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.

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Posted on January 16, 2015, in Useful Information. Bookmark the permalink. Leave a comment.

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