This fact sheet answers the most frequently asked health questions about americium. For more information, you may call the ATSDR Information Center at 1-888-422-8737. This fact sheet is one in a series of summaries about hazardous substances and their health effects. 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.

Americium is a man-made radioactive chemical. Americium has no naturally occurring or stable isotopes. Two important isotopes of americium are americium 241 (²⁴¹Am) (read as americium two-forty-one) and ²⁴³Am. Both isotopes have the same chemical behavior in the environment and the same chemical effects on your body.

²⁴¹Americium is used in ionization smoke detectors. There is no broad commercial use for ²⁴³Am.

Nuclear reactors, nuclear explosions, or the radioactive transformation of plutonium can produce both ²⁴¹Am and ²⁴³Am. These isotopes transform by giving off alpha radiation and turning into radionuclides of other elements. The half-life of a radioactive material is the time it takes for half of the material to give off its radiation. The half-life of ²⁴¹Am is 432 years and that of ²⁴³Am is 7,370 years.

• Americium released to the air (from nuclear weapon tests)
  will be associated with particles and will settle to the soil
  and water in rain or snow. Small particles in air can travel far
  from the point of release.
• Americium released into water will stick to particles in the
  water or the sediment at the bottom.
• Americium strongly sticks to soil particles and does not
  travel very far into the ground.
• Plants may take up small amounts of americium from the
  soil.
• Fish may take up americium, but little builds up in the
  fleshy tissue. In shellfish, americium is attached to the shell
  and not to the parts you normally eat.

• The general population may be exposed to very small
  amounts of americium in air, water, soil, and food. They may
  also be exposed to very low levels of americium radiation
  from smoke detectors and fallout from nuclear weapons
  testing.
• People working at sites where transuranic waste from
  nuclear weapons efforts or spent nuclear fuel from nuclear
  power plants are stored may be exposed to higher levels of
  americium.
• People producing or handling americium in smoke
  detectors or other devices may be exposed to higher levels
  of radiation.

The radiation from exposure to americium is the primary
cause of adverse health effects from americium. Inside your
body, americium is concentrated in your bones, where it
remains for a long time. The radiation given off by americium can change the genetic material of the bone cells and this could result in the formation of bone cancers. The chance of getting cancer is low at low doses, and increases as the dose increases.

Laboratory animals exposed to very high levels of americium had damage to the lungs, liver, and thyroid. However, americium is accumulated in these organs for only a relatively short time. It is unlikely that you would be exposed to amounts of americium large enough to cause harmful effects in these organs.

Americium has not been found to cause cancer in humans. However, studies in animals have demonstrated that internal exposure to ²⁴¹Am can cause cancer in bone and liver, where americium is stored.

Children can be affected by americium in the same ways as adults. However, exposure as children could result in a longer period in which americium in the bones could affect nearby cells and increase the chance of causing cancer later in life. However, there are no actual data showing that children are more sensitive than adults to americium.

Higher-than-normal levels of americium may be in soil near a nuclear waste site, nuclear reactor, or plant that manufactures ionization smoke detectors. Consequently, prevent your children from eating dirt and make sure they wash their hands frequently.

In the unlikely case that you are exposed to high levels of radioactive americium because of accidental release at a manufacturing facility, at a nuclear plant, or because a nuclear weapon has been damaged or detonated, follow the advice of public health officials who will publish appropriate guidelines for reducing exposure.

Two types of tests are available for americium. One is to see if you have been exposed to a large dose of radiation, and the other is to see if americium is in your body. The first looks for changes in blood cell counts or in your chromosomes that occur at 3 to 5 times the annual occupational dose limit. It cannot tell if the radiation came from americium. The second type of test involves examining your blood, feces, saliva, urine, and even your entire body. It is to see if americium is being excreted from or remains inside your body. Either the doctor’s office collects and sends the samples to a special lab for testing, or you must go to the lab for testing.

The Nuclear Regulatory Commission (NRC) has set limits for americium in workplace air of 3 x 10^-12 microcurie per milliliter (µCi/mL) for ²⁴¹Am and ²⁴³Am. EPA set an average annual drinking water limit of 15 picocurie of alpha-emitting radionuclides (such as americium) per liter (pCi/L) so the public radiation dose will not exceed 4 millirem.

Agency for Toxic Substances and Disease Registry (ATSDR). 2004. Toxicological Profile for americium. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.

ATSDR can tell you where to find occupational and environmental health clinics. Their specialists can recognize, evaluate, and treat illnesses resulting from exposure to hazardous substances. You can also contact your community or state health or environmental quality department if you have any more questions or concerns.

For more information, contact:

Agency for Toxic Substances and Disease Registry
Division of Toxicology
1600 Clifton Road NE, Mailstop F-32
Atlanta, GA 30333
Phone: 1-888-42-ATSDR (1-888-422-8737)
FAX:   (770)-488-4178
Email: ATSDRIC@cdc.gov