Published December 30, 2015
Analyzing Nanosilver
in Consumer Products
by Kaine Korzekwa
A
lthough its antimicrobial properties make nanosilver a welcome addition to consumer products such
as socks and shirts, the amount of silver in many of
these products remains unknown. In an open access, 2010
paper in the Journal of Environmental Quality (see http://
bit.ly/1YigZJc), researchers from Arizona State University
(ASU) tested how much nanosilver was present in and
could be released from everyday items such as clothing,
medical masks and cloths, and personal care products such
as shampoo and toothpaste.
Photo courtesy of Adobe Stock
The overall goal of the work—recently named the best
study published in the journal during the past five years—
was to create a mechanism for consumers, product manufacturers, scientists, and policymakers to begin analyzing
the potential risks of nanosilver in products that people use
daily.
“There are a lot of these consumer products coming out
with engineered nanomaterials, and while there is research
into how [nanomaterials] are made, there is little research
on the actual products consumers buy,” says Troy Benn,
who led the study as an ASU doctoral student and now
works as a civil engineer for the state of Montana. “So what
we wanted to start looking at was the exposure side of the
environmental risk question.”
As environmental engineers, one of the team’s concerns was that nanosilver’s antimicrobial properties could
affect wastewater treatment systems that use bacteria to
remediate sewage waste. To help evaluate the environmental risk posed by consumer nanosilver, the researchers
doi:10.2134/csa2016-61-1-4
16 CSA News
looked at two important concepts: exposure rate and quantity.
Specifically, the team quantified the amount of nanosilver in 10 consumer products and how much silver they
released into tap water, airborne water droplets, and a
simulated landfill leachate. The quantities ranged from 1.4
to 270,000 µg/g of product.
The medical mask and cloth contained the highest
concentrations at 270,000 and 230,000 µg/g, respectively. In
contrast, the personal care products all contained less than
10 µg/g while the clothing ranged from 30 and 45 µg/g.
When it came to how much nanosilver was released, the
products varied widely. For example, the mask released
15.8 µg of silver, which was less than .01% of its total.
Meanwhile, the shirt released 2% of its silver, or 34 µg. The
personal care products, such as the toothpaste, shampoo,
and detergent, were assumed to release all of their silver
because they are used with water and disposed of.
“The basic conclusion of the work was we saw a huge
range of silver released from different products. So [nanosilver] is possibly used in these products in different ways,”
says Benn, adding that the type of water source can also
affect how much silver is released.
Based on a calculation by the team, a consumer could,
therefore, release about 470 µg of nanosilver into the sewage system per day. Although this may not seem like much,
Benn says, the quantities add up quickly when you consider
that each person is releasing that amount daily.
“In a highly urbanized area, maybe that is significant for
a couple of wastewater management systems, but in a less
continued on page 19
January 2016
and researchers who depend on federally funded research on the importance of science and their research to
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Nanosilver continued from page 16
dense population, maybe it›s not so bad,” he says. It’s going to depend on further
study and what people think the risk is.”
Benn also adds that the exposure route can differ depending on the product.
For example, because medical masks are worn over the mouth, the exposure
route will most likely be inhalation and not the same as with shirts and socks.
Many of the consumer products in the study end up in landfills, so the researchers also wanted to investigate if silver could be released once the products
were disposed of. To test this, products were put into a liquid that resembled
landfill leachate. With its release of 2,900 µg/L of silver, the medical cloth was
comparable to the USEPA’s toxicity characterization limit, which is set at 5,000
µg/L.
While the study did produce good baseline data on the amount of silver in
consumer products, Benn explains that quantification is only half of the risk
equation.
“In this study, we were really just looking at the potential exposure side of this
question, and the other very important side of that risk equation is the toxicity—
what’s the dose that’s going to cause an adverse effect,” he says. “So we’re still
kind of in the beginning states of developing the appropriate detection methods
for potential regulation.”
K. Korzekwa, contributing writer to CSA News magazine
Top JEQ Paper Recognized
The Journal of Environmental Quality (JEQ) recently bestowed its award
for the best paper published by the journal in the last five years (2010 to
2014). The winning, open access article, “The Release of Nanosilver from
Consumer Products Used in the Home” (published in 2010; see http://bit.
ly/1YigZJc), was chosen
for its originality and the
number of citations and
downloads it received
during the past five years,
as well as for being well
written and making a
significant contribution to
the field of environmental
science.
At the ASA, CSSA,
SSSA Annual Meeting
in Minneapolis, MN, last
November, JEQ Editor
Ed Gregorich (left)
presented the award to
co-author Kiril Hristovski
(right), who accepted it
on behalf of the entire
Arizona State University
research team.
January 2016
CSA News 19