Comparative lung toxicity of size-fractionated cyanobacterial PM
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The global expansion of harmful algal blooms (HABs) poses an increasing threat to public health. While the aerosolization of toxins from marine HABs (red algae) have been well documented, little information is available on the inhalation of aerosolized cyanotoxins in association with particulate matter (PM) in freshwater systems and their subsequent health outcomes. Thus, it is important to determine whether aquatic cyanobacteria can be aerosolized and how inhaled cyanobacterial PM affects the lungs. In this study, we collected size-fractionated PM (fine and coarse) from three different freshwater lake/rivers during periods of rapid HAB growth: Chowan River, North Carolina (NC Coarse and NC Fine), Lake Erie, Ohio (OH Coarse and OH Fine), and Discovery Bay and Stockton, California (DB Coarse and ST Coarse). PM samples were chemically analyzed and assessed for lung toxicity and lung function in CD-1 mice via oropharyngeal aspiration (100 µg of PM). Results showed that coarse PM had relatively higher organic carbon and inorganic element contents than fine PM. On an equal mass basis, DB Coarse and OH Coarse had the highest microcystin content and elicited the greatest pro-inflammatory responses in the lungs (neutrophil influx, increased protein and cytokine levels) and significantly reduced lung function (increase in airflow obstruction) at 4 and 24 h post-exposure. NC Coarse and OH Fine significantly increased lung inflammation at 4 h post-exposure but other biological and physiological endpoints remained unchanged. NC Fine and ST Coarse had the lowest microcystin content and increased (but not significantly) cytokine levels and did not change lung function at either 4 or 24 h time point. These results show that HAB aerosols from freshwater systems can generate contrasting chemical and cyanotoxin spectra depending on their size fraction and inhalation of airborne cyanobacteria and PM mixtures can cause acute respiratory problems. Our findings can be used to fill a gap in current HAB knowledge and public safety education.