Solubility of Polymeric Organic Fibers and Manmade Vitreous Fibers in Gambles Solution

The solubility of fibers is thought to be an important determinant of their potential for inducing toxic and tumorigenic effects in the lung. Three manmade vitreous fiber (MMVF) compositions (borosilicates) and three polymeric organic fiber (POF) compositions (polypropylene, polyethylene, and polycarbonate) were compared for solubility in a physiological fluid, Gambles solution. The test materials were subjected to leaching for 180 days in a system that provided a continuous, constant flow of Gambles solution through sample holders containing the test fibers. During the 180 days, extraction fluids from the MMVFs only were collected for chemical characterization and all fibers, MMVF and POF were examined after 180 days for changes in surface area, total specimen weight, and surface characteristics (by electron microscopy). The MMVFs underwent significant but incongruent dissolution in Gambles solution. From plots of dissolved silica versus time, their silica solubility rates were determined to be much greater than that of chrysotile asbestos (used as a control for these studies) by from 650 to 17,000 times. The surface areas of the MMVFs increased by from 1800 to 22,000%, weight losses ranged from 37 to 75%, and significant visible fiber surface changes were observed on examination by SEM (scanning electron microscopy). On the other hand, the POFs studied showed virtually no dissolution in Gambles solution in this system with no significant changes in surface area, only slight weight gains ranging from 0.08 to 0.50%, and no visible fiber surface changes. These findings indicate that these POFs are more durable and therefore may persist longer in the lung than some MMVFs. Animal testing will be required to assess whether POFs are durable in the lung.