Greenpeace: poor air quality in 6 out of 10 Belgian schools

Greenpeace: poor air quality in 6 out of 10 Belgian schools

Greenpeace’s study “My air, my school” shows that air quality in too many primary schools is worrying or simply bad. Of the 222 Belgian schools that voluntarily took part in the study, barely seven schools recorded good air quality. In 76 schools, the air that children breathe is still acceptable, but in the remaining 143 schools surveyed, the air at the school gate is unhealthy for the children. This is also confirmed by Yuri Thijs of Greenpeace. Because of the higher emission of exhaust gases, the concentration of nitrogen dioxide is also 13 percent higher during school hours than the annual average values.



Between mid-November and mid-December 2017, a total of four weeks, all participating schools measured nitrogen dioxide in the air, each at three locations: at the school gate, on the playground and in the classroom. Tubes were hung in these three places, so-called “passive samplers”, a reliable measurement method that has already proven itself in practice in many countries. Nitrogen dioxide is an important indicator of air pollution, caused by diesel emissions in particular.

The 222 Belgian schools participated in the study on the basis of interest, without further selection. It therefore makes little sense to make comparisons between different regions or provinces on the basis of the measurement results.

Of the participating schools, 64 percent come from Flanders, 17 percent from Brussels and 19 percent from Wallonia. The report does not contain individual results from the schools, but each participating school did receive the measurement results and personalised recommendations.

The concentration of nitrogen dioxide is expressed in micrograms per cubic meter (μg/m³). The European limit value is 40 micrograms per cubic meter, but because epidemiological studies show that there are also effects on health at lower concentrations, and because this research concerns children, Greenpeace takes into account a maximum limit of 20 micrograms of nitrogen dioxide per cubic meter.


Annual average emissions NO2


“Children are more vulnerable and much more sensitive to the negative health effects of air pollution, because their bodies are still in full development,” says Joeri Thijs. “Because they are smaller, they also breathe relatively more unhealthy air than an adult person.”

“Children are particularly vulnerable to air pollution”

“Children who are more likely to be in an unhealthy environment are therefore more likely to suffer from asthma, allergies, lung infections and cancer, among other things. Air pollution in the classroom also leads to more learning and concentration problems”.


Only seven schools have good outdoor air quality

Because the European limit values for nitrogen dioxide are based on an annual average, the measurement results from November and December last year have also been converted into annual average values.

At 29 schools the concentration is between 30 μg/m3 and 40 μg/m3, which still means high exposure to poor air quality. Moderate air quality was measured at 101 schools, and acceptable air quality was measured at 76 schools. Only seven schools measured good outdoor air quality.

In more than half of the schools, the concentration on the playground is too high: between 20 μg/m3 and 40 μg/m3. These concentrations are too high for a playground, because children playing are more active and breathe more intensively.

The concentration of nitrogen dioxide in the classroom is often relatively low, even if the values at the school gate and on the playground are quite high. This has everything to do with the ventilation system.


More pollution during school hours

Annual average values are of course much less representative for different times of the day: at weekends and at night, the values of nitrogen dioxide in the school environment are much lower, because there is less traffic. But children are at school between 8.30 a.m. and 4 p.m.

Based on the annual average nitrogen dioxide concentrations of 68 official measuring stations, Greenpeace has calculated the concentration of nitrogen dioxide to which children are exposed during school hours. And what does it show? During school hours, the concentration is 13 percent higher.


Effect of the ventilation system

Some schools use a mechanical ventilation system, which means that ventilation is “forced”. Schools without such a mechanical ventilation system ventilate in a natural way, for example by opening windows or doors.

Greenpeace has found that the concentration of nitrogen dioxide in the classroom is higher with mechanical ventilation. This effect is most visible in schools in an urban environment, where the concentration of nitrogen dioxide in the outside air is already quite high. Due to the continuous renewal with the same polluted outside air, the concentration of nitrogen dioxide in the classroom increases, even if it is ventilated.

“The schools here face a dilemma,” says Yuri Thijs. “Because less ventilation does not always mean better air quality in the classroom. Ventilation in the classroom remains important to remove the carbon dioxide exhaled by the teacher and students. Excessively high CO2 levels can lead to loss of concentration.”


Rural vs Urban

Of the 222 schools surveyed, 119 are located in urban areas, and 103 in non-urban areas. The concentration of nitrogen dioxide in urban areas is significantly higher than in schools in rural areas.


The complete report of the study ‘My sky, my school’ and also the list of participating schools can be found on the Greenpeace website.


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