Although mostly invisible to the naked eye, the air we breathe is full of tiny particles of chemicals, soil, smoke, dust or allergens, in the form of liquids, gases or solids. When we burn fossil fuels for energy use and production, gases and chemicals are released that pollute the air, posing a risk to human health and the planet as a whole. These minuscule airborne hazards are referred to as particulate matter, or PM.
Where does PM come from?
The amount of particulate matter in the air at any given time depends on the environment you find yourself in. These particles are released from a variety of sources both indoors and outdoors. When inside, PM levels are typically the same or lower than outside.
Here are a few things that increase the levels of particulate matter floating around an indoor space:
- burning candles or fires
- using kerosene heaters
- diffusing essential oils
- cleaning using common chemical products
- opening doors and windows to outdoor polluted environments
- using hairsprays, aerosol room freshers or deodorants
Although there are hundreds of sources of outdoor air pollutants, the main contributors that increase the levels of particulate matter outdoors are:
- power generators
- industrial and agricultural emissions
- residential heating and cooking
- the manufacture and distribution of chemicals
- forrest fires
Why is it called PM 2.5?
The 2.5 in PM 2.5 refers to the size of the pollutant in micrometers. Bear with us here while it gets a bit mathematics-y! Micrometers have this symbol: µm and are equivalent to 0.001 millimeters. The smallest thing that the average human eye can perceive is about 0.1 millimeters, which is around the same width as a human hair. So in order for us to see something as incredibly small as a micrometer, we need to use powerful microscopes. Here’s a diagram from the Environmental Protection Agency to help you visualize the scale of these tiny particles.
While it is obvious that breathing in any particles in the air is going to aggravate your airways, experts are particularly worried about the extremely small particles such as PM 2.5 as they not only penetrate deep into our lungs but are also so minute that they can even pass into our bloodstream.
What are the negative effects of exposure to PM 2.5?
Depending on how healthy you are in general, PM 2.5 will have different long and short term negative health effects. When exposed to levels of PM 2.5 between to moderate – hazardous range, one may experience the following effects:
- shortness of breath
- eye, nose and throat irritation
- excessive coughing and wheezing
- diminished lung function and lung disease
- diminished heart function, sometimes resulting in heart attack
- asthma attacks
PM 2.5 also damages the environment by increasing acidity in the soil and water bodies, which in turn affects their ability to produce food and support life.
What is considered a safe level of PM and how is it measured?
Pollution levels are generally measured on a scale of 0-500 called an Air Quality Index, or AQI:
Even at moderate levels, particulate matter can still be harmful to sensitive people. When air pollution levels are lower, the cardiovascular and respiratory health of a person will be much improved, both long and short term.
Governments measure levels of PM 2.5 using beta attenuation monitors (BAM), which look like this:
The top tube of the instrument separates the smaller particles like PM 2.5 from larger particles such as PM 10. Just as you suck air through your mouth and into your lungs, an internal pump pulls a large volume of air through the inlet head at the top. The smaller particles get sucked down onto filter tape at the base section of the machine. Analysts measure the number of particles drawn onto the filter tape and this shows what the level of PM 2.5 is in the surrounding air. The New Hampshire Department of Environmental Services published this picture of PM 2.5 staining the BAM filter tape after a pollution monitoring session. Each circle represents an hour of particle collection – pretty nasty looking stuff when you imagine it stuck to your lungs not just filter tape.
Exactly How bad is PM 2.5 in different parts of the world?
The internet is a treasure trove for real time data on air quality around the world and there are a few sites such as Berkeley Earth or AQICN, which both show detailed maps describing particulate matter air pollution less than 2.5 microns in diameter constructed from thousands of surface station measurements from around the world.
As of the Words Heath Organisation’s extensive studies, here are a list of the best and worst nations for air pollution around the world in 2017. All units displayed in this table represent levels of PM 2.5.