Types Of Air Pollution And How They’re Generated

Air pollution is more than smog and dusty city centers. It can range from fire smoke to car exhaust to microscopic sulfuric droplets and much, much worse.

The Environmental Protection Agency (EPA) has a whole long list of all the bad stuff in the air and how it can damage not just our own bodies, but the environment at large, too. And sure, we’ve come a long way as a society since the days of billowing coal stacks in every city industrial park, but there’s still a lot of work to be done before we can eliminate all the harmful pollutants out there. 

Out of that long list of toxic substances, the EPA has identified six main air pollutants that they call “criteria pollutants” — these are the pollutants that the EPA regulates most strictly because they can cause great damage to people and to the environment. They’re also the ones you might hear about more often than others, but they’re certainly not the only ones out there. 

Here are those six criteria pollutants, what they’re made of and how they’re generated in the first place! 

The EPA’s 6 main air pollutants

Carbon monoxide

Carbon monoxide (CO) is a colorless, odorless gas and as such is difficult to detect. It’s also an incredibly poisonous gas which can cause a variety of health problems, though right now we’ll focus on how it impacts the environment. 

Carbon monoxide air pollution is generated when any fuel burns incompletely, such as car exhaust, cigarette smoke and the fumes from wood stoves, gas stoves and other appliances (just to name a few). Carbon monoxide can also be released from industrial processes such as smelting and oil refining.

Carbon monoxide air pollution can contribute to ground-level ozone formation, which is a major component of smog. Carbon monoxide can also react with other chemicals in the atmosphere to form particle pollution, which is a mixture of solid particles and liquid droplets that can irritate the lungs and worsen respiratory diseases like asthma. In addition, CO is a greenhouse gas, which means that it traps heat in the atmosphere which can contribute to climate change and global warming.

Lead 

Lead is found in small amounts in the earth's crust and it can be found in products all around us. Much of the lead that’s wandering loosely and freely in our environment comes from human activities, such as burning fossil fuels, mining, smelting and manufacturing.

Lead has many different uses, but some of them have been banned or restricted in recent years because of the health risks. For example, lead was formerly used in gasoline, paints, ceramic products, caulking and pipe solder. Now, lead is mainly used in batteries, ammunition, metal products and devices to shield X-rays. As these products break down, small particles can be carried in the air and can be inhaled or ingested. Exposure to lead can cause a variety of health problems, especially in children. Lead can damage the brain and nervous system, and it can cause learning disabilities, behavioral problems and hearing loss over time. 

Lead particles that make their way into water and soil can also affect reproduction levels in plants and animals, causing havoc in delicate ecosystems and poisoning entire swaths of land. 

Nitrogen oxides

Nitrogen oxides (NOx) are a group of gasses that are made up of nitrogen and oxygen and are released into the air from car exhaust, power plants, welding, explosive manufacturing, rocket fuel and other industrial processes. 

NOx can have a seriously negative impact on our health and the environment in long-lasting ways. NOx can aggravate respiratory issues in humans and animals and, if exposed to it long enough, can cause respiratory infections. Too much NOx in the atmosphere can cause acid rain to form, thick haze to settle over the ground and can create algae blooms and nutrient pollution in oceans, rivers and lakes. 

All in all, it’s bad stuff.

Ozone

Ozone occurs naturally in the atmosphere and is essential to keeping our planet warm enough to sustain life. Without it, we would burn to dust from the sun’s ultraviolet rays or freeze to death as soon as it gets dark. All it is is three oxygen atoms — and hey, all-natural means a-okay, right?

Well, it depends. Ozone at a high atmospheric level — stratospheric ozone — is the good stuff that keeps us alive and protected from the sun. That’s the ozone that people are talking about when you hear the hole in the ozone layer being discussed. 

Ozone at ground level is more problematic. It doesn’t occur naturally below stratospheric levels but is formed artificially when nitrogen oxides and volatile organic compounds (VOCs) interact with heat and sunlight. Like, in a big city with a bunch of manufacturing plants, and vehicular exhaust, for example. 

If we breathe this ground-level ozone in, it can damage our lungs and cause respiratory issues like asthma. It’s also incredibly harmful to the environment since it affects a plant’s ability to photosynthesize and opens it up to diseases of all kinds. Over long periods of time, this could affect entire ecosystems and completely change what kinds of plants and animals live in a given area.  

Particulate matter

Commonly referred-to as PM, particulate matter is the term used to describe the variety of solid and liquid particles floating around in the air. The particle sizes can range from large enough to see with the naked eye (such as dust, soot, pollen and the like) to particles 30 times smaller than the width of a human hair! 

Though particulate matter can come from a variety of sources — manufacturing plants, fuel consumption, fires, cleaning products, dirt roads and more — and all of them together pose great risk to our health. If inhaled, particulate matter can get into our lungs and bloodstream and can cause respiratory and septic issues! 

This is why having air filters in your car and home is so important, and why getting away from the city every now and then is a good idea. The bigger and busier a city is, the more likely it is that the level of particulate matter in the air is higher. 

Sulfur dioxide

Sulfur dioxide is caused by a few different artificial processes that burn fossil fuels, such as power plants, industrial facilities, locomotive and shipping processes, heavy equipment usage and ore extraction in mining. It’s also a byproduct of volcanic eruptions, but there’s not much we can do about that one. 

Like most other air pollutants on this list, sulfur dioxide is harmful to our lungs and can cause a host of respiratory issues. It also contributes to smog, can cling to particulate matter and cause acid rain if concentrated in large enough amounts. 

Acid rain

Acid rain isn’t on the EPA’s list of criteria air pollutants, but it’s worth touching on since it’s caused by many of the pollutants on this list. 

At its simplest, acid rain is rain or any other form of precipitation that is unusually acidic (as in, it has more hydrogen ions than most types of water). Nearly all the fresh water on the planet has a neutral pH between 6.5 and 8.5; acid rain has a pH level dangerously lower than this that can exist anywhere from 4 to 5. 

Acid rain is caused by the release of sulfur dioxide (SO2) and nitrogen oxides (NOx) into the atmosphere: these pollutants react with water, oxygen and other chemicals to form sulfuric and nitric acids that can then fall to the ground in the form of rain, snow, fog or hail.

Acid rain can have a number of negative effects on human health and the environment: it can make lakes and rivers more acidic, which can kill fish and other aquatic life; it can also leach toxic metals from the soil into the water which can further harm aquatic life and make the water unsafe to drink.  Acid rain is also strong enough to corrode buildings and other structures made of limestone, marble, and other soft materials, damaging historical sites and important buildings and increasing the cost of maintenance and repair.

Acid rain is also what causes ocean acidification. A higher pH in the ocean means that small creatures can’t build exoskeletons and excrete calcium carbonate, both of which are vital processes that need to happen for healthy coral reefs and coastal estuaries to thrive.

This all seems bleak, yes, but there is a little bit of good that comes out of knowing about all of this.

For one, these 6 air pollutants are constantly monitored by the EPA and strict rules and regulations have been set in place to enforce their standards. There’s still a lot of this gunk in the air today — and there likely will be for some time — but the fact that we know about it today and are actively taking steps to live sustainably and cleanly makes the outlook a whole lot better than it was a few decades ago.

We can all do our part in keeping our air clean for us, our bodies, our environment and our planet as a whole. After all, if our air isn’t clean, there’s nowhere else for us to go — that in itself is a pretty good reason to fight for clean air!

Good luck!

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Featured photo courtesy Pixabay/Pixource