Sargassum Inundation Events (SIEs): Impacts on Human Health

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Sargassum inundation events (SIEs) can potentially affect human health nearshore or decomposing on beaches. For example, Sargassum may harbor organisms, like jellyfish, that can cause skin irritation. Exposure to hydrogen sulfide and ammonia, produced during the decay of Sargassum, may also cause mild to serious health effects, including respiratory, cardiovascular, and neurological impacts. Additionally, Sargassum accumulates and leaches pollutants, including pesticides and heavy metals like arsenic, which could harm human health and the environment.

On this page:

• Skin Irritation from Sargassum Inundation Events
• Respiratory, Cardiovascular and Neurological Effects of Hydrogen Sulfide and Ammonia
• Impacts from Bioaccumulation and Leaching of Heavy Metals, Pesticides, and Other Pollutants from SIEs on Seafood Safety
• Protect Yourself and Others from Exposure to Sargassum

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Skin Irritation from Sargassum Inundation Events

Sargassum harbors tiny organisms, such as jellyfish larvae, that can irritate the skin. Therefore, during  SIEs, swimmers may suffer skin irritation upon contacting the mats.

Respiratory, Cardiovascular and Neurological Effects of Hydrogen Sulfide and Ammonia

During, SIEs, hydrogen sulfide and ammonia production typically occurs after algal mats have been beached on land for 48 hours, which may pose a human health hazard. Hydrogen sulfide is a corrosive and toxic gas with a foul odor reminiscent of rotten eggs. Ammonia is a colorless, highly irritating gas with a pungent urine, sweat, or dead fish odor that can be corrosive at high concentrations. The effects of these gases on people can be severe and increase with concentrations.

Prolonged exposure to hydrogen sulfide, which tends to occur in areas with decomposing Sargassum, can cause upper airway irritation, nausea, headaches, vertigo, confusion, memory loss, and neurocognitive impacts. Inhalation of this gas may worsen the health of sensitive populations such as people with asthma or other respiratory problems. In 2018, doctors reported 11,402 cases of acute exposure to hydrogen sulfide produced by decomposing Sargassum in Martinique and Guadeloupe. Although human health effects of low concentrations of ammonia released by decomposing Sargassum are less documented, they may cause coughing, and nose and throat irritation.

It has been hypothesized in a recent paper that pregnant women exposed to hydrogen sulfide generated from Sargassum strandings may also be at a higher risk of early onset preeclampsia, a potentially life-threatening pregnancy complication.

Bioaccumulation and Leaching of Heavy Metals, Pesticides, and Other Pollutants from SIEs on Seafood Safety

Sargassum is reported to bioaccumulate heavy metals and metalloids, particularly arsenic, which poses potential health hazards to people when desirable seafood species feed on Sargassum or are exposed to their leachates. The concentration of arsenic on Sargassum that washed onto beaches in Mexico along the Gulf of America in 2018 ranged from 29.0-65.7 mg/kg, which is greater than the recommendations for human consumption of seaweeds made by the French Agency for Food, Environmental and Occupational Health and Safety. Edible bivalves found in SIE areas in Martinique have shown arsenic levels exceeding human health consumption recommendations from the French National Institute for Industrial Environment and Risks and could be potentially harmful to individuals who consume seafood on a regular basis. Sargassum can also bioaccumulate organic compounds like chlordecone, a harmful pesticide that was widely used in the French West Indies during the 1970s-1990s.

Live Sargassum mats may also support the growth of Vibrio bacteria due to the presence of sufficient nutrients to support its growth. This suggests that the accumulation of Sargassum could lead to an increased risk of Vibrio-related illness through foodborne exposure; but reported sanitary risks to date have been minor. More research is needed to evaluate this and other risks.

Moreover, a recent study showed that SIEs contribute to the transport and deposition of microplastics to coastal areas. More study is need to investigate the potential effects of these microplastics on food webs as well as potential human health effects related to Sargassum use as renewable raw material (e.g., for food and cosmetics), and its final disposal.

Protect Yourself and Others from Exposure to Sargassum

Human health risks associated with Sargassum exposure may be reduced by considering some of the recommendations and practices put forth by local and/or state health and environmental agencies. While these are some common guidelines provided by these agencies, we recommend following state and/or territory guidelines.

• Avoid recreating in waters that contain excessive Sargassum. Some of the organisms it harbors may irritate your skin.
• Stay away from areas where Sargassum is decomposing. If you live nearby, close your windows and doors.
• If you experience any airway irritation, nausea, headaches, vertigo, confusion, burning of the eyes, or other symptoms, stay away from the area with Sargassum until your symptoms are no longer present and the decay of Sargassum is no longer off-gassing.
• Avoid or limit your time close to areas with decomposing Sargassum if you have asthma or other respiratory conditions.
• Anyone handling Sargassum, particularly workers that collect and transport it from the beach to alternative locations, should consider wearing protective clothing such as gloves, boots, and respiratory protection as a precaution.

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References:

• Avis de l’Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail (ANSES). (2011). Algues vertes: risques liés aux émissions gazeuses des algues vertes pour la santé des populations avoisinantes, des promeneurs et des travailleurs. [Green algae: Risks related to gaseous emissions from green algae to the health of neighboring populations, walkers and workers.] ANSES, Paris France.
• de Lanlay, D. B., Monthieux, A., Banydeen, R., Jean-Laurent, M., Resiere, D., Drame, M., & Neviere, R. (2022). Risk of preeclampsia among women living in coastal areas impacted by Sargassum strandings on the French Caribbean Island of Martinique. Environmental Toxicology and Pharmacology, 94, 103894.
• Devault, D. A., Massat, F., Lambourdière, J., Maridakis, C., Dupuy, L., Péné-Annette, A., & Dolique, F. (2022). Micropollutant content of Sargassum drifted ashore: Arsenic and chlordecone threat assessment and management recommendations for the Caribbean. Environmental Science and Pollution Research, 29, 66315-66334.
• Devault, D. A., Modestin, E., Cottereau, V., Vedie, F., Stiger-Pouvreau, V., Pierre, R., Coynel, A., & Dolique, F. (2020). The silent spring of Sargassum. Environmental Science and Pollution Research, 28, 15580-15583.
• Devault, D. A., Pierre, R., Marfaing, H., Dolique, F., & Lopez, P. J. (2021). Sargassum contamination and consequences for downstream uses: a review. Journal of Applied Phycology, 33, 567-602.
• Florida Department of Health. (2023). Sargassum [Fact Sheet]. Florida Department of Health, Bureau of Environmental Health, Public Health Toxicology, Division of Disease Control and Health Protection.
• Florida Department of Health in St. John’s County. (2023, June). Sargassum (Seaweed). Florida Department of Health, Bureau of Environmental Health, Public Health Toxicology, Division of Disease Control and Health Protection.
• Florida Fish and Wildlife Commission (FFWCC). (n.d.). Sargassum Bloom. Florida Fish and Wildlife Conservation Commission.
• Institut national de l'environnement industriel et des risques (INERIS). (2010). Arsenic et ses derives inorganiques. [Arsenic and its inorganic derivatives.] INERIS-DRC-09-103112–11453A, Version N°4 – 2010. INERIS, Paris, France.
• Michotey, V., Blanfuné, A., Chevalier, C., Garel, M., Diaz, F., Berline, L., Le Grand, L., Armougom, F., Guasco, S., & Ruitton, S. (2020). In situ observations and modelling revealed environmental factors favouring occurrence of Vibrio in microbiome of the pelagic Sargassum responsible for strandings. Science of the Total Environment, 748, 141216.
• Modestin, E., Devault, D. A., Baylet, A., Massat, F., & Dolique, F. (2022). Arsenic in Caribbean bivalves in the context of Sargassum beachings: A new risk for seafood consumers. Environ Monit Assess, 194, 553.
• Resiere, D., Valentino, R., Neviere, R., Banydeen, R., Gueve, P., Florentin, J., Cabie, A., Lebrun, T., Megarbane, B., Guerrier, G., & Mehdaqui, H. (2018). Sargassum seaweed on Caribbean islands: An international public health concern. The Lancet, 392, 2691.
• Tapia-Fuentes, J., Cruz-Salas, A. A., Martínez-Salvador, C., Ojeda-Benítez, S., Vázquez-Morillas, A., & Álvarez-Zeferino, J.C. (2023).  Presence of microplastics deposited in Sargassum sp. on sandy beaches. Regional Studies in Marine Science, 66, 103152.
• United Nations Environment Programme- Caribbean Environment Programme. (2021). Sargassum white paper – Turning the crisis into an opportunity [White paper]. Ninth Meeting of the Scientific and Technical Advisory Committee (STAC) to the Protocol Concerning Specially Protected Areas and Wildlife (SPAW) in the Wider Caribbean Region. Kingston, Jamaica.
• Vázquez-Delfín, E., Freile-Pelegrín, Y., Salazar-Garibay, A., Serviere-Zaragoza, E., Méndez-Rodríguez, L. C., & Robledo, D. (2021). Species composition and chemical characterization of Sargassum influx at six different locations along the Mexican Caribbean coast. Sci Total Environ., 795, 148852.