Is It Dangerous to Breathe In Insulation?

We’ve improved from the days of dangerous asbestos, but many people still wonder just how dangerous fiberglass insulation is.

And, is it dangerous to breath in fiberglass insulation? There is no conclusive evidence that inhaling fiberglass insulation fibers causes cancer in humans. Fiberglass generally causes irritation in the respiratory system, but most people recover from inhaling fiberglass fibers. A small percentage of fiberglass fibers can reach the lungs, but most of those fibers are dissolved and removed by the body within 10 days of exposure by inhalation.

But before you can even assess how dangerous fiberglass insulation is for your health, you have to know what’s in it.

Only by knowing its ingredients will you be able to understand the impact on your health.


What Is Fiberglass Insulation and What’s In It?

Fiberglass insulation is a woven plastic material that’s filled with small glass, or silica, fibers. The glass fibers come from melting sand and glass at high temperatures, then spinning them at high speeds while they cool off. There are also other chemicals inside that are used to thicken the insulation by curing it with a polymer, called binders.

Just until recent years, fiberglass insulation contained formaldehyde as a binder, which is a carcinogen (cancer-causing) and dangerous volatile organic compound (VOC). Now, apparently more safe organics and chemicals are used as binders.

Nowadays, polyacrylic and polyol polymers (such as glycerol) are common, although there are also some marketed as “natural”, “environmentally friendly”, or “bio-based”. Those usually contain sugars, fats, and proteins. Owens Corning, for example, markets theirs under the Eco-Pure and Eco-Touch labels.

There is another VOC, however, that’s used in resins for fiberglass insulation – styrene. More on that later.


How Dangerous Is Fiberglass Insulation If Inhaled?

Fiberglass was previously listed as a carcinogen, but this information has been removed from Prop 65 labels as of 2011 due to inconsistent test results across the various types of fiberglass insulation products. There are some animal studies showing that fiberglass insulation can cause cancers like respiratory system cancer and mesothelioma. Whether the cancers were caused by inhaling the fibers or by directly injecting them into the animal subjects, however, is hotly debated.

There is no clear evidence as of date that fiberglass causes cancer in humans. Organizations that are responsible for its classification usually use vague terms like “probable” or “possible” carcinogen to get around it. And even then, this applies to only a small subset of fiberglass products. They also use the aforementioned flawed animal studies as a factor in their classification rather than just human studies.

As far as human studies, there is no significant link to cancer even in workers who were occupationally exposed to fiberglass for many years. Those studies that showed higher than usual rates of lung cancer were often found to have been conducted on cohorts that included smokers.

Cancer studies aside, fiberglass insulation is still dangerous in other ways, though.

The styrene in the resin can cause a devastating lung disease called bronchiolitis obliterans. Although, this disease is extremely rare and more likely in fiberglass factory workers.

For most of us average homeowners and occasional remodelers, it’s important to note that glass fibers are considered an inhalable and respirable fiber. Some can also be biopersistent.

Let’s define all those terms.


Fiberglass Particles Are Both Inhalable and Respirable

A particle that can enter the upper respiratory system is considered inhalable. If it can go beyond that and reach the lungs and alveoli in the lungs, it’s also considered respirable.

In other words, fiberglass particles fall in the range of particle sizes that make it both inhalable and respirable.

Fine fibers typically have varying diameters of 1 to 10 micrometers (μm) wide and can be up to 30 to 50 μm long, according to the US Department of Health and Human Services (USDHHS), although some manufacturers make fibers larger than that.

Thinner and shorter particles can’t travel far enough to get to the lungs. So the thinner, shorter glass fibers (less than 2 μm in diameter, and even some up to 4 μm) tend to stay in the upper respiratory tract and be exhaled out. However, if the particles are longer, they can get to the alveolar regions and become toxic (15 μm or longer).

If all this sounds too complicated, know this –

Only a small fraction of glass fibers are respirable because manufacturers deliberately break them up to make them shorter. In other words, most of the fiberglass fibers won’t reach your lungs and will be quickly inhaled and exhaled out.

The others are just inhalable and don’t cause any risk of cancer. The California Prop 65 label was also updated to more realistically reflect this fact.


Fiberglass Insulation Particles Have Low Biopersistence

A biosoluble fiber dissolves in the lungs and can readily leave.

But a biopersistent fiber doesn’t dissolve in the lungs immediately and stays.

Fiberglass is biopersistent in the lungs and trachea, specifically. Take this with a caveat, though – only a small percentage (about 1%) of fiberglass particles are biopersistent, according to the National Insulation Association.

The graph below shows just how long fiberglass stays inside a person’s body. While longer fibers have a greater chance of getting into the lungs, they are dissolved more quickly compared to shorter fibers. In this study, fibers longer than 20 μm were mostly gone before 50 days after inhalation, while shorter fibers took upwards of a full year.



Despite this graph appearing daunting, fiberglass insulation has a low biopersistence. The larger timelines on this graph represent special glass fibers, which are not used in insulation. In fact, the typical fiberglass insulation dissolves within 10 days (compare this to over 5,000 days for asbestos insulation of the past).


Symptoms of Inhaling Fiberglass Insulation

Now that you know about what fiberglass is and how long it stays in your body, you’ll have to be aware of its symptoms on the body.

When inhaled, fiberglass particles cause irritation of the throat, mouth, and nasal passages, causing you to cough. Nose bleeds can also occur.

Regular exposure can cause asthma. Because this is usually occupational, it’s typically referred to as construction workers asthma. Those who have existing asthma or bronchitis will see their condition worsen if exposed to fiberglass in the air.

There are ways obviously that your body can be affected as well. Swallowing fiberglass particles causes stomach irritation. Touching or rubbing your eyes will cause skin and eye irritation.

If the fiberglass insulation has been installed in a humid basement or room and is exposed, you may notice mold develop on it over the years. Fiberglass itself is mold-resistant, but the resins and other components of it are not. If this is the case, understand that you’re possibly inhaling mold as well as exposed fiberglass fibers.

The body’s immune system is quick to react to mold. You may notice similar symptoms as mentioned for fiberglass above. In addition, a runny nose, sneezing, shortness of breath, and chest tightness may occur.