Air pollutants are usually classified into gaseous pollutants and suspended particulate matter. Airborne particles represent a complex mixture of organic and inorganic substances. With respect to mass and composition these pollutants are divided into 2 principle groups: coarse particles larger than 2.5 µ m (up to 10 µ m; PM 10 ) in aerodynamic diameter, and fine particles smaller than 2.5 µ m (PM 2.5 ). The health effects of suspended particulate matter in humans depend on particle size and concentration, and can fluctuate with daily fluctuations in PM 10 or PM 2.5 levels. Chronic health effects include long-term decrements in lung growth, chronic obstructive lung disease, neurobehavioural alterations, heart disease, congenital defects, and cancer. Acute health effects encompass outcomes, such as aggravation of the existing disease, acute respiratory infections, transient deficits in lung function, and allergic reactions. Therefore, it is important to determine levels and composition of ambient genotoxicants and to detect early biological effects in exposed populations.