A tabletop with a stethoscope above magnet letters spelling out 'carcinogenic'

Insulation is one of the essential aspects of home building. Moreover, it has a massive impact on our energy bills. First, however, it is crucial to check if the insulation is safe to use. 

Some types are carcinogenic, meaning they can cause cancer. This is especially true when you are exposed to them for an extended period.

In this article, we look at some popular types of insulation to determine if they are carcinogenic. Continue reading to learn more about keeping your home safe from carcinogenic insulation. 

Is Insulation Carcinogenic?

Some types of insulation can be carcinogenic—and it’s not just fiberglass insulation or the dreaded asbestos that present a risk. Fortunately, most kinds of insulation are only dangerous if they are exposed, damaged, ingested, breathed in, or not correctly installed.

Put simply, with the proper care, you can effectively keep your pipes toasty and your loved ones safe. 

Let’s look at some common types of insulation to understand if they are hazardous or carcinogenic. 


Fiberglass is a suspected carcinogen. Particular studies on animals revealed a higher risk of cancer when fiberglass fibers were implanted in the lung tissue of rats.

However, such studies are not widely accepted because of how the fibers were implanted. Thus, the jury is still very much out regarding cancer risk in humans. 

For instance, a 1988 report from the International Agency for Research on Cancer (IARC) provided the primary evidence for a potential link between cancer and fiberglass in animals. However, after decades of research, medical professionals have concluded no correlation between cancer and fiberglass.

When the report was updated in 2002, it revealed there was insufficient evidence of fiberglass insulation causing cancer in humans and only limited evidence of any effect in animals. It also stated that “glass wool,” a fiberglass kind, is not categorizable as a human carcinogen.

On the other hand, the National Toxicology Program’s fifteenth Report on Carcinogens lists glass fibers as “reasonably anticipated to be a human carcinogen.” This designation indicates some evidence of fiberglass leading to cancer, but there’s no sure proof of an impact on humans. 

In addition, the National Academy of Sciences reviewed studies of fiberglass manufacturing employees in 2000. It concluded that “glass fibers do not appear to increase the risk of respiratory system cancer.”

All in all, deaths due to lung diseases, including mesothelioma and lung cancer, in groups of workers involved in manufacturing glass wool are not different from the overall US general population. 

A picture of un-faced pink fiberglass insulation batts in the wall, with a man installing it

Thus, while fiberglass insulation might not cause cancer, it can lead to eye, nose, lung, and skin irritation if you touch it or are exposed to it nearby long-term. Therefore, the individuals most likely to be impacted by it are those who install it.

You probably will not suffer from going up into your attic a few times a year. Given all the research, it seems fiberglass poses a minimal danger, if any, to the regular homeowner!

Spray Foam 

Spray foam is an insulation and air barrier material that seals floors, walls, and ceiling cavities against air movement. These areas include spaces around light fixtures and electrical outlets and where the walls meet the doors and windows.

To understand the carcinogenicity of spray foam, we need to understand what it contains. 

Spray foam contains two compounds—an isocyanate and a mixture of additives, polyols, and catalysts. They are mixed at the job site to form hardened insulation. 

If these compounds become unbalanced or if the chemicals are not heated to the right temperature before being sprayed, dangerous chemicals can be released into the air. One particular chemical is phenol-formaldehyde, which replaced urea-formaldehyde when banned in 1928 by the US Consumer Product Safety Commission. 

These days, spray foam mixtures contain formaldehyde that can produce airborne methylene diphenyl diisocyanate (MDI), which the EPA warns against. These chemicals can lead to cancer and contribute to unhealthy air quality.


Asbestos is a naturally-occurring mineral that’s been used in many construction projects due to its fire-resistant properties. However, even though asbestos was once regarded as safe, we now know that it can cause severe health problems to individuals exposed to high levels of it over long periods. 

Asbestos is categorized as a known human carcinogenic by international, federal, and state agencies. Moreover, asbestos inhalation is linked to lung cancer and asbestosis (chronic lung disease).

The EPA banned new uses of the material in 1989. 

Nevertheless, we still often witness asbestos-associated problems, from the evacuation of poorly built school buildings to debris produced from the 2005 Hurricane Katrina in New Orleans. 

A worker in a hazmat suit in an attic handles asbestos insulation

Asbestos-related health risks can take 10 to 40 years to develop. Thus, if you have worked on sites where this material was handled or installed, keep in mind that there can be some long-term impacts. 

If you have been exposed to asbestos and are undergoing symptoms including weight loss, loss of appetite, chest pain, fatigue, and coughing up blood, set up an appointment with a doctor instantly. 

Also, if you find out that you have asbestos in your basement, either through visual inspection or testing, immediately put all the materials into sealed containers and get in touch with a professional to come and remove it. Since asbestos is carcinogenic, we strongly advise you not to remove it yourself. 

Mineral Wool 

Mineral wool, also known as slag wool, stone wool, and rock wool, was one of the first insulation materials to be produced commercially, starting in 1871 in Germany.

Mineral wool lost a lot of its market share when less expensive fiberglass insulation became available. However, the material’s unique properties have led to its comeback in recent years. 

One of the downsides of mineral wool insulation is that mineral fibers can break off and become airborne. Breathing in these fibers can lead to health problems. 

Previously, there were concerns that mineral wool fibers might be carcinogenic, like asbestos. Those concerns have mostly been dismissed. In 2001, the IARC updated the classification of mineral wool from “possibly carcinogenic to humans” to “not classifiable as to its carcinogenicity to humans.”

Nevertheless, the mineral fibers can still prove to be respiratory irritants. Therefore, people installing mineral wool should always wear high-quality dust masks. Moreover, it should be covered adequately with coatings or drywall to prevent the fibers from escaping to the indoor air. 

Another drawback of mineral wool insulation is the binder used to glue the fibers together. Most manufacturers use urea-extended phenol-formaldehyde or a phenol-formaldehyde binder.

Bear in mind that formaldehyde is known to be a human carcinogen, and if a high quantity of it enters the air inside your home, it would definitely be a health risk.

Thankfully, the processing eliminates almost all of the free formaldehyde present in the material. Thus, formaldehyde emissions from mineral wool have minimal levels of formaldehyde. 

Denim Insulation 

Denim insulation is a blend of recycled jeans and post-industrial cotton and denim, not just denim alone. The fabric is shredded and treated with boric acid to make it flame-retardant and mildew, insect, and pest-resistant. 

A half batt of denim insulation on the floor in front of the wall it is installed in

Denim insulation does not contain formaldehyde, and it doesn’t have tiny and itchy fibers that can irritate your lungs and skin, like fiberglass. Moreover, it doesn’t contain any chemical irritants and requires no carcinogenic warning label, unlike some other conventional insulation products. 

Hemp Insulation 

Hemp insulation is a composite material and one that’s very environmentally friendly. Rather than comprising 51% plant fibers and 49% chemicals and plastics, it contains up to 92% hemp and 8% polyester fibers. 

Hemp insulation is regarded as an alternative to foam and fiberglass—one that has minimal impact on the environment during manufacturing. In addition, because hemp is a natural plant product, the insulation offers organic benefits when installed and disposed of. 

The best thing about hemp insulation is that it contains no asbestos, glass fibers, formaldehyde, chlorofluorocarbons, hydrofluorocarbons, or hydrochlorofluorocarbons.

There are no health hazards such as cancer-related warnings associated with its installation. In addition, it doesn’t itch or irritate the skin, as does fiberglass and mineral wool insulation. 

Sheep’s Wool Insulation 

Sheep’s wool is the only naturally-occurring insulating material that helps you stay warm and safeguards you from moisture, heat, and cold. The distinctiveness of raw fiber sheep’s wool makes it an insulation material with one-of-a-kind benefits in its final product. 

Wool insulation begins as sheared wool that grew on sheep but is considered too rough to use for clothing or fabric. 

It’s vital to remember that it is a popular production technique to treat sheep’s wool insulation using additives like boric acid to reduce flammability and repel insects. Manufacturers might also add ammonium sulfates as a fire retarding agent. 

Closeup on the texture of sheep's wool

Thus, while the base material of sheep’s wool is inherently non-carcinogenic and natural, the final product is not entirely free of dangerous toxins. Both the additives used to treat it are poisonous if inhaled and irritate the eyes, throat, skin, and nose. 

In addition, Europe’s Classification, Labelling, and Packaging (CLP) agency classifies boric acid as a reproductive toxin. However, in contrast, the Environmental Protection Agency has categorized boric acid as a Group E carcinogenic, stating that it shows “evidence of non-carcinogenicity” for humans.

Cork Insulation 

Cork insulation generally uses the cork granule byproduct of the cork stopper industry. The granules are steam-heated and pressed into a board, making the cork expand.

This process activates a natural binder known as suberin that fuses the granules—no other chemicals or binders are used in this process.

Therefore, cork insulation is entirely healthy, and it doesn’t contain any added chemicals that can cause cancer—only water and cork are used to manufacture it. Thus, cork insulation has no off-gases. 

Also, its surface doesn’t attract dust and pollutants. It’s naturally antimicrobial and antifungal. At the end of its life, cork insulation will decompose. It will not release carcinogenic microplastics or other synthetic compounds into the air. 

What Is the Healthiest Insulation?

Cork surely tops the list for the healthiest, safest, and most non-carcinogenic insulation, at least according to a report published by Energy Efficiency for All focusing on insulation options for affordable multi-family houses.

Thus, it doesn’t talk about some of the more experimental or expensive options out there. However, cork is a great choice when you factor in both cost and health!

Why Should You Hire a Professional to Install Insulation?

Installing insulation is a tough job. If you try to take it up on your own, even the most natural insulators and best methods can be unsafe and dangerous.

For instance, proper installation of spray foam insulation requires specialized equipment. Improper insulation installation can lead to indoor air pollution and release cancerous fumes because of the chemicals used in the production process. 

A good rule of thumb is that if it looks like a task for experts, it probably is!

Last Few Words

We have come a long way from cancer-causing asbestos insulation. These days, there are plenty of healthy insulation choices, regardless of your budget.

Even the primarily-debated fiberglass insulation is now regarded as non-carcinogenic. Thus, you can wrap your house in a soft pink blanket and not stress about your health.

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