Florida 'Red Tides' Can Irritate Asthmatics

WEDNESDAY, Jan. 10, 2007 (HealthDay News) -- Spending just one hour on a Florida beach during a "red tide" can cause a 10 percent drop in lung function and seems to trigger asthma symptoms in susceptible people, new research shows.

What's more, it may take up to five days for an asthmatic's lungs to return to normal after just one hour of red tide exposure.

"People with asthma need to be aware of their environment, particularly if they're visiting an area with Florida red tides," cautioned study author Dr. Lora Fleming, a professor in the departments of epidemiology, public health and marine biology and fisheries at the University of Miami Miller School of Medicine. Her report is published in the January issue of Chest.

If you have asthma and are traveling to or live in an area with red tides, Fleming recommended avoiding the beach during that time. "Go inland. Don't go to the beach when there's an onshore red tide and an onshore wind. There are plenty of other things to do in Florida," she noted.

Annually, harmful algae called Karenia brevis multiply in the Gulf of Mexico and cause the Florida red tide. Fleming said that you can't always see the red tide, but when you can, it turns the water a brownish color. A more obvious sign of the red tide is a terrible fish odor, she said. That's because the red tide causes fish to die off in great numbers. Fleming said other coastal areas experience red tides, but they are often caused by different organisms and may not have the same effects.

To investigate whether the red tide affected people with asthma, as had been anecdotally reported, Fleming and her colleagues recruited nearly 100 people with asthma to spend some time on the beach when the algae was in bloom.

The volunteers were monitored before going to the beach and then soon after they spent an hour walking on the beach during the time of red tide. They were also monitored after walking the beach during a time when no red tide was present.

All of the participants were told they could leave the beach if they started to feel symptomatic, and they were advised to continue using their asthma medications as directed. The researchers also monitored the conditions on the beach and in the water both during red tide time and during the normal period.

The researchers found that walking on the beach for an hour created no statistically significant difference in lung function or on asthma symptoms if there was no red tide.

However, during the time of the red tide, the volunteers were more likely to report experiencing respiratory symptoms and had a small, but statistically significant, drop in lung function. Fleming said the decrease in lung function was slightly more than 10 percent.

"The bottom line is, we don't think this will put someone in the hospital, but one hour makes a measurable difference in lung function," said Fleming.

The researchers don't know for sure what it is about the red tide that causes this reaction in people with asthma. It may act as an irritant or as an allergen. In people without asthma, the red tides often seem to cause watery eyes and nose and a cough.

"This study showed significant effects a very short time after exposure," said Dr. Jonathan Field, director of the asthma and allergy clinic at New York University Medical Center/Bellevue. "People need to be aware of the potential risk in that area if you're thinking of vacationing or relocating there."

More troubling, he said, may be the bigger picture. "These findings are worrisome for coastal areas and beyond. Is this an emerging type of biological allergen associated with global warming?" Field asked.

More information

You can check to see if there's currently a harmful algae bloom (red tide) occurring by visiting the National Oceanic and Atmospheric Administration.