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PUBLIC HEALTH STATEMENT 

Cesium 

CAS#: 7440-46-2 

Division of Toxicology April 2004 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for cesium. It 

is one in a series of Public Health Statements about 

hazardous substances and their health effects. A 

shorter version, the ToxFAQsTM, is also available. 

This information is important because this 

substance may harm you. The effects of exposure to 

any hazardous substance depend on the dose, the 

duration, how you are exposed, personal traits and 

habits, and whether other chemicals are present. For 

more information, call the ATSDR Information 

Center at 1-888-422-8737. 

This public health statement tells you about cesium 

and the effects of exposure. 

The Environmental Protection Agency (EPA) 

identifies the most serious hazardous waste sites in 

the nation. These sites make up the National 

Priorities List (NPL) and are the sites targeted for 

long-term federal cleanup activities. Stable (not 

radioactive) cesium (133Cs) has been identified in at 

least 8 of the 1,636 hazardous waste sites that have 

been proposed for inclusion on the EPA National 

Priorities List (NPL) (HazDat 2003). It was 

reported that 134Cs (radioactive) has been found in 

at least 3 of the 1,636 current or former NPL sites 

and 137Cs (radioactive) has been detected in at least 

23 of the 1,636 current or former NPL sites. 

However, the number of sites evaluated for cesium 

is not known. As more sites are evaluated, the sites 

at which cesium is found may increase. This 

information is important because exposure to this 

substance may harm you and because these sites 

may be sources of exposure. 

When a substance is released from a large area, 

such as an industrial plant, or from a container, such 

as a drum or bottle, it enters the environment. This 

release does not always lead to exposure. You are 

exposed to a substance when you come in contact 

with it. You may be exposed by breathing, eating, 

or drinking the substance, or by skin contact. If the 

substance is radioactive, you may also be exposed 

to radiation if you are near it. 

External exposure to radiation may occur from 

natural or man-made sources. Naturally occurring 

sources of radiation are cosmic radiation from space 

or radioactive materials in soil or building materials. 

Man-made sources of radioactive materials are 

found in consumer products, industrial equipment, 

atom bomb fallout, and to a smaller extent from 

hospital waste, medical devices, and nuclear 

reactors. 

If you are exposed to cesium, many factors 

determine whether you’ll be harmed. These factors 

include the dose (how much), the duration (how 

long), and how you come in contact with it. You 

must also consider the other chemicals you’re 

exposed to and your age, sex, diet, family traits, 

lifestyle, and state of health. 

1.1 WHAT IS CESIUM? 

Cesium is a naturally-occurring element found in 

rocks, soil, and dust at low concentrations. Granites 

contain an average cesium concentration of about 

1 part of cesium in a million parts of granite (ppm) 

and sedimentary rocks contain about 4 ppm. 

Natural cesium is present in the environment in only 

one stable form, as the isotope 133Cs. Pure cesium 

metal is silvery white in color and very soft, but 

pure cesium is not expected to be found in the 

environment. Pure cesium metal reacts violently 

with air and water, resulting in an explosion-like 

reaction. Cesium compounds do not react violently 

with air or water and are generally very soluble in 

water. The most important source of commercial 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Cesium 

CAS#: 7440-46-2 

Division of Toxicology April 2004 

cesium is a mineral known as pollucite, which 

usually contains about 5–32% cesium oxide (Cs2O). 

No known taste or odor is associated with cesium 

compounds. Cesium is not mined or produced in 

the United States and very little is imported from 

other countries. There are relatively few 

commercial uses for cesium metal and its 

compounds. Sometimes cesium is used as a getter 

for residual gas impurities in vacuum tubes and as a 

coating in tungsten filaments or cathodes of the 

tubes. Crystalline cesium iodide and cesium 

fluoride are used in scintillation counters, which 

convert energy from ionizing radiation into pulses 

of visible light for radiation detection and 

spectroscopy. Cesium is also used in highly 

accurate atomic clocks. 

Radioactive forms of cesium are produced by the 

fission of uranium in fuel elements (fuel rods) 

during the normal operation of nuclear power 

plants, or when nuclear weapons are exploded. 

Radioactive forms of cesium are unstable and 

eventually change into other more stable elements 

through the process of radioactive decay. The two 

most important radioactive isotopes of cesium are 

134Cs and 137Cs. Radioactive isotopes are constantly 

decaying or changing into different isotopes by 

giving off radiation. Each atom of 134Cs changes 

into either xenon 134 (134Xe) or barium 134 (134Ba), 

neither of which is radioactive, while each atom of 

137Cs decays to barium 137 (137Ba), which is also 

not radioactive. As 134Cs and 137Cs decay, beta 

particles and gamma radiation are given off. The 

half-life is the time it takes for half of that cesium 

isotope to give off its radiation and change into a 

different element. The half-life of 134Cs is about 

2 years and the half-life of 137Cs is about 30 years. 

Quantities of radioactive cesium, as well as other 

radioactive elements, are measured in units of mass 

(grams) or radioactivity (curies or becquerels). 

Both the curie (Ci) and the becquerel (Bq) describe 

the rate of decay and tell us how much a radioactive 

material decays every second. The becquerel is a 

new international unit known as the SI unit, and the 

curie is an older, traditional unit; both are currently 

used. A becquerel is the amount of radioactive 

material in which 1 atom transforms every second. 

One curie is the amount of radioactive material in 

which 37 billion atoms transform every second; this 

is approximately equivalent to the radioactivity of 

1 gram of radium. 

1.2 WHAT HAPPENS TO CESIUM WHEN 

IT ENTERS THE ENVIRONMENT? 

Naturally-occurring cesium occurs in the 

environment mostly from the erosion and 

weathering of rocks and minerals. The mining and 

milling of certain ores can also release cesium to the 

air, water, and soil. Radioactive cesium is released 

to the environment during the normal operation of 

nuclear power plants, explosion of nuclear weapons, 

and accidents involving nuclear power plants or 

nuclear powered satellites or submarines. 

Nonradioactive (stable) cesium can be neither 

created nor destroyed under typical environmental 

conditions, but can react with other compounds 

found in the environment and change into different 

cesium compounds. Radioactive decay decreases 

the concentration of 134Cs and 137Cs. Both stable 

and radioactive cesium are the same element and 

behave in a similar manner chemically and in the 

body. Cesium compounds can travel long distances 

in the air before being brought back to the earth by 

rainfall and gravitational settling. In water and 

moist soils, most cesium compounds are very 

soluble. Cesium binds strongly to most soils and 

does not travel far below the surface of the soil. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Cesium 

CAS#: 7440-46-2 

Division of Toxicology April 2004 

Consequently, cesium is not readily available for 

uptake by vegetation through roots. However, 

radiocesium can enter plants upon falling onto the 

surface of leaves. 

1.3 HOW MIGHT I BE EXPOSED TO 

CESIUM? 

You can be exposed to stable or radioactive cesium 

by breathing air, drinking water, or eating food 

containing cesium. The level of cesium in air and 

water is generally very low. The concentration of 

natural cesium in air is generally less than 

1 nanogram (1 nanogram equals 1/1,000,000,000 of 

a gram) per cubic meter of air (ng/m3

). The amount 

of cesium in drinking water is ordinarily about 

1 microgram (1 microgram equals 1/1,000,000 of a 

gram) per liter of water (μg/L). On average, a 

person swallows about 10 μg of stable cesium per 

day in food and water, and breathes about 0.025 μg 

per day. Plants and animals contain cesium at 

concentrations of about 1–300 ng/g. 

Radioactive cesium has been detected in surface 

water and in many types of food. This includes 

breast milk and pasteurized milk. The amount of 

radioactive cesium in food and milk is highly 

dependent upon several factors. The most 

important factor is whether or not there has been 

recent fallout from a nuclear explosion such as a 

weapons test or an accident that has occurred at a 

nuclear power plant. However, atmospheric testing 

of nuclear weapons was halted many years ago, and 

there have only been two major reactor accidents at 

nuclear plants where radiocesium was released in 

significant amounts. The two accidents occurred in 

Windscale, England in 1957 and Chernobyl, Russia 

in 1986. You should understand that cesium only 

contributed a small fraction of the total radioactivity 

released following these events. The radiological 

impacts in Europe from 137Cs and 134Cs released 

from the Chernobyl accident, however, were great. 

These included environmental dispersion of 

radiocesium and uptake in reindeer, caribou, and 

livestock. Furthermore, the consequences of 

external exposure to gamma radiation and beta 

particles are not unique to 137Cs and 134Cs, but are 

very similar for all gamma and beta emitting 

radionuclides. People who work in industries that 

process or use natural cesium or cesium compounds 

can be exposed to higher-than-normal levels of 

cesium. An estimated 16,461 workers (4,276 of 

these are female) are potentially exposed to natural 

cesium and cesium compounds in the United States. 

If you work in the nuclear power industry, you may 

also be exposed to higher-than-normal levels of 

radioactive cesium, but there are many 

precautionary measures taken at these facilities to 

minimize this exposure. 

1.4 HOW CAN CESIUM ENTER AND 

LEAVE MY BODY? 

Stable and radioactive cesium can enter your body 

from the food you eat or the water you drink, from 

the air you breathe, or from contact with your skin. 

When you eat, drink, breathe, or touch things 

containing cesium compounds that can easily be 

dissolved in water, cesium enters your blood and is 

carried to all parts of your body. Cesium is like 

potassium; it enters cells and helps to maintain a 

balance of electrical charges between the inside and 

the outside of cells so that cells can perform tasks 

that depend on those electrical charges. Cells like 

muscle cells and nerve cells require changing 

electrical charges in order to function properly and 

allow you to think and move. 

Once cesium enters your body, your kidneys begin 

to remove it from the blood; some cesium is quickly 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Cesium 

CAS#: 7440-46-2 

Division of Toxicology April 2004 

released from your body in the urine. A small 

portion is also released in the feces. Some of the 

cesium that your body absorbs can remain in your 

body for weeks or months, but is slowly eliminated 

from your body through the urine and feces. 

1.5 HOW CAN CESIUM AFFECT MY 

HEALTH? 

To protect the public from the harmful effects of 

toxic chemicals and to find ways to treat people 

who have been harmed, scientists use many tests. 

One way to see if a chemical will hurt people is to 

learn how the chemical is absorbed, used, and 

released by the body. In the case of a radioactive 

chemical, it is also important to gather information 

concerning the radiation dose and dose rate to the 

body. For some chemicals, animal testing may be 

necessary. Animal testing may also be used to 

identify health effects such as cancer or birth 

defects. Without laboratory animals, scientists 

would lose a basic method to get information 

needed to make wise decisions to protect public 

health. Scientists have the responsibility to treat 

research animals with care and compassion. Laws 

today protect the welfare of research animals, and 

scientists must comply with strict animal care 

guidelines. 

You are not likely to experience any health effects 

that could be related to stable cesium itself. 

Animals given very large doses of cesium 

compounds have shown changes in behavior, such 

as increased activity or decreased activity, but it is 

highly unlikely that you would breathe, eat, or drink 

amounts of stable cesium large enough to cause 

similar effects. If you were to breathe, eat, drink, 

touch, or come close to large amounts of radioactive 

cesium, cells in your body could become damaged 

from the radiation that might penetrate your entire 

body, much like x-rays, even if you did not touch 

the radioactive cesium. You would probably 

experience similar effects if you were exposed to 

any other substance with similar radioactivity. You 

might also experience acute radiation syndrome, 

which includes such effects as nausea, vomiting, 

diarrhea, bleeding, coma, and even death. A 

number of people in Brazil, who handled 

radioactive cesium that was scavenged from a 

medical machine used for radiation therapy, became 

sick from exposure to the radiation; a few of them 

died. But people exposed to radioactive cesium that 

has been widely dispersed in air, water, soil, or 

foods following nuclear bombings or accidents have 

not been exposed to amounts large enough to cause 

the same effects. 

1.6 HOW CAN CESIUM AFFECT 

CHILDREN? 

This section discusses potential health effects from 

exposures during the period from conception to 

maturity at 18 years of age in humans. 

Children can be affected by cesium in the same 

ways as adults. Stable cesium is not likely to affect 

the health of children, but large amounts of gamma 

radiation, from sources such as radioactive cesium, 

could damage cells and might also cause cancer. 

Short exposure to extremely large amounts of 

radiation might cause nausea, vomiting, diarrhea, 

bleeding, coma, and even death. In addition, if 

babies were to be exposed to enough radiation while 

in their mother’s womb during the time when their 

nervous system is rapidly developing, they could 

experience changes in their brains that could result 

in changes in behavior or decreased mental abilities. 

However, it is unlikely that children or babies 

would be exposed to enough gamma radiation from 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Cesium 

CAS#: 7440-46-2 

Division of Toxicology April 2004 

a radioactive cesium source to do such damage to 

their bodies. 

1.7 HOW CAN FAMILIES REDUCE THE 

RISK OF EXPOSURE TO CESIUM? 

If your doctor finds that you have been exposed to 

significant amounts of cesium, ask whether your 

children might also be exposed. Your doctor might 

need to ask your state health department to 

investigate. 

Since cesium is naturally found in the environment, 

we cannot avoid being exposed to it. However, the 

relatively low concentrations of stable cesium do 

not warrant any immediate steps to reduce 

exposure. You are unlikely to be exposed to high 

levels of radioactive cesium unless there is a fuel 

meltdown and accidental release at a nuclear power 

plant or a nuclear weapon has been detonated. In 

such cases, follow the advice of public health 

officials who will publish guidelines for reducing 

exposure to radioactive material when necessary. 

1.8 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE 

BEEN EXPOSED TO CESIUM? 

Everyone has small amounts of cesium in their 

body. Laboratories use special techniques to 

measure the amount of cesium in body fluids such 

as blood and urine, as well as in feces or other 

human samples. This can give an indication of 

whether a person has been exposed to levels of 

cesium that are higher than those normally found in 

food, water, or air. Special radiation detectors can 

be used to detect if a person has absorbed 

radioactive cesium. It is difficult to determine if a 

person has been exposed only to external radiation 

from radioactive cesium. Health professionals 

examining people who have health problems similar 

to those resulting from radiation exposure would 

need to rely on additional information, such as the 

testing of blood samples for cell counts and 

chromosomal damage, in order to establish if such 

people had been affected by being near a source of 

radioactivity. 

1.9 WHAT RECOMMENDATIONS HAS 

THE FEDERAL GOVERNMENT 

MADE TO PROTECT HUMAN 

HEALTH? 

The federal government develops regulations and 

recommendations to protect public health. 

Regulations can be enforced by law. Federal 

agencies that develop regulations for toxic 

substances include the Environmental Protection 

Agency (EPA), the Occupational Safety and Health 

Administration (OSHA), the Food and Drug 

Administration (FDA), and the U.S. Nuclear 

Regulatory Commission (USNRC). 

Recommendations provide valuable guidelines to 

protect public health but cannot be enforced by law. 

Federal organizations that develop 

recommendations for toxic substances include the 

Agency for Toxic Substances and Disease Registry 

(ATSDR), the National Institute for Occupational 

Safety and Health (NIOSH), and the FDA. 

Regulations and recommendations can be expressed 

in not-to-exceed levels in air, water, soil, or food 

that are usually based on levels that affect animals; 

they are then adjusted to help protect people. 

Sometimes these not-to-exceed levels differ among 

federal organizations because of different exposure 

times (an 8-hour workday or a 24-hour day), the use 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Cesium 

CAS#: 7440-46-2 

Division of Toxicology April 2004 

of different animal studies, or other factors. 

Recommendations and regulations are also 

periodically updated as more information becomes 

available. For the most current information, check 

with the federal agency or organization that 

provides it. Some regulations and 

recommendations for cesium include the following: 

There are few guidelines for compounds of stable 

cesium. Based on eye irritation, the NIOSH has 

established a recommended exposure limit (REL) 

for cesium hydroxide of 2 mg/m3 as a timeweighted average (TWA) for up to a 10-hour 

workday and a 40-hour workweek. The American 

Conference of Governmental Industrial Hygienists 

(ACGIH) has assigned cesium hydroxide a 

threshold limit value (TLV) of 2 mg/m3 as a TWA 

for a normal 8-hour workday and a 40-hour 

workweek, based on respiratory and eye irritation. 

The NRC established guidelines for radioactive 

cesium that include occupational inhalation 

exposure Derived Air Concentrations (DACs) of 

0.00000004 μCi/mL (4x10-8 μCi/mL) for 134Cs and 

0.00000006 μCi/mL (6x10-8 μCi/mL) for 137Cs. 

Annual Limits on Intake (ALIs) for on-the-job 

exposure are 100 μCi (1x102

 μCi) for 134Cs and 

200 μCi (2x102

 μCi) for 137Cs. 

1.10 WHERE CAN I GET MORE 

INFORMATION? 

If you have any more questions or concerns, please 

contact your community or state health or 

environmental quality department, your regional 

Nuclear Regulatory Commission office, or contact 

ATSDR at the address and phone number below. 

ATSDR can also tell you the location of 

occupational and environmental health clinics. 

These clinics specialize in recognizing, evaluating, 

and treating illnesses resulting from exposure to 

hazardous substances. 

Toxicological profiles are also available on-line at 

www.atsdr.cdc.gov and on CD-ROM. You may 

request a copy of the ATSDR ToxProfiles 

CD-ROM by calling the information and technical 

assistance toll-free number at 1-888-42ATSDR 

(1-888-422-8737), by email at atsdric@cdc.gov, or 

by writing to: 

Agency for Toxic Substances and Disease Registry 

 Division of Toxicology 

1600 Clifton Road NE 

 Mailstop F-32 

 Atlanta, GA 30333 

 Fax: 1-770-488-4178 

For-profit organizations may request a copy of final 

profiles from the following: 

National Technical Information Service (NTIS) 

5285 Port Royal Road 

Springfield, VA 22161 

Phone: 1-800-553-6847 or 1-703-605-6000 

Web site: http://www.ntis.gov/ 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov