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Yung Sung Cheng,¹ Yue Zhou,¹ Clinton M. Irvin,¹ Richard H. Pierce,² Jerome Naar,³ Lorraine C. Backer,⁴ Lora E. Fleming,⁵ Barbara Kirkpatrick,² and Dan G. Baden³

¹Lovelace Respiratory Research Institute, Albuquerque, New Mexico, USA; ²Mote Marine Laboratory, Sarasota, Florida, USA; ³Center for Marine Science, University of North Carolina at Wilmington, Wilmington, North Carolina, USA; ⁴Centers for Disease Control and Prevention, Atlanta, Georgia, USA; ⁵National Institute of Environmental Health Sciences Marine and Freshwater Biomedical Science Center, University of Miami, Miami, Florida, USA

Abstract
Red tides in the Gulf of Mexico are commonly formed by the fish-killing dinoflagellate Karenia brevis, which produces nine potent polyether brevetoxins (PbTxs) . Brevetoxins can be transferred from water to air in wind-powered white-capped waves. Inhalation exposure to marine aerosol containing brevetoxins causes respiratory symptoms. We describe detailed characterization of aerosols during an epidemiologic study of occupational exposure to Florida red tide aerosol in terms of its concentration, toxin profile, and particle size distribution. This information is essential in understanding its source, assessing exposure to people, and estimating dose of inhaled aerosols. Environmental sampling confirmed the presence of brevetoxins in water and air during a red tide exposure period (September 2001) and lack of significant toxin levels in the water and air during an unexposed period (May 2002) . Water samples collected during a red tide bloom in 2001 showed moderate-to-high concentrations of K. brevis cells and PbTxs. The daily mean PbTx concentration in water samples ranged from 8 to 28 µg/L from 7 to 11 September 2001 ; the daily mean PbTx concentration in air samples ranged from 1.3 to 27 ng/m³. The daily aerosol concentration on the beach can be related to PbTx concentration in water, wind speed, and wind direction. Personal samples confirmed human exposure to red tide aerosols. The particle size distribution showed a mean aerodynamic diameter in the size range of 6-12 µm, with deposits mainly in the upper airways. The deposition pattern correlated with the observed increase of upper airway symptoms in healthy lifeguards during the exposure periods. Key words: brevetoxin, exposure assessment, Karenia brevis, marine aerosol, particle size distribution, personal exposure, red tide. Environ Health Perspect 113:638-643 (2005) . doi:10.1289/ehp.7496 available via http://dx.doi.org/ [Online 9 February 2005]

This article is part of the mini-monograph "Aerosolized Florida Red Tide Toxins (Brevetoxins) ."

Address correspondence to Y.S. Cheng, Lovelace Respiratory Research Institute, 2425 Ridgecrest Dr. SE, Albuquerque, NM 87108 USA. Telephone: (505) 348-9410. Fax: (505) 348-8567. E-mail: ycheng@lrri.org

We thank D. Kracko and J. McDonald for the liquid chromatography/mass spectrometry analysis.

This research was supported by the National Institute of Environmental Health Sciences (NIEHS) grant P01 ES 10594 and a Minority Supplement to the P01, also from the NIEHS, as well as by the Centers for Disease Control and Prevention, the Florida Harmful Bloom Taskforce, and the Florida Department of Health.

The authors declare they have no competing financial interests.

Received 2 August 2004 ; accepted 20 December 2004.