ARTICLE NO. TX982484 Acute Respiratory Exposure of Human Volunteers to Octamethylcyclotetrasiloxane (D4): Absence of Immunological Effects

Humans are exposed to silicones in a number of commercial and consumer products. Some of these silicones, including octamethycy-clotetrasiloxane (D^), are volatile. Therefore, there is a potential for respiratory exposure. A phannacokinetic analysis of respiratory ex-posure to D4 is presented in the accompanying paper (M. J. Utell et aL, 1998, ToxicoL Set 44, 206-213). Possible immune effects of respiratory exposure to D4 are investigated in this paper. Normal volunteers were exposed to 10 ppm D4 or air for 1 h via a mouthpiece using a double-blind, crossover study design. Assays were chosen to screen for immunotoxicity or a systemic inflammatory response. As-sessment of immunotoxicity included enumeration of peripheral lym-phocyte subsets and functional assays using peripheral blood mono-nuclear cells. Because in humans there is no direct test for adjuvant effect of respiratory exposure, we analyzed proinflammatory cyto-kines and acute-phase reactants in peripheral blood, markers for