Region 8

Libby Asbestos: Human Health Risk Assessment

After rigorous scientific review, EPA has completed the final Toxicological Review of Libby Amphibole Asbestos (LA). This information allows EPA to assign a numeric value to risk levels associated with different activities.

The two toxicity values are the:

  • cancer value – an estimate of the potential for cancer health effects (mesothelioma and lung cancer) from exposure to LA; and
  • non-cancer value – an estimate of the potential for non-cancer health effects (asbestosis and pleural thickening) from exposure to LA.

Using these values and exposure data collected in Libby and Troy, EPA has also completed a draft Site-wide Human Health Risk Assessment. This document is available for review and informal comment; EPA will also accept formal comments on the draft risk assessment during a proposed plan public comment period which is expected in early 2015.

What Does the Draft Risk Assessment Tell Us?

The Human Health Risk Assessment will help support decisions for the site and answers basic questions such as “how toxic is Libby Amphibole Asbestos” and “have we cleaned up enough.”

Additional documents are available for review, including a fact sheet, briefing, executive summary of the human health risk assessment and the draft Site-wide Human Health Risk Assessment.

Here is a summary of the draft Site-wide Human Health Risk Assessment:

1. EPA has Significantly Reduced Risk from Exposure to Asbestos

EPA has removed major sources of Libby Amphibole (LA) asbestos in and around Libby and Troy. We have investigated thousands of properties and conducted removals at more than 2,000 private homes and properties. Removals include the former export plant, former screening plant, boat ramp, rail yard, golf course, flyway properties, schools and school yards, historic Hotel Libby, creek beds and other public areas. EPA has now removed more than one million cubic yards of impacted soil.

2. It is Now Possible to Live and Work in Libby Without Excessive Exposure to Asbestos

chart showing libby amphibole asbestos concentration in air in 1975 vs. 2014

Our risk assessment shows that EPA’s indoor and outdoor cleanups have been effective in reducing both cancer and non-cancer risks in Libby and Troy. This means that EPA’s cleanup work results in acceptable risk levels. 

EPA has extensively tested outdoor air in Libby and Troy for LA asbestos and concentrations are now equivalent to those found in other Montana cities. Air asbestos concentrations today are up to 100,000 times lower than when the mine and processing facilities were operating. Higher levels of LA could be found at some properties where owners have not yet provided access and in areas located near the former vermiculite mine. Those who own property within the site should contact EPA’s Libby Information Office, 406-293-6194, to schedule a property inspection if they haven’t already done so.

3. Remaining Asbestos Needs to be Safely Managed

It is not possible to remove all LA in Libby and Troy. LA is naturally- occurring in this area. In addition, LA that is sealed behind indoor walls or outdoors below the surface does not pose a health risk unless it is disturbed. Ensuring that LA does not present a risk in the future will be part of a long-term plan for the site. EPA and the Montana Department of Environmental Protection (MDEQ) are confident that any remaining contamination can be effectively managed, and the selected remedy will include details on how any waste that is left in place will be managed after cleanup is completed.

4. There are Two Primary Pathways for Exposure to LA Asbestos

Inhalation and ingestion are the two primary ways that people are exposed to LA asbestos. Inhalation carries the greatest risk. Interrupting this exposure pathway is essential to managing risk from LA asbestos. In other words, the way to avoid potential health risks from LA asbestos is to prevent inhalation of the fibers.

5. Risk Management Will be Based on a Combination of Factors – Not a Single Number

Because exposure is associated with dust generation, remedial action objectives will focus on managing source concentrations as well as activities and their locations. For example, higher risks are currently associated with significant soil excavation and soil dust generation or hiking in areas with elevated concentrations of LA asbestos. Risks are also elevated for career contractors working in areas with vermiculite.

What are the Next Steps?

graphic showing the next steps following the human health risk assessment: feasibility study, propsed plan public comment period, and record of decision

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