Asbestos

Asbestos (definition) presents remarkable properties:

• excellent behaviour against acid and basic attacks,
• good thermal, mechanical, acoustic behaviour
• good mechanical resistance.

Asbestos was therefore intensively used during the 20th century in the construction industry.

Harmfulness

Other side of the coin is that asbestos is harmful to health. The fibres of which it is made up, invisible with the naked eye, are propagated by the air. Inhaled in the lungs, they are likely to cause diseases such as lung cancer or pleura cancer (mesothelioma). These effects have only been highlighted gradually during the last 50 years, since the incubation time of such pathologies is very long.

On the medical level, contrary to lead, one does not know the exact threshold below which asbestos is inoffensive: one cannot exclude the hypothesis that only one asbestos fibre can provoke a cancer.

Among materials that are likely to contain asbestos (the nomenclature counts some more than 3000), all do not present nevertheless the same danger.

One distinguishes:

• friable materials (flockings, duct insulations, suspended ceilings...): they are the most harmful ones because they can emit fibres under the simple effect of air circulation, shocks or vibrations.
• non-friable materials: the asbestos fibres are trapped in a binder (cement, vinyl, painting, coated, cement, bituminizes...) and cannot spontaneously be released in the atmosphere.

This classification is to be balanced with the degree of degradation of the product. Indeed the presence of a product in bad state, friable or not, always implies a risk of asbestos fibre emission in the atmosphere.

Uses of asbestos in the construction industry

The great period of asbestos material use in France extends between the years 1950 and 1980. Then the asbestos containing products enjoy an excellent reputation : certain materials are praised to contain asbestos whereas they do not contain any, the artists paint on asbestos cement ...

At that time, flocking, the most harmful form of asbestos, is massively used as firebreak protection. It is obtained by projection of pure asbestos or in mixture on a support (ceiling, wall).

Among flocked buildings you can find professional buildings, schools, hospitals ...
The dwellings are in general spared by friable asbestos. However their construction or their restoration implements products containing non-friable asbestos, such as asbestos cement (pipe), menuiserite (plates) or vinyl-asbestos (floor tiles).

French legislation

Progressively with the awakening of the harmfulness of asbestos, the authorities promulgated increasingly strict laws aiming at protecting the inhabitants and the workers.
This evolution led in 1997 to the duty for the owners to order an asbestos inspection of their buildings. To this duty was added the one of removing asbestos in case the inspection reveals the presence of flockings, heat insulations or suspended ceilings that are degradated.

Let us note that the air mobility of asbestos fibres and their resistance (they are destroyed only by temperature > 2000°C) make it a major potential pollutant. That justifies the precautions taken at the time of the removal not to release fibres in the environment (containment with hopper of decontamination...). Without these measures, there would be risk to make more harm than good.