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FIREWORKS: THE THRILLS, THE RISK
1.1 BRIEF HISTORICAL BACKGROUND
Many people associate fireworks with Independence Day, but their original use was in New Year's celebrations. Do you know  how fireworks were invented? Legend tells of a Chinese cook who accidentally spilled saltpeter into a cooking fire, producing an interesting flame. Saltpeter, an ingredient in gunpowder, was used as a flavoring salt sometimes. The other gunpowder ingredients, charcoal and sulfur, also were common in early fires. Though the mixture burned with a pretty flame in a fire, it exploded if it was enclosed in a bamboo tube.
This serendipitous invention of gunpowder appears to have occurred about 2000 years ago, with exploding firecrackers produced later during the Song dynasty (960-1279) by a Chinese monk named Li Tian, who lived near the city of Liu Yang in Hunan Province. These firecrackers were bamboo shoots filled with gunpowder. They were exploded at the commencement of the new year to scare away evil spirits. Much of the modern focus of fireworks is on light and color, but loud noise (known as "gung pow" or "bian pao") was desirable in a religious firework, since that was what frightened the spirits. By the 15th century, fireworks were a traditional part of other celebrations, such as military victories and weddings. The Chinese story is well-known, though it is possible fireworks really were invented in India or Arabia.
Chemistry is the true designer of modern fireworks, but our colorful displays are the result of thousands of years of experimentation and trial and error. Fireworks originated in China, and date back to the 10th century, and were simply made of tubes of bamboo packed with black powder. The art of fireworks has changed and evolved drastically over the last 1000 years, and these days, the most common displays of fireworks involve holiday celebrations such as The Fourth of July in the USA and New Year’s Eve in some countries. Many amusement parks and tourist attractions also launch fireworks nightly for guests.

Fig.1.0 Fireworks on display
They were commonly used for large shows, ceremonies, and displays, and progressed into unlikely aids on the battlefield, as rocket propulsion became common in warfare. In the 13th century, Arabs learned about gunpowder from the Chinese, and for several years, they were often called “Chinese Flowers.”
During this time, explosive pyrotechnics became an individualized profession, and experts were revered for their ability to understand various complex techniques for these colorful displays.
In the 17th century, Chinese culture began influencing art throughout Europe, and “chinoiserie” or “Chinese-esque” styles became very popular. Fireworks began to gain popularity throughout Europe during this time. In the late 1700’s, attempts to understand the mysteries of Chinese fireworks were common, and the recreational and ceremonial uses became widespread.
The advanced science behind fireworks has grown, but the manufacturing process still seems relatively simple. Most fireworks are still made in China, where people glue bits and pieces together by hand, rather than using high-tech machinery. However, most modern and traditional fireworks today use highly purified chemicals, which burn in much brighter and richer colors than ever before, providing us with rich reds and blues for our Independence Day as well as other celebrations.

Fig 1.2
These days, the most advanced part of a fireworks display comes from the firing mechanism. Rather than using long fuses and flares, pyrotechnicians use electric matches and computer firing systems for precise firing in sync with music or other fireworks displays.
There are a few specific reasons as to why fireworks are a main display for America’s birthday. For starters, when Francis Scott Key witnessed the Battle of Fort McHenry during the War of 1812, he was moved to poetry, and included the line, “And the rockets’ red glare, the bombs bursting in air,” which many people associate with the patriotic fireworks displays. There is, however, another reason for fireworks each year on July 4th. America’s second President, John Adams, was ecstatic about Independence Day and declared,
“It ought to be solemnized with Pomp and Parade, with Shews, Games, Sports, Guns, Bells, Bonfires and Illuminations from one End of this Continent to the other from this Time forward forever more.”
2.0 THE CHEMISTRY OF FIREWORKS COLOURS
Creating firework colours is a complex endeavor, requiring considerable art and application of physical science. Excluding propellants or special effects, the points of light ejected from fireworks, termed 'stars', generally require an oxygen-producer, fuel, binder (to keep everything where it needs to be), and colour producer. There are two main mechanisms of colour production in fireworks, namely incandescence and luminescence.
(i) Incandescence:  Incandescence is light produced from heat. Heat causes a substance to become hot and glow, initially emitting infrared, then red, orange, yellow, and white light as it becomes increasingly hotter. When the temperature of a firework is controlled, the glow of components, such as charcoal, can be manipulated to be the desired colour at the proper time. Metals, such as aluminum, magnesium, and titanium, burn very brightly and are useful for increasing the temperature of firework.
(ii) Luminescence: Luminescence is light produced using energy sources other than heat. Sometimes luminescence is called 'cold light', because it can occur at room temperature and cooler temperatures. To produce luminescence, energy is absorbed by an electron of an atom or molecule, causing it to become excited, but unstable. When the electron returns to a lower energy state the energy is released in the form of a photon (light). The energy of the photon determines its wavelength or colour.
Sometimes the salts needed to produce the desired colour are unstable. Barium chloride (green) is unstable at room temperatures, so barium must be combined with a more stable compound (e.g., chlorinated rubber). In this case, the chlorine is released in the heat of the burning of the pyrotechnic composition, to then form barium chloride and produce the green colour. Copper chloride (blue), on the other hand, is unstable at high temperatures, so the firework cannot get too hot, yet must be bright enough to be seen.
2.1. Quality
Pure colours require pure ingredients. Even trace amounts of Sodium impurities (yellow-orange) are sufficient to overpower or alter other colors. Careful formulation is required so that too much smoke or residue doesn't mask the colour. With fireworks, as with other things, cost often relates to quality. Skill of the manufacturer and date the firework was produced greatly affect the final display (or lack thereof).

3.0 HOW FIREWORKS WORK

Fireworks have been a traditional part of New Year's celebrations since they were invented. Today fireworks displays are seen on most holidays. Have you ever wondered how they work? There are different types of fireworks. Firecrackers, sparklers, and aerial shells are all examples of fireworks. Though they share some common characteristics, each type works a little differently.
(i) Firecrackers: Firecrackers are the original fireworks. In their simplest form, firecrackers consists of gunpowder wrapped in paper, with a fuse. Gunpowder consists of 75% potassium nitrate (KNO3), 15% charcoal (carbon) or sugar, and 10% sulfur. The materials will react with each other when enough heat is applied. Lighting the fuse supplies the heat to light a firecracker. The charcoal or sugar is the fuel. Potassium nitrate is the oxidizer, and sulfur moderates the reaction. Carbon (from the charcoal or sugar) plus oxygen (from the air and the potassium nitrate) forms carbon dioxide and energy. Potassium nitrate, sulfur, and carbon react to form nitrogen and carbon dioxide gases and potassium sulfide. The pressure from the expanding nitrogen and carbon dioxide explode the paper wrapper of a firecracker. The loud bang is the pop of the wrapper being blown apart.
(ii) Sparklers: A sparkler consists of a chemical mixture that is molded onto a rigid stick or wire. These chemicals often are mixed with water to form slurry that can be coated on a wire (by dipping) or poured into a tube. Once the mixture dries, you have a sparkler. Aluminum, iron, steel, zinc or magnesium dust or flakes may be used to create the bright, shimmering sparks. An example of a simple sparkler recipe consists of potassium perchlorate and dextrin, mixed with water to coat a stick, then dipped in aluminum flakes. The metal flakes heat up until they are incandescent and shine brightly or, at a high enough temperature, actually burn. A variety of chemicals can be added to create colours. The fuel and oxidizer are proportioned, along with the other chemicals, so that the sparkler burns slowly rather than exploding like a firecracker. Once one end of the sparkler is ignited, it burns progressively to the other end. In theory, the end of the stick or wire is suitable to support it while burning.
(iii) Rockets & Aerial Shells: When most people think of 'fireworks' an aerial shell probably comes to mind. These are the fireworks that are shot into the sky to explode. Some modern fireworks are launched using compressed air as a propellant and exploded using an electronic timer, but most aerial shells remain launched and exploded using gunpowder. Gunpowder-based aerial shells essentially function like two-stage rockets. The first stage of an aerial shell is a tube containing gunpowder that is lit with a fuse much like a large firecracker. The difference is that the gunpowder is used to propel the firework into the air rather than explode the tube. There is a hole at the bottom of the firework so the expanding nitrogen and carbon dioxide gases launch the firework into the sky. The second stage of the aerial shell is a package of gunpowder, more oxidizer, and colorants. The packing of the components determines the shape of the firework.


2.3. Firework Colorants
Color
Compound
Red
Strontium salts; e.g strontium carbonate (SrCO2)
Lithium Salts; e.g Lithium Carbonate (Li2CO3)

Orange
Calcium salts; e.g Calcium Chloride (CaCl2), Calcium Sulfate (CaSO4.xH2O), where x=0,1,2,3,5

Gold
incandescence of iron (with carbon), charcoal, or lampblack
Yellow
Sodium compounds; e.g sodium nitrate (NaNO3) cryolite (Na3AlF6)


Electric White
White-hot metal,such as magnesium or aluminum barium oxide, BaO

Green
barium compounds + chlorine producer
barium chloride, BaCl+ = bright green
Blue
copper compounds + chlorine producer
copper acetoarsenite (Paris Green), Cu3As2O3Cu(C2H3O2)2 = blue
copper (I) chloride, CuCl = turquoise blue
Purple
mixture of strontium (red) and copper (blue) compounds
Silver
burning aluminum, titanium, or magnesium powder or flakes

Table 2.0
FIREWORKS POLLUTION
Fireworks consist of a wide range of products with a highly variable composition. The available data on fireworks (safety, environmental effects) are often incomplete. This applies also to consumption figures, which can only be estimated. Every year, some 1,450 tonnes of fireworks are set off in Switzerland. About 1000 tonnes of this consists of materials such as tubes, structural parts and packaging (cardboard, wood, plastic), and 360 tonnes of the pyrotechnic components. These consist of approximately 240 tonnes of black powder (gunpowder) and 120 tonnes of chemicals to produce effects. These effects mixtures contain metallic compounds that may have an impact on the environment or human health.
1. Accidents: Accidents can occur if fireworks are handled incorrectly during sale and use.
Safety regulations for the sale of fireworks in some countries e.g Switzerland are contained in the Ordinance on Explosives. Regulations for the use of fireworks are published by the industrial association.
International surveys have shown that the accident rates associated with fireworks are around 2 - 13 accidents with injury to persons per 100,000 inhabitants.  Minors are disproportionately represented among the injured. This group is thus exposed to a higher risk. Every year, fireworks
cause fires in countries that use them in large quantities.
2. Noise: At the distances where people watching fireworks usually are, noise levels can exceed the impulse noise limit according to SUVA (Capital of Fiji) guidelines. The nuisance of firework noise should not be ignored.For noise-sensitive groups, this nuisance can be substantial, since it causes anxiety and corresponding stress reactions. There are no studies of  this effect

3. Air pollution: In the combustion of fireworks, the main component (gunpowder) gives rise to the solid reaction products such as potassium carbonate, potassium sulphate and potassium sulphide, together with unreacted sulphur. The reaction products from effects mixtures are generally solids and consist of metal oxides and, less often, chlorides. The air pollution caused by firework reaction products is well documented by measurements in some countries. Fine particulates are notable in reaching record short-term pollution levels. International surveys - in more polluted areas - show that susceptible people may be measurably affected.

Dioxins can be released during the combustion of copper containing fireworks. Laboratory experiments, which investigated the extent of dioxin formation caused by setting off various pyrotechnic devices, and measurements taken during Bonfire Night in Great Britain where both bonfires and fireworks are burned as in Switzerland, indicate that bonfires are a far more significant source of dioxin than pyrotechnic devices, especially when waste wood and other
wastes are burned.
4. Pollution of other environmental compartments and indirect effects: The firework reaction products that are emitted are deposited and thus enter the soil, crops and, in the case of fireworks over water, standing waters. This pollution has not been measured yet. Therefore, the deposition of firework-related elements must be estimated from model calculations.

Ecotoxicological and toxicological benchmarks for all firework-related elements were taken from literature. The present assessment shows that firework-related depositions do not cause problematic soil and water contents, and the evaluations suggest that indirect effects (uptake through the food chain, soil ingestion by children) are also not critical.

5.Waste: Some 1000 tons additional waste are annually generated by fireworks.    
4.0 HAZARDS OF FIREWORKS AND PROBABLE SOLUTIONS

Fig.4.0 Lagos Firecracker Warehouse Inferno
A fireworks warehouse in Jankara area of Lagos caught fire on Boxing Day (Dec. 26th 2012) as a result of multiple explosions caused by the Ariel shells stored in the house. The fire destroyed cars and properties of residents in nearby houses. One person was confirmed dead in the accident while many of the residents sustained injuries and were rushed to the hospital. According to a rescue worker, over 30 people had been treated for injuries. This goes a long way to show what disaster fireworks can cause.
Although firecrackers are banned in the country, Nigerians have continued to defy the ban, using them indiscriminately during festive periods.
The metallic particles in the smoke emitted by fireworks pose a health risk, particularly to people who suffer from asthma. This is the conclusion of a study led by researchers from the Institute of Environmental Assessment and Water Research “Instituto de Diagnostico Ambientaly Estudios del Agua- Consedo Superior de Investigations Cientificas” (IDAEA-CSIC).
"The toxicological research has shown that many of the metallic particles in the smoke from fireworks are bio-reactive and can affect human health," Teresa Moreno, a researcher from the IDAEA (CSIC) and lead author of a study that has been published in the Journal of Hazardous Materials, said.
The different colours and effects produced in these displays are achieved by adding metals to the gunpowder. When a pyrotechnic display takes place it releases a lot of smoke, liberating minute metallic particles (of a few microns in size, or even less), which are small enough to be inhaled deeply into the lungs."This poses a risk to health, and the effects are probably more acute in people with a background of asthma or cardiovascular problems," Moreno explains. "The effects in healthy people are still unknown, but common sense tells us it cannot be good to inhale the high levels of metallic particles in this smoke, even if this only happens a few times a year."
In an analysis to confirm the presence of over 30 chemical elements and compounds in the Spanish city of  Girona, it was observed that levels of these elements increase over time, as well as others such as aluminium, titanium, barium and antimony, and also concentrations of nitric oxide (NO) and sulphur dioxide (SO2). Other studies have confirmed that the smoke from fireworks increases the presence of metallic particles in the skies during celebrations.
"People who live in cities already inhale significant amounts of contaminant particles stemming from traffic emissions, chimneys and cigarettes, and the dense smoke caused by fireworks only worsens this situation," points out Moreno.
4.1 Possible solutions
Firework scenario can be compared with that of tobacco. "The less you expose yourself to the smoke, the fewer negative effects it will have on your health, and so the best solution is to avoid inhaling it."
For countries where there is total ban on importation and the use of fireworks the rule should properly be enforced in order enhance safety of life and properties. Whereas in countries where there is no ban, spectators should stay well back in a place not affected by the smoke and pay attention to the wind direction. It is also recommended that fireworks displays should be sited in a place that ensures the plume of smoke will blow away from densely populated areas. Also for the aerial shell people should be conscious of how they store it, and how they use it for the safety of all.
An added problem is the chemical mixtures in the different kinds of fireworks, since some contain extremely toxic metals such as lead. "There should be strict controls on fireworks imports so that those with the potentially most dangerous chemical composition can be avoided”. Otherwise total ban of it will be the best.
REFERENCES.
Anne Marie Helmenstine, Ph.D.; Famous Chemistry Inventions      chemistry.about.com/od/historyofchemistry/a/fireworkhistory.

Anne Marie Helmenstine, Ph.D.; The Chemistry of Fireworks colours
              http://chemistry.about.com/od/fireworkspyrotechnics/a/fireworkcolour
            
             Mary Bellis;   Early Rocket and Gun Powder
           http:// inventors.about.com/od/rstartinventions/a/SolidPropellant_3.

           Evelyn Usman,B. Adelaja and M. Olowoopeja; Firecrackers wreak havoc in Lagos
           Vanguard Thur 17th .Dec. 2012

 
 

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