The composition of airborne particulate matter (PM) varies widely depending on its source, and recent studies have suggested that particle-associated adverse health effects are related to particle composition. The objective of this study was to compare the biological/toxicological effects of different source-related PM. Specifically, we investigated the biological/toxicological effects of standard reference materials (SRMs): non-ferrous dust (PD-1, industrial), urban PM (UPM, SRM1648a), and diesel PM (DPM, SRM2975), and ambient PM(2.5) (PM with an aerodynamic diameter <2.5 µm) collected at an urban site (Toronto, Canada). The dithiothreitol assay was used to measure the redox activity of the particles. Human alveolar epithelial cells (A549) were exposed to a range of concentrations (10-1000 µg/ml) of total PM, and the respective water-soluble and insoluble fractions, for 24 h. Biological responses were then evaluated in terms of cytotoxicity and interleukin (IL)-8 release, and compared with the PM composition and redox activity. We demonstrated that transition metal-enriched PD-1 exhibited the greatest cytotoxic effect (LD(50) values of 100-400 µg/ml vs. >1000 µg/ml for the SRM1648a, SRM2975, and ambient PM(2.5)). Similarly, the PM-induced release of IL-8 was greatest for PD-1 (~6-9 ng/ml vs. ~1.5-3 ng/ml for others). These endpoints were more responsive to metals as compared with compared with secondary inorganic ions and organic compounds. Interestingly, we demonstrated a high degree of adsorption of IL-8 to the various SRMs and ambient PM(2.5), and subsequently derived a new correction method to aid in interpretation of these data. These characteristics likely impart differential effects toward the toxic and immune effects of PM.