The Real Scoop on Polyester
Any parent who is concerned about plastics next to their baby wants to know if synthetic materials are safe in cloth diapers. Let’s look at the science.
For centuries, naturally-occurring absorbent materials were used for diapering infants. These were probably picked from local fibers, easily available, and could have included materials as diverse as moss and linen.
Then, in the 20th century, the amazingly rapid development of artificial materials heralded an almost total switch in the West from cloth diapering to disposables. Highly engineered absorbent gels and processed wood pulp replaced reusable natural fibers. Although the vast majority accepted these changes as the inevitable (and even admirable) progress of technology, a small percentage continued to use cloth diapers.
Perhaps you are among those parents choosing to use cloth diapers because you reject the use of artificial materials. You may be concerned to see that such materials are showing up in popular cloth diapering products. Common man-made materials may be a health threat, including polyester fibers, vinyl and polyvinyl chloride (PVC), polyurethane laminate (PUL), and durable water repellent finishes (DWR).
Polyester was created in a laboratory in 1941, during World War II. It gained popularity as an apparel fiber, particularly in the 1950s, under trade names such as Dacron. It may have become a joke by the 1970s, but it remains, in its various forms, one of the most popular fibers used in clothing.
Polyester is the artificial fiber most commonly blended with cotton, where it is added to reduce cost, speed up drying times, decrease the tendency to wrinkle and improve wear-resistance. Unblended, it is used in a variety of fabrics, including the ubiquitous polyester fleece. In addition, there is a new type of polyester fiber that is made from 100% recycled soda bottles (PET on the bottle stands for polyethylene terephthalate, or polyester). The argument is made that this is a plastic fiber that apparently helps the environment.
You might think, therefore, that water-repellant, 100% recycled polyester fleece would be a good candidate for a diaper cover, and that a soft, poly-cotton blend might make a good diaper. That such a combination would function adequately is not really at issue. The point is that polyester is not the wonder fiber its manufacturers claim.
The use of certain polymeric silicones as cosmetic implants ended in a successful lawsuit against Dow-Corning; the vinyl industry is the subject of mounting litigation (and a critical documentary, the independently-made Blue Vinyl, which aired on HBO in June 2002); and now even supposedly inert polyester is running into trouble.
Researchers at Tufts Medical School noticed that cancer cells being grown in the lab multiplied more quickly in polyester test tubes than in glass. It appears that polyester slowly emits phytoestrogens, which are endocrine disruptors, or compounds similar to estrogen, which can promote certain types of cancer.
Enough people are worried about these chemicals that entire conferences are being held to discuss their possible effects. You can see the concerns of the scientific community reflected in this list of topics at a conference being held as we write.
Polymer Chemistry 101
It is probably a good idea at this point to back up a bit for some chemistry 101.
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.
You may not feel comfortable putting a potential endocrine disruptor next to your child’s most sensitive areas. What about some of the other fabrics and fabric treatments used in cloth diapering?
Vinyl and Polyvinyl Chloride
One widely-distributed brand of cloth diapers uses PVC or vinyl for its diaper covers.
PVC is a polymer made from vinyl chloride monomer and often contains harmful phthalates as unbound plasticizers. Before you buy a vinyl diaper cover (or anything else made from PVC, especially for your children) consider some of the information available from the U.S. Centers for Disease Control and National Institute for Occupational Safety and Health on vinyl chloride, the monomer for PVC or polyvinyl chloride. Pay particular attention to the “long-term exposure” sections.
- CDC, NIOSH Pocket Guide to Chemical Hazards: Vinyl chloride
- CDC, International Chemical Safety Cards (ICSC): Vinyl chloride
Vinyl baby and children’s toys are also very popular, but have raised significant health concerns. Search the U.S. Consumer Product Safety Commission website for references to vinyl and see also the article in Mothering magazine, Issue 90, Sep/Oct 1998, “Toxic Toy Story.”
The independent documentary film Blue Vinyl, which aired on HBO, primarily dealt with the effects of vinyl siding on residential users and the workers who manufacture and install the siding. The film was a catalyst to a PVC-free educational campaign, My House Is Your House. Remember, a diaper cover is in much closer proximity to more sensitive skin than vinyl siding and can contain the same off-gassing monomers.
Note: Materials used in baby toys and other children’s products have changed considerably between the time this was written in 2000 and 2008, with the adoption new safety laws of the U.S. CPSIA (Consumer Product Safety Improvement Act). Specifically, six phthalates were permanently banned from use in children’s toys and some baby care products. You’ll still find these plasticizers in many plastics all around you, though.
Polyurethane Laminate (PUL)
Polyurethane laminate, or PUL, has gained great popularity as a fabric treatment. It is applied to the surface of a porous fabric (usually polyester, but also cotton) to provide a flexible, totally waterproof layer. Ultrex and Extreme, two woven fabrics commonly used in outdoor clothing, are also polyurethane laminates. PUL makes functionally good diaper covers–it is an effective barrier to liquids.
But what are the precursor monomers for polyurethane? Most are based on TDI, or toluene 2,4-diisocyanate, a highly toxic carcinogen. Again the Center for Disease Control and National Institute for Occupational Safety and Health have information about TDI, the polyurethane monomer.
- NIOSH Pocket Guide to Chemical Hazards: Toluene-2,4-diisocyanate
- International Chemical Safety Cards (ICSC): 2,4-Toluene Diisocyanate
Durable Water Repellant Finish (DWR)
Durable Water Repellant finish is a generic term (rather than an trademark) in the outdoor gear industry for a water repellant surface layer, usually sprayed onto the fabric. This layer does not completely fill all the fabric pores (unlike PUL), so the fabric remains breathable. Goretex is probably the most well-known example of a DWR-treated fabric and its treatment contains a fluorocarbon similar to Teflon. The outdoor clothing manufacturer Patagonia describes their DWR finish as “polyurethane” and recommends re-treating “once per season, or more often if the piece gets a lot of use or washing.”
Patagonia recommends the use of Nikwax for re-treatment, which is based on a compound called ethylene vinyl acetate (EVA), blended with a mineral wax. It also contains small amounts of an acidified zirconium salt of a weak acid (acetic acid) and ethylene diamine tetra acetic acid (EDTA) to stabilize the emulsion. If you are interested in digging deeper, you could even read a patent for Nikwax or any proprietary formulation.
Patagonia suggests re-treatment if the garment is washed frequently. They cannot expect their hiking garments will be washed as often as diaper cover would be. DWR treatment would not be effective as a barrier unless you keep a bottle or can of Nikwax handy to restore your cover every few washes.
So, What’s the Harm in Plastics? What’s the Best Choice?
You might ask after reading all this, so what is the actual risk to our babies and families? What if we use some PUL or DWR or fleece for the outer parts of diapers and covers that don’t touch the skin? How much of the monomers are actually given off? Has anyone performed a study on this?
The problem is that we are not aware of any such specific study.
What we do know is this: The short-term risks of exposure to all of the chemicals mentioned is well documented.
The exposure tests are usually performed on animals, since most people would not willingly submit themselves to those kinds of tests and would certainly not volunteer their children. Then exposure limits are estimated, usually for adult males.
In some unfortunate cases, actual exposures from industrial accidents and the like have been used to refine these limits.
The effects of long-term exposure are more problematic to predict than short-term; often symptoms take years, or even generations, to show up.
Long-term studies of the effects of all the monomers mentioned in this article are still underway.
Remember also that these chemicals may respond very differently when used for diapering–the long-term studies are considering only the action of these chemicals in water or air. The presence of urea, ammonia, and the salinity of urine may alter the behavior of monomers in unpredictable ways.
Beyond Health Risks
The main focus here has been the possible health risks of using these materials.
Remember also, that continuing to use these materials supports the industries that produce them. That means continued consumption of the world’s oil, mineral and energy resources and continued pollution of our air and water. It also means continued exploitation of chemical workers around the world, especially in countries with low safety standards. The fate of these materials after we are done using them also needs to be considered. Are they biodegradable, reusable, recyclable?
Natural Materials Are Not Carginogens
In the meantime, wool, hemp, and cotton, particularly when grown and processed organically, are not carcinogens.
There are many reasons to consider the natural alternatives to artificial materials.
Wool is breathable, and micro-absorbent, and naturally moisture repellent (but can be treated with lanolin if necessary, but please don’t use DWR finishes for babies, despite manufacturer recommendations). Wool makes wonderful diaper covers.
Cotton and hemp are both highly absorbent and hemp especially can be grown easily without pesticides, herbicides and fertilizers. Cotton is not so easy to grow organically, but every year more acres are being converted from conventional production. It is becoming widely available as a diapering fabric. Ask for organic cotton specifically.
As you can see, there’s no good reason to use petroleum-based products like polyester, PUL or PVC in your child’s diapers when natural fibers work so well and pose no health risks. Choose natural materials, manufactured with minimal processing under fair labor environments.
- Life Without Plastic – Plastics, plastic types, plastic alternatives, and the effects of plastics on health and the environment.
- Berkeley Plastics Task Force, Ecology Center – Findings of a comprehensive report published 1996.
Please note: The bulk of this article is more than a decade old. There has been a lot of new research on this topic. The authors may update the article beyond the minor additions you may notice. In the meantime, keep the dates in mind and do your own research.
by Marc Pehkonen and Lori Taylor
copyright © 2000 – 2017 Marc Pehkonen. Used by permission.