Metal : Arsenic

Fig-1

INTRODUCTION

• Atomic number: 33
• Atomic symbol: As
• Atomic weight: 74.92160
• Density: 5.776 grams per cubic centimeter
• Phase at room temperature: solid
• Melting point: 1,502.6 degrees Fahrenheit (817 degrees Celsius)
• Boiling point: 1,117.4 F (603 C)
• Number of isotopes: 33; 23 whose half-lives are known; 1 stable
• Most common isotopes: As-75 (100 percent natural abundance)

Fig-2

• An arsenic atom has 33 electrons and 33 protons with five valence electrons (those that can participate in forming chemical bonds with other electrons) in its outer shell.

  History

• Arsenic was used as a healing agent after Greek physicians such as Hippocrates and Galen popularised its use.

• Arsenic compounds became available as solutions, tablets, pastes, and injectable forms. Fowler’s solution, a 1% arsenic trioxide preparation, was widely used during the 19th century.

• As recently as 1958, the British Pharmaceutical and Therapeutic Products handbook edited by Martindale, listed the indications for Fowler’s solution as leukemia, skin conditions (psoriasis, dermatitis herpetiformis, and eczema), stomatitis and gingivitis in infants, and Vincent’s angina. Fowler’s solution was also prescribed as a health tonic.

• Chronic arsenic intoxication from the long term use of Fowler’s solution caused haemangiosarcoma, angiosarcomas of the liver, and nasopharyngeal carcinoma.

• Arsenic was the primary treatment for syphilis until World War II. Arsphenamine (neoarsphenamine), a light yellow compound containing 30% arsenic was used intravenously to treat syphilis, yaws, and some protozoan infections

Sources of exposure

• Arsenic is a natural component of the earth’s crust and is widely distributed throughout the environment in the air, water, and land.
• It can exist in inorganic or organic form, inorganic form being generally considered more toxic.
• About one-third of the arsenic in the atmosphere comes from natural sources, such as volcanoes, and the rest comes from man-made sources.
• Industrial processes such as mining, smelting, and coal-fired power plants all contribute to the presence of arsenic in air, water, and soil.
• High levels of arsenic can be found in drinking water

Fig-3

• Arsenic is found in the following foods: 
  • Rice 
  • Cereal 
  • Chicken 
  • Mushrooms
  • Seafood 

Fig-4

• Pressure-treated woods

Fig-5

Arsenic in food

Watch an interesting video about Arsenic in food.

While eating lunch, three students begin to wonder about the safety of eating foods that contain arsenic. Through their research, the students will discover where arsenic is found, how it is used, and its effects on human health.

Mechanism

Inorganic :

• Arsenate – exists in the +5 oxidation state.
• Arsenite- exists in +3 oxidation state.

Organic As- methylated

• Monomethylarsonous acid (MMA3)
• Dimethylarsinous acid (DMA3)

Arsenic toxicity and potential mechanisms of action

• The absorbed arsenic undergoes hepatic biomethylation to form monomethylarsonic acid and dimethylarsinic acid that are less toxic but not completely innocuous. About 50% of the ingested dose may be eliminated in the urine in three to five days. Dimethylarsinic acid is the dominant urinary metabolite (60%–70%) compared with monomethylarsonic acid. A small amount of inorganic arsenic is also excreted unchanged. After acute poisoning, electrothermal atomic absorption spectrometry studies show that the highest concentration of arsenic is in the kidneys and liver.

 

• In chronic arsenic ingestion, arsenic accumulates in the liver, kidneys, heart, and lungs and smaller amounts in the muscles, nervous system, gastrointestinal tract, and spleen. Though most arsenic is cleared from these sites, residual amounts remain in the keratin-rich tissues, nails, hair, and skin. After about two weeks of ingestion, arsenic is deposited in the hair and nails

Arsenic Metabolism

 

 

 

 

 

 

 

 

 

 

 

Uses

• ‘Poison of Kings’
• Arsenic is mostly used in compounds. A much smaller amount of the element itself is used in alloys. For example, certain parts of lead storage batteries used in cars and trucks contain alloys of lead and arsenic.
• Arsenic has also been used to make a lead shot in the past. The amount of arsenic used in these applications is likely to continue to decrease. It is too easy for arsenic to get into the environment from such applications.
• Minute amounts of arsenic are used in the electronics industry. It is added to germanium and silicon to make transistors. A compound of arsenic, gallium arsenide (GaAs), is also used to make light-emitting diodes (LEDs). LEDs produce the lighted numbers in hand-held calculators, clocks, watches, and a number of other electronic devices.
• Medical uses- syphilis, psoriasis

TOXICITY

Health effects: Signs and Symptoms

Inorganic arsenic is a confirmed carcinogen.

Acute effects:

•  vomiting
• abdominal pain
• diarrhea
• numbness
•  tingling of the extremities
• muscle cramping
• death (in extreme cases)

Long-term effects:

• pigmentation changes
• skin lesions
•  hard patches on the palms and soles of the feet (hyperkeratosis)
• bladder cancer
• lung cancer

Other effects:

• developmental effects
• diabetes
• pulmonary disease
• cardiovascular disease

Diagnosis

Pathological testing:

• blood
• hair
• urine
• fingernail samples

Urine tests should be done within 1-2 days of the initial exposure.

Tests on hair and fingernails can determine the level of arsenic exposure over the period of up to 12 months.

Chronic exposure levels between 0.1 to 0.5mg/kg

Acute toxicity has a range of 1 to 3mg/kg.

Treatment

• removing clothes that could be contaminated with arsenic
• thoroughly washing and rinsing affected skin
• blood transfusions
• taking heart medication in cases where the heart starts failing
• using mineral supplements that lower the risk of potentially fatal heart rhythm problems
• observing kidney function
• bowel irrigation

this video is a graphical representation of symptoms, complications, and treatment of arsenic poisoning.

Differential Diagnosis

Acute arsenic toxicity presents similarly to many gastrointestinal conditions including:

• Guillain-Barre
• Campylobacter
• Shigella
• Salmonella
• Escherichia coli
• Clostridium difficile
• Bacillus cereus
• Vibrio cholerae
• Rotavirus
• Giardia lamblia
• Cryptosporidium
• Entamoeba histolytica

Prevention

• households having arsenic removal systems
• testing the water for traces of arsenic
• taking care when harvesting rainwater
• well depth: the deeper a well is dug, the less arsenic in water.
• AWARENESS program about the harmful effects.

References:

1. 1. https://www.who.int/news-room/fact-sheets/detail/arsenic
   2. https://en.wikipedia.org/wiki/Arsenic_poisoning
   3. Hughes MF, Beck BD, Chen Y, Lewis AS, Thomas DJArsenic exposure and toxicology: a historical perspective
      Toxicol Sci, 123 (2011), pp. 305-332
   4. Fig-1:https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcSz0c0_IiDMG0I222sYH0onmaVb_nkTtj8ZNiYDx4wrGXwCKOSM&usqp=CAU
   5. Fig-2:https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcQcCgUGuwQWc_LZ-AL7QdSKi6uYoq_weTO1i1IGlaAqclrhUuzX&usqp=CAU
   6. Fig-3:https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcS775EBJzXwOl5cBCu6rmgBgFvm3FkGMSx1EZ1WOZurr53DlYTd&usqp=CAU
   7. Fig-4:https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcTm6uX3u9qET0ytLHnO_QPCBW8nO1ypkQXCo0rd6i0ZRIffR4Tu&usqp=CAU
   8. Fig-5:https://contentgrid.homedepot-static.com/hdus/en_US/DTCCOMNEW/Articles/benefits-of-pressure-treated-wood-section-1.jpg”>benefits-of-pressure-treated-wood-section-1.jpg
   9. Fig-6:https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcQuWzhpGuHn24xKAAMRTR2-dKzWRi72WmFXsiqSNIPlcTlkm0IE&usqp=CAU