Urinary arsenic (As) provides an indication of recent or ongoing exposure to various forms of the metalloid. Urine As may also indicate, to a lesser extent, endogenous detoxification of inorganic As. The less toxic organic forms of As from seafood have a circulating half-life of about 48 hours, and are rapidly excreted from the body. Consider very recent shellfish consumption with a finding of high urinary As.
Food, well water, and air are common sources of exposure for As. The predominant dietary source of As is seafood, followed by rice/rice-based products, mushrooms, and poultry (antiparasitics in feed). While fish/shellfish contain the highest levels of As, most abundant are the much less harmful organic As species arsenobetaine and arsenocholine; they are rapidly and efficiently excreted.
Some sea vegetables may contain the more toxic inorganic As. Other common sources of As include: tobacco, certain pesticides, fungicides (orchards, vineyards), smog, and older wood preservatives (CCA; pressure treated wood/sawdust). Copper and lead smelting, as well as hazardous waste sites contribute to environmentally-derived As exposure.
Significant exposure to inorganic As may be associated with malaise, muscle weakness, vomiting, diarrhea, and dermatitis. Long-term exposure may increase risks for diabetes, vascular disease and cancer (skin, bladder, kidney and lung). As may also adversely affect the peripheral nervous and hematopoietic systems.
The W.H.O has stated that in utero and early childhood As exposure has been linked to negative impacts on cognitive development and increased deaths in young adults. Physiological detoxification of inorganic As entails a sequence of oxidation/reduction and methylation
reactions, with final conjugation to glutathione prior to excretion in urine and bile.
Genetic and epigenetic factors may impair As detoxification. Compromised status of methionine, cysteine, glutathione, folate and B-12 may result in diminished capacity for endogenous detoxification of As. Inorganic As accumulates in hair, nails, skin, thyroid gland, bone and the gastrointestinal tract. Exposure to inorganic As over the past few months may be assessed with hair elemental analysis. Chelation may acutely increase urinary excretion of inorganic As.
Arsenic
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