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Human health consequences of long term exposure to gaseous emission produced by sargassum seaweed decomposition


Since 2010, massive and repeated invasions of sargassum seaweeds (s. fluitans and s.natans) have taken place on coasts of Caribbean countries. Stranding of these brown algae represents not only an environmental and economic disaster but also a real threat to human health due to the production of toxic gaseous and organic compounds that are not yet completely identified. Among them, however, acute toxicity of hydrogen sulfide H2S and ammonia NH3 is well documented. To date, there has been no comprehensive assessment regarding potential human health hazards associated with chronic exposure to H2S and NH3. This lack of knowledge is critical because residents of coastlines, impacted by sargassum stranding, are subject to repeated and prolonged exposure to, most often, low concentrations of potentially toxic gases emitted by the decomposing seaweed. A preliminary clinical study performed at the CHU (University Hospital) of Martinique in 2018, conducted on 160 patients, reported that the most frequently observed clinical signs of chronic exposure were conjunctival and upper airway irritation, difficult breathing or shortness of breath, skin rashes and headaches. On the basis of these preliminary results, notably underlining potential consequences on the respiratory system, we hereto propose to better characterize human health consequences of gaseous emissions produced by decomposing sargassum, and their association with exposure levels as evaluated via H2S and NH3 sensors in the French Caribbean region. Consequences of chronic inhalation on the respiratory system will be assessed via spirometry and body plethysmography testing. Biomarkers of lung inflammation and oxidative stress will be measured in exhaled air, breath condensate and blood plasma of exposed individuals. Signaling pathways involved in lung toxicity will be further characterized in a mouse model of chronic exposure. Genotoxicity and effects of prenatal exposition on lung development and postnatal lung dysfunction will also be studied in mice. Lastly, we will investigate the knowledge, belief and practices of the population at risk in the study region, by assessing people's feelings and sentiments about perceived sanitary, economic and social concerns associated with sargassum stranding, based on an anthropological approach as well as individual and collective interviews. The aim of the current study proposal is to meet the requirements of European, French and Caribbean authorities, relative to the improvement of scientific and medical knowledge about the consequences of repetitive sargassum stranding on exposed populations, particularly in regards to respiratory health. We thus expect to provide insight into effective short and long term public health strategies, through integrated approaches based on up-to-date technologies and clinical studies. (AU)

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