Exhaust gas or flue gas is emitted as a result of thecombustion of fuels such as natural gas, gasoline(petrol), diesel fuel, fuel oil, biodiesel blends,or coal (Omidvarborna, 2014).According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack, or propelling nozzle. It often disperses downwind in a pattern called an exhaust plume.It is a major component of motor vehicle emissions (and from stationary internal combustion engines).
There is growing international concern regarding the adverse health effects of air pollution. Pollution is becoming an important public health problem and political issue, due to the rapid growth in world population and the increasing world-wide migration from rural to urban areas (Salvi et al., 1999). Recent United Nations estimates have indicated that 47% of the global population is living in urban areas. This urbanization has brought with it an increased need for transportation and hence an increase in motor vehicle generated air pollutants. However, a large number of epidemiological studies from different parts of the world have consistently identified an association between ambient levels of air particles and various health outcomes, including mortality, exacerbation of asthma, chronic bronchitis, respiratory tract infections, ischaemic heart disease and stroke (Salvi and Holgate, 1999). Indeed, the United Nations Environment Programme has identified particulate matter pollution as the most ser1Ous air pollution problem faced by many cities (Yoshino and Sagai, 1999). It is therefore important to evaluate the health effects of motor vehicle generated pollutants in mechanistic studies, in order to understand the relevance of associations found in the epidemiological studies. Parallel to the increase in air pollution, there has also been a rapid increase in the global incidence of allergic diseases such as asthma and rhinitis in the last twodecades, which cannot be attributed to genetic changes, and is assumed to be related to changes in environmental factors (Salvi et al., 2000). Observations in Japan have sug- gested that children living close to roads with heavy traffic are more likely to develop allergies (Norenhallet al., 2000).