Air Quality 101

Air Quality refers to the characteristics of the air that surrounds us. Generally, good air quality refers to clean, clear air that is free of added pollution. Poor air quality can result from various factors including emissions from industry, vehicles, wood smoke (forest fires and wood stoves) and natural sources. Air quality is compromised when pollutants increase enough to endanger human health and/or the environment (soil, water, vegetation and wildlife). For information about the health impacts of air pollution click here.

Outdoor Air Quality

Otherwise known as "ambient" air quality, this refers to the quality of outdoor air. It is typically measured near ground level, away from direct sources of pollution. In Kamloops it has historically been measured in the valley bottom, although recently the Ministry of the Environment has moved to establish air quality monitoring in Aberdeen and Knutsford. It is possible that the highest level of pollution concentration may not be in the valley bottom in Kamloops, rather, it may be at the level of the inversion layer (Sahali and Lower Aberdeen).

Indoor Air Quality

Indoor air can also contain pollution that has seeped in from outside or that has been emitted from indoor sources. Some common examples of indoor sources of air pollution are tobacco smoke, mould, and chemicals released from synthetic fabrics, furnishings and household products.

Local Factors Influencing Air Pollution

The local terrain has a direct impact on air quality. In Kamloops, a large part of the city is in a mountain valley. This means that we have periods of time when the air pollution is trapped in the valley due to temperature inversions.

Inversion in a valley

Weather also influences air quality. Wind, temperature, turbulence, pressure, rainfall and cloud cover all influence how much pollution exists in any given location.

What types of pollutants are present also influences air quality. Some types of pollution stay suspended in the air much longer than other types of air pollution.

Point sources of pollution contribute to overall air quality. On the "Air Health BC" website they use the following example:

"Let's consider an analogy using water to help explain how air and air emissions behave. Imagine pouring red dye into the ocean. You'll see a red pool of water for a few seconds, but it quickly disappears as the waves mix the dye into the huge mass of water. It is a combination of the amount of water, and the vigorous mixing that makes the dye disappear.

Now imagine pouring that same amount of red dye into a bathtub. The bath water will turn very red because there is far less water than in the ocean, and there is no mixing with a source of clean water to dilute the dye. Just as red dye disappears in the ocean, air pollutants mix and disperse quickly in a large airshed because the air flow is not limited by topography but can travel and mix over great distances. This results in good air quality in the airshed.

Sometimes, however, topography and weather combine to prevent pollutants from mixing and dispersing. In this case the pollutants become trapped within the area, like the red dye in the bathtub that continually builds up with nowhere to go. This results in poor air quality in the airshed."

Kamloops is located in a valley that formed along the Thompson Rivers. This has an influence on how much mixing takes place.

Sometimes, in valleys like Kamloops, the atmosphere is very still. This occurs when the air near the surface of the earth is cooler than the air above and is referred to as a temperature inversion. The trapped, cool air does not move up to mix with the warmer air above. Any pollutants released near the surface will get trapped and build up in the cooler layer of air near the surface. Temperature inversions are common throughout the valley terrain in BC and are common in Kamloops. They often form during calm clear nights with light winds, and they can persist throughout the day during the winter.

A Temperature Inversion in a Valley (from air health BC website)

Point Sources

The number and size of emission sources in our area, along with weather conditions and topography, will determine the level of pollutants in our air. Natural sources of pollution also influence our air quality.

Degraded Air Quality

Air quality is considered "degraded" when pollution is released into the air in large enough amounts to harm the health of people and the environment. The quality of the air depends on the amount of pollutants, the rate at which they are released, and how quickly the pollutants disperse (or, conversely, how long they are trapped in an area).

There are many different types of air pollution. Some are gases or vapours, some are tiny solid particles, and some are larger particles. We can't readily control the natural sources of air pollution, so air pollution management largely involves regulation and control of point sources and things that can be modified like vehicle emissions and wood stove use.

Air pollution terminology

Particulate Matter refers to the substances floating around in the air. Most of these substances are so small they are not visible. In fact, particulate matter that we can't see is the air pollutant that most commonly impacts human health.

Particles can come in almost any shape or size, and can be solid particles or liquid droplets. The particles can be divided into several major groups. These groups differ in several ways. One of the differences is size. The bigger particles are called PM10 and the smaller particles are called PM2.5.

PM 10 refers to the particles which are smaller than 10 micrometres (smaller than 25 times thinner than a human hair). These particles impact health, but are thought to cause less severe health impacts than PM 2.5.

PM 2.5 refers to the particles that are smaller than 2.5 micrometres in size(100 times thinner than a human hair). This type of pollution has been implicated in various human health impacts.

You can see a comprehensive list of the impacts of air pollution on human health here

Nanoparticles or Ultrafine particles are even smaller than most of the particles included in the PM2.5 category. The research on nanoparticles is just beginning to emerge, but it is suspected that this type of air pollution may have different health implications than the other categories of air pollution.

Ultrafine PM can directly enter the brain through the membranes in the nose without going through the blood stream; one example of this is gold which can enter the brain directly and disrupt the tissue protection barriers in the brain. Some heavy metals are more likely to attach to very small particulate.

Smaller particles are lighter, so they stay in the air longer and travel farther. PM10 particles can stay in the air for minutes or hours while PM2.5 (small) particles can stay in the air for days or weeks. These particles can travel far from their source. PM10 particles can travel as little as a hundred meters, or as far as 50 kilometers. PM2.5 particles travel even farther - sometimes many hundreds of kilometers.


1. Particulate matter enters our respiratory (lung) system through the nose and throat.

2|3. The larger particulate matter (PM10) is trapped in mucous and then is largely eliminated through coughing, sneezing and swallowing.

4. PM2.5 can penetrate deep into the lungs. It can travel all the way to the alveoli, causing lung and heart problems, and delivery harmful chemicals to the blood system.

Health Impacts

When you inhale, you breathe in air along with any particles that are in the air. The air and the particles travel into your lungs and airways. Along the way the particles can stick to the sides of the airway or travel deeper into the lungs.

The farther particles go, the more serious the health effects.

Smaller particles can pass through smaller airways. Bigger particles are more likely to stick to the sides of the airways or get wedged into one of the narrow passages deep in the lung.

Other factors that affect how deep into the lungs particles can go:

In response to the air pollution that you inhale, your lungs produce mucous to trap the particles, and tiny hairs wiggle to move the mucous and particles out of the lung. You may notice this mucous in the back of your throat; the mucous is cleared by coughing or swallowing. If the particle is small and it gets very far into the lungs, the particles can't get out and this can result in many health problems.

Health Effects

Both PM10 (big) and PM2.5 (small) particles can cause health problems; specifically respiratory health (that's the lungs and airway). Because the PM2.5 travels deeper into the lungs AND because the PM2.5 is made up things that are more toxic (like heavy metals and cancer causing organic compounds), PM2.5 can have worse health effects than the bigger PM10.

Acute exposure to particulate matter leads to increased use of medication and more visits to the doctor or emergency room. Health effects include the following:

For more details on health impacts of air pollution please click here

For more information:

General information on air quality:

Background information on air quality in Kamloops (references are prior to 2007) from the city of Kamloops website:

Information on air quality's impact on children's health: