A US appeals court has rejected a ruling that would have allowed millions of Ohio residents to sue 3M, DuPont, and others as a group over contamination by so-called toxic "forever chemicals."

A lower court had approved a massive class action, in which virtually every Ohio citizen could have sued the chemical companies due to PFAS (per- and polyfluoroalkyl substances) found in the bloodstream of the lead plaintive Kevin Hardwick.

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3M's plant in Belgium, which made PFAS – Google

The 6th US Circuit Court of Appeals in Cincinnati, Ohio, reversed that decision, stating very strongly that the complaint was too broad.

PFAS chemicals are widely used in many industrial applications relevant to data centers, including silicon chip manufacturing and two-phase immersion cooling. In response to findings that they can cause harm, 3M has withdrawn its Novec coolant along with other PFAS substances.

Two-phase cooling companies have moved to broaden their product lines. For instance, LiquidStack has launched a non-PFAS single-phase cooling system and ZutaCore says it will eliminate PFAS in 2026, through the use of alternative fluids.

The November 27 ruling, by District Judge Edmund A Sargus Jr, pulls no punches:

"Seldom is so ambitious a case filed on so slight a basis," said the Judge. The gravamen of Kevin Hardwick’s complaint is that his bloodstream contains trace quantities of five chemicals—which are themselves part of a family of thousands of chemicals whose usage is nearly ubiquitous in modern life.

"Hardwick does not know what companies manufactured the particular chemicals in his bloodstream; nor does he know, or indeed have much idea, whether those chemicals might someday make him sick; nor, as a result of those chemicals, does he have any sickness or symptoms now. Yet, of the thousands of companies that have manufactured chemicals of this general type over the past half-century, Hardwick has chosen to sue the ten defendants present here."

Sargus says that Hardwick's complaint rarely alleges an action by any one company, and also seeks to represent not just everyone in Ohio, but all residents of the United States. The district court had allowed this to proceed on behalf of Ohio residents.

PFAS chemicals have "innumerable" uses, including "medical devices, automotive interiors, waterproof clothing and outdoor gear, food packaging, firefighting foam, non-stick cookware, ski and car waxes, batteries, semiconductors, aviation and aerospace construction, paints and varnishes, and building materials," says the Judge.

Hardwick is a firefighter who used PFAS-based firefighting foams for 40 years. A blood test has found PFAS chemicals in his blood, but did not prove they came from the foams, nor did Hardwick know who made those chemicals, or who made the foams he used.

The result of this case may not affect the ongoing case against PFAS. The US Environmental Protection Agency (EPA) has classified some PFAS substances as hazardous substances, adding to the difficulties involved in using them, because surplus or used PFAS must be treated as hazardous waste.

EPA findings from March 2022 suggest that PFAS may affect human reproduction and development, harming the immune system and increasing the risks of some cancers. The European Chemicals Agency (ECHA) has published similar findings.

The EU has reversed earlier plans to ban PFAS, after industry groups argued that the chemicals are needed for technologies that will help reach net zero.