Girlfriend Collective (and I’m sure other places) actually sells a microfiber filter that you can hook up to a washing machine to filter out synthetic fibers (you take the filter out if washing organic fibers – however many jeans have Lycra or other synthetic materials to make them stretchy). There are also bags that you can wash synthetic fiber clothing to prevent synthetic fibers from getting in the water supply. Filter link
Edit – another option would be to make sure you are buying 100% cotton. Some companies are also dedicated to sustainable practices and limiting waste. A good example is The Reformation which provides access to quarterly reports showing their practices and info on how they limit waste The Reformation The real answer is just to remove your pants before you eat to ensure they stay clean.
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