There are 2 classes of PM– PM2.5 and PM10. Simply put, PM10 refers to PM 10 microns or less, while PM2.5 refers to PM 2.5 microns or less.
PM2.5 is usually emitted from the combustion of fuels and wood, while PM10 is typically dust produced from construction sites, wildfires and industrial sources. PM10 is likely to be deposited on the upper surfaces of the lungs whereas PM2.5 could travel deeper into the lungs. Both PMs can be found in haze and are used in PSI tracking, but PM2.5 is the main pollutant of concern as they can infiltrate air-conditioned buildings through the air intake, openings and gaps, jeopardising the health of people staying indoors.
So what happens when we are exposed to PM10 or PM2.5? Short-term exposure to PM10 has been associated primarily with the worsening of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD), leading to hospitalisation and emergency department visits. Long-term (months to years) exposure to PM2.5 has been linked to premature death, particularly in people who have chronic heart or lung diseases, and reduced lung function growth in children. Collectively, PM2.5 and PM10 have been associated with premature mortality, irregular heartbeat, worsened asthma and aggravated respiratory symptoms such as coughing, wheezing and breathing difficulties. So now, how does one protect oneself against the health impacts of haze?
If the 24-hour PSI reaches unhealthy levels (101 and above), individuals with chronic lung or heart disease should avoid prolonged or strenuous exercises outdoors. Seniors, pregnant women and children should minimise outdoor exertion. If the one-hour PM2.5 concentration reaches elevated levels, healthy people should reduce strenuous outdoor activities, while vulnerable people should avoid such activities.