Scientists reported that about millions of dollars worth of gold and silver float through Switzerland's sewer systems every year.
A study by environmental chemists Eawag discovered 1.5 million francs worth of gold and silver each are lost through sludge from wastewater treatment plants in addition to rare earth metals such as gadolinium and the heavy metal niobium.
"Trace elements are increasingly widely used in the high-tech and medical sectors - for example, the transition metal tantalum and the semimetal germanium in electronic components, niobium and titanium in alloys and coatings, or gadolinium as a contrast medium and in luminous paints," the study said. "While the ultimate fate of the various elements has been little studied to date, a large proportion is known to enter wastewater."
Eawag said that distribution of the trace amounts of precious metals varies greatly throughout the country but were elevated in Jura, likely due to the presence of the watchmaking industry.
Scientists determined it's not worthwhile to recover the trace amounts of the elements outside of exceptional cases.
"The recovery of metals from wastewater or sludge is scarcely worthwhile at present, either financially or in terms of the amounts which could be extracted," the study said.
The concentrations of elements pose no risk to the environment as most cases lay below harmful limits.