Is the beard on mussel poisonous?

The beard of a mussel, which consists of byssal threads used for anchoring to surfaces, is not poisonous. However, some mussels can accumulate toxins from their environment, particularly in harmful algal blooms, which can make the entire mussel harmful to eat. It's essential to ensure that mussels are sourced from clean waters and properly prepared to avoid any health risks. Always check local advisories regarding shellfish consumption for safety.