Lime (calcium oxide) is produced through the heating of coral, limestone, chalk, or seashells. This process expels carbon dioxide gas, leaving lime as the main product. Sourcing out calcium oxide from limestone is among the oldest chemical processes done by man. It is also very valuable; almost half of its production is intended for use by the steel industry.
However, calcium oxide can be harmful when inhaled, irritating the lungs, causing shortness of breath and coughing. Contact can lead to eye and skin irritations or burns. Being exposed for a long time may result in nose irritation which can later result in porous bones, fragile nails and breaks in the skin.
The workers protect themselves with cloth over their faces soaked in water. That's it. The lime power clings to everything, the walls, the floor, the tools, their skin, hair, clothes and ultimately their lungs.