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 Next to the American flag, there is no better visual
descriptor of Independence Day than a fireworks display. These luminary treats date
back to ancient China, and have been a part of celebrations and festivities in
the United States since
its inception. There's something about the loud noise and bright lights
that just makes for a good time.
(<-- Credit: Smashing Magazine)
But what about the pollution concern? Are we filling our
environment with dangerous chemicals when we shoot fireworks into the skies? Are
the distinct gunpowder-smelling fumes a problem, or are environmentalists just
blowing smoke? (<-- Yes, very punny sir) Let's take a look at the different
components of fireworks.
Fuel - As a fuel
source, fireworks commonly use a blend of charcoal and sulfur in the form of
black powder (gunpowder). Consequently, lighting and burning fireworks creates
clouds of smoke along with a recognizable burnt sulfurous smell. Particulate
matter (unburned solids) in this smoke has been known to affect those with
asthma, and prolonged exposure to the particles has been linked to cases of
lung cancer. Typically, however, concerning levels of particulates within an
area only last a few hours after an average fireworks show before they
dissipate.
 (Smoke hanging from fireworks at a football game. Credit: bengalstornado.com -->)
Oxidizer - Original
blends of gunpowder contain potassium nitrate as an oxidizer, though
pyrotechnic manufacturers often use perchlorates, which are more stable and
less messy. As a result, the lakes above where fireworks are shot often contain
perchlorate contamination. Perchlorates (such as ammonium perchlorate and
potassium perchlorate) are salts derived from perchloric acid (HClO4). In large doses, they can have adverse effects
on the thyroid gland in some animals. However, studies
have led experts to believe that perchlorates do not pose a risk for thyroid
cancer in humans, especially from the minimal levels caused by fireworks (which
last between 20 to 80 days
after a large display).
Coloring Agents -
The most environmentally concerning elements of fireworks are the metals used
to given the spectacles their various hues. Often there are specific chemicals
used for certain colors. Some of them are as follows:
Strontium - red
Copper - blue
Barium - green
Sodium - Yellow/orange
Calcium - orange
Aluminum - white
Rubidium - purple
Other types of metals such as cadmium can be used to produce
a variety of different colors.  These elements will not dissipate like
perchlorates or smoke, and many are known to be carcinogens or toxins in the
human body. However, studies have been inconclusive as to the contribution of
fireworks to water pollution by heavy metals.
Other pollutants
- As with any high temperature combustion in air, fireworks create nitrogen
oxides (NOx); they also produce sulfur oxides (SOx) because of their sulfur
content. These acid gases are key contributors to smog and acid rain. However,
the levels delivered by fireworks are miniscule in comparison to other man-made
sources (e.g. coal power plants) and natural sources (e.g. lightning).
Short term incidents (like
New Years in China) and "firework fallout" from large displays makes it
easy for some to incriminate fireworks as polluters. However, from what I've
gathered, there isn't much evidence that these pyrotechnic thrills pose a major
threat to air quality. I probably wouldn't want to be shooting them off and
breathing in the residuals every night, but for those that do there are
smoke-free alternatives and those that are purposely made with less toxic
colorants. For the rest of us, don't let a fear of air pollution kill the
celebratory fun this holiday week. Fireworks are to the 4th of July
as candy is to Halloween, so enjoy the show and let those rockets soar!
(<-- Credit: Instructables.com)
References
Are
fireworks bad for the environment? - mnn.com
The
Chemistry of Fireworks - Imperial College London
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