Asthma, Aerosolized Florida Red Tide Toxins (Brevetoxins), and Off-shore Winds

Florida red tides occur annually in the Gulf of Mexico as blooms of marine dinoflagellates, Karenia brevis. K. brevis produces highly potent natural polyether toxins, brevetoxins, which cause bronchoconstriction in experimental animals. In prior studies, people with asthma had increased respiratory symptoms and deceased pulmonary function after walking on beaches during Florida red tides. Brevetoxins, measured by LCMS, HPLC and ELISA, were detected in both seawater and aerosol samples collected on the beach.

In a subsequent study, high concentrations of Karenia brevis cells (1-4.6 million cells/L) and brevetoxins (13.4-128.0 um/L) were found in seawater. However, because of strong off-shore winds, concentrations of brevetoxins in aerosols were close to analytic limits of detection (0.01-0.14 ng/m3) in high-volume air samples. Sixty-four persons with physician-diagnosed asthma were evaluated before and after a 1 hour walk on the beach using a questionnaire and spirometry. Compared with results obtained before beach exposure, participants were significantly more likely to report respiratory symptoms and demonstrate significant decreases in pulmonary function afterwards. This is consistent with previous studies with on-shore winds and measurable concentrations of brevetoxins in aerosol samples. There were no differences in respiratory symptoms or pulmonary function during a study without Florida red tide.

This study demonstrated adverse health effects in asthmatics from inhaling aerosolized brevetoxins at concentrations close to current limits of detection. This study has implications for asthmatics in geographic areas that regularly experience Florida red tides: previously it was believed to be “safe” to use beaches as long as the winds were off-shore.