Zonolite Insulation

Fact Checked

Zonolite is the trademarked name of a vermiculite attic insulation product sold between the 1940s and 1990s. Most Zonolite is contaminated with highly-toxic asbestos.

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Zonolite is a type of loose-fill insulation designed to be poured onto an attic floor. Though it is no longer made, its popularity in the past means it can still be found in millions of homes across the U.S.

Quick Fact:
  • Zonolite is made out of vermiculite, a naturally occurring mineral with a silver-gold or light brown color.
  • From a distance, vermiculite insulation resembles pebbles or gravel, and it fades to a grey color over time.
  • The product is very lightweight because vermiculite has the unique ability to be puffed out when heated, much like popcorn.
  • Most Zonolite is contaminated with a highly toxic form of asbestos because of where the vermiculite was mined.

Vermiculite and asbestos have much in common: Both are resistant to fire and chemical corrosion, and both make excellent insulating materials. They also occurred in the same geological formation mined by W.R. Grace and Company, which is why most Zonolite is dangerous. Pure vermiculite is harmless, but vermiculite mined alongside asbestos poses a serious risk for asbestos exposure.

During the decades when Zonolite was manufactured, most of the world’s supply of vermiculite came from the town of Libby, Montana, which became so contaminated by asbestos that the U.S. Environmental Protection Agency (EPA) has now been working to clean the area up for almost 20 years. The Zonolite insulation distributed across the nation will haunt American homes for many more years to come.

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History of Zonolite Insulation

The history of Zonolite begins when E.N. Alley launched his vermiculite mining business in Libby, Montana, almost a century ago. Alley created the Zonolite brand as a commercial name for the mineral, and more than 40 years later, in 1963, his business was acquired by W.R. Grace and Company, becoming its Zonolite Division.

At A Glance
  • Years Produced: 1940 – 1980
  • Places Used: Attics
  • Toxicity: High
  • Asbestos Use Banned: No
  • Friable: Yes

By the time W.R. Grace took over the operation, the asbestos hazard was clear. Asbestos dust had already caused lung diseases and deaths among vermiculite miners and processing plant workers, but the company’s executives ignored this information. They continued growing the Zonolite business throughout the 1970s, even as more employees and residents of the town fell ill from asbestos exposure.

Zonolite Insulation

It is estimated W.R. Grace processed nearly 200,000 tons of vermiculite from the Libby mine each year until the mine finally ceased operations in 1990, far too late to spare W.R. Grace from the wave of lawsuits to come. The Libby mine and surrounding areas were declared a superfund site in 2002, and the EPA now advises all American homeowners to take extreme caution with Zonolite insulation found in attics.

Dangers of Zonolite Insulation

As many as 35 million U.S. homes, buildings and offices may contain Zonolite contaminated with asbestos. Furthermore, the specific type of asbestos found at the mine where the product was sourced poses a particularly grave risk.

  • Most commercially used asbestos is called chrysotile, also known as “white asbestos.” Chrysotile is a serpentine form of asbestos, meaning its fibers are curly and occur in sheets of crystals.
  • The asbestos that contaminates most Zonolite, however, is called tremolite. This noncommercial variety is described as an amphibole form of asbestos because its crystal fibers are straight rather than curly.

It takes less exposure to tremolite to cause asbestos-related disease, compared to the more common chrysotile. Some studies suggest tremolite could be 10 times more dangerous than the white asbestos used by most manufacturers.

People have the greatest risk of developing an illness such as asbestosis or malignant mesothelioma when they are exposed to asbestos dust on a regular basis over many years, and any activity that disturbs Zonolite can potentially release microscopic asbestos fibers into the air.

Working with contaminated Zonolite directly during home construction or renovation creates a major exposure risk, but even simple tasks, such as moving things around in an attic or working on ceiling fixtures, can lead to enough cumulative exposure over the years to cause an asbestos-related illness. There is no safe level of asbestos exposure.

EPA recommendations for homeowners with Zonolite insulation:

  • Do not allow anyone into the attic unless completely necessary.
  • Do not store items in the attic.
  • Do not attempt to remove the insulation yourself if you are not a trained asbestos-abatement professional.


Throughout the 1990s, so many personal injury and property damage lawsuits were filed against W.R. Grace over asbestos exposure that the company finally sought Chapter 11 bankruptcy protection in 2001, along with 61 of its affiliates. After a drawn-out legal process, the plan of reorganization was confirmed in 2011, becoming effective in 2014.

The reorganization required W.R. Grace to set up two separate trust funds to provide compensation to present and future victims of asbestos exposure.

  • The Zonolite Attic Insulation Trust serves property damage claimants by partially reimbursing the cost of professional Zonolite removal and asbestos abatement.
  • The W.R. Grace & Co. Asbestos Personal Injury Trust compensates individuals and families who have suffered because of asbestos-related illnesses caused by W.R. Grace operations and products.

Combined, these two trusts are worth more than $4 billion. Payments totaled more than $353 million in 2015, with thousands of claimants receiving compensation.

Quick Fact:

Between 1919 and 1990, 70 percent of the world’s supply of vermiculite came from the asbestos-contaminated mine in Libby, Montana, according to the U.S. Environmental Protection Agency.

Abating Zonolite Insulation

Handling asbestos-containing Zonolite is a dangerous task that must be performed with caution. Microscopic asbestos dust cannot be seen, smelled or tasted, and the toxic mineral fibers can slip through a standard dust mask. Disturbing contaminated attic insulation can put all those living in the home at risk, and asbestos can also contaminate work clothes, leading to secondhand exposure in workers’ families.

If your home contains Zonolite attic insulation, consult or hire an asbestos abatement professional to assist with any removal or renovation work that may affect the attic.

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Daniel King joined Asbestos.com in 2017. He comes from a military family and attended high school on an Air Force base in Japan, so he feels a close connection to veterans, military families and the many hardships they face. As an investigative writer with interests in mesothelioma research and environmental issues, he seeks to educate others about the dangers of asbestos exposure to protect them from the deadly carcinogen. Daniel holds several certificates in health writing from the Centers for Disease Control and Prevention, and he is a member of the National Association of Science Writers.

Walter Pacheco, Managing Editor at Asbestos.com
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13 Cited Article Sources

The sources on all content featured in The Mesothelioma Center at Asbestos.com include medical and scientific studies, peer-reviewed studies and other research documents from reputable organizations.

  1. Ewing, WM, Hays, SM, et al. Zonolite attic insulation exposure studies. International Journal of Occupational and Environmental Health. (2010 July-September). Retrieved from: http://www.ncbi.nlm.nih.gov/pubmed/20662420#
  2. Environmental Protection Agency. (2010, November 30).Protect Your Family from Asbestos-Containing Vermiculite. Retrieved from: http://www.epa.gov/asbestos/pubs/verm_questions.html
  3. Environmental Protection Agency. (2012 July 10). Vermiculite. Retrieved from: http://www.epa.gov/asbestos/pubs/verm.html
  4. Schneider, A. (2010 December 8). Killer in the Attic: EPA Still Evades Zonolite Warnings. AOL News. Retrieved from: http://www.aolnews.com/2010/12/08/killer-in-the-attic-epa-still-evades-zonolite-warnings/
  5. Schneider, A. (2002 December 29). White House budget office thwarts EPA warning on asbestos-laced insulation. St. Louis Post-Dispatch. Retrieved from: http://www.citizen.org/documents/zonolite.pdf
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  7. Schneider, A. (2008 February 25). Canadian Who Lost Five Family Members to Asbestos in Zonolite Insulation Wants Government to Warn Others. Retrieved from: http://blog.seattlepi.com/secretingredients/2008/02/25/canadiian-who-lost-five-family-members-to-asbestos-in-zonolite-insulation-wants-government-to-warn-others/
  8. Great Falls Tribune. (2004 March 8). Q&A Zonolite? Vermiculite? Asbestos?. Retrieved from: http://www.greatfallstribune.com/news/stories/20040308/localnews/45301.html
  9. North, E. (2011, November 15). What is Zonolite Insulation (And Vermiculite and Asbestos)? Retrieved from: http://www.energyauditingblog.com/what-is-zonolite/
  10. Seltzer, R. (2015, February 11). W.R. Grace makes $490M final payment to asbestos trust. Retrieved from: https://www.bizjournals.com/baltimore/news/2015/02/11/w-r-grace-makes-490m-final-payment-to-asbestos.html
  11. United States Environmental Protection Agency. (n.d.). Protect Your Family from Asbestos-Contaminated Vermiculite Insulation. Retrieved from: https://www.epa.gov/asbestos/protect-your-family-asbestos-contaminated-vermiculite-insulation
  12. WRG Asbestos PI Trust. (n.d.). About. Retrieved from: http://www.wrgraceasbestostrust.com/about/
  13. Zonolite Attic Insulation Trust. (n.d.). About the Zai Trust. Retrieved from: http://www.zonoliteatticinsulation.com/general-information

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Last Modified January 20, 2020

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