Polyester is a very popular fabric choice – it is, in fact, the most popular of all the synthetics. Because it can often have a synthetic feel, it is often blended with natural fibers, to get the benefit of natural fibers which breathe and feel good next to the skin, coupled with polyester’s durability, water repellence and wrinkle resistance. Most sheets sold in the United States, for instance, are cotton/poly blends.
It is also used in the manufacture of all kinds of clothing and sportswear – not to mention diapers, sanitary pads, mattresses, upholstery, curtains and carpet. If you look at labels, you might be surprised just how many products in your life are made from polyester fibers.
So what is this polyester that we live intimately with each day?
At this point, I think it would be good to have a basic primer on polyester production, and I’ve unabashedly lifted a great discussion from Marc Pehkonen and Lori Taylor, writing in their website diaperpin.com:
Basic polymer chemistry isn’t too complicated, but for most people the manufacture of the plastics that surround us is a mystery, which no doubt suits the chemical producers very well. A working knowledge of the principles involved here will
make us more informed users.
Polyester is only one compound in a class of petroleum-derived substances known as polymers. Thus, polyester (in common with most polymers) begins its life in our time as crude oil. Crude oil is a cocktail of components that can be separated by industrial distillation. Gasoline is one of these components, and the precursors of polymers such as polyethylene are also present.
Polymers are made by chemically reacting a lot of little molecules together to make one long molecule, like a string of beads. The little molecules are called monomers and the long molecules are called polymers.
O + O + O + . . . makes OOOOOOOOOOOOOOOO
Depending on which polymer is required, different monomers are chosen. Ethylene, the monomer for polyethylene, is obtained directly from the distillation of crude oil; other monomers have to be synthesized from more complex petroleum derivatives, and the path to these monomers can be several steps long. The path for polyester, which is made by reacting ethylene glycol and terephthalic acid, is shown below. Key properties of the intermediate materials are also shown.
The polymers themselves are theoretically quite unreactive and therefore not particularly harmful, but this is most certainly not true of the monomers. Chemical companies usually make a big deal of how stable and unreactive the polymers are, but that’s not what we should be interested in. We need to ask, what about the monomers? How unreactive are they?
We need to ask these questions because a small proportion of the monomer will never be converted into polymer. It just gets trapped in between the polymer chains, like peas in spaghetti. Over time this unreacted monomer can escape, either by off-gassing into the atmosphere if the initial monomers were volatile, or by dissolving into water if the monomers were soluble. Because these monomers are so toxic, it takes very small quantities to be harmful to humans, so it is important to know about the monomers before you put the polymers next to your skin or in your home. Since your skin is usually moist,
any water-borne monomers will find an easy route into your body.
Polyester is the terminal product in a chain of very reactive and toxic precursors. Most are carcinogens; all are poisonous. And even if none of these chemicals remain entrapped in the final polyester structure (which they most likely do), the manufacturing process requires workers and our environment to be exposed to some or all of the chemicals shown in the flowchart above. There is no doubt that the manufacture of polyester is an environmental and public health burden
that we would be better off without.
What does all of that mean in terms of our health? Just by looking at one type of cancer, we can see how our lives are being changed by plastic use:
- The connection between plastic and breast cancer was first discovered in 1987 at Tufts Medical School in Boston by
research scientists Dr. Ana Soto and Dr. Carlos Sonnenschein. In the midst of their experiments on cancer cell growth, endocrine-disrupting chemicals leached from plastic test tubes into the researcher’s laboratory experiment, causing a rampant proliferation of breast cancer cells. Their findings were published in Environmental Health Perspectives (1991).
- Spanish researchers, Fatima and Nicolas Olea, tested metal food cans that were lined with plastic. The cans were also found to be leaching hormone disrupting chemicals in 50% of the cans tested. The levels of contamination were twenty-seven times more than the amount a Stanford team reported was enough to make breast cancer cells proliferate. Reportedly, 85% of the food cans in the United States are lined with plastic. The Oleas reported their findings in Environmental Health Perspectives (1995).
- Commentary published in Environmental Health Perspectives in April 2010 suggested that PET might yield endocrine disruptors under conditions of common use and recommended research on this topic. 
These studies support claims that plastics are simply not good for us – prior to 1940, breast cancer was relatively rare; today it affects 1 in 11 women. We’re not saying that plastics alone are responsible for this increase, but to think that they don’t contribute to it is, we think, willful denial. After all, gravity existed before Newton’s father planted the apple tree and the world was just as round before Columbus was born.
Polyester fabric is soft, smooth, supple – yet still a plastic. It contributes to our body burden in ways that we are just beginning to understand. And because polyester is highly flammable, it is often treated with a flame retardant, increasing the toxic load. So if you think that you’ve lived this long being exposed to these chemicals and haven’t had a problem, remember that the human body can only withstand so much toxic load - and that the endocrine disrupting chemicals which don’t seem to bother you may be affecting generations to come.
Agin, this is a blog which is supposed to cover topics in textiles: polyester is by far the most popular fabric in the United States. Even if made of recycled yarns, the toxic monomers are still the building blocks of the fibers. And no mention is ever made of the processing chemicals used to dye and finish the polyester fabrics, which as we know contain some of the chemicals which are most damaging to human health.
Why does a specifier make the decision to use polyester – or another synthetic – when all the data points to this fiber as being detrimental to the health and well being of the occupants? Why is there not a concerted cry for safe processing chemicals at the very least?
 Sax, Leonard, “Polyethylene Terephthalate may Yield Endocrine Disruptors”,
Environmental Health Perspectives, April 2010, 118 (4): 445-448