IL-6 response of in vitro cell cultures treated with equal mass concentrations (53 μg/cm2) of nano- and micron-sized particles of the same nominal substance. A and B represent single experiments, N = 9. C and D are merged results from two independent experiments, N = 9 and N = 4 and have a broken scale to show the positive controls. A, C, : BEAS-2B cells in KGM media with 0.1% BSA; B, D. BEAS-2B cells in LHC-9 media with 0.1% BSA, IL-6 concentrations in pg/mL, mean ± s.d. *denotes statistically greater than control. Treatment codes are in Table 1.