Fat Cells in Red Bone Marrow of Human Rib: Their Size and Spatial Distribution with Respect to the Radon-derived Dose to the Haemopoietic Tissue

Samples of human rib were collected at autopsy and 20 were selected for marrow fat cell measurement, representing an age range of 16-96 years. The mean diameter of fat cells in red bone marrow of human rib was found to increase from around 48 µm at ages 16-29 years to around 65 µm at ages 82-96 years. There was a greater number of fat cells of smaller size range in younger ages compared with that in older ones. The maximum size of fat cells was found to be 102 µm. Calculated radon-derived doses to haemopoietic tissue ranged from 60 to 162 µSv y−1 at average UK exposures of 20 Bq m−3. It was concluded that the bone marrow fat fraction is the important parameter as far as α-radiation dose from radon in fat is concerned. This updates the theoretical estimates of dose carried out by Richardson et al. (1991).