Breathing freely is important; in fact, it’s something most of us make a point of doing. It’s even made its way into our vocabulary: a creative idea is a breath of fresh air. If it’s really useful and not just a last gasp, it might even cause you to breathe a sigh of relief. When it solves some kind of problem, you’ll have some breathing space and nobody will breathe down your neck.

It’s actually a shame that we take air quality for granted much of the time. In the past, ignoring the dangers of atmospheric pollution has led to disaster. During the Great Smog of 1952 in London, for instance, over 10,000 people died and another 100,000 became sick – and the event only lasted 4 days.

Improved emissions legislation has made such a disaster much less likely, but we’re definitely not out of the woods. Worldwide, today, an estimated 7 million people die annually as the result of indoor and ambient air pollution. You may think that you and your family are safe, but there’s a good chance you’re not. To better understand the risks, it makes sense to first look at AQIs: Air Quality Indices

Understanding Air Quality Indices (AQI’s)

Although every air quality index has a scientific basis, most countries have their own. Regional differences may occur due to using different epidemiological data (studies linking pollution levels to disease), what’s practically achievable in terms of controlling pollution, and perhaps political lobbying.

The discrepancies can be pretty wide, though:

Original Image, copyrighted. Can be used when given attribution
Data derived from this EEA publication

So if we take the average of the 2014-2016 period, according to E.U. guidelines, only 18% of people living in urban areas are at risk of health problems due to ozone (O₃), yet this figure rises to 97% when applying the stricter World Health Organization limits!

This may seem bizarre and alarming.

The thing to remember, though, is that any increase in pollution increases the risk of illness. Considering that these diseases include lung cancer, stroke, pneumonia and heart disease, it’s always worth paying attention to the rise and fall of AQI figures.

How is AQI Calculated?

The basic idea behind air quality index numbers is to give ordinary people something they can check at a glance to help plan their day or week. This means that the result usually boils down to a single number, sometimes along with specific warnings.

For practical reasons and because it’s usually not necessary, not every kind of pollutant is included in the AQI calculation.

Most commonly, sulfur dioxide, ozone, particulates, nitrogen dioxide, and carbon monoxide are measured, but the exact mix varies by country. Chemicals like VOCs (Volatile Organic Compounds) and chlorine are normally not checked, as their contribution to health problems tends to be minimal in most cases.

The next major difference internationally lies in how gas concentrations in different parts of a city or province are thought to lead to different public health outcomes. Some government bodies use complex equations based on the combination of different harmful gasses, while others use the figure corresponding to the most dangerous pollutant on any given day.

What do AQI Values Actually Mean?

You can find AQI measurements and forecasts on the relevant website, or they may be given along with the local weather report.

To make them easier to understand, results from pollution monitoring stations are boiled down to a simple number, color-coded depending on the level of risk. Each color comes along with a standardized recommendation, for example: “Consider reducing or rescheduling strenuous outdoor activities.”.

Table from the California Air Resources Board

In the United States, AQI numbers run from zero to 500. 100 is the maximum “safe” level recommended by the Environmental Protection Agency: anything below this should represent very little risk for most people. As the number rises, more and more people are likely to be affected in ever more severe ways.

A sharp uptick in the AQI number may be due to unusual events like nearby wildfires, but more commonly happens when a temperature inversion over a city or low wind speeds make pollutants dissipate more slowly.

Here’s an example of how rapidly AQI numbers can sometimes change, even prompting people with asthma or heart conditions to evacuate the area:

Lily Morrison (University of California San Francisco) (CC BY-SA 4.0), via Wikimedia Commons

When something of this magnitude happens, short of suggesting you run for the hills, government may advise at-risk groups to stay indoors and avoid specific areas. They might also appeal to people to drive only when necessary, order factories and power plants to shut down until the crisis has passed, or even start distributing special breathing masks to local residents.

What Are the Main Air Pollutants and Causes?

Aside from carbon dioxide and methane, the two principal greenhouse gasses, there are numerous kinds of air pollution that affect human health. This may happen either through a short but harsh exposure, or by long-term contact with lower concentrations.

In either case, the risks are certainly real. This article is too short to discuss all harmful compounds, but we’d like to touch on a few of the most dangerous:

Ozone

When it’s at very high altitudes, ozone (O₃) literally makes it possible for life on earth to exist by blocking the sun’s more harmful rays. Breathing it in, however, is not something you want to do.

Ozone is formed naturally in the stratosphere and doesn’t descend to the surface. In city air, however, sunlight can cause other types of pollutants to break down into ozone, especially on hotter days.

Source: Max Pixel

Ozone is highly reactive and attacks the lungs and airways on contact, leaving its victims coughing, short of breath, and more vulnerable to infections. Anyone with an existing respiratory condition should steer clear, moving inside if possible.

Particle Pollution

Numerous human activities – truck tires slowly disintegrating, power stations burning coal, driving your car – result in tiny specks of dust or other substances, particularly soot, floating around in the atmosphere. They can stay up there for quite a while and even attract other noxious chemicals to their surface.

When talking about air pollution, particulates are classified into PM₁₀ and PM_2.5 categories, smaller respectively than 10 and 2.5 micrometers (0.0004 and 0.0001 inches). Their size is what makes them so dangerous: they can travel deep into the lungs, causing inflammation, and even pass through bronchial walls into the bloodstream.

Particulates are also carcinogenic, meaning that they cause lung cancer. Anyone with breathing difficulties or a heart condition should limit their exposure to this type of pollution whenever possible.

Carbon Monoxide

Carbon monoxide is formed when something burns without complete combustion taking place. Small amounts are produced in household appliances that use propane or natural gas, by automobile engines, from coal-burning power plants, and in several other ways.

Although it is usually found in air at only the tiniest concentrations, carbon monoxide is extremely toxic and a real killer. Though everyone should be on their guard, children, people with existing cardiovascular conditions, and pregnant women are especially at risk.

Sulfur Dioxide

SO₂ is only one chemical compound in the sulfur oxide family, but it’s probably the most harmful. It’s produced naturally during volcanic activity and is also released whenever fossil fuels are burnt.

Brocken Inaglory (CC BY-SA 3.0), via Wikimedia Commons

One of the results of having too much sulfur dioxide in the air is that acid rain is produced whenever SO₂ encounters water. This damages buildings, can make farmland infertile, and has a very negative effect on lakes and waterways.

When inhaled, it causes extreme irritation to the airways, meaning that anyone with a condition such as asthma and emphysema should avoid it at all costs. There are also indications that it can induce premature labor in pregnant women. Luckily, this gas smells extremely bad even at low concentrations, which provides some warning.

Facts & Figures on Air Pollution

Trivia time!

• The four kinds of pollutant mentioned above are the most important to know about, but around 200 others are legally regulated in many countries. These include things like industrial solvents and airborne chemicals which contain heavy metals.
• Regardless of what you may have heard, more than 90% of scientists believe that there’s a strong connection between air pollution and climate change.
• Air pollution also has an unequal but opposite effect called global dimming. Essentially, particles and chemicals in the air encourage clouds to form, reflecting more sunlight back into space and cooling the atmosphere. If all pollution were to magically cease tomorrow, Mother Nature might reward us with a barrage of floods, hurricanes, and other extreme weather events unlike any before it.
• You would expect air pollution to be a bigger problem in heavily industrialized countries, but this isn’t the case. More people die from this cause in poorer regions where coal plants are still the primary source of electricity and cooking is often done using fire.
• In the U.S.A, approximately 35,000 people die each year in vehicle crashes. The number of deaths related to air pollution is currently estimated at about 50,000. However, this is actually good news: the figure for 1990 was 135,000.
• The average adult breathes in about 2 gallons of air per minute, or 3,000 gallons (11,500 liters) per day. This means that even small amounts of toxins can add up quickly.
• There are cheap air quality sensors available that you can strap to your bicycle. These include a GPS and use a mobile app to share and view air quality data from all over the world. All of its users form a data-gathering network that’s become hugely valuable to researchers.
• The world’s two biggest air polluters (at least in terms of carbon dioxide, which tracks other kinds of emissions closely) are China (29% of total) and the United States (14%). In per-person terms, however, China pollutes at about half the rate of the U.S.
• Lead used to be part of an additive in gasoline, but was phased out partly due to concerns about the effect exhaust fumes have on children’s mental development. 22 years later, every decline in the use of leaded petrol was followed by a drop in the crime rate – though the idea that children started growing up smarter and healthier isn’t the only possible explanation for this.
• Thailand actually sprays water from trucks and drones when pollution in their capital gets dangerously bad. In much the same way, increasing the humidity in your own home improves the air quality by helping to trap harmful particles and molecules.

If you want to find out how polluted or clean the air around your nearest town is, click the link below this map:

WHO map of global ambient air polution – click here to zoom in on your town

Which are the Most Polluted Cities?

When comparing pollution levels in different places, it’s customary to use PM_2.5 figures (i.e. particulate levels) for simplicity and because these tend to reflect other forms of pollution fairly well. It’s also common practice to use annual average figures, or some cities will get a free pass if their air happens to be checked only during the rainy season.

Despite what you may think, Beijing isn’t the most polluted city in the world; not even close. Cities in India and its neighbors occupy 16 of the top 18 spots, the other two both being located in Central Africa.

In fact, the only “modern” city you’ll find near the top of the list is Doha, Qatar at 20^th place, and the only Western Hemisphere cities in the top 100 are in Chile. You can find the full list here on Wikipedia.

Certainly, there are a lot more people living in the Third World, so you’d expect to see poorer cities dominating a list of any kind.

Once countries have industrialized and people are able to live a little more comfortably, preserving the environment automatically becomes more important to them. As far as sustainability goes, this is one of the better pieces of news for our planet.

Avoiding Air Pollution and Unhealthy Air

At Home

• Improve Ventilation: Especially during winter, some toxic gasses (formaldehyde, carbon monoxide, radon, and others) can build up indoors simply because not enough of the air inside is traded for fresh, outdoor air. Opening a window from time to time or installing an extraction fan in your basement may help a great deal.
• Buy an Air Purifier: A typical air purifier helps with both outdoor gases that are entering your home, as well as indoor menaces like mold spores and airborne germs. Depending on how large a space you need to service, they can also be quite pricey.
• Shop Green: When buying furniture, electronics, or materials such as paint, it’s a good idea to choose items with low levels of volatile organic compounds, which will gradually seep into your home’s air over the course of years. Products conforming to Underwriters Laboratories GreenGuard certification program or with a Green Seal label are good things to watch out for.
• Say No to Smoke: Tobacco smoke contains upwards of 200 chemicals known to be bad for you. Incense which isn’t organically produced is not quite that bad, but its artificial fragrances can become toxic when burned.
• When in Doubt, Verify: There are numerous companies that specialize in testing indoor air for a variety of toxins and even some do-it-yourself analysis kits. If you’re getting suspicious about whether the air inside your home is fit to breathe, and especially if more than one person living there has similar symptoms, making use of one of these can save a lot of trouble in the long run.

On the Move

• Make a habit of checking each day’s AQI number, perhaps by installing an app. If you do this every day, your chances of being caught out and perhaps suffering a very unpleasant experience go way down.
• If you prefer to exercise outside, try jogging or cycling as far from heavily trafficked roads as you can.
• If you have to go out, but the AQI number seems a little high to you, try to run your errands as early in the day as possible – pollution is usually more severe in the afternoons.
• When particulate pollution is particularly bad, many people resort to wearing breathing masks. You should know, however, that ordinary dust masks aren’t nearly good enough – rather, look for a specially-designed mask at your local pharmacy.

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Over the long term, the only way the problem of air pollution is going to be solved is if we all, both as societies and individuals, change our behavior. Until then, the best we can do is try to keep ourselves safe, and arming yourself with reliable information is the first step toward doing that.