LATAG

LIBBY AREA TECHNICAL ASSISTANCE GROUP, INC.
January, 2010                                     NEWSLETTER

Report Summary

From the above discussion, it is clear that we still do not have enough information to estimate cancer and non-cancer risks from community exposures to LA associated with OU1 and OU2. Because of the complex multiple pathways of exposure to LA in the Libby area, and the lack of representativeactivity based sampling exposure data from the OU1 and OU2, uncertainties in exposure and risk of adverse health effects associated with OU1 and OU2 could result in an underestimate of cumulative cancer and non-cancer risks from exposure to LA in Libby.

The potential future health risks to Libby residents from exposure to LA is unknown because of uncertainties associated with: (a) the methods used to analyze asbestos; (b) the estimation of potential exposure to airborne asbestos from contaminated soils; (c) thelack toxicological information specific to LA; (d) the relative toxicity of short asbestos fibers (i.e., fibers <5 μm in length) in non-cancer health effectsand (e) the lack of epidemiologic data evaluating the risk of adverse health outcomes associated with low-level, intermittent exposures to LA.

Before any Records of Decision are implemented in Libby, the uncertainties outlined above must be addressed:

1. (a)             Improved analytical methods must be used to quantify levels of LA in both soil and air at OU1 and OU2 and throughout Libby.
2. (b)             Conduct site-specific, activity-based field tests, during all seasons of the year, to assist in developing empirical relationships for exposure scenarios involving re-suspension of asbestos fibers from solid media (e.g., soil, dust) into air. Without knowledge of such relationships, the assurance of the elimination of exposure pathways and the protection of public health is uncertain.  These limitations impede site-specific exposure assessment and risk characterization.
3. (c)             Execute a comprehensive LAtoxicity assessment to determine the effectiveness of the Libby clean-up actions and whether more actions are required. The toxicity assessment should include the effects of low dose exposure on susceptible populations, including children. Toxicology studies are also needed to adequately define the toxicity associated with short (<5 um) LAfibers since these fibers are predominant in Libby, including ambient air.
4. (d)             Determine the reference concentration (RfC) for inhalation exposure to LA, including the risk contribution of LA fibers less than 5 micrometers (um) in length and 0.25 um in diameter.
5. (e)             Sponsor epidemiologic studies employing the use of activity-based sampling results from Libby to allow the reconstruction of lower-bound estimates of exposure to LAassociated with clinically detectable disease.

In policies issued by EPA in their Risk Assessment Guidance for Superfund, EPA is required to understand the cumulative risk from all exposures in the Libby area, and not just one OU.  Recent case-control studies provide evidence for increased mesothelioma and lung cancer risks at very low lifetime cumulative exposures to amphibole asbestos. The Risk Assessment Guidancedocument requires EPA determine the complete exposure pathways that exist for the Libby site. EPA is required to quantify the magnitude, frequency and duration of exposure for each pathway identified in Libby to determine cumulative risk. EPA is required to estimate reasonable maximum exposures for individual pathways. Given the complex multiple pathways of exposure to LA in the Libby area, the combination of exposures across pathways must be considered in cumulative risk estimates.

Exposure assessments must consider past, present, and future exposures.  The Libby population has already had significant exposures to date that must be included in any benchmarks with consideration of future acceptable exposures. This is critically important for subpopulations that may be at increased risk from exposures to LA due to increased sensitivity, behavior patterns that may result in high exposure, and/or current or past exposures from other sources. Subpopulations in Libby that may be more sensitive to exposure to LA include infants and children, elderly people, and people with chronic illnesses.

Board Members