Environmental air pollution is one of the most serious public health problems throughout the world. About 7 million people die prematurely every year as a result of air pollution. A vast array of studies have indicated a strong link between exposure to air pollution and human morbidity and mortality. Ambient air pollution caused 6% of total mortality, or more than 40,000 attributable cases, per year worldwide. Increased number of cars raises a new challenge; Trafficrelated Air Pollution (TRAP), which has been considered as the most important source of air pollution in urban areas. TRAP is a complex mixture of gases (including NO2 , SO2 , O3 ) and Particulate Matters (PMs) with different aerodynamic equivalent diameters, which could access the respiratory system easily via inhalation, and affect human health directly and indirectly. Exhaust fumes are extremely dangerous and can seriously injure and even kill people who are exposed. Recent epidemiological studies have shown that ambient air pollution exposure is associated with increased mortality and higher incidence of several diseases such as asthma, chronic obstructive pulmonary disease, neurologic disease, and cancer.