Fig. 7
Association of biological effects with metal content in size-fractionated particles. a Correlation of total metals (μg/g extracted particle) with potency according to metabolic function (assessed by impacts on resazurin reduction) after 24 h exposure of A549 and J774 cells. b Association of metal content with potency according to metallothionein-2 (MT-2) mRNA in J774 cells after 4 h exposure. Potency estimates were calculated as described in Materials and Methods. Open circles, ultrafine particles; filled circles, all other size fractions (PM0.1–0.5, PM0.5–2.5, PM2.5–10). The trend line and correlation coefficient exclude ultrafine particles (r = 0.69 for all particles)