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What is Arsenic

Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid.

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Arsenic – the “Poison of Kings”

The odorless and tasteless properties of inorganic arsenic compounds such as arsenic trioxide (white arsenic) made them an ideal poison. Single dose could produce severe diarrhea and vomiting, paralysis, and death.

Pedanius Dioscorides, author of the historical pharmacopeia De Materia Medica and a Greek physician, described arsenic as a poison, which was used by Roman Emperor Nero to poison his step-brother Tiberius Britannicus in 55 CE and secure his position as Roman Emperor.
There have long been rumors to suggest that the final agonies of Napoleon Bonaparte in 1821 were due to the repeated administration of arsenic by someone in his cortege.
1952, Claire Booth Luce was the United States ambassador to Italy. In 1955 she fell seriously ill with arsenic poisoning. The ambassador was the target of extermination by agents of the Soviet Union. Medical analysis eventually determined that the poisoning was caused by arsenate of lead in paint dust falling from the stucco that decorated her bedroom ceiling. The episode debilitated Luce physically and mentally, and she resigned her post in December 1956.

 

Arsenic – the “Saviour of Syphilis”

Arsenic also has a place in medical history, particularly in the treatment of  two great scourges of disease in our time, trypanosomiasis or “sleeping sickness”, and syphilis or the “great pox”.  Paul Ehrlich’s and Sahachiro Hata’s new therapeutic discovery in 1909 for treating syphilis, Salvarsan (Arsphenamine), was hailed as “the arsenic that saved”.

In the early 19th century arsenicals were also developed to successfully treat trypanosomiasis (sleeping sickness), and currently arsenic trioxide is approved to treat refractory acute promyelocytic leukaemia.

 

How does arsenic get in drinking water and food?

Groundwater contamination by arsenic is often a natural phenomenon attributed to subsurface sediments containing small amounts of arsenic. The sediments of alluvial deltas originate from the mountains in the upstream river catchment and have been deposited during thousands of years. Mountain erosion leads to a release of rock-forming minerals and arsenic into the hydrosphere. Eroded iron turns to rust, iron(hydr)oxide, and forms particles as well as coatings on the surface of particles such as silt and sand. These iron(hydr)oxides are capable of scavenging dissolved arsenic from water and binding it to its surface Suspended particles with iron(hydr)oxide coatings and adsorbed arsenic are washed into rivers and transported downstream. Arsenic is thus brought to the river deltas bound to suspended solids and deposited in the soil with the settling sediments. River water with high loads of particles generally exhibits a characteristic red to yellowish brown colour caused by the iron, a phenomena that gave the Red River its name.

In the flat lowlands of the Red River Delta, suspended particles are usually deposited during floods. This was particularly the case in ancient times when the flow of the river water was not controlled by dykes. For thousands of years, deposits of river sediments have created the soil layers (sediments) that form the delta as it is known today. These sediments reach more than a hundred meters below the today's topsoil layer. Arsenic adsorbed on the surface of sediment particles is thus buried in the structure of the delta underground. The present Red River Delta was largely formed by sediments deposited in the Holocene period (last 10,000–12,000 years). Read more

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The arsenic remains fixed in the sediments as long as the groundwater contains sufficient dissolved oxygen. However, arsenic is released from the sediments if these come into contact with oxygen-depleted groundwater. During the inundation periods, high loads of river sediments (suspended particles) are frequently covering of the topsoil layers including its vegetation. This process results in the entrapment and subsequent burial of natural organic matter (rotting plants, peat) in the sediment structure. Organic matter can serve as substrate ("food") for microorganisms to thrive on. These microorganisms consume dissolved oxygen to degrade organic material, thereby leading to an oxygen depletion in the groundwater (anoxic conditions). Under anoxic conditions, some microorganisms can use iron(hydr)oxides as a source of energy instead of oxygen. Degradation of solid iron(hydr)oxide particles releases arsenic formerly attached firmly to the particle surface. Read more

About one third of the arsenic in the atmosphere comes from natural sources, such as volcanoes but the rest comes from man-made sources. Arsenic has long being used in industry and agriculture, and even residential purposes.

- As recently as 2003, arsenic was used to treat lumber. Outdoor structures, such as decks, play equipment, and furniture made around or before this time may contain arsenic, and can leach into the groundwater supply.
- In the 19th and 20th century, farmers relied heavily on arsenic-containing pesticides. While most forms of arsenic are currently banned, residues remain in older farmland. In addition, monosodium methyl arsenate (MSMA) is still in use, especially where weeds have developed resistance to modern herbicides. Farmland contaminated with organic arsenic can leach into the groundwater supply.
- Arsenic is used industrially as an alloying agent, as well as in the processing of glass, pigments, textiles, paper, metal adhesives, wood preservatives and ammunition. It is also a byproduct of copper smelting, mining and coal-fired power plants. Industries release thousands of pounds of arsenic into the environment every year.
- Fish, shellfish, meat, poultry, dairy products and cereals can also be dietary sources of arsenic, although exposure from these foods is generally much lower compared to exposure through contaminated groundwater. In seafood, arsenic is mainly found in its less toxic organic form.

 

Daily arsenic intake

You probably didn't know that you do intake a small amount of arsenic daily. From the arsenic life cycle images above, as arsenic came down with the rain, it's adsorbed by vegetables and plant which is then consumed by animals.
Arsenic can be found in items such as wine, juice, syrup, glues and pigments. Inorganic arsenic compounds were found in apple juice, orange and grapefruit juice, in vinegars and salad dressings, in milk and dairy products, beef, pork, poultry and in cereal. Arsenic is also found in most unshelled rice but also in shelled rice and in its products.
The picture below shows an example of arsenic level in our normal daily food.

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SMALL amounts of Arsenic are REQUIRED for normal operation of the body. An average adult can intake between 30 to 50 ppb of arsenic daily. Most Arsenic compounds are soluble in water to some extent and thus are easily transported in the blood stream and assimilated by the body. The water solubility also helps remove some of the Arsenic via the urine and the excrement.
Let say your daily consumtion is a bowl of cheerios, couple small bowls of rice, half pound of chicken, half pound of beef, a few shrimps, drink couple glass of juice and a glass of wine. That alone is already around 10µg. Now let assume your drinking water is at 10 ppb (10µg) per liter, an average person consumed 3 liters per day which bring to a total of 40 µg. This is why it is so important to maintain a low level of arsenic in drinking water!

A drinking water standard of 0.05 mg/L (equal to 50 parts per billion, or ppb) arsenic was originally established in the United States by the Public Health Service in 1942. No other action was taken until January 2001, when the Clinton administration in its final weeks promulgated a new standard of 0.01 mg/L (10 ppb) to take effect January 2006. The Bush administration suspended the midnight regulation, but after some months of study, the new EPA administrator Christine Todd Whitman approved the new 10 ppb arsenic standard and its original effective date of January 2006.