Asthma and dust diseases
Some lung diseases are caused not by germs but by particles breathed in.
Asthma
Asthma is an allergy. The respiratory system reacts to small particles in the air — dust, pollen, wood dust, animal hair, smoke — the inside of the bronchi swells and narrows, and breathing in becomes hard, with a wheezing sound.
Silicosis
Workers in granite, stone quarries, sand and glass are exposed to dust containing silica. It settles in the alveoli and slowly destroys lung tissue.
Asbestosis
Breathing in dust containing asbestos particles and fibres. The fibres collect in the airways and destroy the tissue quickly.