What level of ultrafine particles is harmful?
For many years, experts have known that very small particles called ultrafines (less than 0.1 micron in diameter) acted much like a gas dispersing evenly into a given volume. They also believed that these tiny particles were freely inhaled and exhaled offering little threat to human health. Recent research indicates that ultrafine particles (UFPs) are, in fact, retained in the alveolar regions of the lungs. Ultrafine particles are present in very large quantities in a given volume of air, 86% in terms of count while less than 1% of the mass of particulates. There is growing evidence that the shear numbers of UFPs being inhaled and retained overwhelms the natural mechanisms by which our bodies rid themselves of these tiny particles. Research focused on but not limited to clarifying characteristics, exposure effects and behavior of UFPs is being conducted by a number of regulatory organizations. This research suggests that there may be some adverse health effects associated with UFP expo
