"Natural cardboard will quickly loose it's strength if exposed to hot oily food,..."

I know, I've experienced the problem of disintegrating containers myself many times. That said, I believe that for many applications there are either existing solutions that are practical and still offer PFAS-type performance that won't disadvantage people too much or that new chemistry can be developed that's much more environmentally friendly. As I mentioned above in my previous reply traditional greaseproof paper doesn't contain PFAS so why not use it? It's suitable for food preparation and delivery. However it's not suitable for everything and other alternatives to PFAS have to be found.

It seems to me that chemistry might hiding even better solutions. I'm not a professional chemist but I've studied the subject more years than I care to remember, so I'm not going to offer a neat solution to the problem here, (anyway, if I had one I'd have patented it and I'd be rich). :-)

When previously confronted with these types of problems chemists have applied themselves and have often found suitable solutions. After all, that's a major aspect of chemical engineering. Moreover, I'd be very surprised if there aren't existing solutions that are more environmentally friendly already available. It's finding them and making the switch that's difficult. That said, new chemicals will have to be engineered for specific applications.

Whether PFAS-type chemicals can be modified to break down more easily is moot, as the carbon-fluorine bond is extremely strong and not much can touch it for strength, but there are other molecules that are potentially suitable—that is, ones that can be easily converted into materials that are initially impermeable to water, oils and grease but breakdown after suitably long exposure to water, bacteria etc.

At first guess I'd be looking at reexamining cellulose as the basis for developing better materials but no doubt there are many others that would be suitable. It's a natural material that's readily available from wood and plant matter and it's environmentally friendly, and we understand its chemistry. We already make cellophane from it which is impervious to water and oils but it will still break down upon extended exposure (one of the reasons for why cellophane isn't used more often is that it lacks long-term durability; that wasn't seen as a vitrue but it's now a property that we actually want).

Previously, cellulose and cellulose-type plastics such as cellophane and celluloid were bypassed in favor of oil-based plastics specifically because they weren't as durable as the latter, but in the light of the PFAS-forever chemicals problem I'd reckon a reexamination of their chemistry would seem in order. We need to start researching them and other suitable ones again.

A quick and rather oversimplified way of looking at what's needed to replace PFAS is to think about how soap and detergents work. We start with an oil which is hard to break down partly because it's hydrophobic and hates mixing with water which would help towards breaking it down. To tame its hydrophobic tendencies we attach water-loving hydrophilic OH (hydroxyl) groups to its molecules which they accept only under considerable duress.

Luckily, it turns out that this brual attack hasn't destroyed the oil molecules completely, rather they've metamorphosed—saponified—into a sort of schizophrenic 'hybrid' compound that exhibits both hydrophobic and hydrophilic properties. Now one part of this new 'hybrid' retains its affinity for oils whilst its 'attachment' happily joins with water. Thus, the oily end will still grab grease on your plate whilst its new hydroxyl part allows water to wash the whole mess away. Applying such a process to forever chemicals such as PFAS is extremely difficult if not impossible because of the extremely tough organo-fluorine bond.

What we need to do is to develop a suitable range of compounds that have properties somewhere between the extremely strong bonds exhibited by PFAS and those that can couple easily with water and or other common compounds that are suitable, this will allow them to be broken down into harmless environmentally friendly byproducts.

Nevertheless, we still want control over the breakdown process, that is we need to design chemicals that initially resist being broken down so they are actually useful and do what we want but eventually succumb to being broken down after a suitable duration when we're finished using them.

I believe that this not beyond the capability of modern chemical engineering. As I see it, the main problem is that there's a huge well established industry out there with lots of existing infrastructure that's standing in the way. It's been used to manufacturing and using forever chemicals for a very long time, thus it has inertia and will inherently resist change; moreover, making the change to more friendly alternatives will likely come at considerable cost.

And that's the crux of the matter.