Chronic Toxicity of Radium-226 in the Aquatic Invertebrates Daphnia magna and Chironomus dilutus
Bibliographic record
Abstract
Canada is one of a select few countries that are actively engaged in the full nuclear fuel cycle, encompassing uranium mining and milling, fuel refining and fabrication, medical isotope generation, nuclear power production and associated waste management. Currently, all operating uranium mines in Canada are located in Saskatchewan. Canada’s involvement in the nuclear fuel cycle and the accompanying stringent regulatory oversight have the potential to yield significant economic benefits for the country. The mining, milling, and refining of uranium associated with this fuel cycle result in the production of residual materials. Canadian regulations mandate the safe management of these residues, including process wastewater, tailings, and waste rock stockpiles. Among the radionuclides of concern, radium-226 (226Ra) is of particular importance due to a number of factors. Firstly, it has a long half-life, at approximately 1600 years. Secondly, the hazards associated with its immediate daughter radon are significant. Thirdly, it is highly mobile under a number of common environmental conditions. Finally, it has the potential for bioaccumulation in tissues. Although Canadian regulatory limits exist for radium in mining effluents, no guideline for the protection of aquatic life exists for 226Ra. The overall aim of this research project was to contribute data, on the toxicity of 226Ra to two aquatic invertebrates (Daphnia magna and Chironomus dilutus), to a larger effort aimed at building a species sensitivity distribution (SSD) which will provide the Canadian Nuclear industry and environmental regulators essential data to hopefully generate a Water Quality Guideline for the Protection of Aquatic Life for 226Ra. To this end, three 21-day chronic toxicity tests were performed with D. magna, with endpoints of survival and reproduction. Additionally, a multigenerational study and a bioaccumulation assay were conducted. Furthermore, a partial life-cycle exposure with C. dilutus to 226Ra was conducted with survival, growth, pupation, and emergence as the endpoints. Finally, an additional experiment with C. dilutus was performed to assess whether sublethal exposure to 226Ra induced oxidative stress. Results from these experiments revealed that 226Ra had no statistically significant effects on the reproduction of D. magna, in any of the experiments that were conducted, and that 226Ra is bioaccumulative in D. magna. The 21-day median lethal concentration (LC50) was the main endpoint that was reported, and values ranged from 26.7 to 38.1 Bq/L for D. magna. Chronic exposure of D. magna to 226Ra appeared to elicit toxicity directly through the reduction of lifespan, as opposed to having effects on sublethal endpoints such as reproduction. The results from the experiments conducted with C. dilutus revealed that high activity concentrations of 226Ra (>25 Bq/L) could induce effects on growth. None of the other sublethal endpoints were affected to a significant extent by 226Ra. There were also no effects on oxidative stress.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".