TD, produced by tire wear, is a significant constituent of PM(10) in urban areas where traffic related emissions are predominant. TD contains a lot of chemicals which can affect human respiratory system and it has received little attention until now, even the toxicity of PM has been extensively documented. A549 cells, a human alveolar lung cells, were exposed for 24, 48, 72 h to 10, 50, 60, 75 microg/ml of TD organic extract. MTT and Trypan Blue assays were used to evaluate cytotoxicity and Comet Assay to evidence DNA damage. TD extracts induced a dose-dependent increase in cell mortality and DNA damage. A significant toxicity was observed when cells were exposed to 60 microg/ml for 72 h. Moreover cell morphology observed at ultra structural level, was severely affected at the highest dose.