The alert threshold for exposure to hydrogen sulphide, a potentially deadly gas emanating from the putrefaction of green algae, was lifted on Friday two days after it was triggered on a beach in the bay of Saint-Brieuc, announced the prefecture of Côtes d'Armor.
“As part of the monitoring of the health risk of exposure to hydrogen sulphide emanating from the putrefaction of green algae, it had been detected in the commune of Hillion on the site of the Saint-Guimond beach that the threshold was exceeded alert, set by the health authorities at 1 ppm (part per million), the night of July 20, 2022 at 3:45 a.m. ”
, indicates the prefecture in a press release.
Algae multiplication for 40 years
“Since then, the concentrations measured have not exceeded 1 ppm”
and the alert system has been lifted, adds the prefecture, which however invites the population frequenting the site to
“respect the municipal decrees still in force”.
This is the first time that an alert of this type has been triggered, since the establishment of a network of sensors on several Breton beaches.
Present at sea in their natural state, green algae began to multiply more than 40 years ago on certain Breton beaches, where they are nourished by nitrates spread by farmers in the fields and whose surpluses are transported by coastal rivers.
Since this summer, Air Breizh has been carrying out hydrogen sulphide readings at 12 measurement points in seven Breton bays from Douarnenez (Finistère) to La Fresnaye (Côtes d'Armor).
Information relating to hydrogen sulphide emissions and health issues is available on the ARS website, and the data collected as part of the sensor network is accessible on the Air-Breizh association website.
