From the early 1900s through the 1970s, asbestos was used in many building materials as a cheap, readily available way to add insulation, fire resistance, and reinforcement. Following the discovery of its health risks, a variety of asbestos-containing materials (ACMs) were banned between 1973 and 1979.
But due to its low risk to the general public, asbestos-containing concrete (or asbestos concrete) remains legal to manufacture, import, and use in new construction. Exposure risk is low when the concrete is set and undisturbed, but any mechanical damage can and will release asbestos fiber into the immediate environment.
As such, it poses a particular safety threat to those in the construction industry when proper precautions aren't taken. Below, we'll review why asbestos cement was useful, where construction crews are likely to encounter it today, and the conditions under which the Occupational Safety and Health Administration (OSHA) requires extra safety measures.
Uses and Benefits of Asbestos in Concrete
The
fiber-reinforcement of concrete is a common practice that incorporates a wide variety of fibrous materials into concrete mixtures. Since the fibers are randomly oriented but uniformly distributed throughout the concrete, they increase its structural integrity.
Generally speaking, fiber reinforcement is used to:
Asbestos was common in fiber-reinforced concrete for the same reason it was common in many products: it was inexpensive, easy to acquire, and had some useful properties.
Typically, asbestos concrete consisted primarily of chrysotile asbestos ("white asbestos," often called "good" asbestos) mixed with Portland concrete. However, small amounts of the more dangerous crocidolite asbestos ("blue asbestos") were often part of the mix as well.
Alongside the general benefits of fiber reinforcement, asbestos had a few additional advantages:
- It easily blended into concrete mixes, whereas other fibers can make concrete less workable.
- It was resistant to corrosion, unlike other fibers that cause corrosion stains at the surface.
- It had low friction. This made it particularly attractive for cement piping.
- Its superior strength-for-weight ratio made it a go-to roofing material to replace slate or clay.
The Risks of Asbestos in Concrete
Inhalation of airborne particles is the primary risk of any asbestos product. Since the fibers in asbestos concrete don't become airborne without mechanical disturbance, it poses a minimal risk if the concrete remains set and stable.
In the past, workers in asbestos cement manufacturing bore (and are still bearing) the brunt of the health risks related to asbestos concrete.
Exposure through manufacturing is no longer an ongoing concern, but any chipping, drilling, pressure-washing, or demolition of asbestos concrete is.
Once fibers are released into the air and inhaled, they remain in the lungs for a long time, increasing the risk for breathing problems, heart failure, lung cancer, mesothelioma, and other conditions years down the road.
The biggest problem with asbestos concrete is that it can't be identified without professional testing. Since asbestos fibers are set in a hardened mix, they can't be identified with the naked eye the way they sometimes can in wallboard and other products.
This means that if you suspect your construction, renovation, or demolition site may have asbestos concrete, you
must have it tested for the safety of your crew.
Asbestos in Concrete Today
Although it's still legal to manufacture and use asbestos concrete in corrugated sheets, flat sheets, and shingles, companies in the U.S. shut down stateside manufacturing decades ago as litigation costs grew. Importation poses a liability to anyone in the chain of distribution, as does its application.
So you'll rarely, if ever, encounter it in new construction. The vast majority of asbestos cement you'll encounter today was set in the late 1980s or earlier.
In addition to the concern from
human disturbance of old concrete, we're starting to see the surface erosion and deterioration of asbestos concrete whose 70-year lifespan is expiring.
This is particularly concerning for old asbestos cement piping, which was common in sewage systems, drainage pipes, and storm drainage systems.
Shingles and siding are also finally deteriorating due to normal weathering.
Careful monitoring for corrosion is necessary to prevent a public health threat. In the coming decades, projects to tear up and replace old asbestos cement will remain common. Each project will carry health risks for its workers.
Asbestos Concrete Safety
When working with asbestos concrete, construction must adhere to OSHA Construction Standard 29 CFR 1926.1101(g) in order to limit the exposure of the crew and the general public to airborne asbestos fibers.
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