Real-time monitoring of respiratory absorption factors of volatile organic compounds in ambient air by proton transfer reaction time-of-flight mass spectrometry

Ultra-sensitive analysis of exhaled biomarkers in ozone-exposed mice via PAI-TOFMS assisted with machine learning algorithms

Ground-level ozone ranks sixth among common air pollutants. It worsens lung diseases like asthma, emphysema, and chronic bronchitis. Despite recent attention from researchers, the link between exhaled breath and ozone-induced injury remains poorly understood. This study aimed to identify novel exhaled biomarkers in ozone-exposed mice using ultra-sensitive photoinduced associative ionization time-of-flight mass spectrometry and machine learning. Distinct ion peaks for acetonitrile (m/z 42, 60, and 78), butyronitrile (m/z 70, 88, and 106), and hydrogen sulfide (m/z 35) were detected. Integration of tissue characteristics, oxidative stress-related mRNA expression, and exhaled breath condensate free-radical analysis enabled a comprehensive exploration of the relationship between ozone-induced biological responses and potential biomarkers. Under similar exposure levels, C57BL/6 mice exhibited pulmonary injury characterized by significant inflammation, oxidative stress, and cardiac damage. Notably, C57BL/6 mice showed free radical signals, indicating a distinct susceptibility profile. Immunodeficient non-obese diabetic Prkdc-/-/Il2rg-/- (NPI) mice exhibited minimal biological responses to pulmonary injury, with little impact on the heart. These findings suggest a divergence in ozone-induced damage pathways in the two mouse types, leading to alterations in exhaled biomarkers. Integrating biomarker discovery with comprehensive biopathological analysis forms a robust foundation for targeted interventions to manage health risks posed by ozone exposure.

A literature survey of all volatiles from healthy human breath and bodily fluids: the human volatilome

This paper comprises an updated version of the 2014 review which reported 1846 volatile organic compounds (VOCs) identified from healthy humans. In total over 900 additional VOCs have been reported since the 2014 review and the VOCs from semen have been added. The numbers of VOCs found in breath and the other bodily fluids are: blood 379, breath 1488, faeces 443, milk 290, saliva 549, semen 196, skin 623 and urine 444. Compounds were assigned CAS registry numbers and named according to a common convention where possible. The compounds have been included in a single table with the source reference(s) for each VOC, an update on our 2014 paper. VOCs have also been grouped into tables according to their chemical class or functionality to permit easy comparison. Careful use of the database is needed, as a number of the identified VOCs only have level 2-putative assignment, and only a small fraction of the reported VOCs have been validated by standards. Some clear differences are observed, for instance, a lack of esters in urine with a high number in faeces and breath. However, the lack of compounds from matrices such a semen and milk compared to breath for example could be due to the techniques used or reflect the intensity of effort e.g. there are few publications on VOCs from milk and semen compared to a large number for breath. The large number of volatiles reported from skin is partly due to the methodologies used, e.g. by collecting skin sebum (with dissolved VOCs and semi VOCs) onto glass beads or cotton pads and then heating to a high temperature to desorb VOCs. All compounds have been included as reported (unless there was a clear discrepancy between name and chemical structure), but there may be some mistaken assignations arising from the original publications, particularly for isomers. It is the authors' intention that this work will not only be a useful database of VOCs listed in the literature but will stimulate further study of VOCs from healthy individuals; for example more work is required to confirm the identification of these VOCs adhering to the principles outlined in the metabolomics standards initiative. Establishing a list of volatiles emanating from healthy individuals and increased understanding of VOC metabolic pathways is an important step for differentiating between diseases using VOCs.

Key Role of NO3 Radicals in the Production of Isoprene Nitrates and Nitrooxyorganosulfates in Beijing

The formation of isoprene nitrates (IsN) can lead to significant secondary organic aerosol (SOA) production and they can act as reservoirs of atmospheric nitrogen oxides. In this work, we estimate the rate of production of IsN from the reactions of isoprene with OH and NO₃ radicals during the summertime in Beijing. While OH dominates the loss of isoprene during the day, NO₃ plays an increasingly important role in the production of IsN from the early afternoon onwards. Unusually low NO concentrations during the afternoon resulted in NO₃ mixing ratios of ca. 2 pptv at approximately 15:00, which we estimate to account for around a third of the total IsN production in the gas phase. Heterogeneous uptake of IsN produces nitrooxyorganosulfates (NOS). Two mono-nitrated NOS were correlated with particulate sulfate concentrations and appear to be formed from sequential NO₃ and OH oxidation. Di- and tri-nitrated isoprene-related NOS, formed from multiple NO₃ oxidation steps, peaked during the night. This work highlights that NO₃ chemistry can play a key role in driving biogenic-anthropogenic interactive chemistry in Beijing with respect to the formation of IsN during both the day and night.

Vertical profiles of biogenic volatile organic compounds as observed online at a tower in Beijing

Vertical profiles of isoprene and monoterpenes were measured by a proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) at heights of 3, 15, 32, 64, and 102 m above the ground on the Institute of Atmospheric Physics (IAP) tower in central Beijing during the winter of 2016 and the summer of 2017. Isoprene mixing ratios were larger in summer due to much stronger local emissions whereas monoterpenes were lower in summer due largely to their consumption by much higher levels of ozone. Isoprene mixing ratios were the highest at the 32 m in summer (1.64 ± 0.66 ppbV) and at 15 m in winter (1.41 ± 0.64 ppbV) with decreasing concentrations to the ground and to the 102 m, indicating emission from the tree canopy of the surrounding parks. Monoterpene mixing ratios were the highest at the 3 m height in both the winter (0.71 ± 0.42 ppbV) and summer (0.16 ± 0.10 ppbV) with a gradual decreasing trend to 102 m, indicting an emission from near the ground level. The lowest isoprene and monoterpene mixing ratios all occurred at 102 m, which were 0.71 ± 0.42 ppbV (winter) and 1.35 ± 0.51 ppbV (summer) for isoprene, and 0.42 ± 0.22 ppbV (winter) and 0.07 ± 0.06 ppbV (summer) for monoterpenes. Isoprene in the summer and monoterpenes in the winter, as observed at the five heights, showed significant mutual correlations. In the winter monoterpenes were positively correlated with combustion tracers CO and acetonitrile at 3 m, suggesting possible anthropogenic sources.

The exposure risk of typical VOCs to the human beings via inhalation based on the respiratory deposition rates by proton transfer reaction-time of flight-mass spectrometer

The respiratory deposition rates are the important analytical parameters for human health risk assessment related to the environmental volatile organic compounds (VOCs). In present study, the deposition rates from the linear regressions of CH₂O, CH₅N, C₂H₆O, C₂H₄O₂, C₃H₈O, C₆H₆, C₇H₈, C₈H₈, and C₈H₁₀ of 120 healthy volunteers were obtained with significantly different from the respective calculated deposition rates. The CH₂O (formaldehyde) has the highest deposition rate, indicating the highest associated exposure risk of CH₂O if the persons are exposed to the same concentrations of these VOCs through inhalation. In order to explore the effects of the breathing models and sampling time on the deposition rates of VOCs, volunteers were first asked to breathe successively with nasal-in-nasal-out, oral-in-nasal-out, and oral-in-oral-out breathing models before and after three meals for three days. Sampling time variation has no effect on the deposition rates of selected VOCs, while the deposition rates of C₂H₄O₂, C₃H₈O, C₆H₆, C₇H₈ and C₈H₁₀ by nasal-in-nasal-out were significantly different from oral-in-oral-out and nasal-in-oral-out models. Among all the breathing models, nasal-in-oral-out comprises the entire respiratory system. In order to further validate the results, the deposition rates of the selected VOCs were calculated in 120 healthy volunteers using nasal-in-oral-out breathing model for unlimited time after the conventional lung function examination. Difference in gender and body mass index had no effect on the deposition rates of VOCs, while the age affects the deposition rates of CH₂O, CH₅N and C₂H₄O₂. Positive correlation analysis between lung function factors and deposition rates revealed that the individuals with larger lung function factors are more susceptible to deposit the VOCs. Overall, the main conclusion can be drawn that the respiratory deposition rates were influenced by the physiological factors. Therefore, the major objective for future research is to accurately calculate the deposition rates of environmental VOCs for health-risk assessment.

Biogenic volatile organic compound emissions from Pinus massoniana and Schima superba seedlings: Their responses to foliar and soil application of nitrogen

Increasing nitrogen (N) deposition is one of the main drivers of global change, while the emission of biogenic volatile organic compounds (BVOCs) from plant in response to elevated N deposition is poorly understood, especially with respect to the response to foliar application of N. In this study, BVOC emissions from two tree species (Pinus massoniana Lamb. and Schima superba Gardn. et Champ.) were determined by dynamic chamber coupled with a proton transfer reaction-time of flight-mass spectrometer. Two N application methods, namely soil application of N (SAN) and foliar application of N (FAN), and three N levels (5.6, 15.6 and 20.6 g N m^-2 yr^-1) were employed by applying NH₄NO₃ every week for 1.5 years. The results showed that: (1) oxygenated volatile organic compounds (OVOCs, mainly acetaldehyde, methyl alcohol, ethenone and acetone) and non-methane hydrocarbons (NMHCs, mainly monoterpenes, propyne, 1,3-butadiene and propylene) were the dominant BVOCs for all the treatments, accounting for 32.40-65.72% and 19.21-47.39% of total 100 determined BVOC compounds, respectively; (2) for S. superba seedlings, both SAN and FAN treatments significantly decreased total BVOC emissions (11.83% to 66.23%). However, total BVOCs from P. massoniana significantly increased with N addition for SAN treatment, while no difference were found in the FAN treatment; (3) BVOC emission rates for FAN treatment were significantly lower than those for SAN treatment, indicating that previous studies which simulated N deposition by adding N directly to soil might have imprecisely estimated their effects on plant BVOC emissions. Considering the inconsistent responses of BVOC emissions to different N application methods for different plant species, close attention should be paid on the effects of N deposition or even global change on plant BVOC emissions in the future.

Primary emissions and secondary organic aerosol formation from in-use diesel vehicle exhaust: Comparison between idling and cruise mode

Diesel vehicle exhaust is an important source of carbonaceous aerosols, especially in developing countries, like China. Driving condition impacts diesel vehicle emissions, yet its influence needs further understanding especially on secondary organic aerosol (SOA) formation. In this study tailpipe exhaust from an in-use light duty diesel vehicle at idling and driving speeds of 20 and 40 km h^-1 was introduced respectively into a 30 m^-3 indoor smog chamber to investigate primary emissions and SOA formation during photo-oxidation. The emission factors of SO₂ at 20 and 40 km h^-1 were higher than those at idling, whereas the emission factors of aromatic hydrocarbons (AHs), polycyclic aromatic hydrocarbons (PAHs) and oxygenated volatile organic compounds (OVOCs) decreased when driving speeds increased. The emission factors of black carbon (BC) and primary organic aerosol (POA) at idling were comparable to those at 20 and 40 km h^-1. The SOA production factors were 0.41 ± 0.09 g kg-fuel^-1 at idling, approximately 2.5 times as high as those at 20 km h^-1 (0.16 ± 0.09 g kg-fuel^-1) or 40 km h^-1 (0.17 ± 0.09 g kg-fuel^-1). Total carbonaceous aerosols, including BC, POA and SOA, from diesel vehicles at 20 and 40 km h^-1 were 60-75% of those at idling, due largely to a reduction in SOA production. Measured AHs and PAHs altogether were estimated to explain <10% of SOA production, and eight major OVOCs could contribute 8.4-23% of SOA production. A preliminary comparison was further made for the same diesel vehicle at idling using diesel oils upgraded from China 3 to China 5 standard. The emission factors of total particle numbers decreased by 38% owing to less nuclei mode particles, which was probably caused by the reducing fuel sulfur content; the emission factors of BC were almost unchanged, the POA emission factors and SOA production factors however decreased by 72% and 37%.

Experimental study of destruction of acetone in exhaust gas using microwave-induced metal discharge

Volatile organic compounds (VOCs) are air pollutants that pose a major concern, and novel treatment technologies must be continuously explored and developed. In this study, microwave-induced metal discharge was applied to investigate the destruction of acetone as a representative model VOC compound. Results revealed that metal discharge intensity largely depended on microwave output power and the number of metal strips. Microwave metal discharge exerted the distinct combined effects of intense heat, strong light, and plasma. In the case of MW without metal discharge, the decrease in acetone at 200 ppm was remarkably limited (approximately 5.5% (mol/mol)). By contrast, in the case of microwave-induced metal discharge, a considerably high destruction efficiency of up to 65% (mol/mol) was obtained at low concentrations. This finding highlights the potential of microwave-induced discharge for VOC removal. Initial assessment indicated that energy consumption can be acceptable.

Breathprinting and Early Diagnosis of Lung Cancer

The electronic nose (e-nose) is a promising technology as a useful addition to the currently available modalities to achieve lung cancer diagnosis. The e-nose can assess the volatile organic compounds detected in the breath and derived from the cellular metabolism. Volatile organic compounds can be analyzed to identify the individual chemical elements as well as their pattern of expression to reproduce a sensorial combination similar to a fingerprint (breathprint). The e-nose can be used alone, mimicking the combinatorial selectivity of the human olfactory system, or as part of a multisensorial platform. This review analyzes the progress made by investigators interested in this technology as well as the perspectives for its future utilization.