Signs of Asbestos in Wire Insulation
Be extra cautious when inspecting wires for asbestos
Highlights
Asbestos is a non-conductive material that resists fire, corrosion, and moisture.
It was commonly used in electrical wiring in the mid-20th century but has since been phased out.
You may suspect that the wiring in your home contains asbestos, but the only way to know for sure is through professional testing.
Asbestos was once a common material used in building components around the home, from wall insulation to wiring insulation. Consisting of various types of mineral fibers, asbestos can withstand high temperatures and resist fire, moisture, and corrosion. Since it's non-conductive, it was also commonly used to insulate electrical wires. If you think your home has asbestos wire, here's how to know for sure.
1. Fabric and Fiber
A visual inspection of the electrical wires in your home can give you a clue as to whether they contain asbestos or not. Electrical cables are typically wrapped in either a cloth or rubbery material. If asbestos is present, the wires may be wrapped in a black cloth that has a layer of white fibers underneath it.
Asbestos is friable, meaning it crumbles easily. If you're looking at the end of an electrical wire and the white fibrous material looks crumbly or fragile, it could very well be asbestos.
While a visual inspection can give you a hint about the contents of the material, it's by no means a definitive answer.
2. Older Age
Another clue that the electrical wiring in your home contains asbestos is the age of the electrical system. The heyday for asbestos-containing building materials was in the mid-20th century. By the 1980s, use of asbestos was starting to drop off, due to bans and general awareness of the potential health concerns caused by inhalation of the materials.
If your home was built after the 1990s, it's very unlikely that any of your electrical wiring contains asbestos. However, if your home was built in the 1950s or 1960s, and the electrical system hasn't been updated, there is a likelihood that asbestos is present.
3. Location
Due to its heat and fire resistance, asbestos wire was typically used in areas exposed to high temperatures. For example, the wiring to a lamp or overhead light could likely contain asbestos, as could wires that are located near a heater or boiler.
4. Brand
Electrical wiring that contains vermiculite may also contain asbestos. Vermiculite is a flaky mineral often used in insulation. It's not a type of asbestos, but for years, the main mine that provided vermiculite in the U.S. was contaminated with asbestos, meaning most vermiculite insulation was also contaminated with asbestos.
One of the most commonly used brands of vermiculite wire insulation was Zonolite. Other brands that could also contain asbestos include:
Gold Bond
Hy-Temp
Hi-Temp
Super 66
5. Test to Be Sure
The only way to be 100% certain whether your wiring contains asbestos or not is to have it tested. Testing involves taking a sample of the suspicious material and examining it under a microscope.
You can't see asbestos fibers with the naked eye. Anyone looking for the fibers under a microscope needs to be trained to know what to look for, as well as on the proper way to use the microscope.
If you're concerned about the presence of asbestos wiring in your home, work with a local professional asbestos testing company. The testing company can safely take a sample of the material, then send it to a lab for analysis. You need to be careful when handling asbestos, as you don't want to disturb the fibers, and have them become airborne.
Frequently Asked Questions
Asbestos was commonly used in cloth wiring, but not all types of cloth wiring contain it. The age, condition, and appearance of the wiring can provide clues as to whether asbestos is present or not, but the only way to know for sure if the wiring has asbestos is to have it tested.
Knob and tube wiring is an older type of electrical wiring that's no longer used and generally not considered safe. However, some homes still have it, or may have a knob and tube wiring system that was incorrectly modified or rigged to work with a modern electrical system. Knob and tube wiring may contain asbestos insulation, but the only way to know is to have the material professionally tested.
If you have an older electrical system with fraying wires and other signs of damage, removal may be the best course of action. When asbestos begins to break down, it's more likely to become airborne, increasing the risk of health issues when it's inhaled.
However, if the system is in good condition and doesn't have visible signs of wear or damage, leaving it alone may be the safest course of action. An asbestos abatement and removal professional can help you determine the best way to proceed.
Asbestos is a carcinogen, meaning it increases the risk of cancer. Inhaling asbestos fibers is linked to several respiratory issues, including asbestosis, or scarring on the lungs, lung cancer, and mesothelioma, another type of cancer. There's also a link between asbestos exposure and an increased risk of colon cancer and other cancers of the digestive system.
Usually, the people most at risk for disease related to asbestos exposure are those who spend a lot of time working around the material without protection. Electricians who work with asbestos wire have a higher risk of developing mesothelioma or lung cancer due to their exposure.