The current of Red Tide Research. (NIEHS News).

An interdisciplinary group of scientists from federal and state government, academic, and research institutions have completed the first phase of data collection for human exposure to aerosolized brevetoxins during red tide events. Brevetoxins are potent neurotoxins produced by the dinoflagellate Karenia brevis (previously classified as Gymnodinium breve), a marine microalga found in the Gulf of Mexico and the western North Atlantic. The first portion of this study, known as the 2001 Occupational Red Tide Survey, is being funded by the Florida Department of Health, the Centers for Disease Control and Prevention (CDC), the Florida Harmful Algal Bloom Taskforce, and the NIEHS. The group is being led by Daniel Baden, director of the Center for Marine Science at the University of North Carolina at Wilmington, and Lorrie Backer, leader of the CDC's Emerging Environmental Threats Team.

On an almost annual basis, K. brevis forms large toxic blooms, known as red tides, particularly along the west coast of Florida. An extensive bloom of K. brevis red tide such as the one present in Florida since late in the summer of 2001 can kill tons of fish. Marine mammals (such as the highly endangered West Indian manatee) and birds also succumb to the respiratory paralysis and other neurotoxic effects caused by exposure to brevetoxins.

One recognized human health effect from exposure to K. brevis and its toxins is neurotoxic shellfish poisoning (NSP), which can occur when people eat shellfish that have been contaminated through filter-feeding activities. NSP can be prevented by monitoring waters for K. brevis and rapidly closing shellfish beds when blooms approach; in the United States, the only reported cases of NSP in about 30 years have been from the consumption of shellfish collected illegally from closed beds.

In addition to NSP, people have reported a number of symptoms, including respiratory complaints, after being on or near the beach during a red tide event. Although a link has not been scientifically and medically demonstrated, scientists believe these symptoms are caused by exposure to aerosolized brevetoxins and perhaps airborne K. brevis cellular debris generated during red tide events.

During the K. brevis bloom that formed in August 2001 in the Gulf of Mexico, the research team collected water for K. brevis cell enumeration and for brevetoxin concentrations, collected air samples for brevetoxin concentrations, and monitored meteorologic conditions. The team also monitored the incidence of human health effects associated with red tide events. Specifically, pre- and postexposure information on pulmonary function and inflammatory response as well as respiratory symptoms was collected from a group of lifeguards stationed at the affected beaches and from some of the scientists collecting environmental samples. Preliminary results will be presented at the 2002 annual meeting of the Society of Toxicology to be held this month.

In the future, scientist collaborators will return to this area to collect similar human health and environmental data on the same individuals during a time when there is no red tide event. The scientists also plan to evaluate the health effects from exposure to red tide in people visiting beaches, particularly sensitive populations such as those with asthma and older people with chronic respiratory problems. In addition, ongoing studies are using experimental animals to evaluate both mechanisms and possible prevention of exposure to and health effects of the aerosolized brevetoxins associated with K. brevis red tides. --Red Tide Research Group

Harmful Algal Bloom Web Sites

National Oceanic and Atmospheric Administration http://state-of coast.noaa.gov/ bulletins/html/hab_14/hab.html

Woods Hole Oceanographic Institution http://www.agu.org/revgephys/ anders01/anders01.html

International Society for the Study of Harmful Algae http://www.cbr.nrc.ca/issha/

Florida Marine Research Institute http://www.floridamarine.org/

Mote Marine Laboratory http://www.mote.org/

Northwest Fisheries Science Center http://www.nwfsc.noaa.gov/hab/

University of Miami NIEHS Marine and Freshwater Biomedical Sciences Center http://www.rsmas.miami.edu/ groups/niehs/

National Marine Fisheries Service http://www.sh.nmfs.gov/ EAquaBpg.htm