Emission of volatile organic compounds and production of secondary organic aerosol from stir-frying spices

Multiple effects of relative humidity on heterogeneous ozonolysis of cooking organic aerosol proxies from heated peanut oil emissions

The exposure to cooking organic aerosols (COA) is closely related to people's daily lives. Despite extensive investigations into COA's model compounds like oleic acid, the intricacies of heterogeneous ozonolysis of real COA and the effects of ambient conditions like humidity remain elusive. In this work, the ozonolysis of COA proxies from heated peanut oil emissions was investigated using diffuse reflectance infrared Fourier transform (DRIFTS) spectroscopy, and proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS). We found that humidity hinders the reaction between ozone and CC double bonds due to the competitive adsorption of water and ozone on COA. Although visible light has little influence on the ozonolysis of COA in the absence of humidity, the ozonolytic CO production is significantly promoted by visible light in the presence of humidity. It may be attributed to the formation of water-derived reactive oxygen species (ROS, mainly HO•) from the photosensitization of polycyclic aromatic hydrocarbons (PAHs) in COA. We also found that humidity can enhance the depolymerization of carboxylic acid dimers and hydrolysis of intrinsic acetals in the COA. Moreover, humidity promotes the release of VOCs during both the dark and light ozonolysis of COA. This work reveals the important roles of humidity-responsive and photo-responsive components in COA during its ozonolysis, and the change in VOC release may guide the control of human VOC exposure in indoor air.

Ozone Chemistry on Greasy Glass Surfaces Affects the Levels of Volatile Organic Compounds in Indoor Environments

The chemistry of ozone (O3) on indoor surfaces leads to secondary pollution, aggravating the air quality in indoor environments. Here, we assess the heterogeneous chemistry of gaseous O3 with glass plates after being 1 month in two different kitchens where Chinese and Western styles of cooking were applied, respectively. The uptake coefficients of O3 on the authentic glass plates were measured in the dark and under UV light irradiation typical for indoor environments (320 nm < λ < 400 nm) at different relative humidities. The gas-phase product compounds formed upon reactions of O3 with the glass plates were evaluated in real time by a proton-transfer-reaction quadrupole-interface time-of-flight mass spectrometer. We observed typical aldehydes formed by the O3 reactions with the unsaturated fatty acid constituents of cooking oils. The formation of decanal, 6-methyl-5-hepten-2-one (6-MHO), and 4-oxopentanal (4-OPA) was also observed. The employed dynamic mass balance model shows that the estimated mixing ratios of hexanal, octanal, nonanal, decanal, undecanal, 6-MHO, and 4-OPA due to O3 chemistry with authentic grime-coated kitchen glass surfaces are higher in the kitchen where Chinese food was cooked compared to that where Western food was cooked. These results show that O3 chemistry on greasy glass surfaces leads to enhanced VOC levels in indoor environments.

Particulate Matter and Volatile Organic Compound Emissions Generated from a Domestic Air Fryer

Air frying has become a popular cooking method for domestic cooking, but the level of released indoor air pollutants is poorly understood. In this work, we compared particle and gas phase emission factors (EF) and particle size distributions between cooking with a domestic air fryer and a pan for a variety of foods. The PM10 EFs of air frying chicken wings and breast were higher than pan cooking by a factor of 2.1 and 5.4, respectively. On the other hand, a higher PM10 emission factor from air frying can be achieved by increasing the amount of oil to levels similar to or above those from pan-frying for French fries and asparagus. We propose that higher temperature and greater turbulence lead to higher PM10 EFs for cooking with the air fryer compared with the pan for the same mass of oil added. EFs of volatile organic compounds (VOCs) are also generally higher for cooking with the air fryer compared with the pan: 2.5 times higher for French fries and 4.8 times higher for chicken breast. Our study highlights the potential risk of higher indoor PM10 levels associated with domestic air frying under certain cases and proposes possible mitigation measures.

Spatial distributions of particle number size distributions generated during cooking processes and the impacts of range hoods

Cooking oil fume (COF) is associated with an increased risk of health effects. The particle number size distribution (PNSD) of COF presenting as lognormal structures is recognized as a key metric in determining its exposure toxicities, but the information of its spatial distributions and impacting factors are still lacking. This study conducted real-time monitoring COF PNSD during the cooking processes in a kitchen laboratory. Results showed that COF PNSD presented as a combination of two lognormal distributions. The peak diameters of PNSD inside the kitchen were: 385 nm (very close to the source), 126 nm (5 cm above the source), 85 nm (10 cm above the source) to 36 nm (breath point, 50 cm above the source), 33 nm (sucking surface of the ventilation hood), 31 nm (1 m horizontally to the source), and 29 nm (3.5 m horizontally to the source). The reasons of this observation was the sharp decrease of temperature from the pot to the indoor environment reduced the surface partial pressure of the COF particles and caused a large amount of semi-volatile organic carbons (SVOCs) with lower saturation ratios condensed on the COF surface. With the temperature difference became insignificant with the distance further to the source, the reduction of the supersaturation helped the gasification of these SVOCs. Dispersion led to a linearly horizontal decreases ((1.85 ± 0.10) × 10⁶#/cm³/m) in particle numbers with further distances, making the peak particle number concentrations decrease from 3.5 × 10⁵#/cm³ at the breath point to 1.1 × 10⁵#/cm³ at the point 3.5 m to the source. Cooking dishes also presented as mode diameters of 22-32 nm at the breath point. The amount of edible oil used in different dishes is positively correlated with the peak concentration of COF. Only increasing the exhaust force of the range hood cannot significantly change the sucked COF particle numbers and sizes, owning to that COF particles are mainly small sizes. New technologies on cleaning small size particles and efficient supplemental air should be given more considerations.

Investigating aldehyde and ketone compounds produced from indoor cooking emissions and assessing their health risk to human beings

Aldehyde and ketone compounds are ubiquitous in the air and prone to adverse effects on human health. Cooking emission is one of the major indoor sources. Aiming to evaluate health risks associated with inhalation exposure to aldehyde and ketone compounds, 13 carbonyl compounds (CCs) released from heating 5 edible oils, 3 seasonings, and 2 dishes were investigated in a kitchen laboratory. For the scenarios of heating five types of oil, aldehydes accounted for 61.1%-78.0% of the total emission, mainly acetaldehyde, acrolein and hexanal. Comparatively, heating oil with added seasonings released greater concentrations of aldehyde and ketone compounds. The concentration enhancement of larger molecular aldehydes was significantly greater. The emission factors of aldehyde and ketone compounds for cooking the dish of chili fried meat were much greater compared to that of tomato fried eggs. Therefore, food materials also had a great impact on the aldehyde and ketone emissions. Acetone and acetaldehyde were the most abundant CCs in the kitchen. Acrolein concentrations ranged from 235.18 to 498.71 µg/m³, which was about 100 times greater compared to the guidelines provided by Office of Environmental Health Hazard Assessment (OEHHA). The acetaldehyde inhalation for adults was 856.83-1515.55 µg and 56.23-192.79 µg from exposure to chili fried meat and tomato fried eggs, respectively. This exceeds the reference value of 90 µg/day provided by OEHHA. The findings of this study provided scientific evidences for the roles of cooking emissions on indoor air quality and human health.

Formation pathways of aldehydes from heated cooking oils

Cooking emissions account for a major fraction of urban volatile organic compounds and organic aerosol. Aldehyde species, in particular, are important exposure hazards in indoor residential and occupational environments, and precursors to particulate matter and ozone formation in outdoor air. Formation pathways of aldehydes from oils that lead to their emissions are not well understood. In this work, we investigate the underlying mechanisms involved in the formation of aldehydes from heated cooking oil emissions, through studying how antioxidants and oil composition modulate oxidation chemistry. Our results demonstrate that gaseous emissions are driven by radical-mediated autoxidation reactions in cooking oil, and the composition of cooking oils strongly influences the reaction mechanisms. Antioxidants have a dual effect on aldehyde emissions depending on the rates of radical propagation reactions. We propose a mechanistic framework that can be used to understand and predict cooking emissions under different cooking conditions. Our results highlight the need to understand the rates and mechanisms of autoxidation and other reactions in cooking oils in order to accurately predict the gas- and particle-phase emissions from food cooking in urban atmospheres.

Size-fractionated ultrafine particles and their optical properties produced from heating edible oils in a kitchen laboratory

Cooking oil fume (COF) is an important source of indoor and outdoor air pollutants. COF generates a large number of organic compounds through volatilization and thermal oxidation, mainly including acids, alcohols, aldehydes and polycyclic aromatic hydrocarbons (PAHs), which can contribute 10 %-35 % to airborne organic particles in urban areas. COF not only affects human health owning to their small sizes, but also may absorb incident light due to the presence of brown carbon (BrC) chromophores in organic components. Therefore, we investigated size distributions and light absorption properties of particles produced from heating four types of edible oil. Results showed over 75 % of COF particles belonged to ultrafine particles (UFPs) and capable of absorbing light. The particle number size distributions for heating all edible oils were bimodal lognormal distribution, and the two mode diameters were within 27.9-32.2 nm and 187.7-299.6 nm. Both real-time monitoring and offline analyzing results show the average absorption coefficients of particles generated from heating soybean oil were much greater compare to those of heating other three edible oils. The mean AAE_370/520 for heating soybean oil, olive oil, corn oil and peanut oil were 1.877, 1.669, 1.745 and 1.288, respectively, indicating the presence of BrC chromophores. A large proportion of BrC identified by HPLC-DAD-Q-TOF-MS only contain carbon, hydrogen and oxygen, which are C_nH_2nO₂, C_nH_2n-2O₂, C_nH_2n-4O₂ and C_nH_2n-6O₂ (9 <n < 23), may belong to fatty acids. Their total light absorption at λ = 370 nm accounted for 16.75 %-54.56 % of the total absorption of methanol-soluble BrC. The findings provided scientific evidences for the significance of cooking emissions on ambient aerosol properties.

Enhanced commercial cooking inventories from the city scale through normalized emission factor dataset and big data

Cooking emission inventories always have poor spatial resolutions when applying with traditional methods, making their impacts on ambient air and human health remain obscure. In this study, we created a systematic dataset of cooking emission factors (CEFs) and applied it with a new data source, cooking-related point of interest (POI) data, to build up highly spatial resolved cooking emission inventories from the city scale. Averaged CEFs of six particulate and gaseous species (PM, OC, EC, NMHC, OVOCs, VOCs) were 5.92 ± 6.28, 4.10 ± 5.50, 0.05 ± 0.05, 22.54 ± 20.48, 1.56 ± 1.44, and 7.94 ± 6.27 g/h normalized in every cook stove, respectively. A three-field CEF index containing activity and emission factor species was created to identify and further build a connection with cooking-related POI data. A total of 95,034 cooking point sources were extracted from Beijing, as a study city. In downtown areas, four POI types were overlapped in the central part of the city and radiated into eight distinct directions from south to north. Estimated PM/VOC emissions caused by cooking activities in Beijing were 4.81/9.85 t per day. A 3D emission map showed an extremely unbalanced emission density in the Beijing region. Emission hotspots were seen in Central Business District (CBD), Sanlitun, and Wangjing in Chaoyang District and Willow and Zhongguancun in Haidian District. PM/VOC emissions could be as high as 16.6/42.0 kg/d in the searching radius of 2 km. For PM, the total emissions were 417.4, 389.0, 466.9, and 443.0 t between Q1 and Q4 2019 in Beijing, respectively. The proposed methodology is transferrable to other Chinese cities for deriving enhanced commercial cooking inventories and potentially highlighting the further importance of cooking emissions on air quality and human health.

Carbonyls from commercial, canteen and residential cooking activities as crucial components of VOC emissions in China

Cooking in China supply the large population with nutrition and, as a commercial activity, it also promotes the economic growth of Chinese society. The specific cooking styles in China can produce complex volatile organic compound (VOC) emissions. The resulting adverse effects on the environment and human health of carbonyls from cooking should not be ignored. We quantitatively evaluated the contribution of carbonyls to common VOCs (carbonyl/VOC ratio) from cooking activities in China through the establishment and comparison of the source profiles, emission factors (EFs), emission amount and ozone formation potential (OFP). It was found that carbonyls are crucial components of VOCs from commercial, canteen and residential cooking activities (COC, CAC and REC, respectively). The carbonyl/VOC ratio from cooking activities in China had EFs, emissions, and a total OFP of 22-65 %, 23-34 %, and 49-104 %, respectively. The high OFP was due to the high OFP emissions intensity (OFP_EI) and maximum incremental reactivity (MIR) values of carbonyls. This indicates that to alleviate O₃ pollution, OFP-based control measures that target carbonyls might be more efficient than measures that target common VOCs. Priority should be given to emission controlling COC emissions, specifically those from medium- and large-scale catering. Formaldehyde, acetaldehyde, and hexanal were the key carbonyl species that form O₃ in the environment. Our findings imply that cooking-emitted carbonyls should not be overlooked in investigations of O₃ formation and that these compounds should be subject to strict regulations.

A review of critical residential buildings parameters and activities when investigating indoor air quality and pollutants

Indoor air in residential dwellings can contain a variety of chemicals, sometimes present at concentrations or in combinations which can have a negative impact on human health. Indoor Air Quality (IAQ) surveys are often required to characterize human exposure or to investigate IAQ concerns and complaints. Such surveys should include sufficient contextual information to elucidate sources, pathways, and the magnitude of exposures. The aim of this review was to investigate and describe the parameters that affect IAQ in residential dwellings: building location, layout, and ventilation, finishing materials, occupant activities, and occupant demography. About 180 peer-reviewed articles, published from 01/2013 to 09/2021 (plus some important earlier publications), were reviewed. The importance of the building parameters largely depends on the study objectives and whether the focus is on a specific pollutant or to assess health risk. When considering classical pollutants such as particulate matter (PM) or volatile organic compounds (VOCs), the building parameters can have a significant impact on IAQ, and detailed information of these parameters needs to be reported in each study. Research gaps and suggestions for the future studies together with recommendation of where measurements should be done are also provided.

Recent advances on SOA formation in indoor air, fate and strategies for SOA characterization in indoor air - A review

Recent studies proves that indoor air chemistry differs in many aspects from atmospheric one. People send up to 90 % of their life indoors being exposed to pollutants present in gas, particle and solid phase. Particle phase indoor is composed of particles emitted from various sources, among which there is an indoor source - secondary chemical reactions leading to formation of secondary organic aerosol (SOA). Lately, researchers' attentions turned towards the ultrafine particles, for there are still a lot of gaps in knowledge concerning this field of study, while there is evidence of negative influence of ultrafine particles on human health. Presented review sums up current knowledge about secondary particle formation in indoor environment and development of analytical techniques applied to study those processes. The biggest concern today is studying ROS, for their lifetime in indoor air is very short due to reactions at the very beginning of terpene oxidation process. Another interesting aspect that is recently discovered is monoterpene autooxidation process that leads to HOMs formation that in turn can influence SOA formation yield. A complex studies covering gas phase and particle phase characterization, but also toxicological studies are crucial to fully understand indoor air chemistry leading to ultrafine particle formation.

α-Fe2O3 nanoparticles and hazardous air pollutants release during cooking using cast iron wok in a commercial Chinese restaurant

Long-term exposure to fine particles (PM_2.5), ultrafine particles (UFPs), and volatile organic compounds (VOCs) emissions from cooking has been linked to adverse human health effects. Here, we measured the real-time number size distribution of particles emitted when cooking two served food in Chinese restaurants and estimated the emission rate of UFPs and PM_2.5. Experiments were conducted under a control hood, and both online measurement and offline analysis of PM_2.5 were carried out. The measured emission rates of PM_2.5 generated from deep-frying and grilling were 0.68 ± 0.11 mg/min and 1.58 ± 0.25 mg/min, respectively. Moreover, the UFPs emission rate of deep-frying (4.3 × 10⁹ #/min) is three times higher than that of grilling (1.4 × 10⁹ #/min). Additionally, the PM_2.5 emission of deep-frying was comprised of a considerable amount of α-Fe₂O₃ (5.7% of PM_2.5 total mass), which is more toxic than other iron oxide species. A total of six carcinogenic HAPs were detected, among which formaldehyde, acrolein, and acetaldehyde were found to exceed the inhalation reference concentration (RfC) for both cooking methods. These findings can contribute to future evaluation of single particle and HAPs emission from cooking to better support toxicity assessment.

Gas- and Particle-Phase Amide Emissions from Cooking: Mechanisms and Air Quality Impacts

The high-temperature cooking of protein-rich foods represents an important but poorly constrained source of nitrogen-containing gases and particles to indoor and outdoor atmospheres. For example, panfrying meat may form and emit these nitrogen-containing compounds through complex chemistry occurring between heated proteins and cooking oils. Here, we simulate this cooking process by heating amino acids together with triglycerides. We explore their interactions across different temperatures, triglyceride types, and amino acid precursors to form amide-containing products. Ammonia, arising from the thermal degradation of amino acids, may react with a triglyceride's ester linkages, forming amides and promoting de-esterification reactions that break the triglyceride into volatilizable products. Additionally, triglycerides may thermally oxidize and fragment as they are heated, and the resulting oxygenated breakdown products may react with ammonia to form amides. We observed evidence for amide formation through both of these pathways, including gas-phase emissions of C_2-11H_5-23NO species, whose emission factors ranged from 33 to 813 μg total gas-phase amides per gram of amino acid precursor. Comparable quantities of particle-phase oleamide (C₁₈H₃₅NO) were emitted, ranging from 45 to 218 μg/g. The observed amide products had variable predicted toxicities, highlighting the importance of understanding their emissions from cooking and their ultimate inhalation exposure risks.

Formation of cluster mode particles (1-3 nm) in preschools

This study is the first study that reports the cluster particle (1-3 nm) formation (CPF) in two modern preschools located in Nur-Sultan city of Kazakhstan from October 28 to November 27, 2019. The average particle number concentration and mode diameter values during major CPF events in Preschool I and Preschool II were found to be 1.90 × 10⁶ (SD 6.43 × 10⁶) particles/cm³ and 1.60 (SD 0.85) nm, and 1.11 × 10⁹ (SD 5.46 × 10⁹) particles/cm³ and 2.16 (SD 1.47) nm, respectively. The ultraviolet PM concentration reached as high as 7 μg/m³ in one of the measurement days. The estimated emission rate in Preschool I for CPF events was 9.57 × 10⁹ (SD 1.92 × 10⁹) particles/min. For Preschool II, the emission rate was 7.25 × 10⁹ (SD 12.4 × 10⁹) particles/min. We identified primary cluster particles (CPs) emitted directly from the sources such as candle burning, and secondary CPs formed as a result of the oxidation of indoor VOCs or smoking VOCs. The secondary CPs are likely to be SOA. Indoor VOCs were mainly emitted during cleaning activities as well as during painting and gluing. Indoor VOCs are the controlling factors in the CPF events. Changes in the training and cleaning programs may result in significant reductions in the exposure of the children to CPs.

Nanoscopic Study of Water Uptake on Glass Surfaces with Organic Thin Films and Particles from Exposure to Indoor Cooking Activities: Comparison to Model Systems

Water uptake by thin organic films and organic particles on glass substrates at 80% relative humidity was investigated using atomic force microscopy-infrared (AFM-IR) spectroscopy. Glass surfaces exposed to kitchen cooking activities show a wide variability of coverages from organic particles and organic thin films. Water uptake, as measured by changes in the volume of the films and particles, was also quite variable. A comparison of glass surfaces exposed to kitchen activities to model systems shows that they can be largely represented by oxidized oleic acid and carboxylate groups on long and medium hydrocarbon chains (i.e., fatty acids). Overall, we demonstrate that organic particles and thin films that cover glass surfaces can take up water under indoor-relevant conditions but that the water content is not uniform. The spatial heterogeneity of the changes in these aged glass surfaces under dry (5%) and wet (80%) conditions is quite marked, highlighting the need for studies at the nano- and microscale.

Primary emissions and secondary production of organic aerosols from heated animal fats

Cooking is an important source of primary organic aerosol (POA) in urban areas, and it may also generate abundant non-methane organic gases (NMOGs), which form oxidized organic aerosol (OOA) after atmospheric oxidation. Edible fats play an important role in a balanced diet and are part of various types of cooking. We conducted laboratory studies to examine the primary emissions of POA and NMOGs and OOA formation using an oxidation flow reactor (OFR) for three animal fats (i.e., lard, beef and chicken fats) heated at two different temperatures (160 and 180 °C). Positive matrix factorization (PMF) revealed that OOA formed together with POA loss after photochemical aging, suggesting the conversion of some POA to OOA. The maximum OOA production rates (PRs) from heated animal fats, occurring under OH exposures (OHexp) of 8.3-15 × 10¹⁰ molecules cm^-3 s, ranged from 8.9 to 24.7 μg min^-1, 1.6-14.5 times as high as initial POA emission rates (ERs). NMOG emissions from heated animal fats were dominated by aldehydes, which contributed 14-71% of the observed OOA. We estimated that cooking-related OOA could contribute to as high as ~10% of total organic aerosol (OA) in an urban area in Hong Kong, where cooking OA (COA) dominated the POA. This study provides insights into the potential contribution of cooking to urban OOA, which might be especially pronounced when cooking contributions dominate the primary emissions.

Emission of volatile organic compounds during aerobic decomposition of banana peel

Emissions of volatile organic compounds (VOCs) were continuously measured during the aerobic decomposition of banana peel in a laboratory-scale landfill simulator over 25 d. Using direct membrane inlet single-photon ionisation time-of-flight mass spectrometry (MI-SPI-ToF-MS), 18 VOCs belonging to 10 functional groups were detected in the air samples, and their VOC emission profiles were established using cluster analysis on time-resolved data. Three emission stages were clearly identified, with the major release for most VOC compounds occurring during the first 14 d. The emission patterns of the individual compounds were quite similar despite the different release mechanisms. In addition, no apparent increase in temperature was observed inside the simulator during the entire experimental period. We suggest that the volatilisation of the constituents in the waste pile contributed equally to VOC emissions as did the degradation of banana peel via microbial activity. The average emission rate of total VOCs reached 44.3 × 10^-3 mg VOC kg^-1 of dry banana peel, with more than half belonging to malodourous substances. The malodourous emissions of the decaying banana peel in an aerobic environment mainly originated from styrene, dimethyl sulphide, and diethyl sulphide, the most common contributors to offensive odourants during food waste biodegradation.

Concluding remarks: Faraday Discussion on air quality in megacities

Megacities are metropolitan areas with populations over 10 million, and many of them are facing significant global environmental challenges such as air pollution. Intense economic and human activities in megacities result in air pollution emissions, inducing high levels of air pollutants in the atmosphere that harm human health, cause regional haze and acid deposition, damage crops, influence regional air quality, and contribute to climate change. Since the Great London Smog and the first recognized episode of Los Angeles photochemical smog seventy years ago, substantial progress has been achieved in improving the scientific understanding of air pollution and in developing emissions reduction technologies and control measures. However, much remains to be understood about the complex processes of atmospheric transport and reaction mechanisms; the formation and evolution of secondary particles, especially those containing organic species; and the influence of emerging emissions sources and changing climate on air quality and health. Molina (DOI: ) has provided an excellent overview of the sources of emissions in megacities, atmospheric physicochemical processes, air quality trends and management, and the impacts on health and climate for the introductory lecture of this Faraday Discussion.

Quantifying source contributions for indoor CO2 and gas pollutants based on the highly resolved sensor data

Household air pollution is the dominant contributor to population air pollutant exposure, but it is often of less concern compared with ambient air pollution. One of the major knowledge gaps in this field are detailed quantitative source contributions of indoor pollutants, especially for gaseous compounds. In this study, temporally, spatially, and vertically resolved monitoring for typical indoor gases including CO₂, CO, formaldehyde, methane, and the total volatile organic compounds (VOCs) was conducted to address pollution dynamics and major sources in an urban apartment. The indoor concentrations were significantly higher than the simultaneously measured outdoor concentrations. A new statistic approach was proposed to quantitatively estimate contributions of different sources. It was estimated that outdoor CO₂ contributed largely to the indoor CO₂, while main indoor sources were human metabolism and cooking. Outdoor infiltration and cooking contributed almost equally to the indoor CO. The contribution of outdoor infiltration to methane was much higher than that to formaldehyde. Cooking contributed to 24%, 19%, and 25% of indoor formaldehyde, methane, and VOCs, whereas the other unresolved indoor sources contributed 61%, 19%, and 35% of these pollutants, respectively. Vertical measurements showed that the uplifting of hot air masses led to relatively high concentrations of the pollutants in the upper layer of the kitchen and in the other rooms to a lesser extent.

Potential hazardous effects of printing room PM2.5 exposure include promotion of lung inflammation and subsequent injury

There have been few studies investigating the potential effects of indoor sources of particulate matter on human health. In this study, the effect of different concentrations of fine particulate matter (PM_2.5) collected from a printing room on lung health was examined using cultured cells and a mouse model. Further, the mechanism of lung injury was examined. The results indicated that PM_2.5 significantly enhanced malondialdehyde activity (P<0.05), decreased superoxide dismutase activity (P<0.05), upregulated the expression of pro-inflammatory factors including interleukin (IL)-1β, tumor necrosis factor-, IL-6 and downregulated the expression of the inflammatory factor IL-2 (P<0.05). Western blot analysis indicated that PM_2.5 significantly enhanced expression of phosphorylated (p)-ERK relative to total ERK, cyclooxygenase-2, p-anti-nuclear-factor-κB (p-NF-κB) relative to NF-κB, transforming growth factor-β1 and Bax relative to Bcl-2 in inflammation (P<0.05), fibrosis and apoptosis signaling pathways. Furthermore, the results revealed that exposure was associated with an increased abundance of pathogens including Burkholderiales, Coriobacteriia, and Betaproteobacteria in in the lungs. In conclusion, exposure to PM_2.5 from a printing room significantly increased inflammation, fibrosis, apoptosis and the abundance of pathogenic bacteria, indicating that exposure is potential threat to individuals who spend a significant amount of time in printing rooms.

The atmospheric chemistry of indoor environments

Through air inhalation, dust ingestion and dermal exposure, the indoor environment plays an important role in controlling human chemical exposure. Indoor emissions and chemistry can also have direct impacts on the quality of outdoor air. And so, it is important to have a strong fundamental knowledge of the chemical processes that occur in indoor environments. This review article summarizes our understanding of the indoor chemistry field. Using a molecular perspective, it addresses primarily the new advances that have occurred in the past decade or so and upon developments in our understanding of multiphase partitioning and reactions. A primary goal of the article is to contrast indoor chemistry to that which occurs outdoors, which we know to be a strongly gas-phase, oxidant-driven system in which substantial oxidative aging of gases and aerosol particles occurs. By contrast, indoor environments are dark, gas-phase oxidant concentrations are relatively low, and due to air exchange, only short times are available for reactive processing of gaseous and particle constituents. However, important gas-surface partitioning and reactive multiphase chemistry occur in the large surface reservoirs that prevail in all indoor environments. These interactions not only play a crucial role in controlling the composition of indoor surfaces but also the surrounding gases and aerosol particles, thus affecting human chemical exposure. There are rich research opportunities available if the advanced measurement and modeling tools of the outdoor atmospheric chemistry community continue to be brought indoors.

Quantification of the impact of cooking processes on indoor concentrations of volatile organic species and primary and secondary organic aerosols

Cooking is recognized as an important source of particulate pollution in indoor and outdoor environments. We conducted more than 100 individual experiments to characterize the particulate and non-methane organic gas emissions from various cooking processes, their reaction rates, and their secondary organic aerosol yields. We used this emission data to develop a box model, for simulating the cooking emission concentrations in a typical European home and the indoor gas-phase reactions leading to secondary organic aerosol production. Our results suggest that about half of the indoor primary organic aerosol emission rates can be explained by cooking. Emission rates of larger and unsaturated aldehydes likely are dominated by cooking while the emission rates of terpenes are negligible. We found that cooking dominates the particulate and gas-phase air pollution in non-smoking European households exceeding 1000 μg m-3 . While frying processes are the main driver of aldehyde emissions, terpenes are mostly emitted due to the use of condiments. The secondary aerosol production is negligible with around 2 μg m-3 . Our results further show that ambient cooking organic aerosol concentrations can only be explained by super-polluters like restaurants. The model offers a comprehensive framework for identifying the main parameters controlling indoor gas- and particle-phase concentrations.

Solar light induced transformation mechanism of allyl alcohol to monocarbonyl and dicarbonyl compounds on different TiO2: A combined experimental and theoretical investigation

Enols are an important group of photochemical precursors of atmospheric carbonyl compounds. However, the transformation mechanism is not fully understood. In this study, the photo-induced transformation of a typical enol, allyl alcohol, to carbonyl compounds on TiO₂ (P25) and aluminum reduced TiO₂ (P25, rutile and anatase TiO₂) were investigated. Intermediate results confirmed that a total of seven carbonyl compounds, including four monocarbonyl compounds (acetone, glycolaldehyde, 1,3-dihydroxyacetone and acrolein) and three dicarbonyl compounds (glyoxal, methylglyoxal and dimethylglyoxal), were formed on studied TiO₂. This is the first time to report the transformation of allyl alcohol to dicarbonyl compounds on TiO₂. The same byproducts formation indicated negligible effects of reduction treatment and crystal phase to the composition of carbonyl intermediates. However, the relative content ratio of dicarbonyl compounds to monocarbonyl ones on reduced P25 is ca. 4.1 times higher than that on P25, suggesting reduction treatment significantly accelerated the transformation of allyl alcohol or monocarbonyl compounds to dicarbonyl ones. Furthermore, both rutile and anatase crystal phases were found beneficial for the dicarbonyl compounds generation within enough reaction time, especially for anatase. The enhanced ^•OH was responsible for all accelerations. Furthermore, the intermediate results together with quantum chemical calculations confirmed that ^•OH addition and O₂ oxidation preferred converting allyl alcohol to dicarbonyl compounds rather than monocarbonyl ones. The present work could provide a deep insight into the transformation of allyl alcohol to carbonyl compounds, and efficiently replenish atmospheric transformation fate of enols.

Characteristics of cooking-generated PM10 and PM2.5 in residential buildings with different cooking and ventilation types

The fine particles (PM_2.5, PM₁₀) have worsened indoor air quality and have caused an adverse effect on health. While range hoods have been typically used to exhaust cooking-generated fine particles in residential buildings, it is difficult to remove the fine particles effectively. The present study analyzed the effect of cooking on indoor air quality through the on-site measurements of cooking-generated fine particles (PM_2.5 and PM₁₀) in 30 residential buildings. The results of the field measurement showed that the fine particles occurred during the cooking and the concentration exceeded the Korean indoor fine particle concentration standards for PM₁₀ and PM_2.5. The particle decay rate constant in field measurement was 1.27-21.83 h^-1. The emission rates were 0.39-20.45 mg/min. In addition, the fine particles were measured in the experimental building by varying the cooking methods and ventilation types. Four different cooking methods were selected including broiling fish, meat, frying egg, and meat. By operating the range, hood system and the natural ventilation, the dispersion of the fine particle concentration, the particle emission rate, decay rate constant, and the Living-Kitchen (L/K) Ratio change was evaluated quantitatively. Based on the obtained results, the maximum concentrations of the fine particles were measured when broiling fish. Moreover, the range hood system was not able to decrease the cooking-emitted particle concentration effectively during the cooking period. The cooking-emitted particles were removed rapidly when both natural ventilation and the range hood system were operated simultaneously, where the particle decay rate constant was approximately 9 h^-1. Furthermore, the selection of cooking type was the most important factor that can significantly have an impact on indoor particle concentrations. Cooking - generated particles; Range hood; Particle decay rate constant; Living-Kitchen (L/K); PM2.5; Emission rate.

Secondary Organic Aerosol Formation from Urban Roadside Air in Hong Kong

Motor vehicle emissions are an important but poorly constrained source of secondary organic aerosol (SOA). Here, we investigated in situ SOA formation from urban roadside air in Hong Kong during winter time using an oxidation flow reactor (OFR), with equivalent atmospheric oxidation ranging from several hours to several days. The campaign-average mass enhancement of OA, nitrate, sulfate, and ammonium upon OFR aging was 7.0, 7.2, 0.8, and 2.6 μg m^-3, respectively. To investigate the sources of SOA formation potential, we performed multilinear regression analysis between measured peak SOA concentrations from OFR and the concentrations of toluene that represent motor vehicle emissions and cooking OA from positive matrix factorization (PMF) analysis of ambient OA. Traffic-related SOA precursors contributed 92.3%, 92.4%, and 83.1% to the total SOA formation potential during morning rush hours, noon and early afternoon, and evening meal time, respectively. The SOA production factor (PF) was approximately 5.2 times of primary OA (POA) emission factor (EF) and the secondary particulate matter (PM) PF was approximately 2.6 times of primary particles EF. This study highlights the potential benefit of reducing secondary PM production from motor vehicle emissions in mitigating PM pollutions.

The emission of PM2.5 in respiratory zone from Chinese family cooking and its health effect

To investigate the PM_2.5 emission in the direct exposed area from Chinese family cooking, eleven kinds of Chinese ordinary family cooking dishes were designed including frying, quick-frying, stewing, deep-frying, boiling and steaming according to the results of questionnaire survey. The results showed that the intensity sequence for PM_2.5 emissions decreased as follows in general: deep-frying (0.709-2.731 mg/m³) > stir-frying (0.700-0.958 mg/m³) > stewing (~0.573 mg/m³) > quick-frying (0.140-0.433 mg/m³) > boiling (0.004-0.247 mg/m³) > steaming (0.011-0.088 mg/m³), most of them exceeded the national indoor air standard. The average concentration of PM_2.5 in the direct respiratory zone from family cooking was determined to be 0.599 mg/m³, which was about 8 times higher than the national indoor air standard of China and lower than that from commercial restaurants. The annual PM_2.5 inhalation exposure in the direct exposed area from family cooking for male and female was 346.30 mg/year and 309.59 mg/year, respectively. Although the annual PM_2.5 inhalation exposure of male operators in general ordinary family cooking was about 11.8% higher than that of females, the pregnant women, children and the elderly are not encouraged to prepare ordinary family cooking for a long time due to their sensitive to PM_2.5 emission. Selecting ventilator with high wind speed can reduce PM_2.5 emission more than 65% when compared to medium wind speed. Improvement of ventilator wind speed is considered to be an effect way to reduce PM_2.5 emission for cooking.

Insights into the characteristics and sources of primary and secondary organic carbon: High time resolution observation in urban Shanghai

There is growing evidence suggesting that organic aerosols play an important role in the evolution of severe haze episodes. However, long-term investigations of the different characteristics of carbonaceous aerosols during haze and non-haze days are insufficient. In this work, hourly measurements of organic carbon (OC) and elemental carbon (EC) in PM_2.5 were conducted in Shanghai, a megacity in Eastern China, over the course of a year from July 2013 to June 2014. Both OC and EC exhibited a bimodal diel pattern and were highly dependent on the wind speed and direction. The concentration-weighted trajectory (CWT) analysis illustrated that primary OC (POC) and EC were largely associated with regional and long-range transport. Secondary OC (SOC) formation was the strongest during the harvest season owing to significant biomass burning emissions from the adjacent Yangtze River Delta and farther agricultural regions. Compared to OC (6.7 μg m^-3) and EC (2.0 μg m^-3) in the non-haze days, higher levels of both OC (15.6 μg m^-3) and EC (7.7 μg m^-3) were observed in the haze days as expected, but with lower OC/EC ratios in the haze days (2.4) than in non-haze days (4.6). The proportion of POC and EC in PM_2.5 remained relatively constant as a function of PM_2.5 mass loadings, while that of SOC significantly decreased on the highly polluted days. It is concluded that the haze pollution in urban Shanghai was influenced more by the primary emissions (POC and EC), while the role of SOC in triggering haze was limited.