Particulate matter (PM) 懸浮粒子
Particulate matter represents a complex mixture of small particles and liquid droplets suspended in the air. Major sources of particulate matter include construction activities, road dust re-suspension and combustion.
Particulate matter with aerodynamic diameter smaller than 10 micrometres (μm) (PM10) is already small enough to pass through nose and respiratory tract and enter our lungs. Chronic exposure to particulate matter increases the risk of cardiovascular and respiratory diseases, or even lung cancer. Those particulate matter smaller than 2.5 μm (PM2.5), also known as fine suspended particles, is especially harmful. It is one of the most important parameters for air pollution monitoring.
In Hong Kong, Air Quality Health Index (AQHI) was introduced to replace the late Air Pollution Index in December 2013 from Environmental Protection Department, HKSAR. Individuals with lung and heart disease, influenza, asthma, elderly people and children are sensitive to PM. They are advised to reduce physical exertion and outdoor activities and avoid prolonged stay in areas with heavy traffic when AQHI is at high health risk category or higher.