Ultrafine particulate matter (UFP) has been a concern of industrial hygienists, air pollution control engineers, and public health professionals since the beginning of the 21st century. But these small particles, generally defined as those with a diameter of less than 0.1 micrometers (µm) or 100 nanometers (nm), have been with us for millennia. UFPs range from woodfire smoke and airborne viruses to emissions from advanced materials and technologies such as 3D printing, plasma cutting, and engineered nanomaterials.
UFP are present in ambient air both indoors and outdoors from natural and anthropogenic sources. Particle formation mechanisms include nucleation of gas-phase compounds with low volatility—for example, ammonia, sulfuric acid, and some volatile organic compounds (VOCs)—in the upper atmosphere. UFP can also form and grow through coagulation and condensation. As our subtitle states, you can run, but you can’t hide from unidentified flying particles.
