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What is the most polluted air in cities? – I like science

What is the most polluted air in cities?  - I like science

The number of passenger cars began to grow rapidly at the beginning of the twentieth century, when Henry Ford and his successors, thanks to the improvement of production technology, began to bring them to the market en masse. Cars are becoming cheaper and therefore more accessible to a growing group of people. But what is the thing that pollutes the air the most? Car exhaust fumes only?

It is estimated that there are approximately 1.5 billion cars in the world today. This is one car on average for about 7 people. It sounds innocent, but… it’s a statistic about the entire world. When you look at developed countries, the situation is different. The leader in this ranking is the United States, where there are approximately 0.9 cars per capita. New Zealand is second, with practically the same score, and Canada is third, with approximately 0.8 cars per capita. Interestingly, Poland is among the top ten with a very similar score to Canada.

What is the most polluted air?

We are well aware of the devastating impact of smog on the environment. What causes smog? Often, in the context of smog and air pollution, the so-called low emissions, for example from low-quality furnaces or due to low-quality fuel. There is already enough material on this topic.

How does road transport affect air quality? How is it that in cities where stoves are banned, air quality still leaves much to be desired? And even more so – why does the air quality in cities leave much to be desired even in summer, when no one smokes in the stoves? Cars are the answer.

This will also interest you: How to teach a child environmental empathy? Learn practical tips

Since we have a lot of cars and we exploit them a lot, it can’t be without affecting air quality. Do you realize that a million cars cross the Warsaw border every day? Many of them get stuck in traffic jams, and yet almost no one turns off the engine in traffic jams.

In large cities, the effect of vehicular traffic on the content of harmful nitrogen oxides, or on the cleanliness of the air in general, is very large. This effect reaches tens of percent and increases towards the centers of these cities. For example, it is estimated that the proportion in central Warsaw is as high as 90%.

How is smog formed?

The main problem of increased car traffic is the side effects of burning gasoline or crude oil in diesel engines. Exhaust gas contains nitrogen oxides and hydrocarbons, which seep into the environment and into the air and remain there thanks to the high temperature. When exposed to sunlight, it turns into ozone, which is harmful to breathing. This is how photochemical smog is created.

When there is no wind, the intensity of this smog can already be very high. Aside from major collisions or some tank malfunctions, vehicular traffic primarily causes air pollution.

But the problem is that air, soil and water are in constant contact with each other. Air circulates and water circulates and pollutant particles move freely between all the above-mentioned elements of the environment in the city.

How does smog affect the environment?

Cars, in addition to exhaust emissions from the exhaust pipe, can pollute the environment in other ways – for example by emitting dust and steam as a result of friction of the brake blocks, or by restarting pollutants already deposited … by moving wheels on the road.

This procedure of brake lining should not be ignored. It is estimated that in this way up to 0.5 grams of environmentally harmful dust is produced from one car each year. A simple calculation allows us to estimate that 2,000 passenger cars per year, in a large city, can emit up to a kilogram of dust from corrosion of the brake blocks.

How does smog affect health?

It is clear that air and environmental pollution in cities has an impact on our health. There are estimates that the average lifespan of a city is prolonged just by lowering the level of pollution – even to the level of WHO guidelines.

What can we do to make transportation less environmentally friendly? I have two solutions. We can try to change the transfer technique to a less stressful one. For example, the electric car sector is developing, and hybrid cars are becoming more and more popular, or with the technology already in place, try to organize this transportation in a more controlled way and less harmful to the environment.

See also: Are electric cars environmentally friendly?

Recently, on September 22, 2022, we celebrated European Car-Free Day, and people in many cities had the opportunity to use free transportation. After all, one bus replaces many passenger cars on the road, and it can carry an incomparable number of passengers.

Another idea to reorganize the traffic of cars, by the way, helps protect the environment Clean Transportation Zones. Work is underway to introduce them in cities with a population of more than 100,000 people, where the air quality is insufficient.


The issue of electric and hybrid cars is more complex than it might at first seem. I think I’ll do an episode on that in a while. As for clean transfer areas, anticipate the material earlier, because it is a very hot topic right now.


The material was created in cooperation with Clear Air Fund.

Selected sources:

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Thomas Roshik

I am a physicist by education and a science journalist by profession. I’ve been creating the Nauka brand for years. I like that, in addition, I run the research department of the weekly Gość Niedzielny and collaborate with several media and editorial offices. I am a happy father to twins: Zozia and Janek and Anya’s husband.

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