Speaker
Dr
Carmel Mothersill
(Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Canada)
Description
Purpose: Radium is a long lived actinide in the uranium decay chain. In living organisms it completes with calcium and thus can accumulate in organisms exposed to radium as a result of uranium mining and milling activities associated with the nuclear industry. Currently actinides are assigned an RBE (relative biological effectiveness) factor of between 20 and 40 but this value is highly uncertain as there are very few studies which measure biological effects following chronic exposure to low doses of radium. The aim of this study was to assess the impact of lifetime ingestion of environmentally relevant levels 226Ra on a common freshwater fish species.
Methods: Fathead minnow (Pimephales promelas, Rafinesque) were obtained at the first feeding stage and established on a commercial fish food diet containing 226Ra in the activity range 10mBq/g-10Bq/g. They remained on this diet for 18 months and were sampled invasively at 1,6 and 18 months to assess biochemical indices and accumulated dose and non-invasively also at 12 and 15 months to assess growth.
Results: Fish fed 10 and 100mBq/g diets showed a transitory dysregulation of growth at 6 and 12 months. Fish fed higher activities showed similar or less significant effects. Bioaccumulation at 1 month was below detection levels. At six months significant amounts of 226Ra were present but at 18 months they were gone and radium levels were at background in spite of the continued ingestion of the isotope. Assessment of bystander stress signaling throughout the time period showed a constant fish to fish signaling at all times and doses measured.
Conclusions: Fathead minnow appear to bioaccumulate 226Ra initially and this is associated with growth dysregulation. However after 18 months an effective purging mechanism appears to be in place. The results may be important in the assessment of long-term environmental impacts of 226Ra.
Primary author
Dr
Carmel Mothersill
(Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Canada)
Co-authors
Dr
C B Seymour
(Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Canada)
Dr
D Lariviere
(Department of Radiation Chemistry, Laval University, Quebec City, Canada)
Dr
R W Smith
(Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Canada)
