PFAS vs PFOA vs PFOS: what's the difference?

PFAS is the family

PFAS is the umbrella term for per- and polyfluoroalkyl substances — thousands of compounds sharing fluorinated carbon chains.

PFOA and PFOS are individual compounds

PFOA (perfluorooctanoic acid) is a long-chain carboxylic acid. PFOS (perfluorooctanesulfonic acid) is a sulfonic acid of similar chain length.

Both were used widely before restrictions, and both are among the most studied PFAS, which is why they are usually reported as individual parameters.

Why the distinction matters on a report

A claim about "PFAS" is only meaningful with the compound list attached. A filter evaluated against two compounds has not been evaluated against thirty.

For product testing, the compound list should be agreed before testing and printed on the report so results can be read exactly as they were measured.