title: Monte Carlo determination of age-dependent steady-state dose to red bone marrow and bone from 14C exposure.
abstract: Monte Carlo simulations were carried out to calculate the age-dependent dose from the beta decay of 14C to marrow and bone on the basis of a steady-state specific-activity model. A model of the trabecular cavity containing spherical fat cells in a square lattice surrounded by haemopoietic tissue was employed. The age-dependent 14C dose to haemopoietic (red) marrow was estimated taking account of the change in the fat cell size with fat fraction. Allowances were made for the change in the percentage cellularity and distribution of active marrow in the whole skeleton as a function of age. Age-dependent changes in trabecular cavity size and bone composition were found to have only a small effect on dose. Dose rates were estimated under steady-state conditions, for food ingested with a 14C specific activity of 1 Bq g(-1) of C. The equivalent dose rate to the haemopoietic tissue of a 20 year-old adult is 77 microSv a(-1), and 39 microSv a(-1) for a 3-month-old infant. Similarly, the equivalent dose rate to the bone surfaces of an adult is 48 microSv a(-1), and 38 microSv a(-1) for an infant. Therefore, the equivalent dose rate to marrow and bone stem cells increases with age under steady state conditions.
authors.affiliation: Health, Chemistry and Environment Division AECL, Chalk River Laboratories Chalk River, ON, Canada K0J 1J0. richard@aecl.com
authors.forename: R B
authors.initials: RB
authors.lastname: Richardson
authors.forename: J
authors.initials: J
authors.lastname: Dubeau
mesh_terms: D017667:Adipocytes / Q000528:radiation effects; D000293:Adolescent; D000328:Adult; D000375:Aging; D000886:Anthropometry; D001610:Beta Particles; D001853:Bone Marrow / Q000254:growth & development / Q000528:radiation effects*; D001842:Bone and Bones / Q000528:radiation effects; D002250:Carbon Radioisotopes; D048429:Cell Size; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure; D006412:Hematopoietic Stem Cells / Q000528:radiation effects; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008954:Models, Biological; D009010:Monte Carlo Method; D011829:Radiation Dosage; D011874:Radiometry
chemical_list: D002250:Carbon Radioisotopes