LOCHS in Orkney, the Highlands and the Outer Hebrides are among waters containing high levels of toxic pollutants with health risks known as "forever chemicals", The Ferret can reveal.

More than a quarter of surface ­waters tested in Scotland contain ­unsafe levels of per- and polyfluoroalkyl substances (PFAS) - chemicals used in industrial processes and consumer products from non-stick cookware and food packaging, to ­waterproof clothing. Some of these "forever chemicals" have been linked to various diseases, including cancers.

According to our analysis of ­samples taken by Scottish Water, the sites are above a threshold for environmental safety proposed by the EU.

The worst site, a loch on the Isle of Lewis, tested 10 times over the safe standard. Others - from Orkney to the rural Highlands - were as much as four times over.

We can also reveal that the frequency of Scottish Water's testing for the chemicals has dropped sharply in the past year - from more than 200 samples a month to roughly 30.

One campaigner said the spread of industrial chemicals to some of Scotland's most remote waters was "really heartbreaking". Another living near the Lewis site said the results demonstrated the need for more testing, not less.

"You can't fight an enemy you don't know," said Janet Marshall, founder and chair of environmental group Clean Coast Outer Hebrides. "You've got to establish the nature of the beast."

Scottish Water said that none of its drinking water samples contained unsafe levels of PFAS, and that environmental risk was the purview of Sepa.

(Image: Andres Siimon)

Sepa said that "any potential ­exceedances of an environmental standard in water bodies in Scotland are a concern" and that it plans to ­publish fresh PFAS data "by the end of the year".

PFAS are a family of chemicals designed to be particularly long-lasting.

Used as lubricants in domestic and industrial products since the 1970s, recent research has linked the chemicals to reproductive and immune diseases as well as a number of cancers.

In the past, scientists have ­measured PFAS levels either by ­testing for a few of the most well­-known individual chemicals, or ­adding up the results for a shortlist of common ones.

Scientists now recognise that some PFAS chemicals are more toxic than others. The EU's parliament and council are currently considering a proposal to measure the environmental risk by giving 24 individual ­chemicals a weighted score.

The Ferret applied that weighted test to Scottish Water data seen under freedom of information law. Out of nearly 275 surface waters sampled since the utility began testing for PFAS in 2023, 73 would be considered unsafe under the EU proposals - just more than a quarter.

Loch ­Hatravat (or Atrabhat in Gaelic) on the northern tip of the Isle of Lewis scored more than 10 times over the safe limit. The Loch of Burness (on Westray in Orkney), Loch Lunndiadh (near Golspie) and one other site called "Allt Gharb" (which means "rough burn" in Gaelic and could refer to a number of places) were four times over the threshold.

All but 10 of the sites tested ­contain some level of at least one of the 24 toxic compounds.

Scottish Water tests at its sources for drinking water, before and after treatment. Because the EU's standard is only for surface waters, The Ferret excluded sampling at boreholes and other groundwater sources, and only ran the weighted test on raw samples taken before treatment.

Scottish Water puts its samples through a test for drinking water which involves adding the levels for 20 listed compounds. Asked about the findings, the utility questioned our methodology.

"It's not possible to compare the two as the environmental ­directive covers 24 different PFAS and the drinking water directive covers 20 different PFAS," a spokesperson claimed.

In fact, Scottish Water's full data ­includes results for 21 of the 24 ­chemicals listed in the EU's test. Where the utility did not test for a chemical, we assumed it was not ­present. We also assumed any ­values under the threshold for detection were not present. The results are therefore likely to be an ­underestimate.

(Image: PA)

We shared Scottish Water's data with The Rivers Trust, who ­performed similar analysis on ­results from ­surface waters in England ­earlier this year, and it agreed with the validity of our methodology.

Asked why it had reduced the ­frequency of testing for PFAS, Scottish Water said it is "fully engaged with ongoing work to understand the presence of PFAS in drinking water" and that "none of our sampling results across Scotland have so far come close to the drinking water standard".

The company added: "Our continued monitoring, inspection and risk assessment processes are seeking to build understanding of the factors behind higher concentrations, while recognising that these remain low relative to the rigorous standard set by our regulator for the safety of drinking water."

In its proposal for the newer test, the EU's commission describes the drinking water test used by Scottish Water as "less strict" and says the latter does not take into account the latest scientific advice from the ­European Food Safety Authority.

Sepa declined to comment in ­detail on the findings, but said that any ­potentially unsafe levels of pollutants were "a concern".

"Scientific understanding of the sources, environmental concentrations, and risks of PFAS in the ­environment continues to ­develop ­nationally and globally," a ­spokesperson said, adding that "­initial findings" from a monitoring "pilot project" will be available by the end of the year after they have been "validated and verified".

"Our new analytical methodology will allow us to increase the number of monitoring sites in our ­network, with the data helping to better ­characterise the distribution of PFAS in Scotland's environment."

Megan Kirton leads the anti-pollution charity Fidra's forever chemicals campaign, and welcomed Sepa's new results after "very slow progress". She told The Ferret: "We just need to turn off the tap of these ­chemicals. Then there should be emphasis on monitoring to make sure that the levels of PFAS are decreasing in the environment."

Kirton said that the location of the sites failing the EU's standard was as concerning as their levels and added: "That is really heartbreaking to hear. Beautiful, remote areas that are highly protected and nowhere near where these chemicals have been produced are still impacted. It's really hard to escape them."

While the EU deliberates its new PFAS limit, it remains unclear how industrial chemicals have spread through rural Scotland.

Todd Anderson is a professor of ­environmental chemistry and PFAS expert at Texas Tech ­University. Asked to review some of the highest-scoring samples, he said the mix of ­individual ­chemicals suggested ­possible ­pollution from fire fighting foam at small ­rural airports, or no single source at all.

"The concentrations seem to be more consistent with atmospheric deposition rather than a single point source," he added.

Atmospheric deposition describes a process where the toxic chemicals become airborne at an industrial site and are then transported, sometimes great distances, in water vapour or sea foam.

Last spring, a PFAS report from the Scottish Government's Centre of Expertise for Water concluded: "The role of sea spray aerosols [sea foam] in contamination especially of ­coastal catchments should be considered as a risk factor and its importance ­further investigated."

Marshall, founder of Clean Coast Outer Hebrides, lives on Lewis near Tolsta Head around the corner from the worst offending site. She said the scale of the pollution was "absolutely appalling" for such a secluded part of Scotland and that authorities like Sepa and Scottish Water should be more vigilant.

"It's not surprising, knowing how budgets have been cut, but we need so much more testing," she said. "Just because we can't see it doesn't mean it isn't hurting us."

"I'm looking up at the moorland [towards the loch] and it is very, very remote," she said. "For stuff to have presumably blown there is appalling."

The extent of PFAS's spread represents something concerning not just for individual sites, she said, but for our relationship with the environment at large.

"We - the public, big businesses and governments - don't twig the actual long term, difficult-to-fix problems before they're critically hard and extremely expensive to deal with," she said.

"For a long time, the natural world was regarded as so big that what we did didn't matter - and now we're at this terrible stage where we might have gone too far."