Brevetoxins and emergency department visits among children: A case-crossover study of Florida red tides

Background: Algal blooms of Karenia brevis (“red tide”) produce brevetoxins that contaminate seawater, bioaccumulate in shellfish, and become aerosolized, exposing humans via ingestion and inhalation. While adult exposures are linked to respiratory and gastrointestinal symptoms, children—who may be especially vulnerable—remain understudied. We investigated whether short-term brevetoxin exposures trigger emergency department (ED) visits among children. Methods: We analyzed ED visits from coastal southwest Florida residents aged 0–18 years in the OneFlorida+ network (2012–2019) using a time-stratified case-crossover design with case and control days matched by week, day, month, and year. Two brevetoxin exposure indices were estimated for the prior 2 weeks (Lags 0–13 ): (1) waterborne, based on spatially interpolated K. brevis concentrations linked to residential ZIP codes, and (2) aerosolized, incorporating wind speed and direction. Conditional logistic regression models estimated odds ratios per interquartile range increases in exposure indices, adjusting for time-varying covariates. Models were fit overall and by diagnosis group, including among a negative control group consisting of primarily trauma-related diagnoses. Results: Overall associations were null, as were associations for the negative controls. Stratified models showed: (1) same-day increases in waterborne and aerosolized exposures were associated with ~50% higher odds of respiratory visits (216 cases); (2) increases in waterborne exposures 12–13 days prior were modestly associated with ear, nose, throat, dental, and mouth diseases (321 cases); and (3) increases in aerosolized exposures 6–9 days prior were associated with ~50% higher odds of eye diseases (53 cases). Conclusions: Brevetoxins may trigger ED visits for respiratory, eye, and ear–nose–throat complaints among children in coastal southwest Florida. As red tides in the Gulf increase, public health guidance tailored to children may be needed.