Radiation Protection Dosimetry Advance Access published online on May 21, 2009
Radiation Protection Dosimetry, doi:10.1093/rpd/ncp078
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FACTORS THAT ELEVATE THE INTERNAL RADIONUCLIDE AND CHEMICAL RETENTION, DOSE AND HEALTH RISKS TO INFANTS AND CHILDREN IN A RADIOLOGICAL–NUCLEAR EMERGENCY
Radiation Biology and Health Physics Branch, Atomic Energy of Canada Limited (AECL), Chalk River Laboratories, Chalk River, ON, Canada KOJ 1JO
* Corresponding author: richardr{at}aecl.ca, richardsonr{at}eacl.ca
The factors that influence the dose and risk to vulnerable population groups from exposure and internal uptake of chemicals are examined and, in particular, the radionulcides released in chemical, biological, radiological, nuclear and explosive events. The paper seeks to identify the areas that would benefit from further research. The intake and body burdens of carbon and calcium were assessed as surrogates for contaminants that either act like or bind to hydrocarbons (e.g. tritium and 14C) or bone-seeking radionuclides (e.g. 90Sr and 239Pu). The shortest turnover times for such materials in the whole body were evaluated for the newborn: 11 d and 0.5 y for carbon and calcium, respectively. However, their biokinetic behaviour is complicated by a particularly high percentage of the gut-absorbed dietary intake of carbon (
16%) and calcium (100%) that is incorporated into the soft tissue and skeleton of the growing neonate. The International Commission on Radiological Protection dose coefficients (Sv Bq–1) were examined for 14 radionuclides, including 9 of concern because of their potential use in radiological dispersal devices. The dose coefficients for a 3-month-old are greater than those for adults (2–56 times more for ingestion and 2–12 times for inhalation). The age-dependent dose and exposure assessment of contaminant intakes would improve by accounting for gender and growth where it is currently neglected. Health risk is evaluated as the product of the exposure and hazard factors, the latter being about 10-fold greater in infants than in adults. The exposure factor is also approximately 10-fold higher for ingestion by infants than by adults, and unity for inhalation varying with the contaminant. Qualitative and quantitative physiological and epidemiological evidence supports infants being more vulnerable to cancer and neurological deficit than older children.