Road tunnel-derived coarse, fine and ultrafine particulate matter: physical and chemical characterization and pro-inflammatory responses in human bronchial epithelial cells

Abstract

Background Traffic particulate matter (PM) comprises a mixture of particles from fuel combustion and wear of road pavement, tires and brakes. In countries with low winter temperatures the relative contribution of mineral-rich PM from road abrasion may be especially high due to use of studded tires during winter season. The aim of the present study was to sample and characterize size-fractioned PM from two road tunnels paved with different stone materials in the asphalt, and to compare the pro-inflammatory potential of these fractions in human bronchial epithelial cells (HBEC3-KT) in relation to physicochemical characteristics. Methods The road tunnel PM was collected with a vacuum pump and a high-volume cascade impactor sampler. PM was sampled during winter, both during humid and dry road surface conditions, and before and after cleaning the tunnels. Samples were analysed for hydrodynamic size distribution, content of elemental carbon (EC), organic carbon (OC) and endotoxin, and the capacity for acellular generation of reactive oxygen species. Cytotoxicity and pro-inflammatory responses were assessed in HBEC3-KT cells after exposure to coarse (2.5–10 μm), fine (0.18–2.5 μm) and ultrafine PM (≤ 0.18 μm), as well as particles from the respective stone materials used in the pavement. Results The pro-inflammatory potency of the PM samples varied between road tunnels and size fractions, but showed more marked responses than for the stone materials used in asphalt of the respective tunnels. In particular, fine samples showed significant increases as low as 25 µg/mL (2.6 µg/cm2) and were more potent than coarse samples, while ultrafine samples showed more variable responses between tunnels, sampling conditions and endpoints. The most marked responses were observed for fine PM sampled during humid road surface conditions. Linear correlation analysis showed that particle-induced cytokine responses were correlated to OC levels, while no correlations were observed for other PM characteristics. Conclusions The pro-inflammatory potential of fine road tunnel PM sampled during winter season was high compared to coarse PM. The differences between the PM-induced cytokine responses were not related to stone materials in the asphalt. However, the ratio of OC to total PM mass was associated with the pro-inflammatory potential.

Ambient Nanoparticles (PM0.1) Mapping in Thailand

“…PMs can be categorized into three modes, which include coarse particles (diameter between 2.5 and 10 µm), fine particles (with a diameter between 0.1 to 2.5 µm), and ultrafine particles (diameters ≤ 0.1 µm or 100 nm) [4,5]. The coarse category is primarily generated from attrition processes, namely, mechanical abrasion, the re-suspension of road and soil dust, volcanic eruptions, and sea spray [6]. On the other hand, fine and ultrafine mode particles evolve mainly from combustion processes, e.g., biomass burning, motor vehicle exhaust, coal combustion, and chemical processes in the atmosphere [7,8].…”

Lung cancer associated with combustion particles and fine particulate matter (PM2.5) - The roles of polycyclic aromatic hydrocarbons (PAHs) and the aryl hydrocarbon receptor (AhR)

“…Nevertheless, traffic emissions remain a major source of increased urban air PAH levels. Recent studies of road tunnels PM suggested that PAHs on traffic PM 2.5 were primarily attached to aggregates of ultrafine PM originating from the combustion of transportation fuel [ 53 , 54 ]. More US EPA PAHs have been found in the ultrafine and fine PM (PM 2.5 ) samples than in the coarse PM, which to a large degree seem to originate from non-combustion sources such as bitumen and tires [ 54 ].…”

Role of different mechanisms in pro-inflammatory responses triggered by traffic-derived particulate matter in human bronchiolar epithelial cells

“…Epidemiological studies indicate that short-term exposure to both coarse and fine PM is associated with respiratory hospital admissions and mortality [ 17 , 18 ]. Furthermore, some animal studies [ 19 ] and in vitro experiments have reported higher pro-inflammatory responses of coarse than fine PM [ 19 – 26 ], whereas other animal studies [ 27 , 28 ] and in vitro studies [ 29 – 31 ] show similar or higher responses for the fine than coarse PM. The relative impact of coarse versus fine and ultrafine PM depends on their specific sources, but also on the model system and health outcome examined.…”

“…We have previously demonstrated that particles derived from different stone (rock) aggregates used in road pavement may induce inflammatory responses of different magnitude [ 11 , 38 – 40 ], suggesting that the choice of stone type may be of importance for adverse respiratory effects induced by traffic-related PM. In our recent study, particles of different sizes were sampled inside two road tunnels paved with different stone materials [ 29 ]. The results showed that fine PM (PM 2.5-0.18 ) induced higher pro-inflammatory responses in human bronchial epithelial cells (HBEC3-KT cells) than coarse PM (PM 10-2.5 ), whereas the potency of the ultrafine PM (< PM 0.18 ) was more variable.…”