General Populations  The general population may be exposed 

to arsenic in air, drinking water, and food. Of these, food is usually the largest source of arsenic. 

 Some areas of the United States contain 

unusually high natural levels of arsenic in rock; this can lead to unusually high levels of arsenic in soil or water. 

 Prior to 2003, arsenic was used in the 

production of wood preservatives, primarily copper chromated arsenate (CCA); arsenical wood preservatives have been phased out for certain wood products. Sawing or sanding wood treated with arsenical preservatives can generate arsenic contaminated sawdust. Similarly, burning arsenic-treated wood can result in elevated arsenic levels in smoke.

 Various organic arsenicals are used as 

herbicides and as antimicrobial additives for animal and poultry feed. 

Occupational Populations  Some occupations in which exposure to 

arsenic may occur include copper or lead smelting and wood treatment. 

 Workers involved in the production or 

application of pesticides containing organic arsenicals may also be exposed to higher levels. 

Toxicokinetics  Both arsenate and arsenite are well 

absorbed by both the oral and inhalation routes. Absorption by the dermal route has not been well characterized, but is low compared to other routes. 

 Once absorbed, arsenates are partially 

reduced to arsenites, yielding a mixture of

As(III) and As(V) in the blood. 

 As(III) undergoes methylation primarily 

in the liver to form monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). The rate and relative proportion of methylation production varies among species. 

 Most inorganic arsenic is promptly 

excreted in the urine as a mixture of As(III), As(V), MMA, and DMA. Smaller amounts are excreted in feces. 

 In most species, including humans, 

ingested organic arsenical compounds such as MMA and DMA, undergo limited metabolism, do not readily enter the cell, and are primarily excreted unchanged in the urine. 

Normal Human Levels Levels of arsenic in unexposed individuals:

< 1 μg/L in blood 

<100 μg/L in urine ≤ 1 ppm in nails ≤ 1 ppm in hair 

Biomarkers  Measurement of urinary arsenic levels is 

generally accepted as the most reliable indicator of recent arsenic exposure. 

Environmental Levels Air 1-3 ng/m3 in remote locations.  20-100 ng/m3 in urban areas. Sediment and Soil  Mean and range of arsenic in soil and 

other surficial materials in the U.S. are 7.2 and <0.1–97 μg/g, respectively. 

Water 

 Drinking water generally contains an 

average of 2 μg/L of arsenic, although higher levels have been measured in some parts of the U.S. 

 Arsenic levels ranging from 0.138 to 

1,700 μg/L have been measured in surface water in the U.S. 

Reference Agency for Toxic Substances and Disease 

Registry (ATSDR). 2007. Toxicological Profile for Arsenic. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Services.

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Toxicokinetics and

Normal Human Levels 

Biomarkers/Environmental

Levels Sources of Exposure 

The ToxGuideTM is developed to be used as a pocket guide. Tear off at perforation and fold along lines.
The ToxGuideTM is developed to be used as a pocket guide. Tear off at perforation and fold along lines.

Chemical and Physical 

Information Routes of Exposure Relevance to Public Health 

Health effects are determined 

by the dose (how much), the 

duration (how long), and the 

route of exposure.

 Inhalation – Minor route of exposure for 

the general population. Predominant route for occupational exposure. 

 Oral – Predominant route of exposure 

for the general population; for most individuals diet is the largest source of arsenic exposure. Ingestion of arsenic in dirt through hand-to-mouth activity may be an important route of exposure for young children. 

 Dermal – Minor route of exposure. Arsenic in the Environment Arsenic cannot be destroyed in the 

environment. It can only change its form or become attached to or separated from particles. 

 Arsenic attached to very small particles 

may stay in the air for many days and travel long distances. 

 Arsenic in soil may be transported by 

wind or in runoff or may leach into the subsurface soil. Arsenic is largely immobile in agricultural soils, therefore, it tends to concentrate and remain in upper soil layers indefinitely. 

 Transport and partitioning of arsenic in 

water depends upon the chemical form. Soluble forms move with the water and may be carried long distances. Arsenic may be adsorbed from water onto sediments or soils. 

Arsenic is a metalloid Arsenic is ordinarily a steel gray metallike material that occurs naturally.  Arsenic compounds can be categorized 

as inorganic or organic. 

 Inorganic arsenic is primarily used as a 

preservative for wood to make it resistant to rotting and decay. In 2003, the use of arsenic-containing wood preservatives was phased out for certain residential uses such as play structures, picnic tables, decks, fencing, and boardwalks. Arsenic wood preservatives are still used in industrial applications. 

 Inorganic arsenic occurs naturally in soil 

and in many kinds of rock, especially in minerals and ores that contain copper or lead. 

 Elemental arsenic is used as an alloying 

element in ammunition and solders, as an anti-friction additive to metals used for bearings, and to strengthen lead-acid storage battery grids. 

 In the past, inorganic arsenic compounds 

were used as pesticides; this use is no longer permitted. 

 MMA is used for weed control on cotton,

turf grass and lawns and under trees, vines, and shrubs. DMA, also referred to as cacodylic acid, is used for weed control under nonbearing citrus trees, around buildings and sidewalks, and for lawn renovation. 

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Minimal Risk Levels (MRLs)

Inhalation 

 No acute-, intermediate- or chronicduration inhalation MRLs were derived 

for inorganic arsenic or organic arsenic compounds.

Oral 

 An MRL of 0.005 mg As/kg/day has 

been derived for acute-duration oral exposure (

≤14 days) to inorganic arsenic.

 No intermediate-duration oral MRL was 

derived for inorganic arsenic. 

 An MRL of 0.0003 mg As/kg/day has 

been derived for chronic-duration oral exposure (

≥1 year) to inorganic arsenic. 

 No acute-duration oral MRL was derived 

for monomethylarsonic acid (MMA).

 An MRL of 0.1 mg MMA/kg/day has 

been derived for intermediate-duration oral exposure (15-364 days) to MMA.

 An MRL of 0.01 mg MMA/kg/day has 

been derived for chronic-duration oral exposure (

≥1 year) to MMA.

No acute- or intermediate duration oral MRLs were d



erived for dimethylarsinic 



tion oral 

ex

acid (DMA).An MRL of 0.02 mg DMA/kg/day has been derived for chronic-dura

posure (≥1 year) to DMA.