The Costs of Respiratory Illnesses Arising from Florida Gulf Coast Karenia brevis Blooms

Porter Hoagland; Di Jin; Lara Y. Polansky; Barbara Kirkpatrick; Gary Kirkpatrick; Lora E. Fleming; Andrew Reich; Sharon M. Watkins; Steven G. Ullmann; Lorraine C. Backer


Environ Health Perspect. 2009;117(8):1239-1243. 

In This Article

Abstract and Introduction


Background: Algal blooms of Karenia brevis, a harmful marine algae, occur almost annually off the west coast of Florida. At high concentrations, K. brevis blooms can cause harm through the release of potent toxins, known as brevetoxins, to the atmosphere. Epidemiologic studies suggest that aerosolized brevetoxins are linked to respiratory illnesses in humans.
Objectives: We hypothesized a relationship between K. brevis blooms and respiratory illness visits to hospital emergency departments (EDs) while controlling for environmental factors, disease, and tourism. We sought to use this relationship to estimate the costs of illness associated with aerosolized brevetoxins.
Methods: We developed a statistical exposure–response model to express hypotheses about the relationship between respiratory illnesses and bloom events. We estimated the model with data on ED visits, K. brevis cell densities, and measures of pollen, pollutants, respiratory disease, and intra-annual population changes.
Results: We found that lagged K. brevis cell counts, low air temperatures, influenza outbreaks, high pollen counts, and tourist visits helped explain the number of respiratory-specific ED diagnoses. The capitalized estimated marginal costs of illness for ED respiratory illnesses associated with K. brevis blooms in Sarasota County, Florida, alone ranged from $0.5 to $4 million, depending on bloom severity.
Conclusions: Blooms of K. brevis lead to significant economic impacts. The costs of illness of ED visits are a conservative estimate of the total economic impacts. It will become increasingly necessary to understand the scale of the economic losses associated with K. brevis blooms to make rational choices about appropriate mitigation.


Harmful algal blooms (HABs) of Karenia brevis, a marine dinoflagellate, occur almost annually in the Gulf of Mexico off the west coast of Florida (Heil and Steidinger 2009). K. brevis cells produce potent polyether neurotoxins known as brevetoxins (Baden et al. 1995; Poli et al. 1986), which are released into the ocean when the cells are lysed by wind and waves (Pierce et al. 2001). At high concentrations, K. brevis blooms may cause mortality of fish, marine mammals, and sea birds. Humans who consume shellfish contaminated with brevetoxins are at high risk of developing neurotoxic shellfish poisoning (NSP) (Watkins et al. 2008). Further, there have been anecdotal reports of skin ailments resulting from contact with brevetoxin-contaminated water (Kirkpatrick et al. 2004).

HAB cell count generally correlates with brevetoxin concentration, and residual brevetoxins in seawater have been observed after blooms have diminished (Pierce RH, personal communication). Bubbles from breaking waves transport brevetoxins to the sea surface, where they may be released to the air as jet drops when the bubbles burst (Blanchard 1989; Pierce et al. 1990, 2003). In the air, brevetoxins become incorporated into marine aerosols, which are built around charged salt particles. Aerosol transport is highly influenced by wind speed and direction, and aerosolized brevetoxins can travel as much as 1 mile inland (Fleming et al. 2005; Kirkpatrick et al. 2008).

Woodcock (1948) reported the first accounts of respiratory irritation in humans during severe red tide (HAB) conditions on the Florida Gulf Coast. Subsequent studies have linked inhalation of aerosolized brevetoxins with adverse health effects, including rhinorrhea, nonproductive cough, and severe bronchoconstriction (Asai et al. 1982; Backer et al. 2003; Cheng et al. 2005; Fleming et al. 2005, 2007; Kirkpatrick et al. 2004, 2001; Music et al. 1973). Epidemiologic studies, animal experiments, and anecdotal reports now suggest that aerosolized brevetoxins are linked to both upper and lower respiratory illnesses in humans (Backer et al. 2003; Fleming et al. 2005, 2007; Kirkpatrick et al. 2004). In addition to significantly increased respiratory symptoms, asthmatic individuals have shown small but statistically significant changes in lung function immediately after 1hr visits to the beach during Florida blooms (Backer and McGillicuddy 2006; Fleming et al. 2005, 2007). After only 1 hr of exposure to aerosols at the beach, respiratory complaints may last up to 5 days in asthmatics (Kirkpatrick et al. 2008). Finally, research using data for respiratory visits to the emergency department (ED) demonstrated a significantly increased risk of visits for pneumonia, bronchitis, and asthma during a Florida red tide period compared with a similar period without red tide (Kirkpatrick et al. 2006). This risk is particularly relevant for coastal residents.

In the present study we assessed the relationship between K. brevis blooms and respiratory illness-related visits to hospital EDs while controlling for environmental factors and disease that also may function as significant risk factors for respiratory ailments. Further, we developed estimates of the costs of illness resulting from medical treatments for acute brevetoxin-related respiratory illnesses. This work is an important step toward understanding one component of the economic effects of K. brevis blooms. It may help guide the selection and implementation of management actions to mitigate public health effects and illness costs for brevetoxins and possibly other HABs. Further, it may provide insight to health care administrators and providers as to human resource and medical supply needs as a result of K. brevis blooms.


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