The alert threshold for exposure to hydrogen sulfide, a potentially deadly gas that emanates from the putrefaction of green algae, was exceeded early Wednesday on a beach in the Bay of Saint-Brieuc, the Côtes of Armor prefecture announced.
“As part of the monitoring of the health risk of exposure to hydrogen sulfide emanating from the rotting of green algae, it was detected in the commune of Hillion in the Saint-Guimond site that the alert threshold was exceeded,” indicates the prefecture.
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 in the sea in its natural state, green algae began to multiply more than 40 years ago on certain Breton beaches, where they feed on the nitrates spread by farmers in the fields and whose surpluses are transported by coastal rivers.
Saint-Guimond beach closed to the public
The readings, carried out by the Air Breizh air quality observatory, “reached 1,565 ppm” (parts per million) around 3 a.m. on Wednesday and thus exceeded the threshold set by the Higher Council of Public Health ( HCSP), at 1ppm. .
Since this summer, Air Breizh has been taking hydrogen sulfide readings at 12 measurement points in seven Brittany bays from Douarnenez (Finistère) to La Fresnaye (Côtes d’Armor).
An update on the prefecture’s website reported a lower value (0.128) than the alert threshold indicated at 4:00 p.m., but the sector remains on alert.
Contacted by our AFP colleagues, the expert sub-prefect “Water, green algae and agroecological transition” Etienne Guillet confirmed that “the entire beach” of Saint-Guimond was “closed to the public by decree of the mayor until further notice”. and that a single peak (readings are taken every 15 minutes) had exceeded the alert threshold overnight from Tuesday to Wednesday.
Source: BFM TV
