Asbestos cement siding was widely used in the U.S. construction industry from the early 1900s through the early 1970s, in both homes and commercial buildings. The addition of asbestos to cement created a building material that was lightweight, economical, durable and moldable into many different forms.
The popularity of asbestos cement siding declined quickly, as information about the dangers of asbestos became known. Studies have shown that people who breathe high levels of asbestos fibers may have an increased risk of lung cancer, mesothelioma (cancer of the lining of the chest and abdominal cavity) or asbestosis (a condition in which the lungs are scarred with fibrous tissue). The symptoms of these diseases often appear years after the first exposure to asbestos.
If the asbestos cement siding is intact, and it cannot be broken or crumbled by hand, it does not present a health hazard. If it is damaged in some way – even if you drill a hole in it, cut it with a saw, or sand it — then it may release asbestos fibers, which can then be inhaled and can remain in the lungs for a long time.
It is impossible to tell just by sight whether siding contains asbestos fibers, unless it is labeled as such. If you suspect that asbestos cement siding might be present in your home or commercial building, because it was built when that type of siding was commonly used, check it regularly. If the siding is in good condition, then the best course of action may be to leave it alone, since asbestos material that is not damaged generally does not release asbestos fibers. Look for tears, abrasions, bumps or water damage, especially in areas that are or might be exposed to vibration, air flow or traffic.
When the siding is damaged, or if you plan to make renovations or repairs that will disturb the siding, call a qualified professional contractor or asbestos abatement company. They will analyze samples of the material, confirm whether asbestos is present, and either repair or remove the asbestos cement siding.
Although repair is usually less costly, it may not be recommended because it can complicate matters, if the asbestos material needs to be removed later. Removal is more expensive, but may be required by your state or local regulations. Whichever method you choose – repair or removal – have it done by a professional who is trained to handle asbestos safely.