I'm going to weight in because my partner is an environmental engineer who performs remediation of PFAS contaminated sites for the EPA and other Federal entities.
> Even though they 'stopped' using these chemicals in manufacturing 10-15 years ago, there's still an incredible level of contamination
They haven't stopped using them, the chemicals are still used in stain and water resistant carpeting and textiles. They're used in cosmetics and sunscreens among other things. One of the biggest sources of contamination is fire retardant foams used in fire suppression.
If you look at some of the sites in that report listed as having contaminated water, many are located near military bases, like Oceanside CA. These bases are the largest sources of ground water contamination of all sorts but specifically PFAS because they routinely practice fire suppression exercises.
> 26,000 sites listed by EPA [1]. But that's sort of irrelevant, because these compounds don't break up over human time scales.
PFAS is an emerging contaminant and isn't strictly regulated yet. Keeping track of these sites however is not irrelevant, it's extremely important that we know of and track these sites because they can and are being remediated.
The current method of remediation involves setting up hundreds or thousands of ground water monitoring wells around a contamination site to track the plumes and then using pumps to remove the ground water and filter it through activated carbon filters. The filters are treated as hazardous waste and incinerated.
> It's hard not to be alarmist about this, PFAS contamination is genuinely terrifying.
I wouldn't say you're being alarmist at all, if anything the current response to PFAS is insufficient and we should be treating it as a public health crisis at least on par with Lead.