[Is it necessary to remove fibrous insulation material from buildings?]

Because of potential negative health effects of exposure to airborne fibres, removal of fibrous insulating materials from buildings, particularly asbestos, has become a frequent, in many cases unjustified, undertaking. The results are presented of the determination of airborne mineral respirable and non-respirable fibres, fragments and total airborne dust in a public building before the substitution of the insulating material, shortly after, and about two months later. There were no differences (P greater than 0.05) between the mean concentrations of respirable fibres (diameter less than or equal to 3 microns, length greater than or equal to 5 microns, aspect ratio greater than or equal to 3:1) measured before (0.0038 and 0.0031 f/cm3, resp.) and about two months after (0.0038 and 0.0028 f/cm3, resp.) the substitution, suggesting that the substitution was unnecessary. However, the concentrations measured two and eight days after the substitution were significantly elevated (P less than 0.05; P less than 0.01, resp.), indicating that the unnecessary disturbance of the insulating material caused an increase of exposure levels of the employees. It is concluded that the removal or substitution of fibrous insulating materials, solely on the basis of their presence in the buildings, is unjustified. The decision should be based on elevated concentrations of airborne fibres objectively quantified. Unnecessary substitution brings about an increase, not a decrease, of the concentrations through a shorter or longer period of time.