The idea is amazing
but I agree with Caterpillar Peacock about using unbleached and undyed cotton. I have another concern, a month ago I saw on TV an interview with a designer that use only organic cotton in her clothes, she explained that "normal" cotton grown full with pesticides so maybe this can be a little harmful. I live in Mexico and I don't know if is easy and cheap to get chemical and pesticide free cotton.
If you do any research, you would end up naked eating twigs in the forest! I am serious!!! Check out what tampons consist of, then take a look at how we get those 'ingredients'. I have said it before but the simple process of bleaching (with chlorine) is terrible for the environment and you!
There is a great debate about how much dioxin is present as a result of the processing of rayons (which are in tampons) and other wood products, some are of the thinking that eliminating as much contact with dioxins, no matter how minute, can greatly reduce all kinds of health risks, not just cancer. Get yourself some organic fiber, whatever it is and make your own, use them once, twice or three times my lady, but get away from those plastic manufactured chemical filled hygeine products! You can make them yourself and be confident you are doing yourself and the environment a great service!
If you can't find organic yarns, try finding organic fabrics. If you can't sew, cut the fabric into strips and crochet away!!!
Please, just remember to change them frequently! And use clean hands!!!