People concerned about the risks of asbestos exposure are usually right to be worried. Asbestos is an incredibly deadly substance; major exposure to asbestos leads to diseases such as asbestosis, lung cancer, and mesothelioma, often with fatal effects. To make the asbestos exposure problem even worse, asbestos fibers are nearly indestructible. They do not dissolve in water; they do not burn up in a fire; they do not evaporate in sunlight or when exposed to chemicals.

It is not possible to completely avoid asbestos exposure. This is because asbestos is a naturally-occurring mineral product; it is part of the rocks that make up our planet, and as those rocks erode due to weather, fibers are released into the atmosphere. Asbestos fibers float in the air and water quite naturally, even without any human intervention or industrial development. It is estimated that a cubic meter of outdoor air (about what an adult would breathe in an hour) contains ten asbestos fibers. And – despite the deadliness of asbestos in general – this level of exposure does not present any significant health risk. (If it did, we would all be diagnosised with mesothelioma already.) The body can handle these tiny quantities of asbestos – it is the larger doses received in exposure to industrial processes or asbestos-containing products that cause disease.

Asbestos exposure has two main pathways:

The first pathway is inhalation – drawing the fibers into the lungs because the fibers are in the air.

The second pathway is ingestion, swallowing asbestos fibers that have contaminated food (rarely) or water (much more common). Asbestos fibers are not soluble in water, and so when asbestos washes into a water source by erosion from nearby rocks, runoff from mines, or asbestos-containing pipes or filters, the fibers can be absorbed by people who drink the water. Swallowed fibers are nearly always handled by the body quite well – the stomach and intestines expel the fibers with the other waste products of the body. However, a small number of fibers may penetrate the cells lining the intestine or the stomach, and some fibers may migrate into the bloodstream where they eventually become trapped in other tissues. Most medical authorities believe that swallowed asbestos may be a contributing factor in asbestos-related diseases like malignant mesothelioma, but that inhaled fibers are far, far more important in causing diseases.

Most asbestos-containing materials do not, in fact, shed asbestos fibers into the air. Asbestos insulation within the walls of a home or school, for example, are in all likelihood completely harmless – because the fibers are staying put, and not entering the atmosphere where they can be breathed in. Asbestos is like arsenic – it can’t hurt you if it isn’t entering your body. Where the danger comes in is when the asbestos materials are disturbed – when a fire or flood causes the binding material that the asbestos is part of to become exposed to the air, and the fibers become friable – meaning that they can be crumbled or reduced to powder easily. This is when asbestos-containing materials become deadly, and contribute to asbestos cancer.