Which air pollutants contribute to asthma?

Fine dust, nitrogen oxides and Co: The most dangerous air pollutants

Fine dust (PM 10, PM 2.5 and ultrafine particles)

Fine dust is a complex mixture of solid and liquid particles. They are divided into PM (particulate matter) 10, which have a maximum diameter of 10 micrometers (µm), PM 2.5 - with a maximum diameter of 2.5 µm, and ultra-fine particles, which have a diameter of less than 0.1 µm have.

How is fine dust created?

Primary fine dust is mainly produced by vehicles, power plants, heating systems and stoves in residential buildings. Fine dust is thus created in various combustion processes. But brake and tire wear are also responsible for the formation of fine dust.

Natural sources of particulate matter include volcanic eruptions, forest fires, and the stirring up of earth's crust material such as sandstorms.

Health hazards

Prof. Barbara Hoffmann from the Institute for Occupational, Social and Environmental Medicine in Düsseldorf explained the dangers of various air pollutants to us:

"Fine dust can affect almost all organ systems, especially the respiratory tract. We know that fine dust triggers inflammation in the lungs. This is especially true for people who already have a pre-existing condition such as asthma or a chronic obstructive pulmonary disease.

Particulate matter in the lungs can also cause lung cancer, and particulate matter can affect the cardiovascular system. If the particulate matter level rises, more heart attacks and strokes will occur in the following 24 hours.

We also know that in those who live long-term in an area with high levels of air pollution, the fine dust accelerates processes that affect the vessels - such as vascular aging. That means: there is more inflammation in the body, there is more calcium deposits on the vessels. They then no longer work so well. They can no longer contract and expand so well. The blood pressure rises, we develop arteriosclerosis faster than normal with all the potential consequences.

It is now relatively certain that fine dust also affects the brain and very likely sets off premature aging processes there too. We now have pretty good evidence that particulate matter promotes diabetes mellitus. And we know that fine dust affects the birth weight of unborn babies and leads to a reduced birth weight. This in turn can cause more illnesses and deaths. The effects of fine dust are very diverse. "

Nitrogen oxides (NO and NO2)

The term nitrogen oxides denotes various gaseous compounds. They are made up of the atoms nitrogen (N) and oxygen (O). Nitric oxide (NO) and nitrogen dioxide (NO2) are the two most important. The nitrogen oxides belong to the so-called "mass pollutants" in the air. In Germany alone, more than a million tons of it is released every year.

How are nitrogen oxides formed?

They arise from reactions in combustion processes such as those from exhaust pipes and chimneys. Nitric oxide (NO) develops with atmospheric oxygen in the outside air into what is known as secondary NO2.

Health hazards

Hoffmann: "NO2 is an irritant gas. If you inhale it in higher concentrations, it initially irritates all mucous membranes. You would feel a burning sensation in your eyes, for example. This irritant gas can penetrate relatively deep into the lungs because it is poorly water-soluble. It can then lead to inflammation deep in the lungs. This particularly affects people who already have a previous illness, such as asthma or chronic obstructive pulmonary disease. They may then have more frequent asthma attacks or shortness of breath. We have now also seen that the frequency of death increases on days when nitrogen dioxide is more abundant in the air. "

Sulfur oxides (SO and SO2).

There are several different sulfur oxides such as sulfur monoxide (SO) and sulfur dioxide (SO2). Sulfur dioxide (SO2) is colorless. It is a poisonous gas that has a pungent odor and a sour taste.

How are sulfur oxides formed?

They arise from the combustion of sulfur and fuels containing sulfur, such as coal, heating oil, diesel and gasoline.

Health hazards

Hoffmann: "Since our coal-fired power plants have generally been desulphurized, our sulfur dioxide emissions have dropped significantly. We only have relatively low levels of sulfur dioxide here in Germany. It is - just like nitrogen oxide - an irritant gas that It can cause inflammation in the lungs. In principle, it can have the same effect as nitrogen oxide. But since the values ​​in Germany are relatively low, there are not as serious problems as with nitrogen dioxide. What is also important: Both are precursors for the formation of fine dust and thus have an indirect effect on health. "

In other regions of the world, flue gas desulphurisation has not been implemented as consistently as in Germany. Especially in Asia, the air pollution with sulfur oxides is therefore still very high and the air in the cities is often very bad.

Ammonia (NH3)

In the atmosphere, ammonia reacts with various other gases, and particles develop (secondary fine dust). Ammonia is naturally deposited as an ammonium salt. Ammonia is a neurotoxin and can harm fish in water, for example. It can also damage plants and pollute soils. The ammonium causes acidification of the soil on the one hand and enrichment in the soil on the other. Ammonia is slowly broken down in the soil and converted into nutrients - nitrites and nitrates.

How is ammonia formed?

Agriculture has the largest share in the formation of ammonia. It is responsible for around 95 percent of this pollutant. It does not apply to cattle, pig and poultry farming and also to the use of mineral fertilizers.

Ammonia can convert to one of the many other nitrogen-containing compounds. This in turn has consequences for the quality of the air we breathe, for example through the formation of fine dust and ozone.

Health hazards

Since ammonia can turn into fine dust, it is just as harmful. It can cause cardiovascular and respiratory diseases. The same applies here: Previously injured people, such as asthmatics, are particularly at risk.

Ozone (O3)

Ozone close to the ground that we breathe is considered a secondary pollutant. When exposed to strong sunlight, it is formed mainly from nitrogen oxides and the so-called volatile organic compounds (NMVOC) via complex photochemical processes.

How is ozone created?

The precursors of ozone are primarily man-made: The organic compounds are often gases from solvents - from paints and varnishes, for example, or from cleaning agents. Road traffic also generates such volatile organic substances - for example when fuels and lubricants outgas. But they also occur in nature: for example in the fumes from deciduous and coniferous trees.

Health hazards

Hoffmann: "Ozone is an irritant gas and also has an effect on inflammatory processes in the lungs. We know that ozone increases mortality in the short term. There are also initial studies which show that it increases in those who are exposed to ozone over the long term This in turn is probably triggered by the increased inflammatory reaction. The blood clots faster than it normally would. Then heart attacks, strokes and the like are more likely. And here, too, there is effects on the lungs with asthma and shortness of breath. "

Professor Barbara Hoffmann is working group leader at Institute for Occupational, Social and Environmental Medicine of the University of Düsseldorf

  • Dangerous dust from the Sahara

    The calm before the storm

    First, the fine sand of the Sahara is whirled up close to the ground. High wind speeds quickly blow the dust to great heights and often as far as Europe. The sand in itself is not necessarily a health hazard, the particles are too large for that. Dangerous are the stowaways who use the dust as a ride.

  • Dangerous dust from the Sahara

    Illegal immigrants

    According to the German Meteorological Service, strong winds blow 1.8 billion tons of mineral dust into the northern hemisphere alone. In 2014, a huge amount of sand reached the Alps and even colored the snow. A team of researchers from the Edmund Mach Foundation in Italy and the university in Innsbruck, Austria, examined the dust and found many foreign bacteria and fungi.

  • Dangerous dust from the Sahara

    Microbe glut

    The microbes from the desert are "extremely stress-resistant and have thick cell walls," says Tobias Weil from the Edmund Mach Foundation, one of the study directors. The organisms are tough: they also feel good in completely foreign habitats. In winter, the microbes accumulate in ice and snow. When the glaciers melt, there is a real flood of microbes. With unclear consequences.

  • Dangerous dust from the Sahara

    Asthma, bronchitis, allergy

    Dust in the air has increased by 25 to 50 percent over the past century, warn the United Nations. The desert-like areas are enlarged by intensive agriculture and slash and burn. The wind has easy play and carries away loads of dust with it. Where it goes down, asthma and bronchitis pile up. In addition, allergens, bacteria and fungi in the sand cause problems for allergy sufferers.

  • Dangerous dust from the Sahara

    Questionable or not?

    Mushrooms like this one were blown over the Alps with the Sahara sand in 2014 and ended up in the snow. Researchers from the ecological institute at the University of Innsbruck collected samples of the yellow-colored snow and placed them on agar plates. The result: along with the sand, the entire range of microbes in the Sahara is blown to Europe.

  • Dangerous dust from the Sahara

    A piece of desert in Bavaria

    The sky over Germany, clouded by Saharan dust? "It's something natural that has always happened," says meteorologist Werner Thomas from the German Weather Service. The scientist explains that sand reaches southern German soil up to 25 times a year. Most of the dust reaches the Alps in spring and summer, most recently in large quantities in 2014.

  • Dangerous dust from the Sahara

    Less often in Hamburg too

    Sometimes the Sahara sand makes a detour and first reaches Europe in the north. The dust then traveled 6,000 to 7,000 kilometers. But even that can withstand the microbes that have traveled with them. The researchers from Austria and Italy fear that the robust intruders could be a danger to humans, animals and plants.

    Author: Julia Vergin

  • Respiratory masks put to the test

    Smog alarm

    City dwellers try to use masks to protect their lungs from the increasing fine dust pollution in Asia. Many believe that they are safe.

  • Respiratory masks put to the test

    Deadly fog

    Fine dust particles below 2.5 thousandths of a millimeter in diameter are particularly dangerous. They penetrate the deepest into the lungs and from there enter the blood vessels. But which respirator offers the best protection against them?

  • Respiratory masks put to the test

    Clarity through science

    The actual effect of the masks has only recently been investigated. Scientists from the University of Massachusetts tested four of the most popular models on sale in Kathmandu.

  • Respiratory masks put to the test

    More bad than right

    Fabric respirators are the most popular in South Asia. They are cheap, washable and can be bought anywhere in fashionable colors and patterns. However, the fabric only protects against coarse dust - fine dust particles can get into the lungs unhindered.

  • Respiratory masks put to the test


    Cone-shaped masks with a vent valve provide more protection. They filter around 60 percent of the diesel exhaust gases and up to 90 percent of the larger fine dust particles.

  • Respiratory masks put to the test

    Surprisingly effective

    To the surprise of scientists, the surgical face mask offers the best protection. This disposable medical mask filters up to 80 percent of both large and small particles from the air. This makes it almost as effective as higher quality masks.

  • Respiratory masks put to the test

    No escape

    The World Health Organization (WHO) estimates that more than three million people worldwide die each year as a result of high levels of air pollution. These include strokes, heart disease, lung cancer, and asthma.

  • Respiratory masks put to the test

    Air pollution in the pillory

    Hundreds of Nepalese demonstrated on World Environment Day last June to improve air quality in the capital, Kathmandu.

  • Respiratory masks put to the test

    A matter of courtesy

    The Japanese don't just wear respirators because of the fine dust. They want to protect themselves and others from viruses, especially in the flu season. Wearing a mask is good form there and has become a fashionable trend.

    Author: Marleen Heuer