Common chemicals nicknamed 'forever chemicals' for their tendency to stick around in the environment for a disconcertingly long time have been detected in Arctic seawater.

PFAS (per and polyfluoroalkyl substances) chemicals are used in a lot of household products. While the effects of PFAS on human health are still being debated, they have been detected in the past in our food and drinking water, as well as many waterways.

Looking at the waters of the Arctic, researchers were able to detect 29 different PFAS coming in and going out of the Arctic Ocean, and, worryingly, one compound – the supposedly less persistent HFPO-DA – has been identified in these waters for the first time.

HFPO-DA (hexafluoropropylene oxide-dimer acid) was originally developed as a more environmentally friendly alternative to a PFAS called PFOA (perfluorooctanoic acid). But it's now under scrutiny itself for the harm it can potentially have on both human health and the natural environment.

This is the first time HFPO-DA has been shown to travel long distances, as well as the first time it's appeared in the Arctic.

Water samples were taken from the Fram Strait, located between Svalbard and Greenland, which is the main connection between the Arctic Ocean and the Atlantic Ocean.

That substances old and new are turning up here is concerning, but the research should give us new insight into how these chemicals are circulating.

"The PFAS depth profiles in Fram Strait demonstrate that knowledge of the ocean circulation, vertical and lateral stratification, as well as physical mixing processes is crucial for understanding the large-scale distribution and fate of PFASs," write the researchers in their published paper.

Higher levels of PFAS were detected in the water going out of the Arctic Ocean compared with the water flowing in from the North Atlantic, suggesting these substances arrived through sources in the atmosphere rather than the ocean.

There are more than 5,000 PFAS, and some of them have previously been linked to cancer and liver disease, which is why many of them have now been phased out of manufacturing - including the chemical that HFPO-DA was intended to replace.

But even as the most toxic PFAS are banned, it's going to be thousands of years before some of them break down in the environment, which is why studies like the one carried out in the Arctic Ocean are so important to assessing the risks and the spread of these substances.

"More information on the vertical distribution of PFASs in the oceans is essential to reduce uncertainties in global PFAS mass balances and assess the role of the oceans as a sink of PFAS," write the researchers in their published paper.

The research has been published in Environmental Science & Technology.