Last Updated: Jul 5, 2021
The term "asbestos" can be a loaded one, and for a good reason. Elevated or prolonged exposure to airborne asbestos fibers can have serious health consequences that may not be discovered until years after exposure. On the other hand, having been used in so many products worldwide, in particular building materials, the financial cost to society to "get rid" of asbestos that is already out there would be extreme. Fortunately for current homeowners, occupational hygiene experts have come to a consensus developed through many years of research. They advise that homeowners and building managers can leave asbestos-containing materials (that are maintained and in good condition) as they are without presenting a significant exposure risk. Additional precautions need to be taken when these materials will be disturbed, such as during renovation work.
Let's review some general information on asbestos and the risks it poses, then consider some steps a homeowner concerned about asbestos in their home might take.
While asbestos is now heavily regulated, it can still be found during renovations in homes or buildings built decades ago. Asbestos crumbles easily and is often blue (crocidolite), brown (amosite), or white (chrysotile) in color.
Asbestos was a contaminant in vermiculite produced from a mine in Libby, Montana. Vermiculite from this mine was used across North America. In attic insulation and other products until the mine closed in 1990.
There is evidence that asbestos has been used to improve the properties of other materials since prehistoric times. Ancient peoples incorporated it into candle wicks, clay pots, shrouds for the deceased, and tablecloths. The Industrial Revolution saw the use of asbestos accelerate in the late 1800s, with peak use occurring in the 1960s and early 1970s. Asbestos has been used worldwide, and it has been estimated that it may be present in over 3,000 products.
As evidence of the health effects of asbestos mounted to a level that makers could no longer ignore, industries began voluntarily reducing or eliminating its use in the 1970s. Governments implemented varying degrees of restrictions on use and handling. There wasn't one specific "cut-off" date when nations and states banned all asbestos products altogether. Instead, manufacturers stopped using asbestos over time on a product-by-product basis, determined based on regulations, legal liability, and public pressure.
Friable asbestos-containing materials are materials that are easily crumbled or powdered using hand pressure. These hazardous products were generally discontinued by the late 1970s. Non-friable materials were generally (but not wholly) discontinued by the mid-to-late 1980s.
In the home building industry, asbestos was used in a myriad of manufactured building products. Examples of which include:
It was also added to materials that were mixed on-site, such as:
For the sake of awareness, it is worth mentioning some other asbestos-containing products more commonly used in commercial, multi-residential, or industrial buildings than in single-family dwellings. Asbestos-containing spray-applied fireproofing insulated many building's structural components. Bitumen-based roofing products used for flat roofs also historically contained low concentrations of asbestos.
The use of asbestos in home building materials after the late 1980s is uncommon, at least in North America. But, on rare occasions, you might still find it in products such as vinyl floor tiles, caulking, roofing products, and cement building products. This issue, however, is typically the result of supply chains, as opposed to the intentional inclusion of asbestos in the product. You can find product sheets indicating the composition of many new building materials on the internet.
Below is a summary of several of the more common materials found in homes. It is not exhaustive.
Small quantities of asbestos (generally trace to 5% by mass) were used in vinyl floor tiles and the adhesive used to fix them to the floor. The old 9" x 9" vinyl floor tiles very commonly contain asbestos. Asbestos was also used a little less commonly in 12" x 12" floor tiles up through the mid-to-late-1980s.
Builders historically used various asbestos-containing products to insulate pipe straights and fittings before fiberglass became the dominant product. Like fiberglass, many of these products had a canvas cover. Examples include cellulose (paper-like) pipe insulation, such as corrugated Air Cell and flat, multi-layered sweat wrap, cementitious white magnesium block (mag-block) pipe insulation, and cement-like grey parging on pipe fittings. The use of asbestos in pipe insulation was generally discontinued by the late 1970s. Asbestos concentrations vary widely depending on the type of insulation.
Asbestos may be found in both the grey or brown rough coat and the white finish coat of plaster walls and ceilings. It may also be present in textured or "popcorn" ceiling and wall finishes. Asbestos was often mixed into these materials on-site, generally in low quantities (trace to 5%). As a result, it is not distributed uniformly. So, trying to delineate which finishes within a building contain asbestos and don't can be difficult without extensive sampling. The use of asbestos in plaster and texture coat generally tapered off by the early 1980s, although builders used remaining material stock into the 1980s.
As with plaster, contractors mixed asbestos into drywall joint compound on-site. This process generally used small quantities (trace to 5%). Therefore, it isn't easy to delineate which walls or ceilings contain asbestos and don't. It's also worth noting that joint compounds and similar products were also used as a skim coat on walls and ceilings (drywall or otherwise) to even out imperfections before applying wallpaper. The use of asbestos in plaster and joint compound generally tapered off by the early 1980s. However, due to the shelf life of dry joint compound products, leftover stock persisted for many years.
Although generally found less commonly than in floor tiles, asbestos was present in various acoustic ceiling tiles in varying concentrations, with most use ending by 1980. Asbestos was used in both lay-in and fixed ceiling tile styles, as well as in the mastic used to glue fixed tiles to the ceiling.
Various pre-fabricated asbestos-cement products went into building construction, including cement board in utility areas (e.g., near electrical panels) or moisture-prone areas (e.g., behind shower tile), cement drain pipe, and corrugated siding. Asbestos concentrations vary widely depending on the product. I have seen lab results indicating 95% asbestos in a particular set of cement pipe samples. However, concentrations of 15 to 25% are much more common. While asbestos use has generally ceased in the current versions of these products, it is worth reviewing product information sheets to confirm.
Products that were glued or sealed might have contained asbestos, generally low (trace to 5%) concentrations. Use in friable cement containing parging, e.g., to seal a duct penetration through a wall or cover a brick or cement block foundation wall, generally ceased by the late 1970s. The use of asbestos in caulking and other mastic applications mostly ended in the 1990s, although you may still find it occasionally in old stock.
The use of asbestos in various roofing materials in low concentrations (typically trace to 5%) was common until the early 1980s. Asbestos-containing products included asphalt shingles and flat roof membranes, roofing felts, roofing tars, and sealants, and flashing. The use of asbestos in roofing materials on a smaller scale persisted into the 1990s.
Vermiculite itself is not an asbestiform mineral; however, much of the vermiculite insulation sold in North America until 1990, under the brand Zonolite, came from a mine in Libby, Montana that also contained seams of amphibole asbestos. As a result, Libby vermiculite was often contaminated with asbestos. The mine was shut down in 1990. By that time, Libby vermiculite had been installed in the attics of hundreds of thousands of homes across North America. Not all vermiculite contains asbestos. The concentration of asbestos in vermiculite is generally very low. However, asbestos dust associated with vermiculite is so easily made airborne, even trace amounts present an exposure hazard when the product is disturbed. If you are considering an energy audit, do not perform a blower-door test if you have vermiculite!
There are various helpful websites on the internet where you can look up information and photos for older products or materials to find out if they were known to contain asbestos. As with all things on the internet, search multiple sources and carefully consider the information before deciding. Start with government or reputable NGO sources.
A commonly quoted comparison on the size of individual asbestos fibers is that they can be 700 times smaller than human hair. This fact means that the naked eye can't see them and can stay suspended in the air for extended periods (up to 72 hours). As a result, the primary route of human exposure to asbestos is inhalation. This inhalation leads to the diseases commonly associated with asbestos, which include:
The period between the end of exposure and disease recognition and diagnosis can be decades.
The severity of lung function impairment from asbestosis depends on the level of exposure to asbestos fibers. It is typically a slowly progressive disease, and there is no cure aside from a lung transplant. Mesothelioma is an aggressive form of cancer with no cure. Life expectancy after diagnosis typically ranges from 14 to 22 months. Lung cancer has a longer, though still short, life expectancy after diagnosis. It ultimately results in the most deaths of all asbestos-related diseases. Smoking and asbestos exposure have a stacking effect on lung cancer death rates. This fact means that the lung cancer death rate from the combination of smoking and asbestos exposure is higher than the sum of the two.
Understandably, the thought of having a substance in your home that could be invisible when airborne and is associated with terminal diseases that may not be diagnosed for decades after exposure can be frightening. However, just because we may have asbestos-containing materials in our homes does not mean we should immediately tear them out. Removing these materials improperly actually presents a far greater exposure risk than simply leaving them in place.
It is important to remember that asbestos-related diseases mainly affect workers (and sometimes the members of their household) who have had elevated and long-term exposure to airborne asbestos. Living or working in a building with asbestos-containing finishes or other components will not significantly increase a person's exposure risk, provided materials are maintained in good condition. This is the position generally taken by the various levels of government that have jurisdiction over asbestos management in North America. This stance is based on the broad range of asbestos research conducted over the years.
But, what constitutes "good condition," you may ask? Regular wear-and-tear is ok. A few dings in the walls or a bit of loose plaster or texture coat on the ceiling does not represent an immediate exposure hazard. Do the general maintenance that is good to do anyway to keep a home in shape, such as occasional painting and patching to keep wall and ceiling finishes sealed. If you have old exposed and damaged pipe insulation in your basement and suspect some of it may have fallen and left debris, limit the use of that area. Then arrange for the material to be tested for asbestos (we'll discuss that a bit further shortly). Depending on the test result, have the material cleaned up by a qualified asbestos abatement contractor.
If you suspect you may have vermiculite insulation in the attic, don't use it for storage or other purposes. Don't let children enter the attic. Consider caulking gaps and holes in ceilings (e.g., around light fixtures and the attic hatch) and walls (e.g., around electrical outlets) where vermiculite may have fallen.
The extra thinking (and money) that homeowners may need to put in to deal with asbestos comes into play at renovation time or when home maintenance is required, which could disturb asbestos. If it could be disturbed (vibrated, removed, etc.), it should be removed by an appropriately trained, experienced, and insured abatement contractor.
Asbestos abatement is expensive. As with any other contractor, get more than one quote if you can. Also, it is good to know whether the materials requiring disturbance actually contain asbestos.
The most sure-fire way to determine if a material contains asbestos is to have it tested by a laboratory. The laboratory should be appropriately accredited to conduct asbestos analysis. Examples of common accreditation programs include the National Institute of Standards and Technology (NIST) National Voluntary Laboratory Accreditation Program (NVLAP) and the American Industrial Hygiene Association (AIHA) Bulk Asbestos Proficiency Analytical Testing (BAPAT) Program. Except for vermiculite, the sample does not need to be very large. Contact the laboratory to obtain sampling instructions.
Depending on how many materials you need to sample and in how much of a hurry you are, the cost for asbestos samples can add up as well. There are a couple of approaches you can take to narrow things down. For jobs you plan to do yourself, government websites can be a good resource for general information on asbestos-containing materials, which may be sufficient for your purposes.
If you hire a contractor to do a small job, ask them when they visit your home to quote what materials they will need to disturb and target those. You can take a similar approach for bigger jobs. Ask the general contractors bidding on your project whether there are any materials they are concerned may contain asbestos and, if so, what they would propose to address the concern (e.g., arrange for asbestos sampling or abatement). The associated costs and impacts to the schedule can then be built into their quote. When in doubt, get it tested.
Asbestos removal operations are classified as low, moderate, or high-risk work procedures. Which kind of operations fall into which of these categories may vary slightly between jurisdictions. In addition, asbestos regulations often don't apply specifically to single-family dwellings. However, experienced asbestos abatement contractors that do single-family residential work will often also work in commercial and larger residential buildings. In those types of buildings, regulations typically prescribe how to classify and conduct asbestos work. In other words, a good contractor should know and follow the same procedures when working in your home that they would in different types of buildings. Abatement contractors should be able to provide copies of asbestos training records for their workers. They should carry liability insurance specific to asbestos abatement.
Generally speaking, low-risk operations are those that will be done using hand tools and will only disturb asbestos-containing materials that are not easily crumbled or powdered by hand pressure (non-friable materials). Vinyl floor tiles and drywall with asbestos-containing joint compound are examples of non-friable materials. For these operations, contractors will employ disposable drop sheets and may wear disposable protective suits and respirators.
Medium-risk operations are typically required when disturbing small quantities of friable (easily crumbled) materials. These include items like sections of pipe insulation or when using power tools attached to a HEPA filter-equipped vacuum that might disturb non-friable materials. For these operations, they may set up a temporary enclosure. For pipe insulation, a glove bag may be installed around the material to be removed. A glove bag is a durable, transparent plastic bag with built-in gloves, as implied in the name. They use the bag to surround the pipe insulation that will be removed and seal it with duct tape. Workers can then work from outside of the bag to remove the insulation using the built-in gloves.
High-risk operations are required when removing more significant quantities of friable materials or disturbing non-friable materials using power tools that are not attached to a HEPA vacuum. For these operations, an enclosure equipped with a shower is constructed. Then the workers must maintain a specific negative air pressure inside the enclosure. Workers must wear protective suits and full-face respirators.
The asbestos-containing materials should be regularly misted with a dilute water-surfactant solution to control dust in all operations. Other trades should not work in the same area while abatement is taking place.
Although the use of asbestos in new home building products is quite rare (and prohibited depending on your jurisdiction), asbestos-containing building materials may be present in many older homes. However, the likelihood of harmful exposure is very low, provided they are kept in good condition and not disturbed. The removal and disposal of asbestos-containing materials from your home should be conducted by properly trained, experienced, and insured professionals. The cost of this abatement work can be high. So, you should factor it into your renovation budget if your home was built when asbestos use was prevalent, or you come across some suspicious-looking materials.
Daniel Smith is a professional engineer with over 16 years of experience in consulting and industry, the past 11 of which have been spent consulting in environment, health and safety (EHS) and occupational hygiene. Daniel’s main areas of practice have been in hazardous building materials management and indoor air quality, serving the municipal, institutional, construction, real estate management, and financial sectors.