Zonolite® is a trademark insulation product manufactured by the W.R. Grace Company. Produced at several plants throughout the United States, Zonolite products contain a processed form of the mineral vermiculite and are intended for attic insulation in order to provide both warmth and fire resistance. When subjected to heat, vermiculite has the unusual property of exfoliating or expanding into worm-like pieces to fill in empty spaces, therefore making it a likely candidate for use in insulation.
Zonolite and Asbestos
W.R. Grace-manufactured Zonolite is a general name for many different products in the company's insulation line. While many households wouldn't recognize the word "Zonolite", for those concerned with asbestos contamination and exposure, Zonolite will probably raise a red flag.
Vermiculite is usually a safe mineral, but unfortunately, the vermiculite used to manufacture Zonolite came from a mine in Libby, Montana that was contaminated with very hazardous tremolite asbestos. Because of that, millions of homes throughout the U.S. may be tainted with attic insulation that contains asbestos.
As early as the 1950s, the owners and managers at W.R. Grace were already aware of the asbestos contamination at the Libby mine. As a matter of fact, in 1956, the Montana Board of Health requested that the company "reduce the high concentrations of asbestos dust in dry mill where the vermiculite ore was processed" due to lung ailments among the workers. By 1960, studies showed that 36% of the employees who were involved with day-to-day manufacturing of Zonolite already had lung problems.
Internal reports from one Grace executive to another, recently released for litigation purposes, also show that they were aware of the hazards of tremolite asbestos-containing vermiculite but succeeding in covering up the concerns. In some cases, plant managers were also aware that manufacturing Zonolite was a major health hazard to those who worked at Grace, but did nothing to protect employees.
Despite the information about the dangers of the Libby-mined vermiculite, the company continued to sell Zonolite until 1985, and the United States Environmental Protection Agency believes that about 35 million homes in America contain Zonolite-brand insulation.
When left alone, in-tact Zonolite should not cause a problem. However, if the Zonolite becomes old and crumbly or is damaged in some way, it could release dangerous asbestos fibers. Any number of home projects could cause Zonolite to be disturbed, so great care should be taken with any repair or renovation projects that may involve a home's Zonolite attic insulation.
Last modified: December 28, 2010.