Asbestos Human Health Risk Assessments

Location: Multiple states

U.S. Environmental Protection Agency, Regions 4 and 6


  • Former vermiculite exfoliation facilities that received ore mined in Libby, Montana that was contaminated with amphibole asbestos. Site soil, air, and dust impacted by asbestos contamination.
  • Conducted approximately 20 Human Health Risk Assessments for asbestos exposure based on the EPA Asbestos Framework document. Implemented the Libby Amphibole Asbestos toxicity values from EPA for HHRAs performed after 2014.
  • Activity based air sampling, as well as, soil and dust sampling were used to evaluate risks from asbestos exposure.
  • The HHRA for one of the sites evaluated, the Big Tex Site in San Antonio, Texas, was considered by the U.S. EPA Technical Review Workgroup as an example “template” for other regions and other Libby asbestos sites.
asbestos sampling


As a subcontractor on the EPA RAC Region 4 Lite and START Region 6 contracts, Avatar Environmental was the technical lead in performing approximately 20 human health risk assessments (HHRAs) for potential exposure to amphibole asbestos at a variety of former vermiculite exfoliation facilities located in Texas (Houston and San Antonio) and in multiple states in EPA Region 4. Avatar scientists took prominent roles in the characterization of the site contamination, often times designing the sampling approaches. Air samples were collected using a combination of generic and site-specific activity based sampling (ABS) techniques. Stationary air samples were also collected. Bulk samples (surface and subsurface soil) were collected along with Microvac dust samples from within on-site buildings. At the majority of the sites, the sample results indicated that asbestos contamination existed in the soil, air, and dust (inside buildings). The goal of the HHRAs was to determine whether potential health risks existed to worker and/or local residents that could be exposed and to make decisions on site cleanup options. Risks were estimated using the ABS data from on-site activities such as raking. Other results were also evaluated including stationary air samples as well as soil and dust (inside on-site buildings) sample results. Meteorological data were also collected and considered in the assessments. The asbestos HHRA for the Big Tex Site in San Antonio, Texas was one of the first for Libby asbestos sites performed by any contractor following EPA’s Asbestos Framework guidance that was released during the development of the HHRA. The Framework was developed, in part, due to EPA concerns that the previous 1% in soil definition of asbestos sites might not be health protective, especially when sites contained amphibole asbestos. Avatar developed the Big Tex HHRA in consultation with EPA Region 6 risk assessors as well as EPA risk assessors from other regions who are part of the EPA Technical Review Workgroup (TRW) prior to the actual release of the Framework document. Further, for HHRAs performed after December 2014, Avatar scientists included EPA’s toxicity values specific to Libby amphibole asbestos, which for the first time, allowed for the estimation of noncancer hazards in addition to the estimation of excess lifetime cancer risks.   asbestos 2