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Looking at Fireworks
From Environmental Science Perspective
By: Arun K. Attri
Without
any hesitation it can be stated that the sparkling and twinkling of
coloured lights exhilarates the visual senses of one and all. When this
display is coupled with the sound of explosive bursts it is considered
an expression of joyous affair; occasion can be marriage, new year,
Diwali or any other festival. On the other hand, scientific evidence is
mounting to reveal the immediate impact of such firework displays on
human health through pollution of air we breathe. Diwali festival had
been the focus of scientific investigations related to firework displays
and following adverse health impact.
In order to understand the gravity of the adverse health
related impact due to the fireworks, it is important to comprehend their
basic chemical composition. Firework activation represents a combustion
reaction, where the mixed ingredients are burnt. The most basic form of
fireworks, known as black powder, was discovered and used in China about
1000 years ago. It was a mixture of potassium nitrate, charcoal and
sulfur in 75:15:10 proportion. Black powder, even today, is used as an
explosive charge and propellant in shells and bullets. On ignition the
mixture produces, instantaneously gases and if the mixture is confined
inside a closed space explosion follows. The directed emission of gases
can propel the container like a rocket. From chemistry’s point of view
combustion requires the supply of oxygen; or oxidizing agent capable of
supplying large amount of oxygen. Commonly known oxidizers used in
fireworks are nitrates, chlorates and per-chlorate compounds. Reducing
agent capable of burning in the presence of oxygen supplied by the
oxidizer acts as fuel; sulfur and charcoal are few common reducers used
in making the fireworks. The loose mixture of oxidizer and reducer is
shaped and held together by using binding agent; starch dextrin or gum
arabic are common binders used to make the mixture more evenly
homogeneous. Bright sparkling colours emitted by different types of
fireworks require the addition of metal salts in black powder. Depending
upon the composition of oxidizer and reducer used, fireworks on ignition
can achieve very high temperature (1000 to 3000 0C). Metals,
when heated, at such temperatures, emit radiation covering a wide
spectral range, which includes the visible light of characteristic
colour.
Some of the common metal salts used to achieve the
emission of sparkling colours are: (a) Copper Acetoarsenate [Blue], (b)
Copper chloride [Turquoise], (c) Cryolite [Yellow], (d) Lithium
Carbonate [Brilliant Red], (e) Barium Carbonate [Green], (f) Barium
Chloride [Bright green] etc. In addition, the emission of bright white
sparkling light flashes effects require the mixing of magnesium and
aluminum salts into the mixture. The human eye can only see the
radiation emitted in visible spectral region. One of the little known
aspects associated with metal salts emitting radiation or light, when
heated at high temperature, was revealed in 2001(Nature vol 411, pp
1015).
Experiments clearly provided evidence that in addition to
the emitting of visually elating colours, metals at high temperature
also emit radiation in spectral region known as ultraviolet or UV.
Barium, copper, lithium, strontium, manganese, sodium salts when burnt
at temperatures produced by the ignition of fireworks emit significant
proportion of light having wavelength less than 240 nm (high energy UV
radiation). Consequences of this are alarming. First, the person
standing in the vicinity, where fireworks are ignited, will be exposed
to harmful UV radiation. Second, the high energy UV radiation are
readily absorbed by molecular oxygen present in the air. This results in
the splitting of molecular oxygen into atomic oxygen [O2
+ UV(Wavelength <240 nm ) à O + O].
Now, this is serious as atomic oxygen (O), thus produced,
is chemically very reactive and on reaction with molecular oxygen
produces ozone (O3),
a powerful oxidant. The experiments done recorded precisely this.
Fireworks emitting colour on ignition produced a burst of O3
production in the air surrounding the
ignited fireworks. This new finding unfolded another dimension
associated with firework displays, i.e. in addition to their potential
to pollute the air. Air we breathe, if contains ozone (powerful oxidant)
will damage the lung lining. The damage is likely to be more among
children.
In the wake of new scientific evidence, let us reflect
upon what all we know about the consequences of extensive firework
displays, as it happens on Diwali, New year, or any community related
festive occasion, taking into account the meteorological factors
prevailing during their celebrations.
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Large scale firework displays coincides with the
onset of the winter season. From sunset till morning, atmospheric
mixing height is low as compared to summer season. In simple terms,
whatever pollutants are injected into the lower atmosphere, have
less volume to mix in. This results in the further concentrating the
air pollutants.
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It is already established that the levels of
suspended particulate load (SPM), CO, NOx,
Hydrocarbons, SO2
increase to an unprecedented levels in
air. Pregnant women, children and those having a chronic asthma are
most vulnerable to the serious medical condition during firework
displays.
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UV light and ozone exposure make conditions more
undesirable.
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Meteorological conditions favour calm winds and this
will ensure removal of pollutants produced from fireworks hangs in
the air for long duration.
One of the most desirable aspect of our life is to have a
good quality of life, this requires that we respect the right of every
other individual to pursue the same. So, even if we have a great urgent
desire to ignite fireworks to seek personal gratification, we should
look again, are we not encroaching on the natural rights of others to
seek the availability of pollution free air to breathe? Best
celebrations are not at the cost of making others unhappy. It is time
to seek pollution free air and water and aspire for better quality of
life saying no to the fireworks will be a big step towards attaining it.
Prof. Arun K. Attri is Professor at School of
Environmental Sciences, Jawaharlal Nehru University, New Delhi- 110 067,
India ([email protected]) |
