• 226 Ra bioaccumulates moderately in the soft tissues of L. stagnalis • Incorporation in the shell is an important fate of bioaccumulated 226 Ra • An activity concentration of 226 Ra ≥ 50 Bq/L slightly reduced survival in juveniles • Glutathione peroxidase activity increased slightly at 10 Bq/L of 226 Ra • We report a Maximal Acceptable Toxicant Concentration of 10.7 Bq/L for L. stagnalis Radium-226 ( 226 Ra) may be of concern to aquatic ecosystems, because of its long half-life (1600 years), its potential for bioaccumulation and its radiotoxicity. Yet, in Canada, there is currently no 226 Ra water quality guideline for the protection of aquatic life. To better evaluate the ecological risk of this radioelement in Canadian fresh waters, we conducted toxicity tests with the great pond snail Lymnaea stagnalis . Because of the analogy between 226 Ra and calcium, this calciphilic organism was expected to readily bioaccumulate 226 Ra, particularly during its early-life stage. We performed two chronic toxicity tests with aqueous 226 Ra activity concentration ranging from 0.1 and up to 100 Bq/L: i) a 28-day juvenile test with newly-hatched snails (measurements: growth and survival) and ii) a 52-day early-life stage (ELS) test encompassing the embryonic stage (measurements: growth, hatching success and survival) and the juvenile stage (measurements: growth, survival and oxidative stress). In the ELS test, 226 Ra bioaccumulated four times more in the shell than in the whole-body soft tissues. Overall, there was almost no apical effect of 226 Ra on L. stagnalis in the tested concentration range, with only a slight evidence of juvenile survival reduction at 226 Ra ≥ 50 Bq/L in the ELS test (NOEC = 4.27 Bq/L, LOEC = 26.7 Bq/L, MATC = 10.7 Bq/L). In 52-d exposed snails, there was slightly significant positive effect of 226 Ra on glutathione peroxydase (GPx) activity. Our study suggests that 226 Ra in contaminated and uncontaminated fresh waters (0.0002 – 7.8 Bq/L) is unlikely to have toxic effects on L. stagnalis .
Guimard et al. (Wed,) studied this question.