Understanding Air Pollution - Criteria Air Pollutants
You don’t have to live next to a factory to be affected by air pollution. The most common forms of air pollution can travel, linger, and build up in ways that might surprise you, even when the sky looks clear. This article covers which air pollutants are most common and where you might encounter them on a daily basis, giving you the knowledge you need to make informed decisions about your health.
Criteria Air Pollutants
Air quality is a term used to describe the composition of the air. You might've heard people talk about air quality as being good or bad. What they're talking about when they say that is the amount of pollutants present in the air. Air pollutants, the topic of this article, are the harmful substances that are present in the air. When there is less air pollution, air quality is good. When there is more air pollution, air quality is bad, put very plainly.
There are a large number of air pollutants present on the Earth, and they are not universal, so it's hard to say which ones may be affecting you. One type of air pollutant may be a large issue in a specific area, but not a huge concern anywhere else. However, some air pollutants are much more common than others. The United States Environmental Protection Agency (EPA) classifies six air pollutants as being the most commonly found, labeling them as criteria air pollutants.
Those pollutants are:
- Ozone (O3) is a highly reactive gas. When it's high up in the atmosphere, it protects us from the Sun's harmful UV rays. But when it's down near the ground, it can cause a variety of health problems.
- Particulate Matter (PM) refers to the blend of solid particles and liquid droplets that float around in the air. The size of those particles affects how deep into your lungs they penetrate.
- Carbon Monixide (CO) is a gas you can’t see or smell. It’s produced when things burn, like fuel or wood, and breathing in too much of it can be dangerous because it keeps your body from getting enough oxygen.
- Lead (Pb) is a naturally occurring metal that many people associate with older paints or pipes, but it can also exist in the air as a pollutant. When present in the air, lead is a serious health concern, which is why it’s closely regulated nowadays.
- Sulfur Dioxide (SO2) is a harmful gas that has negative health effects. It's used as an indicator pollutant, which means if sulfur dioxide is present, other sulfur oxides might also be present.
- Nitrogen Dioxide (NO2) is a gaseous pollutant that can affect respiratory health. It is also used as an indicator pollutant for the larger nitrogen oxide family.
These pollutants are labled as being the most common, but that does not mean other air pollutants aren't critical to consider from region to region.
How These Pollutants Affect our Everyday Lives
These pollutants affect us in our everyday lives, whether we realize it or not. Symptoms like a mystery headache or a sudden cough may be due to air pollution exposure. Actively considering what you may be exposed to, and where that can commonly happen, allows you to proactively safeguard your health.
Common Symptoms of Air Pollution Exposure
While each causes some distinct health effects, ozone, particulate matter, sulfur dioxide, and nitrogen dioxide all also share a significant number of short-term effects. All four can:
- Aggravate asthma.
- Cause diffculty breathing.
- Result in a sudden cough.
In addition to the above, Ozone is known to cause a burning sensation in the lungs after a workout, and PM can result in an irregular heartbeat.
On the other hand, carbon monoxide and lead are a bit different. CO is primarily a concern indoors in poorly ventilated or unventilated spaces. This is becasue CO reduces the amount of oxygen your body is able to transport. If you are present in an unventilated space where there is a buildup of CO, you can experience dizziness, confusion, unconsciousness, or even death if not transported out.
Airborne lead used to be a much larger air quality issue becasue of its inclusion in motor vehichle gasoline. But, becasue of the EPA's regulatory efforts, the "levels of lead in the air decreased by 98 percent between 1980 and 2014." However, it can still be found in some areas. Unlike some of the other criteria pollutants, lead is more commonly associated with long-term health issues affecting the nervous system, kidney function, immune system, reproductive and developmental systems, and the cardiovascular system.
The above information was sourced from various US EPA informational website pages.
Common Encounters with Air Pollution
There are many everyday scenarios in which you might encounter some of these pollutants. As you go about your day-to-day life, it's important to keep these situations in mind so that you can make decisions for your health.
Here are some common scenarios:
- During Morning Commutes or Errands, you can be exposed to PM, CO, NO2, and even O3. These criteria pollutants are commonly found near major roadways because they are either directly emitted by motor vehichles, or formed from those emissions (Research on Near Roadway and Other Near Source Air Pollution).
- When Exercising Outdoors, you breathe in large amounts of any pollutant in the air. Typically, this is PM or Ozone, especially on hot summer days (Health Effects of Ozone and Particulate Matter).
- In Your Workplace or Other Indoor Spaces, air quality can often reflect outdoor conditions, as well as anything that may be happening inside. The biggest culprit here is PM, although there are CO considerations to be made becasue of the indoor environment (Introduction to Indoor Air Quality).
- When Traveling Through Industrial Areas, you can be exposed to pollutants that are offput by manufacturing facilities, factories, or other industrial activities. These have the potential to offput PM, SO2, NO2, and even lead (Air Pollution Emissions Overview).
Air pollution isn’t something that only affects people living near factories or obvious smoke. Because pollutants can travel, linger, and build up, even under clear skies, understanding what’s in the air around you matters for everyday health. The EPA’s six criteria pollutants—ozone, particulate matter, carbon monoxide, lead, sulfur dioxide, and nitrogen dioxide—are the most common drivers of poor air quality, and each comes with its own risks. Some can cause immediate symptoms like coughing, breathing trouble, or asthma complications, while others contribute to longer-term issues.
Most importantly, these pollutants show up in normal parts of life: commuting, exercising outside, spending time indoors, or traveling through industrial areas. By knowing what these pollutants are and recognizing when you’re most likely to encounter them, you’re better equipped to check air quality, adjust your routines when needed, and make informed choices that protect your health day-to-day.