The word arsenic is derived from the Persian zarnikh and Syriac zarniqa, later incorporated into Greek as arsenikon, which meant “masculine” or “potent” and referred primarily to orpiment, or yellow arsenic. The word became arsenicum in Latin and arsenic in old French, from which the current English term is derived.
Occurrence & Distribution: Arsenic is widely distributed in nature and principally occurs in the form of inorganic or organic compounds. In soils, arsine gases may be generated by fungi and other related micro-organisms. The two major toxic forms of arsenic are trivalent arsenite(AsIII) and pentavalent arsenate(AsV). Different forms of arsenic have different toxicities, with arsine gas being the most toxic form of the inorganic oxyanions, arsenite are the most toxic forms and arsenate, the less toxic forms. The organic (methylated) arsenic forms are considered least toxic. Exposure to inorganic compounds may occur in a number of ways through certain industrial effluents, pesticides, chemical alloys, combustion of fossil fuels, wood preservative agents, occupational hazards in mining and dissolution in drinking water. The most commonly found arsenic compounds in drinking water are arsenate or arsenite. However, groundwater is notoriously prone to chemical and other types of contamination from natural sources or by anthropogenic activities.
Problem: Approximately 20 incidents of groundwater arsenic contamination have been reported from all over the world. Of these, four major incidents were recorded in Asia including: Bangladesh; West Bengal, (India); Inner Mongolia, (China); and Taiwan. Arsenic contaminated groundwater in India and Bangladesh and its consequences to the human health have been reported as one of the world’s biggest natural groundwater calamities to mankind. In India, seven states namely- West Bengal, Jharkhand, Bihar, Uttar Pradesh, Assam, Manipur and Chhattisgarh have so far been reported affected by Arsenic contamination in groundwater above the permissible limit of 10 µg/L.
Historical past: Mineral forms of arsenic were known as early as the fourth century BC, but the German scholastic Albertus Magnus is usually accredited with the discovery of the element around 1250 A.D. The first precise directions for the preparation of metallic arsenic, however, are found in the writings of Paracelsus, a physician-alchemist in the late Middle Ages who is often called the father of modern toxicology. Arsenic occurs free in nature, but is most often found in the minerals arsenopyrite (FeAsS), realgar (AsS) and orpiment (As2S3). Today, most commercial arsenic is obtained by heating arsenopyrite.
Magnitude of the arsenic contamination: The British Geological Survey analyzed that approximately 21 million people in Bangladesh were drinking water with arsenic levels > 50 µg/L. The WHO maximum permissible limit for arsenic in drinking water is 10µg/L.
Toxicity: The common symptoms of chronic arsenic toxicity due to prolonged drinking of arsenic contaminated water pigmentation, keratosis, arsenicosis produces protean manifestations like weakness, chronic respiratory disease, peripheral neuropathy, liver fibrosis, peripheral vascular disease, etc. For example, the incidence of arsenic related cancer was reported to be 5.1% among 4865 cases of arsenicosis examined in West Bengal, (India) during the period of 1983 to 2000.
Therapeutic uses: Arsenic has earned a place in history both as a favoured poison and as a miracle drug. It figured prominently in the development of chemotherapeutic agents by renowned physicians and scientists such as Thomas Fowler, Paul Ehrlich, Sahachiro Hata and Albert Neisser, and became the first antimicrobial agent to be effective against the great pox syphilis.
Realgar: Hippocrates used the arsenic sulphides realgar and orpiment to treat ulcers and abscesses, and Dioscorides used orpiment as a depilatory. The use of arsenic in traditional Chinese medicines dates back to 200 BCE and was described in the first traditional Chinese medicine book Shen Nong Ban Cao Jing. A common concept in ancient Chinese medicine was to use a poison against a poison. Indian Ayurvedic herbal medicines often contained arsenic, lead and mercury, and it was thought the mineral elixir made from the “essence of five planets” could give perpetual life. Up to the 1940s, arsenic was successfully used to treat syphilis; it was a key ingredient in a compound named Salvarsan. It has also been given to leprosy victims and sufferers of yaws (a contagious tropical skin disease).
Fowler’s solution: In 1786, Thomas Fowler, a British physician, published a study on the effectiveness of his solution of 1% potassium arsenite which he called “Liquor mineralis”, for “agues, remittent fevers, and periodical headaches”. In 1809 “Liquor mineralis”, known by that time as “Fowler’s solution”, was accepted into the London Pharmacopeia and became widely used as an alternative to quinine for “agues” (malaria) and was used for “sleeping sickness” (trypanosomiasis). By the 1880s Fowler’s Solution was used for a variety of other ailments including asthma, eczema, psoriasis, anaemia, hypertension, gastric ulcers, heartburn, rheumatism, and tuberculosis, and arsenic paste was used to treat cancers of the skin and breast. Other arsenic preparations at the time included Donovan’s solution (arsenic triiodide and mercuric iodide) and de Valagin’s solution (arsenic trichloride), both used to treat similar disorders. In 1878 Fowler’s solution was discovered to lower the white cell count in chronic myelogenous leukaemia and was used as the main treatment for leukaemia until the advent of radiation and chemotherapy in the 20th century. Fowler’s solution remained a treatment for many conditions well into the 20th century and is listed along with arsenic trioxide and sodium arsenate in the 1914 edition of the American Medical Association’s Handbook of Useful Drugs as treatment for skin cancer, chronic inflammatory skin disorders, malaria, syphilis and protozoal diseases. Later in 1912 Ehrlich developed neoarsphenamine, Neo-Salvarsan, or drug “914”, which was water soluble and easier to administer. Salvarsan and Neo-Salvarsan were listed in the American Medical Association’s 1914 Handbook of Useful Drugs as an effective treatment for primary syphilis and spirillar diseases such as relapsing fever and Vincent’s angina, and for later stages of syphilis in combination with mercury.
Arsenic compounds began to be used in agriculture as ingredients in insecticides, rat poisons, herbicides and wood preservatives, as well as pigments in paints, wallpapers and ceramics.
Arsenic poisoning: The toxic properties of arsenic were known by Hippocrates, who in 370 BCE described abdominal colic in a miner of metals, and similar properties were described of mercury and arsenic. Pedanius Dioscorides, author of the historical pharmacopeia De Materia Medica and a Greek physician in the court of the Roman Emperor Nero, described arsenic as a poison, which was used by Nero to poison his step-brother Tiberius Britannicus in 55 CE and secure his position as Roman Emperor. The odourless and tasteless properties of inorganic arsenic compounds such as arsenic trioxide (white arsenic) made them an ideal poison. White arsenic was readily made by heating arsenic ore; this produced a white crystalline powder which was soluble in water and virtually undetectable in food or drink.
Poisoned victims: When Napoleon died in 1821, his doctors recorded the official cause of death as stomach cancer. Although trace amounts of arsenic were found in Napoleon's hair, the amount could have been absorbed naturally and not intentionally administered. Napoleon could have absorbed arsenic through eating a seafood meal, as it appears naturally in sea water and in sea dwellers. Towards the end of Napoleon's life, he spent increasing amounts of time indoors, where his home was decorated with Paris Green wallpaper.
In the 1890s, medical authorities in Italy were concerned about the unexplained deaths of over a thousand children. A chemist, E. Gosio, was consulted. Gosio did not examine the children, but the rooms where the deaths occurred. He discovered the deaths had two common factors: Paris Green wallpaper in the rooms and a presence of mildew. The children, being shorter and playing on the floor, inhaled the heavy arsine, the byproduct of arsenic and dampness. The removal of Paris Green from wallpaper prevented further deaths.
World Bank and DFID (UK Department for International Development) tested a few of the water filters and found to be consistently removing arsenic to bring it down to a satisfactory level:
- Alcan-enhanced activated alumina
- Sono-3 kalshi
- BUET-activated alumina
- Stevens Institute of Technology filter