Nearly 200 fish farms are allowed to use a carcinogenic chemical called formaldehyde which is used to embalm corpses, The Ferret can reveal.

Documents disclosed under freedom of information law reveal that 184 Scottish fish farms are permitted to use formaldehyde in a solution called formalin, which is used as a disinfectant to guard against parasites and diseases.

Formaldehyde has been famously used by artist Damien Hirst to preserve dead animals such as cows, lambs and sharks. Formalin is a water solution containing formaldehyde which is legal to use, but there are concerns over its safety.


In India last year, for example, there was a scare over preserved fish laced with the chemical, prompting a ban on fish imports in Goa state.

The UK government classified formaldehyde as a carcinogen in 2016 which means there are restrictions on its use, but it is permitted for use by the caged salmon industry.

The campaign group, Scottish Salmon Watch (SSW), which obtained the documents, wants formaldehyde banned. Concerns have been expressed over the potential of formalin leaks into river, lochs and seas.

Mass deaths: nine million fish killed by diseases at Scottish salmon farms

The documents were released by the Scottish Environmental Protection Agency (Sepa). They reveal that a company called Mowi, formerly known as Marine Harvest, used 50.7 tonnes of formalin between May 2017 and September 2018 on salmon farms at Loch Shiel, Loch Arkaig, Loch Lochy and Loch Garry.

One document revealed there was an “accidental overdose” of formalin at Mowi’s Glenfinnan salmon farm at Loch Shiel in October 2017. This was “due to human error” leading to 1,343 dead fish.

As part of its investigation, SSW filmed vats of formaldehyde labelled “corrosive” and “toxic” this month outside The Scottish Salmon Company‘s Russel Burn Hatchery on the shore of Loch Kishorn.

Don Staniford, director of Scottish Salmon Watch, said: “The salmon farming industry uses formaldehyde, via a formalin solution, as a disinfectant to guard against parasites and diseases although there are fish welfare and environmental concerns as well as human health impacts due to its carcinogenicity.

“The use of carcinogenic chemicals such as formaldehyde on salmon farms should be banned immediately. A public register of all chemicals used by salmon farms in Scotland is urgently required. The public surely have a right to know which toxic chemicals – including formaldehyde – are being used at which salmon farms.”

The use of carcinogenic chemicals such as formaldehyde on salmon farms should be banned immediately. Don Staniford, Scottish Salmon Watch

Certain restrictions apply to the use of formalin because it is deemed a “substance presumed to have carcinogenic potential for humans”.

Guidance from the UK Department for Environment Food and Rural Affairs says: “Fish, poultry, sheep and cattle farmers – as professionals – will be able to continue to use products containing formaldehyde for dis-infection, fumigation and foot bathing purposes.

“Whoever is physically using the product must be competent enough to meet the restrictions and precautions detailed by the labelling. There is no requirement to prove competency before purchase and use.

“However if a health and safety issue arose through its use and be (sic) investigated, and the person using it found not to have been suitably trained and competent, then there could be grounds for prosecution.”

John Aitchison, of Coastal Communities Network, Scotland, said any discharge of toxic chemicals from salmon farms and hatcheries into Scotland’s rivers and sea “is a real cause for concern”.

He added: “That an overdose of formaldehyde/formalin killed 1,343 fish shows that this is a potent chemical. It has no place being dumped into rivers or the sea, where it can harm wild animal and where people from coastal communities live or make their living,” he added.

Aquaculture chemicals used to treat farmed fish can also kill or harm crustaceans that many fishermen depend on catching, Aitchison argued.

He added: “Sepa allows fish farms and well boats to discharge of another toxic compound, hydrogen peroxide, without any licence being required. This chemical is used in huge quantities, then dumped straight into the sea, despite research in Norway showing that it can kill commercially-fished crustacean species days later.”

Formalin is used to protect small salmon in our freshwater farms from water-borne bacteria. Safe use of the product is licensed by Sepa. Ian Roberts, Mowi

Ian Roberts, spokesman for Mowi said: “We can confirm that human error during application of formalin in 2017 resulted in the unfortunate loss of about 1,300 juvenile salmon. When realised, we quickly rectified the situation and have since ensured it hasn’t occurred again.

“Formalin is used to protect small salmon in our freshwater farms from water-borne bacteria. Safe use of the product is licensed by Sepa under the Controlled Activities Regulations, following Sepa’s established environmental risk assessment that ensures product application meets environmental quality standards. Formaldehyde biodegrades quickly in water after contact with bacteria and/or sunlight.”

The Scottish Salmon Company was asked for a comment but referred us to the Scottish Salmon Producers’ Organisation (SSPO) which represents Scotland’s farmed salmon industry.

SSPO pointed out that formalin was a full licensed medicine approved by Sepa for use in freshwater to protect fish health. “It is a dilute form of formaldehyde, which is a naturally occurring compound,” said an SSPO spokesperson.

“After use it swiftly breaks down and is, therefore, safe to use for both fish and the environment.  Fish farmers are fully trained in the correct usage of any medicinal product used to protect fish health and welfare.”

The Soil Association, which grants organic status to fish farms, said formalin may be used twice per year maximum under the direction of a farm’s contracted vet.

The association’s spokesman added: “However, if the production cycle is less than 18 months you may use parasite treatments once per year. This is highly regulated. Fish farmers must obtain prior approval from their certification officer for all parasite treatments on each occasion, and must give preference to the use of cleaner fish for biological control of ectoparasites or freshwater, marine water and sodium chloride solutions.

“The use of this treatment must also be within their Sepa license and is at very low concentrations.”

According to Sepa, uncontrolled releases of formaldehyde had “the potential to cause significant harm” to the environment. “It is therefore important to ensure that formaldehyde is stored, handled and used appropriately to minimise the risk of any uncontrolled releases,” said a Sepa spokesperson.

“The use of formaldehyde is authorised at the Russel Burn hatchery by Sepa and the operators are required to record each individual use of formaldehyde. These records are audited as part of Sepa’s routine compliance inspections.”

The spokesperson added: “We take any allegations of environmental breaches very seriously and as an evidenced based organisation we would always take action to investigate where information comes to light. We would therefore encourage anyone with information of non-compliance to contact Sepa, in confidence, via the pollution hotline 0800 80 70 60.”

Fish farming industry bids to relax limits on toxic pesticide

Earlier this month The Ferret revealed that the salmon farming industry was pushing behind the scenes for environmental limits on a toxic pesticide to be 100 times weaker than government regulators recommend.

The pesticide’s US manufacturer, Merck, and SSPO, funded a study arguing that wildlife in sea lochs could withstand high concentrations of the pesticide.

The industry’s move to relax the limits was condemned as “beyond belief” by community groups, while environmentalists urged fish farmers to protect wildlife by ceasing to use the pesticide. The industry, however, insisted that it had confidence in its science.

The documents released by the Scottish Environment Protection Agency

This story was published in tandem with the Sunday National.


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