What is formalin?

Formalin is a 37% aqueous (water) solution of formaldehyde and is an authorised medicine. Formaldehyde is the active ingredient that is used to treat some waterborne micro-organisms. Formaldehyde occurs naturally in the environment.

Why is it used?

Like all other livestock sectors, salmon farmers use licensed veterinary medicines and compounds (such as disinfectants) as part of their integrated approach to protecting the health and welfare of their fish.

Formaldehyde is used to protect our young salmon from naturally occurring water-bourne micro-organisms such as Saprolegnia during their freshwater stage of life. There are many different species of Saprolegnia and they are found in almost all freshwater environments.

Saprolegnia are fungal-like organisms that can infect fish at all freshwater developmental stages. If left untreated such infections can be serious for the fish and potentially lead to death.  For that reason treatment with formaldehyde is sometimes a vital and necessary part of salmon farming, to ensure fish health and welfare.

How is it administered?

Fish are treated with formaldehyde through what is known as a “bath treatment”.  Formaldehyde is added to the water and fish are “bathed” in a weak solution for a short period of time, after which the treatment is safely flushed away.

For our open net farms in freshwater lochs we create a bath using a tarpaulin to reduce the quantity of water we need to treat and thereby reduce the quantity of medicine we need to use.

How does it affect the environment?

Formaldehyde itself is a naturally occurring compound that swiftly breaks down in water and is therefore safe to use for both fish and the environment.

Is it safe to eat salmon treated with formaldehyde?

YES. This product is only used in our freshwater facilities. Our fish then have many months, typically at least 18 months at sea where they are reared prior to harvesting for the food chain. This time at sea means that no formaldehyde residues are present in our fish when they are harvested for food consumption.

Even if fish were to be consumed at the freshwater stage they would still be safe to eat as formalin has a very short 'withdrawal period' of less than a day.

What is a 'withdrawal period'?

A withdrawal period is the minimum time before harvest during which treatment with a veterinary medicine must cease to ensure that any residues of veterinary medicines in the edible parts of the aquaculture product are within the limits established for the safety of consumers.

How is its use controlled?

The use of any medicines, disinfectants and other compounds are strictly controlled by several regulatory authorities. Products are produced and distributed through a safe and fully traceable supply chain. Compounds used on fish farms are heavily and strictly regulated.

The use of formaldehyde-based compounds is controlled by four main bodies - the Veterinary Medicine Directorate (VMD), Food Standards Sctoland (FSS), Scottish Environmental Protection Agency (SEPA) and Health & Safety Executive (HSE).

Where can I find out more?

You can find out more about formaldehyde and its everyday uses in everything from healthcare products to furniture production by clicking here.