When understanding Air Quality standards you’ll see acronyms such as PM2.5 being used. These are classifications of Particulate Matter (PM) accompanied by a number displayed, usually in subscript text, this number describes the size of particles, for example PM10 denotes particles with a diameter of 10 micrometres (10µm) or less [1], or PM1 with an even smaller diameter of 1 micrometres or less.
µm
A micron or micrometre is used to analyse very small particles. The symbol for micrometres is “µm”,which is a length of measurement equal to one millionth of a metre. (1,000µm is equal to 1mm.)
ABOVE Particle size comparison
PM2.5 is generally described as fine particles. By way of comparison, a human hair is about 100 micrometres (100µm), so roughly 40 fine particles (100 ÷ 2.5) could be placed on its width.
Every reduction in Particulate Matter (PM) size presents a greater risk to health, the smaller the particles the further they travel into the human anatomy. Particles that are 0.1 microns and smaller may enter the bloodstream and have been linked to negative health effects throughout the body such as cancer, dementia, multiple sclerosis, and even diabetes.[3]
ABOVE The smaller the matter, the greater the damage
What are the associated health risks when Particulate Matter is inhaled?
- Respiratory Issues: PM can penetrate deep into the lungs, causing respiratory problems such as aggravated asthma, bronchitis, and reduced lung function. Fine particles, particularly those smaller than 2.5 micrometres (PM2.5), can reach the deepest parts of the lungs and even enter the bloodstream.
- Cardiovascular Effects: Exposure to PM is linked to cardiovascular diseases, including heart attacks, strokes, and irregular heart rhythms. Fine particles can cause inflammation, oxidative stress, and vasoconstriction, leading to cardiovascular problems.
- Increased Mortality: Long-term exposure to high levels of PM is associated with an increased risk of premature death, particularly from cardiovascular and respiratory diseases. Studies have shown a correlation between elevated PM levels and higher mortality rates in both urban and rural areas.
- Cancer: Some studies suggest that long-term exposure to certain types of PM, particularly those containing heavy metals and polycyclic aromatic hydrocarbons (PAHs), may increase the risk of lung cancer.
- Neurological Effects: Recent research indicates that PM exposure may have neurological effects, including cognitive decline and an increased risk of neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Fine particles can enter the brain through the olfactory nerve or systemic circulation, causing inflammation and oxidative stress in the brain tissue.
- Reproductive and Developmental Effects: Exposure to PM during pregnancy may increase the risk of adverse birth outcomes such as low birth weight, preterm birth, and developmental disorders in children. PM can cross the placental barrier and affect foetal development, leading to long-term health consequences.
These health risks are supported by a considerable body of scientific evidence, including epidemiological studies, toxicological research, and mechanistic studies elucidating the biological pathways through which PM exerts its effects.
What are the Sources of Particulate Matter?
Particulate matter can originate from a variety of sources, which includes:
Outdoor air: vehicle exhaust, wildfire smoke, road dust, pollen, mining operations, agricultural activities, and factory emissions. Outdoor particulate matter, also known as particle pollution, can enter buildings through windows, doors, ventilation (HVAC) systems, and small cracks and crevices.
Biological Sources: mould spores, dust mites, pests.
Combustion Activities: smoking vapes or tobacco, burning candles or incense, and using fireplaces, oil furnaces, and fuel-burning space heaters
Consumable Products: some cleaning products, air fresheners, oil diffusers, and aerosol sprays
Industrial Activities: woodworking, metalworking, printing, and activities including glues and adhesives
ABOVE Biological Sources, Combustion Activities, Consumable Products, Outdoor air all contribute to particulate matter levels
How do we minimise exposure to Particulate Matter in Indoor Environments?
- Follow the AS3666 standard for the regular maintenance and inspection of HVAC systems and ductwork, AHUs, Coils and ventilation components
- Use air cleaners, or air purification systems, such as germicidal UVC to sterilise air as it passes through HVAC systems.
- Conduct regularly microbial testing for mould and bacteria colonies, remediate to IICRC S520 standard if mould issues are present
- Reduce outside air when outdoor PM levels are high
- Never use unvented fuel-burning stoves, fireplaces or space heaters indoors
- Increase ventilation: Install and use exhaust fans where appropriate
What are safe PM standards and guidelines?
There is no safe limit for fine particles. Particulate matter (PM) less than 1 micron in size, PM1 (sometimes PM1.0) is considered especially dangerous due to its extremely small size.
The smaller the diameter of a particle, the more harm it can typically cause. Tiny airborne particles like PM1 are small enough to penetrate lung tissue and get into the bloodstream. PM1 can then circulate throughout the body and cause systemic health effects. [5]
Exposure to no more than 15μg/m3 of PM2.5 over a 24 hr period
Exposure to no more than 45μg/m3 of PM10 over a 24 hr period
(air containing 45 micrograms of pm10 per cubic metre)
According to the new recommendations from WHO, exposure to the concentrations of PM2.5 fine particles should be less than 5 μg/m3 as an annual average, and less than 15 μg/m3 as a 24-hour average.
Exposure to the concentrations of PM10 coarse particles should be less than 15 μg/m3 as an annual average, and less than 45 μg/m3 as a 24-hour average.
However, a safe limit for fine particles has not been determined, they are always a health risk.
SOURCE World Health Organization (WHO) Air Quality Guidelines, Recommended exposure over a 24hr time period.
According to European Environment Agency fine particulate matter concentrations higher than WHO recommendation resulted in 238,000 premature deaths in the European Union in 2022.
WHO Recommended 2021 AQG levels
Pollutant | Time | μg/m3 |
PM2.5 | Annual | 5 |
PM2.5 | 24 hr | 15 |
PM10 | Annual | 15 |
PM10 | 24 hr | 45 |
O3 | Peak Season# | 60 |
O3 | 8 hr | 100 |
NO2 | Annual | 10 |
NO2 | 24 hr | 25 |
SO2 | 24 hr | 40 |
CO, mg/m3 | 24 hr | 4 |
# Average of daily maximum 8-hour mean O3 concentration in the six consecutive months with the highest six-month running- average O3 concentration. Note: Annual and peak season is long-term exposure, while 24 hour and 8 hour is a short-term exposure
Visit the WHO Website for more information on their Air Quality Guidelines
Summary
Particulate Matter (PM) refers to tiny particles in the air, classified by size, such as PM2.5 and PM10, which denote particles with diameters of 2.5 micrometres and 10 micrometres or less, respectively. These particles come from various sources, including biological materials, combustion activities, consumable products, industrial processes, and outdoor pollution. Smaller particles pose greater health risks as they can penetrate deep into the lungs and enter the bloodstream, leading to respiratory and cardiovascular issues, increased mortality, cancer, neurological effects, and adverse reproductive outcomes. To minimise indoor PM exposure, it is recommended to maintain HVAC systems, use air purifiers, conduct microbial testing, and increase ventilation. There is no safe limit for fine particles, with the WHO setting strict guidelines for PM2.5 and PM10 exposure levels.
References
[1]https://www.health.nsw.gov.au/environment/air/Pages/particulate-matter.aspx#:~:text=The%20size%20of%20particles%20affects,and%20cause%20serious%20health%20effects. https://www.mdpi.com/2673-527X/3/1/3#:~:text=3.3.-,Particle%20Sizes,22%2C23%2C24%5D. [2] https://www.safera.com/fine-particles-pm25-are-significant-health-risk/ [3] https://www.dcceew.gov.au/environment/protection/npi/substances/fact-sheets/particulate-matter-pm10-and-pm25#:~:text=Description,be%20placed%20on%20its%20width. [5] https://www.iqair.com/au/newsroom/pm1 [6] https://www.facebook.com/WHO/photos/a.750907108288008/4693957043982975/?type=3
Pope CA 3rd, Dockery DW. Health effects of fine particulate air pollution: lines that connect. J Air Waste Manag Assoc. 2006;56(6):709-742. | Brook RD, Rajagopalan S, Pope CA 3rd, et al. Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association. Circulation. 2010;121(21):2331-2378. | GBD 2019 Risk Factors Collaborators. Global burden of 87 risk factors in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019. Lancet. 2020;396(10258):1223-1249.