On September 29, the World Health Organization released its draft PFOS and PFOA in Drinking-Water background document. In it, WHO outlines its proposed guidance for PFOS and PFOA in drinking water. WHO found that "the uncertainties in identifying the key endpoint applicable to human health following exposure to PFOS and/or PFOA are too significant to derive a HBGV [health- based guidance value] with confidence."

As a result, WHO proposed provisional guideline values for both PFOA and PFOS individually of 0.1 µg/L, or 100 parts per trillion (ppt). For all PFAS that are currently measurable, it proposed 0.5 µg/L, or 500 ppt. These numbers are orders of magnitude higher than those released by EPA earlier this year, which set interim health advisories for PFOA at 0.004 ppt and PFOS at 0.02 ppt.