No longer asbestos
asbestos' fireproofing and insulating properties were first discovered by the ancient Greeks, but they knew nothing about the hazards associated with its use. When inhaled, asbestos fibres can cause asbestosis, a stiffening of lung tissue that contributes significantly to heart disease and lung cancer. Because of this risk, asbestos is being removed from schools, hospitals and thousands of other buildings around the us. It is an expensive, time-consuming and dangerous exercise, as workers in protective gear scrape out the substance, which must then be disposed of as a hazardous material. To prevent asbestos fibres from escaping into the air, areas being cleaned must be sealed-off in pressurised tents first.
Now a team of researchers from the Brookhaven National Laboratory at Long Island, usa, and the us-based W R Grace and Company have developed a novel way to tackle asbestos: change its chemical composition so that it no longer remains asbestos (Discover, Vol 19, No 5).
Chrysotile asbestos, the most common form of the mineral, is composed of oxygen, hydrogen, silica and magnesium atoms. The removal formula consists of a powerful acid combined with a fluoride ion that acts as a catalyst. "The two attack the silica layer, then the magnesium layer and remove the magnesium ion from the structure," says Leonidas Petrakis, principal investigator for the laboratory's team. This reaction breaks up asbestos' fibrous structure, leaving clumpy minerals that are not easily airborne.
Less than one per cent, a level deemed safe by the us epa, of the fibre remains after treatment, says Petrakis .
"What used to be asbestos has been converted into harmless chemicals like silica oxide and magnesium oxide," says Petrakis. "They continue to provide fireproofing for columns and beams at the equivalent of the fire rating the material when it contained asbestos."
The chemical is applied directly to asbestos-covered pipes or walls in a mix that has the consistency of a shaving cream. "The application is very gentle, so hardly any fibres are released," Petrakis says. A pressurised tent is not necessary. "That is a huge savings for people who want to use the process," he says.