The indestructible nature of asbestos is exactly what creates a risk for humans.  When any invasive particles are inhaled and reach the lungs, the body's defenses attempt to trap and digest those particles.  Asbestos cannot be digested and cannot be broken down.  As such, the asbestos fibres simply remain in the lung indefinitely.  The body recognizes this and will continue to attack the fibres, forming scar tissue over time.  Asbestosis is a condition where the ability of the lung to operate is compromised by this scar tissue.  A number of forms of cancer have also been linked to asbestos exposure.  Symptoms of asbestos related illness manifest themselves over a very long period of time.  The time between exposure to asbestos and incidence of related disease can be as long as 30 years.  Every individual will be affected differently.

While the dangers of asbestos exposure should not be understated, it is important to understand that asbestos becomes a health risk to humans through inhalation or ingestion.  Asbestos is not toxic nor does it leach gas or any other effluent.  If asbestos is contained/encapsulated in such a way that risk of release of fibres into the air is eliminated, the hazard is also eliminated.