Chalk dust can cause cancer

Is chalk dust harmful?

Hardly any studies on the compatibility of chalk dust

This question affects many millions of teachers worldwide. And the number of potentially affected pupils is much larger - although the teachers are naturally more exposed because they often write something on the blackboard with chalk for a large part of the lesson time. But even though so many people are affected, there are comparatively few studies on exactly this question: Is inhalation of chalk dust a concern?

At least I found a few studies. One comes from India and first asked the simple question: How much chalk is there normally in the air? The typical situation is: you write something on the board. Most of the chalk stays on the blackboard. But some of it is ground up while writing and sooner or later falls to the ground. Before the dust falls to the ground, it floats in the air.

The researchers were able to show that the dust remains in the air long enough for the person standing directly at the blackboard to inhale some of it. Especially if he or she also has his or her mouth open while writing.

School chalk is made of plaster of paris

In the geological sense, “chalk” is not chalk like the one found on the chalk cliffs of Dover or Rügen - it consists of calcite, i.e. fine limestone. School chalk, on the other hand, consists primarily of plaster of paris. Gypsum is calcium sulfate - a material that is harmless to health. It is not toxic in the sense that it causes long-term damage. As a rule, one does not ingest such amounts that the lungs cannot cope with them. Unless it is already ailing, for example because you have a cold or the bronchi are inflamed.

Dust-free production using casein

In order to avoid that - and because the chalk dust is annoying anyway - the chalk manufacturers switched to producing chalk as dust-free as possible some time ago. To achieve this, however, another substance is often added to the chalk, namely casein. Casein is a milk protein.

A study has shown that this casein, in turn, could pose a problem for allergy sufferers. A study with schoolchildren of different ages came to the result: In children who have a milk allergy, inhaling chalk dust could cause allergic reactions, and in some cases even promote asthma. At least individual cases have been documented. However, the number of children examined is still too small to be able to say what role the chalk really played in this.

Beware of milk allergy

Nevertheless, one could derive the advice from this: If you have a milk allergy, you should perhaps avoid the dust as much as possible and not go extra close to the blackboard when writing.

In the meantime, more and more schools are switching from traditional blackboards to whiteboards - where the problem does not arise either.