Seaweed piling up on a beach might look harmless, but as quantities begin to rot, they can release gases that are toxic to people.
In recent years, two people and several animals (including a horse and 36 wild boar) have died after inhaling toxic gases from decomposing seaweed on the Brittany coast in France. And between January and August 2018, thousands of people reported headaches, nausea and eye irritation after inhaling seaweed gas in the Caribbean.
