I think, as I mentioned in my opening remarks, that class of per- and polyfluoroalkyl substances, or PFAS, is upwards of a 5,000, maybe 10,000, group of chemicals internationally. In the context of contaminated sites, they're predominantly from legacy use of aqueous film-forming foams that are present either for the use of containing fires or for training purposes.
The Government of Canada has been looking at this class of chemicals for over 15 years. There are very well-characterized chemicals, including PFOS, long-chain perfluorooctane sulfonate, and also a range of other very complex but well-studied chemicals.
Health Canada has recently adopted a drinking water quality objective, which cites the most common PFAS that are being monitored at these contaminated sites, and then provides guidance on analytical methods to ensure that sampling is done to detect these chemicals and what treatment can be done, at both the domestic residential scale—