Plenty of money will change hands at retail operations great and small over the next few weeks, but a new study finds that coins actually do change the human hands that grip them to produce a distinctive metallic odor.
In a recent study, a team of Virginia Tech environmental engineers explained the source of the metallic odor generated when people handle keys, change or other metal objects.
"The odors humans perceive as 'metallic' are really byproducts of the metals reacting with skin or impurities in the metal itself" — essentially, a type of human body odor rather than from the metal itself, said Andrea Dietrich, the lead author of the study.
"We're the first to demonstrate that there are no iron atoms in the odors humans describe from handling metal." Instead, the compounds people smell are from metal-induced oxidation of skin oils and sweat.
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Dietrich and her team are studying odors associated with metals under a National Science Foundation grant mainly aimed at solving aesthetic problems associated with water pipes, and particularly old iron pipes.
But because the makeup of smelly byproduct molecules depends on which organic substances are reacting, the researchers think their findings may help identify not just problem odors in water, but also possibly aid doctors searching for disease markers related to oxidative damage to cells in sweat or other body fluids.
One of the chemicals produced when skin comes in contact with metal is called 1-octen-3-one, which has a mushroom-metallic smell and a very low odor threshold. Humans can smell it at concentrations as low as 5 parts per trillion.
The scent also emanates from iron in blood. "We speculate that the 'blood scent' may result from skin reacting with ferrous iron, because the same metallic odor is produced if you rub blood on skin," Dietrich said.
So, a human ability to smell blood so sensitively "may have provided an evolutionary advantage that allowed humans to track wounded comrades or prey," she added.
