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---
  layout: post
  title: Cleaning the air with jeans
  author: Joe Schwarcz
  source: McGill Blogs
---
  HYPERLINK
"http://blogs.mcgill.ca/oss/2015/11/17/cleaning-the-air-with-jeans/" 
Cleaning the air with jeans 

  You may want them in your jeans, but you probably want to keep them
away from your genes. They’re “nano” particles of titanium
dioxide, about ten billionths of a meter in diameter that can exhibit
beneficial properties not possessed by their larger cousins, but they
may also have a darker side.

There are more jeans in the world than people. That stat sparked an idea
in the mind of University of Sheffield chemist Tony Ryan. Why not use
people’s penchant for wearing denim to help purify the air? After all,
the International Agency for Research on Cancer (IARC) classifies
outdoor air pollution in Group 1, reserved for substances that are known
to cause cancer in humans. It estimates that there are up to seven
million premature deaths in the world every year as a result of air
pollution.

With thoughts of reducing pollutants such as the nitrogen oxides and
volatile organic compounds emitted by vehicles, power plants,
residential heating, cooking and various consumer products, Ryan, in
partnership with former fashion designer Helen Storey, came up with the
concept of “Catalytic Clothing.”

“Catalytic” apparel uses fabric impregnated with nano-sized
particles of titanium dioxide to degrade air pollutants. “Nano”
means small. So small that the combined surface area of the
nanoparticles that are distributed through any fabric is immense. And
that matters because the action takes place on the surface of the
particles.

Titanium dioxide is a “photocatalyst,” meaning that it can make
chemical reactions happen when exposed to the right wavelength of light,
in this case ultraviolet. The light energy causes it to release
electrons that then target water molecules in the air, breaking them
apart to form extremely reactive hydroxyl radicals that then chop up
organic compounds into simple molecules such as carbon dioxide and
convert nitrogen oxides into water soluble nitric acid. This is not just
theory, it is well established technology that already has commercial
application, for example in “self-cleaning glass.” A thin layer of
titanium dioxide ends window cleaning worries, as long as the climate
provides for sufficient sunshine and rain. The chemical can even be
mixed into concrete, resulting in self-cleaning buildings such as the
Jubilee Church in Rome.

Thanks to titanium dioxide we may never have to confront yellow urinals
again. Coating the ceramic with a layer of titanium dioxide, about a
fiftieth the thickness of human hair, prevents stains from forming. The
technology also has potential in operating rooms where bacteria on floor
and wall tiles can be destroyed with fluorescent light, common in
hospitals, furnishing enough of the right wavelengths. And how about
self-cleaning tiles for the kitchen and bathroom?

Clearly, titanium dioxide photocatalysis is sound technology. But can
wearing jeans treated with this chemical actually have an impact on air
pollution? According to Professor Ryan, yes. He calculates that that if
a third of a million people in Sheffield wore such jeans, nitrogen oxide
levels could be significantly reduced. And there is no need to buy
special jeans. Titanium dioxide particles stick readily to the fabric so
the idea is to add a formulation of the chemical to the water when the
jeans are being laundered. The nano particles will stick until the
fabric degrades.

As is often the case in science, there is a “but.” What happens if
nanoparticles enter the bloodstream? What tissues might they affect?
Titanium dioxide has the potential to damage DNA, but to do that it has
to enter cells. That is a possibility since nanoparticles are smaller
than cells. In the lab, nano titanium dioxide has been shown to damage
DNA in human intestinal cells, but only at doses far higher than what
could ever be ingested.

In any case, people will not be dining on their treated jeans. But they
may be gulping donuts, or a vast array of other foods such as
Gobstoppers, M&Ms, pastries or soy milk that have titanium dioxide added
to them to provide a more pleasing whitened appearance. Only about 5% of
the titanium dioxide is made of nano sized particles, but that has
raised concern because IARC has classified titanium dioxide as possibly
carcinogenic to humans (Group 2B). This classification is based on
inhalation of titanium dioxide dust in an occupational setting, quite a
different exposure than eating a donut with a titanium dioxide enhanced
white sugar coating. Nevertheless consumer activism has resulted in
Dunkin Donuts removing titanium dioxide from the powdered sugar coating
on its products. Maybe it can be redirected into catalyst jeans. We
really don’t need to make junk food look more appealing, do we?

 

Joe Schwarcz – Nov 17th/2015