Plutonium in gonads: a summary of the current status

Area of Science:

• Radiological health
• Human toxicology
• Radiation biology

Background:

• Plutonium (Pu) distribution in human gonads is crucial for assessing genetic radiation dose.
• Understanding the need for localization factors and relative biological effectiveness (RBE) of Pu alpha particles is essential for accurate risk assessment.

Purpose of the Study:

• To determine the fraction of plutonium in human gonads.
• To evaluate the necessity of a localization factor for human genetic dose calculations.
• To assess the RBE of alpha particles from plutonium for genetic effects.

Main Methods:

• Literature review of human autopsy data from occupationally exposed individuals and the general public.
• Analysis of plutonium distribution within ovaries and testes.
• Evaluation of existing data on RBE for genetic effects of alpha particles.

Main Results:

• An average of 3 x 10^-3 (0.3%) of the body's plutonium burden was found in human ovaries and testes, with significant inter-individual variability.
• A specific localization factor, unlike that required for rodents, is not necessary for calculating the genetic dose to sensitive cells in humans.
• The RBE for plutonium alpha particles causing genetic effects aligns with expectations for neutron irradiation, suggesting current quality factors are appropriate.

Conclusions:

• Plutonium deposition in human gonads is minimal, simplifying genetic dose estimations.
• The absence of a required localization factor for humans streamlines dose calculations for internal plutonium exposure.
• Established quality factors for radiation protection are likely adequate, possibly conservative, for plutonium alpha particle exposure, especially in females.