Red Tides Worsen Asthma with Breathtaking Seascapes

MIAMI -- Harmful algal blooms known as red tides release toxins that can leave people with asthma gasping still harder for air, reported researchers here.

After spending just 60 minutes on a beach where a Florida red tide was present, teens and adults with asthma had small but significant decreases in standard measures of pulmonary function, reported Lora E. Fleming, M.D., Ph.D., of the University of Miami Rosenstiel School of Marine and Atmospheric Science.

"In the normal population, inhaled aerosolized red tide toxins can lead to eye irritation, rhinorrhea, nonproductive cough, and wheezing," Dr. Fleming and colleagues reported in the January issue of Chest.

"However, these symptoms usually subside after leaving beach areas," Dr. Fleming and colleagues said. "Our study shows that Florida red tide toxins may have a greater impact on patients with asthma, who experienced significant respiratory problems and decreased lung function after just one hour of beach exposure to the toxins."

Although the investigators only looked at short-term exposure, previous studies have shown that there are increased rates of emergency department admission for asthma exacerbation, upper airway disease, pneumonia, and bronchitis during periods of active red-tide blooms. Aerosols produced by the blooms can drift inland for at least a mile, wafting with them highly potent toxins known as brevetoxins.

Brevetoxins are sodium channel blockers and may activate histamine, and in animal studies have been shown to cause significant bronchoconstriction.

To get a better grasp of the effects of brevetoxins on lung function, the investigators asked 97 volunteers with asthma, mean age 38.2 + 18.6 years (range, 12 to 69 years) to spend an hour at the beach on two separate occasions: during a Florida red tide bloom, and when the waters were free of algal blooms.

The patients, all of whom had physician-diagnosed asthma, were asked to fill out questionnaires and were tested with spirometry both before and after their beach time.

The authors measured forced expiratory volumes at 1 second (FEV₁), midexpiratory phase of forced expiratory flow, peak expiratory flow, and forced vital capacity.

While the patients were sunning themselves and strolling along the strand, the authors conducted environmental monitoring, water, and air sampling. The patients were also given personal air monitors to carry while at the beach.

The investigators found that the participants were significantly more likely to report respiratory symptoms after being exposed to red tide aerosols than before exposure. On spirometry testing, the participants were found to have small but statistically significant decreases in FEV1, midexpiratory phase of forced expiratory flow, and peak expiratory flow after exposure.

Decreases in lung function were particularly pronounced among those participants who required regular asthma medications. No significant differences in lung function were detected when the waters were free of Florida red tide, however.

When they further divided the population in those who lived inland (66) and coastal dwellers (31), they found that the inlanders were more likely than the coast dwellers to have more severe asthma, to report symptoms, and to have decreased respiratory function after toxin exposure.

However, those who lived inland had higher baseline spirometry scores compared with coastal residents, suggesting that the beach dwellers already had compromised lung function from prior exposures to brevetoxins.

In addition, when the authors broke down the data according to asthma medication use in the 12 hours prior to the study, they found that there were no significant differences in spirometry or respiratory symptoms between recent medication users and non-users after exposure to the toxins, despite previous animal data suggesting that asthma medications were protective against the effects of brevetoxin.

"This suggests that without the prior preventive use of these asthma and brevetoxin-blocking medications, the effects of aerosolized red-tide brevetoxins among the participants with more severe asthma might have been even greater," the authors wrote.

"People with asthma, whether residents or tourists, need to be aware of the Florida red tides and their potential to exacerbate asthma, as well as their own personal reaction to Florida red tides," said Barbara Kirkpatrick, Ed.D, of the Mote Marine Laboratory in Sarasota, a co-author.