Brevetoxin composition in water and marine aerosol along a Florida beach: Assessing potential human exposure to marine biotoxins

Abstract

The toxic dinoflagellate, Karenia brevis, produces a suite of polyether neurotoxins (brevetoxins, PbTx) that cause massive fish kills and neurotoxic shellfish poisoning. A unique characteristic of K. brevis blooms is the associated airborne (aerosolized) toxin component causing respiratory irritation to humans and other mammals. This study was undertaken in collaboration with human respiratory effects studies to establish the type and amount of brevetoxins to which beach-goers were exposed during a coastal harmful algal bloom (HAB). Concentrations of K. brevis cells were monitored in water, and brevetoxin concentrations were monitored in water and air over 3-day periods during a non-exposure control study (no HAB) and an exposure study (HAB event) along the Gulf Coast of Sarasota, FL, USA. The aerosol particle size distribution was also determined to assess brevetoxin aerosol deposition in the human respiratory system. During the non-exposure study, very low to background K. brevis cell counts were observed on day 1 and at background levels (<1 × 10 3 cells/L) on days 2 and 3; brevetoxin concentrations were very low in water and non-detectable in air. In contrast, the exposure study samples exhibited moderate concentrations of K. brevis cells in surf water (1 × 10 5 to 1 × 10 6 cells/L) and brevetoxin concentrations (sum PbTx-1, -2, and -3) in water ranged from <1 to 14 μg/L. In air, brevetoxin concentrations were highest on day 1, diminishing on day 2, and below detection levels on day 3, reflecting a change in wind direction from onshore to offshore during this period. Quantitation of individual brevetoxins showed that PbTx-2 was the most abundant in water, while PbTx-3 was the most abundant in air. The brevetoxin antagonist, brevenal, also was detected in water and aerosol samples during the exposure study. Particle size distribution analyses indicated that most of the aerosolized brevetoxin would be deposited in the nasal, oral, and pharyngeal regions, consistent with reported upper airway symptoms of stinging eyes and nose and dry, choking cough from throat irritation. About 2–3% would be deposited farther down in the tracheobronchial and alveolar regions, as evidenced by symptoms of wheezing, airflow reduction and chest tightness.