Clothes are made from a wide range of different materials and while it is widely believed most fabrics are made from natural fibres like cotton, linen and leather - sourced from plants and animals; the greatest percentage of fabrics are made of materials and chemicals derived from fossil fuel-based crude oil - plastics. And they are mostly polyester.
According to Common Objective, in descending order, our clothes are made from synthetics (mainly polyester) 62%; Cotton 24%; Cellulosics 6%; Wool 1%; Other 7%. Polyester has really come into it's own in recent years and it is fast fashion that drove it into our closets.
Polyester, also known as polyethylene terephthalate, is a synthetic fibre, manmade from petrochemicals (fossil fuels). Synthetic fibres are processed through a series of highly toxic chemical processes. The main chemicals used in the production of polyester are terephthalic acid (TA) or dimethyl terephthalate, which are reacted with ethylene glycol. Polyester fibre manufacture also involves a process of purifying TA and is based on bromide-controlled oxidation.
Polyester is a shiny, smooth, and flowy fabric that is now synonymous with trendy, cheap clothing - fast fashion. Polyester is also blended with cottons and linens to create a more natural looking fabric that still has flow - and is cheap. Apart from clothing, polyester and polyester blends are in many bedding products.
Textile factories, where around 300 million people around the world work (many are in China, Indonesia, and Bangladesh), are dangerous environments - and beyond the factory, the surrounding lands and waterways are also at risk. Textile factories are infamous for having terribly low safety standards. Millions of workers (many of whom are children) are regularly subject to chemical exposure (heavy metal cobalt; manganese salts; sodium bromide; antimony oxide, and titanium dioxide), machine injuries, building instability, and fires.
Sadly the problems with polyester don't stop at the factory door and this is a summary of its impact life journey.
The most obvious thing to do is to avoid synthetic fibres altogether. If you do need to buy them - swimmers and gym gear are obvious examples - buy garments made with regenerated nylons like Econyl. If you choose to buy synthetic garments or buy rescued or secondhand synthetics, minimise the number of times you wash them and always use a wash bag. Essentially, be aware that you are contributing to our plastic waste problem and minimise your impact.
Fashion and fabrics are very very tricky. Things that seem fine aren't and even some things that don't seem fine are. Bamboo rayons for instance are made the same way as a synthetic. Bamboo is simply part of the base material. After that, it's chemical stew.
Regenerated nylons like Econyl are made from melting down nylon fishing nets and other discarded nylons, mixing with other commerical waste and regenerating new recyclable nylon. (Bear in mind that they still do shed micro fibres.)