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Four years ago Fisher and Paykel felt under pressure to use a "miracle" particle in its appliances because of its surrounding hype and novelty.

The ingredient was nanosilver - silver manipulated to a billionth of a metre - which was believed to eliminate fungus and bacteria with great efficacy.

It was added to clothing, medical products such as plasters and dressings, home cleaning products and fridges. Vials of nanosilver could also be bought in health shops for human consumption.

Samsung created "Silvercare" washing machines which claimed to release 400 billion nano-sized silver ions in the wash. This was caused by the "electrolysation" of silver plates within the machines.

Fisher and Paykel product developer Anna Duncan said the company conducted tests to see if there was an advantage in using the novel particles.

It concluded that washing clothes at 20C with detergent could achieve a 99.79 per cent elimination of bacteria. Samsung claimed its Silvercare range had a 99.9 per cent elimination rate.

"We really thought it was superfluous. There was no real benefit in using silver."

She said the company could not justify the environmental cost of using nanosilver for such a slender advantage.

Silver is known by the Environment Risk Management Authority to be toxic in aquatic ecosystems. It is classified as a hazardous substance in New Zealand.

Associate Professor of Physics at University of Canterbury Simon Brown said that there were strong indications nanosilver was also toxic, possibly even more toxic than in its bulk form. "Nanotechnologies are not by definition bad, or unsafe. It is largely a question of 'we don't know'. But with respect to nanosilver, there are enough early signals from scientific institutes saying 'let's hold up on this one until we understand it'."

Nanoscale silver used in washing machines could find its way into New Zealand's waterways. This would cause problems in sewage treatment stations, which rely on "good" bacteria to treat waste. Silver in particle form could also build up in the gills of fish.

Fisher and Paykel's decision was vindicated earlier this year when a German Federal Ministry for the Environment recommended the commercial use of nanosilver be avoided until more is known about the fate of the metal.