Vacationing in France? Watch Out for Deadly Seaweed

Sea lettuce is harmless in water, but it can become fatal when it washes ashore.

ByABC News
August 21, 2009, 8:35 AM

PARIS, Aug. 21, 2009 — -- Vacationers, beware! A potentially dangerous seaweed could be a threat to the health of millions of beachgoers on the shores of Brittany, western France.

Ulva Lactuca – more commonly known as sea lettuce – is harmless while living in the water. But it can become fatal when it decays on land after being washed ashore.

A gas which formed under a crust of seaweed killed a horse at the end of last month on a beach in Saint-Michel-en-Grève, on the Côtes d'Armor, the only one of the four departments of Brittany affected by the phenomenon. The horse collapsed and died after inhaling the deadly hydrogen sulphide gas. The horse rider lost consciousness and was treated at a local hospital. Last year, two dogs died in the same area in the same conditions.

This "green tide" has been present on Brittany beaches for the past 30 years. Environmental groups have blamed the use of huge amounts of nitrates used in intensive farming for a build-up of the seaweed. The nitrates seep into the region's rivers and end up in the sea.

Despite its small population of 3 million people living on just 5 percent of the country's agricultural land, Brittany is home to 60 percent of France's pig farms, 45 percent of its poultry farms and 30 percent of its dairy farms.

"The green seaweed is the physical expression of the pollution of the water in Brittany by nitrates. The population of Brittany is waiting for the reduction of at least 1/3 of the pollution by the nitrates of the water," Jean-Francois Piquot of the environmental group Eau et Rivieres de Bretagne told

"It hurts me a lot," Pierric Neveu who runs a camping ground overlooking Saint Brieuc told