asbestos

asbestos Many aspects of our physical environment pose risks to human health. Contrary to popular belief, asbestos is not, in general, one of them. Despite this fact, various parties continue to make money by exploiting public fears about this material. Furthermore, billions of dollars of state and federal funding continue to be spent to remove asbestos-containing materials from buildings, perhaps unnecessarily.‘Asbestos’ is a commercial, rather than mineralogical, term that encompasses six silicate minerals: chrysotile, amosite, fibrous anthophyllite, fibrous tremolite, fibrous actinolite, and crocidolite. All six minerals are referred to as ‘asbestos’ because they have ‘asbestiform habit’; that is, they form bundles of minute fibres. These fibres resist heat and are quite flexible, yet they are chemically and mechanically durable. Asbestos minerals are therefore employed as insulation and to make materials fire-retardant. Commonly, ceiling and floor tiles, pipe insulation, vehicle brake linings, cement, and mortar contain asbestos. The US government characterizes all six forms of asbestos as hazardous and requires its removal from public buildings.

Ninety-five per cent of all asbestos used commercially is chrysotile. This type of asbestos differs fundamentally from the other five kinds. Amosite, fibrous anthophyllite, fibrous tremolite, fibrous actinolite, and crocidolite are amphiboles, double-chain silicates, which observed microscopically look like sharp needles. Most experts agree that crocidolite, which comprises less than 5 per cent of asbestos used in industry, is the only type of asbestos which causes cancer. In particular, it is thought to cause mesothelioma, a cancer of the outer lining of the lung or the abdomen.

When materials that contain any type of asbestos are disturbed or damaged, the fibres can separate and become airborne. If people inhale the fibres, they can cause significant health problems. Asbestosis, first found in naval shipyard workers, is a lung disease caused when asbestos fibres become trapped in lung tissue. Acid produced by a body to destroy the fibres does little damage to the resistant asbestos fibres but scars the lungs, sometimes so severely that they cannot function. However, it seems that only high concentrations of fibres (more than 20 fibres per cubic centimetre of air) inhaled for many years cause this disease. In addition, only the presence of crocidolite among the fibres will cause lung cancer to develop.

This raises the question, should we remove from public buildings asbestos that is in good condition, isolated from the air, and therefore not inhalable?

Individuals who are exposed regularly to high concentrations of asbestos, such as mine, factory, and construction workers, must certainly be protected against the potential health hazards of their work. However, since chrysotile does not cause cancer, and since undisturbed asbestos in good condition cannot be inhaled, the benefits of having all asbestos removed from public buildings are dubious. A number of studies even show that ingestion of asbestos particles that settle in water or on food is not dangerous and that skin contact with asbestos poses no threat to health.

It seems that the health risks associated with minimal exposure to asbestos are tiny. The calculated risk for cancer resulting from smoking is 1 in 5, as compared to that for asbestos-related lung disease, which is 1 in 100 000. The most sensible course for dealing with asbestos in public spaces will include evaluation of the condition and type of asbestos present.

Jill S. Schneiderman