicted contaminant release rates from defined sources and transport pathways, and predicted concentrations within environmental media throughout the system (e.g., groundwater, soil, air, blood). If desired, concentrations in environmental media can be converted to doses and/or health risks by assigning appropriate conversion factors.

An important requirement for using the RIP is that the user has a clear understanding of the features, processes, and events controlling the behaviour of the system to be modelled. The modeller must have a good understanding of the fundamentals of contaminant transport modelling. The RIP model can be run in a deterministic manner, or can represent uncertainty through the use of probability distributions. However the user must have at least a basic understanding of the representation and propagation of uncertainty as a probability distribution.

Refer to: http://www.golder.com/rip/default.htm

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Page last updated: 01 May 2007

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