Arsenic

The text on this page is taken from an equivalent page of the IEHIAS-project.

Arsenic is a metalloid which is widespread through the earth’s crust. Arsenic occurs naturally in rocks and can be released through erosion, particularly in water, but it can also be released through human activity (e.g. burning of fuels, production of metal, through agriculture and waste, and through cigarette smoke). Inorganic As is more toxic than organic.

Arsenic as a biomarker

Sample collection and storage

Matrix:

• Inorganic As and its metabolites (DMA, MMA) in urine are good markers for recent or chronic exposure
• Finger nails or hair may be used to detect chronic exposure
• Blood As is only useful for high-level exposure

Kinetics:

• The principal way of exposure is through ingestion, with rapid and extensive absorption in the gastrointestinal tract
• As in inhaled airborne particles is well absorbed in the lungs
• As is rapidly cleared from the blood, and distributed among liver, kidney, lungs, nails, hair, bones
• As is mainly excreted via the kidneys, secondary routes are hair, nails, sweat and feces
• 45-75% of the dose is excreted within a few days to a week. Half life of elimination is about 40-72 h.

Sampling conditions:

• Blood and urine can be samples using standard protocols
• Freezing at -80°C is recommended

Sample measurement

Analytical aspects:

• Total As can be measured using AAS or ICP-MS
• Speciation of arsenic is effective to differentiate between inorganic and organic As, and between tri and pentavalent As.
• For speciation, various types of chromatography or chelation-extraction techniques are combined with AAS, ICP-AES or ICP-MS methods
• Sensitivity is about 0.5-1 µg/l for total As

Performance characteristics:

• Analytical reproducibility is 3-15 % for total As
• Inter- and intralaboratory variability is around 5-30%

Validation:

International intercomparison programs and certified standards/reference materials are available

Confounding factors:

• Diuresis has to be taken into account for urinary arsenic
• Other confounding factors are: age, sex, smoking behavior, food preference, area of living,…

Data interpretation

Concentrations reported in literature:

• Normal concentrations range from 0.08-0.25 µg/g hair and 0.34 µg/g nail - The normal range of As in urine can be 5-40 µg/day
• Concentrations of the sum inorganic As + metabolites (MMA + DMA) are generally < 10µg/g creatinin and most of concentrations are < 15 µg/g creatinin (German reference value: 15 µg/L)

Dose-response/effect relationships:

• Inorganic As is a carcinogen classified in group 1 by IARC
• Increased As doses may lead to increased risk of dermal lesions, skin cancer, neurological, haematologic, cardiovascular, hepatic, endocrine, developmental and reproductive effects
• Reference values: oral cancer slope factor is 1.5 (mg/kg/day)^-1 and RfD and MRL of 3.10^-4 mg/kg/day for non-carcinogenic effects for chronic exposure by oral way

Time trend, geographical variation, susceptibel groups:

Some areas in the world have naturally high levels of inorganic As in water