Particulate Matter: PM2.5 vs PM10
What is Particulate Matter?
There are several reasons why a lot of our pollution and stressor work at Centric Lab involves the data and science around particulate matter (PM). The term particulate refers to a group of particles. PM is everything in the air that isn’t a gas, such as dirt, dust, soot, smoke, drops of liquid, or any combination of these.
While PM is present in many places, it only takes low concentrations to start having health impacts. No threshold has been identified below which no damage to health is observed, it’s more a case of volume and exposure that determines how long it will take for the particulate pollution to affect your health. Therefore, the WHO Global guideline limits aimed to achieve the lowest concentrations of PM possible. Any amount above 0 is to account for the inevitable activities such as transport and construction that will contribute to particulate pollution in any environment.
When you see the terms PM2.5 and PM10, the numbers in their names (PM2.5 and PM10) refer to the largest diameter in microns (aka micrometres) of particles in that particulate matter. So PM10 has particles with a diameter of up to 10 microns. This means that all PM2.5 particles also count as PM10 particles. Because of this, the guidelines for acceptable levels of PM10 will usually be higher than PM2.5 when you look at 24-hour and annual recommendations from organisations like the WHO. What makes PM2.5 more specifically dangerous (and the common pollutant associated with the greatest proportion of adverse health effects related to air pollution based on the WHO’s Global Burden of Disease Project) is that this diameter is small enough that particles can get deeper into the lungs, eventually ending in the bloodstream and causing inflammation, while the larger particles of PM10 tend to stay more respiratory.
Short and Long Term Effects
If we look at the short term effects, exposures up to 24-hours duration are associated with premature mortality, increased hospital admissions for heart or lung causes, acute and chronic bronchitis, asthma attacks, emergency room visits, respiratory symptoms, and restricted activity days. In comparison, short-term exposures to PM10 are associated with the worsening of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD), leading to hospitalisation and emergency department visits.
If we look at long term effects, PM2.5 can increase the likelihood of premature death, particularly in already vulnerable populations such as children, the elderly, asthmatic people, and people with chronic heart or lung diseases. The effects of long-term exposure to PM10 are less clear than we’ve found for PM2.5, although studies suggest a link between long term PM10 exposure and respiratory mortality.
Sources
Emissions from combustion of gasoline, oil, diesel fuel or wood produce much of the PM2.5 pollution found in outdoor air, as well as a significant proportion of PM10. This is why maps and models often show high values around roads, factories, and high transport areas. PM10 has all the sources of PM2.5 yet includes dust from construction sites, landfills and agriculture, wildfires and brush/waste burning, industrial sources, wind-blown dust from open lands, pollen and fragments of bacteria.
What to Look Out For
If you have concerns around particulate matter from local activities such as high traffic and construction, both PM2.5 and PM10 should be investigated in addition to your usual suspects, such as CO2. While it’s common to investigate particulate matter when there are respiratory issues, the long term effects of the smaller PM2.5 particles mean that people can experience much deeper and dangerous symptoms affecting the heart and the brain. But ultimately, individual citizens aren’t responsible for the majority of the causes and emitters of particulate matter as the sources are systemic. Therefore, the solutions are systemic and involve holding the bigger infrastructure accountable.
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