ATSDR TOXZINE

ARSENIC

CONTENTS

1

ARSENIC 

OVERVIEW

Arsenic is a naturally occurring element that is widely 

distributed in the Earth’s crust. 

Arsenic is classified chemically as a metalloid, having both properties of a metal 

and a nonmetal; however, it is frequently referred to as a metal. Elemental arsenic

(sometimes referred to as metallic arsenic) is a steel grey solid material. However, 

arsenic is usually found in the environment combined with other elements such 

as oxygen, chlorine, and sulfur. Arsenic combined with these elements is called 

inorganic arsenic. Arsenic combined with carbon and hydrogen is referred to as 

organic arsenic.

Most inorganic and organic arsenic compounds are white or colorless powders that 

do not evaporate. They have no smell, and most have no special taste. Thus, you 

usually cannot tell if arsenic is present in your food, water, or air.

Inorganic arsenic occurs naturally in soil and in many kinds of rock. When these ores 

are heated in smelters, most of the arsenic goes up the stack and enters the air as 

a fine dust. Smelters may collect this dust and take out the arsenic as a compound 

called arsenic trioxide (As2O3). However, arsenic is no longer produced in the 

United States; all of the arsenic used in the United States is imported.

Presently, about 90% of all arsenic produced is used as a preservative for wood to 

make it resistant to rotting, attack by termites and fungi, and decay. The preservative 

is copper chromated arsenate (CCA)—a water-soluble inorganic pesticide—and 

the treated wood is referred to as “pressure-treated.” In 2003, U.S. manufacturers 

of wood preservatives containing arsenic began a voluntary transition from CCA 

to other wood preservatives that do not contain arsenic for certain residential 

uses, such as play structures, picnic tables, decks, fencing, and boardwalks. This 

phase out was completed on December 31, 2003; however, wood treated prior to 

this date could still be used and existing structures made with CCA-treated wood 

would not be affected. CCA-treated wood products continue to be used in industrial 

applications. It is not known whether, or to what extent, CCA-treated wood products 

may contribute to exposure of people to arsenic.

In the past, inorganic arsenic compounds were predominantly used as pesticides, 

primarily on cotton fields and in orchards. Inorganic arsenic compounds can 

no longer be used in agriculture. However, organic arsenic compounds, namely 

1
cacodylic acid, disodium methylarsenate (DSMA), and 

monosodium methylarsenate (MSMA), are still used as 

pesticides, principally on cotton. Some organic arsenic 

compounds are used as additives in animal feed. Small

quantities of elemental arsenic are added to other 

metals to form metal mixtures or alloys with improved 

properties. The greatest use of arsenic in alloys is in 

lead-acid batteries for automobiles. Another important 

use of arsenic compounds is in semiconductors and 

light-emitting diodes . ◆

All of 

the arsenic 

used in the 

United States 

is imported

2
3

ARSENIC AND 

THE ENVIRONMENT 

Arsenic occurs naturally in soil and minerals and it therefore 

may enter the air, water, and land from wind-blown dust and 

may get into water from runoff and leaching.

Volcanic eruptions are another natural source of arsenic. Arsenic is associated with 

ores containing metals, such as copper and lead. Arsenic may enter the environment 

during the mining and smelting of these ores. Small amounts of arsenic also may be 

released into the atmosphere from coal-fired power plants and incinerators because 

coal and waste products often contain some arsenic.

Arsenic cannot be destroyed in the environment. It can only change its form, or 

become attached to or separated from particles. It may change its form by reacting 

with oxygen or other molecules present in air, water, or soil, or by the action of bacteria 

that live in soil or sediment. Arsenic released from power plants and other combustion 

processes is usually attached to very small particles. Arsenic contained in wind-borne 

soil is generally found in larger particles. These particles settle to the ground or are 

washed out of the air by rain. Arsenic that is attached to very small particles may stay 

in the air for many days and travel long distances. Many common arsenic compounds 

can dissolve in water. Thus, arsenic can get into lakes, rivers, or underground water 
4

by dissolving in rain or snow or through the discharge 

of industrial wastes. Some of the arsenic will stick to 

particles in the water or sediment on the bottom of lakes 

or rivers, and some will be carried along by the water.

Ultimately, most arsenic ends up in the soil or sediment.

Although some fish and shellfish take in arsenic, which 

may build up in tissues, most of this arsenic is in an 

organic form called arsenobetaine (commonly called “fish 

arsenic”) that is much less harmful.

Newly CCA-treated wood may have some pesticide 

residue left on the wood surface from the treatment 

process. Because CCA is water-soluble, rainwater can 

seep in and leach CCA onto the wood surface. The CCA 

residue can be wiped or dislodged from the wood 

surface and can stick to hands or clothing from contact 

with the wood surface. Furthermore, the soil beneath 

and adjacent to CCA-treated wood structures has been 

shown to be contaminated by arsenic, chromium, and 

copper. When decks built with CCA-treated wood was 

coated with a waterproof sealant, the soil underneath 

had lower concentrations of the metal. ◆

Arsenic may 

enter the 

environment 

during 

the mining 

and smelting 

of copper 

and lead ores.
5

EXPOSURE 

TO ARSENIC

Since arsenic is found naturally in the environment, you will 

be exposed to some arsenic by eating food, drinking water, or 

breathing air.

Children may also be exposed to arsenic by eating soil. Analytical methods used 

by scientists to determine the levels of arsenic in the environment generally do not 

determine the specific form of arsenic present. Therefore, we do not always know the 

form of arsenic a person may be exposed to. Similarly, we often do not know what 

forms of arsenic are present at hazardous waste sites. Some forms of arsenic may be 

so tightly attached to particles or embedded in minerals that they are not taken up by 

plants and animals.

The concentration of arsenic in soil varies widely, generally ranging from about 

1 to 40 parts of arsenic to a million parts of soil (ppm) with an average level of 

3–4 ppm. However, soils in the vicinity of arsenic-rich geological deposits, some 

mining and smelting sites, or agricultural areas where arsenic pesticides had been 

applied in the past may contain much higher levels of arsenic. The concentration 

of arsenic in natural surface and groundwater is generally about 1 part in a billion 

parts of water (1 ppb), but may exceed 1,000 ppb in contaminated areas or where 

arsenic levels in soil are high. Groundwater is far more likely to contain high levels of 

arsenic than surface water. Surveys of U.S. drinking water indicate that about 80% 

of water supplies have less than 2 ppb of arsenic, but 2% of supplies exceed 20 ppb 
6

of arsenic. Levels of arsenic in food range from about 

20 to 140 ppb. However, levels of inorganic arsenic, the 

form of most concern, are far lower. Levels of arsenic in 

the air generally range from less than 1 to about 2,000 

nanograms (1 nanogram equals a billionth of a gram) of 

arsenic per cubic meter of air (less than 1–2,000 ng/m3

), 

depending on location, weather conditions, and the level 

of industrial activity in the area. However, urban areas 

generally have mean arsenic levels in air ranging from 20 

to 30 ng/m3

.

 You normally take in small amounts of arsenic in the air 

you breathe, the water you drink, and the food you eat.

Of these, food is usually the largest source of arsenic.

The predominant dietary source of arsenic is seafood, 

followed by rice/rice cereal, mushrooms, and poultry.

Some seaweeds may contain arsenic in inorganic forms 

that may be more harmful. The total amount of arsenic 

you take in from these sources is generally about 50 

micrograms (1 microgram equals one-millionth of a 

gram) each day. The level of inorganic arsenic (the 

form of most concern) you take in from these sources 

is generally about 3.5 microgram/day. Children may 

be exposed to small amounts of arsenic from handto-mouth activities from playing on play structures or 

decks constructed out of CCA-treated wood; however, 

this exposure is generally smaller than that they would 

receive from food and water. Hand washing can reduce 

the potential exposure of children to arsenic after 

playing on play structures constructed with CCA-treated 

wood, since most of the arsenic on the children’s hands is 

removed with water. ◆

Potential sources 

for higher levels of 

exposure to arsenic

➤ Living in an area with high 

natural levels of arsenic in 

rock can lead to elevated 

amounts of arsenic in 

drinking water

➤ Living near hazardous 

waste sites containing large 

quantites of arsenic may lead 

to higher levels of exposure 

from water, air, or soil

➤ Occupations involving 

arsenic production or use 

(e.g. copper or lead smelting, 

wood treating, or pesticide 

application)could lead to 

higher exposure levels

➤ Inhaling sawdust from 

working with arsenic-treated 

wood or smoke from burning 

the wood

➤ Exposure to soil from 

agricultural areas where 

arsenic was used on crops

➤ Exposure to home products 

that contained arsenic (rat 

and ant poison, weed killer, 

and some types of medicines)
7

ARSENIC AND 

THE BODY 

If you are 

exposed to 

organic arsenic, 

most of it 

will leave 

your body 

within 

several days.

If you swallow arsenic in water, soil, or 

food, most of the arsenic may quickly 

enter into your body. 

The amount that enters your body will depend on 

how much you swallow and the kind of arsenic that 

you swallow. This is the most likely way for you to 

be exposed near a waste site. If you breathe air that 

contains arsenic dusts, many of the dust particles settle 

onto the lining of the lungs. Most of the arsenic in these 

particles is then taken up from the lungs into the body.

If you get arsenic-contaminated soil or water on your 

skin, only a small amount will go through your skin into 

your body, so this is usually not of concern.

Both inorganic and organic forms leave your body in 

your urine. Most of the inorganic arsenic will be gone 

within several days, although some will remain in your 

body for several months or even longer. If you are

exposed to organic arsenic, most of it will leave your 

body within several days. ◆
8

HEALTH EFFECTS

OF EXPOSURE 

Inorganic arsenic has been recognized as a human poison 

since ancient times.

Large oral doses (above 60,000 ppb in water which is 10,000 times higher than 80% 

of U.S. drinking water arsenic levels) can result in death. If you swallow lower levels 

of inorganic arsenic (ranging from about 300 to 30,000 ppb in water; 100–10,000 

times higher than most U.S. drinking water levels), you may experience irritation of 

your stomach and intestines, with symptoms such as stomachache, nausea, vomiting, 

and diarrhea. Other effects you might experience from swallowing inorganic arsenic 

include decreased production of red and white blood cells, which may cause fatigue, 

abnormal heart rhythm, blood-vessel damage resulting in bruising, and impaired 

nerve function causing a “pins and needles” sensation in your hands and feet.

Perhaps the single-most characteristic effect of long-term oral exposure to inorganic 

arsenic is a pattern of skin changes. These include patches of darkened skin and the 

appearance of small “corns” or “warts” on the palms, soles, and torso, and are often 

associated with changes in the blood vessels of the skin. Skin cancer may also develop.

Swallowing arsenic has also been reported to increase the risk of cancer in the liver, 

bladder, and lungs.

Cancer Determinations 

from Regulatory Agencies 

for Inorganic Arsenic

Department of 

Health and Human 

Services (DHHS)

Known to be a 

human carcinogen

International 

Agency for Research 

on Cancer (IARC)

Carcinogenic to 

humans

Environmental 

Protection Agency 

(EPA)

Known human 

carcinogen
9

If you breathe high levels of inorganic arsenic, then you are likely to experience a sore 

throat and irritated lungs. You may also develop some of the skin effects mentioned 

above. The exposure level that produces these effects is uncertain, but it is probably 

above 100 micrograms of arsenic per cubic meter (μg/m3) for a brief exposure. Longer 

exposure at lower concentrations can also to circulatory and peripheral nervous 

disorders. There are some data suggesting that inhalation of inorganic arsenic may also 

interfere with normal fetal development, although this is not certain. An important 

concern is the ability of inhaled inorganic arsenic to increase the risk of lung cancer.

This has been seen mostly in workers exposed to arsenic at smelters, mines, and 

chemical factories, but also in residents living near smelters and arsenical chemical 

factories. People who live near waste sites with arsenic may have an increased risk of 

lung cancer as well.

If you have direct skin contact with high concentrations of inorganic arsenic 

compounds, your skin may become irritated, with some redness and swelling.

However, it does not appear that skin contact is likely to lead to any serious 

internal effects.

Almost no information is available on the effects of organic arsenic compounds 

in humans. Studies in animals show that most simple organic arsenic compounds 

(such as methyl and dimethyl compounds) are less toxic than the inorganic forms. In 

animals, ingestion of methyl compounds can result in diarrhea, and lifetime exposure 

can damage the kidneys. Lifetime exposure to dimethyl compounds can damage the 

urinary bladder and the kidneys. ◆
10

ARSENIC 

AND CHILDREN 

Children are exposed to arsenic in many of the same ways 

that adults are. 

Since children tend to eat or drink less of a variety of foods and beverages than do 

adults, ingestion of contaminated food or juice or infant formula made with arseniccontaminated water may represent a significant source of exposure. In addition, since 

children often play in the soil and put their hands in their mouths and sometimes 

intentionally eat soil, ingestion of contaminated soil may be a more important source 

of arsenic exposure for children than for adults. In areas of the United States where 

natural levels of arsenic in the soil and water are high, or in areas in and around 

contaminated waste sites, exposure of children to arsenic through ingestion of 

soil and water may be significant. In addition, contact with adults who are wearing 

clothes contaminated with arsenic (e.g., with dust from copper- or lead-smelting 

factories, from wood-treating or pesticide application, or from arsenic-treated wood) 

could be a source of exposure. Because of the tendency of children to taste things 

that they find, accidental poisoning from ingestion of pesticides is also a possibility.

Thus, although most of the exposure pathways for children are the same as those 

for adults, children may be at a higher risk of exposure because of normal hand-tomouth activity.
11

All health 

effects 

observed in 

adults are 

of potential 

concern in 

children.

Children who are exposed to inorganic arsenic may have 

many of the same effects as adults, including irritation of 

the stomach and intestines, blood vessel damage, skin 

changes, and reduced nerve function. Thus, all health 

effects observed in adults are of potential concern in 

children. There is also some evidence that suggests that 

long-term exposure to inorganic arsenic in children may 

result in lower IQ scores. We do not know if absorption 

of inorganic arsenic from the gut in children differs from 

adults. There is some evidence that exposure to arsenic 

in early life (including gestation and early childhood) 

may increase mortality in young adults.

Young children are more at risk of exposure to CCA 

because they tend to spend more time playing outdoors, 

and because they have frequent hand-to-mouth 

activities. When playing on playground equipment 

or decks built with CCA-treated wood, they can be 

exposed to CCA by touching the CCA leachate on the 

wood surface with their hands and then inadvertently 

ingesting the CCA on their hands by hand-to-mouth 

activity.

 There is some evidence that inhaled or ingested 

inorganic arsenic can injure pregnant women or their 

unborn babies, although the studies are not definitive.

Studies in animals show that large doses of inorganic 

arsenic that cause illness in pregnant females can also 

cause low birth weight, fetal malformations, and even 

fetal death. Arsenic can cross the placenta and has been 

found in fetal tissues. Arsenic is found at low levels in 

breast milk. The dose levels that cause these effects also 

result in effects in the mothers. ◆
12

REDUCING RISK 

OF EXPOSURE 

If your doctor finds that you have been exposed to substantial 

amounts of arsenic, ask whether your children might also 

have been exposed. Your doctor might need to ask your state 

health department to investigate.

Many communities may have high levels of arsenic in their drinking water, 

particularly from private wells, because of contamination or as a result of the 

geology of the area. The north central region and the western region of the 

United States have the highest arsenic levels in surface water and groundwater 

sources, respectively. Wells used to provide water for drinking and cooking 

should be tested for arsenic. As of January 2006, EPA’s Maximum Contaminant 

Level (MCL) for arsenic in drinking water is 10 ppb. If you have arsenic in your 

drinking water at levels higher that the EPA’s MCL, an alternative source of 

water used for drinking and cooking should be considered.

If you use arsenic-treated wood in home projects, personal protection from 

exposure to arsenic-containing sawdust may be helpful in limiting exposure 

of family members. These measures may include dust masks, gloves, and 

protective clothing. Arsenic-treated wood should never be burned in 

open fires, or in stoves, residential boilers, or fire places, and should not be 

composted or used as mulch. EPA’s Consumer Awareness Program (CAP) for 

CCA is a voluntary program established by the manufacturers of CCA products 

to inform consumers about the proper handling, use, and disposal of CCAtreated wood.

If you live in an area with a high level of arsenic in the water or soil, substituting 

cleaner sources of water and limiting contact with soil (for example, through 

use of a dense groundcover or thick lawn) would reduce family exposure to 

arsenic. By paying careful attention to dust and soil control in the home (air 

filters, frequent cleaning), you can reduce family exposure to contaminated soil.

Make sure children wash their hands frequently and before eating. Discourage 

them from putting their hands in their mouths or engaging in other handto-mouth activities. Since arsenic may be found in the home as a pesticide, 

household chemicals containing arsenic should be stored out of reach of young 
13

children to prevent accidental poisonings. Always store household chemicals in 

their original labeled containers; never store household chemicals in containers that 

children would find attractive to eat or drink from, such as old soda bottles. Keep your 

Poison Control Center’s number by the phone.

It is sometimes possible to carry arsenic from work on your clothing, skin, hair, 

tools, or other objects removed from the workplace. This is particularly likely if you 

work in the fertilizer, pesticide, glass, or copper/lead smelting industries. You may 

contaminate your car, home, or other locations outside work where children might be 

exposed to arsenic. You should know about this possibility if you work with arsenic.

Material safety data sheets (MSDS) for many chemicals used should be found at your 

place of work, as required by the Occupational Safety and Health Administration 

(OSHA) in the U.S. Department of Labor. MSDS information should include chemical 

names and hazardous ingredients, and important properties, such as fire and 

explosion data, potential health effects, how you get the chemical(s) in your body, 

how to properly handle the materials, and what to do in the case of emergencies.

Your state OSHA-approved occupational safety and health program or OSHA can 

answer any further questions and help your employer identify and correct problems 

with hazardous substances. ◆

Map of Arsenic Concentrations in Groundwater of the United States 

Explanation

Arsenic concentration, 

in micrograms per liter

>50

>10 to ≤50

>5 to ≤10

>3 to ≤5

≤3

USEPA Arsenic drinking 

water standard is 

10 micrograms per liter

Source: U.S. Geological Survey. Trace Elements National Synthesis Project. Arsenic in groundwater of the United States. 

http://water.usgs.gov/nawqa/trace/arsenic/
14

EXPOSURE 

TESTING 

Several sensitive and specific tests can measure arsenic in 

your blood, urine, hair, or fingernails, and these tests are often 

helpful in determining if you have been exposed to aboveaverage levels of arsenic in the past.

These tests are not usually performed in a doctor’s office. They require sending the 

sample to a testing laboratory.

Measurement of arsenic in your urine is the most reliable means of detecting arsenic 

exposures that you experienced within the last several days. Most tests measure the 

total amount of arsenic present in your urine. This can sometimes be misleading, 

because the nonharmful forms of arsenic in fish and shellfish can give a high 

reading even if you have not been exposed to a toxic form of arsenic. For this reason, 

laboratories sometimes use a more complicated test to separate “fish arsenic” from 

other forms. Because most arsenic leaves your body within a few days, analysis of 

your urine cannot detect if you were exposed to arsenic in the past. Tests of your hair 

or fingernails can tell if you were exposed to high levels over the past 6–12 months, 

but these tests are not very useful in detecting low-level exposures. If high levels 

of arsenic are detected, this shows that you have been exposed, but unless more is 

known about when you were exposed and for how long, it is usually not possible to 

predict whether you will have any harmful health effects. ◆
15

GOVERNMENTAL 

RECOMMENDATIONS 

Recommendations and regulations are also updated 

periodically as more information becomes available. 

For the most current information, check with the federal agency or organization 

that provides it for the substance in which you are interested. Some regulations and 

recommendations for arsenic include the following: 

The federal government has taken several steps to protect humans from arsenic.

First, EPA has set limits on the amount of arsenic that industrial sources can release 

into the environment. Second, EPA has restricted or canceled many of the uses of 

arsenic in pesticides and is considering further restrictions. Third, in January 2001, 

the EPA lowered the limit for arsenic in drinking water from 50 to 10 ppb. Finally,

OSHA has established a permissible exposure limit (PEL), 8-hour time-weighted 

average, of 10 μg/m3

 for airborne arsenic in various workplaces that use inorganic 

arsenic. ◆
16

ADDITIONAL 

INFORMATION 

If you have any more questions or concerns, please contact 

your community or state health or environmental quality 

department or contact ATSDR at the address and phone 

number below. 

Agency for Toxic Substances and Disease Registry

Division of Toxicology and Human Health Sciences

1600 Clifton Road NE, Mailstop F-57

Atlanta, GA 30329-4027

Toll-free information and technical assistance:

1-800-CDCINFO (1-800-232-4636)
17
something like: A publication from the Centers for 

Disease Control and Prevention

ATSDR TOXZINE A publication of CDC/ATSDR

CS249496-A