They are talking about PFAS, which was (is?) in aqueous foam firefighting chemicals that were (are?) in widespread use.
At air force bases, airports (both the trucks and hangar suppression systems), firefighter training facilities. Municipal fire departments have metering devices on their trucks and can mix in the foam additive if it's warranted. Foam is incredibly effective on a lot of fires.
It gets into the groundwater from stuff like accidental hangar fire suppression system triggering, training exercises (at an airport near me, they have a dedicated steel structure that vaguely resembles a jetliner which they use for training, and yes, they use foam every time.) There are a lot of videos on youtube of the systems going off, intentionally (certification after installation - the system has to fill the hangar to X feet of foam within Y time), or accidentally being triggered because someone didn't respond to the prealarm fast enough to get to the control panel and stop it before the system started discharging.
At AF bases, FF training facilities, and airports it gets into the groundwater and it's game over - everyone who gets water from that water table has to install an expensive filtration system. And that's assuming it doesn't get into a nearby river or stream. The stuff gets used on a lot of vehicle fires on highways, those are often near riviers, streams, lakes, reservoirs....
I hadn't heard that PFAS or related chemicals were in the colored flame retardant used in forest fire fighting, though.
AFFF is being/has been phased out pretty much everywhere in the first world. There is still plenty of it around though - disposing of, and then filling with fluorine free foam can be an expensive process.
Personally, it’s about $10/litre to dispose of. Regardless of concentration. So properly rinsing out old equipment is expensive. But I know the situation differs by country, and what’s deemed “acceptable” varies too.
Powder doesn’t contain fluorinated compounds, at least to my knowledge. The role of fluorosurfactants is in increased wetting and emulsifying with hydrocarbons. Not really applicable to a dry agent.
It's a doomscroller-brained comment, confusing the PFAS fire retardant foams used on military bases with this ammonium phosphate made from mined Phosphorite rock.
AFFF is used in far more than just military bases. Outside of the USA, AFFF extinguishers, small vehicle/building hazard suppression systems, etc. are much more common.
I haven't found any studies about that, can you link them? It doesn't look like ammonium phosphate is dangerous.