Air pollution is the largest environmental health risk for humans. It not only affects our lungs but also impacts the climate: pollutants exacerbate global warming. In the Netherlands, air quality has been improving in recent years, especially in cities. However, in many African cities, pollution is rapidly increasing. Twice a year, the KNMI, together with GLOBE Netherlands, organizes a measurement campaign for students to better understand satellite measurements of air pollution. This autumn, schools in Ghana will also participate for the first time.
On the International Day of Clean Air, September 7, the United Nations calls for increased attention to the global problem of air pollution. According to the World Health Organization (WHO), 6.5 million people die prematurely each year due to polluted air. Since pollutants remain in the air for a short time, we can almost immediately notice benefits for both human health and the climate if we reduce them.
Nitrogen Dioxide in Cities
NO2 is released during combustion processes, and traffic emits it directly where large groups of people live.
In cities, nitrogen dioxide (NO2), primarily from traffic, is a problem. NO2 is released during combustion processes, and motorized traffic emits it directly where large groups of people live and breathe. The major cities in the Netherlands currently meet the EU limit values for annual average concentrations. However, the values still exceed the tightened limit values that will be introduced in 2030 and the much stricter guideline that the WHO has set as a healthy upper limit since 2021 (see image 1).
In many African cities, the trend is moving in the opposite direction: urbanization and outdated vehicles are leading to a significant increase in pollution. The impact on health remains unknown because measurement equipment is expensive to purchase and maintain, resulting in few measurements being conducted.
Satellites Cannot Measure at Ground Level
The KNMI manages the Dutch TROPOMI instrument, which measures air pollutants from space worldwide. It is also closely involved with the recently launched Sentinel-4 and Sentinel-5 instruments. However, satellites cannot determine direct values at ground level. Therefore, local measurements are essential.
Students Hang Measurement Tubes in Various Locations
This provides valuable information on how satellite measurements can be translated into the amount of nitrogen dioxide at ground level.
Inexpensive NO2 measurement tubes offer a solution. Together with GLOBE Netherlands, the KNMI organizes a measurement campaign for students twice a year. Students place measurement tubes in various locations, and the results are analyzed in a laboratory. Because measurements are taken throughout the Netherlands, this provides valuable information on how satellite measurements can be translated into the amount of nitrogen dioxide at ground level.
Air Quality Laboratory in Ghana
Due to the low costs and simple materials, these measurement tubes are a good option for measurements in Africa. Earlier this year, the KNMI, together with the University of Kumasi, established an air quality laboratory in Ghana. Here, the tubes can be prepared and analyzed without relying on foreign laboratories. Since March 2025, measurements have been conducted at twenty locations in the city.
Join and Learn from Each Others Measurements
Ghanaian and Dutch students can also learn from each others measurements.
In October, Ghanaian schools will also participate in the GLOBE measurement campaign for the first time. This not only expands the measurement network but also allows Ghanaian and Dutch students to learn from each others measurements. It is not too late to join! Schools in the Netherlands can register via the GLOBE website.