Arsenic is an ubiquitous element, and although it is apparently essential for certain animal species, its significance in man lies in the acute and chronic toxicity that results from overexposure. Fish and crustaceans contain particularly high amounts of non-toxic forms of organic arsenic in their tissues, and in the human body the element is concentrated largely in hair and nails. The element is present in the ores used in the smelting of copper, lead and zinc, and the resulting production of arsenic trioxide is a potential health hazard. In both inorganic and organic forms the element is widely used as an insecticide, herbicide, feed additive and wood preservative. More recently, the semiconductor industry has become a major user of arsenic compounds.
Toxicity
Although there are substantial differences in the toxicities of different arsenic compounds, acute exposure usually causes abdominal pain, weakness, trembling, increased salivation, jaundice, diarrhoea and vomiting. Long term exposure to smaller amounts causes similar symptoms in a milder form which, of course, resemble those of many chronic diseases. This similarity has made the element popular for many centuries as a deliberate poison. Concern regarding the exposure of industrial workers to arsenic compounds has increased following the realisation that arsenic may be carcinogenic.
Traditional Asian remedies may contain substantial amounts of arsenic, and cases of toxicity from their use have been reported both from India and the UK.
Recent descriptions of siuations with whole populations suffering from arsenic toxicity in areas of Bangladesh and China are associated with drinking water with high natural levels of arsenic, made available by new wells
The element probably exerts its toxic effects by its ability to bind to sulphydryl groups in tissue proteins, although cellular metabolism may also be disrupted by arsenate analogues of phosphate compounds. The well known antidote to arsenic poisoning, British Anti Lewisite (BAL; Dimercaprol) is effective by virtue by its ability to bind arsenic through its sulphydryl groups.
Laboratory Indices of Exposure
Arsenic is excreted in the urine and measurement of the urinary arsenic output is the determination of choice. Concentrations both in blood and urine will increase after the consumption of sea food. Separation of the arsenic species in urine is necessary to distinguish between the toxic and non-toxic forms. Alternatively known sources of non-toxic arsenic should be excluded from the diet some five days before making an assessment.
References:
Kew J, Morris C, Aihe A, Fyshe R, Jones S, Brooke D. Arsenic and mercury intoxication due to Indian ethnic remedies. BMJ 1993; 306: 506-7
Vahter M. What are the chemical forms of arsenic in urine and what can they tell us about exposure. Clin Chem 1994; 40: 679-680