In recent times, there have been several newspaper articles, academic symposia, and meetings within the tourism sector in our region regarding the pervasive sargassum weed now found polluting many beaches across the Caribbean.

However, while the major concern has been its possible effects on tourism, particularly in states that are heavily dependent on the industry to bolster or maintain their revenue, few articles, if any, have drawn attention to the possible dangers the seaweed may pose to human health.

The issue dates back to 2011 when larger than normal rafts of brown seaweed began washing up on shores around the Caribbean. In a report by Dr Andrea Boggild, clinical director of the Tropical Disease Unit at Toronto General Hospital and Dr Mary Elizabeth Wilson of the Harvard TH Chan School of Public Health in Boston, the seaweed was determined as originating from off the northeast coast of Brazil. By 2018, record amounts of the seaweed were reported.

Other reports have linked its excessive quantities to the effects of global warming where the waters issuing from the mouth of the Amazon River in Brazil meet the warm Atlantic Ocean near the equator. The seaweed has also been reported in excessive amounts in China’s Yellow Sea where it is known as ‘golden tide’.

With the sargassum seaweed now accumulating along the coasts of Florida, the Gulf of Mexico, and the lesser Antilles in the Caribbean during the past year, collaborations between oceanographers, ecologists, marine biologists, and public health agencies have begun to understand the causes, health effects, and prevention strategies.

Symptoms caused by the seaweed

Prolonged physical contact with the sargassum weed, or inhaling the hydrogen sulfide gas that it gives off as it decomposes on the beach, can cause heart palpitations, shortness of breath, dizziness, vertigo (the sensation of the place whirling and spinning, with a loss of balance), headache, and skin rashes.

The decomposing weed in fact releases both hydrogen sulfide and ammonia, which can not only cause respiratory and skin symptoms, but also neuro-cognitive (the nerve processes and structures involved in understanding) symptoms. Toxic exposure typically happens during decomposition, which occurs around 48 hours after the seaweed washes ashore.

On the Caribbean islands of Guadeloupe and Martinique alone, more than 11,00 cases of acute sargassum toxicity were reported for an eight-month period during 2018. The report was published in the Journal of Travel Medicine on July 1, 2019.

People may present to doctors with unusual symptoms that are reminiscent of an intoxication syndrome, but with no alternative explanation for their symptoms. Unfortunately, this matter continues to fly under the radar of most medical professionals.

Preventive measures

If the rafts of sagassum seaweed continue, as is very likely, there is the expectation that doctors will increasingly encounter pople with a range of symptoms associated with sargassum toxicity. It is also noteworthy that while no specific treatment for the sargassum toxicity exists, supportive medical care for the various symptoms will be necessary.

Consequently, it is better for people to avoid exposure to the seaweed, and for visitors to the island, tour operators and hotels to be cognisant of these effects in order to take active measures to minimise contact of their guests with the seaweed. These could include hiring clean-up crews, installing offshore barriers to limit the amount of seaweed washing ashore, and sending boats into the ocean to remove the seaweed. After returning home, travellers should seek medical care if symptoms occur or are persisting.

Nevertheless, physical removal from beaches or from bays of the fishing community may provide only temporary respite until the next raft of the seaweed arrives. The matter, therefore, has an international dimension that will need the international scientific community to work with local partners and those who can assist with the logistical handling of the seaweed, to design strategies with positive outcomes that are sustainable.

— Dr Derrick Aarons MD, PhD, is a consultant bioethicist and family physician; a specialist in ethical issues in health care, research, and the life sciences; the health registrar and head of the health secretariat for the Turks and Caicos Islands, and a member of UNESCO’s International Bioethics Committee (IBC).