In autumn 2017, Finnish health and safety authorities rebuked promoters of silver water for false advertising over claims that the liquid had health benefits.
However in spite of the official reprimand, an investigation by Yle's Swedish-language service has found that advocates of the substance continue to promote it for internal use.
Since 2010, EU regulations have banned the use of so-called colloidal silver for internal consumption. Silver water refers to water with a suspension of fine silver particles and appears as a clear liquid with no odour.
Many experts have raised concerns about the health risks of imbibing the liquid and in animal tests, it has been observed to cause damage to internal organs.
Svenska Yle reported Friday that in spite of warnings from Finnish authorities such as the Finnish Agency for Safety and Health (Fimea), the food safety watchdog Evira, the national health and welfare authority THL and the safety and chemicals agency Tukes, members of closed Facebook groups have been dispensing advice on using the prohibited substance.
According to the report, Finnish and Swedish firms promoting silver water have been advising parents on administering the liquid to sick children and even infants.
Toxicologist: Children and foetuses most susceptible
University of Eastern Finland toxicology professor Kirsi Vähäkangas said that she strongly advises against drinking colloidal silver, noting that silver is toxic when ingested.
"Silver is absorbed from the digestive tract and accumulates in the internal organs, in the kidneys and in the brain. It can lead to liver and kidney damage. Children and, in particular, foetuses are more susceptible to the toxic effects than adults. Older people are also more sensitive,” Vähäkangas said.
Many who drink silver water claim that colloidal silver is harmless, and that it is only silver nitrate that is harmful to humans.
"Silver is present in various forms, both in compounds such as silver nitrate and as metal as well as nanoparticles in colloidal silver. All forms of silver release silver ions, and the researchers assume that these ions produce the harmful effects. In a worst-case scenario, someone who drinks a lot of silver water can get silver poisoning, argyria, which colours the skin blue or gray,” she adds.
Since the Yle revelations last autumn, Vähäkangas has agreed to write the first Finnish-language overview of colloidal silver, which is awaiting publication.
Police have also intervened into the black market trade and launched investigations into two women alleged to have given their children silver water. Prosecutors are now considering charges in those cases.