ACUTE RESPIRATORY EXPOSURE OF HUMAN VOLUNTEERS TO OCTAMETHYLCYCLOTETRASILOXANE (D-4) - ABSENCE OF IMMUNOLOGICAL EFFECTS

Humans are exposed to silicones in a number of commercial and consumer products. Some of these silicones, including octamethycyclotetrasilox ane (D-4), are volatile. Therefore, there is a potential for respirato ry exposure. A pharmacokinetic analysis of respiratory exposure to D-4 is presented in the accompanying paper (M. J. Utell et al., 1998, Tox icol. Sci. 44, 206-213). Possible immune effects of respiratory exposu re to D-4 are investigated in this paper. Normal volunteers were expos ed to 10 ppm D-4 or air for 1 h via a mouthpiece using a double-blind, crossover study design. Assays were chosen to screen for immunotoxici ty or a systemic inflammatory response. Assessment of immunotoxicity i ncluded enumeration of peripheral lymphocyte subsets and functional as says using peripheral blood mononuclear cells. Because in humans there is no direct test for adjuvant effect of respiratory exposure, we ana lyzed proinflammatory cytokines and acute-phase reactants in periphera l blood, markers for a systemic inflammatory response, as surrogate ma rkers for adjuvancy. These tests were repeated when the volunteers wer e reexposed to D-4 approximately 3 months after this initial exposure. Blood was obtained prior to exposure, immediately postexposure, and 6 and 24 h postexposure. In these short-term, controlled human exposure s, no immunotoxic or proinflammatory effects of respiratory exposure t o D-4 were found. (C) 1998 Society of Toxicology..