The membranolytic and cytotoxic properties of two naturally occurring (
chrysotile asbestos;
attapulgite clay) and two man-made (Fiberfrax, an
aluminium-
silicate, and
xonotlite, a
calcium silicate) industrial minerals were compared. "Short" fiber fractions of
chrysotile and Fiberfrax were obtained by sedimentation in demineralized water, while the
attapulgite and
xonotlite samples were used as obtained. The
aluminium silicate fibers were found to be non- hemolytic, while for the other three
silicates,
chrysotile had the strongest
hemolysis potential, followed very closely by
xonotlite;
attapulgite was less hemolytic than the former two
silicates, but was nevertheless highly hemolytic to the rat erythrocytes. Using rat pulmonary alveolar macrophages, the in vitro cytotoxicity assays showed that with fresh cell monolayers, all four
silicates were equivalent in causing cell damages at a dose of 250 micrograms; at a lower dose (50 micrograms), the intensity of the cytotoxic effect was in the decreasing order: Fiberfrax greater than
attapulgite greater than
chrysotile greater than
xonotlite. With one day-old cultured cell monolayers, a dose of 250 micrograms of the
silicates fibers was less cytotoxic, with the exception of the
attapulgite fibers which remained essentially as cytotoxic as with the fresh cell monolayers. The reduced cytotoxic response was especially noticeable with the
chrysotile fibers. At 50 micrograms, the cytotoxicity scale of the
mineral dusts with one day-old cell monolayers was essentially the same as the one obtained with the fresh cell monolayers, that is: Fiberfrax approximately equal to
attapulgite greater than
chrysotile greater than or equal to
xonotlite. Overall, these in vitro tests imply: 1) that all four industrial
silicates tested can be considered to be "biologically active"; 2) that on the basis of their different reactivities with the two types of cell culture conditions used, their
biological reactivity in vivo might be quite distinct. This might be especially true for at least the
chrysotile,
attapulgite and
xonotlite short fibers, considering that these three types of
silicate dusts have very similar dimensions. Moreover, for the
chrysotile and
attapulgite samples, fiber numbers is probably not an important factor, since the density of the two
silicates is roughly the same. The unaltered cytotoxic responses of the American
attapulgite fibers in the two macrophage assays correlate well with the fact that short
attapulgite fibers seems to have a stronger in vivo reactivity than short
chrysotile fibers. In fact, it might be the strongest of the four industrial
silicates tested.(ABSTRACT TRUNCATED AT 400 WORDS)