Particulate polycyclic aromatic hydrocarbons in urban air of Tehran
Epidemiological studies have shown correlations between the concentration of particles in the air and increase of daily rates of respiratory and cardiovascular diseases and mortality (Douglas et al.,1992; Jonathan et al.,1995; Auron et al.,1995). Elevated lung cancer rates among women in rural china have been attributed to emissions from their coal-fired stoves (Mumford et al.,1987;Alder and Fischer,1994). Studies of populations occupationally exposed to diesel emissions data suggest that there is an association between this exposure and lung cancer ( Roger,1987; Sharma and Patil, 1992a; Chow et al., 2001). The carcinogenic activity of diesel emissions has also been demonstrated in rats (BCMELP, 1993; CEPA.,1994). In the late, Whitby and coworkers synthesized numerous measurements at atmospheric particle size distributions to describe the distribution of particle sizes in atmospheric aerosols (Seinfeld ,1986). Atmospheric particles are grouped into ultrafine, fine and coarse size modes. Sources of Polycyclic aromatic hydrocarbons (PAHs) in the urban atmosphere of industrialized countries include automobiles, re-suspended soils, refineries and power plants (Roger et al., 1991; Venkataraman and Friedlinder, 1994). Tehran with population of more than 10 million has faced air pollution for a long time. Tehran occupies ~2300 km2 at an elevation of 1200 m above mean sea level. It is bordered on the north, northwest, east and southeast by high to medium height (4000-1000m) mountain ranges. As in many large cities with limited ventilation, Tehran experiences air pollution problems, especially suspended particles. Particle size has important health implications, with the smaller particles having a greater ability to penetrate deeper into the airways and lungs of a person who is breathing in these particles (Kiss et al.,1998; Sanderson et al., 2004). The composition and relative chemical load of differentsized particles is, therefore, clearly important in decreasing and determining risk.