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BIOMARKERS OF EXPOSURE: A CASE STUDY WITH INORGANIC ARSENIC
Citation:
HUGHES, M. F. BIOMARKERS OF EXPOSURE: A CASE STUDY WITH INORGANIC ARSENIC. ENVIRONMENTAL HEALTH PERSPECTIVES. National Institute of Environmental Health Sciences (NIEHS), Research Triangle Park, NC, 114(11):1790-1796, (2006).
Impact/Purpose:
to study biomarkers to quantify exposure to iAs
Description:
Inorganic arsenic (iAs) is a human toxicant and carcinogen that is found in the environment as a natural contaminant and from anthropogenic sources. Most mammalian species metabolize iAs by reduction to trivalent species followed by oxidative methylation to pentavalent species. Inter- and intraindividual differences in the methylation of iAs may impact the adverse health effects of arsenic. Trivalent forms of arsenic, both inorganic and organic, are more potent toxicants than pentavalent forms. Inorganic arsenic and its methylated metabolites are primarily excreted in urine within 4-5 days by most species, and it has a relatively low rate of bioaccumulation. Several modes of action for arsenic-induced toxicity have been proposed, but a scientific consensus has not been achieved. Biomarkers of exposure may be used to quantify exposure to iAs. The most commonly used biomarker of exposure for iAs is the measurement of urinary arsenic. However, consumption of seafood containing high concentrations of organic arsenic can confound estimation of exposure to iAs. Because these organic species are thought to be relatively nontoxic, their presence in urine may not represent increased risk. Speciation of urinary arsenic, into inorganic and organic forms, and even oxidation state, gives a more definitive indication of the exposure to iAs. Questions still remain, however, as to how reliably the measurements of urinary arsenic, either total or speciated, may predict arsenic concentrations at target tissues and how this measurement could be used to assess chronic exposures to this toxicological agent.
The presence of the metalloid arsenic in the environment is from both natural and anthropogenic sources. Arsenic in the environment is commonly bound to elements such as carbon, iron, oxygen and sulfur, forming inorganic and organic arsenicals in various oxidation states. The physico-chemico properties of arsenic are important determinants of its potential toxic effect.