The 13 Most Devastating Air Pollutants' Health Effects: An Ultimate Guide

Hi again! You're currently reading the first part of my 3-installment series on air pollution and health.

In the first installment of this series, I talked about why air pollution is such a big problem. My main argument - backed with a ton of scientific data - is that millions of people die each year due to breathing polluted air and the health of billions is negatively affected.

This second blog post dives deep into the effects of different air pollutant health effects. Such air pollutants include toxic mold, particulate matter, sulfur dioxide, and many more.

The next blog post in this series will give you actual solutions. So stay tuned, one more blog post filled with gloom and doom and then everything becomes better!

Also, this is an epic 10,000-word long blog post that tries to be reasonably exhaustive on the basics of this topic. Nevertheless, I've made the topic as readable as possible:



The Science Of Thirteen Air Pollutant's Health Effects

Before diving deep into the effects of these many air pollutants, let's grasp two basic air pollution principles first.

The first principle is that while I've divided air pollutants into 13 categories below, in reality, some types overlap. 



Particulate matter, which are tiny particles emitted by cars and industry, can be created in the atmosphere by reactions of other types of air pollution that ended up there.

An air pollutant called "ozone", can be created when car exhausts react with sunlight. Air pollution can thus exist of chemicals that react within a given environment and create new types of air pollution.

Then there's another important basic principle:

The second principle is that air pollution does (generally) not just remain in the location it's emitted. Examples:

  • I'm living in a relatively clean environment in the Eastern part of the Netherlands. 

    A large industrial area can be found in neighboring western part of Germany. When the wind is going in the wrong direction (or the right direction for the inhabitants of that industrial area), some of that air pollution from Germany can arrive at my doorstep.

  • Very tiny particles, called "particulate matter", especially the really small variations, can travel for hundreds and even thousands of miles. Industry, energy creation, and industry are major sources of particulate matter. 

    When emitted in China, some particulate matter can literally end up in the west coast of the US. 

    Yes, really...

  • You can have bad luck if there's almost no wind, as an area that emits lots of air pollution can have its pollutants trapped at the location they were originally emitted.

  • Colder temperatures can prevent (some) air pollutants from being released into the atmosphere, which also negatively affects people living in areas that are net-contributors to air pollution.


The weather can thus determine how much air pollution ends up at your doorstep, not only by creating new types of air pollution but also by steering their trajectory so that they end up in one place rather than another.

One remark: don't be overwhelmed by the enormous list of pollutants that I've listed below. 

Instead, just get a general impression of these air pollutants - you don't have to understand their ins and outs completely to adequately deal with them. 

Of course, if you're interested then read the full sections. To be honest, the solutions given later are more important:

In section five I'm going to break down the solution to lowering your exposure to these toxins in very simple to follow steps. These steps to reduce air pollution levels will work regardless of whether you understand the intricate details of all air pollutants in this section.

Another remark before I'll take you through the list of pollutants: all the information supplied below, while seemingly complex, is still oversimplified

As of this moment, this guide is already over 15,000+ words long. If I had included all important air pollutants and described their full effects, not even 2,500,000 words would not have been sufficient.

Let's now take a deep dive into thirteen different air pollutants. I'll start with an air pollutant you're may be acquainted with: 




1. Carbon Monoxide (CO).

Carbon monoxide (CO) is a gas. CO is deceptively dangerous because it cannot smelled or seen.[23, 24; 27; 29; 58; 59]

Carbon monoxide is created when carbon-containing compounds (such as gasoline or coal) are incompletely burned, due to insufficient available oxygen being present. You probably know that "carbon dioxide" is normally created, instead of "carbon monoxide".

Let me explain:

Just imagine burning wood at a fireplace that does not have enough access to fresh air. Over time, oxygen levels around the fireplace will go down. The burning of wood that ordinarily results in "carbon dioxide" will then off-gas "carbon monoxide".

carbon monoxide breathing through firewoodCozy fireplaces: deceptively dangerous...


Most carbon monoxide (CO) is created by human action.


If you drive a car or truck or work in an industry where fossil fuels are used, small amounts of carbon monoxide can be emitted continually into the air.

Indoor sources of carbon monoxide exist as well.

Smoking is a common reason for inhaling carbon monoxide -  from both cigarettes or water pipes. Second-hand smoke is another reason you're being exposed to CO.


After breathing carbon monoxide it's absorbed by a compound called "hemoglobin" in your blood, which is extremely dangerous.

You see, the role of hemoglobin is to transfer oxygen in your blood.

Under the influence of carbon monoxide, that hemoglobin is transformed into something called "carboxyhemoglobin", making the hemoglobin compound impotent. As a result, your blood can no longer properly carry oxygen (and carbon dioxide).

The consequence is that the oxygen that you breathe through your lungs--that is normally diffused into the bloodstream--can no longer be used. Your body's cells end up no longer functioning adequately.

In worst case scenarios you can even die of the consequences of CO poisoning.

Remember that air pollution was called a "silent killer"? That statement is especially true for carbon monoxide. 


You don't initially notice that you're breathing this compound, and may fall asleep (and die because of the body's inability to regulate itself in sleep). 

Over time, you may notice symptoms of CO poisoning. 

These symptoms can include headaches, mental problems (confusion or poor memory), nausea, dizziness, and overall bodily weakness. You may also have a low heart rate or low blood pressure, poor coordination and less of an ability to speak clearly.

Shocking fact?

CO Is currently responsible for 50% of fatal poisonings in the world.

Carbon monoxide also influence how well your mitochondria function.

Mitochondria are the energy-producing factories in your cells. While I'm oversimplifying, oxygen and food are transformed into water and carbon dioxide in the mitochondria. In essence, the process that's present in plants by which plants create oxygen from carbon dioxide and water is reversed in your mitochondria. 

Carbon monoxide thus short-circuits that process in your cells as well so that they can no longer function adequately.

And there's more bad news:

If you're severely poisoned by carbon monoxide, a full recovery can take months.[30; 31]

And it's not just the severe cases of carbon monoxide poisoning that you should worry about.

Smaller exposures matter...

Remember that the exhausts of cars and trucks produce carbon monoxide.[65] Many people are exposed to that pollution without ever nearing the threshold of full-fledged carbon monoxide poisoning. 

In other words, if you're being exposed to small amounts of carbon monoxide every day you probably won't notice any symptoms, but your blood will still carry less oxygen and the energy creation process in your cells will be sub-par.

The more carbon monoxide entering your body, the worse your overall health becomes.

If you're spending lots of time inside vehicles, you're going to be exposed to more carbon monoxide.[32; 33; 34; 35] That car exhaust can significantly lower your blood pressure, for example.

Just spending time outside in bigger cities with lots of cars increases your carbon monoxide exposure as well. 

Lots of appliances likewise emit small amounts of carbon monoxide.[36; 45]


Lawn mowers, leaf blowers, electricity generators that work on fossil fuels, etcetera. Indoor carbon monoxide sources are air conditioning systems, (central) heating, and generators.

Indoor cooking in developing countries also produces carbon monoxide, which may increase blood pressure.[64The reason for that carbon monoxide creation is that indoor levels of oxygen tend to go down if you cook indoors. 

But let's explore CO's health effects in more detail...

Carbon monoxide exposure is related to many negative health effects, such as:[37; 44; 48; 51; 55; 57; 60; 66; 69]

  • plaque buildup in your blood vessels, heart problems, a greater frequency of brain infractions (dying brain tissues due to a low oxygen supply), and lower overall brain volumes.
  • being more susceptible to heart problems or dementia, years down the road (if you've been poisoned by carbon monoxide).
  • poorer development of the nervous system and brain, especially among children. When pregnant (prospective) mothers are exposed to carbon monoxide, fetuses can be damaged. Children are also more prone to be born prematurely with increased carbon monoxide exposure levels.
  • greater risk of getting diabetes. In diabetes, the body no longer produces the "insulin" hormone or does not correctly use sugars inside cells. Both a decrease in insulin production and sugar usage have detrimental effects on how well your cells are able to produce energy - and your ability to function in life.
  • more allergies, resulting in nasal irritation - especially in children. Lung problems such as asthma also increase with greater carbon monoxide exposure.

Yes, overall that's very bad news. Carbon monoxide is thus not "innocent"...

Health problems due to higher carbon monoxide levels are quick to show up:

If levels increase by 1mg per m3 then a city about 1% more people will die of heart disease and strokes over time - other studies show an even bigger effect.

If you've already got heart disease, lung problems, anemia (low iron in your blood, which already gives you an inability to transfer oxygen well), have multiple diseases, or if you're of young or older age, then carbon monoxide will affect your health even more than normal.

Short-term exposures of carbon monoxide can thus put you "over the top" if you're already sick.

Delicious sight--but not enough oxygen present
to prevent carbon monoxide buildup?

The bright side about carbon monoxide is this: even if you're poisoned, you may recover eventually.[46; 50]

Brain recovery and increased diabetes risk, while sometimes taking years of time, are possible. Unfortunately, stroke risk and heart disease risk do appear to remain higher over time.[51; 54; 55]

Fascinating fact:

Really low levels of carbon monoxide exposure might be beneficial to your health, as there's an adaptive response to exposure.[63]

Don't stress out too much about carbon monoxide right now. Remember: in a later section I'll teach you how to avoid the worst pollutant levels...

Let's move on:

You'll now learn about an air pollutant that most people don't know about, nitrogen dioxide:



2. Nitrogen Dioxide (NO2)

Just as with carbon monoxide, fossil fuel usage is one of the main reasons nitrogen dioxide emissions exist in the first place. Most nitrogen dioxide either originates from traffic emission or power generation (and use).

Industry or agriculture does not emit large quantities of nitrogen dioxide (although they do emit other nitrogen substances).

Nitrogen dioxide is a gas. Inhaling that gas mainly has consequences for your airways and lung health.

Nitrogen dioxide is part of a group of substances called "nitrogen oxides" (NOx). Nitrogen dioxide is the most important type of NOx, and to keep the message relatively simple  I'll, therefore, focus on nitrogen dioxide in this blog post.

At higher concentrations (for nerds: 200 micrograms per cubic meter (m3)), nitrogen dioxide is directly toxic. 

Let's consider the following NO2 health consequences. Over time, NO2 exposure:[92; 106; 117; 352; 353; 358]

  • increases your all-cause mortality risk. 

    All-cause mortality is your general risk of dying, whether that's of lung disease, a car accident, or old age. In fact, with every 10 micrograms per m3 increase in NO2 levels that you breathe, your overall mortality risk goes up.

  • creates lung problems such as asthma (a lung inflammation disease), and COPD (reduced airflow and lung capacity).

    With greater exposure levels nitrogen dioxide also makes you more likely to be taken up in a hospital for lung or heart problems (which is somewhat self-evident). Existing lung conditions such as asthma also become more severe with greater NO2 exposure. 

    Fetuses who are exposed to NO2 during pregnancy they also have more respiratory problems later in life.

  • raises your risk for heart and blood vessel diseases, and lead to higher blood pressure, especially with long-term exposure. Heart attacks, heart failure, and brain infarctions also increase with greater exposure levels. 

    (With a brain infarction, part of your brain tissue dies due to low oxygen levels. Bleeding can be a cause of such infarctions.)

  • may even slightly increases women's risk for breast cancer, as well as overall cancer risk.

Not fun, that list...

You may be thinking: "No problem. Not that many people get hurt by nitrogen dioxide..."


Let me  give you a perspective of how damaging NO2 is:

In Germany, it's estimated that up to 8% of all diabetes cases are directly caused by nitrogen dioxide - equaling nearly half a million people. 

That figure alone also tells you why air pollution is not a problem you can choose to ignore if you care about your health.

Another example: over 20,000 people die in the United Kingdom because of this air pollutant on a yearly basis.[107]

Why are the effects of nitrogen dioxide not widely known?

Well, for a long time it was hard to distinguish between the effects of nitrogen dioxide and particulate matter - both air pollutants are co-created in large quantities in modern society. And now the extensive effects of this pollutant are correctly understood, it's time to get more worried...

And there's more bad news:

Children, elderly people, and people with pre-existing lung or heart problems are hit hardest by exposure to this air pollutant (again).

If you've got lung, airway, or breathing problems, inhaling nitrogen dioxide can exacerbate your symptoms, such as causing an increase in coughing, wheezing, an increase in mucus production, or breathing problems.

And unlike air pollutants that I'll consider later on in this blog post, such as pet dander, the evidence for the negative health effects of NO2 is solid.

Really solid...

When emitted into the air and reaching the atmosphere, NO2 can also react with other chemicals which leads to the production of new air pollutants.

In fact, two air pollutants that can be created through reactions with NO2 are next on the list: ozone (O3) and particulate matter.

The next air pollutant should create an even bigger incentive you to take air pollution seriously:



3. Particulate Matter

So let's consider particulate matter: the "king of air pollutants"--or maybe "most tragic air pollutant" is a better name...

Particulate matter are tiny particles subsumed in the air that are created as a byproduct of traffic, energy production, cooking, and industry.

800,000 people die every year due to particulate matter exposure. Billions of individuals' health is negatively affected due to the same substance.[181; 182]

Due to particulate matter's heavy impact on human health, I've written an extensive blog post (or guide) on the topic before. That guide teaches you how to reduce your particulate matter exposure by 50-90% - even while living in the city.

But let's talk about that stuff quickly:

Particulate matter is commonly measured by size - specifically the "micrometer" metric. One micrometer is a thousand times as small as a millimeter - yes, that's really small.

The problem is that these tiny particles end up in your lungs, your bloodstream, brain, and organs. Once particulate matter enters your body, the damage begins.[183; 190

Different types of particulate matter exist.

Common measurement categories for particulate matter are:

  • those with diameters smaller than 10 micrometers, called "PM10";
  • smaller than 2.5 micrometers which are named "PM2.5";
  • and smaller than a tenth of a micrometer, "PM0.1"

To put these numbers in perspective: the average human hair has a diameter of 70 micrometers...

2.5 micrometers or 0.1 is thus extremely small and invisible to the human eye.

Particulate matter exposure has many negative health effects--smaller types of particulate matter such as PM0.1 and PM2.5 have stronger negative consequences because they more easily transfer to the blood from the lungs.

The smallest type, PM0.1, may even be able to travel directly from your nose to the brain.

It's often hard to imagine that particulate matter has negative health effects, so let's consider the following analogy:

Most people can imagine that if billions of harmful bacteria are breathed in, that they can be harmful to your overall health. In the case of particulate matter, you can simply imagine that tiny dust particles end up everywhere in your bloodstream, brain, and other organs.

In fact, dust often consists of particulate matter so you don't need to think very far outside the box to understand the effects particulate matter has on your health.

Health effects?


There are many...

But let's consider a shortlist with the most important health effects of breathing in particulate matter. Particulate matter causes:

  • an increase in all-cause mortality, which is your most general risk of death no matter what the origin.[191; 196]
  • more lung, heart, and blood vessel diseases, and lung cancer.[197; 209; 352; 353] Overall lung function development in children, as well as lung function in healthy people also decrease.
  • surges in stress hormone levels such as cortisol and adrenaline. Yes, you'll immediately become more stressed and even have higher blood pressure levels with particulate matter exposure.[211; 212]

(Many more effects are laid out in my extensive guide on particulate matter.)

Children, elderly, and people with pre-existing lung or heart conditions are hit the hardest by particulate matter (yet again).

While short-term exposures to particulate matter already cause adverse health effects, such as an increase of stress hormones and blood pressure, the negative health effects of particulate matter accumulate the longer you're exposed.

The last two air pollutants I've discussed (particulate matter and NO2) are mainly found outdoors. The next one is found is found everywhere:



4.  Volatile Organic Compounds (VOCs).

Volatile Organic Compounds or "VOCs": that sounds like a complicated word. 

No worries though...

VOCs are a gas and are made of molecules that have a low boiling point. VOCs are created by "off gassing" from solid compounds.

Simply put, VOCs evaporate into the air...

VOCs can be created from several sources, such as a byproduct of the burning of fossil fuels or as an off-gassing of chemicals such as solvents.

Sources of VOCs are oil and gasoline that are burned by cars and airplanes, as well as fossil fuels used in energy generation (e.g. power plants).

But VOCs are often found indoors as well.


Coatings, varnish, glue, adhesives, and paint are common VOC sources. Plywood, vinyl flooring, and particleboard are also problematic off-gassing causes. Additional sources are cosmetics, aerosol sprays, air refreshers, cleaning products, and disinfectants.

VOCs are literally everywhere. Examples:

Plastic materials in kids playing toys? Toxic VOCs.[156

Getting your hair colored in a salon?[167] More VOC exposure...

That new car smell? That's VOCs being emitted from the interior.

Incense burning or indoor smoking? VOCs...

Buying a new dinner table, sofa, carpet, or cabinet? That furniture is coated with VOCs to preserve the material and make it look shinier.[149; 151; 159; 160; 162; 165

A beautiful new painted or coated cabinet will release new gases into the air over the course of years.

How about outdoor VOCs?

Benzene exposure when refueling your car tank, or the exhaust you're smelling when using your lawn mower are common sources.

a picture of furniture, which can off gas VOCs
Counter intuitive VOC indoor air pollutants from chairs, 
cushions, and the couch...

Simply put, VOCs are gases that are emitted from many compounds humans have introduced to the environment.

Indoor VOC levels are generally two to five times higher as outdoors.[152; 154

Unfortunately, not all VOCs are easily measurable, so the scientific understanding is still incomplete.

The levels of one VOC called "formaldehyde" can be easily estimated, for example. The problem is that thousands of different types exist, which are sometimes hard to measure. New VOCs are also identified over time...

So what are VOCs health effects? Let's jump straight into another list of consequences you'd want to avoid. VOCs:

  • raise your risk of asthma and allergies. VOCs also increase inflammation in the lungs while decreasing your lung function.[148; 150; 154; 158; 170Mothers exposed to VOCs during pregnancy may also confer a higher asthma risk upon their (eventual) kids.
  • may increase heart disease risk while almost certainly giving you more lung disease.[166; 169170; 171cause organ damage, particularly to the liver and kidneys, as well as nervous system (neurological) problems.[172; 177]
  • probably increase cancer risk.[161; 166; 168
  • give you nasal, throat, and eye irritation.[163Higher VOC exposure levels can cause dizziness and headaches.[161; 164

And it's not just breathing that's problematic--VOCs also enter the body through skin exposure.[178; 180]

As often the case with air pollutants, currently recommended VOC exposure levels may currently not be stringent enough.[163]

It's safe to assume that less exposure is better.


Advanced explanation: It's not probable that short-term exposure to VOCs is very damaging. The problem starts with longer-term exposure.[154] Additionally, a problem with mapping the health consequences of VOCs, however, is that they are a very broad category that tells you almost nothing about the effects of individual toxins. Some VOCs have been proven to be highly damaging, such as formaldehyde, while many other VOCs have yet to be identified. Data on exposure patterns of different types of VOCs is also limited compared to previously treated pollutants. The topic of VOCs is extremely complex, as toxicology and exposure patterns of thousands of chemicals as well as their interactions would need to be mapped to attain a complete understanding.


An example of a VOC?

Let's consider one you probably know of: benzene.

Benzene is a natural part of crude oil. 

When you're filling up your gas tank at the gas station, you're being exposed to benzene if the wind is blowing in the wrong direction (at you). Forest fires, volcanoes, and cigarette smoke are other benzene sources.

As a VOC, benzene has many different health effects.

At low levels, benzene causes throat irritation, trouble breathing, skin rashes, eye irritation, increased blood pressure and confusion. [240; 243At higher levels, benzene increases the risk for leukemia (cancer of blood and bones), especially in children, but can also cause kidney and liver problems - and finally even death.[237; 239; 244; 247] 

And although my treatment of benzene is really superficial here, fully considering its effects of different all types of VOCs is impossible in one blog post. 

And remember: even though this list may seem overwhelming, I'll tell you all about simple solutions later on in this blog post.

Stay with me...

Next, I'll consider an air pollutant which many people living in the 70s and 80s are acquainted with:



5. Ozone (O3)

You probably know about the chemical structure of the oxygen you're breathing (O2), which contains two oxygen atoms.

(Both the atoms of the substance that you're breathing, as well as the compound gas itself, are thus problematically called "oxygen".)

A compound called "ozone" also exists, which contains three oxygen atoms (O3). 

When present at the earth's surface, that ozone is often considered a pollutant. Nevertheless, ozone is also essential for life to exist at this planet at all: in the atmosphere, ozone filters out excessive radiation from the sun.

That ozone in the atmosphere is called "stratospheric ozone". The emission of several air pollutants into the air can damage that protective "ozone layer", but fortunately, that layer is slowly recovering.

Ozone emissions have been going down the last few decades--this air pollutant is thus currently less damaging than it was 30 years ago. Bright spot: again, humanity can improve the environment.

picture of the sky, in which ozone was depleted up until 20 years ago
The protective ozone layer is found
20-30 kilometers up in the sky


On the earth's surface (where you're living unless you're an astronaut), ozone is mainly created through the reactions of other chemicals.

To be more precise:

Chemicals that were treated earlier, such as VOCs and nitrogen oxides, can react with sunlight to create ozone on the earth's surface.

Remember that VOCs and nitrogen oxides (NOx) can be created from many sources, such as exhausts of vehicles that burn fossil fuels, as a byproduct of energy creation, industry, and others.

Even though many previously treated pollutants are more problematic in colder environments because they are more prone to keep on "hanging" in the air, that's not true for ozone - sunlight is essential to ozone creation.

Not all ozone is created by humans though: a greenhouse gas called "methane" is a natural source for ozone when it reacts with sunlight. 

Small amounts of ozone are generally considered safe, but in larger amounts, negative health effects begin to appear. 

You might be thinking: "so what are the health effects of ozone?" 

Ozone exposure increases your:[110; 112; 143; 147]

  • risk of dying of heart or lung disease if you're exposed to higher concentrations. More ozone exposure also gives you a decline in lung function and increases hospitalizations if you've got existing lung problems. 
  • overall stress levels and inflammation. Inflammation underlies many modern diseases such as heart and brain diseases, and cancer. Of course, more stress is not beneficial for most people either...
  • your risk of having allergies.
  • causes a higher risk for "stillbirth", which is the death of the fetus during pregnancy, and an increase in heart defects of children after they're born.

Fortunately, the effects of ozone exposure have no (proven) effect on your mental health, such as autism, dementia, or decline in thinking ability (cognitive functions).[109]  Your overall risk of death, surprisingly, is not affected by both short-term and overall yearly ozone concentrations either--although there's some conflict of evidence regarding this point. 

And again:

Children, women, older or obese people are more strongly affected by ozone air pollution.[113; 114; 123; 125

If you have pre-existing lung or heart conditions ozone will also affect your health more negatively.[129]

Even if you're healthy, you should still be wary of ozone exposure because of its effects on the airways. Your propensity for shortness of breath, wheezing, coughing, and inflammation increases - of course, this process occurs more frequently if you've already got lung problems.

Although there's some contradictory evidence, some studies suggest that your lungs and heart simply have to work harder when you're exposed to ozone.[137; 141] Longer-term exposures at higher concentrations are most likely harmful.

Another problem:

Current safety threshold set by institutions such as the US Environmental Protection Agency may not be low enough to prevent harm to those who are more susceptible to ozone's damage.[142]

Fortunately, ozone pollution is not the worst air pollutant out there, but you should be wary of excessive exposure.

Previously treated air pollutants such as particulate matter and nitrogen dioxide are much more damaging than ozone.

To reduce exposure, be very wary of any indoor ozone-generating products. Some air purifiers, for example, sometimes generate ozone as a byproduct or even intentionally emit ozone into the air.

Ozone may be helpful in certain instances, such as reducing the toxins of household items that have collected mold on them--but it's recommended to be extremely cautious with exposing yourself to ozone if you don't know what you're doing. 


Advanced explanation: keep in mind I'm not in favor or against what is called "ozone therapy". Ozone therapy seems to elicit a hormetic reaction in the body, and may or may not have health benefits - I've not closely looked at the evidence yet, so I cannot judge.


Next, let's consider sulfur dioxide - the air pollutant that was primarily responsible for the great fog of London in the 1950s, which started a wave of air pollution control legislation:



6. Sulfur Dioxide (SO2)

Sulfur dioxide is actually one of the longest tracked air pollutants.

The reason for that relationship is that sulfur dioxide is a direct byproduct of energy production from coal.

a fire that emits sulfur dioxide
Coal: humanity's angel and devil at the same time.


As coal was used on a larger scale after the Industrial Revolution, nations began to track their coal production and consumption. From that data it has now become possible to reconstruct how much SO2 pas were put into the air over the last few centuries.[22]

The reason sulfur dioxide emissions were reduced in Europe and North America after the 1970s and 80s, is because SO2 lowering technologies were mandated for energy production industry such as coal plants.

Even in some Asian countries such as China, SO2 emissions are declining today. India, however, still increases its yearly emissions, which is why overall Asian SO2 emission increase.

Sulfur dioxide a few unwanted health consequences. Sulfur dioxide:

  • increases your risk for heart and lung problems.[351; 354; 357; 363; 364

    With short-term exposure, you'll (just) have an increased risk of shortness of breath or chest tightness, especially if you're breathing actively. Sulfur dioxide can also disrupt your heart rhythm. 

    Due to longer-term sulfur dioxide exposure your cardiac arrest frequency increases - in cardiac arrest your heart stops pumping.

    In fact, every 10 micrograms per cubic meter of sulfur dioxide exposure - a frequently used measurement method for air pollutants levels - linearly increases your chances of dying of a heart or lung disease. The same linear relationship is likely applicable to children's risks of getting asthma (if they're exposed to sulfur dioxide).

  • raises risks for birth defects and pre-term births.[357; 358; 359; 363]

    Stillbirth risk and lower birth weight risk also surge with more SO2 exposure. Sulfur dioxide exposure during pregnancy also increases asthma and wheezing in children after they're born.

    Notice a pattern here? 

    Many air pollutants are damaging during pregnancy...

  • may lower reproductive fitness.[361; 365; 366; 367 ]

    Unfortunately (or perhaps fortunately), these reproduction-lowering effects have only been established in rat studies.


That's it...

When sulfur dioxide is emitted into the atmosphere, chemical reactions can also help it turn into particulate matter. Acid rain can additionally be created through sulfur dioxide exposure, so the pollutant has a negative effect on the environment. 

Your neighbor is thus not always your best friend when sulfur dioxide emissions are in play...

Next to sulfur dioxide, other sulfur gases such as SO3 are also harmful. I won't cover these other sulfur compounds in order to not complicate this blog too much...

Having said that, I'll now move to the next category of pollutants: air pollutants with indoor origins (most of the time): 


7. Biological Pollutants

Let's start with a definition: biology is the study of living organisms. All air pollutants included in this subsection are thus (derived from) living beings. 

I'll consider several biological air pollutants, such as allergens including pollen, animal dander, and dust mites.

How you respond to these biological pollutants really depends on you individually. You may be really susceptible to pollen, for example, or not susceptible at all.

If you're having an adverse reaction to biological pollutants, many of the symptoms overlap with what you'd get from exposure to air pollutants such as sulfur dioxide or particulate matter:

  • coughing
  • eye irritation
  • a running nose
  • throat problems
  • sneezing
  • breathing problems

Stronger reactions entail having headaches, becoming ill, dizzy, or depressed. 

Of course, exposure to germs can have more far-reaching consequences.

Biological air pollutants are somewhat different than other pollutants in that your immune system is more prone to consider them invaders.


Some people's immune system responds very heavily towards certain substances entering their bodies. If your immune system reacts very heavily over and over again, you'll feel the consequences - resulting in the symptom list I described above.

Let's consider these biological pollutants in more detail. Examples of allergens are:

  • Pollen, which causes hay fever in some people

    You may know someone with allergies: they'll get sick if they eat peanuts or drink milk. You also know some people who are completely unharmed when consuming milk or peanuts - signifying an absence of allergies

    So what's up with allergies, and the substances causing these allergies called "allergens"? 


    Pollen should not be considered an "invader" to your body but can be treated as such if you're allergic. Pollen are emitted into the air by plants and act as a fertilizer for plants of the same species. These pollen can travel hundreds of miles...

    When pollen are reintroduced into the air in the spring at many locations, for example, asthma attack numbers increase, .[320

    Different people are allergic to different types of pollen. You may be intolerant to the pollen of certain grasses, or to pollen of beech trees while having no problem with grasses at all.

    (Keep in mind that in this blog post I'll only consider substances emitted through the air, and not food allergies.)

    The result for (some) poor humans?

    If you're breathing these substances while allergic, signaling substances such as "histamine" are created as a response to the allergen exposure, and bodily inflammation is increased.

    A surprise about allergies?

    Contrary to 50 years ago, allergies are really widespread today: up to one in four persons has hay fever in developed countries.[33140 to 50 million people have one allergy or another in the US alone, 

    And you know what?

    Allergy risk increases by exposure to lots of (smaller) particulate matter and dust mites (a topic I'll treat in a second).[314; 315Particulate matter exposure also worsens existing allergies.[317; 318; 319

    In fact, indoor pollutants pose the biggest risk factor for developing allergies.[316]  Suddenly those omnipresent VOCs no longer sound so smart. Many "regular"air pollutants thus contribute to your risk of getting allergies to biological substances. 

    But let's move to the next biological air pollutant:

  • Animal dander

    Animal dander are tiny skin particles emitted by furry or feathery animals. Most pets either have fur or feathers.

    Fun fact?


    You can get reptiles pets that do not emit any dander, but their foods such as grasshoppers can be problematic for some allergic people...[321]

    So there's no easy solution for pets...

    You're probably aware that your beautiful cat or dog can get you in trouble, and that they don't just do so by breaking things. 


    Roughly the same immune reaction occurs when an allergic person is exposed to animal dander as happens in someone who's hypersensitive to pollen.[322; 323; 324It's not just dander that sensitizes some people towards these pets, but also microbes associated with these animals.[320; 329]

    It's very sad if family members have allergic reactions to pets, as pets are often considered part of the family. It's tragic to find out that you're allergic to the dog you love so much...

    Let's talk about prevention though:

    Exposure to pets or farm animals when you're young is generally as protective against developing pet allergies.[326; 327; 328Having other bacteria exposures, such as from drinking raw milk or a vaginal birth (as opposed to a C-section) may be protective as well...

    In general, owning cats is also more protective against allergies than owning a dog.[330

    (I'm waiting for dog-persons' hate e-mails to arrive)...

    Unfortunately, most of us no longer grow up around farm animals when we're young, no longer drink raw milk, and C-section births have also been increasing in the last few decades.

    Again: tragic...

    Pet allergies, however, are far from completely understood. The coming decades will probably yield lots of exciting new research...

  • Dust mites

    You may know about dust mites: tiny organisms living on furniture and in dust.[332] 

    Mattresses, pillows, and carpets are other preferred dust mite places.[334; 335; 336; 342] Couches and cushioned chairs are also breeding grounds. 

    All buildings contain dust mites but different buildings contain different numbers of them.[331Dust mites thrive in warmer and more humid environments.[338] If you're living in a drier climate, you're lucky: dust mites have a harder time growing there.

    (I'll get back to the topic of sterile environments later--developed countries may have a problem with too much hygiene in some regards).

    But let's get back to dust mites:

    If you're living in developed countries with good hygienic circumstances, you're more prone to be allergic to dust mites than when you're living in a rain forest or a primitive hut in the desert.[333]

    Dust mite allergies usually develop during your childhood or teenage years and are currently non-curable. If you're more intolerant towards dust mites, you'll also have higher risks of having other allergies as well.[339; 340; 341]

    But let's move on...

    Just when you thought the topic couldn't get any more disgusting:

  • Cockroaches

    Yes, cockroaches are a bit gross but I'll have to consider them anyway...


    Having cockroaches in your home, for example, increases your risks for asthma.[343; 345The reason for the allergenic nature of cockroaches is because they emit tiny particles which you may not tolerate.

    If you're sensitive to cockroaches you're also more prone to be sensitive to dust mites, and vice versa.[347Again, observe that many allergies are interrelated...

    Different types of cockroaches exist in varying climates.[348] Cockroaches found in colder climates are not the same as those thriving in hot and humid conditions.

    Pest control is recommended if you've got a cockroach problem. I'm not an expert on cockroaches (fortunately), but generally, if you've got an insect problem in your home then it's wise to get help.

    Living in the city--yet again--is associated with cockroach allergies increases.[346; 349; 350

    Farmboys like me fortunately do very well in the allergy department (you didn't think I was a farmboy right?)

A sad development, all these allergens--as if human-made air pollution weren't menacing enough...

And you know what? 

Allergies are very "weird" from an evolutionary perspective.

Many traditional societies don't have a conception of allergies at all. 

Hay fever was extremely rare in the late 19th century. Specific diseases that are highly interrelated with allergies such as asthma only became more prevalent after the 1960s.[325] 

"Coincidentally" (or not so coincidentally), the number of allergic people has massively increased since humans adopted an indoor lifestyle. 

Spending lots of time indoors thus has its expected downsides...

By the way:

I've decided not to treat germs such as bacteria and viruses in this section. 

Let me explain why:

On the one hand, germs have made human lives miserable and short for thousands of years - they're thus really important. 

Tuberculosis incidences, for example, which are caused by bacteria, are dramatically influenced by air quality. Influenza is another example that's widely known as a pathogen that's carried through the air.

On the other hand: humans have always been exposed to germs. Germs are thus very different than many types of modern air pollution, in that continuous air pollution is novel from an evolutionary perspective.

Even biological types of air pollution such as the dust mites and cockroaches stand in a totally different relationship to you today than 200,000 years ago when your ancestors evolved in Africa.

That's why I excluded germs here...

Next, another indoor air pollutant: 



8. Radon (Rn)

Back to the topic of gases: radon (Rn) this time. 

Remember that I've considered other gases before, such as carbon monoxide (CO).

And just as is the case with carbon monoxide, it's impossible for you to smell radon. And likewise to carbon monoxide, the only way to know you're exposed to radon is to measure

How does that happen?

Well. radon is created when uranium decays.[72

Radon naturally occurs in the earth's surface and is emitted from there. The more uranium within the soil, the higher your radon exposure generally will be. 

Radon can be found in homes, offices workplaces, and public buildings, but is not found outside homes in any large concentrations. 


Radon quickly dilutes in outdoor air. 

Radon is thus only damaging when it emerges from the soil into buildings such as houses or offices - being trapped there for a while.

Cracks in the floor, spaces around pipes that have not been sealed, and holes in walls are mechanisms by which radon "sips" into buildings. Good isolation of ground floors of buildings ensures that less radon is passed from the basement or crawl space into the actual building.

Basements generally get high radon exposure. Other underground locations such as caves and mines are especially dangerous for radon levels - unless they're properly ventilated.


Poor ventilation "entraps" some of the radon in buildings, resulting in negative health effects. 

Radon has only become problematic is (again) because humans have moved indoors while insulating their buildings so that little air can enter from the outside.

If you're thinking: "am I at risk", then here's the answer:

You can guesstimate your exposure levels with the following maps:

USEU, or Australian map, for example, gives you a general impression of how likely radon levels are high at your location. 

Don't use that map to speculate about your specific living locations' radon levels though, as two houses located 100 yards apart can have hugely different exposure levels.

On another note...

Want to know a shocking radon fact?

Here it is:

Next to smoking, radon is actually the second most common cause of lung cancer.[70; 71; 75; 77; 82; 84; 87]

The risks of these two dangers stack: if you're already smoking then radon exposure will further increase your cancer risks.

Up to 10 times as many smokers die of radon exposure compared to non-smokers. Smokers also have up to 25-times higher risks of dying of radon-induced lung cancer than non-smokers.

That's devastating...

There's no radon exposure "safe zone" regarding lung cancer risk--less exposure is always better, even if you don't smoke.

While the link to lung cancer is strongest, radon exposure is also associated with other diseases:[76; 78; 79; 81; 83; 89; 90]

  • Lung diseases, such as "COPD" - COPD gives you breathing and lung problems.
  • Several nervous system diseases.
  • Skin cancer and cancer in bones and blood cells (leukemia), but not lymph system or nervous system cancer.

Unfortunately, the research in these non-lung-cancer health domains is not crystal clear yet. It's thus essential to wait for more high-quality research to be released on those topics.

The relationship between radon and disease is fascinating to me because it's reasonable to assume that radon exposure does cause additional health problems next to 20,000 yearly lung cancer deaths (in the US alone).

In the case of particulate matter, many health effects were also discovered in time. I expect radon to follow the same pattern (to a lesser extent) as well...

Furthermore, radon can also end up in your drinking water.[73; 74] It's uncertain whether radon in drinking water has health effects though, as exposure has negative associations with stomach cancer, for example.[81]

Realize that the 20,000 US radon-induced lung cancer deaths figure is immense.

Putting that number into perspective: drunk driving kills 17,400 people each year, drownings 3,900, and home fires "only" 2,800.[90]

Radon air pollution is not part of the common awareness (yet again), the problem is therefore not actively tackled actively.

But enough about radon...

The next air pollutant is carbon dioxide. You probably know that compound from biology class:



9. Carbon Dioxide (CO2)

Carbon dioxide is often considered an environmental pollutants--but its true status is more complex - even in your body.

I nevertheless subsume carbon dioxide under air pollutants because high indoor CO2 levels are often a culprit why people function poorly. Let's start with a comparison to understand high CO2 levels in indoor environments.

If you're spending time in the forest or on the beach, the air contains about 400 parts per million carbon dioxide.

(Outdoor CO2 levels have been creeping up due to climate change. CO2 levels used to fall below 300 parts per million in the 19th century.)


That's where you get into trouble.

well-ventilated indoor environment contains up to 1,000 parts per million CO2. But: that 1,000 parts per million almost triples "nature's normal levels" alrady.

And the story gets worse.

Much worse...

Indoor environments such as offices and classrooms can contain levels up to a whopping 5,000 parts per million of CO2.

In the wintertime, classrooms in temperate climates generally have CO2 levels between ~600 and 4,000 parts per million. During the summertime that levels decreases to ~500 to 2,000 parts per million.[299]


Less ventilated a building build up more carbon dioxide.[296] Let's now first consider the problem with too much carbon dioxide.

Here are some carbon dioxide health facts:

  •  With every 100 parts per million CO2 increase in classrooms, attendance dropped 0.2%.[298Children thus called in sick sometimes due to higher CO2 concentrations.[305] 

    Fortunately, kids' test performance was not negatively affected by that indoor air quality. Kids thus still do reasonably well with poor air quality.

    But older people like you and me?

    Different story...

    Teachers are less well off: headaches, fatigue, and an inability to focus all increase with high CO2 levels.[300]

  • If CO2 levels exceed 800 parts per million in offices eye irritation and breathing problems are more likely to occur - although these symptoms may also be explainable by indoor pollutants co-present with carbon dioxide.[301]

    Higher CO2 concentrations also promotes tiredness and dizziness.[302An increase from 600 to 1,000, (or worse: 2,500 parts per million) even impairs your decision-making ability.[304]

    Reducing both VOCs and CO2 levels, instead improves cognitive performance.[306; 307]


In general, your health immediately declines slightly once your spending time in a room where CO2 levels approximate 1,000 parts per million. 

Getting a good ventilation system in place is one method to keep CO2 levels low.[303In fact, optimizing CO2 levels is highly underrated for improving indoor air quality (and well-being).

That's it for CO2.

Now I'll tell you about one of the most toxic indoor pollutants - in many instances this one should make you run, not walk: 



10. Toxic Mold

Mold spores are fungi. Fungi are neither plants nor animals but are a separate kingdom in biological classifications.


Look at the wall below:

a picture of toxic mold on a wall

That's toxic mold.

Toxic mold exposure can be devastating to your health. To be clear: not all mold is toxic, but the mold displayed above is. That mold type is known as "black mold", and frequently found in the developed world.

Mold primarily originates from water damage - whether that's from a flood, humid air, or leakages. In humid or wet materials, mold has the ultimate means to multiply and spread.

What materials precisely?

Well, wood products, carpets, cardboard, drywall, insulation, paint, ceilings, wallpaper, and even dust are favorite mold growing places. 

Mold is problematic as an indoor pollutant because up to 10 - 50% of residences and offices in the developed world are contaminated.[218]

No, that 10-50% is not a joke--it's a tragedy.

And that 50% estimation may even be low as people with mold intolerance are affected by an even greater percentage of buildings.

So how can mold hurt you?


If mold builds up in a humid medium such as a damp wall, it can continually emit toxins.

Of course, mold can also build up in your food, but you'll generally throw away moldy food once it's spoiled. A moldy wall can stay in place for decades while emitting toxins that entire time.

And while these toxins are not living organisms in themselves they can be damaging to you.

So what are mold exposure health consequences?

Let me tell you:

In the "best case scenario", mold exposure makes you breathe more poorly, irritated, and give you a headache. Simply put, you'll have a small allergic reaction but are fine afterward.

During the worst case scenario your entire immune system shuts down (or goes nuclear), with a disability, being bedridden, seizures, and finally death as possible consequences.[213Yes, mold really kills people over time - its health consequences are wildly underestimated.

Of course, there's a large continuum of intermediaries between these two extreme responses to mold.

I've lived in moldy buildings before, and I presume I'm one of the "lucky" people who is not immediately affected by mold (to any great extent at least). Working inside a moldy home and sleeping outside during the summer ensured that I could still perform reasonably well.

Not many people are that lucky...

If you're sensitive to mold, just entering a building can trigger your immune system for the rest of the day.

Keep in mind that there's no scientific consensus on toxic mold - some scientists assume that mold poisoning is a pseudo-scientific concept.[212I'm very skeptical of that claim.


Consider these mold facts:

  • Mold toxins, also called "mycotoxins", can be detected in urine after exposure. One likely mechanism has also been established: you simply breathe them in through your nose.[215
  • Hundreds of studies have established the negative effects of mycotoxins.[216]
  • Upon contact with mold, hypersensitive patients get an inflammatory and immune response.[217; 223In rat studies, mold can cause extreme inflammation levels.[225] 
  • That inflammatory response has even been demonstrated to exist on the surface of your eye when that eye is affected by mycotoxins - illustrating how far-reaching the effects of mold can be.[222]
  • In lab tests, molds can change DNA and damages nervous system cells.[219; 220; 221]
  • Mold can create extreme symptoms in humans, ranging from nasal irritation to (symptoms of) nervous system and autoimmune disease.[226] (In autoimmune disease the immune system turns itself against your own body).


Even established institutions such as the World Health Organization and US Food and Drug Administration consider mycotoxins significant to health in one way or another.[224]

You may think: "so why doesn't everyone complain about mold if up to 50% of buildings are infected?"

Good question...

Answer: there's large variability between your individual capacity to handle mold toxins--there's also no current lab test definitively establishing that capacity.[214Based on the symptoms seen in thousands of individuals, nevertheless, it's safe to conclude that this variability exists.

One problem with combating mold is that a lot of scientific research still needs to be carried before diagnosis and treatment can be simplified.

But let's consider the question: "why is mold such a big problem today?" from another angle. Why didn't people living in Ancient Greece or the Middle ages have mold problems?

That's simple:

Humans only started relying on fully insulated buildings with airtight ecosystems in the 20th century.

Double walls, triple layer glass, less air circulating from outside into buildings, and maximized energy-efficiency all build on that principle.


If mold grows in an airtight buildings you'll be exposed as long as you spend time in that building. The mold thus stays "trapped" while clean air cannot enter.

A 1,000 or 5,000 years ago things were very different...

Primitive societies live in buildings such as huts. These buildings are often not fully airtight. These people additionally only slept inside--they don't spend their entire day indoors.

Remember that modern humans, on the contrary, spend 90% of their days indoors. Individuals living in hunter-gatherer societies only do so for 33%. 

Your modern airtight home thus becomes a toxic prison if mold grows there...

Another reason why mold used to be less of a problem is because in nature, the conditions in which mold can continually grow and spread are almost never present. Almost no situations exist wherein mold can grow for years in a specific medium while being fully isolated from the environment.

So you might be thinking: "how does mold affect me in the first place?"

The following analogy can help you imagine the effects:

Your body will have an immune response if you ingest moldy food. The same response occurs when you breathe moldy air.

While eating moldy food your immune response activates just once. Breathing mold, however, can force your immune system to continually activate (if you're sensitive).

So if you're spending up to 16 hours inside a moldy home your immune system is triggered all the time. As a consequence you'll become progressively more fatigued in time. 

The consequence is that you can no longer think straight, get tired, dizzy, and that's just the beginning. Again, people end up disabled or even die because they're too weakened to spend any more time in a mold-infested environment... 

That's tit, the mold basics you need to know. Next, number eleven - another danger you may know of: 



11. Asbestos

Asbestos is a mineral that can be highly toxic - if the particles become volatile.

The mineral naturally occurs in the soil, especially in rock, and has been mined for most of human history because of its special chemical and engineering properties. 

What properties?

Asbestos' ability to withstand tension and heat make it ideal material in construction.

Fortunately, almost everyone knows that asbestos is toxic today.

And even though asbestos' toxicity was officially understood in the 1920s, governments only recommended scaling back its usage 50 years later.[227; 228The asbestos industry additionally knew about the negative health effects of their products but kept information hidden for a long time.[229]

Many products made in the 1960s to 80s therefore still contained asbestos, such as insulation in walls and around machinery, piping for sanitation, roofing, floor tiles, and even clothing.

As often is the case with toxins, governments act once a problem can no longer be ignored (and when most damage has already been done). Sadly enough, government policy in response to toxicity is usually reactive. 

If you're living in a developed country today, your governments is probably extremely thorough in preventing asbestos pollution fortunately - giving credit where credit is due...

If asbestos is spotted in a US school, for example, that building will be inspected every three years to see whether the compound is not emitted into the air (unintentionally).

Asbestos is rarely damaging undisturbed. But when disrupted, asbestos-containing materials can enter your body through your airways.

Asbestos particles thus need to be released into the air in order to become health-damaging. 

If you're renovating an older home or you're removing asbestos insulation along water piping, you're at risk for asbestos' negative health effects. Of course, always get professional clean up for asbestos in your home or workplace. 

One of the most deceptive dangers of exposing yourself to asbestos is that it can take years before negative health consequences finally show up.

You won't feel anything - initially...

Two main asbestos health effects exist. Asbestos:

  1. increases your lung cancer risk, or cancer in the lining around the lungs.[230; 231; 235; 236If you smoke, the lung cancer risk from asbestos exposure will increase.[233; 235]
  2. decreases lung function.[232]

While that's a short list, these health consequences are not fun to experience at all. The list of consequences is somewhat similar to that of radon - with lung cancer as the primarily associated disease.


Don't break the stuff containing asbestos or make it volatile. And if you suspect problems due to asbestos exposure, a CT scan is best to detect lung cancer from asbestos exposure early on.[234] 

That's it...

Just two more air pollutants to cover.

Next up are toxic heavy metals, which are found both indoors as well as outdoors:



12. Toxic heavy Metals: Airborne Lead And Cadmium

First of all, have a sign of relief:

Airborne heavy metals have, fortunately, been declining steadily (in developed societies). 

Many heavy metals are toxic in very minute amounts. Lead and cadmium are examples of such heavy metals. While a heavy metal such as arsenic or mercury can also be emitted through the air, I'm restricting myself in order not to over-complicate this post (further). 

Keep in mind that heavy metals are not always toxic: you need some heavy metals in your system, such as iron and zinc

But back to the topic of toxic metals: let's being with lead...

Again, first a positive message:

The main reason airborne lead levels have been declining is that lead is no longer added to gasoline (in almost all countries).

Lead was added to fuel sources because vehicles run a lot better with it and engine performance goes up. That higher car performance comes at a terrible cost if you're around those cars of sitting inside of them, as you'll then be breathing in that toxic lead.

I have to give a compliment to governments here: airborne lead levels have fallen between 95-98% in the last decades.

Credit where credit is due...

A few problems though:

Some countries such as Algeria and Yemen still add lead to their gasoline.

Additionally, air travel is tragically not yet mandated to use fuel that doesn't have added lead. If you're living closer to an airfield, you're at risk of being exposed to (much) higher lead levels compared to those who don't live close to an airfield...

That's sad...

But why worry about lead in the air in the first place?

Let me tell you:

Lead affects almost any process in the human body. Lead:

  • lowers IQ in both children and adults.[248; 251] 

    Even small amounts of lead are damaging. Lead specifically interferes with several brain signaling substances such as "GABA", which is necessary for relaxation, and "dopamine", which is essential for motivation and assertive action.

    If you're exposed to lead as a kid it's difficult to recover your cognitive function later on in life.[255] Why? Well, higher lead exposure at the age of 11 can predict your social and economic status at the age of 38.

    That fact is scary...

  • lowers female fertility, and can even cause miscarriages.[251; 252

    There's no easy opt-out for us men though--male fertility is also negatively affected by lead.[278

  • gives you insomnia and lowers sleep quality.[256Heavy (toxic) metals often ruin your sleep cycle...

  • increases your risks for getting anxiety, panic disorders, and depression.[257Why? Lead is simply toxic to the nervous system.[265; 266

    The toxic metal even disrupts many basic processes of your (brain) cells.

  • negatively affects organ functions of your kidneys, liver, heart, and brain.[258; 260; 263] 
    In high doses, lead causes organ damage. 

    Your blood pressure also rises with more lead exposure. 


So how does lead end up in your body in the first place?

Let's find out:

Once lead enters your body through the airway, the bloodstream spreads it throughout the body.

Lead is even stored in your bones.

Please keep in mind that not all lead exposure thus occurs through air pollution from industry or fuel exhaust.

Lead can also be found in many paints. Buying paint that does not contain lead for your home is thus essential. Lead is still used in some workplaces - which is dangerous as well.[253; 254]

Bottom line: avoid lead like the plague...

Next, the second heavy metal "devil": cadmium...

Even though it's not as well known, cadmium has a similar profile as lead. And just as lead, cadmium is also a heavy metal and can be inhaled through air pollution.[266; 267]

Cadmium can cause organ damage to the liver,[268; 269] kidneys (although some conflicting evidence exists),[270; 274] brain and nervous system,[275; 276; 277] may promote male and female infertility,[278; 279; 282; 286] gives rise to different types of cancer,[287; 291; 374; 375] and much more...

(I confess: I'm almost done with these depressing lists...)

Keep in mind that research regarding cadmium is really rudimentary again.


Right now, it cannot be proven beyond a shadow of a doubt that cadmium does not inhibit fertility in humans (yet), even though many animal studies demonstrate that cadmium reduces fertility.

Some institutions insist that more research on cadmium needs to be carried out to definitively establish many of its negative health effects.

And there's (some) truth to that statement...

But I'm already recommending you to reduce your exposure as far as possible anyway. Why? Simple: an extreme number of negative health effects is already observed across the board due to cadmium exposure.[280; 281; 283; 284; 285]

I don't need to see 100 more studies on the negative health effects of cadmium - current evidence is already devastating...

The most common source of cadmium air pollution is, surprise, surprise: tobacco smoke.

Pointing at tobacco as the main culprit can give you a false sense of security though.


As a byproduct of industrial processes, such as the refinement of metals such as zinc, aluminum, or iron, cadmium can be released into the air around factories.[292; 295

If you're living around a cadmium-polluted area, for example, the amount of cadmium in your blood can be significantly higher than in non-polluted areas.

While tobacco smoke is thus most likely to poison you with some cadmium, high levels of cadmium from industry are most dangerous because you can get exposed to a very large dose instantly

Oh yes, I've got a present for nerds - just to demonstrate how complex the air pollution problem can be: 



13. Advanced Explanation (Bonus): Solar Winds And Flares From Space

Yes: while this air pollution type may sound counter-intuitive, space nevertheless has effects on the air quality down on earth.

Solar flares, for example, which are momentary increases in the sun's brightness, don't just entail that more light reaches the earth. Instead, mass is literally emitted from the sun that travels here. That mass emitted by the sun is bombarded on the earth.

Although different in character, energy from space is thus a form of "particulate matter exposure"...

If you're interested, watch the following video on particle matter pollution from space.

Contrary to many's expectations, solar flares and winds can have medical consequences. After an eruption from the sun, people with multiple sclerosis are more prone to have an exacerbation and be admitted to the hospital.[514Your heart and circadian rhythm also respond to solar eruptions.[515; 517Incidences of headaches, surprisingly, do not go up.[516

Of course, energy emitted from space also interacts with the earth's magnetic field, which is another mechanism by which the sun can create a form of particulate pollution. Unfortunately, the research into solar eruptions upon health is really rudimentary now.


That's it:

Thirteen different types of air pollution.

Please keep in mind that I've not even included all types of air pollution out there. Phthalates, which are contained in many beauty products, are not treated. Other heavy metals that can be polluting as well, such as arsenic or mercury.

Nevertheless, air pollution does have another side-effect that I need to tell you about:

Some types of air pollution have the devastating effect that they block sunlight from reaching the earth's surface.[368; 369; 371; 372; 411; 412; 413]

Yes, really.

So let's do a quick refresher on sunlight:

Sunlight emits several types of light, such as "infrared" light (part of which gives you heat sensations), "visible" light (consisting of all the colors of the rainbow), and "ultraviolet" light (which can give you a sunburn).

You need ultraviolet light exposure on your eyes to create more "dopamine". Dopamine is a brain signalling substance that gives you motivation and well-being while making you more assertive. 

Ultraviolet exposure to your skin is also essential to help you feel good and to produce vitamin D.

Both particulate matter and ozone preclude ultraviolet light from reaching the earth's surface.

One study - unfortunately published in Chinese - demonstrates that high air pollution levels lower ultraviolet light exposure from the sun up to 50%. 

That 50% reduction is insane.

Let's explore some examples that make you familiar with the effects of such a reduction:

If I'd be exposed to sunlight in the mid-summer in the Netherlands under heavy air pollution, ultraviolet light levels are reduced to mid-spring or early-fall levels.

Say goodbye summer...

Another example:

If I'm in southern Spain for a summer holiday and there's heavy smog there, the sun's strength would be equal that of southern Norway's level.

For nerds: southern Spain's UV index of 10 would be reduced to 5 (the estimated maximum at Oslo, Norway).

Very sad...

Keep in mind that the examples above signify extreme air pollutant levels. Nevertheless, you can always expect an effect of "sun blockade" if particulate matter or ozone are present...

Still think city life is optimal? 

Getting your daily sunlight in polluted environments is thus not optimal.


Advanced explanation: of course, the pollutants described above also interact, and their negative effects accumulate if you're exposed to a higher number of pollutants. Higher dosages are also more damaging...


Oh by the way, congratulations.

You've now completely read trough the depressing list of air pollution health effects. The next step is to look at measuring these effects in your unique circumstances and finding solutions.

The topic of air pollution measurements is treated first...



Finishing Thoughts: Onwards And Upwards, The Search For Solutions Has Finally Begun

Yes, I understand that this list of problems is kind of depressing. And yet, I've tackled the same type of problem in my guide about particulate matter. In the end, you are in control with your air pollutant exposure.


Well, in case of particulate matter, you can easily decrease your exposure by 95-99%+, using air purifiers and 7 other harm reduction strategies. The same is true for air pollution, so stay tuned for the last installment of this series on this topic.




This is a post by Bart Wolbers. Bart finished degrees in Physical Therapy (B), Philosophy (BA and MA), Philosophy of Science and Technology (MS - with distinction), and Clinical Health Science (MS), and is currently a health consultant at 


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