Knowledge of how the chemical composition of a given ambient particle affects varied biological response upon inhalation is of considerable interest regarding the pathogenesis of respiratory and cardiovascular diseases. Characterization of initiating events, using measurements of proinflammatory mediator differential expression by lung tissues, is an objective of our studies. Results demonstrating the capability to monitor changes in the secreted proteome of a human lung cell line culture dosed with <150 particles, for incubation periods ranging from 30 min to 24 h using matrix assisted laser desorption ionization (MALDI) mass spectrometry, are presented. Each population of particles was created within an electrodynamic balance to have the same size and chemical composition prior to being deposited onto a culture of A549 cells. The carbon particles, and the lipopolysaccharide (52 pg/particle) containing carbon particles, were 6.3 microm in diameter. Numerous biomolecules are observable in the mass spectra of supernatants of lung cells. The relative abundance of many of these biomolecules changes as a function of particle type and incubation time, suggesting the ion signal intensities observed are indicative of the relative differential expression of these compounds, some of which could be proinflammatory mediators.