Microscopic, pollutive particles of solid or liquid matter that circulate in the Earth’s atmosphere, and in human and animal bodies through inhalation (see Murphy; Prieto; and Sobecka). Particulate sources vary, from the natural to human-made, including vehicle emissions, dust storms, volcanoes, and power plants (see Canada’s Waste Flow). This term may also describe the nearly invisible plastic particles (termed microplastics) circulating in bodies of water throughout the globe (see Shear).