PFOS and PFOA in Drinking-water: Background document for development of WHO Guidelines for Drinking-water Quality

Per- and polyfluoroalkyl substances (PFAS) is the collective name for a large group of fluorinated compounds, which are used in a wide range of applications, such as aerosol propellants; solvents; pesticides; antifoaming agents; surface treatments for textiles, leather, masonry and paper and board; leveling agents in paints, coatings and waxes; plastics; lubricants and greases; and fire-fighting foams.

The most widely studied of these PFAS are perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).  Although the stability of PFOS and PFOA as well as their surfactant properties make them useful in consumer and industrial applications, there are concerns with their persistence and impacts on the environment and human health, as a result of exposure through the widespread uses of these chemicals. Drinking-water is one of several environmental sources of human exposure to PFAS, along with exposure via food, use in consumer products and occupational exposures.

What is the status of the process in developing the background document?

WHO’s GDWQ chemical working group guided the preparation of the draft background document for the GDWQ on PFAS in drinking-water with a focus on PFOS and PFOA.

The process was initiated in 2017. Preliminary drafts were discussed at numerous consultations with the authors and the chemical working group, including in July 2018, April 2019, March 2021 and October 2021. The document also went through a peer review process in 2021, with the feedback provided considered by the chemical working group. 

“PFOS and PFOA in drinking-water: Background document for development of WHO Guidelines for drinking-water quality” was offered for public review from 29 September to 11 November 2022.  During this period, WHO received 25 sets of comments from different stakeholders. WHO responses to the most common comments can be found here.  In light of comments received and to ensure that the latest evidence is taken into account since the background document was drafted, WHO will continue its review of PFAS. For further information on this initiative see here.

What is WHO advising its Member States in relation to PFOS and PFOA in drinking-water?

Although the process of developing the guideline values is still ongoing, WHO’s advice to its Member States in relation to PFOS and PFOA in drinking-water is guided by key principles laid down in the draft background document for the GDWQ on PFAS in drinking-water, namely:

1. Member States should strive to achieve concentrations in drinking-water that are as low as reasonably practical.
2. Contamination of water sources should be minimized, including preventing new sources of contamination.
3. Non-essential uses of PFAS should be stopped.
4. Risks from PFAS need to be balanced with other risks in the water supply including not having adequate supplies of drinking-water.