The Office of Pollution Prevention and Toxics (OPPT) has developed several exposure assessment methods, databases, and predictive models to help in evaluating:
- what happens to chemicals when they are used and released to the environment; and
- how workers, the general public, consumers and the aquatic ecosystems may be exposed to chemicals.
These models and tools are intended to be used by scientists and engineers familiar with exposure assessment principles. They may be helpful when appropriate monitoring data are not available or need to be supplemented, and in:
The results of an exposure assessment are generally combined with a hazard assessment (potential for a chemical to cause adverse health or environmental effects). When combined, this information is used to evaluate whether there is a potential risk that requires Agency attention.
|Model||Consumer||General Population||Workers||Environmental||Download Availability|
|Dermal||Inhalation||Drinking Water||Fish Ingestion||Inhalation|
|*In addition to estimating worker exposures by the dermal and inhalation routes, ChemSTEER estimates environmental releases from industrial and commercial operations.|
|**Except for the the BioHCwin and KOAWIN models, EPI SuiteTM and the individual programs included in the software are owned by the U.S. Environmental Protection Agency and are protected by copyright throughout the world. EPI SuiteTM estimates physical/chemical properties and environmental fate and transport. EPI SuiteTM includes estimation programs for octanol-water partition coefficient (KOW), organic carbon-normalized partition coefficient for soil and sediment (KOC), atmospheric oxidation potential, Henry's Law constant, water solubility, melting point, boiling point, vapor pressure, octanol-air partition coefficient (KOA), sorption to aerosols, biodegradation, bioconcentration and bioaccumulation factors, hydrolysis, removal of chemicals in sewage treatment plants, and multimedia modeling.|
OPPT uses these tools in a tiered approach to exposure assessment. In order to find tools that are most appropriate for your needs, the exposure assessment tools have been grouped by Specialized Priority Setting Tools, Screening Level Tools, and Higher Tier Tools. The three categories of tools can be used together in a tiered approach to efficiently assess potential exposures to chemicals.
Priority Setting Tools use standardized criteria and exposure
models, and hazard information. These Tools are designed to:
- rapidly compare large numbers of chemicals by ranking them on the basis of relative risk and/or exposure using standardized criteria; and
- rank concerns broadly, and thus are not intended to provide detailed and accurate exposure assessments.
If you are evaluating a large number (hundreds, thousands) of chemicals for potential exposures, these tools can help in identifying chemicals and issues for further review. You can then focus and refine your assessment for those chemicals which rank higher based on the standardized criteria. Our Specialized Priority Setting Tools include:
- performs a systematic screening-level review of over 12,000 potential indoor pollution sources to identify high-priority product and material categories for further evaluation
- can also identify the products that have contained a specific chemical.
- identifies and screens clusters of chemicals ("use clusters") that are used to perform a particular task. A use cluster is a set of chemicals that may be substituted for one another in performing a given task
- identifies clusters of potential concern and provides an initial ranking of chemicals using human and environmental hazard and exposure data from a number of sources.
Screening Level Tools use readily available data and simple models, and are designed to:
- require minimal data entry;
- quickly screen release and exposure potential and "bin" chemicals by priority for future work; and
- estimate conservative (i.e., high or perhaps higher than actual) values of release and exposure.
If a screening level predicted exposure result is of potential concern, an appropriate next step would be to refine the assessment by collecting monitoring data and/or to use a more detailed model. Screening Level Tools include:
- estimates occupational inhalation and dermal exposure to a chemical during industrial and commercial manufacturing, processing, and use operations involving the chemical.
- estimates releases of a chemical to air, water, and land that are associated with industrial and commercial manufacturing, processing, and use of the chemical.
- provides screening-level estimates of the concentrations of chemicals released to air, surface water, landfills, and from consumer products.
- estimates provided are potential inhalation, dermal and ingestion dose rates resulting from these releases.
- modeled estimates of concentrations and doses are designed to reasonably overestimate exposures, for use in screening level assessment.
- estimates physical/chemical properties and environmental fate and transport, and includes estimation programs for octanol-water partition coefficient (KOW), organic carbon-normalized partition coefficient for soil and sediment (KOC), atmospheric oxidation potential, Henry's Law constant, water solubility, melting point, boiling point, vapor pressure, octanol-air partition coefficient (KOA), sorption to aerosols, biodegradation, bioconcentration and bioaccumulation factors, hydrolysis, removal of chemicals in sewage treatment plants, and multimedia modeling.
- estimates exposure and risk resulting from contact with inert ingredients in pesticides used in the home.
- requires user to input toxicity, formulation, and use information.
- calculates screening-level exposure and risk levels.
- estimates surface water chemical concentrations at drinking water utilities downstream from industrial facilities.
Higher Tier Tools use detailed data and more sophisticated models and are designed to:
- be closely tailored to (i.e., simulate) the exposure scenario of concern; and
- produce results with a higher level of accuracy.
These tools are complex and often require substantial, detailed data as input to the model. Where possible, data sets and default values are included with the model. A solid, technical background in science, chemistry, engineering or related disciplines is needed to use them appropriately. Higher tier tools include:
AMEM is a DOS-based software product developed in 1989 that uses a family of mathematical equations that address simple and complex scenarios for chemical migration. The more complex equations require more input data. Using the model, you may:
- Develop migration estimates, .
- Consider the effect of chemical partitioning between the polymer and the external phase,and .
- Consider the effect of mass transfer resistances in the external phase.
- brings together in one system several EPA environmental fate and transport models and some of the environmental data needed to run them.
- includes models and data for ambient air, surface water, soil, and ground water, and makes the models much easier to use than their stand-alone counterparts.
- has graphics and Geographical Information System (GIS) capabilities for displaying environmental modeling results.
- estimates average and peak indoor air concentrations of chemicals released from products or materials in houses, apartments, townhouses, or other residences. The data libraries contained in MCCEM are limited to residential settings. However, the model can be used to assess other indoor environments (e.g. schools, offices) if the user can supply the necessary inputs.
- estimates inhalation exposures to these chemicals, calculated as single day doses, chronic average daily doses, or lifetime average daily doses. (All dose estimates are potential doses; they do not account for actual absorption into the body.)
- estimates the potential exposure of consumers and workers to the chemicals emitted from wall paint which is applied using a roller or a brush.
The Economics, Exposure, and Technology Division of OPPT began developing these tools in the mid-1980s for use in our programs. Most of the tools have been peer reviewed. A few are scheduled for peer review upon completion of the ongoing updates. Where possible, EPA has compared the modeled results with monitoring data, but a thorough validation has not been conducted. EPA's comparisons have been favorable, but we encourage you to learn about the models, and evaluate them for your application before relying on modeled results. You may want to collect monitoring data as part of your evaluation. We encourage you to share your findings with us so we can continue to improve, refine and enhance these tools.