Air Pollution and Particle Size

By Adrien Lafond

People knew that poor air quality induced human diseases and other problems since antiquity, but it was not until recently that the adverse health effects of air pollution became a household term. Only in the past few decades did we learn about how air pollution, and particulate matter can do to our bodies.

What is Particulate Matter?

Particle pollution refers to any mix of tiny solid or liquid particles floating in the air we breathe. Also called particulate matter (PM), these microscopic particles come in various sizes, chemical composition, and other environmental factors. They are normally too small for us to see, but can become opaque when they reach a high enough saturation in the environment. This sounds simple, but nothing about airborne particles pollution is simple. They can combine with nitrogen and volatile organic compounds to create respiratory problems and other adverse health risks.

The air quality around us always contains some pollution. At any time of the day, we could be breathing in any number of acids, nitrogen oxides, volatile organic and inorganic compounds, biological materials, metals, soil or dust, and allergens such as pollen or mold spores. Some of these pollution is large enough to be visible with the naked eye. Others are so small you need an electron microscope to see them. They come from combustion, human and animal shedding, and other sources. They then mix with liquid droplets and get suspended in the air. They become health risks when they reach enough saturation to cause health issues.

Particle Sizes and Effects

While they all look the same on a macroscopic level, the particles themselves come in different sizes. Some are smaller than a strand of hair, but most of the more volatile ones are much, much smaller. These size differences contribute to how each type of particle interacts and affects our health. For instance, our bodies can readily deal with most of the larger particles. We just cough or sneeze to get them out. Our throat and lungs act as a filter, therefore the larger particles cannot enter deeply in our bodies. However, there are particles out there for which we have no defenses against. These particles can either get trapped in our lung or make it through to our bloodstream.

The US EPA and researchers group the various particles in three broad categories.

The categories of airborne particulate include:

Coarse particles (PM10) - These are the largest particle, such as wind-blown dust., ranging from 2.5 to 10 microns in aerodynamic diameter. Most of it is stopped by our lungs.
Fine particles (PM2.5) - Most particles that can adversely affect our health fall under the fine category. These particles have diameters that are at least 2.5 microns or smaller. This includes stuff like smoke and haze.
Ultrafine particles (PM1) - The smallest of the particles, these things have diameters that are smaller than 100 nanometers in size. Ultrafine particles can pass through any lung tissue right into the bloodstream. From there, they can circulate throughout your body along with your blood cells and oxygen. The exact effects of these PM1 on human health remain unknown, as there are much less studies about these.

However, because these particles can come from a number of sources, they often come with the different sizes mixed together. Some of them can even exist as liquids or liquid-suspended solids.

You will also find different types of particles floating in the air depending on where you live and the time of the year. For example, Sulfur dioxide and other sulfates are common in the Midwest, Southeast, and Northeast states. On the other hand, the Northeast, Southern California, the Northwest and North Central U.S often have high levels of nitrate and other organic particles during the winter.

Health Effects of Particulate Exposure

With all the buzz surrounding particle pollution, it is surprising that very little is known about it. Most research focuses on fine particles. There are currently no studies on the effects of the ultrafine and coarse airborne particulates. Even within the limited research, we do not have precise ways to distinguish between the particles effects. Because of this, the National Particle Component Toxicity (NPACZT) program concluded that all particles affect your health in some way.

Even without the research, we do know that all particulate matter has adverse health effects. In particular, the size of the particle often determines what it will do to you.

Particles less than 10 micrometers are the worst offenders. They can get deep into your lungs. Some can even get into your bloodstream. Larger particles can still irritate your eyes, nose, and throat as well.

Regardless of the size, particulate matter can damage both your lungs and heart leading to such health problems as:

Heart disease
Chronic lung diseases
Heart attacks
Irregular heartbeat
Aggravated asthma
Decreased lung function
Blood clots and other changes to blood chemistry
Premature death
Lung irritation, leading to increased lung tissue permeability
Increases susceptibility to viral and bacterial infections
Increased respiratory symptoms including irritated airways, coughing or difficulty breathing

If you already suffer from a heart or lung disease, particle pollution exposure will enhance these issues.

Particulate Matter Risk Factors

While particle pollution can affect even healthy people, if you have heart or lung disease or diabetes, you will still have a higher risk for severe complications from the exposure that may require hospital admission. Older adults and children are also at risk. It gets even worse if you are physically active. Exercise and physical activity cause you to breathe faster and more deeply, which draws more particles into your lungs.

Signs that you may have been exposed can be noticed if you experience any one of the following problems:

Eye, nose, or throat irritation
Coughing
Phlegm
Chest tightness and discomfort
Unusual fatigue
Shortness of Breath

While government agencies, health organizations, and many industries are trying to reduce particle pollution, the pollution is likely to stick around for a while. As the effects of particulate matter increase with strenuous activity and the duration of exposure, you can prevent prolonged exposure by limiting or discontinuing any planned activity or heavy exertion during times of elevated risk. You can also plan these things around them if the National Parks Service (NPS) and the Environmental Protection Agency (EPA) can forecast them in advance. These agencies will provide warnings if the air quality in your area reaches certain thresholds. Each threshold defines when different adverse health effects become more likely in the individuals that the most as risk.

All air pollution is harmful. Size just affects the severity of it.

Particulate pollution comes in all shapes and sizes, but is generally grouped into three categories: coarse, fine, and ultrafine. Each category I defined by a certain range of diameter sizes regardless of their composition. They can all damage our lungs, though they have different adverse effects. While our bodies can ward off most coarse grains, we have no protection against anything smaller or the VOCs that often come with them. Some semi volatile organic compounds can even pass through our lungs and enter our blood to effect other parts of our bodies, including our brains. If you’re not suffering from respiratory problems, it might not have visible effects if it only lasts during a few days. But if you’re very frequently exposed, over the course of years, they can cause premature death and other severe health problems. Only by taking a few precautions and heeding the warnings from WHO and the Environmental Protection Agency, you can prevent a hazy day from becoming a disaster.

Sources

https://www.epa.gov/pmcourse/what-particle-pollution

http://www.lung.org/our-initiatives/healthy-air/outdoor/air-pollution/particle-pollution.html"