The use of metals has bought many benefits to human civilization. However, some uses of metals have been bad for people and our environment. Metals have been used to make weapons that have claimed many lives. As we use more and more metals, some of them find their way into the air we breathe and the water we drink, thus poisoning us. In this section, we explore the dark side of how metals have been and continue to be used.
Metals in Warfare
The stone weapons of our cave-dwelling ancestors protected them from predatory animals, but had their own limits. They could not be too long or too thin without becoming too brittle, and were often more likely to break than to hurt the opponent seriously. The ductility of metals proved to be exactly what people were looking for, and daggers and swords showed up among the early uses of metals. The first metal used for this purpose, copper, turned out to be not hard enough. Around 3500 BC, some groups in the Middle East created bronze, a copper alloy, and made weapons with it. Bronze weapons such as axes and spears soon became popular for the strength and penetrating power. Another new idea was to put a metal tip on arrows fired from bows. Metal-tipped arrows had a huge impact on the outcomes of battles. For the first time, warriors had a long-range weapon with lethal capability. As metal weapons became common, the need arose for protective gear to protect against these weapons. Metal helmets, shields and armor provided some protection against metal weapons.
Some of the weapons made from metal were:
Mace - A mace is a simple weapon that consists of a strong, heavy shaft made either of metal or of wood reinforced with metal, and a head made of stone, copper, bronze, iron or steel. Maces were used heavily in early wars and were among the first weapons to ever be developed.
Dagger – Daggers are good for stabbing and cutting the opponent. Until the Bronze Age in the third millenium BC, daggers were made of flint, ivory or bone. Once bronze was discovered, it found ready use in making daggers, which were commonly used as murder
Sword – The sword is a long, sharp weapon developed from the dagger. Swords became common during the Iron Age due to the abundance of raw materials. During the Iron Age, blades of swords were made of iron, which became increasingly common due to the abundance of raw materials. Once people learnt to make steel, and some of most advanced steelmaking techniques were aimed at building better blades for swords.
Handgun – A handgun is a firearm made of zinc, iron or steel, designed to be held and operated by one hand, with the other hand optionally supporting the shooting hand.
Rifle - A rifle is a firearm designed to be fired from the shoulder. It is usually made of iron, steel, or aluminum alloys.
The mushroom cloud from the atomic bomb dropped on Nagasaki, Japan, in 1945, rose to some 11 miles above the spot where the bomb fell.
Shotgun – A shotgun is a firearm, which, like the rifle, is designed to be fired from the shoulder. The bullets or pellets, also called "shot", are made of lead, steel, or tungsten alloys. The material used to make the shotgun often has a density close that of the lead shot.
Cannon - A cannon is a type of artillery, usually large and tubular, that uses gunpowder or another explosive to launch a heavy ball over a long distance. Iron bars and pipes are welded together to make cannons.
Nuclear Weapons – The most dangerous weapons made by man, nuclear weapons (or "atom bombs") get their power from nuclear reactions in radioactive metals such uranium and plutonium. Even a small nuclear weapon can destroy vast areas through the blast, extreme heat, and nuclear radiation. Unlike ordinary bombs, an atomic blast makes the environment unsuitable for life for months and years after the explosion itself.
Environmental and Health Effects of Metals:
With so much metal being used, it is no surprise that some of them end up on our environment, in the air we breathe and the water we drink. The three metals responsible for the most pollution are lead, cadmium and mercury. In addition to these, chromium, copper and nickel can also pose risks to our health. It is good to remember that most metals are toxic to humans at high doses, even those that are needed in trace amounts for the body to function properly.
Lead can do our bodies quite a bit of harm, and the actual damage increases with the dose and time of exposure. Unborn children in their mothers' wombs, and infants, are more at risk than adults. Poisoning by lead makes it difficult for the body to produce haemoglobin, and damages the joints, the kidneys, and the digestive, nervous, and reproductive systems of the body. On average, adults in the UK consume about 1.6µg (1 µg is a millionth of a gram) of lead from the air, 20µg from drinking water and 28µg from food. This is within the tolerable limits specified by the UN Food and Agriculture Organisation and the World Health Organisation. People in emerging countries such as India and China are less fortunate, and may be exposed to far higher levels of lead in their air, water, and food. Though most people take in most of their lead from food, water carried by lead piping, air near a source of lead emissions, or dust and paint flakes in old houses can also expose people to lead. In addition, lead in the air contributes to lead in food by depositing lead-bearing rain and dust on crops and the soil they grow on.
The atomic bomb dropped on Hiroshima on August 6, 1945 was codenamed "Little Boy", and contained 64 kilograms of uranium.
Cadmium is chemically similar to zinc, so it can attach itself to the cells in the body that contain or process zinc. Once it enters the body, cadmium can persist in the body for decades before it is completely excreted. Cadmium can cause lung cancer, while exposure to the metal for a long period of time can damage the kidneys. Cadmium can also cause bone defects like osteomalacia (soft bones) and osteoporosis (weak bones). Under normal conditions, humans take in about 0.15µg of cadmium from air and 1µg from water. Cigarette smoke contains cadmium, and smoking twenty cigarettes deposit about 2-4µg of cadmium into the body. More than 7µg per week causes the body harm.
Mercury is a toxic substance that has no known function in the body. Mercury poisoning can cause many health problems like tremors, gingivitis (gum disease), and psychological changes. Mercury compounds can damage the brain and the nervous system, especially in unborn babies and infants. Pregnant mothers exposed to mercury can have abortions, or the children might have birth defects and developmental problems.
Minamata Syndrome: In 1952, in Minamata Bay, Japan, fish polluted with mercury poisoned people who ate them, killing over 500 people.
Chromium is commonly used in alloys and pigments. Contact with chromium can cause skin irritation and ulcers. Long-term exposure damages the kidney, the liver, and circulatory and nerve tissue. As chromium compounds often accumulate in water bodies such as lakes and ponds, we must be careful about eating fish who might have been victims of chromium poisoning.
Copper is one of those metals that is essential in small quantities for our bodies, but turns harmful in high doses. Copper poisoning causes diseases like anaemia and damage to the liver and kidneys. Excess copper also irritates the stomach and intestines. In an inherited disease called Wilson’s disease, copper is not excreted from the body, and the accumulation of copper causes brain and liver damage.
The human body requires small amounts of nickel for the production of red blood cells. When the body is exposed to high levels of nickel over a long period of time, the metal poses a threat to human health. Excessive exposure to nickel causes a decrease in body weight, damage to the heart and liver, and skin irritation.
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