Air Quality Wiki


Ozon – O3

Ozone is a colourless, toxic gas. At ground level, it is formed from nitrogen oxides and other volatile organic compounds by solar radiation, through photochemical processes.

  • Main sources: road traffic, combustion plants, solvents, agriculture
  • Health effects: damage to the lungs, intensification of asthma symptoms or other lung diseases, irritation of the respiratory tract
  • Affected risk groups: people with lung diseases, children, seniors, people active outdoors
  • Environmental impact: impaired plant growth, quality and quantity of agricultural products

Particulate Matter – PM10

PM10 summarizes all solid and liquid particles with different chemical compositions with a diameter smaller than 10 μm.

  • Main sources: road traffic, power plants, stoves / heaters in residential buildings, metal production, agriculture, soil erosion
  • Health effects: depending on the size, particles penetrate into the nasal cavity, bronchi or blood circulation and damage the tissue
  • Affected risk groups: people at increased risk of lung, heart / circulatory diseases or diabetes, children, seniors, people active outdoors

Particulate Matter – PM2.5

PM2.5 summarizes all solid and liquid particles with different chemical compositions with a diameter smaller than 2.5 μm.

  • Main sources: road traffic, power plants, stoves / heaters in residential buildings, metal production, agriculture, soil erosion
  • Health effects: depending on the size, particles penetrate into the nasal cavity, bronchi or blood circulation and damage the tissue
  • Affected risk groups: people at increased risk of lung, heart / circulatory diseases or diabetes, children, seniors, people active outdoors

Nitrogen Dioxide (NO2)

Nitric oxides are by-products of combustion processes. Under sunlight, they are instrumental in the formation of ground-level ozone and are also a source of fine dust.

  • Main sources: road transport, combustion plants, solvents, agriculture
  • Health effects: irritants and narrows the bronchi, intensifies lung diseases, increases the risk of diabetes and heart/circulatory diseases
  • Affected risk groups:  persons with lung disease or increased cardiovascular risk, children, seniors, outdoor active persons
  • Effects on the environment: Impaired plant growth, leading to overfertilization and acidification of soils and waters.

Air Quality and Health


What is Asthma?

Bronchial asthma, simplistically usually referred to as asthma, is a chronic lung disease in which the airways are chronically inflamed. At the same time, the airways are overly sensitive to various stimuli – this is referred to as bronchial hyperreactivity. This hyperexcitability of the airways leads to the constriction of the bronchial tubes in attacks, resulting in typical asthma symptoms.

What are typical asthma symptoms?

A characteristic feature of asthma is that symptoms occur in attacks, resolve, and then flare up again during the next attack. Asthma symptoms include:

  • whistling, hissing breathing (wheezing)
  • shortness of breath
  • chest tightness
  • cough

What happens in the body during asthma?

During normal breathing, the airways to the lungs are completely open. This allows air to flow freely in and out of the lungs. In asthma, the airways change in the following ways:

The airway branches leading to the lungs become overly reactive and more sensitive to all types of asthma triggers. The linings of the airways swell and become inflamed. Mucus clogs the airways.

The muscles around the airways contract (bronchospasm). The lungs have difficulty letting air in and out (airway obstruction: letting air out can be especially difficult). These changes narrow the airways. Breathing becomes difficult and strenuous, like trying to breathe through a straw filled with absorbent cotton.

How does air pollution contribute to the development of asthma?

The risk of developing asthma is higher the more the air at the place of residence is polluted with particulate matter from road traffic. This is particularly true for children, but also for adults. Particularly in urban centres, industrial areas and along traffic arteries, air polluted by fine dust is becoming an ever-increasing problem.

High levels of particulate matter and ozone in the air we breathe can cause asthmatics to develop symptoms of chronic obstructive pulmonary disease (COPD) in addition to asthma.

Why are asthmatics particularly at risk from air pollution?

Millions of people require emergency care each year because polluted air triggers an asthma attack – a problem that, by its very nature, is particularly common in major cities and basin locations. Up to 20 percent of emergencies are attributed to ozone irritating the airways. Fine particulate matter is responsible for up to nine percent, according to researchers, particularly ultrafine particles that penetrate the bronchial tubes and alveoli. A small percentage (0.4%) is due to nitrogen dioxide, which is produced by combustion and traffic. Overall, air pollution is responsible for 12 to 30 percent of asthma emergencies.

Ozone triggers asthma because it is highly irritating to the lungs and airways. It is well known that ozone levels are directly related to asthma attacks. It has also led to the need for more asthma medications and emergency treatment for asthma. Ozone can impair lung function and make it difficult to breathe deeply.

Other forms of air pollution can also trigger asthma. Small particles in the air can enter the lungs through the nose or mouth. Suspended particles found in haze, smoke, and airborne dust pose a serious air quality problem. People with asthma are at greater risk from breathing in small particles. The particles can exacerbate asthma. Both long-term and short-term exposure can lead to health problems such as decreased lung function and more asthma attacks.

Patients who already have asthma are also three times more likely to develop additional COPD if they are exposed to particulate matter and ozone over the long term.


What is COPD?

COPD is a progressive and yet incurable lung disease in which the airways become inflamed and persistently narrowed. The abbreviation COPD stands for “chronic obstructive pulmonary disease”, where “obstructive” stands for “narrowing”.

What are typical COPD symptoms?

Typical COPD symptoms are:

  • Cough with sputum
  • Shortness of breath

What happens in the body with COPD?

In COPD, the airways are inflamed and permanently narrowed (obstruction). Changes occur in the bronchi and lung tissue, either individually or in combination, and can worsen as the disease progresses:
The starting point is usually obstructive bronchitis: areas of the bronchi and bronchioles become inflamed due to inhaled pollutants. As a protective measure, the lungs secrete more mucus. The mucus is normally carried toward the exit (throat) by fine, mobile cilia that line most of the airways.
Pollutants such as nicotine destroy these fine hairs, causing them to lose their ability to cleanse and transport mucus. This leads to a thickening or destruction of the lung tissue (COPD with emphysema).

How does air pollution contribute to the development of COPD?

It is known that the main cause of the development of COPD is smoking – that is, breathing very polluted air containing fine dust. Smoking plays a role in 90% of those affected by COPD, although passive smoking can also be a triggering factor.
The role that ambient air pollution plays in the development of COPD is still under scientific investigation.

Why are COPD patients particularly at risk from air pollution?

Small and minute particles from household fires or road traffic in the ambient air and other air pollutants such as NO2 or ozone can contribute to air pollution that is problematic for health and thus also influence the course of COPD.
For example, there is a correlation between number of hospital outpatient visits for exacerbation of COPD and short-term increased air pollution from road traffic or in cities. This is also plausible because quite a few studies have shown that there is a relationship between air pollution and lung function.

Behavioural recommendations for risk groups in the event of increased air pollution

If exposure to air pollutants is high, strenuous outdoor activities should be avoided. In addition, staying in places with a lot of traffic should be avoided.

Living rooms should only be ventilated at times when there is little traffic. The use of a room air purifier is also advisable.

A healthy lifestyle (balanced diet, regular exercise, not smoking, low alcohol consumption at most, etc.) can also strengthen the body’s defences against oxidative stress and inflammation. This helps to counteract damage to health caused by negative environmental influences to a certain extent.

Summary of Selected Thresholds

Limits in Germany are strongly oriented towards the EU regulations. Switzerland, on the other hand, strives to comply with the WHO recommendations. Switzerland and Scotland have the strictest thresholds for air pollution. Brexit is unlikely to influence UK thresholds, since the UK limits are already strict. 

Ozon Thresholds

WHO: 100 µg/m3 (8h, daily maximum) 

EU: 120 µg/m3 (8-hour mean threshold not to be exceeded on more than 25 days averaged over 3 years) 

Germany: 120 µg/m³ O3 (highest 8-hour average of a day during a calendar year) 


Particulate Matter (PM10) Thresholds

WHO: 15 μg/m³ (annual mean) 

EU: 40 μg/m³ (annual mean) 

Germany: 40 μg/m³ (annual mean) 


Particulate Matter (PM2.5) Thresholds

WHO: 5 μg/m³ (annual mean) 

EU: 25 μg/m³ (annual mean) 

Germany: 25 μg/m³ (annual mean) 


Nitrogen Dioxide (NO2) Thresholds

WHO: 10 μg/m³ (annual mean) 

EU: 40 μg/m³ (annual mean) 

Germany: 40 μg/m³ (annual mean) 


Climate & Environment

Short-lived climate pollutants

Short-lived climate pollutants are powerful climate forcers that remain in the atmosphere for a much shorter period of time than carbon dioxide (CO2), yet their potential to warm the atmosphere can be many times greater. Certain short-lived climate pollutants are also dangerous air pollutants that have harmful effects for people, ecosystems and agricultural productivity.

The short-lived climate pollutants black carbon, methane, tropospheric ozone, and hydrofluorocarbons are the most important contributors to the man-made global greenhouse effect after carbon dioxide, responsible for up to 45% of current global warming.

More here

Tipping Points

A tipping point is when the familiar development of a system becomes so unbalanced that it takes on a new development and often cannot be restored to its former state.

Closely related to this is the term “tipping element“. In climate research, a tipping element refers to a part of the climate system whose interrelationships indicate the existence of a tipping point (in the broader sense).

With the help of various climate models, a number of regions have been identified so far where the local climate reacts very sensitively to interventions. Some of these tipping points could already be crossed in the course of the 21st century or have already been crossed.

Such a “tipping point” thus represents a risk where the damage is huge but the probability of occurrence is unknown. In view of the profound changes that each of these scenarios entails, it seems compelling that all these developments also influence each other and that the crossing of one tipping point could indirectly trigger the crossing of another. The complex interactions are unmanageable and by no means fully explored at present.


Climate Change

“Climate change” refers to the cooling or warming of the Earth’s climate over a long period of time. Not to be confused with weather – what we perceive every day in terms of short-term, current changes in temperature. Climate change is not a new phenomenon. It describes the long-term changes in factors such as temperature, precipitation and ocean currents.

Natural climate change is a process that develops over thousands of years.

Man-made climate change, on the other hand, takes place within a few generations.

Over the last 10,000 years, the temperature of our planet has been largely stable. This changed with the dawn of the industrial age about 260 years ago.

What is “climate”?

“Climate” refers to the average weather, including its extreme values, over a longer period of time at a specific location. “Climate” is therefore not directly measurable anywhere, but a statistic from many measurements. The area can be small or large, a city or a continent or the whole globe. The time period must be large enough for the formation of a statistical mean.

The reference period for determining the climate of the present is 30 years, e.g. the years 1961-1990. If the climate variables, i.e. temperature, precipitation, wind, evaporation, etc., fluctuate around a long-term mean value, the climate remains stable. If the mean value and the variability of the extremes change noticeably, a climate change is present. In contrast to the weather, the statistical mean values of the climate can theoretically be predicted over the longer term, especially for larger spaces such as continents or the globe

More here

What is „climate justice“?

“Climate justice” sees man-made climate change not only as a purely technical challenge and ecological problem but rather as a moral and political issue. The term deals with the current unequal distribution of causation, resources and the associated fight against the consequences of climate change, especially at the global level. The costs of combating and eliminating the consequences should be balanced according to the polluter pays principle. After all, the population groups that suffer the most from the consequences today are usually not the ones who initiated and intensified climate change in the past.

The aim is, therefore, not to distribute the costs equally at the global level but to link them to justice. This should be done by integrating social justice, equality, human rights and collective rights for climate change.

What is “environmental justice”?

The consequences of harmful environmental impacts caused by humans are not equally distributed even within a country or region. Socio-economic factors such as income and education play a significant role. Thus, lower income groups and marginalised groups are more likely to be affected by negative environmental impacts than those who are socially more advantaged.

Environmental justice deals with the equal treatment of all people with regard to their environment. Accordingly, all people should be able to enjoy the same healthy environment, regardless of origin, skin colour, income, or wealth.

What is “cumulative impact“?

Cumulative means accumulating or increasing. The cumulative effect thus describes a positive or negative impact, influenced by various factors that reinforce or cancel each other out. However, the factors considered separately may appear only marginal or even insignificant. In sum, however, they can have a major impact. Within environmental justice, “cumulative impact” has great significance.

An example: For a person living in an area with increased air pollution, the health burden increases, among other things, because he or she is exposed to unfavourable conditions at work and cannot afford to pursue compensatory activities or to pay attention to healthy nutrition in his or her free time.

Air Quality in Numbers

In 2021, 97% of cities and 100% of countries did not meet WHO PM2.5 air quality guidelines.

6,475 cities and 118 countries did not meet WHO PM2.5 air quality guidelines. Only 222 countries worldwide met WHO PM2.5 air quality guidelines. Read more here

Nearly 2 million children worldwide suffer from asthma caused by traffic-related air pollution.

The researchers studied nitrogen dioxide concentrations due to traffic. They tracked the development of new asthma cases in children. 1.85 million new asthma cases were caused by NO2.   Read more here

NO2 levels increased significantly by 30% during COP26.

NO2 levels in 01/22 within one mile of COP26 (Glasgow) increased by 30%, 93% above WHO limits. Read more here. 

22,000 data sets indicate a link between air/noise pollution and heart failure.

Researchers from the American Heart Association collected data from over 22,000 people. The analysis revealed evidence of an association with heart failure. It’s surprising how the two factors work together, the researchers said. Read more here.  

500,000 premature deaths annually in the European Region are attributable to air pollution

The WHO figure shows that 348 000 of these deaths in the Region occurred in low- and middle-income countries, and 208 000 deaths occurred in high-income countries. Of these, the majority are attributable to ambient air pollution.
Read more here


Risk of death from Alzheimer’s disease 35% higher with higher levels of PM2.5

Particulate matter (PM2.5) pollution is linked to a significantly increased risk of hospitalisation and death from Alzheimer’s disease, according to a new study by Duke University.

The researchers analysed North Carolina mortality and hospital admissions data for associations with levels of PM2.5. They identified 87 North Carolina postcodes where PM2.5 was above World Health Organisation (WHO) levels. Having adjusted for factors such as race, sex, income, education and health care access, the researchers found that the risk of death from Alzheimer’s disease was 35% higher in populations living in areas with higher levels of PM2.5.

Read more in Air Quality News


90% of the world suffers from harmful levels of air pollution

The average level of particulate matter (PM2.5) pollution in the largest cities in the world is 39 ug/m3, nearly 4 times higher than the World Health Organisation guideline of 10 ug/m3, according to analysis conducted by NGO OpenAQ.
Read more here