Urban air pollution has been one of the most important pollution problem for many decades. Airborne particulate 
matter (PM) from combustion sources is considered the most important air pollutants for adverse health effects to 
humans, especially for acute and chronic respiratory diseases and lung cancer. Airborne particles contain a number 
of toxic and carcinogenic substances as well as persistent free radicals entering the lung’s alveoli. PM in the lungs 
can generate free radicals and reactive oxygen species (ROS), initiating mechanisms of oxidative stress, inflammation 
and mutagenic damage to cellular DNA. These conditions lead progressively to increased morbidity and mortality as 
well as to increased risk of lung cancer. In the last decades a number of studies investigated PM size focusing to PM 
with aerodynamic diameter below l0 μm (ΡM10 
and ΡΜ2.5
), transition metals, polycyclic aromatic hydrocarbons (ΡΑΗ), 
stable quinoids αnd carcinogenic nitropyrenes. ROS generated by PM are linked to the pathogenesis of pulmonary 
oxidative damage, lipid peroxidation, damages to enzymes and cellular DNA. In our experimental study we investigated 
ROS generation by airborne PM (exhaust soot diesel and gasoline) by Electron Paramagnetic Resonance (EPR) and 
persistent free radicals characteristic to a mixture of semiquinone radicals. Also, we examined by EPR the formation of 
oxidative damage to guanosine nucleobase. by PM in aqueous phosphate buffer (pH 7.4) and the formation of the cancer 
biomarker 8-hydroxy-2’-deoxyguanosine.

Keywords: Airborne particulates; Particulate matter; Reactive oxygen species; Free radicals; Lung cancer; Carcinogenic 
mechanisms; Cancer biomarker.