Florida Red Tide: Inhalation Toxicity of Karenia brevis Extract in Rats.

Area of Science:

• Marine toxicology
• Environmental health

Background:

• Brevetoxins, produced by *Karenia brevis*, are marine neurotoxins.
• Marine mammal deaths during red tides suggest respiratory, nervous, hematopoietic, and immune systems are targets.

Purpose of the Study:

• Evaluate effects of repeated *K. brevis* extract inhalation on rat target systems.
• Assess potential toxicity in mammalian models.

Main Methods:

• Rats inhaled *K. brevis* extract (200, 1000 microg/L) for 4 hrs/day, 5 days/week, up to 4 weeks.
• Immunohistochemistry, clinical observations, hematology, serum chemistry, histopathology, and immune function assays were performed.

Main Results:

• Brevetoxin-like compounds deposited in rat lungs but caused no clinical signs or histopathological changes.
• Hematology and serum chemistry remained unaffected.
• Immune suppression indicated by reduced spleen cell and lymphocyte responses *in vitro*.

Conclusions:

• Repeated brevetoxin inhalation suppressed rat immune function without causing overt toxicity.
• Observed differences from marine mammal responses may be due to dose or species sensitivity.