Antimony is used as a catalyst in the production of polyester.
Synthetic fibers are the most popular fibers in the world with 65% of world production of fibers being synthetic and 35% natural fibers.1 Fully 70% of that synthetic fiber production is polyester. There are many different types of polyester, but the type most often produced for use in textiles is polyethylene terephthalate, abbreviated PET. Used in a fabric, it’s most often referred to as “polyester” or “poly”. It is very cheap to produce, and that’s a primary driver for its use in the textile industry.
The majority of the world’s PET production – about 60% - is used to make fibers for textiles; and the rest (about 30%) is used to make bottles. Annual PET production requires 104 million barrels of oil – that’s 70 million barrels just to produce the virgin polyester used in fabrics.2 That means most polyester – 70 million barrels worth - is manufactured specifically to be made into fibers, NOT bottles, as many people think. Of the 30% of PET which is used to make bottles, only a tiny fraction is recycled into fibers. But the idea of using recycled bottles – “diverting waste from landfills” – and turning it into fibers has caught the public’s imagination. There are many reasons why using recycled polyester (often called rPET) is not a good choice given our climate crisis, but for now we’re concentrating on only one aspect of polyester: the fact that antimony is used as a catalyst to create PET. We will explore what that means.
Antimony is present in 80 – 85% of all virgin PET. Antimony is a carcinogen, and toxic to the heart, lungs, liver and skin. Long term inhalation causes chronic bronchitis and emphysema. The industry will say that although antimony is used as a catalyst in the production process, it is “locked” into the finished polymer, and not a concern to human health. And that's correct: antimony used in the production of PET fibers becomes chemically bound to the PET polymer so your PET fabric does contain antimony but it isn't available to your living system. 3
But wait – that’s not all! Antimony is leached from the fibers during the high temperature dyeing process. The antimony that leaches from the fibers is expelled with the wastewater into our rivers (unless the fabric is woven at a mill which treats its wastewater). In fact, as much as 175ppm of antimony can be leached from the fiber during the dyeing process. This seemingly insignificant amount translates into a burden on water treatment facilities when multiplied by 19 million lbs each year - and it's still a hazardous waste when precipitated out during treatment. Countries that can afford technologies that precipitate the metals out of the solution are left with a hazardous sludge that must then be disposed of in a properly managed landfill or incinerator operations. Countries which cannot or which are unwilling to employ these end-of-pipe treatments release antimony along with a host of other dangerous substances to open waters.
But what about the antimony that remains in the PET fabric? We do know that antimony leaches from PET bottles into the water or soda inside the bottles. The US Agency for Toxic Substances and Disease Registry says that the antimony in fabric is very tightly bound and does not expose people to antimony, 4 as I mentioned earlier. So if you want to take the government’s word for it, antimony in PET is not a problem for human health - at least directly in terms of exposure from fabrics which contain antimony. (Toxics crusader William McDonough has been on antimony’s case for years, however, and takes a much less sanguine view of antimony. 5)
Antimony is just not a nice thing to be eating or drinking, and wearing it probably won’t hurt you, but the problem comes up during the production process - is it released into our environment? Recycling PET is a high temperature process, which creates wastewater tainted with antimony trioxide – and the dyeing process for recycled PET is also problematic. Another problem occurs when the PET (recycled or virgin) is finally incinerated at the landfill – because then the antimony is released as a gas (antimony trioxide). Antimony trioxide has been classified as a carcinogen in the state of California since 1990, by various agencies in the U.S. (such as OSHA, ACGIH and IARC) and in the European Union. And the sludge produced during PET production (40 million pounds in the U.S. alone) when incinerated creates 800,000 lbs of fly ash which contains antimony, arsenic and other metals used during production.6
Designers are in love with polyesters because they’re so durable – and cheap (don’t forget cheap!). So they’re used a lot for public spaces. Abrasion results are a function not only of the fiber but also the construction of the fabric, and cotton and hemp can be designed to be very durable, but they will never achieve the same abrasion results that some polyesters have achieved – like 1,000,000 rubs. In the residential market, I would think most people wouldn’t even want a fabric to last that long – I’ve noticed sofas which people leave on the streets with “free” signs on them, because it was out of style, or stained, or something – I mean, have you even replaced a piece of furniture because the fabric had actually worn out? Hemp linens have been known to last for generations.
1 “New Approach of Synthetic Fibers Industry”, Textile Exchange, http://www.teonline.com/articles/2009/01/new-approach-of-synthetic-fibe.html
2 Polyester, Absolute Astronomy.com: www.absoluteastronomy.com/topics/Polyester and Pacific Institute, Energy Implications of Bottled Water, Gleick and Cooley, Feb 2009, www.pacinst.org/reports/bottled_water/index.htm)
4 Shotyk, William, et al, “Contamination of Canadian and European Bottled waters with antimony from PET containers”, Journal of Environmental Monitoring, 2006. www.rsc.org/delivery/_ArticleLinking/DisplayHTMLArticleforfree.cfm