The three variables, dose, dimensions and durability, have been shown from many studies to be the factors that combine to give the potential for a fibre to cause respiratory diseases. Regarding durability, a fibre that could show increased dissolution, possibly accompanied by chemical change, in physiological solutions would be expected to show reduced persistence in the lungs & have a lower potential for producing respiratory diseases. The development of such a fibre, Superwool X607, & the understanding that has been acquired in terms of solubility rate & other fibre properties is presented. The importance of in-vitro solubility rate studies to screen useful fibre compositions, combined with an understanding of how these can be selected using fee energy of hydration or non-bridging oxygen theories, is discussed in terms of developing new less "in-vivo" durable fibres.
