S.C.U.B.A. Diving

By KATE SPINNER
New York Times Regional Newspapers

ENGLEWOOD - When red tide drifts into town, coastal residents cough and wheeze. They also spend more time in the emergency room with pneumonia, according to a new study.

Scientists already recognized that toxin produced by red tide can strip manatees of their ability to ward off disease. So they started looking at whether the toxin causes similar damage to the human immune system.

Barbara Kirkpatrick, an environmental health scientist at Mote Marine Laboratory in Sarasota, said her study suggests the toxin does cause immune deficiency in humans.

It revealed a 31 percent increase in emergency room visits for pneumonia when red tide bloomed near the coast.

Pneumonia generally attacks only after a person's immune system has been weakened by another illness.

"There's lots more work to be done, but it's sort of really the first piece of information that we've had," Kirkpatrick said.

The study, funded by the Centers for Disease Control and Prevention and the Florida Department of Health, will be published in an edition of the scientific journal Harmful Algae.

Kirkpatrick said the study does not give definitive proof that red tide toxins damage the human immune system, but the data add to a growing body of evidence that points to the toxin's ability to break down human defense against disease.

She revealed the results of the study at a public health meeting Wednesday night at Lemon Bay Park in Englewood.

During a three-month period when a red tide bloom hugged the Sarasota County shoreline, coastal residents visited the emergency room with complaints of respiratory ailments 54 percent more often than they did during a three-month period when there was no red tide, according to Kirkpatrick's research.

"When we broke it down to coastal residents, people with ZIP codes on barrier islands or on water, they were the ones who had the increase in admissions," Kirkpatrick said.

She noted that pneumonia-related visits to the emergency room increased 19 percent across all ZIP codes during the bloom.

But the increase in pneumonia-related visits increased 31 percent for residents who lived within a mile and a half of the beach, she said.

To conduct the study, Kirkpatrick reviewed Sarasota Memorial Hospital emergency room records from October, November and December 2001 and 2002.

Red tide plagued the coast during those three months in 2001, but was absent during the same period the following year.

Kirkpatrick broke down the data by ZIP code to see where the people who visited the emergency room lived.

The Sarasota hospital did not keep records of whether people who checked into the emergency room were exposed to red tide, but there were no reports of high pollen counts or unusual pneumonia outbreaks in 2001.

By analyzing records during the same three months the next year, Kirkpatrick said, the potential for pollen or seasonal tourism to skew the data is minimal.

Red tide is caused by a microscopic algae known in scientific circles as Karenia brevis, which occasionally encounters conditions in the Gulf of Mexico that allow it to over-populate into a bloom.

The algae naturally produce a poison that, in very low concentrations, causes little harm. But when a lot of the red tide-causing algae start reproducing and dying off, the poison accumulates to such high levels that it kills fish, coral, manatees and dolphins.

The toxin also becomes airborne, and if the bloom is inshore and the wind is blowing east, the toxic air finds its way to the sunbathers and shell collectors on the beach. Sometimes it wafts further inland as an unwelcome visitor to backyard barbecues and pool parties.

That irritating air worries people who live near the coast. Several residents at the Englewood forum told health officials they were concerned about the way red tide toxins affected their health.

Carol Ashton, who lives on Manasota Key, said her seasonal neighbor returns home to New Jersey with a sinus infection every time she visits when red tide is present.

Although the toxin causes such respiratory problems for people and might also weaken their immune systems, it has yet to prove deadly for humans, said Lorraine Backer, one of the study's 10 co-authors and team leader epidemiologist at the Centers for Disease Control in Atlanta.

She said scientists have documented the toxin's ability to destroy the immune system in manatees, but it's important to keep in mind that manatees breathe, eat and swim in the toxin.

For three years, Backer has been studying the effect of the red tide toxin on healthy lifeguards who work full-time on Sarasota beaches.

Though the lifeguards show signs of temporary illness, such as coughing and throat irritation when red tide is around, Backer said she has not come across any evidence that the toxin causes long-term health problems in the lifeguards.

Cathy Walsh, manager of the marine immunology program at Mote Marine Laboratory, said more research will show whether there is a threshold of exposure that people can withstand before the toxin harms their immune systems or causes long-term health problems. Certain populations, such as the very young, the elderly or the chronically ill, might also be more vulnerable to immune system suppression from the toxin, she said.

Inspired by Kirkpatrick's research and the evidence of the toxin's ill effects on manatees, Walsh recently began research to pinpoint exactly how red tide toxins attack different human immune cells.

"For a long time, people on the beach have recognized that respiratory symptoms are common and I think for a long time people assumed once you leave the beach that's the end of the story," Walsh said. "But there is actually a lot of evidence that the effects are more long term."

Source: http://www.gainesville.com/apps/pbcs.dll/article?AID=/20060730/LOCAL/207300330