Florida red tides are a natural phenomenon caused by dense aggregations of single cell or several species of unicellular organisms. Patches of discolored water, dead or dying fish, and respiratory irritants in the air often characterize these algal blooms. In humans, two distinct clinical entities, depending on the route of exposure, are associated with exposure to the Florida red tide toxins (particularly the brevetoxins). With the ingestion of brevetoxin-contaminated shellfish, neurotoxic shellfish poisoning (NSP) presents as a milder gastroenteritis with neurologic symptoms compared with other marine toxin diseases such as paralytic shellfish poisoning (PSP) or ciguatera fish poisoning. With the inhalation of the aerosolized red tide toxins (especially the brevetoxins) from the sea spray, respiratory irritation and possibly other health effects are reported in both humans and other mammals (Baden 1995, Fleming 1998a, Fleming 1998b, Fleming 1999a, Bossart 1998, Asai 1982, Eastaugh 1989, Pierce 1986, Music 1973, Temple 1995, Anderson 1994).This paper reviews the literature on the known and possible human health effects of exposure to the Florida red tides and their toxins. The review includes discussion of the red tide organisms and their toxins, as well as the effects of these toxins on both wild and laboratory animals as they relate to possible human health effects and exposures.
The extrathoracic region, including the nasal and oral passages, pharynx, and larynx, is the entrance to the human respiratory tract and the first line of defense against inhaled air pollutants. Estimates of regional deposition in the thoracic region are based on data obtained with human volunteers, and that data showed great variability in the magnitude of deposition under similar experimental conditions. In the past decade, studies with physical casts and computational fluid dynamic simulation have improved upon the understanding of deposition mechanisms and have shown some association of aerosol deposition with airway geometry. This information has been analyzed to improve deposition equations, which incorporate characteristic airway dimensions to address intersubject variability of deposition during nasal breathing. Deposition in the nasal and oral airways is dominated by the inertial mechanism for particles >0.5 mum and by the diffusion mechanism for particles <0.5 mum. Deposition data from adult and child nasal airway casts with detailed geometric data can be expressed as E(n) = 1 - exp(-110 Stk), where the Stokes number is a function of the aerodynamic diameter (d(a)), flow rate (Q), and the characteristic nasal airway dimension, the minimum cross-sectional area (A(min)). In vivo data for each human volunteer follow the equation when the appropriate value of A(min) is used. For the diffusion deposition, in vivo deposition data for ultrafine particles and in vivo and cast data for radon progeny were used to derive the following deposition: En=1-exp(-0.355Sf4.14D0.5Q-0.28), where S(f) is the normalized surface area in the turbinate region of the nasal airway, and D is the diffusion coefficient. The constant is not significantly different for inspiratory deposition than for expiratory deposition. By using the appropriate characteristic dimension, S(f), one can predict the variability of in vivo nasal deposition fairly well. Similar equations for impaction and diffusion deposition were obtained for deposition during oral breathing. However, the equations did not include airway dimensions for intersubject variability, because the data set did not have airway dimension measurements. Further studies with characteristic airway dimensions for oral deposition are needed. These equations could be used in lung deposition models to improve estimates of extrathoracic deposition and intersubject variability.
This paper reviews the literature describing research performed over the past decade on the known and possible exposures and human health effects associated with Florida red tides. These harmful algal blooms are caused by the dinoflagellate, Karenia brevis, and similar organisms, all of which produce a suite of natural toxins known as brevetoxins. Florida red tide research has benefited from a consistently funded, long term research program, that has allowed an interdisciplinary team of researchers to focus their attention on this specific environmental issue—one that is critically important to Gulf of Mexico and other coastal communities. This long-term interdisciplinary approach has allowed the team to engage the local community, identify measures to protect public health, take emerging technologies into the field, forge advances in natural products chemistry, and develop a valuable pharmaceutical product. The Review includes a brief discussion of the Florida red tide organisms and their toxins, and then focuses on the effects of these toxins on animals and humans, including how these effects predict what we might expect to see in exposed people.
Deposition patterns are described of a nasal spray formulation for a novel rhinovirus protease inhibitor. These patterns, which were generated from different nasal spray pumps, were characterized using a multisectional nasal airway model. A human nasal replica was made from an in vivo magnetic resonance imaging (MRI) scan of an adult male human. The nasal replica consisted of 77 acrylic plastic sections, 1.5-mm thick. Our data showed that the aerosols were deposited mainly in the anterior and turbinate regions with little passing beyond the nasopharyngeal region. Detailed deposition information from the turbinate region indicated that deposition was high toward the anterior portion where most deposition was concentrated on the inferior meatus. Spray droplets were also deposited in spots of the middle and posterior portions of the turbinate region, and this nonuniform deposition pattern may be correlated with the flow pattern. The spray angle and droplet size of the nasal spray were found to be important in influencing the deposition pattern in the nasal airway. The droplet size was determined by a laser-diffraction technique and the spray angle by high-speed photography. Larger droplets and a wider spray angle increased deposition in the anterior region of the nasal airway, which prevented more material from depositing in the turbinate region.
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