Is it nice when you cross a street and you have to breathe the car’s exhausts just in front of you? Of course not! We all prefer a deep breath of fresh and clean air.

In that case, why we face that situation so often? Do we have to stand it, and that’s it? Or is there anything that we can do, apart from wearing a mask?

Let’s have a look!

What is air pollution?

Air pollution is a mix of gases and other particles that are released in such a high concentration that can be unhealthy for people, plants or animals.

The same as with water pollution, the presence of a given substance in the air is not a threat by itself. It depends on the quantity released. For instance, Carbon Dioxide (CO2) is usually in the air that we breathe. It is not a problem in small quantities. But if the concentration of CO2 is big enough, it starts to be unhealthy, or it can even kill you.

Some people used to think that the Earth’s atmosphere is such a big thing that the wind could disperse in it almost anything. Well, today we know that this is not the best way to manage air pollution.

Air pollution is a problem which affects all of us, and it doesn’t care about your status. Whether you are rich or poor, we all breathe the same air around us.

Air pollution works on several scales, from very local to global.

Local air pollution

In this case the source of pollution and the effects are very close both in time and space. Think about yourself cooking at home. You get distracted and suddenly something is burning. Particles and smoke are released into your kitchen. This kind of air pollution is most of the times easy to deal with, but sometimes it can be fatal.

Neighborhood air pollution

Sometimes the quality of the air that you breathe depends on your neighborhood. The air is generally cleaner in green areas within the cities. On the other hand, the air usually is more polluted in areas of big traffic intensity.

Regional air pollution

Sometimes the source of air pollution systematically causes effects in another location which is far away. This is a typical case of winds blowing usually in the same direction and tall smokestacks. The wind carries the polluted air, which finally drops somewhere else with the rain. The air pollution doesn’t care about political borders. Source and effects could be easily located in different countries.

Global air pollution

This take place when we do something that can damage the entire planet. Our daily actions can have an impact on global warming, damage the ozone layer or contribute to climate change.

I know that there is a lot of controversy with these topics. Some people truly believe that human actions have been causing the damage. Other people are completely against that idea. In any case, everybody should agree that the more environmentally friendly our actions are the better. And for sure nobody wants to breathe polluted air.

Types of air pollution

Primarily and secondary pollutants

Pollutants which are a direct result of a process are known as primarily pollutants, while pollutants formed by reactions of primary pollutants are known as secondary pollutants.

Sulfur dioxide (SO2)

SO2 forms when sulfur-containing fuel such as coal, oil or diesel is burned with oxygen from the air. Coal-fired power plants and some industrial ports are the main source of SO2.

Not only human action spreads SO2 into the air. Volcanic eruptions can spew massive amounts.

Carbon monoxide (CO)

CO comes from burning fuels when they have little oxygen to burn completely. This a very common case when it comes to car exhausts. Be careful indoor if you have a gas boiler or any fuel –burning appliance, and maintain it properly.

Carbon dioxide (CO2)

CO2 is not a pollutant itself. We all produce CO2 when breathing out. Green plants and other organisms need it for their photosynthesis. The problem comes because in high concentrations it is a greenhouse gas. It is mainly released by engines and power plants.

Nitrogen oxides (NOx)

Nitrogen dioxide (NO2) and nitrogen oxide (NO) are produced during combustion, as a reaction of nitrogen and oxygen from the air. Nitrogen oxide pollution is produced by vehicle engines and power plants.

Volatile organic compounds (VOCs)

These are carbon-based chemicals used as solvents in paints, varnishes, waxes, etc.

Particulates Matter (PM)

These are a mix of solid and liquid deposits in the air, which cause breathing problems. They usually come from smokes and traffic fumes. These particulates can be of different sizes. They are referred as PM followed by a number which stands for the maximum diameter of the particulate measured in micrometers ( 1×10−6 meters). PM10 and PM2,5 are the most used ones. The smaller its size the farther they can travel into your system, and the more dangerous for your health.

Ozone (O3)

The ozone layer is a band of O3 in the stratosphere which protects us from ultraviolet (UV) radiation of the sun. Nevertheless, at ground level O3 is a very toxic pollutant, and is the main ingredient of smog.

Chlorofluorocarbons (CFCs)

CFCs were commonly used as aerosols and as coolers in refrigerators till they were banned in 1980s, after discovering that they were deteriorating the ozone layer.

Unburned hydrocarbons

If petroleum and other fuels don’t burn completely, they can release CO or remain floating into the air in small particles.

Lead and heavy metals

Heavy metals can be spread into the air by aerosols and exhaust fumes from industries.


The term smog comes from “smoke” and “fog”. It takes place when sunlight reacts with a mixture of primary pollutants. The most toxic element of smog is the O3 at ground level. Smog is usually brown, but it can turn into a kind of blue if the presence of O3 is high enough.

Smog usually affects cities with very high traffic levels, but the particular conditions of wind, rain and orography play an important role also.

Causes of air pollution

The main contributor by far of air pollution nowadays is traffic. Power plants and industries are also important contributors. Most of us drive or use cars, buy stuff produced in factories and use electricity. Besides, anytime you burn something, or use chemicals, or produce big amount of dust, you are spreading pollutants into the air.

Traffic and transportation

Every kind of vehicle (car, bus, train, airplane, boat) running on combustion engine is emitting a large number of pollutants: CO, NOx, VOCs, lead, and others. Vehicles can also release air pollution from brakes and tire wearing and tearing. Vehicles also create water pollution.

It is obvious that we all need to fulfill our transportation needs, but overuse of cars and other transportation systems has a severe impact in the air quality.

In rich countries, there is one car for every two people!

Power plants

In USA, 70% of electricity still comes from conventional power plants burning fossil fuels. These kind of power plants produce a large list of pollutants: SO2, NOx, CO2, PMs, etc.

Renewable energy production is growing every year, but there is still a long way to go.

Factories and industries

Manufacturing factories, plants that produce goods, refineries, producers of metals, cements or plastic, are examples of industries that produce air pollution. Unless there is an accident, these kinds of plants tend to release small quantities of pollutants, but in a constant fashion.

Agricultural activities

Some of the fertilizers and pesticides used in agriculture activities contain very toxic products, which can cause air and water pollution.

Mining operations

During mining operations a lot of dust and chemicals are spread into the air, causing air pollution. Unfortunately, it is common to see around mines workers and people living there who are affected by these processes.

Household and indoor air pollution

Normal activities at home like painting the walls or some cleaning products make the indoor air not breathable. Gas boilers, chimneys and stoves are a potential danger if not well maintained. A good option to improve the quality of the air at home is an air purifier.

Garbage incineration

In some cold countries, garbage is incinerated, even at a domestic scale. These actions can cause very dangerous air pollution.


Air pollution is not only produced by human actions.

The wind can carry dust from deserts. Living beings release gases when breathing or digesting. Volcanos can release huge amounts of pollutants at once. There are also many natural processes of combustion and fermentation.

Why and how do we measure air pollution?

Even if you don’t see smog, it doesn’t mean that the air quality is good enough and healthy. The problem is that most of the times we can’t see air pollution. That is why we have to monitor and measure the air quality. This monitoring is even more important near schools, hospitals and workplaces. Unfortunately, low-income countries are not fully prepared for this.

The World Health Organization (WHO) has established air quality guidelines values, and an online pollution meter to help people understand how polluted the air they are breathing is.

Air Quality Index (AQI)

AQI is a tool to provide easy and understandable information about local air quality. It also gives information about the effects you may suffer due to air pollution, and how to protect yourself from them.

The AQI considers four major air pollutants: ground level O3, PM, CO and SO2. Different countries have their own air quality indices, corresponding to different national air quality standards. For example, in Europe the Common Air Quality Index (CAQI) is the air quality index used since 2006.

In USA, the Environmental Protection Agency has set six different levels of health concern:

Effects of air pollution

Health problems

According to WHO 7 million people die every year due to the combination of outdoor and household air pollution. Also according to WHO, 9 out of 10 people breathe air with pollutants. In urban areas, 80% of population breathes air with a quality below de WHO guideline limits.

Air pollution increases the risk of stroke, heart disease, pulmonary disease, lung cancer and all kind of respiratory infections. Air pollution can also cause short-term problems such as sneezing and coughing, eye irritation, headaches, and dizziness.

Effect on wildlife

Not only humans suffer from air pollution effects. Sometimes animal species have to move to a new place due to excess of pollutants in their original habitat.

Global warming

CO2 and other greenhouse gases are contributing to create a layer in the atmosphere which is making the global temperature rise. This fact can have effects like increase in sea levels and melting of ice from the North and South Poles, or displacement and loss of habitats.

The mainstream scientific organizations assess that warming over the last 50 years is likely due to the human-caused increase in greenhouse gas concentrations. There are also some scientists in climate and climate-related fields that disagree with the consensus view.

Acid rain

When it rains through air pollution, the water droplets combined with pollutants like SO2 become acidic. This phenomenon is called acid rain.

Pure water is neutral (PH 7,0), while rain water is a little bit acidic. The problem appears when the rain becomes more acidic than that, changing the acidity of lakes, rivers or grounds. Fishes and other animals start to die when the water PH drops under 6,0. It also affects to crops.

Monitoring and controlling acid rain is very difficult. SO2 can be released in a given location, and transported afterwards hundreds of miles away, and finally produce acid rain very far away from the source of pollution.

Depletion of the ozone layer

As mentioned before, the ozone layer is a band of O3 in the stratosphere which protects us from UV radiation of the sun. An excess of UV rays can hurt eyes and skin, and can also affect agriculture and crops.

The presence of CFCs and other pollutants in the atmosphere caused the ozone layer to deplete. During the 1980’s the ozone hole was of such a magnitude in Antarctica that many countries got aware and signed the Montreal Protocol. This international treaty was designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion.

What can we do to avoid air pollution?

Air pollution is not a single problem, but the combination of many different factors. As a result, we need to follow many different ways to tackle each of the factors.

But one thing is for sure, accountability is the beginning of everything here. Individuals, families, communities, regions, countries and international associations have to push in the right direction.

Technological solutions

Even though it is not always the easiest and fastest way, the creation of new technologies is helping to reduce air pollution. This is the case of renewable energy technologies and new energy efficient industrial processes. Cars are equipped with catalytic converters to reduce exhaust emission. Electric vehicles have become a real alternative. Power plants have systems to minimize the emission of pollutants into the air. New products are substituting the old toxic chemicals in aerosols, fertilizers and in many other fields. Household devices are more energy efficient now, and home energy recovery systems are getting more and more popular.

Laws and regulations

Many cities are now enjoying a clean air thanks to the laws introduced during the second part of the 20th century. Unfortunately, many of these laws were introduced after people getting killed by air pollution tragedies, like the one in London in 1952.

In USA, Pollution Prevention Act tends to focus on prevention rather than on cleaning up pollution.

Air pollution is a global issue. It easily crosses countries and continents, so different standards in different countries are a major problem.

International law plays a key role here. As the awareness of global society grows, some governments are taking actions to apply new international common laws to protect the environment and reduce emission. Let’s hope that countries which so far are not that much interested will join soon.

Successful policies that reduce air pollution

There are many policies which are successful and are helping to reduce air pollution in sectors like industry, energy, transport, urban planning, power generation, municipal waste management and agriculture.

Awareness and education

It is not possible to solve a problem if we are not aware of it. That is why helping people to understand the causes and effects of pollution is so important. We are in the era of social media, and it can be a great tool to make the whole world aware!

Education on environmental issues is a must for our kids. As they grow and get involved in routine and productive activities, they will transform the old bad habits into good practices.

Anyone can help to reduce air pollution. Here you have 10 tips to start right now:

  1. Save energy by using energy efficient devices.
  2. Save water whenever you can.
  3. Cut the car and use public transport. Even better, walk or bike if possible!
  4. Cut out garden bonfires.
  5. Never burn household waste.
  6. Garden organically.
  7. Cut the chemicals.
  8. Use water-based paints and glues.
  9. Reduce, reuse, and recycle.
  10. Don’t smoke.


As a general approach, prevention is cleaner and more environmental friendly than reparation. In this sense, the idea of the polluter pays principle is not only based on paying to clean up. It means that polluting will result more expensive than to invest in operational systems to avoid pollution.


At this point, the same as with water pollution, I am sure that everybody agrees that air pollution is an essential subject for all of us. The more aware we are the closer to solve it.

Air pollution is hard to escape, no matter how rich or important you are. Air is the same for everybody, and we all can be damaged by air pollution. We have to be accountable.

The awareness of air pollution is growing constantly, and it is even a major social concern in some countries. We are not where we want to be, but we know the way to get there. Let’s lead this positive tendency!