A couple of further suggestions, that don’t involve buying new products (though a similar bag could be made from an old pillowcase):
Use a gentle wash cycle, to reduce the agitation that releases microplastics. I’ve seen conflicting advice on the effects of soaking and whether we should prefer a cycle that uses a lot of water or a little.
Save the synthetics for when they’re needed: If you’re outdoors all day in all weathers, carrying all your kit, choose stuff that’s lightweight, wicking, quick-drying, etc. If you’re just going to the gym, or for a short run in nice weather, a cotton T-shirt might not be so bad after all – probably not your best ones as they can end up less than fresh even after a good wash if you have to save up your washing to make a load. If you exercise frequently, this can reduce the amount you need to own, and prolong the life of synthetic garments.
Another thing you can do to reduce the amount of microplastic synthetic garments shed is to make then last longer. This might mean repairing them, such as replacing a failed zip as I did on a bike jersey yesterday. For a few minutes and a few grams of (synthetic) materials, I significantly prolonged the life of the garment.
