Ecological Risk Assessment
Frequently Asked Questions
- Is there a "standard set" of screening values used in Region 3?
- The "Region 3 BTAG Screening Benchmarks" table does not provide a value for a compound at my site. Can I develop an alternate value?
- What values do I use to screen / evaluate exposure via food chain exposure? Does Region 3 have screening values that address this route of exposure?
- Which compounds should be considered in the food chain exposure evaluation?
Yes. The "Region 3 BTAG Screening Benchmark" tables provide media-specific sets of ecotoxicological benchmarks that should be used in developing a screening level assessment. These guidelines are to be used to screen exposure through routes other than food chain exposure. The 1995 Region 3 BTAG table is currently being updated and revised benchmarks for freshwater and freshwater sediments are now available. Additional media-specific tables will be posted on this website as they become available. Until the updated tables are available, the values found in the 1995 Region 3 BTAG Table should be utilized. Where appropriate, updated values that may be available in subsequent releases of the EPA Ecological Soil Screening Levels, and the NOAA SQuiRT values should be used in place of the values cited in the 1995 Region 3 BTAG table.
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2. The "Region 3 BTAG Screening Benchmarks" tables do not provide a value for a compound at my site. Can I develop an alternate value?
In general, when a BTAG value is not available, we recommend carrying a compound through the screening level assessment and providing justification for dropping or retaining the compound for further evaluation in the ecotoxicological and fate and transport discussions that will be provided in the baseline problem formulation.
As approved by BTAG, alternate values may be considered if they are from one of the following sources and the source of the value is clearly cited:
- EPA's Ecological Soil Screening Levels
- EPA EcoTox Thresholds;
- NOAA SQuiRT values (current values may also be used to update the historical ER-L values previously used as a BTAG value);
- CCME (Canadian Council of Ministers of the Environment) Canadian Environmental Quality Guidelines; and,
- Oak Ridge National Laboratory Screening Benchmarks (appropriate safety factors must be applied to values not based on "no effects" data).
The revised Region 3 BTAG Screening Benchmarks for Freshwater and Freshwater Sediment were based on the most recent ecotoxicological data available at the time of their compilation. These values will be routinely reviewed and revised. The absence of a value in the tables indicates that toxicity data were lacking or existing values were not suitable. Therefore, alternate screening values will not be considered for chemicals detected in these media when a BTAG value is not provided. These compounds should be appropriately identified and addressed in the baseline problem formulation.
Alternate values from other sources will be considered when the following criteria have been met:
- a written justification supporting the use of the value is provided and approved by BTAG prior to the development and submission of the Screening Level Ecological Risk Assessment;
- the value is based on a NOAEL;
- citations for the studies that were evaluated during the development process are provided; and,
- copies of the key references (e.g., journal article, unpublished research, etc.) supporting the use of the value are provided.
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3. What values do I use to screen / evaluate exposure via food chain exposure? Does Region 3 have screening values that address this route of exposure?
The Region 3 BTAG has not developed food chain exposure screening values. NOAEL-based values must be obtained from the literature for the receptor species (or its surrogate) selected for evaluation in the screening level assessment. When applicable and available, EPA's Ecological Soil Screening Levels for food chain exposure should be utilized. Adequate documentation for the use and applicability of each value must be provided. The risk assessor should consult with BTAG prior to initiating the development of these values and discuss the format for the presentation of the data that is to be evaluated and considered.
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All bioaccumulative compounds need to be assessed in the food chain exposure evaluation. The list of compounds that the Region III BTAG considers to be bioaccumulative is on Table 4-2 in Bioaccumulative Testing and Interpretation for the Purpose of Sediment Quality Assessment, Status and Needs, EPA-823-R-00-001, February 2000. If a compound found on your site is on this list, it must be considered in the food chain evaluation.
The need to include other compounds should be evaluated using the site conceptual model to identify complete exposure pathways to higher trophic level receptors. For compounds expected to be present in prey, toxicity data should be reviewed to determine if higher trophic level species are sensitive to these compounds.
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