The critical role of dissolution on the potential health effects of inhaled fibres is well established . Over the last several decades there have been numerous publications on the relation between various physical characteristics of a synthetic vitreous fibre and its dissolution rate in physiological saline solution. These include the chemical composition of the fibre , fibre density changes as a result of annealing , fibre diameter , and the physical changes resulting from the fiberization method [3–5].
In addition to glass fibres, commercial insulation glass wool products typically contain an organic binder to give the strength and mechanical integrity required for their end use application. Although Bauer  notes that it is unlikely that fibres with thick binder coatings could reach the deep lung due to aerodynamic considerations, binder is typically found on some fibres during routine microscopic examination of airborne respirable fibres [unpublished observations, M. Kalinowski, Owens Corning Science and Technology Center]. It is therefore desirable to know if such binders provide any protection in the lung environment that would slow the dissolution rate of an otherwise biosoluble fibre.
Glass wool insulation binders, traditionally phenol-formaldehyde based resins, have received some previous study. Mattson  measured the dissolution rate in simulated lung fluid of a production glass wool with no applied binder, with phenol-formaldehyde binder, and with that binder removed by low temperature ashing. She found the dissolution rates for the three samples to be the same within the uncertainty of the measurements. Bauer  also found that phenol-formaldehyde binder has no effect on the dissolution rate. In addition, his microscopic examination of partially-dissolved samples showed that fluid attack of the resin-glass bond left the fibre surface exposed directly to the fluid early in the dissolution process. Similar experiments with coatings of silicone oil and a silane coupling agent alone, materials commonly used in commercial glass wool insulation binders, showed a similar delamination of the resin-glass interface but at a later point in the dissolution process. Although the silicone-silane coating caused an initial slowing of the dissolution, this did not last long enough to affect significantly the dissolution rate.
The studies just cited show that the phenol-formaldehyde binder traditionally used in commercial glass wool insulation has no effect on the dissolution of the glass fibres in physiological saline solution. In addition, these studies indicated that the absence of a protective effect was due, at least in part, to early attack of the glass-binder interface, which allows access of the fluid to the fibre surface even under thick binder droplets.
More recently, a number of new, formaldehyde-free binders, typically based on carbohydrate-polycarboxylic acid chemistry, have been developed and used in commercial insulation glass wool production. The present study addresses two questions about the effect of such new binders on the dissolution rate of wool insulation glass fibre in physiological saline solution: 1) does a visible layer of the binder affect the dissolution rate of the fibre underneath it and 2) does binder application influence the dissolution rate of fibre not visibly coated with it.