How does an entire town become contaminated with asbestos dust? The story of Libby, Montana

Aug 29, 2022

When we think of asbestos we often think of building materials – floor tile, pipe insulation, black flooring mastic/glue, and popcorn ceilings. When it comes to abatement, teams remove or repair the broken materials along with isolating or encapsulating the area to prevent disturbance. But, what happens when an entire town becomes contaminated with asbestos? This blog will discuss the asbestos contamination of Libby, Montana resulting from vermiculite mining and efforts taken to protect the residents.

Vermiculite and Libby Amphiboles

Vermiculite is a sheet-like silicate mineral that is coveted for its insulating and thermal resistant properties but after decades of production vermiculite ore was discovered to contain 26% amphibole asbestos. While all forms of asbestos are hazardous, amphiboles have been shown to be more harmful than chrysotile. This due to the needle-like shape of amphiboles vs the curvy pattern of chrysotile which allows to it adhere to the lungs easier.

According to the EPA, vermiculite was discovered in Libby, MT by gold miners in 1881. The mine was first operated by the Zonolite Company starting in the 1920s with the operations transitioning to W.R. Grace in the 1960’s and production continued until the 1990’s. The mine is thought to have produced 80% of the global supply of vermiculite.

Health Effects of Residents in Libby

It is believed that peak asbestos exposure in Libby was between the 1950s and 1970s – where production was at its highest and there was a lack of engineering controls. In the early 2000s, the Agency for Toxic Substances and Disease Registry (ATSDR) published a report on respiratory related deaths in Libby from the late 1970s to the late 1990s. The report showed that malignant respiratory deaths were 20 to 40 times higher than normal and non-malignant respiratory deaths including the illness asbestosis, were at over 40 times higher than normal.

Libby Remediation Efforts

In the late 2000s, a public health emergency was declared in Libby and remediation activities began. Since then, the EPA has remediated thousands of contaminated properties and over a million cubic yards of soil. The ambient levels of asbestos in the air are now considered 100,000 times less than during peak production. While the first phase of the cleanup is complete, the surrounding woods near the mines may still have contamination.


While this blog is primarily about the contamination of Libby, the bigger picture concern is the number of homes and businesses that still contain vermiculite insulation. While modern vermiculate may not be asbestos containing, it is best to have suspect materials evaluated by an environmental consultant such as Indoor Science.