A red tide is one type of harmful algal bloom and has been around since long before humans. However, pollution from chemicals, sewage, and industries supercharge and worsens these events. When red tide produces potent toxins, it wipes out fish, shellfish, mammals, and birds.
The toxins may also make the surrounding air difficult to breathe. It can be hazardous to human health, causing cough, headache, sore throat, chest congestion, fatigue, skin irritation, rashes, and burning or irritated eyes. Reactions to red tide may be worse in individuals with asthma, emphysema, or any other chronic lung disease.
Red Tide Causes Health Effects to Humans
Avoid entering bodies of water with a distinct foul odor, appear discolored, or have foam, scum, or algal mats (sheet-like accumulations of blue-green algae) on the surface.
People and animals are exposed to marine algal toxins through:
Eating shellfish or fish containing toxins
Swimming or other activities in the water
Breathing in tiny droplets in the air that contain toxins
People can get sick and have symptoms
Brevetoxins from red tides are airborne and may cause respiratory irritation, difficulty breathing, and increased asthma risk
Coughing, wheezing, shortness of breath, sneezing, and sore throat
Inflammation in the lungs and possible bronchitis outcome
Headache and eye irritation
Risk of infections and rashes
Neurotoxic shellfish poisoning
Immunocompromised people should be especially careful.
Exposure to blooms and long-term health effects
The long-term health effects of harmful algal blooms are still being studied, but research is showing damage to DNA that can lead to mutations in genes that normally prevent the formation of cancers.
Neurotoxicologist has found that exposure to toxins from blue-green algae leads to neurodegeneration and increased expression of gene markers in dolphin brains, similar to the changes found in humans with Alzheimer’s disease and related dementia.
Chronic dietary exposure to BMAA has been linked to a form of amyotrophic lateral sclerosis/Parkinson dementia complex (ALS/PDC)
How to protect yourself from harmful exposure
Check environmental or state websites for the local beach or lake closures before visiting. Red Tide Current Status
Get away from the aerosolized brevetoxins from the red tide.
Do not swim in the water if dead fish are on the shore.
Do not fish, swim, boat, or participate in water sports in areas experiencing a red tide. This includes swimming and jet-skiing.
Children should not play along the shoreline where they might e exposed to clumps of algae or red tide water.
Red tide poses the same risk to animals. Pets should not drink affected water and should avoid beach areas with red tide.
Wash immediately and thoroughly with clean water and soap if you come in contact with contaminated water.
Do not go into the water and you have open sores or cuts on your body; you risk flesh-eating bacteria, which can be associated with bloodstream infections
Do not eat shellfish such as clams and oysters that are harvested from areas with an active red tide. Follow local guidance when consuming harvested fish or shellfish.
Wear a particle filter mask or stay indoors to help with the symptoms of red tide.
People with chronic respiratory problems such as asthma should avoid areas with active red tides or severe algae blooms.
Do not drink directly from lakes, rivers, or ponds.
Boiling water does not remove or destroy algal toxins.
Over-the-counter antihistamines may decrease your symptoms.
See a doctor if you think you may have eaten contaminated seafood or are sick from exposure to red tide.
Talk with your healthcare provider if you have questions about your health and exposure to a harmful algal bloom.
Red Tide Frequently Asked Questions
Red Tide Current Status Map: https://myfwc.maps.arcgis.com/apps/View/index.html?appid=87162eec3eb846218cec711d16462a72
How often does red tide happen, and what is it? Nearly every summer, the gulf coast of Florida encounters Harmful algal bloom or HAB. These HABs are microscopic algae that produce deadly toxins which make the air difficult to breathe and kill local fish. These toxic HABs also usually turn the water red which leads to the common name of “Red Tide.” The type of algae that usually occurs off the gulf coast of Florida is known as Karenia brevis. How long does red tide last? When there is a red tide, it can last for weeks or even months. The longest recorded red tide in Florida lasted for 18 months, from October 2006 to March 2008. How far inland is impacted? Airborne red tide toxins can travel inland by up to a mile from the coast depending on the speed and direction of the wind, plus tide levels. Is red tide natural? Red tides have been around since long before humans. However, certain human activities are making them more frequent.. Since the 1980s, harmful red tide events have become more frequent and widespread. This is a result of pollution from industrial runoff, sewage spills, and overuse of lawn chemicals. Why didn't my hotel tell me this was happening? Red tide has negative impacts on Florida's economy, but the tourism industry has a moral responsibility to educate and warn visitors, putting their health before profit. How can we stop supercharging red tide? Stopping the source of pollution will reduce harmful algal blooms. Preventing runoff from yard spills from sewage facilities, updating septic tanks, industrial dumping, and changing the laws so that it holds polluters accountable.
Research on Brevetoxin
You cannot smell or see brevetoxins, but they become aerosolized and pass into the atmosphere near water, where they are generated, and we then breathe them in. Brevetoxins are tasteless, odorless, and heat and acid-stable. These toxins cannot be easily detected, nor can they be removed by food preparation procedures. These toxins pose a significant risk to sea turtle health. Documented effects of contaminants include potential disease progression and adverse impacts on development and immune function and caused tumors.
Aerosol Toxins From Red Tides May Cause Long-term Health Threat https://www.sciencedaily.com/releases/2008/07/080709110049.htm
Diaz, R. E., Friedman, M. A., Jin, D., Beet, A., Kirkpatrick, B., Reich, A., Kirkpatrick, G., Ullmann, S. G., Fleming, L. E., Hoagland, P. (2019) Neurological illnesses associated with Florida red tide (Karenia brevis) blooms. Harmful Algae. 82, 73-81. https://doi.org/10.1016/j.hal.2018.07.002
Effects of Inhaled Brevetoxins in Allergic Airways: Toxin–Allergen Interactions and Pharmacologic Intervention https://ehp.niehs.nih.gov/doi/10.1289/ehp.7498
Florida Fish and Wildlife: Red Tide Current Status
Illness and Symptoms: Marine (Saltwater) Algal Blooms https://www.cdc.gov/habs/illness-symptoms-marine.html
Krimsky, L., Staugler, B., Hall-Scharf, B., Stump, K., & Burton, R. (2018, December 4) Understanding the 2017-2018 Florida Red Tide. University of Florida website. http://blogs.ifas.ufl.edu/extension/2018/12/04/understanding-the-florida-red-tide/
Potential effects of brevetoxins and toxic elements on sea turtles after a red tide bloom event https://pubmed.ncbi.nlm.nih.gov/28693110/
Occupational Exposure to Aerosolized Brevetoxins during Florida Red Tide Events: Effects on a Healthy Worker Population https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1257562/
Reddy, R., Verma, N., & Mohammed, T.-L. (2019). A Rare Case of Hypersensitivity Pneumonitis due to Florida Red Tide. Case Reports in Pulmonology. https://link.gale.com/apps/doc/A602004852/HRCA?u=tamp44898&sid=bookmark-HRCA&xid=b1fad141
Review of Florida Red Tide and Human Health Effects: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3014608