DEVELOPMENT OF A CONSISTENT MODEL FOR ECOLOGICAL RISK ASSESSMENT IN TEXAS: The Protective Concentration Level Calculator
Heim, Bradley L
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Ecological risk assessments (ERAs) for contaminated sites can be lengthy, resource-intensive, and prone to subjective interpretation. The Texas Commission on Environmental Quality (TCEQ) periodically publishes the RG-263 document which is known as the Ecological Risk Assessment Guidance or ERAG, but is entitled “Conducting Ecological Risk Assessments at Remediation Sites in Texas”. The ERAG also discusses the interactions of the ERA process with the ecological services analysis process and the role that the Natural Resource Trustee agencies play in both under Texas regulation 30 TAC §7.124. The guidance outlines a three tiered process: Tier 1 Exclusion Tier II Screening Level ERA Tier III Baseline ERA The ecological protective concentration level (PCL) calculator and supporting database were intended to provide a consistent, scientifically derived and legally defensible methodology that will streamline the processes of development and review of ecological risk assessments. The result is a web-based user interactive toxicological database capable of calculating screening levels (Step 6 ERAG) and protective concentration levels (PCLs; Step 7 ERAG) for chemicals of concern (COCs) for over 80 indicator species in seven diverse habitats of Texas. The web-based tool is also capable of supporting the risk assessor in the development of a site-specific Tier III risk assessment. Input variables can be changed by the risk assessor automatically re-calculating the PCL. In addition, three test habitats have been developed that include species commonly used as ecological receptors by risk assessors in Texas. The calculator allows the selection of one or more individual species, including a growing list of threatened and endangered (T&E) species for risk calculations. For each COC, a fate and transport/toxicological profile was developed based on an exhaustive literature review which incorporated No Observed Adverse Effects Level (NOAEL)-Lowest Observed Adverse Effects Level (LOAEL)-based toxicity reference values (TRVs) for growth, reproduction and mortality. The TRVs, in conjunction with species uptake factors and a multimedia bioaccumulation/food web model, are used to calculate the PCL. When site-specific factors differ from default values this tool allows the user to use site-specific values to calculate refined PCLs provided the values can be supported.