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| Courtesy of theawesomer.com |
In honor of the upcoming Red Bull Stratos jump, today’s
topic is ozone! Ozone (O3) is a naturally occurring form of elemental
oxygen (known as an allotrope) which is present in the Earth’s atmosphere. Although ozone and pollution are often hot
topics in today’s news, ozone makes up approximately 0.6 parts per million
(ppm) of the atmosphere.1 Ozone’s concentrations, however, vary greatly within
different parts of the atmosphere with normal levels of 10 ppm at 100,000ft, 4
ppm at 50,000ft, less than 0.1 ppm below 40,000ft and typically 0.03ppm at sea
level.2 As a chemical, ozone is a very reactive gas which is
irritating to the eyes and lungs even at low concentrations, and yet the ozone
layer is largely responsible for shielding the Earth from some of the sun’s
harmful radiation. For our purposes, we’ll focus on the reactions with O3
that make it both useful in chemical synthesis, but harmful within the body.
In actuality, you’re probably more familiar with ozone than
you may believe. In addition to being made from combustion fumes, O3 is also
produced indoors by high voltage electrical equipment such as ionic air
purifiers, laser printers, photocopiers, tasers, arc welders, and even electric
drills. If you have ever smelled a sharp odor somewhat similar to bleach when
using these, you’ve most likely smelled O3! Luckily your body has
the ability to detect concentrations of about 0.003 ppm.3 Don’t be
too afraid, however, the ozone produced by these devices is quickly converted
back into O2 when it comes in contact with surfaces.
Within your body, ozone has the ability to function several
ways as a toxin. Although ozone itself is not a free radical, ozone readily
reacts with a number of biological molecules including amino acids, NADH, and
ascorbic acid (Vitamin C). Although the mechanisms can vary, these reactions
produce singlet oxygen (1O2) which can damage fats
(lipids) and proteins in cells, leading to oxidative stress within cells and possible
cell death. 4 One suggested mechanism involving lipid double bonds
is given below. Additionally, ozone can react with double bonds within cholesterol
in a similar fashion to produce compounds called atheronals, compounds which
naturally occur in the plaque of atherosclerotic arteries (arteries hardened by high cholesterol).
While O3 can have such negative effects, surprisingly
it is produced naturally in the body! White bloods cells produce the reactive
species as a means of destroying foreign species, such as bacteria. By this
measure, O3 within the body has a double edge effect, but a net
positive effect in protecting the human body from foreign invaders or mutated
cells.
References:
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