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French Agency for Food, Environmental and Occupational Health & Safety

Green algae: ANSES publishes its report and issues recommendations

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News of 07/07/2011

7 July 2011

In response to a solicited request received in February 2010 as part of the national plan to combat the spread of green algae, ANSES today published an Opinion and an Expert Assessment Report which complements the initial recommendations published by the Agency in July 2010. The key recommendation is that green algae should be collected and processed as rapidly as possible to mitigate potential risk.

Every summer for more than 30 years, massive quantities of green algae have been washing up on parts of the French coastline. This phenomenon was initially more limited but has become increasingly widespread, with the Cotentin Peninsula and Charente Maritime coasts being affected; Brittany (La Bretagne) is now the most heavily affected region.. Once washed up on beaches, these huge deposits of algae decompose and produce large quantities of gases, especially hydrogen sulfide, causing disagreeable smells and health problems for strollers and those living near the beaches in question. In an effort to rectify this situation, certain local authorities collect the algae from their beaches, before transporting them inland for processing. Workers engaged in the different aspects of this process are exposed to the fumes.
In February 2010, the French government drew up an action plan to combat green algae and called on the Agency to produce an expert assessment. ANSES published an initial Opinion in July 2010 with a first set of recommendations designed to protect workers involved in all stages of the elimination process, as well as the public. The Report published today and the accompanying Opinion complement the earlier work while reinforcing the first set of recommendations.

Recommendations for three types of action

ANSES first underlines the importance of preventive measures to avoid the proliferation of green algae.
When it is impossible to prevent algae from reaching the beaches, ANSES emphasises that collection, transport and disposal of algae in processing centres should be completed as rapidly as possible to try and prevent them from decomposing and producing toxic fumes. Studies have thus recommended that algae be collected and processed no more than 48 hours after arrival on the beach.
The Agency recommends favouring mechanised collection methods and states that the algae should be collected under conditions that minimise the exposure of the general public as far as possible. Signs should be erected around the perimeters of sites indicating that collection is taking place.
In areas that are too inaccessible for washed-up algae to be collected and thus posing a risk, the Agency recommends informing all those visiting or living near that part of the coast.
ANSES recommends that all workers involved in the collection, transport and disposal of green algae, whatever their contractual status (including seasonal workers), should be issued with portable individual hydrogen sulfide detectors. The Agency also suggests that staff receive appropriate information and training and that all periods of exposure be entered in their medical records.
Lastly, the work carried out for the expert collective assessment undertaken by ANSES was limited due to lack of knowledge of certain aspects. The Agency thus recommends further research, especially to improve the characterisation of gas emissions from green algae and the way emissions evolve over time, for a better understanding of the exposure hazard and toxicity of the various substances emitted.

Find out more

  • Opinion and report (in French): « Avis et rapport relatifs aux risques liés aux émissions gazeuses des algues vertes pour la santé des populations avoisinantes, des promeneurs et des travailleurs »