Differential effect of residual oil fly ash (ROFA), ambient particulate matter and diesel exhaust particle (DEP) on the human pulmonary alveolar epithelium

The physico-chemical composition of the particles was determined using transmission electron microscope and energy dispersive x-ray spectrometer (TEM/EDX) analysis. Primary human alveolar type 2 epithelial cells (AT2) and a transformed human alveolar type 1 (TT 1 ) epithelial cell line were exposed to ambient particles, ROFA, DEP and a ROFA/ DEP (1:1) mixture. Reactive oxygen species (ROS) production and cell viability were evaluated using the dichlorofluorescin (DCFDA) and 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium (MTI) assay respectively. Enzyme-linked immunosorbent assay (ELISA) was used to quantify release of CXCL8, IL-6, and CCL2. TEM/EDX results revealed that transition metals and other reactive elements were present in the samples. The result also showed that ambient PM has an amorphous structure which made particle size difficult to determine. The estimated average diameters of ROFA and DEP were 74 +17nm and 65 + 2nm respectively. When mixed, it was 76 + 24nm. Morphologically, these particles have large spherical, agglomerate and crystalline structures. Cellular exposures to PM were associated with significant increases in cytokine and chemokine release compared to non-treated controls (P< 0.002). At high concentrations (50 and 100f.tg/ml) the ROFA/DEP mixtures caused a significant increase in IL-6, CXCL8, and CCL2 release by TT-1 cells compared to exposure to an equivalent amount of DEP or ROFA alone (P