The World Health Organization (WHO) published its fourth edition of the Guidelines for Drinking-water Quality in 2022, including for the first time guideline values specifically for PFAS compounds. These guidelines serve as the primary reference point for drinking water quality management in dozens of countries that lack domestic regulatory capacity to develop independent PFAS risk assessments—making the WHO framework the de facto global standard in much of the developing world. Understanding the WHO approach, its derivation, and how it compares to national standards that have moved beyond it is essential for any manufacturer or technology provider operating across international markets.
WHO 2022 Guideline Values for PFAS
The 2022 WHO guidelines established the following health-based guideline values for PFAS in drinking water: PFOS at 100 ng/L; PFOA at 100 ng/L; PFHxS at 600 ng/L; and PFNA at 90 ng/L. These values are derived from tolerable daily intake (TDI) values established by WHO’s International Programme on Chemical Safety (IPCS), combined with standard assumptions about drinking water consumption, body weight, and the proportion of total PFAS intake attributable to drinking water exposure. WHO emphasized that these guidelines are health-based values—not technology or feasibility-based limits—meaning they represent the concentration at which lifetime consumption is unlikely to cause a measurable increase in risk of adverse health effects in the most sensitive population groups.
How WHO Values Compare to National Standards
The WHO guidelines were already more protective than many existing national standards at the time of publication in 2022. However, subsequent national regulatory actions have in several cases gone significantly further, reflecting different regulatory philosophies about how to handle scientific uncertainty and mixture effects. The U.S. EPA’s 4 ng/L MCLs for PFOA and PFOS—finalized in April 2024—are 25 times more stringent than the WHO guidelines for both compounds. The EU Drinking Water Directive’s 100 ng/L sum-of-20-PFAS value is numerically equal to WHO’s individual PFOS and PFOA guidelines but applies to the combined concentration of 20 compounds, making it effectively more stringent at any site with multiple PFAS present. Australia’s June 2025 revised PFOS guideline of 8 ng/L is 12.5 times more stringent than WHO’s 100 ng/L value for PFOS.
The WHO Mixture Challenge
One of the most significant limitations of the 2022 WHO guidelines is their compound-by-compound approach, which does not account for the cumulative health risk of exposure to multiple PFAS simultaneously. Real-world drinking water contamination almost always involves mixtures of PFAS, but the WHO guidelines provide individual values for only four compounds and do not establish a sum-of-PFAS approach equivalent to the EU’s parametric value. WHO acknowledged this limitation in the 2022 publication and committed to developing guidance on mixture assessment in a future update. Several countries that reference WHO guidelines as their primary standard have adopted supplementary national guidance on PFAS mixtures pending the WHO update.
WHO as the Floor for Developing World Regulation
In the absence of domestic regulatory capacity, many lower- and middle-income countries use WHO guidelines as the legal standard in their national drinking water regulations. Countries across Sub-Saharan Africa, South and Southeast Asia, and Latin America that have incorporated WHO 2022 PFAS guidelines into their national standards now have a legal basis for requiring PFAS monitoring and remediation where concentrations exceed 100 ng/L for PFOS or PFOA—a modest but real improvement over the absence of any standard. As monitoring programs identify sites above WHO guideline values in these markets, treatment technology procurement will follow. OEM filter manufacturers that can demonstrate performance to WHO guideline values—and that have the cost structure to serve lower-income markets—are positioned for long-term growth in the expanding global PFAS treatment market.
Expected WHO Update
WHO has indicated that its PFAS drinking water guidelines will be revisited in a future edition update that will address: the rapidly evolving science on PFAS health effects at lower concentrations; the development of a mixture assessment approach; the inclusion of additional PFAS compounds beyond the four currently covered; and alignment with the analytical capabilities of monitoring laboratories in lower-resource settings. The timing of the next WHO PFAS guideline update has not been specified, but the pace of national regulatory action globally—and the scientific publications accumulating since 2022—suggest that an update is likely within the next three to five years. Countries that reference WHO guidelines will see their effective PFAS standards tighten substantially when the update is published.