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Polypropylene. It's in so much of what we use in our daily lives. Most of us have probably handled it a few times already today. Because of its relatively low cost and incredible versatility, you can find it in your kitchen (utensils), your closet (athletic clothes), your car (batteries), your food containers (it's recycling number 5), and in a place that few of us might realize: our area rugs and carpets. When something as permanent and in-contact with our physical selves as an area rug is made from something that originates from crude oil, our hackles immediately go up. So the question on any rug buyer's mind is: Is Polypropylene toxic?
Is Polypropylene Toxic?
The question, "Is Polypropylene Toxic?" is a sticky one. If polypropylene has been used in the manufacturing of a rug, then it's very likely several other synthetic components have been used in its manufacture, and those components demand your equal attention as well.
In this post, I am limiting the scope of the discussion to polypropylene only. I will talk about what it is, how it's used, the dangers that are associated with it, and the actions you can take to avoid it or limit its possible effects.
what Is Polypropylene?
Similar to most types of plastics, polypropylene is made from derivatives of hydrocarbon fuels such as petroleum oil. In the case of polypropylene, it is extracted in monomer form (propylene) as a gas from crude oil. It becomes polypropylene (H2C=CHCH3) via chain-growth polymerization. The illustration below shows the polymerization of propylene into polypropylene.
Similar to most types of plastics, polypropylene is made from derivatives of hydrocarbon fuels such as petroleum oil. In the case of polypropylene, it is extracted in monomer form (propylene) as a gas from crude oil. It becomes polypropylene (H2C=CHCH3) via chain-growth polymerization. The illustration below (Courtesy of differencebetween.com.) shows the polymerization of propylene into polypropylene.
Monomer, a molecule of any of a class of compounds, mostly organic, that can react with other molecules to form very large molecules, or polymers. The essential feature of a monomer is polyfunctionality, the capacity to form chemical bonds to at least two other monomer molecules.
Publisher: Encyclopædia Britannica
Date Published: March 05, 2020
Polypropylene (PP) is one of the most difficult plastics to recycle. Recycled PP can be blended with virgin PP at a rate of only 50% maximum. Because it has such a low rate of recyclability, it's most ideal to avoid it entirely.
In its food container forms, it's recommended that you reuse the container as many times as you can before you throw it away. In its rug or carpet form, it's ideal to avoid it altogether for this reason alone.
How is Polypropylene Used in Rug Manufacturing?
A large number of propylene monomers are strung together to form a solid plastic material called polypropylene resin. To create a textile that can be integrated into an end product, polypropylene resin must be mixed with a wide variety of plasticizers, stabilizers, and fillers. Those additives, as well as colorants, are added to the molten polypropylene to give it additional properties that are needed in the end product (it's flexible enough, bulky enough, has the required properties of the end product, its color), the plastic is cooled into bricks or pellets (see photo below of PP pellets).
Textile factories buy the pellets or bricks where they are then remelted. In most cases, this polypropylene is then formed into sheets, or it may be allowed to cool in molds. If sheets are created, these thin fibers (see photo by Zobia Hamid below) are then cut into the desired shape and sewn or glued to create rugs or carpets. Different manufacturing methods are used to form polypropylene into non-rug/carpet products.
What Are the Dangers OF Having a Polypropylene Rug OR Carpet in Your House?
In the case of polypropylene, you are asking the first question, "Is polypropylene toxic?" but you MUST ask the second question that paints a more definite answer as to whether you should consider bringing a polypropylene rug or carpeting into your home.
[GRAY] Answers to the first question, "Is polypropylene toxic?"
First gray answer: The EPA has rated Polypropylene as an "EPA Safer Choice" (The Safer Choice of the U.S. Environmental Protection Agency (EPA) helps consumers, businesses, and purchasers find products that perform and are safer for human health and the environment.) I'm sure I'm not alone not finding pure comfort in something being considered "safer" versus "safe." "Safer" relative to what? Out and out poison?
Second gray answer: According to the U.S. Coast Guard, it has "No apparent toxicity." (U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.) "Apparent" is a very dodgy word. Many times the word "apparent" is used in the context of hindsight. For instance, "the presence of the disease was not immediately apparent."
It's hard to consider those answers conclusive enough when it's the health of you and your family on the line.
[Black and white] Answers to the SECOND question, "Is A polypropylene RUG toxic?"
Altering the question slightly makes a BIG difference in the answer. You can't have a polypropylene rug or carpet with a host of other players getting involved, and those players are known to be toxic. First, we need to take a look at how handmade and machine-made rugs are constructed versus how a synthetic rug (with polypropylene fibers or polypropylene backing) is built.
The anatomy of a handmade rug
While there are different methods to make a handmade rug, the illustration below shows how the threads themselves build the "plane" of the rug.
In this way, the design can be seen through the back of the rug, whether it's handmade or machine made (see the examples below).
The terms "machine-made" and "synthetic" shouldn't be confused.
You can read more about the true adventure that is shopping for a Persian rug in our Ultimate Guide to Buying a Persian Rug. If you know anything by now, it's that the BACK of the rug tells the whole story - if it's synthetic, handmade or machine-made!
The anatomy of a Synthetic rug
The synthetic rugs that we want to avoid are the ones that pair polypropylene fibers (tuft) with dangerous backings and adhesives (see the illustration below).
If the back of a polypropylene rug looks like the one below, you're in a dangerous gray area - what has been layered into that backing?
Take a deep breath and get ready to see a frightening graphic that shows you all the possible toxicity involved...
Terrifying, but informative...
Here is an incredibly informative graphic that outlines the 44 (yes, that reads FORTY-FOUR) hazardous substances in carpet and synthetic rugs. I urge you to read the full paper - the citation is below the graphic.
TY - BOOK
AU - Vallette, Jim
AU - Stamm, Rebecca
AU - Lent, Tom
PY - 2017/10/01
T1 - Eliminating Toxics in Carpet: Lessons for the Future of Recycling. An Optimizing Recycling Report by the Healthy Building Network
DO - 10.13140/RG.2.2.14204.03200
Is polypropylene toxic?
Well, if it's part of a synthetic rug or carpet, there is a mind-numbing number of toxic substances that might have been added to it, sprayed on it, adhesed to the back of it. It's all in the phrasing. If polypropylene is present, then there is a high likelihood that the toxins referenced above are present.
What is the Best Way to Have Total Peace of Mind?
Ideally, the best way to avoid any risk of possible negative side effects of polypropylene in your living space is to avoid it entirely. Then the question "Is Polypropylene toxic?" and its gray, murky answer doesn't have to live in the back of your mind while your baby is crawling on the rug, reaching for her toy. Never buying it in the first place compounds that peace of mind because you've avoided adding polypropylene rugs to the waste stream where its capacity to be recycled - altogether or in your area - is questionable at best.
Recycled PP can be blended with virgin PP at a rate of only 50% maximum. 🙁
What is the Next Best Way to Have Peace of Mind?
The fact is that many of us have rugs or carpets in our homes that were in our living spaces before we had the awareness to question their safety or before we were able to prevent their installation. I personally moved into my house four years ago, and it had wall-to-wall carpeting on the first floor and basement, carpeting running up the stairs, and carpeting throughout the upstairs (including my daughters' rooms - one of whom was diagnosed with lymphoma two years ago). We are taking it bit by bit and ripping it out to replace it with wood floors and natural fiber rugs. Renovating our lives to be healthier takes time and money, and awareness is the first step in the process. Baby steps are better than no steps.
Rugs and carpets are materials we live with and touch day in and day out. Making a mindful choice based on research is critical because of the degree and length of time of exposure, which could be years, even decades. To dive deeper into the subject, I've listed links below that are worth your time. If you've seen enough and want to explore alternatives, read our post, Non-Toxic Area Rugs for Your Home.
Have you had any health problems that might be related to the rugs in your living space? Please consider commenting below so we can all learn from your experience.
Sources & Further reading
This post was originally published on November 11, 2020.