Asbestos products numbered in the thousands before it was declared a carcinogen in the 1970s and effectively eliminated from most industrial and commercial uses. But during the century when it was in use, asbestos was valued as a raw material for its resiliency, flexibility and its resistance to chemical corrosion and heat. Wherever there was heat or fire in use as a production element, there were usually asbestos products in use as well. Steel mills, chemical plants, oil refineries, auto plants and textile mills all made use of asbestos as insulation, for the manufacture of bricks and cement, in gasket and sealing materials and for heat protection in a production line environment. But the use of asbestos in industrial applications was probably surpassed ultimately by its uses in the home.
Asbestos in Home Construction
The characteristics of asbestos that made it valuable in industrial applications made it a useful component of many home construction materials. Asbestos roofing shingles were developed as a fire resistant alternative to wooden shakes or shingles; they were flexible and easy to work with and were a natural fire retardant rather than a combustible material. Asbestos house siding was brought into use for similar reasons: it was fire resistant, provided some insulating capacity and was easier to mount than shiplap or shingled siding. Asbestos siding was also not susceptible to dry rot or splintering.
At some point in the nation’s industrial development an inventive construction professional realized what the addition of asbestos to cement could accomplish. Asbestos fibers in cement acted as a natural bonding agent, causing the cement to set more readily and rendering it less likely to crack. For decades asbestos was an additive to Portland cement, and every year hundreds of tons of that cement mixture were poured for home foundations, piers, and basement walls.
Asbestos also found its way into home interiors. It was used as an additive for vinyl flooring sheets such as linoleum and the brand name Congoleum. Once again its binding properties and resilience made it an attractive addition to vinyl synthetics. Asbestos was also incorporated into flooring tiles manufactured from polyvinyl chloride polymers, adding flexibility and increased resilience. Ceiling tiles used in homes commonly contained asbestos for its insulating properties. In many cases the adhesive used to install these flooring tiles and sheet linoleum contained asbestos as well. Asbestos was a common additive to joint sealant used with wallboard; several manufacturers also included it as a raw ingredient in the manufacture of wallboard itself.
Asbestos in Home Insulation
The insulating properties of asbestos have always been among the mineral’s most attractive characteristics. Home insulation made from asbestos compounds of various types became very popular during the twentieth century. It was used in walls and for ceilings. It was also commonly used to insulate heating systems that used hot water or to insulate heating boilers in a basement. This type of insulation came in blanket form and can still be seen today in many older homes, both in the walls and along the pipes associated with an older furnace and heating system.
From 1960 on one of the most popular forms of insulation for homes was vermiculite, an ore that could be heated and would “pop” into small kernels that had effective insulating properties and could be blown into walls. For many years the primary source of vermiculite in the United States was a mine in Libby, Montana that was operated by W.R. Grace Corp. The vermiculite ore from that mine was, and is, contaminated with tremolite asbestos. At one point the Libby mine was shipping 80% or more of all the vermiculite being used in the United States. W.R. Grace had 26 production facilities scattered around the country that were producing vermiculite insulation under the trade name Zonolite. It remains in millions of homes today.