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Myths and Facts about Asbestos-Cement
Andrew F. Oberta, MPH, CIH
The Environmental Consultancy

What is so important about asbestos-cement?
Over 95% of the chrysotile asbestos fiber mined worldwide is mixed with cement to form roofing, siding, pipes and many more products. These products have been used for decades throughout the world, but due to bans on their use in many countries they are now marketed primarily in developing countries. The following table shows where chrysotile asbestos fiber is currently mined and where it is consumed to be turned into products and installed. Note that the producing countries are not necessarily the users of the fiber they mine. In 2017 the United States imported 300 tons of chrysotile asbestos fiber, all of which was used by the chlor-alkali industry. (Source: US Geological Survey)

Production, tons (2017)
World total
Consumption, tons (2014)

What are some examples of asbestos-cement products? Here are a few of the major uses.

Corrugated siding
Corrugated roofing

Water distribution pipes

Residiential siding

Electrical ducts

Cooling tower

Is this what we call “Transite?”
Not entirely. Transite is a trade name for Johns-Manville asbestos-cement products made to specific formulations. For example, a line of Transite electrical ducts had 15 to 25% chrysotile asbestos, 45 to 55% Portland cement and 25 to 35% silica flour. I have seen a lot of asbestos-cement products in the US without the name “Transite,” not surprising since CertainTeed, National Gypsum, GAF Corporation, Celotex, Nicolet and others also produced it. I have never seen the name “Transite” used in connection with asbestos-cement products outside the US, where major producers included Eternit, Saint Gobain and James Hardie.

Transite flue duct

Transite label

So asbestos-cement is still sold world-wide?
Not if you believe the purveyors of the fiber and products. According to their literature and websites, they sell chrysotile fiber and chrysotile cement, not asbestos fiber and asbestos cement. This disingenuous shell game doesn’t make the fiber and products any less hazardous. Chrysotile is asbestos.
How else are people being misled about asbestos-cement? Now we get to the myths and facts....
Myth: Fibers are firmly locked in a cement matrix
Fact: Fibers are readily released from deteriorated or weathered surfaces. These pictures show the effect of weathering on asbestos-cement roofing. You can see the fibers protruding from the weathered surface.

Myth: Asbestos-cement cannot be crumbled to powder by hand pressure
Fact: Products such as this piece of corrugated siding, which came from a building that had been demolished, become friable from damage. Click on the picture for the video, in which I am easily crumbling debris from the edge of the piece. (The sound is my HEPA-filtered exhaust hood.)

Myth: Asbestos-cement products present no exposure hazard to building occupants
Fact: Asbestos roofing and siding can release fibers inside as well as outside the building. Not all asbestos-cement roofing and siding remains in as good condition as in these pictures. The inside of asbestos-cement roofing and siding is subject to the normal activities of the building occupants. Microvacuum sampling of the siding on the far right showed that these activities can release millions of fibers from the surfaces.

Myth: Asbestos-cement pipes do not present a health or environmental hazard
Fact: Health and environmental hazards start during the manufacturing process when the ends of the pipes are ground and the waste is disposed of carelessly. Fine dust produced during installation of the pipes is a hazard to the workers and community.

When the pipes are broken and crushed as they are dug up and removed, asbestos fibers are released . Pressure pipe for water distribution was made with crocidolite and amosite as well as chrysotile. White chrysotile and blue crocidolite fibers can be seen in the close-up on the uppper right. A microvacuum sample of the surface of a pipe fragment similar to the coupling on the right detected nearly a million chrysotile and crocidolite fibers per cm². Click on the picture to see the fibers close-up.

Myth: Paint and encapsulants offer permanent protection against asbestos fiber release
Fact: Paint and encapsulants deteriorate and take asbestos fibers with them when they peel off. We have to wonder why it is necessary to protect a material that is touted for its weather-resistance and durability, but encapsulants for asbestos-cement roofing and siding are widely marketed. Encapsulants are a form of paint, and a good paint job begins with surface preparation. We hope that no one sands asbestos-cement roofing and siding before they paint or encapsulate it, because of the obvious dust and health hazard created.

Paint and encapsulants might be removed deliberately or come off by themselves. These pictures show what happens to the asbestos fibers on the surface when that occurs: they come off with the paint and are embedded in the back side of the paint chips. This creates a problem for disposal by generating a waste stream of contaminated paint or encapsulant, not to mention contaminating the water and soil they may become mixed with or the pavement that catches the run-off.
Knowing all that, why do people still use asbestos-cement?
That's the problem -- people don't know and of course those who sell asbestos fiber and products don't tell them. Asbestos-cement products sell because they are cheap and intensively marketed under the fiction of "controlled use."

What about the millions of square meters of roofing and siding, and the kilometers of pipe, that are already in place?

Roofing and siding should be replaced with non-asbestos materials when a building is renovated. If the building is demolished it should be disposed of in a way that no one can scavenge and re-use it. Pipe should be replaced with non-asbestos pipe; again, responsible disposal is required.
What about managing asbestos-cement products in place?
The definitive resource is ASTM E2394 Standard Practice for Maintenance, Renovation and Repair of Installed Asbestos Cement Products ( It contains procedures for working with asbestos-cement products that are not practical to remove, emphasizing wet methods and hand tools. E2394 is written for those who may not have access to the expensive abatement equipment available in industrialized countries. It emphasizes the need for an infrastructure of contractors, tradesmen, government and NGOs to protect workers and the community. As the chairman of the ASTM task group that developed E2394 I would be pleased to answer any questions about it.

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