Measurement of nitrogen dioxide in cigarette smoke using quantum cascade tunable infrared laser differential absorption spectroscopy (TILDAS)

The impact of second-hand smoke on nitrogen oxides concentrations in a small interior

Nitrogen oxides (NO_x), especially nitrogen dioxide (NO₂), are among the most hazardous forms of air pollution. Tobacco smoke is a main indoor source of NO_x, but little information is available about their concentrations in second-hand smoke (SHS), particularly in small indoors. This study presents data of NO_x and its main components nitric oxide (NO) and NO₂ in SHS emitted by ten different cigarette brands measured in a closed test chamber with a volume of 2.88 m³, similar to the volume of vehicle cabins. The results show substantial increases in NO_x concentrations when smoking only one cigarette. The NO₂ mean concentrations ranged between 105 and 293 µg/m³, the NO₂ peak concentrations between 126 and 357 µg/m³. That means the one-hour mean guideline of 200 µg/m³ for NO₂ of the World Health Organization was exceeded up to 47%, respectively 79%. The measured NO₂ values show positive correlations with the values for tar, nicotine, and carbon monoxide stated by the cigarette manufacturers. This study provides NO₂ concentrations in SHS at health hazard levels. These data give rise to the necessity of health authorities' measures to inform about and caution against NO_x exposure by smoking in indoor rooms.

Surviving With Smog and Smoke: Precision Interventions?

Despite continuous efforts of regional governmental agencies, air pollution remains a major threat to public health worldwide. In January 2017, a severe episode of smog similar to the Great Smog of 1952 occurred in London. The longest episode of Chinese haze also developed in Beijing, during which levels of particulate matter < 2.5 μm rose to 500 μg/m³. European smog and Chinese haze are associated with large numbers of premature deaths each year, at 400,000 and 1.2 million, respectively, primarily from respiratory diseases, cerebrovascular diseases, and ischemic heart diseases. In addition to air pollution, some are exposed to other harmful environmental factors, such as secondhand smoke. For countries with large populations of smokers, such as China, India, the United States, and Russia, surviving both smog and smoke is a serious problem. With novel genomic and epigenomic studies revealing air pollution- and smoking-induced mutational signatures and epigenetic editing in diseases such as lung cancer, it has become feasible to develop precision strategies for early intervention in the disease-causing pathways driven by the specific mutations or epigenetic regulations, or both. New therapies guided by gene-drug interactions and genomic biomarkers may also be developed. We discuss both perspectives regarding the urgent need to manage the toxic effects of smog and smoke for the benefit of global health and the novel concept of precision intervention to protect the exposed individuals when exposure to smog and secondhand smoke cannot be voluntarily avoided or easily modified.

Acetyl Radical Generation in Cigarette Smoke: Quantification and Simulations

Free radicals are present in cigarette smoke and can have a negative effect on human health. However, little is known about their formation mechanisms. Acetyl radicals were quantified in tobacco smoke and mechanisms for their generation were investigated by computer simulations. Acetyl radicals were trapped from the gas phase using 3-amino-2, 2, 5, 5-tetramethyl-proxyl (3AP) on solid support to form stable 3AP adducts for later analysis by high performance liquid chromatography (HPLC), mass spectrometry/tandem mass spectrometry (MS-MS/MS) and liquid chromatography-mass spectrometry (LC-MS). Simulations were performed using the Master Chemical Mechanism (MCM). A range of 10-150 nmol/cigarette of acetyl radical was measured from gas phase tobacco smoke of both commerial and research cigarettes under several different smoking conditions. More radicals were detected from the puff smoking method compared to continuous flow sampling. Approximately twice as many acetyl radicals were trapped when a glass filber particle filter (GF/F specifications) was placed before the trapping zone. Simulations showed that NO/NO₂ reacts with isoprene, initiating chain reactions to produce hydroxyl radical, which abstracts hydrogen from acealdehyde to generate acetyl radical. These mechanisms can account for the full amount of acetyl radical detected experimentally from cigarette smoke. Similar mechanisms may generate radicals in second hand smoke.

Role of the Filters in the Formation and Stabilization of Semiquinone Radicals Collected from Cigarette Smoke

The fractional pyrolysis of Bright tobacco was performed in nitrogen atmosphere over the temperature range of 240 - 510 °C in a specially constructed, high temperature flow reactor system. Electron paramagnetic resonance (EPR) spectroscopy was used to analyze the free radicals in the initially produced total particular matter (TPM) and in TPM after exposure to ambient air (aging). Different filters have been used to collect TPM from tobacco smoke: cellulosic, cellulose nitrate, cellulose acetate, nylon, Teflon and Cambridge. The collection of the primary radicals (measured immediately after collection of TPM on filters), the formation and stabilization of the secondary radicals (defined as radicals formed during aging of TPM samples on the filters) depend significantly on the material of the filter. A mechanistic explanation about different binding capability of the filters decreasing in the order: cellulosic < cellulose nitrate < cellulose acetate < nylon ~ teflon is presented. Different properties were observed for the Cambridge filter. Specific care must be taken using the filters for identification of radicals from tobacco smoke to avoid artifacts in each case.

Formation of mainstream cigarette smoke constituents prioritized by the World Health Organization--yield patterns observed in market surveys, clustering and inverse correlations

The WHO TobReg proposed mandating ceilings on selected smoke constituents determined from the market-specific median of nicotine-normalized yield distributions. Data validating this regulatory concept were obtained from essentially single-blend surveys. This process is strongly impacted by inverse correlations among yields. In the present study, 18 priority WHO smoke constituent yields (nicotine-normalized) were determined (using two smoking regimens) from 262 commercial brands including American, Virginia and local blends from 13 countries. Principal Component Analysis was used to identify yields patterns, clustering of blend types and the inverse correlations causing these clusters. Three principal components explain about 75% of total data variability. PC1 was sensitive to the relative levels of gas- and particle-phase compounds. PC2 and PC3 cluster American- and Virginia-blends, revealing inverse correlations: Nitrogen oxides and amino- or nitroso-aromatic compounds inversely correlate to either formaldehyde and acrolein, or benzo(a)pyrene and di-hydroxybenzenes. These results can be explained by reviewing the processes determining each components smoke delivery. Regulatory initiatives simultaneously targeting selected smoke constituents in markets with mixed blend styles will be strongly impacted by the inverse correlations described. It is difficult to predict the ultimate impact of such regulations on public health, considering the complex chemistry of cigarette smoke formation.

Pyrolysis and combustion of tobacco in a cigarette smoking simulator under air and nitrogen atmosphere

A coupling between a cigarette smoking simulator and a time-of-flight mass spectrometer was constructed to allow investigation of tobacco smoke formation under simulated burning conditions. The cigarette smoking simulator is designed to burn a sample in close approximation to the conditions experienced by a lit cigarette. The apparatus also permits conditions outside those of normal cigarette burning to be investigated for mechanistic understanding purposes. It allows control of parameters such as smouldering and puff temperatures, as well as combustion rate and puffing volume. In this study, the system enabled examination of the effects of "smoking" a cigarette under a nitrogen atmosphere. Time-of-flight mass spectrometry combined with a soft ionisation technique is expedient to analyse complex mixtures such as tobacco smoke with a high time resolution. The objective of the study was to separate pyrolysis from combustion processes to reveal the formation mechanism of several selected toxicants. A purposely designed adapter, with no measurable dead volume or memory effects, enables the analysis of pyrolysis and combustion gases from tobacco and tobacco products (e.g. 3R4F reference cigarette) with minimum aging. The combined system demonstrates clear distinctions between smoke composition found under air and nitrogen smoking atmospheres based on the corresponding mass spectra and visualisations using principal component analysis.

Microprobe sampling--photo ionization-time-of-flight mass spectrometry for in situ chemical analysis of pyrolysis and combustion gases: examination of the thermo-chemical processes within a burning cigarette

A microprobe sampling device (μ-probe) has been developed for in situ on-line photo ionization mass spectrometric analysis of volatile chemical species formed within objects consisting of organic matter during thermal processing. With this approach the chemical signature occurring during heating, pyrolysis, combustion, roasting and charring of organic material within burning objects such as burning fuel particles (e.g., biomass or coal pieces), lit cigarettes or thermally processed food products (e.g., roasting of coffee beans) can be investigated. Due to its dynamic changes between combustion and pyrolysis phases the cigarette smoking process is particularly interesting and has been chosen as first application. For this investigation the tip of the μ-probe is inserted directly into the tobacco rod and volatile organic compounds from inside the burning cigarette are extracted and real-time analyzed as the glowing front (or coal) approaches and passes the μ-probe sampling position. The combination of micro-sampling with photo ionization time-of-flight mass spectrometry (PI-TOFMS) allows on-line intrapuff-resolved analysis of species formation inside a burning cigarette. Monitoring volatile smoke compounds during cigarette puffing and smoldering cycles in this way provides unparalleled insights into formation mechanisms and their time-dependent change. Using this technique the changes from pyrolysis conditions to combustion conditions inside the coal of a cigarette could be observed directly. A comparative analysis of species formation within a burning Kentucky 2R4F reference cigarette with μ-probe analysis reveals different patterns and behaviors for nicotine, and a range of semi-volatile aromatic and aliphatic species.

Carbon-centered radicals in cigarette smoke: acyl and alkylaminocarbonyl radicals

The widely accepted mechanism of formation for carbon-centered radicals in the gas-phase cigarette smoke involves reactions of NO(2) and alkadienes. However, specific examples of such radicals have never been isolated from fresh cigarette smoke or their structure determined. We have identified two previously unrecognized classes of carbon-centered radicals, alkylaminocarbonyl and acyl radicals, that are unrelated to radicals that form by NO(x) chemistry. The combined abundance of these mainstream smoke radicals is significantly higher than the alkyl radicals previously quantified by electron paramagnetic resonance (EPR) solution spin-trapping methods. The new radicals were trapped directly from smoke with either 3-amino-proxyl (3AP) or 3-cyano-proxyl radical on a solid support and identified by combination of chemical synthesis, deuterium labeling, high-resolution mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy, and ab initio quantum mechanical calculations. 3AP-R adducts were quantified both by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and by high-performance liquid chromatography with fluorescence detection (HPLC/FLD). Seven acyl and 11 alkylaminocarbonyl radicals were identified in the whole smoke of cigarettes made from single tobacco varieties and blended tobacco research cigarettes. The overall yield of these radicals was measured to be 168-245 nmol/cigarette from machine-smoked cigarettes under Federal Trade Commission (FTC) conditions. The yield was significantly reduced when the gas-phase smoke was separated from whole smoke by filtration through a 0.1 microm Cambridge filter pad or upon aging whole smoke in an inert tube.

A practical alternative to chemiluminescence-based detection of nitrogen dioxide: cavity attenuated phase shift spectroscopy

We present results obtained from a greatly improved version of a previously reported nitrogen dioxide monitor (Anal Chem. 2005, 77, 724-728) that utilizes cavity attenuated phase shift spectroscopy (CAPS). The sensor, which detects the optical absorption of nitrogen dioxide within a 20 nm bandpass centered at 440 nm, comprises a blue light emitting diode, an enclosed stainless steel measurement cell (26 cm length) incorporating a resonant optical cavity of near-confocal design and a vacuum photodiode detector. An analog heterodyne detection scheme is used to measure the phase shift in the waveform of the modulated light transmitted through the cell induced by the presence of nitrogen dioxide within the cell. The sensor, which operates at atmospheric pressure, fits into a 19 in.-rack-mounted instrumentation box, weighs 10 kg, and utilizes 70 W of electrical power with pump included. The sensor response to nitrogen dioxide (calculated as the cotangent of the phase shift) is demonstrated to be linear (r2 > 0.9999) within +/- 1 ppb over a range of 0-320 ppb (by volume). The device exhibits a detection limit (3sigma precision) of less than 60 parts per trillion (0.060 ppb) with 10 s integration, a value derived from measurements at NO2 concentration levels of both 0 and 20 ppb; the detection limit improves as the integration time is increased to several hundred seconds. The observed baseline drift is less than +/- 0.5 ppb overthe course of a month. An intercomparison of measurements of ambient NO2 concentrations over several days using this sensor with a quantum cascade laser-based infrared absorption spectrometer and a standard chemiluminescence-based NOx analyzer is presented. The data from the CAPS sensor are highly correlated (r2 > 0.99) with the other two instruments. The absolute agreement between the CAPS and each of the two other instruments is within the expected statistical noise associated with the infrared laser-based absorption spectrometer (+/- 0.3 ppb with 10 s sampling) and chemiluminescence analyzer (+/- 0.4 ppb with 60 s averaging). The major limitation concerning accuracy is a direct spectral interference with phototchemically produced 1,2-dicarbonyl species (e.g., glyoxal, methylglyoxal). However, this interference can be readily removed by shifting the detection band to a slightly longer wavelength and ensuring that the lower edge of the detection band is greater than 455 nm.

A new look at radicals in cigarette smoke

Radicals in cigarette smoke have been proposed to contribute to the harm caused by cigarette smoking. For the first time, using HPLC and high-resolution mass spectrometry analysis of stable radical adducts, we have identified specific radical species in cigarette smoke: 7 acyl and 11 alkylaminocarbonyl radicals. Their combined abundance measured in fresh whole smoke from a single 2R4F cigarette is approximately 225 nmol (1.4 x 10(17) radicals). The fiberglass Cambridge filter pad conventionally employed to separate the gas phase from mainstream smoke was found to reduce the apparent yield of these radicals, introducing artifacts of measurement. The long-accepted steady-state mechanism for the formation of carbon-centered radicals in cigarette smoke involving NO2 chemistry cannot account for these newly identified radicals, and it does not in general appear to be a major source of carbon-centered radicals in fresh mainstream cigarette smoke. Consequently, we suggest that the precise nature of radicals in cigarette smoke warrants reexamination.