[Opinion] What Limits Will the World Health Organization Recommend for PFOA and PFOS in Drinking Water?
By Elizabeth Southerland, and Linda S. Birnbaum
Environ. Sci. Technol.
April 26, 2023
DOI: 10.1021/acs.est.3c02260
The World Health Organization (WHO) updates Guidelines for Drinking-Water Quality (GDWQ) on a periodic basis and is in the process of adding perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) to the fourth edition of these guidelines. (1) On September 29, 2022, the GDWQ chemical working group released a draft “PFOS and PFOA in Drinking Water” background document for public comment recommending limits for these chemicals. (2) WHO received 25 sets of comments but has not yet disclosed the comments or announced when the guidelines will be finalized.
It is critically important for the safety of drinking water worldwide that WHO recommendations are based on the best available science on the health effects of PFAS and the effectiveness of drinking water treatment technology. Here we explain why the draft WHO guidance values are not based on the best available science and should be extensively revised before they are finalized.
WHO proposed provisional guidance values (pGVs) of 100 ppt individually for PFOA and PFOS and a combined pGV of 500 ppt for total PFAS, with total PFAS based on the 29 PFAS compounds reliably measured with the U.S. Environmental Protection Agency’s (EPA) analytical methods for drinking water. Once finalized, these guidelines will represent the position of the United Nations regarding PFAS in drinking water and are likely to be adopted by many countries around the world. Several countries have promulgated or proposed drinking water limits for PFAS over the years, with the most recent ones trending to much lower levels. (3) The WHO draft guidelines are much higher than recent limits set by Denmark (2 ppt for four PFAS) or proposed by Canada (30 ppt for total PFAS). (3,4) These guidelines could also have a significant impact on legal challenges to enacting drinking water standards for PFAS in the United States. On March 14, 2023, EPA posted a prepublication rule proposing drinking water standards of 4 ppt individually for PFOA and PFOS, along with health-based goals of 0 ppt for these two PFAS, and a hazard index for the combined concentrations of PFHxS, HFPO-DA, PFNA, and PFBS. (5) EPA expects to promulgate these standards within a year with a compliance date by 2026.
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