Every fabric has some form of processing that includes potentially toxic chemicals.
Google "toxic fabrics" and a host of sites will come up, some from as far back as 1993. Generally they list a number of synthetic fabrics (acrylic, nylon, polyester) along with rayon (which is made from chemically processed wood pulp) and make the case that all are bad because they are made from scary chemicals. Obviously, natural fibers such as cotton, hemp, wool, and linen are the way to go. Those are made from plants and sheep, not coal and petroleum derivatives.
The truth is more complicated than this. Your clothing is never made solely out of just cotton or polyester. Every single fabric has some form of processing. It may be preshunk cotton, or superwash merino. It may be bleached. It's almost always dyed. And nowadays clothing comes in all kinds of high-tech variations: UV protective, bug repellant, wrinkle-free, stain resistant, antimicrobial, and so on. Even pure cotton can be grown with pesticides.
These chemicals pose a myriad of concerns for the environment, both in the place of manufacture and due to chemicals released through washing. But what about the safety to the wearer?
The Basics: What Are Fabrics Made From?
If you look in your closet, you'll likely find a number of different natural and synthetic fibers. Over 60 percent of global fiber consumption is comprised of petroleum based synthetic fibers, although some may be used for textiles other than clothing (like rugs or rope). Comparatively, cotton makes up nearly a quarter of textile consumption, with wool making up about 1 percent, and other natural fibers (hemp, linen, etc) accounting for 5 percent. The remaining 6.6 percent are wood-based cellulose fibers (e.g. rayon).
Natural fibers come from either plants or animals. Plants used for clothing include cotton, hemp and flax. Animal fibers are more diverse, even if some, such as yak, remain uncommon. However, sheep are not the only animals who can provide high-quality fiber: alpacas, goats (cashmere and mohair), rabbits (angora), yaks, camels, llamas, and even the wild alpaca relative, the vicuña, provide fiber used for clothing. Silk is also a natural fiber, made from the cocoons of the mulberry silkworm. Other animal products used in clothing are hides (leather), feathers (down) and fur.
While humans have used natural fibers for millennia, rayon, which is made from wood fibers with synthetic processing, was invented in 1894, and the first fully synthetic fiber, nylon, was invented in the 1930s. Other wood-based fibers produced with synthetic processing include modal and bamboo. Fully synthetic fibers, generally made from petroleum or coal products, are acrylic, polyester and spandex.
Toxicology research into clothing focuses less on the fibers themselves and more on the chemicals used in processing the fibers. Even a simple cotton T-shirt requires numerous chemicals to bring it to market. The question for consumers is not only how safe are the chemicals used, but what are you willing to sacrifice and how much are you willing to spend in order to get the chemicals out of your closet?