Have you heard of polyurethane? You may be resting your head on it every night. Or it might be keeping your home warm in winter or cool in summer as attic insulation.
The polyurethane foam (PU) found in pillows or home insulation are just two of the many uses of this fossil fuel-derived product. Because it is so common, you may want to know whether it’s toxic or not.
Unfortunately, companies don’t have to prove their products are non-toxic before launching them in the marketplace… which means it’s totally up to you to do the toxic sleuthing on your own.
To help you in your toxic chemical tracking on polyurethane, I looked closely at PU from its laboratory birth to its (usually) landfill or incinerator death. I examined PU for its potential health and environmental impacts at each step of its life cycle, and I’m giving you all of the necessary info here.
If, based on the information presented in this article, you conclude polyurethane is too toxic for you and your family, check out our list of PU alternatives below. (And if you’re not interested in the more “scienc-y” parts of how PU is made, just scroll down!)
Table of Contents
- What is Polyurethane?
- How is Polyurethane Formed?
- What are the Properties of Polyurethane Foam?
- What Products are PUs in?
- Is Polyurethane Spray Foam Toxic?
- Is Polyurethane Safe?
- Tips for Reducing Harmful Exposures to PU Chemicals
- Is Polyurethane Leather Toxic?
- How is PU Leather Made?
- Dimethylformamide (DMF) in PU Leather Manufacturing
- PBDEs in PU Leather
- Antimicrobials in PU Leather
- Plasticizers in PU Leather
- PVC Leather
- Vegan Leather
- What are Polyurethane Poisoning Symptoms?
- Is Polyurethane Carcinogenic?
- Can Polyurethane Be Recycled?
- How is PU Recycled?
- Alternatives to Polyurethanes
- Key Takeaways on Polyurethanes
What is Polyurethane?
Polyurethane (aka PU, or sometimes PUR) is the generic name for a large number of different plastic polymers featuring a urethane (carbamate) linkage. Unlike most types of plastic, which are formed by specific chemicals (and only those specific chemicals), such as polystyrene (#6 plastic) or polypropylene (#5), there are dozens of chemicals that can be used to make polyurethanes.
These chemicals fall into two broad classes: polyols and isocyanates. Let’s talk about each of these.
Notice the -ol ending on the word polyol? That’s the clue signifying that polyols belong to the chemical family called alcohols. Ethanol in beer or biofuels are well-known examples of alcohols.
The prefix poly– indicates there are more than one hydroxyl (-OH) group in the chemical. To make polyurethanes, alcohols with two or three hydroxyl groups are used. They’re also called diols or triols, respectively.
Most of the time, two different polyols are present in a reaction vessel to form PU. They’re partly responsible for some of the physical characteristics of polyurethanes, such as being foamy or rigid, flexible or strong.
The hydroxyl groups are the sites of chemical action when polyols combine with isocyanates to form polyurethanes.
Some common polyols used to make PUs include 1,4-butanediol or 1,6-hexanediol.
The other major chemical class needed to create polyurethanes is called isocyanates. Their claim to fame is not as glamorous as beer or biofuel, however. In fact, it’s deadly.
Notice the root word –cyan– in isocyanates? Like in cyanide poisoning?
Many isocyanates are extremely flammable poisons. They can irritate skin, eyes, and mucous membranes. In the presence of water, they generate toxic fumes made of volatile organic compounds. If heated high enough, they decompose into toxic nitric oxides and cyanide fumes.
The most common isocyanates used to make PUs include:
- Toluene diisocyanate (TDI)
- Methylene Bisphenyl diisocyanate (MDI), also called Diphenylmethane diisocyanate
- Hexamethylene diisocyanate (HDI)
- Naphthalene diisocyanate (NDI)
All of these chemicals are toxic. Even the Communications Workers of America (CWA) warns its members to take precautions when working around them in the telecommunications or automotive industries. They state TDI is the most toxic of all the isocyanates used to make polyurethanes.
If you think toxic isocyanates could be a reason why urethanes made with them could also be toxic, you’d be right. To avoid repetition on this point, check out my article on thermoplastic polyurethanes, where I discuss this aspect of the toxicity of PU in greater depth. (In a later section of this article, I’ll highlight yet other ways PUs are toxic.)
How is Polyurethane Formed?
To make polyurethanes, diisocyanates or triisocyanates are used with two or three N=C=O groupings each, respectively. (The capital letters stand for atoms of nitrogen, carbon, and oxygen. The lines represent their connections.) Polyols with two or more hydroxyl groups are added to them.
Here is a schematic of how polyurethanes are produced:
Special urethane (carbamate) linkages in polyurethanes join repeating and alternating polyols and isocyanates together. Reactions occur at both ends of both of the molecules. If there are three isocyanate or hydroxyl groups in either one, cross linking occurs. An inter-connecting polymer lattice forms in that case.
When the crosslinks are chemical and numerous, thermoset polyurethanes result. The strong connections mean the PUs won’t melt under high temperatures—although they will burn or char. Most PUs are thermoset plastics.
However, when the crosslinks are physical and less prevalent, thermoplastic polyurethanes (TPU) result. Weaker connections between molecules translate into quick melting when these urethanes are exposed to high heat.
Blowing Agents in PU Foams
Most PUs that are commercially produced today are foams. To make polyurethane foam, a blowing agent is required during the polymerization reaction. These blowing agent chemicals control bubble formation during the polymerization reaction. Open- or closed-cell foam structures result from the action of blowing agents. Carbon dioxide or water are common blowing agents.
Ozone layer-depleting chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), or hydrofluorocarbons (HFCs) may be used as well in some countries. Despite the Montreal Protocol that bans some of them, the ozone hole is only slowly shrinking. In 2021, it was larger than usual. As a result, more harmful UV radiation reaches Earth’s surface.
All of these substances are also potent greenhouse gases with global warming potentials (GWPs) up to 14,000 times as powerful as carbon dioxide in heating the planet. Unsurprisingly, these blowing agents supercharge the climate crisis. Unfortunately, they persist in the atmosphere for hundreds of years, wreaking havoc as long as they’re present.
Azodicarbonamide—the “yoga mat chemical“—is another blowing agent to make polyurethane foams. Banned in some countries as a food additive, there are reports that azodicarbonamide as a blowing agent can lead to respiratory problems in exposed workers.
What are the Properties of Polyurethane Foam?
By carefully controlling the relative amounts of polyols and isocyanates under varying experimental conditions, scientists create PUs with certain desired characteristics.
Just as there are dozens of different polyols or isocyanates that could be selected to form a particular polyurethane, there is a wide range of physical properties that could result. Some of the major characteristics include:
- Water resistance
- Temperature resistance
- Flame resistance
- Thermal insulation
What Products are PUs in?
There are so many products containing PUs that only a partial listing is feasible. Here are some of the main categories of consumer goods made with PUs.
- Medical devices
- Car parts
- Floor coatings
- Artificial leather (more on that below)
- Building insulation
Here’s a pie chart that shows the relative percentages of all the major types of polyurethanes:
Is Polyurethane Spray Foam Toxic?
According to the U.S. Environmental Agency (USEPA), spray polyurethane (PU) foam can be toxic. The isocyanates are particularly worrisome.
USEPA states: “Exposure to isocyanates may cause skin, eye and lung irritation, asthma, and ‘sensitization.’ Isocyanates are irritants to the mucous membranes of the eyes and gastrointestinal and respiratory tracts. Direct skin contact can also cause marked inflammation.”
The USEPA also cautions spray foam appliers to be aware of other possible proprietary components in this PU product that “…may vary widely from manufacturer to manufacturer…Amine catalysts may be sensitizers and irritants that can cause blurry vision (halo effect)…Flame retardants, such as halogenated compounds, may be persistent, bioaccumulative, and/or toxic chemicals…Blowing agents may have adverse health effects…Some surfactants may be linked to endocrine disruption.”
Is Polyurethane Safe?
Since there are so many different polyurethanes (PU), it is not possible to make a blanket statement that all PUs are safe. Some PUs, such as spray foams, are not safe, even according to the U.S. Environmental Protection Agency.
There’s always a concern about hazardous residual contaminants on PU final products. Because they are so numerous—including flame retardants, phthalates, diisocyanates, and DMF (as I’ve explained elsewhere in this article), it’s difficult to conclude if the PU product these chemicals are on/in is safe.
If something containing a polyurethane was totally encased by a non-toxic substance and was shown not to off-gas, it’s more reasonable to conclude that particular PU is safe. But whether this ever could happen in real life is questionable.
Tips for Reducing Harmful Exposures to PU Chemicals
Here are some tips that will help you be proactive in protecting yourself and your family from exposure to PU chemicals:
- If you have furniture or bedding with polyurethane foam that’s breaking off in bits and pieces, contain it with a secure, non-toxic cover or dispose of it immediately.
- Buy pre-owned PU products only if they are in good shape. Avoid items with tears or holes through which chemicals can leak out.
- Dust and vacuum (preferably with a HEPA filter) PU furniture weekly (or even more if possible). Do the same to the floors and carpet around it, especially if you have young children.
- When a PU item has come to the end of its useful life, dispose of it properly. Purchase non-PU replacements from our recommended list in this article.
Is Polyurethane Leather Toxic?
These days, a lot of vegan leather fashion items are made out of PU.
There’s no question that the chemicals traditionally used to tan animal leather—chromium and azo dyes especially—make it toxic. Since polyurethane (PU) leather is not treated in the same way as animal skins, you may think PU-based faux leather is non-toxic. However, there are other reasons why PU vegan leather is toxic.
As we’ve described above, PU is made of fossil fuel-derived polyols and isocyanates. You can never be sure which ones are used in a particular PU product because manufacturers aren’t required to tell you.
Material safety data sheets (MSDS) may give you some idea, but they do not have to provide a complete list of chemicals. (There is very little regulation on the chemicals that can be used on clothing and accessories.)
Although the final PU product may be considered non-toxic or chemically inert, the presence of residual polyols or isocyanates as contaminants could be hazardous if you breathe them in or touch the foam.
How is PU Leather Made?
During the manufacture of PU leathers, polyurethane is applied as a coating to another material serving as the backing. Usually, it is a synthetic textile, such as polyester. The chemical most often used to perform this attachment is highly toxic.
Dimethylformamide (DMF) in PU Leather Manufacturing
To make PU leather, polyurethane is typically dissolved in toxic dimethylformamide (DMF). Incidentally, DMF is also widely used to make synthetic clothes such as sportswear containing spandex.
Some PU manufacturers are developing non-toxic methods to make this faux leather and synthetic clothes, but DMF is still the most common solvent used today.
DMF is a hazardous chemical to work around. It is easily absorbed through the skin and respiratory tract. Some of the negative health effects of DMF include:
- Liver and kidney damage
- Reproductive toxicity
- Cell death
- Gut microbiome alteration
- Endocrine disruption
Unfortunately, DMF used in PU leather manufacture doesn’t stay in the lab, where it can adversely affect workers. Residual DMF left on products provides a direct exposure route to unsuspecting shoppers.
In one study analyzing random samples of PU gloves found for sale in the marketplace, the gloves contained 49-10,000 ppm of DMF. The recommended occupational exposure limit is five times below that lowest measurement (49 ppm). On the high end, what the gloves contained (10,000 ppm) was almost 600 times above the long‐term occupational exposure limit.
This study might be reason enough to avoid PU leather completely.
PBDEs in PU Leather
But if you’re not yet convinced that PU leather is toxic, the additives could be highly toxic, too. For instance, PU leather—as well as the foam underneath it in a piece of furniture—could have been treated with flame retardants, especially PBDEs. As explained in our article on flame retardant laws, PBDEs are known endocrine-disrupting chemicals. Some are associated with cancer.
Antimicrobials in PU Leather
Other additives that PU leather could contain are antimicrobials.
As I explained in another article, antimicrobials in clothes and other products often contribute to increasing antibacterial resistance. (This basically means when you’re sick with a serious bacterial infection, normally life-saving antibiotics may not help you.)
Plasticizers in PU Leather
The soft, supple characteristics of PU leather may be due to added plasticizers. Most plasticizers used commercially today are endocrine-disrupting phthalates. These toxic chemicals may be absorbed through the skin upon contact.
If leather made of polyurethane can be toxic, it’s a sure bet that PVC-based faux leather is toxic, too. As I’ve discussed in a previous article, PVC is one of the most toxic materials on Earth from cradle to grave.
There are many companies claiming to sell vegan leather. While they may incorporate some natural materials (such as Pinatex pineapple leather or apple leather), there is almost always a fossil fuel-based component, too. Usually, it is polyurethane.
While their products are technically vegan, this doesn’t mean they are non-toxic. If the PU had been manufactured with DMF or a similarly toxic solvent such as dimethylacetamide (DMA), there could be residual contamination on the final product. Likewise, flame retardants or antimicrobials are likely present. Be especially wary of foreign-made goods, which are more likely made under little or lax regulation (although that’s not always the case and depends on many factors).
To the best of my knowledge, the only vegan leather on the market today that contains no fossil fuel-derived materials is in products made with Mirum by Natural Fiber Welding.
What are Polyurethane Poisoning Symptoms?
Breathing polyurethane (PU) vapors or coming in skin contact with paints, coatings, or varnishes containing PU may result in your experiencing polyurethane poisoning symptoms. When in doubt, contact your local urgent care or hospital. In an emergency contact The Poison Control Center. Their toll-free number is 800-222-1222.
According to Mount Sinai Hospital, polyurethane poisoning symptoms when you swallow it include:
- Loss of vision
- Severe pain in the throat
- Severe pain or burning in the nose, eyes, ears, lips, or tongue
- Blood in the urine
- Kidney failure
- Breathing difficulty
- Throat swelling
- Rapidly developing low blood pressure
- Impaired memory
- Loss of coordination
- Sensation of being drunk
- Severe brain damage
- Walking difficulties
- Blood in the stool
- Burns in the esophagus
- Abdominal pain
- Vomiting blood
If you encounter any of these symptoms from swallowing polyurethane, drink water or milk, unless a medical professional tells you not to. However, do not drink anything if you cannot swallow due to vomiting, convulsions, or stupor.
If you breathed in polyurethane fumes from varnish and experienced any of the listed poisoning symptoms, go outside immediately.
If polyurethane touches your skin or eyes, poisoning symptoms you may experience include burns, inflammation, or irritation. Rinse or flush the PU off quickly with copious amounts of water for 15 minutes. Seek medical care as soon as possible.
Is Polyurethane Carcinogenic?
According to the polyurethane (PU) industry, their products are not carcinogenic. A study following the health of PU factory workers generally supported this conclusion. However, the study pointed out that it was one of three studies of female workers who had an elevated risk of lung cancer.
Certain isocyanates commonly used to make PUs are known to cause cancer in lab animals. They are classified as potential human carcinogens. For example, the U.S. National Toxicology Program stated in its review that toluene diisocyanates are “reasonably anticipated to be human carcinogens.”
Chemicals frequently added to PUs, such as many flame retardants, are known carcinogens. Companies aren’t required to tell you which specific chemicals have been applied.
Some PUs may have had endocrine-disrupting plasticizers applied to their surfaces to make them less rigid. Manufacturers claim this information is proprietary and won’t tell you. Certain phthalate plasticizers have been banned in some countries because of their carcinogenicity. For example, there is an association between phthalates and breast cancer.
As discussed earlier in this article, the solvent DMF used to make PU leather and clothes has been known to cause cancer in exposed workers. Residual DMF could be present on the surfaces of these products.
Can Polyurethane Be Recycled?
Although there is some ongoing research into recycling polyurethanes, only a few pilot plants in the world actually transform used PUs into reusable products. A handful of places recycle PUs on a commercial basis, but they aren’t equipped to deal with the nearly 26 million tons of PUs created every year.
While all components of polyurethanes may be downcycled and incorporated into lower quality goods, some companies are focused on recapturing only certain chemicals used to make it. For example, Dow is developing a process to incorporate up to 50% of captured polyol to make rigid foam and up to 30% for flex foam. This means the majority of polyol to make repurposed PU will still come from virgin petroleum stock.
How is PU Recycled?
Because companies won’t divulge their process of restoring all or part of polyurethanes, it’s only possible to provide a brief sketch of what actually happens in a PU recycling plant. This summary is surmised from the known chemistry of the molecules making up PUs:
- Soaking polyurethanes in ethylene glycol
- Heating the mixture at approximately 536°F for 4-5 hours, breaking the PUs down into smaller molecules
- Separating the mixture components via distillation
- Purifying the recovered chemicals
- Packaging the used chemicals for resale
Because fossil fuels are comparatively cheaper than what it costs to recycle PUs, companies lack an economic incentive to recycle them. They prefer to manufacture brand-new (clean) PUs.
An added concern has to do with shopper preferences and expectations. People aren’t willing to buy pre-owned PUs due to possible odor, discoloration, imperfections, age, and lack of knowledge about their history.
As a result, tens of millions of tons of PUs in consumer goods are tossed into landfills or incinerators every year. In landfills, toxic leachate can contaminate groundwater. By burning PUs in incinerators, toxic airborne chemicals can be released, contributing to air pollution. In some cases, further destruction of the Earth’s ozone layer and the climate results.
When PUs are recycled, they are incorporated into inferior quality products such as pillow fill or carpet underlayment.
Alternatives to Polyurethanes
Fortunately, there are plenty of alternatives to PUs on the market today. You may not be able to find replacements for everything, and it’s unrealistic to think you can do so overnight. I recommend that you use what you have until it reaches the end of its useful life before you replace it with these eco-friendly polyurethane options. Here are a few of our favorites to get you started:
- Buckwheat hull or organic cotton pillows
- Wool carpet
- Cotton or natural exercise/yoga mat
- Latex mattresses
- Vegan leather goods
Key Takeaways on Polyurethanes
Polyurethanes (PU) is the name for a large family of mostly thermoset plastics made of two types of fossil fuel-derived chemicals: isocyanates and polyols. The particular chemicals used determine the characteristics of the final PU products. Foam and rigid board are the most common.
Although polyurethane foam is generally considered inert, some of the chemicals used to make it are not. There could be residual amounts of the starting chemicals present in the resulting PUs.
If you’re exposed to them, you could experience negative health outcomes including respiratory or skin problems, or worse.
What is more concerning about PUs are some of their chemical additives. Flame retardants belonging to the PBDE family of chemicals are the most serious because they are known endocrine disruptors and carcinogens. While many of the most hazardous flame retardants have been banned in the U.S., they are used elsewhere in the world. Shoppers should be wary of imported goods made of PUs.