Estimation of dietary ¹⁴C dose coefficient using ¹³C-labelled compound administration analysis

Area of Science:

• Environmental Science
• Radiological Protection
• Human Metabolism

Background:

• Carbon-14 (¹⁴C) from nuclear facilities contributes to public radiation dose via the food chain.
• Current International Commission on Radiological Protection (ICRP) dose coefficients for ¹⁴C are not based on human metabolic data.
• Accurate dose assessment requires understanding ¹⁴C metabolism in human nutrients and diet.

Purpose of the Study:

• To validate the ICRP's dose coefficient for ingested ¹⁴C using experimental human metabolic data.
• To investigate the human metabolism of ¹⁴C incorporated into essential nutrients.
• To refine radiation dose estimations for the public from dietary ¹⁴C exposure.

Main Methods:

• Administered stable ¹³C-labeled nutrients (amino acids, fatty acids, monosaccharide) to volunteers.
• Measured ¹³C concentrations in excreta samples to track metabolic fate.
• Constructed metabolic models based on excretion data and estimated unrecovered ¹³C fractions.

Main Results:

• Significant fractions of administered ¹³C were unrecovered for certain nutrients, indicating complex metabolism.
• Estimated ¹⁴C dose coefficients for a Japanese diet varied from 6.2 × 10⁻¹¹ to 8.9 × 10⁻¹⁰ Sv Bq⁻¹.
• Calculated dose coefficients were comparable to the ICRP's recommended value of 5.8 × 10⁻¹⁰ Sv Bq⁻¹.

Conclusions:

• Experimental data suggest current ¹⁴C dose coefficients are approximately appropriate, but require refinement.
• Further research is needed to elucidate ¹⁴C metabolism in the unrecovered fraction of nutrients.
• Improved understanding of ¹⁴C metabolism will enhance public radiation dose assessments from nuclear facilities.