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The 4 Most Dangerous Air Pollutants [2017]

Air quality is an enormous global health problem and causes millions of premature deaths every year. In 2012, there were around 3 million premature deaths because of outdoor air pollution and 4.3 million because of indoor air pollution.* In 2014, 92% of the world population was living in places where the WHO air quality guidelines levels were not met.*

There is still a long way to go until all of us can breathe fresh air, as everybody deserves. However, there are also some good news: in developed countries, air quality improves continuously.

In this blog episode, we would like to share our thoughts about the 4 most dangerous air pollutants [nowadays] in high income countries (2017). In addition, we give you insight of the huge air quality problem in low and middle income countries.

*World Health Organisation (WHO), 2017

Developed countries

There is clear evidence, that the air quality in the high-income countries is getting better and better. This is the result of many initiatives and regulations like the U.S. clean air act (1970), the UNECE convention CLRTAP (1979) and the WHO air quality guidelines (since 1987).

The graph below shows clear evidence that the yearly average values of several pollutants in Zurich go down****. The only upwards trend can be seen for ground level ozone (O3).

However, there are still issues with air pollutants in 2017. We will give you an overview of the 4 air pollutants which are still an issue nowadays:

  • Particulate Matter (PM2.5, PM10)

  • Ground Level Ozone (O3)

  • Nitrogen Dioxide (NO2)

  • Indoor Radon (Rn)

If you have a look into air quality reports of European and North American countries, these are the pollutants which regularly violate the maximum levels.

**** Bundesamt für Umwelt (BAFU), 2017


Particulate Matter (PM)

PM2.5 and PM10 are particles that can be carried deep into the lungs where they can cause inflammation and a worsening of the condition of people with heart and lung diseases. In addition, they may carry surface-absorbed carcinogenic compounds into the lungs. PM is mainly a problem during winter months. Particles from heating systems are the main source during cold month. Here an example of monthly averaged PM2.5 values of Indian cities over the years 2014 to 2016. []

Monthly averaged PM2.5 ov Indian cities. 2014-2016.

Ground Level Ozone (O3)

There is this saying about ozone (O3): "Good up high, bad nearby". What does that exactly mean?

  • Ozone in the upper atmosphere (stratosphere, 15-50km above earth surface) is good, because it protects us from the sun's harmful ultraviolet (UV) rays.

  • Ground level ozone in the lower atmosphere (troposphere, 0-15km) is bad, because it is harmful to breathe and it damages crops, trees and other vegetation.

Ozone is a colorless and odorless gas. It makes it difficult for us to breath, could cause coughing and even makes the lungs more susceptible to infections and worsens bronchitis, emphysema, and asthma.* Furthermore, ozone has a negative impact on vegetation and ecosystems, because it damages photosynthesis. Read more about this here.

Ozone is a secondary pollutant, that means it is not emitted directly into the air. Ozone is created by photochemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) when sunlight is present. This means that the only way to reduce ozone is to reduce the emission of NOx and VOCs from vehicles, industrial facilities, electric utilities and so on.

*World Health Organisation (WHO), 2017


Nitrogen Dioxide (NO2)

Nitrogen dioxide is a toxic, colorless and odorless gas.

NO2 could aggravate respiratory diseases, particularly asthma. Furthermore, NO2 along with other nitrogen oxides NOx react with other chemicals in the air to form Particulate Matter (PM2.5, PM10) and ozone (O3).***

NO and NO2 gets in the air from burning fuel (transport, heating, etc.). That the maximum permissible value for NO2 (dashed line in graph) is still not met in any case can be seen in the following graph (Switzerland, 1981-2014).****

NO2. 1981-2014. Switzerland.

*** Environmental Protection Agency (EPA), 2017

**** Bundesamt für Umwelt (BAFU), 2015


Indoor Radon (Rn)

You may have noticed, that this is the only indoor air pollutant on our list, all the others are outdoor pollutants.

Radon is a colorless and odorless radioactive gas which is sourced by the earths ground. It enters buildings through cracks and its concentration in air depends heavily where you live on the planet (e.g. if there is a higher uranium concentration in the ground). The Radon concentration in the basement and lower level floors is higher than above. Radon is on second place (after smoking) of the substances which causes lung cancer. It causes about 3–14% of all lung cancers in a country**.

When it comes to indoor air quality, you often hear the terms CO2 or Volatile Organic Compounds (VOCs). We do not want to lower their impact on your health, they clearly have. However, there are clear ways to overcome these pollutants (e.g. with ventilation or indoor plants).

We see Radon as the most dangerous indoor air pollutant in the western world nowadays. This is because of several reasons:

  1. Radon is the number one cause of lung cancer among non-smokers.***

  2. Radon is colorless and odorless. No human senses (eye, nose etc.) which would would help you detect a high Radon level in your home or workplace.

  3. The awareness of Radon as a health risk is not widely spread.

Radon exposure varies heavily from location to location. Therefore, national and international radon maps help to identify high and low risk radon areas. Have a look at the Radon map of your country and check Radon exposure is in your area:

UK for example has an interactive Radon map, which is pretty impressive.

UK Radon map. 2017.

** World Health Organisation (WHO), 2016

*** Environmental Protection Agency (EPA), 2017

Developing countries

Some 88% of all premature death caused by bad air quality, occurred in low- and middle-income countries.* This number makes clear, that air quality is a much bigger problem in these countries.

There are these two main factors which have to change in low-and middle-income countries.

  • Indoor air pollution: some 4.3 million premature deaths were attributable to household air pollution in 2012. The main cause is indoor smoke, which is a serious health risk for some 3 billion people who cook and heat their homes with biomass fuels and coal.*

  • Outdoor air pollution: ambient air pollution is a major environmental health problem affecting everyone in developed and developing countries alike.* However, the degree of pollution in fast-developing countries are often far higher than in developed countries. In general, air pollutants of concern in developing countries are the same as in the developed countries:

  • Particulate Matter (PM2.5, PM10)

  • Ground level ozone (O3)

  • Nitrogen dioxide (NO2)

  • Sulfur dioxide (SO2)

  • Carbon monoxide (CO)

* World Health Organisation (WHO), 2016


Developed countries

In developed countries, air quality improves constantly. The only exception is ground level ozone (O3), which is a major problem in summer. During winter, maximum permissible exposure limits of Particulate Matter (PM2.5, PM10) are regularly exceeded. Indoor Radon (Rn) is a so called "the silent killer". It is odorless and colorless.

Developing countries

It is necessary that homes in these countries get electrified. This would bring significant improvement to indoor air quality and would save millions of lifes. On the other hand, when it comes to outdoor air pollution: developing countries should learn from the high-income countries.

Personal Thoughts

Air quality depends heavily on the countries income. The higher the income, the more money is spent for a healthy environment and the better the air quality. Therefore, on a global perspective, people have to work together, increase wealth and prosperity. This will not only help increasing their own living standard, it also helps everybody living in a healthy and clean environment.

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Thank you!

#airquality #indoorairquality #IAQ #outdoorairquality #OAQ #Cellabox

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