Sampling Of Volatile Organic Compounds Research Articles

A low cost, easy-to-assemble, open-source modular mobile sampler design for thermal desorption analysis of breath and environmental VOCs

Exhaled breath vapor contains hundreds of volatile organic compounds (VOCs), which are the byproducts of health and disease metabolism, and they have clinical and diagnostic potential. Simultaneous collection of breath VOCs and background environmental VOCs is important to ensure analyses eliminate exogenous compounds from clinical studies. We present a mobile sampling system to extract gaseous VOCs onto commercially available sorbent-packed thermal desorption tubes. The sampler can be connected to a number of commonly available disposable and reusable sampling bags, in the case of this study, a Tedlar bag containing a breath sample. Alternatively, the inlet can be left open to directly sample room or environmental air when obtaining a background VOC sample. The system contains a screen for the operator to input a desired sample volume. A needle valve allows the operator to control the sample flow rate, which operates with an accuracy of −1.52 ± 0.63% of the desired rate, and consistently generated that rate with 0.12 ± 0.06% error across repeated measures. A flow pump, flow sensor and microcontroller allow volumetric sampling, as opposed to timed sampling, with 0.06 ± 0.06% accuracy in the volume extracted. Four samplers were compared by sampling a standard chemical mixture, which resulted in 6.4 ± 4.7% error across all four replicate modular samplers to extract a given VOC. The samplers were deployed in a clinical setting to collect breath and background/environmental samples, including patients with active SARS-CoV-2 infections, and the device could easily move between rooms and can undergo required disinfection protocols to prevent transmission of pathogens on the case exterior. All components required for assembly are detailed and are made publicly available for non-commercial use, including the microcontroller software. We demonstrate the device collects volatile compounds, including use of chemical standards, and background and breath samples in real use conditions.

Characteristics and Source Apportionment of Vehicular VOCs Emissions in a Tunnel Study

To explore the emission characteristics of volatile organic compounds (VOCs) from vehicular exhaust sources and evaporative sources with ethanol gasoline (E10) as the main fuel, VOCs sampling campaigns were carried out in the north third ring tunnel of Zhengzhou city for two consecutive weeks in December 2019. In addition, the characteristics of traffic flow and environmental information were also monitored in the tunnel. Firstly, 106 VOCs were quantified using gas chromatography/mass spectrometry (GC/MS), and then source apportionment of VOCs in the tunnel was carried out using a positive matrix factorization (PMF5.0)-chemical mass balance (CMB8.2) composite model. Finally, the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) of vehicle exhaust sources and evaporative sources were analyzed using the maximum incremental reactivity (MIR) and fractional aerosol coefficient (FAC). The results showed that ρ(VOCs) in the tunnel was (2794.5±147.4) μg·m-3 during the experiment, among which halogenated hydrocarbons[(32.4±2.0)%] accounted for the highest proportion, followed by aromatic hydrocarbons[(27.5±0.6)%] and alkanes[(23.3±0.8)%]. Source apportionment of vehicular VOCs showed that exhaust emissions (62.5%)>evaporative emissions (37.5%), whereas the contribution of OFP was that exhaust emissions (71.9%)>evaporative emissions (28.1%), and the contribution of SOAFP was that exhaust emissions (75.8%)>evaporative emissions (24.2%). The dominant components of OFP in evaporative sources were m,p-diethylbenzene, isoprene, and trans-2-pentene, whereas m,p-diethylbenzene, m,p-xylene, and 1,2,3-trimethylbenzene were the dominant components of SOAFP. The major components of OFP in exhaust sources were m,p-xylene, 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene, whereas m,p-xylene, m,p-diethylbenzene, and 1,3,5-trimethylbenzene were the dominant components of SOAFP. In regions where ethanol gasoline is used, special attention should be paid not only to the exhaust emissions control but also to strengthening the emissions reduction of VOCs from vehicle evaporative sources, especially the high active components such as aromatic hydrocarbons and alkenes.

Sources and Seasonal Variance of Ambient Volatile Organic Compounds in the Typical Industrial City of Changzhi, Northern China

Volatile organic compounds (VOCs) emitted from industrial processes, which are major emission sources of air pollutants, could cause significant impacts on air quality. However, studies on the comprehensive analysis from sources contributing to the health risk perspective regarding ambient VOCs in industrial cities are limited. In this study, VOC samples were collected from 15 April 2018 to 19 October 2018 in Changzhi, a typical industrial city in northern China, and a total of 57 VOCs were measured for analysis. The average VOC concentrations were 54.4 µg·m−3, with the highest concentrations in autumn (58.4 µg·m−3). Ambient VOCs in spring, summer and autumn were all dominated by alkanes (66.8%), with contributions of 70.3%, 66.3% and 63.8%, respectively. The top five concentrations of total VOCs were isopentane (19.0%), ethane (9.5%), n-butane (8.1%), benzene (7.9%) and propane (5.2%), indicating that vehicle exhaust and coal combustion are the main sources of VOCs. Source apportionment by principal component analysis showed that vehicle exhaust (27.5%) and coal combustion (23.5%) were the main sources of VOCs in Changzhi, followed by industrial production (17.4%), solvent evaporation (13.5%), liquefied petroleum gas/natural gas leaking (9.5%), and biogenic emissions (8.7%). Sources of coal combustion and vehicle exhaust contributed more VOCs than industrial production. The carcinogenic risks of benzene (3.4 × 10−5) and ethylbenzene (2.2 × 10−6) were higher than the limit levels (1 × 10−6). Coal combustion contributed most (25.3%) to the carcinogenic risks because of its high VOC emissions. In an industrial city such as Changzhi, vehicle exhaust and coal combustion have become major sources of ambient air VOCs owing to the increasingly stringent industrial standards. Therefore, VOCs from vehicle exhaust and coal combustion also need to take into account mitigation measures for VOCs from the perspective of source contribution to health risk.

TD-GC/MS analysis of indoor air pollutants (VOCs, PM) in hair salons

Hairdressing personnel is daily exposed to various chemical air pollutants, and specifically to Volatile Organic Compounds (VOCs) and Particulate Matter (PM) in hair salons. This is of concern, due to the hazardous effects of these chemicals on the individual's health. Nevertheless, a limited exposure assessment of indoor air quality (IAQ) has been performed. The aim of this study was to analyze the indoor air in 5 hair salons, to assess the IAQ of the occupational exposure, and to identify the main VOCs produced or activities responsible for the respective indoor pollution. The chemical analysis took place inside the salon environment by monitoring the emitted VOCs, as well as the PM of 1, 2.5, 4, and 10 μm aerodynamic diameter. The sampling of VOCs was performed by adsorption of pollutants on Tenax TA sorbent tubes, that were subsequently analyzed using a thermal desorption unit coupled to gas chromatography/mass spectrometry (TD-GC/MS). The obtained results showed that hair products are a major source of air pollutants, as elevated concentrations of VOCs and PM are released in the working environment. Furthermore, the type and concentration of VOCs are affected by the various hair treatment activities taking place in the salons. Among the main compounds detected there was benzene, toluene, ethylbenzene, and xylenes, known as BTEX, as well as, diethyl phthalate, 1,4-dioxane, etc. More than 50 VOCs were identified (occurrence ≥60%) and 14 of them were quantified. Their average concentration levels varied from 12 μg m−3 for naphthalene to 941 μg m−3 for toluene. The measuring levels for PM revealed violations of the EPA and WHO international standards for permissible limit concentrations; this was the case in all hair treatment activities but mostly during keratin treatment. Hence, much more effort is needed to reduce the respective concentration levels of PM and VOCs, that contribute to self-reported health problems.

Atmospheric VOCs Pollution Characteristics and Health Risk Assessment of Large-scale Integrated Industrial Area and Surrounding Areas in Southwest China

To investigate the characteristics of atmospheric volatile organic compound (VOCs) pollution and promote VOCs pollution prevention and control in industrial areas, in December 2020, VOCs samples collected using Summa Canisters at three observation sites were used to study the characteristics of VOCs pollution and source apportionment and to conduct a health risk assessment in large integrated industrial areas and surrounding urban areas in southwest China. The results showed that the mean φ(TVOCs) at site A and site B in an industrial area and at a third urban site were 105.25×10-9, 222.92×10-9, and 82.87×10-9, respectively. Monochloromethane, dichloromethane, acetone, ethanol, and ethane were the species with higher volume fractions at the three sites. Aromatic hydrocarbons and OVOCs had a large contribution to the ozone formation potential (OFP), with a cumulative contribution of more than 50%, and the main reactive species were methyl methacrylate, toluene, p-xylene, and o-xylene; the secondary organic aerosol formation potential (SOAP) of aromatic hydrocarbons contributed more than 80%, with the main active species being toluene, p-xylene, and o-xylene. The results of PMF source analysis showed six main sources of VOCs, in the descending order of the petrochemical industry (21.83%), industrial waste incineration (18.6%), pharmaceutical manufacturing (16.99%), fossil fuel combustion (16.03%), motor vehicle exhaust (14.23%), and chemical manufacturing (12.32%). The mean values of the hazard index (HI) of site A and site B in the industrial area and in the urban site were 0.55, 0.68, and 0.41, respectively, and the mean lifetime cancer risk (LCR) values were 6.71×10-6, 6.72×10-6, and 6.58×10-6, respectively. Both HI and LCR in industrial areas were larger than those in urban areas. The quantitative assessment of risk sources showed that motor vehicle exhaust and fossil fuel combustion contributed relatively high carcinogenic risks.

Genetic algorithm (GA) - Artificial neural network (ANN) modeling for the emission rates of toxic volatile organic compounds (VOCs) emitted from landfill working surface

Volatile organic compounds (VOCs) emitted from the working surface of landfills have received increasing attention due to the potential risks to human health. Quantifying the emission rates of risky VOCs is important to their health risk assessment but is also challenging because of their high variation and complicated relationship between the emission rates and various influencing factors. In this study, a continuous nine-month sampling of VOCs was conducted on a landfill working surface to identify dominant VOCs that are risky to human health and to construct artificial neural network (ANN) models for their emission rates by involving 105 datasets. Among the 63 detected VOCs, ethanol presented the highest emission rate (885.28 ± 1398.10 μg·m−2·s−1), and the dominant compounds with high emission rates and detection frequencies were characterized in each category. According to the human toxicity impact scores calculated with USEtox method, carbon tetrachloride, ethanol, tetrachloroethylene, 1, 2-dichloroethane, benzene, ethylbenzene, and chloroform were identified as the dominant carcinogenic VOCs, and acrolein, carbon tetrachloride, and 1, 2-dichloropropane were the dominant noncarcinogenic VOCs. ANN models were established for the emission rates of six typical risky VOCs, with meteorological conditions and waste compositions as input parameters and emission rates as output parameters. With the structure optimization and genetic algorithm, all the ANN models achieved good performance and excellent prediction capability with high R2 and low root mean square error (RMSE) values. The emission rates under a 95% probability were predicted for each risky VOCs via the established ANN models, by randomly sampling the input parameters under their data distribution. The approach proposed and results obtained can provide scientific methodology and important information for the monitoring, prediction, and health risk assessment of the VOCs emitted from MSW landfills.

Volatile Organic Compounds Analysis as a Potential Novel Screening Tool for Breast Cancer: A Systematic Review.

Introduction:An early diagnosis is crucial in reducing mortality among people who have breast cancer (BC). There is a shortfall of characteristic early clinical symptoms in BC patients, highlighting the importance of investigating new methods for its early detection. A promising novel approach is the analysis of volatile organic compounds (VOCs) produced and emitted through the metabolism of cancer cells.Methods:The purpose of this systematic review is to outline the published research regarding BC-associated VOCs. For this, headspace analysis of VOCs was explored in patient-derived body fluids, animal model-derived fluids, and BC cell lines to identify BC-specific VOCs. A systematic search in PubMed and Web of Science databases was conducted according to the PRISMA guidelines.Results:Thirty-two studies met the criteria for inclusion in this review. Results highlight that VOC analysis can be promising as a potential novel screening tool. However, results of in vivo, in vitro and case-control studies have delivered inconsistent results leading to a lack of inter-matrix consensus between different VOC sampling methods.Discussion:Discrepant VOC results among BC studies have been obtained, highly due to methodological discrepancies. Therefore, methodological issues leading to disparities have been reviewed and recommendations have been made on the standardisation of VOC collection and analysis methods for BC screening, thereby improving future VOC clinical validation studies.

A pilot study characterizing tetrachloroethylene exposure with exhaled breath in an impacted community

Martinsville, Indiana overlays four groundwater contamination plumes, including a U.S. Environmental Protection Agency (EPA)-designated Superfund site. The primary contaminants are tetrachloroethylene (PCE), trichloroethylene (TCE), and other volatile organic compounds (VOCs). Martinsville represents many similar communities facing the challenge of groundwater and soil contamination and vapor intrusion, where residents are often frustrated by the lack of help in understanding and addressing the problem. The objective of this study was to evaluate PCE in exhaled breath to identify and quantify exposure to PCE and to explore the extent and level of PCE exposure among community residents. We measured chlorinated VOCs in exhaled breath samples from 38 healthy individuals who lived either in a contamination area or outside any plume area. We also measured VOCs in indoor air and tap water samples collected from 10 homes. PCE was detected in all exhaled breath samples (mean: 6.6 μg/m3; range: 1.9–44 μg/m3) and tap water samples (mean: 0.74 μg/L; range: 0.39–0.92 μg/L). PCE was detected in six of nine (66%) homes with air concentrations ranging from 1.6 to 70 μg/m3, exceeding the EPA action level of 42 μg/m3. We did not detect TCE or any other chlorinated VOCs in these samples. PCE exposure occurred among individuals living on the EPA Superfund site, as well as among those living on other plume sites and those living outside any known plumes. Preventive measures should focus on identifying highly exposed groups and reducing their exposures, followed by addressing moderately elevated exposures in the community. Our results demonstrated that PCE in exhaled breath can be used as an effective tool in community engaged environmental health research to evaluate the extent and level of community exposure, increase awareness, and promote residents’ participation in research and site cleanup decision-making.

A Strategy for Field Evaluations of Exposures and Respiratory Health of Workers at Small- to Medium-Sized Coffee Facilities.

Coffee production is a global industry with roasteries throughout the world. Workers in this industry are exposed to complex mixtures of gases, dusts, and vapors including carbon monoxide, carbon dioxide, coffee dust, allergens, alpha-diketones, and other volatile organic compounds (VOCs). Adverse respiratory health outcomes such as respiratory symptoms, reduced pulmonary function, asthma, and obliterative bronchiolitis can occur among exposed workers. In response to health hazard evaluations requests received from 17 small- to medium-sized coffee facilities across the United States, the National Institute for Occupational Safety and Health conducted investigations during 2016–2017 to understand the burden of respiratory abnormalities, exposure characteristics, relationships between exposures and respiratory effects, and opportunities for exposure mitigation. Full-shift, task-based, and instantaneous personal and area air samples for diacetyl, 2,3-pentanedione and other VOCs were collected, and engineering controls were evaluated. Medical evaluations included questionnaire, spirometry, impulse oscillometry, and fractional exhaled nitric oxide. Exposure and health assessments were conducted using standardized tools and approaches, which enabled pooling data for aggregate analysis. The pooled data provided a larger population to better address the requestors' concern of the effect of exposure to alpha-diketones on the respiratory heath of coffee workers. This paper describes the rationale for the exposure and health assessment strategy, the approach used to achieve the study objectives, and its advantages and limitations.

Exploring Methods for Surveillance of Occupational Exposure from Additive Manufacturing in Four Different Industrial Facilities.

3D printing, a type of additive manufacturing (AM), is a rapidly expanding field. Some adverse health effects have been associated with exposure to printing emissions, which makes occupational exposure studies important. There is a lack of exposure studies, particularly from printing methods other than material extrusion (ME). The presented study aimed to evaluate measurement methods for exposure assessment in AM environments and to measure exposure and emissions from four different printing methods [powder bed fusion (PBF), material extrusion (ME), material jetting (MJ), and vat photopolymerization] in industry. Structured exposure diaries and volatile organic compound (VOC) sensors were used over a 5-day working week. Personal and stationary VOC samples and real-time particle measurements were taken for 1 day per facility. Personal inhalable and respirable dust samples were taken during PBF and MJ AM. The use of structured exposure diaries in combination with measurement data revealed that comparatively little time is spent on actual printing and the main exposure comes from post-processing tasks. VOC and particle instruments that log for a longer period are a useful tool as they facilitate the identification of work tasks with high emissions, highlight the importance of ventilation and give a more gathered view of variations in exposure. No alarming levels of VOCs or dust were detected during print nor post-processing in these facilities as adequate preventive measures were installed. As there are a few studies reporting negative health effects, it is still important to keep the exposure as low as reasonable.

Field measurement of spatiotemporal distributions of ambient concentrations of volatile organic compounds around a high-tech industrial park using a drone

A quadrotor drone, carrying a 3 L Teflon bag and an active sampling pump, collected ambient air samples around a high-tech industrial park to investigate the distribution characteristics of volatile organic compounds (VOCs). A total of 490 air samples were collected in winter, spring, summer and autumn in one year and analyzed. Ambient VOC samples were obtained using a drone on the ground and at the altitude of 50 m which is approximately the heights of chimney outlets of the factories once per month at four sites around the high-tech industrial park. Acetone, toluene, methyl ethyl ketone (MEK), p-xylene, m-xylene and ethyl acetate were the most commonly detected VOCs; these are commonly used solvents in semiconductor, LCD panel and optoelectronics manufacturing in the high-tech industrial park. The highest total VOC concentration (TVOC) on the ground was 346.8 μg/m3 (including acetone of 107.9 μg/m3 and m,p-xylenes of 65.4 μg/m3) and that at the altitude of 50 m was 278.3 μg/m3 (including acetone of 104.0 μg/m3 and m,p-xylenes of 36.3 μg/m3) on an August day. Based on the concentration ratios of m,p-xylenes to ethylbenzene, the exhaust of VOCs from neighboring plants affected air quality at the altitude of 50 m. The VOC-rich air affected the ambient air quality that was supplied to clean rooms, increasing the operating cost of the high-tech industrial factories in the park.

Sampling Volatile Organic Compounds from Individual Cotton Leaves to Test Effects of Fungal Endophyte Treatments

Facultative fungal endophytes are unspecialized plant-associated fungi capable of colonizing plant tissues without causing symptoms of disease. Studies suggest facultative fungal endophytes enhance cotton (Gossypium hirsutum L.) plant defense against insect herbivores and might alter emissions of volatile organic compounds. We tested for changes in emissions of volatile organic compounds using cotton plants treated with facultative fungal endophtytes Beauveria bassiana (Balsamo-Crivelli) Vuillemin strain GHA and Phialemonium inflatum (Burnside) strain TAMU490 in the presence and absence of herbivory. Solid-phase micro-extraction was used to sample static headspace of individual leaves in collection chambers designed specifically for the experiment. Relative abundance of volatile organic compounds was significantly affected by herbivory, but differences caused by treatment with B. bassiana or P. inflatum were not significant. Findings showed our sampling method can be used to assess constitutive and herbivore-induced volatile organic compound profiles from individual leaves, but further studies need to investigate mechanisms underlying facultative fungal endophyte-mediated herbivore resistance in cotton.

Are Volatile Organic Compounds Accurate Markers in the Assessment of Colorectal Cancer and Inflammatory Bowel Diseases? A Review.

Simple SummaryEarly diagnosis is crucial for reducing colorectal cancer-related mortality in both the general population and inflammatory bowel disease. Volatile organic compound (VOC) analysis is a promising alternative to the gold standard procedure, endoscopy, for early detection and surveillance of colorectal diseases. This review aimed to provide a general overview of the most recent evidence in this area on VOC testing in breath, stool, and urine samples.Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the Western world. Early detection decreases incidence and mortality. Screening programs based on fecal occult blood testing help identify patients requiring endoscopic examination, but accuracy is far from optimal. Among the alternative strategies, volatile organic compounds (VOCs) represent novel potentially useful biomarkers of colorectal cancer. They also represent a promising tool for the screening of both intestinal inflammation and related CRC. The review is focused on the diagnostic potential of VOCs in sporadic CRC and in inflammatory bowel diseases (IBD), which increase the risk of CRC, analyzing future clinical applications. Despite limitations related to inadequate strength of evidence, differing analytical platforms identify different VOCs, and this unconventional approach for diagnosing colorectal cancer is promising. Some VOC profiles, besides identifying inflammation, seem disease-specific in inflammatory bowel diseases. Thus, breath, urine, and fecal VOCs provide a new and promising clinical approach to differential diagnosis, evaluation of the inflammatory status, and possibly the assessment of treatment efficacy in IBD. Conversely, specific VOC patterns correlating inflammatory bowel disease and cancer risk are still lacking, and studies focused on this issue are strongly encouraged. No prospective studies have assessed the risk of CRC development by using VOCs in samples collected before the onset of disease, both in the general population and in patients with IBD.

Robotized Noncontact Open-Space Mapping of Volatile Organic Compounds Emanating from Solid Specimens.

Analysis of volatile organic compounds (VOCs) is normally preceded by sample homogenization and solvent extraction. This methodology does not provide spatial resolution of the analyzed VOCs in the examined matrix. Here, we present a robotized pen-shaped probe for open-space sampling and mapping of VOCs emanating from solid specimens (dubbed "PENVOC"). The system combines vacuum-assisted suction probe, mass spectrometry, and robotic handling of the probe. The VOCs are scavenged from the sample surface by a gentle hydrodynamic flow of air sustained by a vacuum pump. The sampled gas is transferred to the proximity of corona discharge in an atmospheric pressure chemical ionization source of a tandem mass spectrometer. The PENVOC has been attached to a robotic arm to enable unattended scanning of flat surfaces. The specimens can be placed away from the mass spectrometer during the scan. The robotized PENVOC has been characterized using chemical standards (benzaldehyde, limonene, 2-nonanone, and ethyl octanoate). The limits of detection are in the range from 2.33 × 10-5 to 2.68 × 10-4 mol m-2. The platform has further been used for mapping of VOCs emanating from a variety of specimens: flowers, glove exposed to smoke, fuel stains, worn medical face mask, worn clothing, cheese, ham, and fruits. The chemical maps show unique distributions of the VOCs on the scanned surfaces. Obtaining comparable results (VOC maps) using other techniques (e.g., repetitive headspace sampling prior to offline analysis) would be time-consuming. The presented mapping technique may find applications in environmental, forensic, and food science.

Detecting volatile organic compounds to locate human remains in a simulated collapsed building

The occurrence of mass disasters has increased worldwide due to changing environments from global warming and a heightened threat of terrorism acts. When these disasters strike, it is imperative to rapidly locate and recover human victims, both the living and deceased. While search and rescue dogs are used to locate the living, cadaver detection dogs are typically tasked with locating the dead. This can prove challenging because commingling of victims is likely to occur during disasters in populated areas which will impact the decomposition process and the resulting odour produced. To date, there has been no research to investigate the process of human decomposition in a mass disaster scenario or to understand which compounds are detectable by cadaver detection dogs. Hence, the current study investigated the human decomposition process and subsequent volatile organic compound (VOC) production in two simulated building collapse scenarios with six human donors placed in each scenario. The human remains were only recovered after a period of one month, during which time VOC samples were collected and analysed using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry. A considerable degree of differential decomposition was observed upon recovery of the human remains, which was carried out as a part of a police disaster victim recovery training exercise. The location of the bodies in the disaster area was found to impact the decomposition process. The VOC profile was found to correlate with the decomposition process. Fifteen days following the simulated disaster, the VOC profile changed showing that a detectable change in the decomposition process had occurred. Overall, the changing VOC profile can inform the training of cadaver detection dogs for these unique scenarios.

Investigation of the relationship between skin-emitted volatile fatty acids and skin surface acidity in healthy participants—a pilot study

Volatile organic compounds (VOCs) emitted from human skin are of great interest in general in research fields including disease diagnostics and comprise various compound classes including acids, alcohols, ketones and aldehydes. The objective of this research is to investigate the volatile fatty acid (VFA) emission as recovered from healthy participant skin VOC samples and to characterise its association with skin surface acidity. VOC sampling was performed via headspace-solid phase microextraction with analysis via gas chromatography-mass spectrometry. Several VFAs were recovered from participants, grouped based on gender and site (female forehead, female forearm, male forearm). Saturated VFAs (C9, C12, C14, C15, C16) and the unsaturated VFA C16:1 (recovered only from the female forehead) were considered for this study. VFA compositions and abundances are discussed in the context of body site and corresponding gland type and distribution, and their quantitative association with skin acidity investigated. Normalised chromatographic peak areas of the recovered VFAs were found to linearly correlate with hydrogen ion concentration measured at each of the different sites considered and is the first report to our knowledge to demonstrate such an association. Our observations are explained in terms of the free fatty acid content at the skin surface which is well-established as being a major contributor to skin surface acidity. Furthermore, it is interesting to consider that these VFA emissions from skin, governed by equilibrium vapour pressures exhibited at the skin surface, will be dependent on skin pH. It is proposed that these pH-modulated equilibrium vapour pressures of the acids could be resulting in an enhanced VFA emission sensitivity with respect to skin surface pH. To translate our observations made here for future wearable biodiagnostic applications, the measurement of skin surface pH based on the volatile emission was demonstrated using a pH indicator dye in the form of a planar colorimetric sensor, which was incorporated into a wearable platform and worn above the palm surface. As acidic skin surface pH is required for optimal skin barrier function and cutaneous antimicrobial defence, it is envisaged that these colorimetric volatile acid sensors could be deployed in robust wearable formats for monitoring health and disease applications in the future.

Observation of Conditions Preceding Peak Indoor Air Volatile Org Compound Concentrations in Vapor Intrusion Studies.

Temporal and spatial variability of indoor air volatile organic compound (VOC) concentrations can complicate vapor intrusion (VI) assessment and decision-making. Indicators and tracers (I&T) of VI, such as differential temperature, differential pressure, and indoor radon concentration, are low-cost lines of evidence to support sampling scheduling and interpretation of indoor air VOC sampling results. This study compares peak indoor air chlorinated VOC concentrations and I&T conditions before and during those peak events at five VI sites. The sites differ geographically and in their VI conceptual site models (CSM). Relative to site-specific baseline values, the results show that cold or falling outdoor temperatures, rising cross slab differential pressures, and increasing indoor radon concentrations can predict peak VOC concentrations. However, cold outdoor air temperature was not useful at one site where elevated shallow soil temperature was a better predictor. Correlations of peak VOC concentrations to elevated or rising barometric pressure and low wind speed were also observed with some exceptions. This study shows how the independent variables that control or predict peak indoor air VOC concentrations are specific to building types, climates, and VI CSMs. More I&T measurements at VI sites are needed to identify scenario-specific baseline and peak related I&T conditions to improve decision-making.

Evaluation of health risks associated with exposure to volatile organic compounds from household fuel combustion in southern India

Volatile organic compounds (VOCs) from household cook-fuel use are a major public health concern in low and middle income countries (LMICs), but health risk assessments have largely been based on measurements of fine particulate matter. We report results from cooking period measurements of 21 non-methane VOCs (NMVOCs) and estimated lifetime cancer risk for women cooks in the Tamil Nadu Air Pollution and Health Effects (TAPHE) cohort in Southern India. We enrolled 112 (56 biomass, 23 kerosene and 33 liquefied petroleum gas (LPG) using) TAPHE households to perform kitchen area measurements during the cooking period. VOC samples were collected on mixed-bed sorbent thermal desorption tubes using low-volume air samplers and analyzed using automated thermal desorption on a GC-MS system. Pentafluorobenzene, 1,4-difluorobenzene and chlorobenzene-d5 were used as internal standards that provided recoveries ranging from 81.7% to 119.9%. Total VOC concentrations were 4617 µg/m3, 2839 µg/m3 and 1639 µg/m3 while total BTEXS (i.e. benzene, toluene, ethylbenzene, m,p-xylene, o-xylene and styrene) concentrations were 139 µg/m3,121 µg/m3 and 245 µg/m3 among biomass, LPG and kerosene using households, respectively. Sampling season, type of food cooked and kitchen ventilation were significantly associated with measured total NMVOC concentrations. Lifetime cancer risks were estimated to be 2.93 × 10−3, 1.55 × 10−4 and 8.18 × 10−5, for biomass, kerosene and LPG fuel users, respectively with 1,2,3-trichloropropane, benzene, 1,4-dichlorobenze, 1,2-dibromoethane and chloroform contributing maximally to excess cancer risks. Health risk assessments for women cooks in LMICs should be expanded to include NMVOCs as these risks may not be adequately addressed through measurements of fine particulate matter (PM2.5) pollution alone.

Evaluating a commercially available in-duct bipolar ionization device for pollutant removal and potential byproduct formation

We conducted a series of experiments to evaluate the gas and particle removal effectiveness and potential for byproduct formation resulting from the operation of a commercially available in-duct bipolar ionization device. Laboratory tests were conducted with the ionizer installed in a small air handler serving a large semi-furnished chamber. Chamber experiments were conducted under (i) normal operating conditions to characterize the impact of the ionizer on concentrations of particles (0.01–10 μm), ozone (O3), nitrogen dioxide (NO2), volatile organic compounds (VOCs), and aldehydes, and (ii) particle injection and decay conditions to characterize the impact of the ionizer operation on particle loss rates. The field test involved air sampling of particulates (0.01–10 μm), O3, and VOCs upstream and downstream of an operating ionizer device installed in an air handling unit serving an occupied office building. Both the chamber and field tests suggested that the use of the tested bipolar ionization unit led to a decrease in some hydrocarbons (e.g., xylenes) among the lists of compounds we were able to analyze, but an increase in others, most prominently oxygenated VOCs (e.g., acetone, ethanol) and toluene. Ionizer operation appeared to minimally impact particle, O3, and NO2 concentrations during normal operating conditions. Particle injection and decay experiments in the chamber suggest that operation of the ionizer unit led to a small increase in loss rates for ultrafine particles (<0.15 μm) and a small decrease in loss rates for larger particles (>0.3 μm), but with negligible net changes in estimated PM2.5 loss rates.

Reproducibility of the Quantification of Reversible Wall Interactions in VOC Sampling Lines

Volatile Organic Compounds (VOCs) are widely measured at ppb and ppt level in many contexts, from therapeutic drug control in respiratory diseases to monitoring of climate change and indoor air quality. The need for accuracy is a common denominator in all these fields. The interactions between gas mixtures and solid surfaces in sampling lines and instruments play an important role in calculating the total uncertainty of the amount of VOC. The amount of substances in the gas mixture is affected by its reversible and irreversible interactions with the sampling line. The main aim of this paper is to propose and discuss a method to quantify the amount of substance segregated by reversible interactions on sampling lines. To validate the proposed method, the areic amount of a VOC (Acetone) is measured for a commercial test pipe (Sulfinert®) as the amount of substance per unit area of the internal surface of the test pipe segregated from the flowing gas mixture. Stainless steel coated by Sulfinert® was chosen as a test material because of its wide use and its limited irreversible and permeation effects. A certified gas mixture of Acetone in air with a nominal mole fraction of 10 µmol mol−1 was used for validation. Broad temperature control was used and the sensibility of the method to the temperature and the pressure has been evaluated to correct the bias due to physical condition. The sensitivity to the residence time and the Reynolds number of the gas flow has been evaluated to verify the reaching of equilibrium and the limits of the applicability of the method. The areic amount of Acetone at equilibrium on Sulfinert® coated pipe was measured as 40 nmol m−2, and an equilibrium constant value of around 0.2 m was calculated as the ratio between the superficial amount segregated on the wall and the amount concentration of Acetone in the mixture, both at the equilibrium. The observed reproducibility was better than 2.5%. This method is aimed to investigate VOC losses due to interactions for many VOC/material systems at a lower amount of substance levels.