“We initiated the study last year to follow up on questions from a journalist about the safety of eye drops,” says Tuulia Hyötyläinen, lead researcher and professor of chemistry at Örebro University.

The Örebro researchers have studied a fluorinated compound, perfluorohexyloctane, which has properties and a structure that resembles PFAS. One difference is that it has previously been assumed to be biologically inactive. Meaning that it should not affect biological processes in the body.

“Our study shows that this assumption may not always hold true. Understanding how these compounds behave in the body is essential for protecting long-term human health,” says Tuulia Hyötyläinen.

Although eye drops are applied directly into the eye, small amounts of their ingredients can enter the bloodstream, particularly with repeated use. Previous research on similar substances has shown that they may accumulate in the liver over time.

The researchers have now therefore studied the effects in human liver cells in a laboratory setting. The experiments are designed to reflect low-level but long-term exposure, rather than short-term high-dose exposure.

“We wanted to capture changes in cell metabolism that could reflect repeated use,” says Andi Alijagic, a researcher leading the experiments and docent in biology at Örebro University.

The analyses showed global changes in liver cell metabolism. The study also shows that perfluorohexyloctane may be partially transformed inside liver cells into a PFAS-like substance. This suggests that the compound does not remain chemically unchanged in the body.

“These data suggest a pattern of changed metabolism that warrants further investigation in long-term studies and in living organisms,” says Matej Orešič, professor of systems medicine.

Beyond eye care products, the study – along with a growing body of evidence – adds to increasing concern that fluorinated chemicals used in medical and hygiene products may affect human health.

“Our findings cannot be directly translated into health outcomes in people. However, they do indicate that long-term exposure and effects in various organs deserve closer scientific and regulatory attention. This knowledge is needed for evidence-based decisions by regulators, healthcare professionals and manufacturers when evaluating chemical safety,” says Tuulia Hyötyläinen.

“It’s worth contemplating that similar substances are banned in ski wax but not in eye drops,” says Matej Orešič.