At this time last year, Sarasota and Manatee County residents were facing a red tide outbreak sparked by high water temperatures and the Piney Point disaster that killed thousands of fish, birds and other types of marine life. Tourists and locals were deterred from going to the beach because the smell was so strong, while toxins from the blooms floated through the air, causing symptoms like shortness of breath, coughs, itchy and watery eyes and noses, and headaches. Even if you lived miles inland, you could experience these side effects.

Typically, once red tide season subsides, so do our symptoms. But does repeated seasonal exposure affect our long-term health?

Sarasota's Roskamp Institute has been trying to answer that question since 2020. The institute, which focuses on a variety of neurological diseases, has studied 250 volunteers, comparing those with high red tide exposure to those with little or no exposure to judge the impact of red tide on the brain. Volunteers report their symptoms and give blood and urine samples during blooms.

The toxin that the micro-ogranism Karenia brevis produces is called a brevetoxin. It is colorless, odorless and damages the nervous system of marine life. It also has an effect on the human nervous system, interfering with the electrical signals sent through our neurons. This can cause disruptions in muscle movements and bodily sensations. Over time, you may experience lethargy or a general malaise.

According to a blog post published by Roskamp executive director Dr. Michael Mullen, when large amounts of brevetoxins are present in the body, they can cause gastrointestinal problems and neurological complications such as seizures, parathesias (tingling in the extremities), reversal of hot and cold sensations, and vertigo, especially when the toxin is ingested.

One of the most common routes brevetoxin takes to the brain is through ingestion of contaminated shellfish, according to the Centers for Disease Control and Prevention. While it is safe to eat store-bought and restaurant-served shellfish because it is regulated by the U.S. Food and Drug Administration, it is not safe to eat recreationally caught shellfish during a red tide outbreak.

Once a brevetoxin enters the body through inhalation, ingestion or skin exposure, Mullen writes that it can swiftly arrive at the brain, because it is fat-soluble and able to travel through the body with ease. It can also cause inflammation in multiple organs.

HCA Florida Sarasota Doctors Hospital pulmonologist Dr. Janie Mylett says that long-term lung inflammation can also occur, especially if you have underlying lung disease, emphysema or asthma. This can lead to permanent scarring of the lungs and trouble keeping airways open. She recommends taking precautions like wearing particulate masks (like the ones you wear for Covid-19 protection) or talking to your doctor about prescription anti-inflammatories and antihistamines.

"Masks won't completely prevent symptoms, because toxins are small enough to pass through the masks," says Mylett. "But wearing one will help reduce some irritation."

Serious issues usually do not develop in one red tide season, but rather through seasonal exposure. This is particularly concerning to residents who live on the coast. Emergency room visits for extreme migraines increased during the extended 2017-2019 outbreak, and, prior to that, from 2005 to 2009, an uptick in visits for neurological complaints were recorded, according t statistics from the Gulf of Mexico Coastal Ocean Observation System.

Mullen writes that one of the ways scientists are monitoring prior red tide exposure is by looking at the antibodies the body builds against the toxin. These can be measured in a blood sample.

"While a majority of volunteers did not have high levels of these antibodies, a few individuals did show high levels," writes Mullen. "When our research team took the blood samples from the volunteers, they hadn't been anywhere near brevetoxin for about six months. This implies that there are long-lasting immune effects after exposure to the toxin."

Now, the Roskamp study is investigating whether more or fewer antibodies correlate with more or less reporting of neurological signs and symptoms. Mullen and his staff are also looking to find treatments to stop or slow these effects, not only in those with chronic lung or neurological diseases, but also healthy individuals. Findings from the study are expected to roll out by the end of this year.

"Sometimes lung damage will resolve and other times it leaves chronic issues," says Mylett. "Hopefully, with these studies and further information, we can provide recovery to patients that live close to the water, increase their functional abilities and allow them to stay in their waterfront homes year-round."