WHO draft drinking water guidance ‘disregards’ science on ‘forever chemicals’, say experts

The World Health Organization's (WHO) approach to "forever chemicals” for its drinking water quality guidelines draft has been criticised by an international group of scientists, who are calling for a revision or withdrawal.

In an open letter, a group of 116 global experts on per- and polyfluoroalkyl substances (PFAS), a group of chemicals described as “forever chemicals” as they do not break down in the environment, have called on WHO to review or withdraw its draft assessment looking at two PFAS compounds, PFOS and PFOA, in drinking water.

The WHO document suggests “a pragmatic solution” for the derivation of provisional guideline values (pGVs) for PFAS, citing the lack of consensus over what level of PFOS and PFOA substances are harmful to human health in drinking water. It suggests a 0.1 micrograms per litre (µg/L) for both PFOS and PFOA, and 0.5µg/L limit for all PFAS. Using the US Environmental Protection Agency (EPA) conversion guide, this is 100 parts per trillion (ppt).

The WHO figure is the same level recommended in the UK by the Drinking Water Inspectorate, which suggests that at PFOA or PFOS levels greater than 0.01µg/L, health professionals should be consulted, and levels should be kept below 0.1µg/L. The European Commission is seeking to impose a 0.0044µg/L limit on 24 PFAS in ground or surface water, expressed as a PFOA equivalent. This is equivalent to 4.4 ppt.

The level of these compounds that the EPA considers safe in drinking water is 0.004 ppt and 0.02 ppt, for PFOA and PFOS respectively.

The WHO report states that the values “were not derived based on adverse health effects studies, the values fall within the range of most health-based values derived through national risk assessments”.

However, the scientists said: “We strongly recommend that this document be significantly revised and the numerous peer-reviewed scientific studies demonstrating strong links between PFOS and PFOA exposure and the many adverse health outcomes be carefully considered. Otherwise, the proposed guidance should be withdrawn.

“The WHO assessment disregards the robust evidence of human health harm at environmentally relevant exposure levels which is also supported by experimental literature.”

The scientists pointed to studies that show the carcinogenic impact of PFOA, which would “result in a drinking water value well below the WHO provisional guideline, making this an important and sensitive endpoint for risk”.

The group also highlighted that PFOS and PFOA exposure has been linked to liver damage, which they say is disregarded in the WHO report. They further criticised the report for “misstatements” regarding the immunotoxicity of PFAS.

“As the authoritative international body on public health and water quality, WHO should provide health-protective, science-based guidance,” said the scientists.

They argued that PFOA and PFOS can be removed from drinking water to non-detectable levels, and said that although they recognise the high cost of this removal process this is “not a valid justification for setting less protective drinking water guidelines”.

This problem of PFAS has seen increasing scrutiny globally. The US has released a National PFAS Testing Strategy under the Biden administration, to address the data gap on the toxicity and presence of PFAS, campaigners are lobbying to ban PFAS in Europe, and the UK chemicals stakeholder forum has proposed a working group to support the development of policy on PFAS in the UK.

As a final note, the group has requested the WHO enforce conflict-of-interest policies and identify the names and affiliations of those involved in preparing or peer reviewing this draft, and any future WHO documents.

According to the WHO webpage: “WHO has strict ethical principles of integrity, independence and impartiality”.

It states WHO staff members must disclose any conflicts of interest on an annual basis, and experts contributing to WHO must disclose “any circumstances” that may result in a conflict of interest and be “actually and ostensibly, objective and independent.”

A WHO spokesperson said: "WHO produces international norms on water quality and human health in the form of guidelines that are used as the basis for regulation and standard setting world-wide. The Guidelines for drinking-water quality (GDWQ) are updated through a "rolling revision" process which ensures that the GDWQ presents the latest scientific evidence and addresses key concerns raised by countries.  This has been achieved by systematically updating sections of the GDWQ as new or updated evidence becomes available.

"Per- and polyfluoroalkyl substances (PFAS), with a focus on perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), are currently being considered for the update of the GDWQ.  The draft background document was offered for public review from 29 September to 11 November 2022.  During this period, WHO received 25 comments, which will be carefully reviewed."