If you’ve ever eaten from silverware or worn copper jewelry, you’ve been in
a perfect storm in which nanoparticles were dropped into the environment, say
scientists at the University
of Oregon.
Since the emergence of nanotechnology, researchers, regulators, and the
public have been concerned that the potential toxicity of nano-sized products
might threaten human health by way of environmental exposure.
Now, with the help of high-powered transmission electron microscopes,
chemists captured never-before-seen views of miniscule metal nanoparticles
naturally being created by silver articles such as wire, jewelry, and eating
utensils in contact with other surfaces. It turns out, researchers say,
nanoparticles have been in contact with humans for a long, long time.
The project involved researchers in the UO’s Materials Science Institute
and the Safer Nanomaterials and Nanomanufacturing Initiative (SNNI), in
collaboration with UO technology spinoff Dune Sciences Inc. SNNI is an
initiative of the Oregon Nanoscience and Microtechnologies Institute (ONAMI), a
state signature research center dedicated to research, job growth, and
commercialization in the areas of nanoscale science and microtechnologies.
The research—detailed in a paper placed online in ACS Nano—focused on understanding the dynamic behavior of silver
nanoparticles on surfaces when exposed to a variety of environmental
conditions.
Using a new approach developed at UO that allows for the direct observation
of microscopic changes in nanoparticles over time, researchers found that
silver nanoparticles deposited on the surface of their SMART Grids 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 dynamic 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 James E. Hutchison, who holds the Lokey-Harrington Chair
in Chemistry. “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.”
Any potential federal regulatory policies, the research team concluded,
should allow for the presence of background levels of nanoparticles and their
dynamic behavior in the environment.
Because copper behaved similarly, the researchers theorize that their
findings represent a general phenomenon for metals readily oxidized and reduced
under certain environmental conditions. “These findings,” they wrote,
“challenge conventional thinking about nanoparticle reactivity and imply
that the production of new nanoparticles is an intrinsic property of the
material that is now strongly size dependent.”
While not addressed directly, Hutchison says, the naturally occurring and
spontaneous activity seen in the research suggests that exposure to toxic metal
ions, for example, might not be reduced simply by using larger particles in the
presence of living tissue or organisms.
