Annual Limits on Intake (ALI)

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    If a radionuclide becomes internalized it can cause significant exposure to certain tissues and organ systems.
    In most scenarios the main mode of entry is either inhalation or ingestion.
    Studies and research over many years have established intake limits for many forms of radionuclides.
    These standards are based on inhalation or ingestion of materials by standard man under normal circumstances. Since every person is different and most accidental ingestion or inhalation usually causes stress and concern, the actual exposure a person receives may be different.
    These are known as the Annual Limit on Intake (ALI) which is the derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. The ALI is the smaller value of intake of a given radionuclide in a year that would result in a committed effective dose equivalent (CEDE) of 5 rem (0.05 Sv) or a committed dose equivalent of 50 rem (0.5 Sv) to any individual organ or tissue.
    The following are some of the more common research isotopes used along with the target organ and amount required to reach ALI.

Radionuclide (uCi)
Intake
Target Organ
ALI
S-35 Ingestion 10 mCi
I-125 Inhalation Thyroid 40 uCi
I-131 Inhalation Thyroid 30 uCi
P-32 Ingestion Bone 600 uCi
C-14 Ingestion Whole Body 2.0 mCi
P-33 Ingestion Bone 6 mCi
H-3 Inhalation Whole Body 80 mCi


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