What are the lungs? The lungs are the organs of breathing: they are responsible for bringing oxygen from the atmosphere into the body through a series of branching air tubes (Figure 1) and exchanging it for carbon dioxide that is released back into the atmosphere.

The lungs are constantly exposed to danger from the dusts we breathe. Luckily, the lungs have another function - they have defence mechanisms that protect them by removing dust particles from the respiratory system. For example, during a lifetime, a coal miner may inhale 1,000 grams of dust into their lungs. When doctors examine the lungs of a miner after death, they find no more than 40 grams of dust. Such a relatively small residue illustrates the importance of the lungs’ defences and certainly suggests that they are quite effective. On the other hand, even though the lungs can clear themselves, excessive inhalation of dust may result in disease.

Dusts are tiny solid particles scattered or suspended in the air. The particles are “inorganic” or “organic,” depending on the source of the dust. Inorganic dusts can come from grinding metals or minerals such as rock or soil. Examples of inorganic dusts are silica, asbestos, and coal.

Organic dusts originate from plants or animals. An example of organic dust is dust that arises from handling grain. These dusts can contain a great number of substances. Aside from the vegetable or animal component, organic dusts may also contain fungi or microbes and the toxic substances given off by microbes. For example, histoplasmosis, psittacosis and Q Fever are diseases that people can get if they breathe in organic that are infected with a certain microorganisms.

Dusts can also come from organic chemicals (e.g., dyes, pesticides). However, in this OSH Answers document, we are only considering dust particles that cause fibrosis or allergic reactions in the lungs. We are not including chemical dusts that cause other acute toxic effects, nor long term effects such as cancer for example.