Chemistry

Fluoride is a group of compounds consisting of naturally occurring elements of fluorine plus one or more elements. These compounds are naturally found in water and soil. However, waters are still fluoridated through the process of fluoridation. Water fluoridation is a process that involves addition of fluoride into the amount of water in order to have about one particle of fluoride in every one million particles of water (ppm) or one milligram of fluoride in every one liter of water (mgL). This process is done to prevent tooth decay and optimal amount of fluoride has to be added in order to achieve that goal (Centers for Disease Control and Prevention, 1991). Fluoride is quite abundant and can be found in solid forms in minerals like fluorspar, apatite and cryolite. Fluorspar which is also known as the fluorite is the most common fluoride mineral around the world. It contains about 30-90 percent of calcium fluoride. The cryolite minerals on the other hand are composed of sodium, aluminum and fluoride. Cryolite has got low melting point which makes it unsuitable for water fluoridation but it is a preferred mineral for industrial use. The apatite mineral is a mixture of calcium compounds like calcium phosphate, calcium carbonates and calcium fluorides. It contains about 3-7 percent of fluoride and it is normally preferred for water fluoridation (British Fluoridation Society, n.d).
The process of fluoridation began in 1940s when scientific evidence revealed that those who resided in areas where water supply was rich in natural fluoride levels of about 1.0 ppm experienced low dental cavities. Recent studies have supported such claims and suggest that fluoride not only prevents tooth decay but may also reverse decay through the process of remineralization. The Americas Center For Disease Control has always hailed the fluoridation process as one of the greatest achievements of man in the twentieth century for it has numerous benefits (Centers for Disease Control and Prevention 1991). However, there are scientific evidences suggesting that the fluoridation is hazardous to human health. This paper will look at the benefits and the health of fluoridation process.

Health Benefits
Fluoride therapy is a common practice that is recommended by dentists as a useful preventive and curative measure to dental problems. Fluoride generally has three primary health benefits if used optimally and as recommended by the dentist.

Studies have shown that water fluoridation may reverse the decaying process of the tooth. The fluoride compound is said to promote the remineralization process of the teeth. The remineralization process is enhanced when the fluoride available in the saliva are absorb by the tooth surfaces where demineralization had started or had occurred. Fluoride present in the teeth would then attract some other minerals like calcium which together with the fluoride would be able to form a new tooth mineral (Chartered Institution of Water and Environmental Management, 2004).

One of the primary reasons of water fluoridation however, is that it helps prevent the decaying process. A fluoride is able to make the teeth resistant to the demineralization process. When the fluoride in the saliva is absorb by the tooth and together with other minerals forms a new tooth mineral through the remineralization process, a stronger compound than the initial one would be formed on the tooth thereby providing cover for the tooth. The teeth generally is a composition of carbonated hydroxypatite and hydroxypatite, but fluoride absorb by the teeth would introduced a new compound called fluorapatite as a result of the remineralization process. The presence of fluoride in this process and the subsequent formation of the fluorapatite make the teeth more resistant to demineralization which is caused by the dissolution of the teeth by acids (Committee to Coordinate Environmental Health and Related Programs, 1991).

Fluoride is also known to inhibit the ability of the oral bacteria to produce acids known to cause demineralization. Fluorides would limit the rate of acid production by the bacteria living in the dental plaque by not only disrupting the comfortability of the bacteria but also its sugar metabolism rate and ability. When the bacteria consumes less sugar it would produce less acid on and around the tooth hence less acid to be used in the demineralization process(Stookey, 1994).

Health Hazards
Dentists consider fluoride a prescription drug and just like any other prescription drug it has to be used as prescribed. Fluoride can be very lethal if consumed in large amounts but if it is used or consumed appropriately it can be very beneficial. The following are some of the health hazards of the fluoride and fluoridated water.

There are numerous health hazards posed by consumption of high amounts of the fluoride. Although, the question as to whether fluoride and how much should be added remains  with the water supplier, the Environmental  Protection Agency of the United States sets the maximum level at four mgL fluoride necessary for human use. One of the health hazards associated with the long term consumption of high levels of fluoride is bone disease.  Bone disease or skeletal fluolosis is as a result of excess systematic exposure to fluoride leading to such systematic effects (National Research Council. Carcinogenicity of fluoride. In Subcommittee on Health Effects of Ingested Fluoride, 1993).

High levels of fluoride are also known to cause fluorosis or browning as well as pitting of the teeth among young children. Studies suggest that high levels of fluoride are likely to affect the childs developing teeth before they fully emerge from the gums. Other studies reveal that about 10-15 percent of children who use the recommended amount of fluoride still experience some degree of dental fluorosis. The recommended amount of fluoride for young persons below nine is 2 mgL, however as the researches have revealed children may not be able to develop healthy teeth as anticipated. Acute overdose of fluoride may result into fluoride poisoning and death in both children and adults (Stookey, 1994).

While water fluoridation has always been credited for reducing tooth cavities among US populations, extensive research provide a gloomy picture of the success. It has been found that there is a surprising similarity in dental health improvement in both communities having or lacking fluorated water. It can therefore be explained that reduced tooth decay is a product of improvement in the dental health care, timely intervention as well as the availability of fluoride in toothpastes and in other dental products (DHoore  van Nieuwenhuysen, 1992). However, a lot of studies are recommended in this area for comprehensive and valid results.

Even with its magic as both a preventive and curative compound, there is simply no substitute to healthy dental practices. Oral hygiene and healthy nutrition would not only complement the magic of fluoride but would also ensure a healthy life. This means that the amount of sugar and acidic level in our foods should be minimized as well as the frequency of beverage exposure. This would ensure that the amount of sugar available for the oral bacteria is reduced and the subsequent release of acid by the bacteria is kept low.

Many of us might think that chemistry is just another science. For me, once I hear the word, a picture of a scientist mixing different chemicals in the laboratory immediately comes to mind. At least this was what I initially thought before taking this chemistry class. What now retains in my head is the fact that chemistry works in ways people might not have realized  from the food we eat, the clothes we wear, the cars we ride, the processes inside our bodies, the products we consume, the air we breathe, the environment we live in. Truly, all living processes are in one way or another controlled by chemical reactions (Chemistry 2011, n.d.). Hence for me, it seems my life is therefore is ruled by this science, including my studies and my future.

Yet how does chemistry fit into my major My current major is General Studies, in the Arts and Social Sciences field. After getting my degree, I plan to teach in elementary school. Thus, I see chemistry as a possible subject that I can teach my students. My general knowledge on chemistry acquired from this course will definitely aid me in teaching science to my students. Specifically and more importantly, the lessons I learned from how chemistry impacts our environment calls for me to educate the little ones about environmental factors and phenomena currently affecting our world such as global warming, pollution, air and water quality, and greenhouse emissions, among others. Since these are big words for such little minds, I will try to simplify them by using pictures and presentations that they can understand and appreciate.

With this, the children will be able to gain awareness on crucial matters affecting the world they live in so that they can do their share in improving the situation even in the simplest and smallest way they can. This goal is in fact in line with the recent declaration of the UN General Assembly that the year 2011 will be known as the International Year of Chemistry. The said resolution primarily aims to increase the interest of young people in chemistry, to heighten peoples appreciation of the science in meeting the worlds needs, and to generate enthusiasm for the creative future of chemistry (Chemistry 2011, n.d.). Furthermore, I also want to impart to my students the value of life and appreciating all its facets in whatever subject I will teach. Hence, my knowledge in chemistry will enable me to discuss the importance of some of the ordinary things, both living and non-living, to my students. For instance, teaching students about how crayons and paper came about in art class, telling them the story of how pens and pencils were made in English writing class, or explaining to them how rain is created in science class, among others. I can integrate chemistry concepts into my teaching and I plan to do this despite the fact that research has revealed that teaching chemistry is unpopular according to most students. This is due to the fact that its relevance has not been highlighted (Holbrook, 2005). Therefore, it is all the more necessary to include chemistry in whatever subject I will teach in the future.

However, I also aspire to work in the human services as my current minor is sociology. I specifically plan to involve myself with local communities as a social worker or a social and community service manager. Chemistry will come into play with the projects and programs that I will spearhead. For instance, basic understanding of human body systems and functions will aid in planning health programs, knowledge on various food components will be beneficial in doing food-related programs, and awareness on environmental problems and processes will help in advocating for clean, green, and sustainable projects for the community.
Therefore, whether I may end up being an elementary school teacher or a community service manager, the need to utilize some chemistry concepts and ideas is inevitable. Hence, the basic knowledge I gained in this course will definitely come in handy.

Urbanization and modernization have brought with them financial prosperity, economic betterment and a higher standard of comfort and living. However, man has sacrificed all the elements, with absolutely no consideration, only to achieve and accomplish prosperity at the cost of natures biodiversity and ecological balance. The world today faces the threat of extinction of innumerable species of plants and animals that have a right to stay on planet Earth more than us as they were its first occupants. The increasing pressure on farmlands to produce larger quantities of food to meet the ever increasing demands of a rapidly growing population has forced man to use harmful chemicals like insecticides, pesticides and weedicides in an abusive and unethical manner. This paper examines why harmful chemicals should not be used and suggests alternative modes and methods of insect and pest control.

The scenario that Rachel Carson describes in the book Silent Spring is one of utter chaos and melancholy. The numbers of natural pollinators like bees have declined in recent years due to the indiscriminate use of harmful chemicals. The earths environment has undergone major disastrous changes at the cost of feeding the worlds population. These chemicals are extremely invasive and settle in the tissues of plants and animals changing their intrinsic biological structure. Humans have also been largely affected by the intrusion of chemicals into their biological systems. Nearly five hundred new chemicals are developed every year in the United States alone to meet industrial requirements. Studies show that every year, on an average, at least two hundred different chemicals are used to treat crops for diseases and pests.

According to the National Research Council (1993),A commodity treated with or exposed to a pesticide theoretically can never totally be rid of all traces of residue. The chemicals get deposited in the underground water table and from their seep into the roots of plants, vegetables and crops grown on croplands and reach our homes through the market produce that we buy. The effects of these chemicals on the delicate biological systems of infants and children are a major area of medical research and investigation. Furthermore, growing the same kind of crops year after year results in the same kind of pest attack because the soil lacks the required diversity and complexity that helps keep these predators and insects and bay. Human activities have caused an imbalance in nature as man has tried to simplify a system that can stay alive only if there is present a certain level or degree of complexity. Nature has its own way of maintaining a balance. This is highly evident if we take into consideration the process of random pollination that is mainly responsible for the diversity of flora and botanical richness in the ecosystem. Chemicals must be used in a controlled way and newer methods of biological pest control must be considered to reduce further damage.

One big fear that the world is always faced with is what it would be if all the fossil fuel the it has been relying on are depleted. There is a continuously growing consumption of energy in all aspects of human life. The production processes all require enormous amounts of energy and they keep on growing each and very day. The consequences of these have been overexploitation of fossil fuel and which lead to great pollution of the environment.  The  from the statistics California institute of technology  indicate that since the year 1980 the major sources of energy on earth have been hydroelectric power , natural gas, coal , oil and other sources. Those that been have driving industries are the coal and oil. Out of these this sources, it is only hydroelectricity that is renewable but it is not sustainable. The reliance on oil, coal and gas has been consistently increasing in that by the year 1980 the total world oil energy consumption was just 140 quadrillion BTU, and cool and gas both 55 quadrillion BTU, but this has changed to 250 quadrillion BTU by the year 2000.

In attempt to mitigate this, many attempts are being made to come up with alternative energy sources. These energy sources should be renewable and sustainable. Many energy research organizations have always identified solar energy as the new frontier for energy production. This source is seen as being not only renewable and sustainable but also very environmentally friendly. The biggest challenge to the source has been how to tap it efficiently and cheaply. Even though there are already many methods that have been used for along time, they have not always achieved the level that can be productive enough. For example, there is the use of solar panels in various homes and some institutions but they are quite unreliable for any large-scale use. The world requires adequate energy to run the production plants in the manufacturing industries, enough energy to fuel up vehicles and for home consumption.

According to Caltech research, there has never been a time in history when fossil fuel consumption was highest as it has been in this century. This has made the global carbon levels to shift to very high concentrations. According to the research by the year 1800, the atmospheric carbon concentration was just 285 ppm but this has shifted to over 330 ppm by the year 2000 and continues to shoot. It openly shows how environmental pollution is high in this century and with it has come the threats of global warming.

Researchers have come up with various technologies that can help harness this abundant energy from the sun and use it productively. One of those technologies is the fuel cell technology by the researchers from the California institute of technology. These researchers, with the U.S. Department of Energys Lawrence

Berkeley National
Laboratory (Berkeley Lab) is now in the process of a major breakthrough towards artificial photosynthesis. They are quite hopeful about the properties of nano-sized crystals of cobalt oxide. They are banking on cobalt oxide that can effectively carry out the crucial photosynthetic reaction of splitting water molecules.

Artificial photosynthesis will not add up to the green house gases and hence global warming. This will be a renewable resource for transportation energy. The idea is to create an artificial leaf that can duplicate the few steps of photosynthesis. That leaf can capture the solar photons and have a catalytic system in place that can oxidize water.

Heinz Frei and Feng Jiao have published the findings of their study in the journal AngewandteChemie. This research was carried out with help of the Helios Solar Energy Research Center (Helios SERC), a scientific program at Berkeley Lab under the direction of Paul Alivisatos. They are concentrating on developing fuels from sunlight. Frei is the deputy director of Helios SERC. Heinz Frei, who is a chemist with Berkeley Labs Physical Biosciences Division, explains, Photo-oxidation of water molecules into oxygen, electrons and protons (hydrogen ions) is one of the two essential half reactions of an artificial photosynthesis system  it provides the electrons needed to reduce carbon dioxide to a fuel. He again emphasized why he is putting lots on effort into cobalt oxide, Effective photo oxidation requires a catalyst that is both efficient in its use of solar photons and fast enough to keep up with solar flux in order to avoid wasting those photons. Clusters of cobalt oxide nanocrystals are sufficiently efficient and fast, and are robust (last a long time) and abundant.

They perfectly fit the bill.
Fredi also explained why they are not very keen on using iridium oxide for artificial photosynthesis. He stated though iridium oxide is efficient and fast enough for light absorption and a good catalyst but this metal is least abundant metal on earth. Hence, it is not very practical to use it on commercial scale. He says, We needed a metal that was equally effective but far more abundant. First, they tried to take the manganese based organ metallic complexes for artificial photosynthesis, which plants use in Photo system II. However, manganese-containing compounds were water insoluble and not very robust. Fredi and his team paid attention to cobalt oxide, which is a highly abundant material and fit for commercial use. Cobalt oxide also dissolves in water. However, it was not a success story right from the beginning. The micron-sized particles of cobalt oxide were ineffective and slow to act as catalysts. Then Frei and Jiao turned to nano-sized cobalt oxide. The yield for clusters of cobalt oxide (Co3O4) nano-sized crystals was about 1,600 times higher than for micron-sized particles, said Frei. And the turnover frequency (speed) was about 1,140 oxygen molecules per second per cluster, which is commensurate with solar flux at ground level (approximately 1,000 Watts per square meter). The next big step, however, will be to integrate the water oxidation half reaction with the carbon dioxide reduction step in an artificial leaf type system.

This research showed that by 2050 the worlds total energy requirement would be more than 20TW.This technology would be the ultimate solution to this energy challenge. When one critically analyses all the energy sources available on earth you conclude that harnessing the solar power is the only promising sustainable energy source. We have other renewable sources like wind with only 2.4 TW extractable, ocean and tides has a total of only 2TW, geothermal at 12TW but only a small fraction is recoverable. Finally, there is hydroelectric with a total of 4.6TW but only 1.6 is technically feasible with 0.9 TW economically feasible and 0.6 already installed.

Others, which are nonrenewable like nuclear, fossil and biomass all, cannot amount to any sustainability. Not all these can compare to the solar energy, which is 120000TW on the earth and 600TW practically trappable according to the Caltech research.

The technology described though complex in context show is a promising future as far as renewable energy is concerned. The presenters are convincing in the manner of approach to their idea. They seem to fully understand their course of action. They     understand the resources needed that can help them achieve this mission. They portray exuding confidence in their work, which gives one hope that it would lead to a great breakthrough, and help alleviate this fear of global warming. In fact, with this technology one can change the ideoalogyn that has been running over the 19th century that we live in doomed earth.

This paper researches on the history of explosives over the past century, its types and usage.

A brief introduction of the explosives has been given. The research question or problem is that the explosives accessibility should be limited and restricted for public use because of its negative effects. The method used has been secondary research.

The explosives have been classified as high, low, primary and blasting agents. Disadvantages of the explosives are concerned with safety and health issues, storage, environmental considerations and misuse. Some other uses of explosives have also been mentioned in the paper such as aerospace, agriculture, art, demolition, excavation, destroying waste, metal hardening, shooting and welding.

Analysis has been made of the findings. Recommendations are also made that include proper recycling, handling, and regulated so there are no misuses of the explosives. Lastly, strict regulations and laws should be made in relation to the usage of different explosives.

With the recent increase in terrorism around the world, it would be quite interesting to know the history of explosives, their original purpose and their use today. Just the word explosives give a picture of warfare, bombings and killing of the innocent lives in short for destruction.

Explosives basically are made up of one or more combination of substances with the capability of exploding it self using its own energy. They are categorized by the energy stored unto them. Their power is obtained from oxygen, nitrogen and carbon. These chemical reaction take place as small material transforms into larger volume of heat and gas. The expanding heat and gas have the capability to smash buildings and large objects by exploding through heat, shock or electricity. (Akhavan, 2004)

Explosives of any kind solid, liquid or gas consists of fuel and oxidizer, which helps burn and supply oxygen for the fuel respectively. The burning and expansion of gases takes place in thousandths of a second. The expansion of gases results in vicious shockwave. The more there is the pressure of shockwave, the stronger the blast.

Combustion or fire takes place when oxygen gas joins with a substance. There are substances that do not explode by themselves but explode when there is oxygen near them. Example include gas, hydrogen, or alcohol. Although they are not explosives but they can set off when there is oxygen in the air.
The use of chemical explosives could be seen in the peacetime besides in the warfare such as rockets into space, mining projects, and fireworks. Although, explosives were built for various different reasons, they are misused today in harming the society as whole. It is true that several types of explosives developed over the years were used for military reasons, construction, mining and engineering companies and other industrial uses they should be restricted for any other use and to any persons who are not involved in the above purpose regardless how low the explosives are.

Methodology
The report is based on secondary research i.e. books and internet sources.

Results
The research conducted from the internet sources have helped study several classification of explosives, their history, many usages, and types of explosives used over the years.
           
There are different classifications of explosives
High explosives
Deflagratelow explosives
Primary explosives
Secondary explosives
Blasting agents
         
High explosives are detonated by the influence of shock. Within millionths of a second, explosions take place. Some of the examples of high explosives include TNT (Trinitrotoluene) or nitroglycerine, RDX and PETN (pentaerythrite tetranitrate). Those that start out by heat are known as primary explosives while the ones starting out by detonator are termed as secondary explosives. High explosives can be mixed with oil to form clay. They become plastic explosives that could take into different shapes to explode directly. Terrorists used this weapon during 1970s and 1980s. It can also be pressed into shape of thin layer to be but into an envelope. (Davis, n.d.)
           
Primary explosives are initiators detonate through heat, electricity and shocks. They explode from small explosive materials to large explosions. (Davis, n.d.)
           
Deflagrate or low explosives dont create much pressure but burn very quickly. It takes hardly thousandths of a second to burn all the way through from one end to the other. Low explosives include gun powder or black powder. Although they are low, they produce a solid reaction creating smoke in the air. They are also called propellant explosives. They have enough oxygen for their combustion that burns and not explode. Such explosives differ with the speed of which their energy is delivered. It depends on how powerful powder has been used. Fireworks are also considered as propellant explosives. (Davis, n.d.)
         
Blasting agents are used at construction sites, mining places etc. they are safe and less costly. A blasting agent called ANFO (Ammonium Nitrate and Fuel Oil) can cause serious destruction if thousands of pounds are used of it. Some fertilizers contain ANFO. Unfortunately it has been misused by the terrorists around the world because of its easy availability. (Davis, n.d.)

Brief history of explosives
The explosives started off in the 1650s dated back to the Chinese black powder being used for military reason was tailored for mining in England and Hungary. In 1847, a powerful explosive called Nitroglycerine was discovered by Italian chemist named Sobreo. Black powder was the only explosive available until Sobreros nitroglycerin, Bottgers and Schonbeins nitrocellulose was discovered. Black powder is made up of sulfur, charcoal and potassium nitrate. Because its capacity to generate heat and gas, it was popular for using as a propellant explosive in fireworks. Black powder also known as gun powder is low explosive as it decomposes at a slow rate.   Afterwards, the genius Alfred Nobel gave birth to dynamite by adding 25 Kieselguhr in the Nitroglycerine to ensure safer management. It was the era of dynamites around the world. (Akhavan, 2004)

Over the period of 100 years, there were modifications in the mixture of nitroglycerine with other substance like wood, Nitro Cellulose, Ammonium Nitrate (adding salt oxidants) and flammable products like TNT and BNT.

TNT was made by Wilbrand from Germany. Its manufacturing started in the year 1891. In 1902 it became a substitute of picric acid and was used as a standard explosive in the Great War. It can transfer from solid to gas quite rapidly. It holds carbon, nitrogen and oxygen in it self. TNT does not explode impulsively. It has to be detonated by another pressure force to initiate the explosion.

Nitroglycerine has been used for the manufacturing of dynamites and other explosives since 1850s. It has been used for military, construction and demolition purposes. In the cold weather, nitroglycerine used to be replaced by nitro glycol. Moreover, it serves as a vasodilator for curing heard diseases. A main component of AFNO Ammonium Nitrate has been used as an oxidizing agent for explosives.  Ammonium Nitrate was one of the major developments of the all which had greater capability to detonate which became popular after disasters like the one in Texas City in 1947. (Akhavan, 2004)

In the 1960s came the ANFO and water Gels. ANFO captured a significant fraction of explosive dynamite market. AFNO explosive also serves the purpose of peacetime uses. It can result into devastating explosions but still considered slower to detonate than TNT. TNT has high velocity and is more expensive than the AFNO but AFNO is  times powerful than TNT. Because of they were not regulated as the TNT and dynamites, they were taken by the terrorists to be used in making bombs. Some of the bombings took place in New York in the year 1993 and 1995 in Oklahoma City using these explosives. (Akhavan, 2004)
Other explosives developed were known as slurries or water gels. They were made of Ammonium Nitrate solutions and sensitized gels by using TNT or black powder. There usage was limited to the construction and boreholes.

Then there was the development of nuclear explosives. A nuclear device reacts from the ignition of fission and fusion. They are so destructive that can blast the whole city. They are known to be weapons of mass destruction. Their usage has become a debut of international relations policy. There are two types of nuclear weapons

Atomic bombs- they produce their energy from nuclear fission.

Hydrogen bombs- they produce their energy through nuclear fusion.

The atomic age started in the WWII when the US bombed on Hiroshima and Nagasaki. The world knows the results of these bombing and the death tolls that justifies abandoning of these explosives.

Disadvantages
Safety and Health- safety is big issue against using these explosives. The blast from a nuclear explosion could destroy the whole city. Moreover, the radiation in the air remains for a longer period of time even after the heat waves have finished causing long term sickness for the survivors. Thus even in the warfare, this explosive should be restricted.

The four main effects of the blast on a human body are

Overpressureshock- this causes an increased pressure damaging internal organs of the human body that may lead to permanent injury or death.

Fragmentation- this includes the debris, and harming the vegetation around the place of blast. It is usually done for mining.

Impact and Heat- the impact of overpressure waves on a human body induces aggressive levels of blast acceleration. This results in injuries that may also become unbearable. Declaration injuries may also take place by being impacted directly against the surface. Explosive fireball may also act as combustible driving force into the body.

Storage-Explosives tend to be expensive to acquire and maintain. There are obstacles as explosives fall into unofficial hands causing problems.

Environmental considerations there are some explosive substances like hydrogen that may cause less oxygenic environment (inhalation risk). Individuals may come across sickness, headache, unconsciousness, and depression and so on. Even death may occur under certain circumstances in the case of hydrogen overexposure. Other explosives that we consider as peacetime like fireworks may cause problems for animals with their loud noise. The toxins used in these substances can cause inhaling problems, ingestion and skin disease. Although they do not pose as such negative effects but improper handling may cause poisoning or bone marrow.

When explosives are used for mining coal, it may destroy vegetation, soil, wildlife, and air quality.
Misuse- explosives that are not fully regulated get misused as they have had over the past years in terrorist activities. Criminal and illegal use of them has become a threat everywhere around the globe now. Explosives are the means through which terrorists win their aims and targets.

Analysis
From the research above, it justifies the fact that explosives should only be used for engineering, construction, space shuttles and research purposes keeping the health and safety of all the living things around them.

It is true that over the years there have been geniuses who have developed so much to make life easier but unfortunately its mishandling can cause serious hazards for the people, their property and the environment it self. Precautionary measures should be taken while using these explosives should be kept in mind.

We should also learn from the history of using nuclear explosives and how disastrous the outcome was and that it would always produce the same result if ever used again. Although there have been treaties over not using these weapons, there still exists wars due to those in possession with.

Lastly, the problem of terrorism is quite linked with explosive materials being used by them. There shouldnt be any accessibility to the public of such disastrous monsters that could eat away peoples lives. Terrorism is a global threat which has not been encountered or overcome and may take years to end it.

Other uses of explosives
It would be quite interesting to know that explosives are also used for the following
Aerospace- boosting rockets
Agriculture- used by farmers to demolish boulders or tree stubs
Art- for craving the mountains
Blasting of coal
Logging
Demolition- building, towers, bridges etc
Manufacturing of diamonds- grinding and polishing of jewelry
Excavation- clearing underwater channels
Destroying hazardous waste
Security systems
Medical uses
Metal hardening- this includes railways or railroads
Driving pile- dynamites help explode piles
Shooting in sports
Welding
Recommendations

Explosives that contain toxic substances like sulfur or nitrates must be properly disposed to avoid pollution of the air, land and water.

Explosives that are used at the constructions sites must be used and handled carefully to avoid any injuries or mishaps.

Explosives that are dangerous to the environment should be kept to minimum use.

Terrorists should be prevented from acquiring any sort of chemical explosives.

There should be license for using such explosives as it cannot be determined whether the person may perform a terrorist act with it.

Cleaner explosives should be built that generate less radio active waves.

Strict rules and regulations should be made regarding the usage of each type of explosives ranging from high to low.

Injuries at the construction sites can be prevented if the workers wear proper protection suits to survive any blasts or unpleasant event.

Conclusion
Explosives are tend to be used for various purposes and yet justifiable purposes by the businesses. However, explosives that are hazardous to the environment and the people should not be used. Regardless of the benefits explosives gives its misuse can cause serious damage to the world. Thus they should be carefully regulated and monitored. This probably may help encounter the biggest threat of terrorism.
Besides the above reason it should not be forgotten that many explosives being used may affect the health of the people. Thus safety of the public should be the main focus. Similarly animal life should also be protected by not using explosives that may disrupt wildlife. In the end we must aim for cleaner environment that is free from contaminated soil, water or land.

Polychlorinated biphenyls also known as PCBs belong to a group of 209 synthetic organic chemicals composed of between 1 and 10 atoms of chlorine attached to biphenyl rings (1). These individual chlorinated biphenyl rings, congeners, were mainly manufactured as mixtures comprising of 60-90 congeners. The PCBs have a general formula of C12H10-xClx (1). PCBs are sparingly soluble in water but highly soluble in oils, fats and organic solvents. They are stable compounds and not easily degradable although some thermal, biochemical and chemical factors can degrade PCBs through spontaneous (metabolically) or intentional (incineration) processes (1). Degradation of PCBs by heat requires enormous application of heat energy and metabolic degradation proceeds slowly as compared to other compounds. The once highly controversial PCBs were produced as complex isomers with varying numbers of chlorine atoms. They were manufactured and sold with a 4 digit number attached to their trade names where the first two numbers referred to the carbon atoms attached to the biphenyl rings and the other two numbers referred to the chlorine percentage by mass in the PCBs mixture (1). For instance, Aroclor 1260 contained 12 atoms of carbon attached to the biphenyl rings and had 60 percent chlorine in its total mass (1). The commercial applications of PCBs were mainly made possible by their physical and chemical stability such as thermal and chemical resistance which attracted uses such as electrical insulation and as lubricants. Because of these properties and the poor understanding of their toxicity levels, PCBs may make a come-back although they were banned due to environmental contamination.  However, this calls for detailed studies that will disapprove the existing studies of PCBs on the harmful health hazards caused by the compounds.

History, Properties and Uses of PCBs The PCBs are classes of chemical compounds that never existed naturally but were slowly released into the environment beginning 1900s by industrial processes and human activities (1). In 1929, Monsanto became the only American company to first manufacture PCBs which made a breakthrough in industrial chemistry. PCBs were highly celebrated for their properties of preventing explosions and fires and the fire code made PCBs a requirement for fire prevention (1). The PCBs oils have low reactivity, are inflammable, have high resistance to electricity, are excellent insulators and are subtle even when exposed to pressure and heat. These properties made PCBs oils to be used as insulators for capacitors and transformers and dielectric fluids. The oils slowly gained applications in hydraulic fluids, systems for heat transfer, casting wax, adhesives, pigments, plasticizers, compressors, fluorescent light ballasts and much more (1). The PCBs application declined in 1970s and then completely stopped in 1977 due to environmental and health concerns (1).Health Effects of PCBsPCBs as Carcinogens A number of studies have also shown PCBs to be associated with cancer of the biliary tract and that of the liver. From animal studies, rats that feed on PCBs have a higher propensity of developing hepatomas or liver cancers. This may bring into a conclusion that PCBs are likely to be carcinogenic compounds among humans. The Environmental Protection Agency (EPA) and the International Agency for Research on Cancer (IARC) have classified PCBs as potential human carcinogens and some studies under the National Toxicology Program have already concluded that PCBs can cause human cancer (1). The National Institute for Occupational Safety and Health has classified PCBs as possible occupational carcinogenic compounds. Among the studies on exposed workers have shown some changes in urine and blood and this are indicators to liver damage.

The most affected population consists of the mothers and children who are exposed to PCBs. Metabolism of these compounds in the liver is slow and often leads to hydroxyl conjugates which are highly poisonous and have a potential to cause hepatomas (1). A number of melanomas have also been observed apart from hepatomas. PCBs exposure causes skin cancers perhaps due to the interference with melanocytes that produce melanin. Melanin is essential for the protection of humans against ultraviolet rays from the sun. Absence of melanin paves way for destructive effect of UV rays on the deoxyribonucleic acid (DNA) which eventually leads to a number of mutations (1). Consumption of fish contaminated with PCBs lead to the development of biliary tract cancer, cancer of the gall bladder and cancers of the gastrointestinal (GIT) cancers. The main entry of PCBs into the human system is through the GIT where humans consume heavily PCBs contaminated fish. The PCBs get into the system and circulate in the entire body. The PCBs eventually reach their destiny in the fat tissues where they are periodically released to cause detrimental health effects. While there is blood-brain barrier, the PCBs can get into the brain and cause brain cancer (1).

Women exposed to PCBs sometimes develop breast cancer. The mechanism for the development of breast cancer can be thought to be that of activation of protooncogenes to oncogenes. Protooncogenes consist of class of human genes that have the property to cause cancer but upon activation. The protooncogenes are usually activated to oncogenes by a number of factors which include chemical and viral activation factors. PCBs, particularly the metabolites such as hydroxyl PCBs have a potential to activate protooncogenes and oncogenes (1).Non-Carcinogenic Effects of PCBs on Human Health Large amount exposure to PCBs has been observed to cause various skin conditions like rashes and chloacne. Animal experiments have shown that PCBs cause skin conditions presented as acne. PCBs have also been found to cause anemia, thyroid, stomach, and liver damages in animal experiments.  The changes in behavior, reduced immune defense and impaired reproduction observed in animal studies show the potentiality of PCBs of causing devastating effects in humans. While these effects have been observed, PCBs have not shown to cause any birth effects. The compounds are not therefore classified as teratogenic despite the heated controversy surrounding the topic of PCBs (1).

PCBs cause women to give birth to babies with reduced weights. Women that heavily feed on PCBs contaminated fish have babies with reduced weights than the ones who do not feed on PCBs contaminated fish. There are also abnormal infant behavior responses to tests. The behaviors include greatly declined short-term memory and motor skills problems which last for a number of years. The children often have a lowered IQ than those born of mothers not exposed to PCBs (1).

There may be also some problems of developing skills in visual recognition and general learning. Among other effects to babies born of mothers exposed to heavy PCBs concentration include deranged immune system and various effects to the thyroid functions. Perhaps one of the ways through which children get exposed to PCBs toxicity is through breastfeeding. However, placental PCBs transfers are also not unusual as the mother can pass the PCBs to the fetus during early stages of development in the mothers womb. This affects their immune function. The PCBs just like dioxin binds to essential immune receptors and influence the working of the T cells and the lymphocytes. There has been an increasing association of Epstein-Barr virus infection with increased PCBs exposures (1). In addition, since the immune system is weakened, there are higher chances of individuals developing non-Hodgkins lymphoma. Animal experiments show an increased risk of PCBs exposed animals to get infected with Epstein Barr virus. This similar effect is seen among individuals exposed to dioxins and dibenzofurans (1).

PCBs also affect the levels of estrogen thus contributing to the overall problems of reproduction. There are high chances of males being feminized in the womb of mothers. In some cases, the babies turn out to be intersex meaning that they are neither nither males nor females. The babies born of mothers with PCBs contamination also have chances of developing both the female and male reproductive organs. While the two organs may develop, neither the penis nor the vagina will be fully functional there may be some aberrations in the normal functioning of the reproductive system. This observation has mainly been made in whales and polar bears exposed to PCBs. These animals that are exposed to PCBs develop both the female and the male reproductive organs and they do not usually reproduce. This condition is known as the endocrine disruption and therefore PCBs are referred to as endocrine disrupting chemicals (EDCs) (1).

Other non-cancer effects of PCBs such as the ocular and dermal effects have also been documented among monkeys as well as humans subjects. Liver toxicity among rodents has also been documented. There have also been studies to evaluate serum cholesterol, serum triglyceride and blood pressure and linked to the increased levels of serum PCBs among human subjects (1).Environmental Effects of PCBs

PCBs do not degrade easily and therefore remain in the environment for a long time. They continue to be maintained in air, soil and water constantly exposing humans to devastating health risks .The higher the chlorination of biphenyls, the more they are resistant to degradation. Unfortunately, the qualities that make PCBs much valued are the same qualities that make the PCBs to be environmental unfriendly the chemical and thermal stability. The compounds therefore increasingly build up in the environment as more PCBs are introduced. The PCBs increasingly got released into the environment prior to their ban in 1977 through releases and leaks mainly from PCBs containing electrical transformers(1). It is also suggested that PCBs got released through industrial incinerators and the burning of municipal waste. The PCBs enter the human food chain hence leading to harmful health hazards. Organic matter which is contaminated with the PCBs is consumed by worms. The same organic matter provides for nutrients for plant growth. These worms are then eaten by small fishes which are eaten by larger fishes. These small larger fishes are eaten by humans. The eagles also feed on the large fish and since the eagles have a longer lifespan, they continue to feed on the larger fish that fed on small fishes which were heavily contaminated with PCBs from worms. This eventually leads to the concentration of PCBs in the fatty tissues of eagles in a process known as bioaccumulation. Similarly, as humans continue to feed on the contaminated fish, bioaccumulation of PCBs in the fatty tissues also increases and the health consequences are always devastating (1).

A common historical case of PCBs contamination occurred in Hudson River where PCBs were dumped by the General Electric Company between 1946 and 1977(1). The chemicals entered the human food chain through humans consuming fish that fed on contaminated zooplanktons and phytoplanktons. While some of these chemicals may be biotransformed into non-toxic metabolites, most congeners of PCBs take long to be metabolized hence get retained in fat tissues.Conclusion

The controversial PCBs still hold significant debate among health and environmental protection activists since their ban in 1977. Their potential physical and chemical properties that attract an array of uses continue to make chemists to start thinking of reusing the PCBs. However, for these compounds to be reintroduced, efforts have to be made to make them less toxic. Structural chemists and pharmacologists have a challenge to come up with compounds of PCBs that are not toxic to humans. Conjugation of some groups or moieties can help reduce toxicity levels of PCBs. It is hoped that the successful transformation of these compounds will lead to the reintroduction of the PCBs in uses such as the use in capacitors and transformers, voltage regulators, electromagnets, carbonless carbon paper and oil-based paints. Meanwhile intensive public education should be provided to the members of the public and educate them on the dangers of polluting the environment. The health hazards such as cancer, immunotoxicity, neurotoxicity and developmental problems should be communicated in a clear way. Knowledge on environmental protection seems critical in preventing such problems that were caused by deliberate dumping of PCBs by the General Electric Company between the years 1946 to 1977.

A majority of substances used by humans in daily life such as air, water and food contain thousands of unknown substances. Other organisms also present in the environment such as insects, animals and microorganisms may be harmful to humans and can result in serious health effects on human beings. The following paper will examine health risks in relation to pesticides, chemical contaminants and natural toxins.

Their history, mode of manufacture, safety and toxicity, relevance and importance based on their current uses and their relation to laws and legislative issues will also be discussed. Finally, measures taken to prevent harm and poisoning due to these substances will be looked at and future needs and concerns analyzed

Introduction
Most harmful organisms are normally present in the form of pests and include house flies, mosquitoes, weevils, locusts and disease  pathogens such as bacteria, viruses and fungi .some of these transmit disease vectors directly to humans while others attack foodstuff like vegetables and fruits which if ingested lead to health problems. Some foods have natural toxins which enable them to resist these insects. They include potatoes which contain a toxic component known as solanine among other glycoalkaloids that usually occur at low level (NZFSA, 2010).

As a result, when these foods are wrongly handled they can in turn cause food poisoning. Pesticides, which are also developed to destroy certain harmful insects and prevent diseases, can be harmful to human beings when they are exposed to certain levels as they are mostly sprayed. On the other hand, chemical contaminants may be chemicals related to cooking and heating procedures and include acrylamide (Health Canada, 2010) .

Pesticides are designed in a toxic manner to certain forms of life and are widely used in the environment as a control against pests. However, huge public concern is developing in relation to their use as they can pose serious health problems. This is due to contamination of drinking water in both agricultural and urban regions. The residues are also found in almost all places including offices, homes, on food and in the air. This necessitates the continuous monitoring to protect human populations from this problem (Levine, 2007)
Among the various forms of pesticides are the chlorinated hydrocarbons (Levine, 2007). An example of these forms is dichlorodiphenyltrichloroethane or DDT. The IUPAC name for this chemical which has a molecular formula of C14H9Cl5 is 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane. The molecular structure of DDT is as shown in Figure 1.

Although it is not a very chemically reactive chemical, it is normally involved in one important dehydrochlorination chemical reaction to form 2,2-bis(p-chlorophenyl)-1,1-dichloroethene or p,p-DDE. This occurs in the presence of KOH, NAOH, and other strong alkalis.(National Research Council  US, 1952) as shown
(C6H4Cl)2 CHCCl3  OH-  (C6H4Cl)2CCCl2  Cl-  H2O.

The chlorine produced from this reaction is measurable, aqueous and depleted isotopically, and is therefore usefully used as a tracer of these reactions in environments with fresh water (National Research Council US, 1952).

On the other hand natural toxins occur naturally in food and in some plants which have the ability to produce toxic compounds if ingested by humans under certain conditions such as when raw or when improperly prepared or cooked (Health Canada, 2010). Some of the naturally occurring toxins include ipomeamarone, furocoumarins, lectins, oxalic acid, cucurbitacins,cyanogenic glycosides, and toxic honey (NZFSA, 2010) Some of these natural toxins can however at times be man made.

Another major health risk can be posed by food-borne chemical contaminants which can either be organic, inorganic or radioactive (Artiola, Pepper  Brusseau, 2004). These chemical contaminants become pollutants only when their levels accumulate sufficiently to cause negative environmental and health effects. They include Acrylamide, industrial chemicals such as dioxins, furan, radionuclides and melamine (FDA, 2009). Most sources of fish also contain these chemical contaminants like mercury posing serious effects if eaten.

Production and the Adverse Effects on Humans
Pesticides can get into ground water and hence contaminating drinking water in different sources. Their negative health effects are experienced by all people but are majorly found among children, pregnant women, farmers and farm workers, and the elderly (Levine, 2007 p.1). They include acute poisoning, cancer, damage to the neurological system, birth defects and harm associated to reproduction and development. In addition, the normal responsiveness of a persons immune system has been found to be suppressed resulting to vulnerability of the body to invading pathogens such as viruses, bacteria, parasites and tumors. Moreover, the exposure to pesticides has revealed a decrease in sperm counts (Levine, 2007).

Some of the foods that may contain natural toxins include fruit seeds and pits like apple and pears seeds and Kernel of apricots and peach contain naturally occurring substance called amygdalin which can turn into hydrogen cyanide in the stomach causing discomfort or sickness. Other examples include kumara, potatoes, kidney beans, zucchini, toxic honey and rhubarb (NZFSA, 2010).

Although the degree of reactions and symptoms experienced depend on an individuals sensitivity to a toxin and the amount of concentrations, natural toxins present general side effects. These include vomiting, stomach cramps, diarrhea, collapse, muscle twitching, cramps, decreased breathing and heart action, pain, headache, convulsions and coma and at times they cause a painful skin reaction when ultra-violet rays of the sun are combined in the contact with the parsnip plant. In worse situations they can even lead to death (NZFSA, 2010).

Before the advent of synthetic pesticides was introduced in the nineteenth century with the use of sulphur compounds as fungicides, naturally occurring substances such as pyrethrum were being used by farmers. Arsenic compounds were later developed to control insects which attacked fruits like apples and grapes and vegetables. For instance, DDT was first synthesized by Othmar Zeidler in 1874 (WHO, 1979). However, its properties were only discovered in 1948 by Paul Hermann Muller, a Swiss scientist who won a nobel price award for his efforts in physiology of medicine (Nobelprice.org, 2010).

As there was a short supply of pyrethrum at that time, DDT became widely used in Europe during the Second World War to control insect vectors that caused typhus and also as weapons of war. As a result, it almost wiped the disease out completely.  With additional impressive effects, it was also used in the South pacific for malaria control where it was aerially sprayed to kill the mosquitoes. The use of pesticides also ensured increased agricultural production because they decreased the number of insects which were a natural threat to crops (Levine, 2007).

Whereas natural toxins were discovered by Homo sapiens in ancient times and were used in hunting as arrow poison, they are still currently put to use in hunting and for ethnic wars in Asia, Africa and South America. They are also used as molecular markers in studies of designing functional membrane and structures of cells due to their high efficiency and selective effect they are used as molecular (Gelashvili, 2002).

The manufacturing process of pesticides involves the manufacture of major compounds such as carbamates and dithiocarbamates, chlorophenol compounds, organochlorines, and miscellenious compounds like biopesticides and pyrethroids. It goes through the main processes of preparing process intermediaries, functional groups introduction, coupling and esterification, processes that involve separation and final product purification. Emissions of substances in the air such as volatile organic compounds and particulate matter, liquid effluents that contain pesticide residues and toxic organics as a result of equipment cleaning after operations and solid wastes are generated from each of these steps (World Bank Group, 1998).

Natural toxins are therefore natural chemicals that occur in food which include carbohydrates, protein, sugar and vitamins essential for growth and health. However, when they are contained in some foods they become possibly harmful. At times, certain climatic conditions favor growth of toxic producing fungi on food crops. Furthermore there can also be bacterial toxins as well as those produced by algae and molds (Phelps  McKillip, 2002).

Chemical contaminants can be environment related where the chemicals manufactured for industrial use break down easily due to their stability hence can enter the food chain when released (Williams  Hammit, 2001). Others although they occur naturally, their mobility is increased by industrial activities making their entry levels in food chains higher than usual. Some contaminations are induced by food processing as a result of reactions between naturally occurring food components or the intentional use of food additives which react with another compound (Health Canada, 2010).

Current Uses
Besides the control of malaria among other diseases spread by insects, pesticides can also be used for agricultural activities (Levine, 2007). Currently, the types of pesticides in use are grouped into three. They include insecticides, which are meant to eliminate destructive insects. These can be sprayed directly or used to dose a particular area. There are also herbicides or weed- killers, which like insecticides, can be selective for particular kinds of unwanted plant. Fungicides on the other hand are used for moulds, rots and several plant diseases. They must be sprayed widely since they have to come to direct contact with the fungus.
On the contrary, is not yet clear why the natural toxins occur in some plants. The presence of natural toxins in some plants, however, act as natural pesticides to prevent the attack by insects, as a reaction when the plant has been stressed by micro-organisms, and damaged such as in bruising, and also as response to injury.

They are additionally available to prevent the plant from spoilage when damaged by weather. Toxins may also be produced to protect the plant from ultra-violet light, handling or microbes (NZFSA, 2010).
Additionally, agricultural chemicals are used for increase of crop yields, weeds and pest controls and prevention of crop and livestock diseases and can also be classified as chemical contaminants. These include pesticides, herbicides, regulators of plant growth, growth hormones and veterinary drugs or antibiotics (Dionex Corporation, 2010).

Legislative Issues for Prevention and Control against Harm by Toxic Substances
There is however some hope since there are ways to reduce pesticide use and exposure (Levine, 2007), because a lot of emphasis has currently been laid on microbial safety and food defense with regards to the food industry (DeVries, 2006). Various laws and regulations such as environmental law, water quality regulation, and pesticide regulation among others have been set up to provide guidance on how people should handle wastes, food and other substances with regards to safety (Levine, 2007) . Agencies such as the UK Food Standards Agency give recommendations on the specific amount of food substances to be included in a dietary intake for example not more than two apricot kernels daily (NZFSA, 2010). They also provide guidelines on how to prepare and cook various foods that contain toxic substances
In order to prevent such bodily harm to consumers, food producers should test plants and animals for chemical residues. The introduction or delivery of food into consumer markets and global trade in general is also regulated by bodies such as the Federal Food, Drug and Cosmetic Act (FFDCA). This ensures that those purchased and consumed do not contain any poisonous or dangerous substances like chemical contaminants which may be harmful to human health hence overseeing food safety. As a result natural toxins such as mycotoxins, pesticides, industrial chemical which include dioxins are assessed and potential exposure and risk eliminated (FDA, 2009).

Research is also conducted by health scientists to assess and understand effects of certain chemicals on the human body. As in the case of chemical contaminants, there are set regulations concerning the annual or lifetime rates of application for pollutants such as heavy metals which are sometimes used as plant or animal micronutrients. There are also restrictions as to the maximum amount of organic pollutants in biosolids such as pesticides allowed for use (Artiola, Pepper  Brusseau, 2004).

Efforts should also be made for replacement of highly toxic and persistent pesticides ingredients with those that are degradable and less toxic. To prevent pollution some of the recommendations are use of high pressure hoses to clean equipment and reduce waste water, the reuse of processes by products as raw materials or substitutes for raw materials in other processes and the appropriate use of nitrogen blanketing on pumps, storage tanks and other equipment to reduce the amount of toxic organics released (World Bank Group, 1998). Consequently, due to presence of food toxins, a number of products have been recalled, alerts provided on public health and trade issues have occurred (DeVries, 2006)

Conclusion
In general, due to the detrimental effects of toxins, strict measures should be taken to avoid diseases caused by such toxic materials. Food should be well prepared and properly cooked to prevent poisoning from natural toxins. Good manufacturing practices should also be implemented to destroy natural toxins. In addition, manufacturing companies that deal with the production of such material and pesticides should minimize the amount of toxic waste products released or treat them to remove toxicity. Agricultural chemicals and wastes from factories should be correctly handled to prevent them from getting into water sources or accumulate to dangerous levels in the soil.

More specific laws and regulations should be established and strictly adhered to so as to ensure the safety of consumables. In addition, before the toxicity of a new substance is established, it should be held back till the necessary research is completed and it is found to be harmless. If such steps are taken, it will help in elimination of risks associated with these and many more substances.