Algae, a diverse group of photosynthetic organisms, play a vital role in aquatic ecosystems, serving as the foundation of the food chain and contributing to oxygen production. However, under certain conditions, typically fueled by nutrient pollution and warm temperatures, some algae species can undergo explosive growth, forming dense colonies known as algal blooms.
While not all algal blooms are harmful, certain species produce potent toxins and other compounds that pose significant risks to human and animal health. The impact of harmful algal blooms (HABs) on human health became strikingly evident in a series of public health crises around the world, affecting millions of people.
Health Risks of Harmful Algal Blooms
Depending on the duration of exposure, type, and concentration of toxins present, humans may experience serious health consequences. In some cases, even short-term exposure to contaminated water can lead to adverse health effects. Contact with water affected by HABs can cause skin and eye irritation, characterized by rash, redness, itching, burning sensation or swelling.
People who inhale aerosolized algal toxins may encounter throat discomfort and breathing difficulties, often followed by coughing due to respiratory tract irritation. Nausea, vomiting or diarrhea are common acute gastrointestinal symptoms that can develop as a consequence of drinking or coming into contact with water contaminated with high concentrations of toxins. Abdominal pain, headaches, fatigue, and fever frequently happen as subsequent symptoms.
While some immediate effects are visible within minutes to hours of exposure, others can result from prolonged or repeated exposure to low levels of algae toxins. Research shows that such exposure can lead to liver damage and the risk of gradually developing liver cancer. Numerous studies have also investigated the neurological impact of algal toxins on humans. Some of the commonly reported symptoms vary from muscle weakness and numbness or tingling in extremities to seizures and even paralysis.
While individual factors, such as age, overall health, immune status, and genetic predisposition, greatly determine the severity of the outcome, the dangers of exposure to harmful algal blooms are not to be underestimated. They represent a pressing public health concern requiring urgent attention and intervention.
Who is most at risk from harmful algal blooms?
The health effects of a harmful algal bloom are not felt equally. Children are more vulnerable because they are more likely to swallow water while swimming and because their smaller body weight means a given dose of toxin has a greater effect. People with existing liver conditions face heightened risk from microcystins, which target the liver specifically, while those with respiratory conditions such as asthma are more susceptible to the aerosolized toxins that drift off bloom-affected water. Pets and livestock are among the most frequent fatalities, as dogs in particular will drink from or swim in scummy water that a person would avoid, and small body size makes even a modest dose lethal. This uneven vulnerability is part of what makes HABs a public health issue rather than an individual one: the people least able to assess the risk are often the most exposed to it. For a fuller breakdown of specific conditions, see our overview of algae-associated illnesses.
How people are exposed to algal toxins
Understanding exposure routes helps explain why harmful algal blooms reach so many people so quickly. The most direct route is ingestion, drinking contaminated tap water or swallowing water during recreation, which is why bloom events so often trigger tap-water advisories. A second route is skin contact during swimming, boating, or fishing, producing the rashes and irritation associated with recreational exposure. A third, less obvious route is inhalation: wind and wave action aerosolize toxins into fine droplets that can be breathed in near affected water, affecting people who never actually touch it. Finally, toxins can accumulate in the food chain, concentrating in fish and shellfish and reaching people who eat contaminated seafood. Because a single bloom can expose a population through all four routes at once, containment after the fact is difficult, which is why prevention at the water source is so much more effective than response.
Algal Bloom Public Health Emergencies and LG Sonic’s Interventions
There have been several significant global incidents where large populations have been affected by HABs, leading to widespread impacts on public health and the environment. As a result, a great number of people have experienced the aforementioned health issues alongside significant instances of fish kills in the affected areas. These events have led to the issuing of public health advisories cautioning against the use of tap water for drinking or cooking, concerns about seafood safety, the closing of public beaches, and economic losses for coastal communities dependent on tourism and fishing.
The Rio Guandu public health crisis occurred in January 2020 in Rio de Janeiro, Brazil, when the water supply system sourced from the Guandu River was affected by algal blooms. The water became contaminated with geosmin and MIB, compounds produced by algae, causing an unpleasant taste and odor. Health concerns were raised, and as panic won over the population, bottled water supplies started running out despite the sudden significant increase in price. Additionally, there were fears about the potential long-term health effects of exposure to these contaminants.
This crisis directly affected more than 9 million residents of Rio de Janeiro who were supplied from the Rio Guandu drinking water reservoir. The incident that led to a temporary suspension of the water supply caused a domino effect that has prompted authorities to take urgent measures to protect public health.
Thanks to LG Sonic’s intervention, during which 8 MPC-Buoys were installed, we effectively eliminated geosmina-related problems using our ultrasound technology. This ensured a water treatment solution that is both chemical-free and environmentally sustainable. Furthermore, our ultrasound technology has contributed to saving over €29 million in chemical treatments since 2020.
A similar scenario played out in Santo Domingo, Dominican Republic. The country’s most important drinking water source, the Valdesia reservoir, which supplies drinking water to over 4 million people, has been plagued by cyanobacteria blooms, causing the water to turn green and emit foul odors, posing health risks. To tackle this emergency that has left millions without clean drinking water, the Santo Domingo Aqueduct and Sewer Corporation (CAASD) sought an experienced expert who could provide a sustainable solution, ultimately opting for the installation of LG Sonic technology to restore the ecosystem without the drawbacks of chemical treatments.
Due to the hazards posed by harmful algal blooms, numerous recreational water bodies worldwide have been forced to close over time, disrupting leisure activities and impacting local economies. LG Sonic intervenes in these cases as well. One of our success stories includes MPC-Buoy implementation in Lake Cross, Ireland, a water treatment plant and touristic hotspot, which was largely affected by algal blooms. Since implementing MPC-Buoys, uninterrupted water supply has resumed, business operations have normalized, and significant reductions in algae blooms have been achieved. Moreover, overall water quality has improved, and operational costs have been substantially decreased.
LG Sonic’s treatment has also shown remarkable results in a Dutch recreational lake, Noord Aa. In order to monitor, predict, and prevent excessive algae growth, 5 MPC Buoys have been installed. As a result, a 90% reduction in summertime phycocyanin concentrations (a pigment found in blue-green algae) was recorded. These successes in diverse environments underscore the effectiveness of our treatment solutions.
Government officials and the general public around the world have recognized LG Sonic as a leading expert in water management. As a result, our ultrasonic algae control devices have been installed in 60+ countries, in a wide range of environments, including lakes, drinking water reservoirs, and recreational water bodies. Our award-winning, solar-powered, environmentally friendly technology precisely targets algal blooms and eliminates the need for chemical treatment, thereby protecting water quality, ecosystems, and public health.
Connect with LG Sonic to learn how you can protect yourself and your community from the health risks of algal blooms. Discover our monitoring solutions that predict and prevent algal growth, ensuring safer water and a better quality of life for millions across the globe.
Why prevention matters more than response
Once a harmful algal bloom reaches a drinking water supply or a public beach, the options narrow to damage control: issue advisories, distribute bottled water, close the beach, and absorb the economic loss, exactly the pattern seen at Rio Guandu, where bottled water ran short and prices spiked as more than 9 million people lost trust in their tap water. Reactive measures are expensive, disruptive, and arrive after people have already been exposed. Preventing blooms at the source changes the equation. By combining real-time monitoring with chemical-free ultrasonic treatment, water managers can detect the conditions that precede a bloom and suppress algae before toxins are ever released, protecting public health while avoiding the cascade of advisories, closures, and emergency spending that follows a crisis. This is the difference between managing a disaster and preventing one, and it is why utilities in over 60 countries have moved toward source-level control.