Carbon in Intimate Contactwith Quartz Reduces theBiological Activity of Crystalline Silica Dusts.

To evaluate the effect of carbonaceous materials on thepathogenicactivity of quartz dusts, mixtures of carbon soot (1 and 10%) andquartz (Min-U-Sil) were prepared and then milled so to attain an intimateassociation of carbon and the quartz surface. Both cellular and cell-freetests show that carbon associated to quartz completely inhibits thetypical free radical generation of quartz dusts (through Fenton activityand homolytic cleavage of a C–H bond) and suppresses the oxidativestress and inflammation induced by quartz alone on MH-S murine macrophagecells (lipid peroxidation, nitric oxide release, and tumor necrosisfactor-α synthesis). The cytotoxic response to quartz is alsolargely reduced. An extremely pure quartz milled with 10% of sootshowed inactivating effects on the adverse reactions to quartz similarto Min-U-Sil quartz. None of these effects takes place when the sameexperiments are carried out with mechanically mixed samples, whichsuggests that carbon acts not just as a radical quencher but becauseof its association to the quartz surface. [ABSTRACT FROM AUTHOR]