Chapter 3I: Arsenic: Biomarkers of Exposure and Human Biomonitoring

Arsenic is a potentially toxic element to humans, animals and plants. Exposure of humans to arsenic and its compounds may originate from both natural and anthropogenic sources, including industrial activities, and consumption of food and beverages. Arsenic is found in nature in a variety of inorganic and organic compounds. The distribution, mobility, and toxicity of arsenic in nature are species dependent. For example, inorganic arsenic species are generally much more toxic than organic species, and of these trivalent arsenic species (arsenite and methylated arsenic compounds) are much more toxic than pentavalent (arsenate and methylated compounds), while arsenobetaine and arsenocholine are considered to be non-toxic. Inorganic arsenic is also known to be carcinogenic in humans. Therefore, speciation of arsenic is essential in providing an accurate assessment of environmental and human health risks, rather than using only total arsenic concentrations as has been the practice for many years. There are three population groups at high exposure risk: (1) the occupationally exposed, (2) people drinking water with abnormally high concentrations of arsenic, (3) children living in the close vicinity of arsenic contaminated (copper) smelters. Hair, nail, blood and mainly urine can be analysed to monitor exposure to inorganic arsenic. However, matrix complexity often prevents complete identification of arsenic compounds (speciation) so that only total arsenic can be determined in non-liquid biological samples. Arsenic species are more easily determined in blood and urine; nevertheless, for kinetic reasons, the determination of urinary metabolites is preferred for the biomonitoring of exposure to arsenic.