Teachers often need to write and draw on the blackboard to explain. In a class of 45-50 minutes, we have to erase and write several times. When the class ends, a layer of white chalk dust is often left on hands, sleeves, and even hair and shoulders. Every day, year after year, after 20 to 30 years of work, tens of thousands of chalks are consumed. Inevitably inhaling some chalk dust from the nostrils. Whether inhalation of chalk ash causes disease is a matter of great concern to teachers. Chalk is made of plaster. The composition of gypsum is calcium sulfate. Gypsum is stable and non-toxic. For thousands of years, crude gypsum (calcium sulfate CaSO--4·2H2O containing crystal water) has been decoctioned in traditional Chinese medicine, and calcined gypsum (plaster of paris) is applied externally to the affected area. It is believed that it can cool down and relieve fever, promote body fluid and quench thirst, and promote muscle recovery.
To write on a blackboard with chalk, you apply gypsum powder to the blackboard. When wiping the blackboard, gypsum dust (chalk dust) briefly floats in the air and then falls on the surface and the ground near the blackboard. The particles are larger, more than 100 microns, heavier, fall faster, and float in the air for a short time. According to relevant labor hygiene data, dust particles in the air of production and living environments with a diameter of more than 10 to 20 microns are mostly blocked by the nose hair, nose, pharynx and throat when inhaled through the nostrils, and adhere to the small mucosal airways and alveoli. If the substances are harmful to the body (such as silicon dioxide, asbestos), they will accumulate in the alveoli and small airways, which will cause damage to the human body. It can be seen from the above that the particles of chalk dust are relatively large, and most of them will not be inhaled into the lower respiratory tract. In addition, gypsum itself is non-toxic to the human body. So far, there is no report of lung disease caused by inhalation of chalk dust in the medical field. China's labor and health department, in the relevant regulations of occupational pneumoconiosis, did not use chalk dust as the cause of lung disease.
Bár a krétapor nem káros az emberi szervezetre, Kínában tanárok milliói használnak krétát a táblára való íráshoz nap mint nap, és a tábla mindennapos letörlése után a krétaporban élnek, ami még mindig kellemetlen érzést okozhat az orrban, a garatban és a garatban. torok .
