Abstract
Abstract. A photo-electric aerosol sensor, a diffusion charger, an Aethalometer, and a continuous particle counter were used along with other real-time instruments to characterize the particle-bound polycyclic aromatic hydrocarbon (p-PAH) content, and the physical/chemical characteristics of aerosols collected a) in Wilmington (CA) near the Los Angeles port and close to 2 major freeways, and b) at a dynamometer testing facility in downtown Los Angeles (CA), where 3 diesel trucks were tested. In Wilmington, the p-PAH, surface area, particle number, and "black" carbon concentrations were 4-8 times higher at 09:00–11:00 a.m. than between 17:00 and 18:00 p.m., suggesting that during rush hour traffic people living in that area are exposed to a higher number of diesel combustion particles enriched in p-PAH coatings. Dynamometer tests revealed that the p-PAH emissions from the "baseline" truck (no catalytic converter) were up to 200 times higher than those from the 2 vehicles equipped with advanced emission control technologies, and increased when the truck was accelerating. In Wilmington, integrated filter samples were collected and analyzed to determine the concentrations of the most abundant p-PAHs. A correlation between the total p-PAH concentration (μg/m3) and the measured photo-electric aerosol sensor signal (fA) was also established. Estimated ambient p-PAH concentrations (Average=0.64 ng/m3; Standard deviation=0.46 ng/m3 were in good agreement with those reported in previous studies conducted in Los Angeles during a similar time period. Finally, we calculated the approximate theoretical lifetime (70 years per 24-h/day) lung-cancer risk in the Wilmington area due to inhalation of multi-component p-PAHs and "black" carbon. Our results indicate that the lung-cancer risk is highest during rush hour traffic and lowest in the afternoon, and that the genotoxic risk of the considered p-PAHs does not seem to contribute to a significant part of the total lung-cancer risk attributable to "black" carbon.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the urban atmosphere and are typically produced from incomplete combustion of fossil fuels and organic compounds, or from high temperature pyrolytic processes involving any materials containing carbon and hydrogen (Bostrom et al, 2002)
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The observed changes in the chemical and physical properties of particle-bound PAHs (p-PAHs) throughout the day suggest that the toxicity of fresh versus aged particles may differ
Summary
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the urban atmosphere and are typically produced from incomplete combustion of fossil fuels and organic compounds, or from high temperature pyrolytic processes involving any materials containing carbon and hydrogen (Bostrom et al, 2002). Atmospheric PAHs are found in the gas-phase (if characterized by high vapor pressures) and in the particulate phase (if their vapor pressures is relatively low), or can partition between the gas- and the particlephases (Naumova et al, 2003). Most PAHs, especially those with more than four aromatic rings, readily adsorb onto combustion aerosols (Harrison et al, 1996), and are predominantly associated with particles with an aerodynamic diameter smaller than 1–2 μm (Chetwittayachan et al, 2002). Fine and ultrafine particles (and, the PAHs bound to them) can penetrate deeply into the bronchial and pulmonary part of the human respiratory system, where their deposit and accumulation
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