The U.S. EPA RTR Program's Tiered Screening Approach to Evaluating Ingestion Risks from Emissions of PBHAPs

摘要

U.S. EPA's Risk and Technology Review (RTR) assesses risks remaining from emissions of hazardous air pollutants (HAP) after implementing maximum achievable control technologies. Risk characterization includes a tired screen run with custom software tools to evaluate potential risks from ingestion of fish, farm foods, soil, and breastmilk (for infants) contaminated from persistent and bioaccumulative HAP (PBHAP) emissions. The screens are based on pre-run scenarios in the Total Risk Integrated Methodology's Fate, Transport, and Ecological Exposure module (TRIM.FaTE), producing PBHAP threshold emission rates below which a facility's emissions are unlikely to pose risks above benchmark levels. Each tier uses additional site-specific data to reduce instances of false-positive estimates of such risk. Tier 1 uses settings that maximize media contamination and ingestion. EPA uses a software tool to compare facility emissions to Tier 1 threshold rates. For facilities not passing Tier 1, Tier 2 allows EPA to efficiently incorporate more site-specificity. EPA ran many TRIM.FaTE simulations with a variety of lake locations and meteorology to produce a variety of Tier 2 threshold rates. EPA uses a tool with national databases of lakes and local meteorology to identify appropriate threshold rates per facility. While Tier 1 combines high-end ingestion of fish and farm foods, Tier 2 evaluates them separately, allows fish to come from multiple lakes, and lowers the farm-food ingestion to home-gardener levels. Using Tier 3, EPA continues to refine the evaluation by evaluating local lakes for fishability, estimating the exposure-mitigating effects of plume rise, and better accounts for the effects of local hourly meteorology on chemical fate and transport. After Tier 3, if the potential remains for risks above benchmark levels, EPA may conduct a site-specific risk assessment using TRIM.FaTE and local data on watersheds and soil and water characteristics.