Arsenic Is A Metalloid Biology Essay

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During the Bronze Age, arsenic was often included in bronze, which made the alloy harder. Albertus Magnus Albert the Great, 1193-1280 is believed to have been the first to isolate the element from a compound in 1250, by heating soap together with arsenic trisulfide. In 1649, Johann Schroder published two ways of preparing arsenic. In the Victorian era, arsenic (white arsenic or arsenic trioxide) was mixed with vinegar and chalk and eaten by women to improve the complexion of their faces, making their skin paler to show they did not work in the fields. Arsenic was also rubbed into the faces and arms of women to improve their complexion.

The 1858 Bradford sweet poisoning involved the accidental poisoning of more than 200 people. Twenty people died and over 200 became seriously ill when sweets accidentally made with arsenic were sold from a market stall in Bradford.

In the 17th and 18th century sugar plantations in the West Indies supplied Britain with sugar, and trading ports such as Bristol grew rich on the trade.

By 1750, there were 120 sugar refineries operating in Britain but these could only produce 30,000 tons of sugar per year, so prices were very high. Vast profits were made in the sugar trade, to the extent that sugar was called "white gold". The government recognised this and taxed it highly. As the price of sugar was so exorbitant, it was often mixed with cheaper substances or 'daft' and then this inferior sugar would be sold on to the working classes. Daft was a mixture of substances such as powdered limestone and plaster of Paris, not tasty but perfectly safe.

William Hardaker sold sweets from a stall in the Green Market in central Bradford. As was common practice at the time, his supplier and maker of the sweets - in this case peppermint humbugs - used daft in his sweet production, supplied by a druggist in Shipley. Tragically on this occasion, due to a mistake at the pharmacy, 12 pounds of arsenic trioxide were purchased instead of the harmless daft. Both daft and arsenic trioxide are white powders; the arsenic trioxide was not properly labeled and stored alongside the daft, and so the confusion arose.

The mistake was not discovered during the manufacture of the sweets, even though the finished product did look a little unusual. The sweets were made by James Appleton, who combined forty pounds of sugar, twelve pounds of arsenic trioxide, four pounds of gum, and peppermint oil, to create at least forty pounds of peppermint humbugs, meaning the sweets contained enough arsenic to kill two people per humbug.

Hardaker went on to sell the sweets from his market stall that night. Of those who purchased and ate the sweets, around 20 people died, with a further 200 or so becoming severely ill with arsenic poisoning within a day or so.

The Bradford poison scandal led to new legislation in order to protect the public from any similar tragedy. The 1860 Adulteration of Food and Drink Bill changed the manner by which ingredients could be used, mixed and combined.  The UK Pharmacy Act of 1868 introduced more stringent regulations regarding the handling and selling of named poisons and medicines by druggists and pharmacists.

Arsenic is still added to animal food, in particular in the US as a method of disease prevention and growth stimulation. One example is roxarsone, which is used as a broiler starter by about 70% of the broiler growers since 1995. The Poison-Free Poultry Act of 2009 proposes to ban the use of roxarsone in industrial swine and poultry production.

Arsenic was also used in various agricultural insecticides, and pesticides. For example, lead hydrogen arsenate was a common insecticide on fruit trees, but contact with the compound sometimes resulted in brain damage among those working the sprayers. In the second half of the 20th century, monosodium methyl arsenate (MSMA) and disodium methyl arsenate (DSMA) - less toxic organic forms of arsenic - have replaced lead arsenate in agriculture. It was used extensively as a rat poison due to its deadly effect on rats.

Similarly, due to arsenics terminal effect on insects, bacteria and fungi, it is used quite extensively in the treatment of wood. In the 1950s a process of treating wood with chromated copper arsenate (also known as CCA or Tanalith) was invented, and for decades this treatment was the chief industrial use of arsenic. An increased appreciation of the toxicity of arsenic resulted in a ban for the use of CCA in consumer products; the European Union and United States initiated this process in 2004. CCA remains in heavy use in other countries around the world however, e.g. Malaysian rubber plantations.

Some arsenic compounds are used medically, for instance, arsphenamine and arsenic trioxide. Arsphenamine as well as neosalvarsan was indicated for syphilis and trypanosomiasis, but has been superseded by modern antibiotics. Arsenic trioxide has been used in a variety of ways over the past 500 years, but most commonly in the treatment of cancer. The US Food and Drug Administration in 2000 approved this compound for the treatment of patients with acute promyelocytic leukemia that is resistant to ATRA. It was also used as Fowler's solution in psoriasis. Recently new research has been done in locating tumors using arsenic-74 (a positron emitter). The advantage of using this isotope instead of the previously used iodine-124 is that the signal in the PET scan is clearer.

Arsenic is also used in making alloys of metals. The primary use of metallic arsenic is in making lead-arsenic alloys. Adding a certain percent of arsenic to them for example strengthens the lead components in car batteries. Gallium arsenide is an important semiconductor material, used in integrated circuits. Circuits made from this compound are much faster (but also much more expensive) than those made in silicon. Unlike silicon it has a direct bandgap, and so can be used in laser diodes and LEDs to directly convert electricity into light.

Due to the toxic nature of many of its compounds in acute doses, arsenic has been used in chemical weapons. After World War I, the United States built up a stockpile of 20,000 tonnes of lewisite (ClCH=CHAsCl2), a chemical weapon that was used as a lung irritant and would also cause skin infections like skin lesions and blisters.

Other anthropogenic sources of arsenic include its unintended release during the mining and smelting of gold, lead, copper, and nickel, in whose ores it commonly occurs. It also occurs as a by-product of iron and steel production.

The arsenic from farming and smelting tends to bind strongly to soil and is expected to remain near the surface of the land for hundreds of years as a long-term source of exposure. 

Naturally occurring pathways of exposure include volcanic ash, weathering of arsenic-containing minerals and ores, and dissolved in groundwater. It is also found in food, water, soil, and air. Arsenic is absorbed by all plants, but is more concentrated in leafy vegetables, rice, apple and grape juice, and seafood. An additional route of exposure is through inhalation.

What are the health effects of arsenic?

Arsenic can cause many different health problems in people, but it is difficult to predict how arsenic will affect a specific individual. Similar arsenic exposures may cause serious health problems for some people and may have no effect on others. The types of health problems that may occur are influenced by things such as the amount of arsenic to which a person is exposed, the length of time exposure occurs, and an individual's sensitivity to the harmful effects of arsenic.

Short-term Exposure to Large Amounts of Arsenic:

Swallowing relatively large amounts of arsenic (even just one time) can cause mild symptoms, serious illness, or death. Milder effects may include swelling of the face, discoloration of the skin, stomach pain, nausea, vomiting; diarrhea; numbness in hands and feet; partial paralysis; and blindness. Serious effects may include coma, internal bleeding, or nerve damage causing weakness or loss of sensation in the hands, arms, feet, or legs.

Long-term Exposure to Small Amounts of Arsenic:

Long-term ingestion (greater than 6 months) of smaller amounts of arsenic that can be found in the environment has the potential to cause many different health problems. Illnesses strongly linked to this type of exposure include bladder cancer, lung cancer, non-melanoma skin cancer, liver cancer, prostate cancer, kidney cancer, cardiovascular disease, diabetes mellitus, damage to peripheral nerves, and changes to the pattern of color or thickness of the skin. For cancer, there is usually a delay of several decades from the time exposure starts until tumors are seen. 

Bangladesh

In the 1970s and 1980s the Bangladesh government, along with international aid agencies spearheaded by UNICEF, undertook an ambitious project to bring clean water to the nation's villages. Too many children were dying of diarrhea from drinking surface water contaminated with bacteria. The preferred solution was a tubewell: a simple, hardy, hand-operated pump that sucks water, through a pipe, from a shallow underground aquifer. The well-to-do could afford them, and with easy loans from nongovernmental agencies, many of the poor also installed the contraptions in their courtyards. A tubewell became a prized possession: it lessened the burden on women, who no longer had to trek long distances with their pots and pails; it reduced the dependence on better-off neighbors; and most important, it provided pathogen-free water to drink. By the early 1990s 95 percent of Bangladesh's population had access to "safe" water, virtually all of it through the country's more than 10 million tubewells--a rare success story in the otherwise impoverished nation.

Tests on 50,000 wells in Bangladesh have shown that around 40% are too contaminated with arsenic to provide drinking water, according to a World Bank official.

Babar Kabir, head of the bank's Water and Sanitation programme in 1999, told Reuters that tests on another 30,000 wells also showed arsenic in nearly 40% of the wells.

The tests, carried out by the United Nations Development Programme (UNDP) represent a first step towards tackling a crisis that has developed in the past decade.

According to some reports, arsenic poisoning could threaten 75 million of Bangladesh's 120 million population, mostly in the north and west of the country.

The World Bank announced in August 1999 that it would provide $30m dollars in aid to Bangladesh to combat arsenic contamination in its water supplies.

Mr Kabir estimated that Bangladesh would eventually require $275 million in the next 10 to 12 years to fight the problem.

He said the World Bank was committed to providing the funds, but added: "We need to determine what is really causing (the contamination) and provide an alternative to get people safe water."

Can I be tested for arsenic?

Several types of tests are available to measure exposure to arsenic, but they cannot predict whether the arsenic in your body will affect your health.  Each test has certain limitations that should be considered when deciding whether to be tested, which test to use, and how to interpret the results. 

Most arsenic stays in the body only a short time. Measuring the level of arsenic in urine is the best way to evaluate exposure that occurred in the last 1 - 2 days. Two types of urine tests are available. The most common test measures the total amount of arsenic and does not distinguish between the toxic "inorganic" forms of arsenic that are a health concern and the less toxic "organic" forms that make up the majority of arsenic in seafood and other foods. The second type of test, for "speciated" or "fractionated" arsenic, measures exposure to just the toxic inorganic forms of arsenic and is better for evaluating exposures relevant to your health. 

Measurement of arsenic levels in hair or fingernails can be useful to evaluate longer-term exposure, but these tests can be difficult to interpret because there are no standardized procedures for conducting the tests and there are no widely accepted standard values to distinguish "normal" from "elevated" test results.

Anthropogenic environmental sources of arsenic stem from

• the continuing use of its compounds as pesticides;

• its unintended release during the mining and smelting of gold, lead,

copper, and nickel, in whose ores it commonly occurs

• the production of iron and steel;

• the combustion of coal, of which it is a contaminant; and

• arsenic-contaminated water brought to ground level by wells.

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