'Red tide toxins' leave beachgoers breathless

The ecological phenomenon, known as Florida red tide, can be harmful for people with asthma. Florida red tides, an annual event in areas along the Gulf of Mexico, are blooms of the ocean organism, Karenia brevis (K brevis), that are concentrated along shorelines and produce highly potent aerosolized toxins. New research reported in the January issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians (ACCP), shows that Florida red tide toxins (known as brevetoxins) can impact respiratory function and increase respiratory symptoms in patients with asthma.

“In the normal population, inhaled aerosolized red tide toxins can lead to eye irritation, rhinorrhea, nonproductive cough, and wheezing. However, these symptoms usually subside after leaving beach areas,” said study author Lora E. Fleming, MD, PhD, University of Miami Rosenstiel School of Marine and Atmospheric Science, Miami, FL. “Our study shows that Florida red tide toxins may have a greater impact on patients with asthma, who experienced significant respiratory problems and decreased lung function after just one hour of beach exposure to the toxins.”

Dr. Fleming and a team of researchers from seven academic, environmental, and government institutions evaluated the exposures and effects of aerosolized Florida red tide brevetoxins in 97 subjects with asthma. Participants, who were all residents of Sarasota, FL, spent at least one hour at Sarasota's Siesta Beach during active K brevis bloom (exposure period) and during a period when there was no bloom (nonexposure period). Detailed baseline information was collected, and all participants underwent pre- and post-beach evaluations, including medical history questionnaires, nasal swab sampling, and lung function testing (spirometry). Each participant also carried a personal air monitor while at the beach. Throughout exposure and nonexposure periods, researchers collected water and air samples and monitored air temperature, relative humidity, and wind speed and direction.

During active K brevis bloom exposure periods, significant differences were found for all participants between pre- and post- beach report of symptoms and pre- and post- spirometry. During exposure periods, participants reported a significant increase in symptoms, predominantly chest tightness, and differences were measured objectively on lung function testing. In contrast, no significant differences were observed between pre- and post- beach symptoms or spirometry during nonexposure periods.

Researchers further evaluated subpopulations based on area of residence and the use of asthma medication within 12 hours prior to the study. Inland residents were more likely than coastal residents to be severe asthmatics and had more reported symptoms and decreased respiratory function after toxin exposure. However, inland residents had higher baseline spirometry scores, compared with coastal residents, suggesting that coastal residents were already affected by the toxins through their environmental residential exposure even prior to study exposure, and, therefore, reacted less to the one-hour beach exposure. Furthermore, participants who reported using asthma medication within 12 hours prior to the study had similar post-exposure differences in spirometry and respiratory symptoms compared with those who did not use medication – even though a sheep model asthma study indicated that these medications have been shown to block the effects of the Florida red tide toxins.

“It is possible that coastal residents, who had less of a reaction to the toxins, have learned not to get exposed or may use more asthma medications to deal with red tides,” said study coauthor Barbara Kirkpatrick, EdD, Mote Marine Laboratory, Sarasota, FL. “People with asthma, whether residents or tourists, need to be aware of the Florida red tides and their potential to exacerbate asthma, as well as their own personal reaction to Florida red tides.” Florida residents and tourists can stay informed of Florida red tide conditions by checking with local environmental groups, including the Florida Department of Health and the Florida Marine Research Institute.

“Environmental asthma triggers, such as Florida red tide, can greatly impact the health of patients with asthma,” said Mark J. Rosen, MD, FCCP, President of the American College of Chest Physicians. “It is important for patients with asthma or other chronic respiratory illness to understand their personal limitations regarding red tide toxins and take steps to reduce exposure during times when red tide levels are at their highest.”