Not just no-iron clothing. Lots of clothing is treated with formaldehyde for various reasons.
Is it anything to worry about? No. Formaldehyde is pretty volatile stuff, and levels soon drop to pretty much zero once clothing has been washed and aired a few times.
That said, it’s probably advisable to wash and air brand-new clothes before wearing them if you have sensitive skin, or if the clothes are for a small child. (That “new clothes” smell is basically volatile organic compounds, of which formaldehyde is one.) I’ve noticed the skin on my neck getting a bit red and itchy when wearing brand-new shirts, but whether that’s due to any chemical intolerance or just because new shirts are stiffer and more scratchy, I couldn’t say.
So, unlike most chemical scare stories on the internet, it’s not complete hogwash, but neither are your shirts going to give you cancer.
Also, from what I can ascertain, non-iron shirts are not made by “dipping them in formaldehyde” as you will often read on the internet. The process uses formaldehyde resin - a polymer, with very different properties than formaldehyde itself (just as polyethylene has very different properties than ethylene). Yes, there will likely be a small amount of formaldehyde monomer present, but it’s not the same as “dipping the shirt in formaldehyde”.
Ok, so, what about formaldehyde resins? Are they dangerous? Searching a bit I found a lot about using those resins to make laminate materials and the like, but not much abut fabrics. Then I found this link here:
It reads a bit like a scare mongering page, but it has some cites at the end. I do not know whether the claims they make are true, but would like to know.
The resin itself isn’t the problem. What may be a problem is if the resin used contains residual free formaldehyde left over from the manufacturing process, or if it breaks down gradually and releases formaldehyde.
This quote is disingenuous:
The resin is the active coating. That won’t wash off, but the free formaldehyde will, at least to some extent.
This link does suggest that degradation of the resin has been a problem, but that modern versions of the coating have greatly reduced the amount of free formaldehyde produced.
Suppliers of these resins now seem to make a selling point of the low-formaldehyde formulations: example.
In a nutshell, I’d say the tiny amounts of formaldehyde are nothing to worry about unless you have a particular allergy, but it’s well worth washing brand new clothes treated with the resin before wearing them. You probably get more exposure from your carpet, or chipboard furniture. And don’t worry about “accumulated exposure” - formaldehyde doesn’t accumulate in the body.
Way, way back at the start of my career I worked for Monsanto on a replacement chemical for formaldehyde resins in the dry cleaning industry (the replacement was butanetetracarboxylic acid, IIRC). Anyway, formaldehyde exposure was the concern requiring the switch to BTCA – not exposure for people wearing the dry cleaned clothes; exposure for the dry cleaners.
Workers handling the treated clothing had a much higher exposure to the trace formaldehyde than could ever be possible from just wearing the treated clothes. So if you’re making the no-iron shirts, be sure to wear protective equipment to limit your exposure. Otherwise… eh.
We use formaldehyde to fix samples in the lab for microscopy. It’s a cross-linking reagent, meaning that it causes covalent bonds to form between adjacent organic molecules, like proteins. Once those bonds are formed, there’s absolutely no need to keep the formaldehyde around, so you wash it out. Which both answers the question posed by Colophon’s quote, and shows just how stupid the question was in the first place.