I have worked in the Single-Use Plastics and Chemical industries for two decades now in sectors such as BioPharma, BioTech, Chemical Manufacturing, Refining, and Food & Bev, and currently work for a company that manufactures single-use plastics. Virtually every drug, vaccine, sauce, shampoo, water bottle, snack, etc. that goes into or is consumed by anyone, is produced using heavy PFAS materials in the fluid-systems or paths during manufacturing, or are packaged in PFAS materials.
Why? Because PFAS are incredibly durable, and phobic to essentially any type of liquid, be it water, oil, ketchup, glue, you name it. It is also infinitely faster and more profitable to use PFAS for production and packaging.
PFAS are progressively more well-studied, but still in the early stages of "science" and "medicine" understanding their impact. The data on just the handful of the PFAS family of chemicals that have been studied, is alarming. The vast majority of PFAS chemicals have not been studied at all yet, as there are thousands of chemicals within the family. Based on what we do know, they should ban them all*, everywhere, in everything, as quickly as possible.
* (This is not physically possible in our lifetime or probably ever due to their absolute prevalence in virtually every meaningful industrial process or manufacturing sector, and the immense lobbying power of industries that rely on these chemicals to hit profit numbers, kickback to politicians, etc. etc. etc.)
One semi-frequently cited study in our circles for reference:
https://pmc.ncbi.nlm.nih.gov/articles/PMC7906952/
Environmentally, the concern is as already described prior -- leachability into the water supply, and the long-term accumulation of PFAS in said water supply, rising to the surface, etc. PFAS have been shown to impact animals outside of humans. I have not heard of any data or seen any studies (outside of locations adjacent, downwind, or down-stream of chemical plants) that indicated any meaningful build up in natural landscapes yet. But it is inevitable if the manufacture and usage of PFAS continues.
Practically speaking, the risk of PFAS shedding and absorption from clothing through the skin is minimal compared to how much exposure we have from nearly anything we eat and drink these days. Talk to any compliance officer or chemist involved in the design and manufacture of outdoor gear, and they will tell you your risk of PFAS exposure from clothing is largely limited to the presence of moisture (sweat) combined with friction, directly on the skin. This goes for most synthetic materials that are against your skin in those conditions. This is why you see a big push in media and marketing back to natural fiber underwear, and away from synthetic underwear. Because PFAS have shown clear impacts on reproductive organs in both men and women. DWR is pure PFAS, but is external to your body, so almost exclusively an environmental concern as it degrades on your rain gear. When you wash your rain gear in the washer, then you are introducing those PFAS to your ground water and water supply as well.
Largely, precaution is the key here and what states are going for. Early studies are showing clear and concerning negative health impacts of PFAS to humans and animals, and the half-life's range all the way up to 40 years in the human body for some of these chemicals. In the ambient environment, PFAS once again have varying half-life's, with some reaching up to 1,000+ years. The continued accumulation of them, combined with early warning signs of their impact, are why folks are raising the flag and banning them early. Again, this is all preliminary findings with very strong correlations.
PFAS are in virtually everything these days, there is no escaping them in your day-to-day life anymore.
This is really a case of "hey, this is for sure bad for us, maybe we should do what we can to mitigate it now instead of later", or not making it our children's problem and destroying future generations biology and food/water supplies.
In the end, if you are a younger adult with health and longevity in mind, you may want to invest the time into researching the already known effects on the human body from PFAS. The best you can personally do, is to eliminate sources of PFAS in your personal life ranging from your clothing, food and water storage, cooking utensils/pans, cleaning chemicals, etc.
Ultimately, though, unless you live in an extreme remote and untouched location, with your own stable food and pure water supply, you aren't escaping PFAS no matter what you do.