I'm sure there's got to be a safe alternative. I haven't bothered to look, I just use the fabric curtains and keep inside the tub--like in hotel tubs? kwim?-- and wash very frequently and I have never had any problems with mold. I remember a post on The Soft Landing talking about EVA being a safe alternative to PVC so check thesoftlanding.com they usually have a database of household goods.
Re: shower curtain that is ecofriendly?
My Blog: Naturally Mindful
Check out the listing of PVC free shower curtains on VitaFutura - we also avoid all PVC in our bath mats, shower curtains, etc!
https://www.healthyhappytot.com/pvc-free-bath/