RISC5

Overview

RISC5 is the premier software package for performing fate and transport modeling as well as human health and ecological risk assessments for contaminated sites. RISC5Ã‚Â’s distinguishing feature is its ability to perform backward risk calculations in addition to conventional forward risk calculations. Backward risk calculation in RISC5 computes a cleanup level for an input risk value. RISC5 also offers fate and transport models to estimate receptor point concentrations in both air and groundwater. RISC5 is the only RISC package to offer these features while using up to nine exposure pathways to estimate the potential for adverse human health impacts. Additional pathways and other non-human health impacts may be considered in future revisions of RISC.

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What's New in RISC5

Food web screening models for terrestrial and aquatic ecological risk assessments
Output tables and charts are now created directly in Excel
Particulate emission model
New plant uptake model (Trapp and Matthies, 1995)
RISC5 model chemical database has been expanded from 80 to ~120 chemicals
User can choose to use either reference concentrations and unit risk factors, or, inhalation reference doses and inhalation slope factors
All chemical toxicity values updated to be current with USEPA values
Now much easier to use chemical database to edit and generate summary tables of chemical properties
Mass balanced, depleting source, added to indoor and outdoor air models
References provided (online and in Excel tables) for all chemical and receptor parameters
New databases:
Ecological receptors and receptor-specific information
Mammalian and avian toxicity values
Worm and plant toxicity values
Soil and plant screening values
New human receptor profiles (including ones for additive receptor cases)
User can add new receptor and soil profiles and/or may customize default values
Sediment was added as a media of concern for human health risk (dermal contact and ingestion exposure pathways)

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Key Features of RISC5

RISC has an intuitive graphical interface; it was developed with teaching principles of risk assessment and fate and transport as a primary goal.
RISC allows for pathway, compound and receptor additivity both when calculating risk and in calculating clean-up levels.
All of the fate and transport models that start with a soil source can be used in the presence of phase-separated product (RaoultÃ‚Â’s Law is considered for all soil source models).
There is a transient vadose zone leaching model in RISC than can also be used to predict volatile emissions.
The soil source models consider mass balance (that is, they can model depleting sources).
The groundwater models are transient (i.e. they can handle time varying input).
RISC includes several exposure pathways not considered in other risk assessment software (to date) such as dermal exposure and inhalation during indoor showering, irrigation pathways and surface water and sediment intake pathways (both for humans and ecological receptors).
RISC has a large internationally derived surface water criteria and sediment criteria database for comparing modeled results with these environmental criteria.
A customizable chemical database with 82 chemicals
An Excel spreadsheet based on the RBCA algorithms that can be used to replicate the tiered RBCA process
A detailed user's manual with three in-depth example problems
The ability to determine risk-based TPH (total petroleum hydrocarbon) targets using the TPH fractions proposed by the U.S. Air Force led TPH Working Group
The ability to calculate additive risk due to multiple pathways, compounds and receptors (such as a resident exposed as both a child and an adult)
A Monte Carlo capability for probabilistic risk evaluation
Fate and transport models that distinguish between presence and absence of phase-separated product (NAPL) in the source zone

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Overview of Features

RISC5 allows the user to:

Choose chemicals of concern from a standard library of 128 chemicals; users may also add or delete chemicals from the library and alter the physical, chemical, and toxicological properties of each;
Perform calculations for two different human exposure scenarios (with up to seventeen exposure pathways each) simultaneously (e.g. calculations for both residential and industrial scenarios can be performed at the same time);
Determine cumulative risks from two different exposure scenarios, as might be the case when the user wants to sum the risks for the scenario where a resident is exposed during both childhood and adulthood;
Estimate exposure point water and air (both indoor and outdoor) concentrations using predictive chemical fate and transport models;
Allow for additivity of pathways and compounds for either a forward calculation of risk or back calculation of cleanup levels;
Print or save tables, charts, and figures.

New features that were included in Version 4.0 of RISC5 included:

Estimate human health risk from Ã‚Â“irrigation pathwaysÃ‚Â” for groundwater used outdoors but not supplying indoor uses;
Estimate human health risk from ingestion of vegetables grown in contaminated soil or irrigated with contaminated groundwater;
Use surface water mixing models to estimate potential impacts to surface water and sediments from contaminated groundwater;
Compare modeled surface water and sediment criteria with regulatory standards from around the world;
Consider degradation in two new vapor models; and
Calculate clean-up levels in soil and groundwater using MCLs (maximum concentration levels) or user-supplied concentrations in groundwater or surface water as targets (as opposed to risk-based calculations).

New features in Version 5 of RISC include

Tables and charts of model results are displayed directly in Excel for easier printing and incorporation in risk assessment reports;
Expanded chemical database, including the references for all chemical property values;
Saved project file names may exceed 8 characters;
A particulate emission (dust emissions) model has been added;
An updated vegetable uptake model based on Trapp and Mathis ();
For volatilization to outdoor air from soil, the soil source term is allowed to deplete over time, if desired; and
Default receptor profiles may be added, or modified, by the user.
Screening level food web model for evaluating ecological risk

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Expanded Data Sets in RISC5

Surface Water Criteria

United States Environment Protection Agency National Recommended Water Quality Criteria (2004)
United Kingdom Environmental Quality Standards (statutory and proposed)
Australia and New Zealand Environment and Conservation Council, Guidelines for Fresh & Marine Water Quality (October 2000)
European Commission Water Quality Objective
Canadian Council of Ministers for the Environment Canadian Environmental Quality Guidelines (December 2003)
TCEQ (Texas Commission on Environmental Quality) Guidance for Conducting Ecological Risk Assessment at Remediation Sites in Texas (December 2001)
MDEQ (Michigan Department of Environmental Quality) Rule 57 Water Quality Values (February 1, 2005)
GLWQI (Great Lakes Water Quality Initiative), Water Quality Guidance for the Great Lakes System 40 CFR 132 - Table 2 (March 23, 1997)
NYSDEC (New York State Department of Environmental Conservation) Ambient Water Quality Standards and Guidance Values - Table 1 (June 1998, updated January 1999, April 2000, & June 2004)
NCDENR (North Carolina Department of Environment & Natural Resources) 15A NCAC 2B or National Criteria per EPA (October 31, 2004)ODEQ (Oregon Department of Environmental Quality) Guidance for Ecological Risk Assessment Level II Screening Level Values (12/2001)
WA Ecology (Washington State Department of Ecology), WAC 173-201A Water Quality Standards for Surface Waters of the State of Washington (Updated 7/1/03)

Sediment Criteria

ANZECC - Australia and New Zealand Environment and Conservation Council, Guidelines for Fresh & Marine Water Quality (October 2000)
ARCS - Assessment and Remediation of Contaminated Sediments Programme
CCME - Canadian Council of Ministers of the Environment
FDEP - Florida Department of Environmental Protection
MDEP - Massachusetts Department of Environmental Protection, Technical Update: Freshwater Sediment Screening Benchmarks for Use Under the Massachusetts Contingency Plan (May 2002)
NOAA - National Oceanic and Atmospheric Administration
ODEQ - Oregon Department of Environmental Quality Guidance for Ecological Risk Assessment Level II Screening Level Values (12/2001)
ORNL - Oak Ridge National Laboratory, Tennessee
OSWER - Office of Solid Waste and Emergency Response
RIZA - Netherlands Institute for Inland Water Management and Waste Water Treatment
NAWQC - Derived by Equilibrium Partitioning from US EPA National Ambient Water Quality Criterion
WA Ecology - Washington State Department of Ecology, WAC 173-204-320 Table 1 (Standards apply to marine sediments located within Puget Sound as defined in WAC 173-204-200(19))

Soil and Plant Criteria (new)

Oregon - Oregon Department of Environmental Quality Guidance for Ecological Risk Assessment Level II Screening Level Values (12/2001)
Texas - TCEQ (Texas Commission on Environmental Quality) Guidance for Conducting Ecological Risk Assessment at Remediation Sites in Texas (12/2001)
Washington State - Washington State Department of Ecology Terrestrial Ecological Evaluation Process

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RISC5 Exposure Pathways Include

Ingestion of soil
Dermal contact with soil
Ingestion of groundwater
Dermal contact with groundwater
Inhalation in the shower
Inhalation of outdoor air
Inhalation of indoor air
Ingestion of surface water
Dermal contact with surface water

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RISC5 Fate and Transport Models Include

Johnson and Ettinger indoor air model
Vadose zone model
Saturated zone model
Volatilization from groundwater to indoor and outdoor air
Outdoor box model

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RISC5 System Requirements

A minimum of 15MB of free hard disk space
Windows XP/Vista/Windows 7,8,10 or higher
A Pentium class chip
1024 * 768 pixel monitor minimum
Excel 2003 or higher

RISC5 has been designed to run on an individual computer, that is, it can not be run over a network.

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Additional Features in RISC5

RISC5 has features that give it even greater flexibility in assessing risk for the following scenarios:

Irrigation pathways, i.e. water used for gardening but not for indoor usage
Vegetables grown in contaminated soil
Two new vapor models , where the vapors are allowed to biodegrade during transport through the unsaturated zone
Models for surface water and sediment contamination from impacted groundwater and direct comparison with relevant national standards for these media
The use of groundwater MCLs (maximum concentration levels) and surface water concentrations in addition to acceptable risk levels as the criteria for back-calculating clean-up targets
The ability to calculate a site-specific target level (SSTL) for a TPH mixture using the site-specific measured concentrations of the TPH fractions detected in the soil

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RISC5 Bugs Being Fixed and Work Arounds (Current Version 1.06.001)

This notice is providing you with information that you should be aware of concerning two bugs in the RISC5 software. There are also some cautions about the use of the Ã‚Â“Cumulative RiskÃ‚Â” back-calculation and the Ã‚Â“Saturated Soil ModelÃ‚Â”. (Note, the cautionary information applies to the use of any risk assessment model, not just RISC5.) Here is the information:

1. Bug in the Ã‚Â“Back-CalculationÃ‚Â” When Using Inhalation Pathways

The back-calculation has a bug in it when using inhalation pathways. This bug occurred several versions ago when we updated the code to follow the Ã‚Â“new USEPAÃ‚Â” approach to using inhalation reference concentrations (RfCs) and inhalation unit risk factors (URFs). The previous approach used toxicity parameters similar to the other pathways (dermal toxicity and oral toxicity).

So, the Ã‚Â“work-aroundÃ‚Â” for this bug, is to iterated on the concentration term when you need to perform a back-calculation for inhalation pathways. You change the source concentrations, calculate risk in the Ã‚Â“forwardÃ‚Â” mode and check the risk and hazard index. Based on the results of this, you can increase or decrease your source concentration terms until you reach your risk target. This should go very fast because the calculations are performed quickly.

This bug has been fixed in the code, however a new version has not been released because there is also a bug in the saturated soil model that is being worked on. When the saturated soil model is fixed, a new version will be released and you all will be notified and provided a new link to the updated version.

2. Bug in the Saturated Soil Model

If using the saturated soil model, you should always set the time step to 1 year. This bug is currently being fixed in the code and will be released in the next version.

3. A Caution When Using the Ã‚Â“Cumulative RiskÃ‚Â” Option (for any of the pathways)

Also, if any of your projects include a number of chemicals for which the total risk needs to reach some target (cumulative risk across all chemicals), I highly encourage you to do the Ã‚Â“back-calculationÃ‚Â” this way so you can control the range of source concentrations. This is a very important point. The reason is, if, for example, you have a high benzene concentration and a low benzo(a)pyrene (BaP) concentration and you are calculating risk from an indoor air model (or a leaching model), the BaP should not provide any significant risk since it is non-volatile and highly sorbs to soil. However, if you use the Ã‚Â“CumulativeÃ‚Â” risk option in Step 5, the RISC5 code assumes that all of the source concentrations will be reduced or increased using the same initial ratio of concentrations. So, if the benzene source concentration needs to be reduced 100-fold to meet the risk target, when using the Ã‚Â“CumulativeÃ‚Â” option, the BaP concentration will be reduced 100-fold as well. This is not good practice because the BaP was not contributing to risk in the first place so its source concentration does not need to be reduced in this case.

4. Saturated Soil Model Will Over-Estimate Source Depletion Time Usually

Because of the equations used in the saturated soil model when compared to Ã‚Â“real-lifeÃ‚Â”, the model should be used with a lot of caution, because it can over-estimate the flux of dissolved phase chemicals at the downgradient edge of the source.

This caution is also true for all of the vapor models that use soil source concentrations. One reason this happens is that the equilibrium partitioning equation is used to determine the both the dissolved phase concentration and the vapor phase concentration in the source usually over-estimates concentrations in those media (water and air) because the chemical sorbs more strongly to soil in Ã‚Â“real lifeÃ‚Â” than is predicted by the equilibrium partitioning equations in our fate and transport models (even with RaoultÃ‚Â’s Law applied).

It turns out (based on many technical articles based on measured data) that the equilibrium partitioning equation (which just uses the fraction organic carbon (Foc) to calculate sorption) tends to over-estimate the dissolved and vapor phases of the chemical concentrations when compared to measured data from the field. There are probably many reasons for this, one is that Foc is not the only cause for a chemical to sorb to soil (i.e. there are other causes of sorption and retardation). For example, the equilibrium partitioning equation assumes that all of the chemical sorbed to soil is Ã‚Â“availableÃ‚Â” to be put in the dissolved phase or vapor phase. However, the reality may be, that only a fraction of the chemical is adjacent to the pore water and air content and only that top layer can desorb at one time. In other words, it may not be a good idea to assume Ã‚Â“equilibrium partitioningÃ‚Â” exists all the time. However, currently this is the most commonly used predictor of sorption and desorption in any risk assessment models, so thatÃ‚Â’s what we have. It is just something to be aware of and it indicates why it is so important for the air models to get soil vapor concentrations rather than soil concentrations if possible.

The saturated soil model in RISC5 was developed for the case where there may be Light Non-Aqueous Product Liquid (LNAPL), or Ã‚Â“free-phase productÃ‚Â”, in the soil right at the water table. This model allows the user to enter a source concentration and then calculate concentrations that move downgradient in the groundwater. The model works by checking the soil concentration for each individual chemical and calculates if the concentration exceeds the chemicalÃ‚Â’s saturation limit. Note, it is very important to enter total TPH if your mixture is a petroleum product. So the code calculates the chemicalÃ‚Â’s dissolved phase concentration (using equilibrium partitioning) and then compares that dissolved concentration with the chemicalÃ‚Â’s effective solubility. (The RISC5 manual (Appendix B) explains how this is determined in a little more detail.)

The updated software will be sent out as soon as it is available.

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