There's no need to worry about the effects of nanoparticles on human health, it appears - we've all been surrounded by them for years.
Since the emergence of nanotechnology, there's been concern that the size alone of such particles makes them potentially hazardous. But, says a University of Oregon team, if you've ever eaten from silverware or worn copper jewelry, you've had a wide exposure to them already.
The chemists used high-powered transmission electron microscopes to observe miniscule metal nanoparticles being created quite naturally by silver articles such as wire, jewelry and eating utensils in contact with other surfaces.
It turns out, they say, that nanoparticles have been in contact with humans for thousands of years.
The researchers found that silver nanoparticles deposited on the surface of their electron microscope slides began to transform in size, shape and particle populations within a few hours, especially when exposed to humid air, water and light.
Similar behavior and new nanoparticle formation was observed when the study was extended to look at macro-sized silver objects such as wire or jewelry.
"Our findings show that nanoparticle 'size' may not be static, especially when particles are on surfaces. For this reason, we believe that environmental health and safety concerns should not be defined - or regulated - based upon size," says Oregon's James E Hutchison.
"In addition, the generation of nanoparticles from objects that humans have contacted for millennia suggests that humans have been exposed to these nanoparticles throughout time. Rather than raise concern, I think this suggests that we would have already linked exposure to these materials to health hazards if there were any."
Because copper behaved similarly to silver, the researchers theorize that their findings represent a general phenomenon for metals that are readily oxidized and reduced under certain environmental conditions.
Any potential federal regulation, the research team says, should take account of the presence of background levels of nanoparticles and their dynamic behavior in the environment.