Arsenic

Arsenic (As) is a naturally occurring chemical, common in especially high concentrations in sedimentary rocks—like the sandstone, shale, and coal deposits in Colorado, Utah, South Dakota, and Wyoming for example. Arsenic can also be found in ground water with varying concentrations. 

There is a significant anthropogenic source of arsenic as well. Predominantly, arsenic is introduced into the natural system from smelting operations, the use of some pesticides, and wood preservatives. Mining operations often discharge large amounts of arsenic which can leach into the ground water or get washed along in run-off and accumulate in streams. Arsenic is a particular concern at superfund sites where the chemical signature of the previous operation lingers.

The incorrect disposal of electronic waste constitutes one of the most dangerous sources of inorganic arsenic into the environment. Arsenic is present in circuit boards, LCD displays, and computer chips. As these electronic parts pile up in landfills, the arsenic present leaches into the soil at those sites affecting the soil chemistry and possibly the ground water composition as well.

When arsenic is present in the ground water and soil, it has a variety of influences on organisms depending on the organism. In humans, ingestion of arsenic at low doses will result in irritation of the digestion system (stomach, intestines, etc) and consumption of large doses is lethal. Arsenic has also been proven to be a carcinogen, cited as a cause in everything from skin cancer to liver cancer.

Ecologically speaking, arsenic has shown to act as a growth stimulant and development inhibitor depending on the species. Arsenic has been used as a pesticide until its production ban in 1985. Studies have shown that a small amount of arsenic in the terrestrial system may actually stimulate plant growth. There are also some plant species, like brake ferns, that are hyper-accumulators of arsenic. In terms of mammals, research has shown that most animals are able to excrete excess arsenic without experiencing any side effects. However, arsenic can negatively impact fetus development in most mammals. Arsenic has shown varying effects in birds as well. While chickens experience stimulated growth when fed amounts of arsenic, ducks experienced stunted growth. Similar effects were observed in aquatic plants and animals. Aquatic organisms are primarily sensitive to arsenic in early development. Currently, there appears to be no tropic magnification through the aquatic system; however, research is ongoing (like this paper on the bioaccumulation of arsenic in a lake in China).

This particular method of introducing arsenic into the ecosystem can be compared to the practices of mining companies and its consequences—contaminating water resources and other ecological damages. Extensive research has been done regarding the specific consequences of mining in the western United States.

Another widely-used method of electronic waste disposal is to simply set fires to the unusable parts. This introduction of arsenic into the atmosphere has severe human health implications. As exhibited by workers in old smelter plants, inhaling arsenic can cause lung cancer (in fact, a linear relationship has been shown by research by the National Cancer Institute)  as well as an array of peripheral nervous disorders. Mammals, on the other hand, seem to be able to cope much better with arsenic in the atmosphere-shown by this study of rabbits.

 

General Background
http://www.clu-in.org/contaminantfocus/default.focus/sec/arsenic/cat/Toxicology/
Arsenic Speciation: http://www.allbusiness.com/north-america/canada/321073-1.html|
Toxicity Research: http://lib.bioinfo.pl/meid:224917
Extensive Explanation: http://www.inchem.org/documents/ehc/ehc/ehc224.htm


Interesting Links
How to deal with arsenic when recycling electronics - http://www.ehow.com/how_2238195_deal-arsenic-recycling-electronics.html
Arsenic in E-waste - http://www.videojug.com/tag/e-waste-recycling
Human health implications - http://www.atsdr.cdc.gov/csem/arsenic/exposure_pathways.html
Mitigation possibilities - http://phys4.harvard.edu/~wilson/arsenic/references/Sarkar,EST.pdf
    http://www.sahra.arizona.edu/unesco/casestudies/BangladeshAs.pdf

Picture courtesy of the World Bank - http://siteresources.worldbank.org/INTSAREGTOPWATRES/Images/Arsenic-2-hands.jpg

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