Arsenic

Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in conjunction with sulphur and metals, and also as a pure elemental crystal. Arsenic is a metalloid. It can exist in various allotropes, although only the grey form has important use in industry.

 

Arsenic atoms can assume several different bonding patterns which are the basis of its allotropes, each of which has a different colour; metallic grey, yellow and black arsenic. Interestingly, using a hammer to bang on arsenide minerals releases a garlic-like odour, which is the result of toxic fumes created by the oxidation of arsenic to arsenic trioxide.

Arsenic is notoriously poisonous to multicellular life, although a few species of bacteria are able to use arsenic compounds as respiratory metabolites. Arsenic contamination of groundwater is a problem that affects millions of people across the world.

Historically, Arsenic was commonly used as a rodent poison in English households, and it was also a convenient murder weapon, particularly amongst the ruling classes as you may have read in various novels and non-fiction books. However, Victorian England used arsenic in a number of ways; it was incorporated into wallpaper to prevent the growth of mould during the dark, damp English winters, it was used as the green colouring in paints, candies and candles, and as a preservative in lace.

The main use of metallic arsenic is for alloying with lead. Lead components in car batteries are strengthened by the presence of a very small percentage of arsenic.

Widespread arsenic contamination of groundwater has led to a massive epidemic of arsenic poisoning in Bangladesh and neighbouring countries. It is estimated that approximately 57 million people in the Bengal basin are drinking groundwater with arsenic concentrations elevated above the World Health Organization's standard of 10 parts per billion (ppb).

More recently arsenic has been in the news for being found in rice.  Rice holds higher levels of arsenic than other grains and acts as one of nature’s “great scavengers of metallic compounds.” Unlike, millet or polenta, rice planted in arsenic-contaminated fields acts as a vacuum for the toxin.

Rice from different countries contain differing levels of arsenic.  It's recommended that rice is washed before cooking and rinsed afterwards to lessen the effects.

Currently, the FDA in America doesn't have safety levels for arsenic in rice. They've cautioned against making state-by-state or country-by country comparisons in Inorganic Arsenic levels for rice, citing the varying factors that can influence arsenic concentrations, such as soil composition, fertilizers, seasonal variability, and water-use practices.

Evidence-based public health advocates also recommend that, given the lack of regulation or labelling for arsenic in the U.S., children should eat no more than 1 to 1.5 servings per week of rice and should not drink rice milk as part of their daily diet before age 5. They also offer recommendations for adults and infants on how to limit arsenic exposure from rice, drinking water, and fruit juice.

A 2014 World Health Organization advisory conference will consider limits of 200–300 ppb for rice.  The proposed new EU recommendations will limit 200 parts of arsenic per billion for adults and just 100 ppb for children and babies.

For more information visit:-
http://en.wikipedia.org/wiki/Arsenic
http://www.theguardian.com/science/punctuated-equilibrium/2011/oct/14/1
https://time.com/3592399/arsenic-rice/
http://www.dailymail.co.uk/news/article-2817542/More-half-rice-products-exceed-new-EU-limits-ARSENIC.html

Mercury

Mercury is a chemical element with the symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum (from Greek "hydr-" water and "argyros" silver)

 

 

Mercury is remarkable because it is the only metal that is liquid at room temperature. It is a dense, lustrous grey metal. Mercury is extremely rare in the Earth's crust and in the wild, it typically is concentrated near volcanically active areas, either as the pure metal or in a number of minerals.

 

Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, mercury switches, mercury relays, fluorescent lamps and other devices, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favour of alternatives such as alcohol- or galinstan-filled glass thermometers and thermistor- or infrared-based electronic instruments.

The reason mercury was so popular is because it readily forms stable amalgams with a number of other metals, particularly silver and gold, making them workable at lower temperatures, and these amalgams have been the source of many instances of mercury poisoning.

Amalgam Filling

 

Biologists are quite interested in mercury because it is highly toxic to life, causing both acute and chronic poisoning. Mercury can be absorbed through the skin and mucous membranes and mercury vapors can be inhaled. Mercury is concentrated in the body over the lifetime of the individual, and it also becomes more concentrated when one animal eats another, which is how it moves up the food chain. This is the reason why the flesh of tuna, a long-lived apex predator in the oceans, contain such high levels of mercury.

For more information visit:-

http://www.theguardian.com/science/grrlscientist/2013/jan/25/1?guni=Article:in%20body%20link

http://en.wikipedia.org/wiki/Mercury_(element)



Antimony

Antimony is a chemical element with symbol Sb (from Latin: stibium) and atomic number 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb₂S₃).

 

Antimony compounds have been known since ancient times and were used for cosmetics.  Nowadays Antimony is mainly used as its trioxide in making flame-proofing compounds and in certain alloys.  The Egyptians had a hieroglyph for Antimony......

Antimony has no known biological role, but it is a potent toxin, with effects that are similar to arsenic poisoning. When ingested, antimony strongly bonds to sulfur-containing enzymes, thereby inactivating them. Antimony is even more toxic when inhaled as the gas, stibine, SbH₃. Poisoning by antimony ingestion manifests as gastric distress, and large doses cause vomiting, and kidney and liver damage, followed by death a few days later.

It was thought that Mozart was a victim of poisoning at the hand of rival composer, Antonio Salieri, although historians don't give this hypothesis any credence. It is far more likely that Mozart was poisoned by his doctors. A heavy drinker, Mozart was known to also overindulge in the popular hangover cure of the day that contains antimony, tartar emetic, C₄H₄KO₇Sb, which was provided by his doctors.

Stibnite

For some time, China has been the largest producer of antimony and its compounds, with most production coming from the Xikuangshan Mine in Hunan. The industrial methods to produce antimony are roasting and subsequent carbothermal reduction or direct reduction of stibnite with iron.

For more information visit:-
http://www.theguardian.com/science/grrlscientist/2012/feb/24/1?guni=Article:in%20body%20link
http://en.wikipedia.org/wiki/Antimony

Lead.

Lead is a chemical element in the carbon group with symbol Pb (derived from the Latin: plumbum) and has the atomic number 82. It is a soft and malleable metal and has a bluish-white colour after being freshly cut, but soon tarnishes to a dull grey colour when exposed to air. It has a shiny chrome-silver luster when it is melted into a liquid.  Lead rarely occurs in its elemental form in the wild. It is typically found in ores along with copper, and in smaller quantities with zinc and silver.

Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield.  It was also commonly used in pipes for many hundreds of years, giving rise to the English words, "plumbing", "plumber", "plumb", and "plumb-bob" -- words derived from the same Latin root with lead.

If ingested, lead is poisonous to animals, including humans. It damages the nervous system and causes brain disorders. Excessive lead also causes blood disorders in mammals. Like the element mercury, another heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bones. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China.

Lead pigments were used in lead paint for white as well as yellow, orange, and red. Most uses have been discontinued due of the dangers of lead poisoning. Lead chromate is still in industrial use. Lead carbonate (white) is the traditional pigment for the priming medium for oil painting, but it has been largely displaced by the zinc and titanium oxide pigments. It was also quickly replaced in water-based painting mediums. Lead carbonate white was used by the Japanese geisha and in the West for face-whitening make-up, which was detrimental to health.

Tetraethyllead was used in leaded fuels to reduce engine knocking, but this practice has been phased out across many countries of the world in efforts to reduce toxic pollution that affected humans and the environment.

Lead is a highly poisonous metal (regardless if inhaled or swallowed), affecting almost every organ and system in the body. The main target for lead toxicity is the nervous system, both in adults and children. Long-term exposure of adults can result in decreased performance in some tests that measure functions of the nervous system. Long-term exposure to lead or its salts (especially soluble salts or the strong oxidant PbO2) can cause nephropathy, and colic-like abdominal pains. It may also cause weakness in fingers, wrists, or ankles.

For more information visit:-
http://en.wikipedia.org/wiki/Lead
http://www.theguardian.com/science/grrlscientist/2013/feb/15/1?guni=Article:in%20body%20link