Cong Liu

Lubricant oils emit strongly volatile organic compounds (VOCs) in industrial settings. The oil–gas interface concentration is a key parameter to drive the emission process. In this study, a dynamic headspace sampling method was proposed to characterize the interface concentration with the advantage of being simple and low cost. A critical sampling flow rate was theoretically derived as DA/L, where D (m²/s) is the diffusion coefficient of VOCs in the air, A (m²) is the surface area of the oil–gas interface, and L (m) is the height of the headspace. Experimental results prove that oil–gas equilibrium can be readily maintained by a sampling flow rate lower than the critical one. Four lubricant oils were characterized by the proposed method. The results indicate that the top five species accounted for 64–85% of the total VOC concentrations. Butylhydroxytoluene, an antioxidant additive, is the only compound among the top five species for all four lubricant oils. A V-shaped volatility distribution pattern was consistently observed. The vaporization enthalpies of VOCs for lubricant oils are smaller than those for pure substances, indicating weaker molecular interactions. The method offers a new powerful tool to characterize VOC pollution and consequently prioritize source control.

Although electronic cigarettes (e-cigarettes) are a substitute for traditional cigarettes, increasing studies indicate that e-cigarettes are unsafe. Here, we first analyzed the constituents of e-cigarette liquid (e-liquid) and e-liquid vaping-produced aerosols (e-aerosols) by gas chromatography quadrupole time-of-flight mass spectrometry (GC/Q-TOF MS) and inductively coupled plasma-MS (ICP-MS), and our result indicated that the components of e-aerosols differed from those of e-liquid. However, there is insufficient evidence on the toxicity of e-aerosols; therefore, an animal study was conducted accordingly. Mice were exposed to e-aerosols for 30, 60, or 90 days within a whole-body exposure chamber equipped with an air quality monitor. Compared with the control, weakened lung function and fiber deposition in murine lungs were observed following e-cigarette exposure. Microcomputed tomography (Micro-CT) images suggested fibrosis-like lesions in the lungs. Mechanistically, the expression of the core circadian rhythm gene, per1, was significantly inhibited by e-aerosols, which is negatively correlated with interleukin-6 (IL6) expression and resulted in continuous IL6⁺ macrophage infiltration in the lungs during both daytime and night. Eventually, the knockout of il6 expression could completely resist e-aerosol-induced pulmonary fibrosis in mice. Our results raise concerns regarding the role of circadian rhythm in regulating pulmonary fibrosis and the potential damages of e-cigarette consumption.

Fine particulate matter is a leading air pollutant, and its composition profile relates to sources and health effects. The human respiratory tract hosts a warmer and more humid microenvironment in contrast with peripheral environments. However, how the human respiratory tract impacts the transformation of the composition of environmental PM_2.5 once they are inhaled and consequently changes of source contribution and health effects are unknown. Here, we show that the respiratory tract can make these properties of PM_2.5 reaching the lung different from environmental PM_2.5. We found via an in vitro model that the warm and humid conditions drive the desorption of nitrate (about 60%) and ammonium (about 31%) out of PM_2.5 during the inhalation process and consequently make source contribution profiles for respiratory tract-deposited PM_2.5 different from that for environmental PM_2.5 as suggested in 11 Chinese cities and 12 US cities. We also observed that oxidative potential, one of the main health risk causes of PM_2.5, increases by 41% after PM_2.5 travels through the respiratory tract model. Our results reveal that PM_2.5 inhaled in the lung differs from environmental PM_2.5. This work provides a starting point for more health-oriented source apportionment, physiology-based health evaluation, and cost-effective control of PM_2.5 pollution.