Radium-226 bioaccumulation and toxicity in the great pond snail Lymnaea stagnalis

Area of Science:

• Environmental Toxicology
• Radiochemistry
• Aquatic Ecology

Background:

• Radium-226 (226Ra) is a concern for aquatic ecosystems due to its long half-life, bioaccumulation potential, and radiotoxicity.
• Canada lacks water quality guidelines for 226Ra to protect aquatic life.

Purpose of the Study:

• Evaluate the ecological risk of 226Ra in Canadian fresh waters.
• Determine the toxicity of 226Ra to the great pond snail, Lymnaea stagnalis, a calciphilic organism.
• Investigate 226Ra bioaccumulation and its effects on snail growth, survival, and oxidative stress.

Main Methods:

• Conducted two chronic toxicity tests (28-day juvenile and 52-day early-life stage) with L. stagnalis exposed to aqueous 226Ra concentrations from 0.1 to 100 Bq/L.
• Measured snail growth, survival, hatching success, and oxidative stress markers (glutathione peroxidase activity).
• Quantified 226Ra bioaccumulation in snail tissues, particularly shells.

Main Results:

• 226Ra bioaccumulated significantly more in snail shells than in soft tissues.
• Minimal apical effects of 226Ra were observed across tested concentrations.
• A slight reduction in juvenile survival was noted at 226Ra concentrations ≥ 50 Bq/L (NOEC = 4.27 Bq/L).
• A slight positive effect on glutathione peroxidase activity was observed in snails exposed for 52 days.

Conclusions:

• 226Ra bioaccumulation occurs in L. stagnalis, primarily in shells.
• Current 226Ra levels in most Canadian fresh waters (0.0002 - 7.8 Bq/L) are unlikely to cause toxic effects in L. stagnalis.
• The study provides data to inform the development of water quality guidelines for 226Ra in freshwater ecosystems.