Formaldehyde in the indoor environment

One-Pot Method to Synthesize Silver Nanoparticle-Modified Bamboo-Based Carbon Aerogels for Formaldehyde Removal

The present study demonstrated a freeze-drying-carbonization method to synthesize silver nanoparticle-modified bamboo-based carbon aerogels to remove formaldehyde. The bamboo-based carbon aerogel (BCA) has the advantages of controllable pore size and rich oxygen-containing groups, which can provide a good foundation for surface modification. BCA can greatly enhance the purification of formaldehyde by loading silver nanoparticles. The maximum adsorption capacity of 5% Ag/BCA for formaldehyde reached 42 mg/g under 25 ppm formaldehyde concentration, which is 5.25 times more than that of BCA. The relevant data were fitted by the Langmuir model and the pseudo 2nd-order model and good results were obtained, indicating that chemical absorption occurred between the carbonyl of formaldehyde and the hydroxyl of BCA. Therefore, silver nanoparticle-modified bamboo-based carbon aerogels play a positive role in the selective removal of formaldehyde. Silver nanoparticles promoted the activation of oxygen and strengthened the effect of BCA on HCHO adsorption.

A Study on the Measurement of Unregulated Pollutants in Korean Residential Environments

This study investigated the pollution caused by unregulated chemical substances in Korean residential environments. A TA tube was used for indoor air collection, and Gas Chromatography–Mass Spectrometry was used for the analysis of chemical substances. According to the results of this study, 13 substances out of the 16 analyzed chemicals were detected and, among them, the concentrations of phenol, α-pinene, and limonene within the indoor air were high. The average concentration of phenol was 32.7 µg/m3. α-pinene and limonene were detected, of which the highest concentrations were as 598.2 µg/m3 and 652.5 µg/m3, respectively. The maximum concentrations of these three substances exceeded the levels of the lowest concentration of interest. Notably, α-pinene and limonene were released from the wood itself. Wood has been widely used indoors as a natural building material and as furniture. Therefore, it was considered that this was the reason for the high the concentrations of the two substances in indoor air. However, we do not argue that the usage of wood should be reduced because of the results obtained in this study. Instead, we sµggest that it is important to reduce the emissions of α-pinene and limonene throµgh the processing of the wood, extending its drying period, and determining the most appropriate time of use.

Validation of two contrasting capturing mechanisms for gaseous formaldehyde between two different types of strong metal-organic framework adsorbents

In this research, the adsorption behavior of formaldehyde (FA) onto two types of metal-organic frameworks (MOFs: MOF-199 [M199] and UiO-66-NH₂ [U6N]) is investigated against changes in the key process variables (e.g., FA partial pressure (0.5-10 Pa), temperature (30-120 °C), and relative humidity (RH: 0%, 50%, and 100%)). The results revealed that the FA adsorption behavior onto both MOFs is exothermic in nature. Besides, their relative dominance for FA uptake varies interactively with the changes in RH and FA partial pressure levels. As the FA levels increase in dry conditions, their breakthrough volumes (BTV (100% BT)) exhibit contrasting trends: The values of U6N decreased noticeably from 5232 and 3792 L·atm·g^-1, while those of M199 increased from 4152 to 5772 L·atm·g^-1. The superiority of U6N over M199 in the lower FA level (at<5 Pa) is supported by the Lewis acid-base interactions with amine groups (U6N) in line with kinetic/isotherm studies. Such superiority is also persistent at higher (10 Pa) FA level under all humid conditions in line with its higher moisture stability. However, in dry conditions, the reversal of relative dominance in which M199 exhibits enhanced efficacy for 10 Pa FA uptake (relative to U6N) should reflect its breathing effects with the potent role of pore-diffusion mechanism. This study offers valuable insights into the construction of tunable adsorbents with enhanced adsorptivity toward key targets.

From small molecules to polymeric probes: recent advancements of formaldehyde sensors

Formaldehyde is a well-known industrial material regularly used in fishery, vegetable markets, and fruit shops for maintaining their freshness. But due to its carcinogenic nature and other toxic effects, it is very important to detect it in very low concentrations. In recent years, amine-containing fluorescent probes have gained significant attention for designing formaldehyde sensors. However, the major drawbacks of these small molecular probes are low sensitivity and long exposure time, which limits their real-life applications. In this regard, polymeric probes have gained significant attention to overcome the aforementioned problems. Several polymeric probes have been utilized as a coating material, nanoparticle, quartz crystal microbalance (QCM), etc., for the selective and sensitive detection of formaldehyde. The main objective of this review article is to comprehensively describe the recent advancements in formaldehyde sensors based on small molecules and polymers, and their successful applications in various fields, especially in situ formaldehyde sensing in biological systems.

Thermal Insulation Mattresses Based on Textile Waste and Recycled Plastic Waste Fibres, Integrating Natural Fibres of Vegetable or Animal Origin

The current context provides, worldwide, the need to identify solutions for the thermal efficiency of constructions, through sustainable and innovative methods and products. A viable solution is to produce thermal insulating products by carding-folding technology, using natural fibres and recycled polyethylene terephthalate (rPET) and polyester (rPES) waste, converted to fibres. This paper presents experimental results obtained after testing several thermal insulation composite products produced using a mix of sheep wool, cellulose, rPET and rPES fibres. The results of the research demonstrate the thermal insulation properties but, at the same time, identify the benefits of using such materials on the quality of the air in the interior space (the ability to adjust humidity and reduce the concentration of harmful substances). At the same time, the advantages of using sheep wool composite mattresses concerning their resistance to insect attack is demonstrated when compared with ordinary thermal insulation materials. Finally, sensitivity elements of these composites are observed in terms of sensitivity to mould, and to contact with water or soil, drawing future research directions in the development of this type of materials.

Formaldehyde, acrolein and other carbonyls in dwellings of university students. Levels and source characterization

Fifteen carbonyl compounds were investigated in the living rooms and bedrooms of 25 university student flats in the urban area of Ciudad Real (Central Southern Spain) in wintertime. Carbonyls were sampled using Radiello ® passive samplers refilled in the laboratory according to the method described in ISO 16000-3 Standard. The most abundant carbonyls in the living rooms and bedrooms were formaldehyde, acetone, acetaldehyde, hexaldehyde and butyraldehyde. The median concentration levels in the living rooms and bedrooms were: 28.6 and 34.2 μg m^-3 for formaldehyde, 18.3 and 23.1 μg m^-3 for acetone, 14.3 and 15.8 μg m^-3 for acetaldehyde, 11.4 and 14.1 μg m^-3 for hexaldehyde and 10.8 and 12.4 μg m^-3 for butyraldehyde. The median concentration of formaldehyde, benzaldehyde, valeraldehyde and hexaldehyde was significantly higher in the bedrooms than in the living rooms. Indoor concentrations were significantly higher than outdoor concentrations for all carbonyl measured, indicating that sources in the indoor environment are prevailing in all flats. Principal component analysis, multiple linear regressions and Spearman correlation coefficients were used to investigate the origin, the indoor pollutants determinants and to establish common sources between carbonyls. Eight components were extracted from the application of PCA to the indoor and outdoor measurements accounting for 97.7% of the total variance. Formaldehyde, acetone, acetaldehyde and acrolein presented different indoor sources. In the multiple linear regression analysis, higher formaldehyde concentrations were found in those living rooms with wood floor and smoking was positively associated to acetone, propionaldehyde, benzaldehyde and isovaleraldehyde. Formaldehyde, acetaldehyde, acrolein, acetone, propionaldehyde and benzaldehyde concentrations were compared with relevant international guidelines, being their concentrations below recommended values except acrolein, where all measured flats exceeded the reference levels; it would be important to focus on the characterization of emission sources of acrolein in indoor air in order to minimise the exposure and health risk.

A Simple Preparation Method of Graphene and TiO2 Loaded Activated Carbon Fiber and Its Application for Indoor Formaldehyde Degradation

Formaldehyde has a significant impact on human health. This study used a simple dipping method to load graphene-titanium dioxide (GR-TiO2) on activated carbon fibers (ACFs). The microstructure of GR-TiO2/ACF hybrid material was observed by SEM, combined with XRD and BET analysis. The result showed that the GR-TiO2/ACF hybrid material had a specific surface area of 893.08 m2/g and average pore size of 2.35 nm. The formaldehyde degradation efficiency of the prepared material was tested under different conditions, such as ultraviolet (UV) radiation, air supply volume, relative humidity, initial mass concentration. The results showed that the UV radiation intensity, airflow and the initial mass concentration were positively correlated with the formaldehyde removal rate, and the relative humidity was negatively correlated with the formaldehyde removal rate. The GR-TiO2/ACF hybrid material had a maximum formaldehyde removal rate of 85.54% within 120 min.

How to predict emissions of volatile organic compounds from solid building materials? A critical review on mass transfer models

Volatile organic compounds (VOCs) emitting from solid building materials can cause adverse human health and environmental climate effects. It's more cost effective and powerful for mass-transfer emission models to describe the emission characteristic of VOCs than emission chamber studies. In this review, the existing main physical mechanism-based models for predicting VOCs emissions from dry solid building materials have been discussed, as well as their differences and similarities. Ignoring internal diffusion and porosity of solid materials, single-phase model is generally quite safe for use in actual condition. Conversely, porous media model is good for understanding VOC-transfer principles in porous materials. Additionally, the porous media model and the single-phase model can be transformed mutually because their model parameters are correlative. The availability of emission models is largely determined by the reliable and useful model parameters. Therefore, substantial technologies and novel methods have been developed for parameter estimation, which have also been reviewed in this paper. How to readily and rapidly obtain model parameters is a future development direction. In addition, applying emission models to predict and control VOCs emission from other solid waste materials is another future research prospect.

Indoor air quality impacts of residential mechanical ventilation system retrofits in existing homes in Chicago, IL

Mechanical ventilation systems are used in residences to introduce ventilation air and dilute indoor-generated pollutants. A variety of ventilation system types can be used in home retrofits, influencing indoor air quality (IAQ) in different ways. Here we describe the Breathe Easy Project, a >2-year longitudinal, pseudo-randomized, crossover study designed to assess IAQ and adult asthma outcomes before and after installing residential mechanical ventilation systems in 40 existing homes in Chicago, IL. Each home received one of three types of ventilation systems: continuous exhaust-only, intermittent powered central-fan-integrated-supply (CFIS), or continuous balanced system with an energy recovery ventilator (ERV). Homes with central heating and/or cooling systems also received MERV 10 filter replacements. Approximately weeklong field measurements were conducted at each home on a quarterly basis throughout the study to monitor environmental conditions, ventilation operation, and indoor and outdoor pollutants, including size-resolved particles (0.3-10 μm), ozone (O₃), nitrogen dioxide (NO₂), carbon dioxide (CO₂), carbon monoxide (CO), and indoor formaldehyde (HCHO). Mean reductions in indoor/outdoor (I/O) ratios across all systems after the intervention were approximately 12% (p = 0.001), 10% (p = 0.008), 42% (p < 0.001), 39% (p = 0.002), and 33% (p = 0.007), for CO₂, NO₂, and estimated PM₁, PM_2.5, and PM₁₀, respectively. There was a reduction in I/O ratios for all measured constituents with each type of system, on average, but with varying magnitude and levels of statistical significance. The magnitudes of mean differences in I/O pollutant concentrations ratios were generally largest for most pollutants in the homes that received continuous balanced with ERV and smallest in the homes that received intermittent CFIS systems, with apparent benefits to providing ventilation continuously rather than intermittently. All ventilation system types maintained similar indoor temperatures during pre- and post-intervention periods.

Au25 Nanoclusters Incorporating Three-Dimensionally Ordered Macroporous In2O3 for Highly Sensitive and Selective Formaldehyde Sensing

Detection of formaldehyde (FA) in the atmosphere is of significant importance because exposure to FA may cause serious health problems such as sick-house syndrome, leukemia, and cancer. Modifying metal oxide semiconductors (MOSs) with noble metal nanoparticles (NPs) is an efficient method to enhance FA-sensing properties. Herein, a series of Au₂₅ nanocluster (NC)-decorated three-dimensionally ordered macroporous In₂O₃ materials (Au₂₅/3DOM In₂O₃) is created, and the loading amount of Au₂₅ NCs was optimized based on FA responses. To reveal the effect of gold size on FA responses, we constructed Au₁₄₄ NC-loaded 3DOM In₂O₃ and Au NP (2.9 nm)-modified 3DOM In₂O₃ and compared their gas-sensing properties with the optimal Au₂₅/3DOM In₂O₃. The results show that in comparison with its counterparts, the optimal Au₂₅/3DOM In₂O₃ presents higher sensitivity, shorter response/recovery times, better selectivity, and excellent reproducibility. More attractively, the responses to FA are dependent on the size of Au particles loaded on In₂O₃. We suggest that the enhanced FA responses for the optimal material are mainly attributed to the electronic and chemical-sensitization effects of Au₂₅ NCs, and the size-dependent effect of FA responses is ascribed to the size of Au NPs affecting the formation of oxygen-adsorbing species. This work provides an efficient way for fabricating noble metal NP-loaded MOSs with tunable gas-sensing properties.

Study on the Effect of an Intermittent Ventilation Strategy on Controlling Formaldehyde Concentrations in Office Rooms

Material emission and ventilation are two aspects influencing indoor air quality. In this study, a model predictive control (MPC) strategy is proposed for intermittent ventilation system in office buildings, to achieve a healthy indoor environment. The strategy is based on a dynamic model for predicting emissions of volatile organic compounds (VOCs) from materials. The key parameters of formaldehyde from panel furniture in the model are obtained by an improved C-history method and large-scale chamber experiments. The effectiveness of the determined key parameters is validated, which are then used to predict the formaldehyde concentration variation and the pre-ventilation time in a typical office room. In addition, the influence of some main factors (i.e., vacant time, loading ratio, air change rate) on the pre-ventilation time is analyzed. Results indicate that the pre-ventilation time of the intermittent ventilation system ranges from several minutes to several hours. The pre-ventilation time decreases exponentially with the increase in the vacant time, the air change rate, and with the decrease in the loading ratio. When the loading ratio of the furniture is 0.30 m2/m3 and the vacant time is 100 days, the required pre-ventilation time approaches zero. Results further reveal that an air change rate of 2 h−1 is the most effective means for rapid removal of indoor formaldehyde for the cases studied. The proposed strategy should be helpful for achieving effective indoor pollution control.

Synergy of surface sodium and hydroxyl on NaTi2HO5 nanotubes accelerating the Pt-dominated ambient HCHO oxidation

Surface hydroxyl is widely perceived as conducive to HCHO degradation. Here, a kind of sodium titanate with interlayered hydroxyls (NaTi₂HO₅) was prepared to study the action conditions of surface hydroxyls in HCHO oxidation. The nanotubes mainly exposing (001) and nanobelts mainly exposing (100) are synthesized as the two morphologies of NaTi₂HO₅. We found the (001) facet is much more favored to HCHO adsorption via HRTEM and XPS analysis. The DFT calculations prove that the synergy of surface hydroxyl and Na atom is perfect for HCHO chemisorption. By this means NaTi₂HO₅ nanotubes can partially oxidize HCHO into formate and release very few CO, measured by in situ DRIFTS. Dominated by Pt nanoparticles, the complete oxidation of HCHO can be performed on NaTi₂HO₅ nanotubes with enhanced early reaction speed. Rather than simple surface hydroxyl, the effective synergy of hydroxyl and positive ion is proposed as an advantage for HCHO oxidation.

Acid pretreatment of support promotes Pd/SiO2 activity for formaldehyde oxidation at room temperature

Hydroxyl groups on SiO2 produced by acid pretreatment favored the anchoring of Pd particles and increased their dispersion, which induced more oxygen vacancies on the surface of catalysts and further enhanced H2O activation.

N-Coordinated Ir single atoms anchored on carbon octahedrons for catalytic oxidation of formaldehyde under ambient conditions

N-Coordinated Ir single atoms using N-doped carbon as a non-oxide support for formaldehyde removal under ambient conditions for the first time.

Residential building materials: An important source of ambient formaldehyde in mainland China

This study investigates the contribution of formaldehyde from residential building materials to ambient air in mainland China. Based on 265 indoor field tests in 9 provinces, we estimate that indoor residential sources are responsible for 6.66% of the total anthropogenic formaldehyde in China's ambient air (range for 31 provinces: 1.88-18.79%). Residential building materials rank 6th among 81 anthropogenic sources (range: 2nd-10th for 31 provinces). Emission intensities show large spatial variability between and within regions due to different residential densities, emission characteristics of building materials, and indoor thermal conditions. Our findings indicate that formaldehyde from the indoor environment is a significant source of ambient formaldehyde, especially in urban areas. This study will help to more accurately evaluate exposure to ambient formaldehyde and its related pollutants, and will assist in formulating policies to protect air quality and public health.

Formaldehyde, aliphatic aldehydes (C2 -C11 ), furfural, and benzaldehyde in the residential indoor air of children and adolescents during the German Environmental Survey 2014-2017 (GerES V)

Indoor air concentrations of formaldehyde, furfural, benzaldehyde, and 11 aliphatic aldehydes (C₂ -C₁₁ ) were measured in residences of 639 participants in the German Environmental Survey for Children and Adolescents 2014-2017 (GerES V). Sampling was conducted using passive samplers over periods of approximately seven days for each participant. The most abundant compounds were formaldehyde and hexanal with median concentrations of 24.9 µg m^-3 and 10.9 µg m^-3 , respectively. Formaldehyde concentrations exceeded the Guide Value I recommended by the German Committee on Indoor Guide Values (Ausschuss für Innenraumrichtwerte - AIR) (0.10 mg m^-3 ) for 0.3% of the participating residences. The sum of aliphatic n-aldehydes between C₄ (butanal) and C₁₁ (undecanal) exceeded their Guide Value (0.10 mg m^-3 ) for 2.0% of the residences. The geometric mean concentrations of most aldehydes were lower than in the earlier GerES IV (2003-2006) study. Formaldehyde and hexanal concentrations, however, were comparable in both studies and showed no significant difference. Indoor aldehyde concentrations did not exhibit significant correlations with factors collected in questionnaires, such as the age of the participants, their socio-economic status, the location of the residence (former East/West Germany), migration background, tobacco exposure, and the type of furniture used. The validity of the passive sampler measurements was verified against active sampling techniques in a test chamber experiment.

Acid-Catalyzed Isomerization of Carbonyls-2,4- dinitrophenylhydrazone in Mainstream Smoke of Heat-Not-Burn Tobacco Product for HPLC Analysis

Carbonyls (such as acrolein, acetaldehyde, and formaldehyde) are the critical type of carcinogens and toxicants contained within the heat-not-burn (HNB) tobacco products. Using HNB products can have negative effects on human health; therefore, it is important to measure carbonyl contents within the HNB mainstream smoke. Typically, the 2,4-dinitrophenylhydrazine (DNPH) approach involves forming the 2,4-dinitrophenylhydrazone derivatives, which is the most extensively adopted approach to qualitatively and quantitatively analyze carbonyl compounds. However, the approach can result in analytical error because 2,4-dinitrophenylhydrazones contains the E-stereoisomer as well as the Z-stereoisomer. Only an E-isomers exists in the purified carbonyls-2,4-dinitrophenylhydrazone, but when acid is added, the E-isomer and Z-isomer can be observed. For propionaldehyde-, acetaldehyde-, crotonaldehyde-, acrolein-, and 2-butanone-2,4-dinitrophenylhydrazones, their equilibrium Z/E isomer ratios are 0.143, 0.309, 0.093, 0.028, and 0.154. In the case of adding trace water into hydrazone derivatives dissolved within the acetonitrile solution, the derivative contents decrease, whereas the free DNPH content increases. Therefore, catalytic acid should be added in the low content. To determine carbonyls-2,4-dinitrophenylhydrazones through HPLC, the optimal approach is adding phosphoric acid into the samples and the standard reference solution to form the 0.02–1.0% acid solution.

Solvent-free synthesis of a formaldehyde-free benzoxazine monomer: study of its curing acceleration effect for commercial benzoxazine

A new 2-substituted benzoxazine bearing a phenol was blended with commercial benzoxazine for improving curing and thermomechanical properties.

Research Progress of Wood-Based Panels Made of Thermoplastics as Wood Adhesives

When thermoplastic resins such as polyethylene (PE) and polypropylene (PP) are selected as wood adhesives to bond wood particles (fibers, chips, veneers) by using the hot-pressing technique, the formaldehyde emission issue that has long existed in the wood-based panel industry can be effectively solved. In this study, in general, thermoplastic-bonded wood-based panels presented relatively higher mechanical properties and better water resistance and machinability than the conventional urea-formaldehyde resin-bonded wood-based panels. However, the bonding structure of the wood and thermoplastic materials was unstable at high temperatures. Compared with the wood-plastic composites manufactured by the extruding or injection molding methods, thermoplastic-bonded wood-based panels have the advantages of larger size, a wider raw material range and higher production efficiency. The processing technology, bonding mechanism and the performance of thermoplastic-bonded wood-based panels are comprehensively summarized and reviewed in this paper. Meanwhile, the existing problems of this new kind of panel and their future development trends are also highlighted, which can provide the wood industry with foundations and guidelines for using thermoplastics as environmentally friendly adhesives and effectively solving indoor pollution problems.

A ratiometric ESIPT probe based on 2-aza-Cope rearrangement for rapid and selective detection of formaldehyde in living cells

Formaldehyde (FA) is a crucial reactive signaling molecule participating in epigenetic and metabolic pathways. However, abnormally elevated levels of FA are implicated in various diseases spanning from tumors to neurodegenerative disorders. Despite being highly selective for FA, current 2-aza-Cope-based fluorescent probes leave room for improvement because their relatively slow reaction kinetics (1-9 hours response time) hinder their capability to track transient biological FA. Herein, we present a ratiometric fluorescent probe, FormAFP, based on excited state intramolecular photon transfer (ESIPT) for rapid (within 10 min), selective (above 70-fold over other RCS) and sensitive (240-times fluorescence enhancement with 66 nM detection limit) detection of FA via 2-aza-Cope rearrangement. The probe also displayed a fast response (<20 min) to both exogenous and endogenous FA in living cells. Besides, FormAFP was capable of monitoring FA released by folate degradation in living MCF7 cells. More importantly, FormAFP successfully detected fluctuations of endogenous FA levels in oxidative stress stimulation, demonstrating its potential as an ideal tool to explore FA biology.

Recent Advances on the Development of Protein-Based Adhesives for Wood Composite Materials-A Review

The industrial market depends intensely on wood-based composites for buildings, furniture, and construction, involving significant developments in wood glues since 80% of wood-based products use adhesives. Although biobased glues have been used for many years, notably proteins, they were replaced by synthetic ones at the beginning of the 20th century, mainly due to their better moisture resistance. Currently, most wood adhesives are based on petroleum-derived products, especially formaldehyde resins commonly used in the particleboard industry due to their high adhesive performance. However, formaldehyde has been subjected to strong regulation, and projections aim for further restrictions within wood-based panels from the European market, due to its harmful emissions. From this perspective, concerns about environmental footprint and the toxicity of these formulations have prompted researchers to re-investigate the utilization of biobased materials to formulate safer alternatives. In this regard, proteins have sparked a new and growing interest in the potential development of industrial adhesives for wood due to their advantages, such as lower toxicity, renewable sourcing, and reduced environmental footprint. This work presents the recent developments in the use of proteins to formulate new wood adhesives. Herein, it includes the historical development of wood adhesives, adhesion mechanism, and the current hotspots and recent progress of potential proteinaceous feedstock resources for adhesive preparation.

NHC-CDI Betaine Adducts and Their Cationic Derivatives as Catalyst Precursors for Dichloromethane Valorization

Zwitterionic adducts of N-heterocyclic carbene and carbodiimide (NHC-CDI) are an emerging class of organic compounds with promising properties for applications in various fields. Herein, we report the use of the ICyCDI(p-Tol) betaine adduct (1a) and its cationic derivatives 2a and 3a as catalyst precursors for the dichloromethane valorization via transformation into high added value products CH₂Z₂ (Z = OR, SR or NR₂). This process implies selective chloride substitution of dichloromethane by a range of nucleophiles Na⁺Z^– (preformed or generated in situ from HZ and an inorganic base) to yield formaldehyde-derived acetals, dithioacetals, or aminals with full selectivity. The reactions are conducted in a multigram-scale under very mild conditions, using dichloromethane both as a reagent and solvent, and very low catalyst loading (0.01 mol %). The CH₂Z₂ derivatives were isolated in quantitative yields after filtration and evaporation, which facilitates recycling the dichloromethane excess. Mechanistic studies for the synthesis of methylal CH₂(OMe)₂ rule out organocatalysis as being responsible for the CH₂ transfer, and a phase-transfer catalysis mechanism is proposed instead. Furthermore, we observed that 1a and 2a react with NaOMe to form unusual isoureate ethers, which are the actual phase-transfer catalysts, with a strong preference for sodium over other alkali metal nucleophiles.

Photocatalytic Air Purification Using Functional Polymeric Carbon Nitrides

The techniques for the production of the environment have received attention because of the increasing air pollution, which results in a negative impact on the living environment of mankind. Over the decades, burgeoning interest in polymeric carbon nitride (PCN) based photocatalysts for heterogeneous catalysis of air pollutants has been witnessed, which is improved by harvesting visible light, layered/defective structures, functional groups, suitable/adjustable band positions, and existing Lewis basic sites. PCN-based photocatalytic air purification can reduce the negative impacts of the emission of air pollutants and convert the undesirable and harmful materials into value-added or nontoxic, or low-toxic chemicals. However, based on previous reports, the systematic summary and analysis of PCN-based photocatalysts in the catalytic elimination of air pollutants have not been reported. The research progress of functional PCN-based composite materials as photocatalysts for the removal of air pollutants is reviewed here. The working mechanisms of each enhancement modification are elucidated and discussed on structures (nanostructure, molecular structue, and composite) regarding their effects on light-absorption/utilization, reactant adsorption, intermediate/product desorption, charge kinetics, and reactive oxygen species production. Perspectives related to further challenges and directions as well as design strategies of PCN-based photocatalysts in the heterogeneous catalysis of air pollutants are also provided.

Synthesis and characterization of CuxO/Bi2O3 oxides for removal of HCHO under visible light irradiation

Cu_xO/Bi₂O₃ oxides grown on nickel foam were synthesized via an electrodeposition method to degrade indoor HCHO under visible light irradiation and fully characterized by XRD, SEM, FT-IR, and UV-Vis technologies. The characterization results showed that the Cu_xO/Bi₂O₃ oxides were successfully loaded on nickel foam and the visible light response spectrum was expanded to 740 nm. Plackett-Burman design combined with central composite design has been used to optimize factors that affect HCHO removal performance. The results demonstrated that bismuth nitrate content, polyethylene glycol 600 content, sintering time, and lactic acid concentration were the four most important factors affecting the HCHO removal performance over Cu_xO/Bi₂O₃ sample. The optimum Cu_xO/Bi₂O₃ sample could degrade 88.796% of HCHO in 300 min at the conditions of 4.28 mol/L lactic acid, 4.86% polyethylene glycol 600, 194.03 min sintering time, and 45.83 g bismuth nitrate, and the HCHO removal rate remained 82.3% after five cycles. A plausible mechanism for the degradation of HCHO under visible light irradiation was proposed. This work provides a feasible solution for removing indoor formaldehyde in the field of photocatalysis.

Tunable formaldehyde sensing properties of palladium cluster decorated graphene

The ability to tune the adsorption strength of the targeted gas on sensing materials is crucial for sensing applications. By employing first-principles calculations the adsorption and sensing properties of HCHO on small Pd _n (n = 1-6) cluster decorated graphene have been systematically investigated. The adsorption energy is found to depend on the size of the Pd _n cluster and can be tuned in a wide range from -0.68 eV on Pd(111) to -1.98 eV on the Pd₃/graphene system. We also find that the Pd _n /graphene (n = 5 and 6) systems have an appropriate adsorption energy for HCHO gas sensing. The current-voltage curves are calculated by the non-equilibrium Green's function method for the two-probe nano-sensor devices along both the armchair and zigzag directions. The devices constructed with Pd _n /graphene (n = 5 and 6), having the highest absolute response over 20% at small voltages, should be applicable for HCHO detection. This work provides a theoretical basis for exploring potential applications of metal cluster decorated graphene for gas sensing.

Introducing Polyhydroxyurethane Hydrogels and Coatings for Formaldehyde Capture

Formaldehyde (FA) is a harmful chemical product largely used for producing resins found in our living spaces. Residual FA that leaches out the resin contributes to our indoor air pollution and causes some important health issues. Systems able to capture this volatile organic compound are highly desirable; however, traditional adsorbents are most often restricted to air filtration systems. Herein, we report novel waterborne coatings that are acting as a FA sponge for indoor air decontamination. These coatings, of the poly(hydroxyurethane) (PHU) type, rich in primary amine groups, are prepared by the polyaddition of a hydrosoluble dicyclic carbonate to a polyamine in water at room temperature under catalyst-free conditions. We highlight the importance of the choice of the polyamine on the curing rate of the formulation and on the FA capture ability of PHU. The excellent FA capturing ability of the best candidate is rationalized by investigating the action mode of the polyamine used to construct PHUs. With poly(vinyl amine), FA is covalently and permanently bound to PHU, with no release over time. The performance of the coating in FA abatement is impressive, with more than 90% of captured FA after one day of contact. The facility to prepare these transparent and colorless coatings from waterborne formulations gives access to new efficient indoor air depolluting solutions, potentially applicable to various surfaces of our living spaces (wall, ceiling, etc.).

Efficient removal of formaldehyde using metal-biochar derived from acid mine drainage sludge and spent coffee waste

A novel metal-biochar (Biochar/AMDS) composite were fabricated by co-pyrolysis of spent coffee waste (SCW)/acid mine drainage sludge (AMDS), and their effective application in adsorptive removal of air pollutants such as formaldehyde in indoor environments was evaluated. The physicochemical characteristics of Biochar/AMDS were analyzed using SEM/EDS, XRF, XRD, BET, and FTIR. The characterization results illustrated that Biochar/AMDS had the highly porous structure, carbonaceous layers, and heterogeneous Fe phases (hematite, metallic Fe, and magnetite). The fixed-bed column test showed that the removal of formaldehyde by Biochar/AMDS was 18.4-fold higher than that by metal-free biochar (i.e., SCW-derived biochar). Changing the ratio of AMDS from 1:6 to 1:1 significantly increased the adsorption capacity for formaldehyde from 1008 to 1811 mg/g. In addition, thermal treatment of used adsorbent at 100 °C effectively restored the adsorptive function exhausted during the column test. These results provide new insights into the fabrication of practical, low-cost and ecofriendly sorbent for formaldehyde.

Research Progress of Adsorption and Photocatalysis of Formaldehyde on TiO2/AC

Based on the increasingly serious formaldehyde pollution, effective degradation of formaldehyde has become a practical problem that humans urgently need to solve. Among many treatment methods, activated carbon has the advantages of large specific surface area, high adsorption efficiency, and uniform pore size distribution. As a kind of clean photocatalytic material for formaldehyde degradation, titanium dioxide supported by activated carbon has become a research hotspot to develop adsorption-catalytic materials for formaldehyde degradation. In this paper, the research progress of activated carbon and its modification, the photocatalytic principle and modification of titanium dioxide, and TiO2/AC materials are reviewed. The results show that the pore size distribution gradient and acidic oxygen-containing functional groups of activated carbon play key roles in the formaldehyde adsorption process. TiO2 doped with metal ions and nonmetal ions can significantly improve the photocatalytic activity. The TiO2/AC material can greatly improve the photocatalytic rate and achieve the technical goal of efficient and clean degradation for formaldehyde.

Associations between prenatal exposure to volatile organic compounds and neurodevelopment in 12-month-old children: The Japan Environment and Children's Study (JECS)

In recent years, there has been an increase in the number of problems associated with neurodevelopmental disorders in children, and there has been a growing interest in the relationship between environmental chemicals and children's health. The objective of this study was to examine whether an association exists between occupational or environmental prenatal maternal exposure to volatile organic compounds and the risk of neurodevelopmental disorders in children using Japanese translations of the Ages & Stages Questionnaires, Third Edition (J-ASQ-3). An increase in the risk of neurodevelopmental delay in 12-month-old children associated with maternal exposure to formalin or formaldehyde was identified in terms of problem-solving (odds ratio (OR): 1.76, 95% confidence interval (CI): 0.99-3.12) and personal-social skills (OR: 3.32, 95% CI: 1.46-7.55). It is not clear whether or not this tendency is reversible, and whether it is observed past 12 months of age. Further research and a preventive approach are needed.

Influencing factors of carbonyl compounds and other VOCs in commercial airliner cabins: On-board investigation of 56 flights

Volatile organic compounds (VOCs) as a non-negligible aircraft cabin air quality (CAQ) factor influence the health and comfort of passengers and crew members. On-board measurements of carbonyls (short-chain (C₁ -C₆ )) and other volatile organic compounds (VOCs, long-chain (C₆ -C₁₆ )) with a total of 350 samples were conducted in 56 commercial airliner cabins covering 8 aircraft models in this study. The mean concentration for each individual carbonyl compound was between 0.3 and 8.3 μg/m³ (except for acrolein & acetone, average = 20.7 μg/m³ ) similar to the mean concentrations of other highly detected VOCs (long-chain (C₆ -C₁₆ ), 97% of which ranged in 0-10 μg/m³ ) in aircraft cabins. Formaldehyde concentrations in flights were significantly lower than in residential buildings, where construction materials are known formaldehyde sources. Acetone is a VOC emitted by humans, and its concentration in flights was similar to that in other high-occupant density transportation vehicles. The variation of VOC concentrations in different flight phases of long-haul flights was the same as that of CO₂ concentration except for the meal phase, which indicates the importance of cabin ventilation in diluting the gaseous contaminants, while the sustained and slow growth of the VOC concentrations during the cruising phase in short-haul flights indicated that the ventilation could not adequately dilute the emission of VOCs. For the different categories of VOCs, the mean concentration during the cruising phase of benzene series, aldehydes, alkanes, other VOCs (detection rate > 50%), and carbonyls in long-haul flights was 44.2 µg/m³ , 17.9 µg/m³ , 18.6 µg/m³ , 31.5 µg/m³ , and 20.4 µg/m³  lower than those in short-haul flights, respectively. Carbonyls and d-limonene showed a significant correlation with meal service (p < 0.05). Unlike the newly decorated rooms or new vehicles, the inner materials were not the major emission sources in aircraft cabins. Practical Implications. The on-board measurements of 56 flights enrich the VOC database of cabin environment, especially for carbonyls. The literature review of carbonyls in the past 20 years contributes to the understanding the current status of cabin air quality (CAQ). The analysis of VOC concentration variation for different flight phases, flight duration, and aircraft age lays a foundation for exploring effective control methods, including ventilation and purification for cabin VOC pollution. The enriched VOC data is helpful to explore the key VOCs of aircraft cabin environment and to evaluate the acute/chronic health exposure risk of pollutants for passengers and crew members.

Estimates of emission strengths of 43 VOCs in wintertime residential indoor environments, Beijing

There are many sources of volatile organic compounds (VOCs) in indoor environments, leading to much higher total indoor VOC concentrations than outdoor counterparts. Given the potential health hazards associated with VOC exposure, it is necessary to estimate the indoor VOC emission strengths. In this study, the indoor and outdoor concentrations of 43 VOCs were concurrently measured in 8 urban residences, Beijing. The indoor/outdoor concentration ratio was used to screen out 36 species having significant indoor sources. A one-compartment steady-state model was developed to estimate the indoor emission strengths of these VOCs, in which ventilation and reaction with ozone were included as sink routes. The order of VOCs in terms of indoor emission strength was d-limonene (a median value of 1.05 g/h), α-pinene (82.50 mg/h), styrene (24.12 mg/h), ß-pinene (9.70 mg/h), formaldehyde (1.97 mg/h), n-dodecane (1.82 mg/h), n-pentadecane (1.66 mg/h), n-hexadecane (1.62 mg/h), n-undecane (1.20 mg/h), acetaldehyde (1.05 mg/h) and 1, 4-dichlorobenzene (0.80 mg/h). The sum of estimates of those VOCs accounted for >95% of total emission strength. Specific indoor sources of those VOCs in the tested homes were identified. Air exchange rate, indoor temperature and air humidity were found to pose significant impacts to the indoor emission strengths of VOCs.

Systematic investigation of the aza-Cope reaction for fluorescence imaging of formaldehyde in vitro and in vivo

Increasing evidence has highlighted the endogenous production of formaldehyde (FA) in a variety of fundamental biological processes and its involvement in many disease conditions ranging from cancer to neurodegeneration. To examine the physiological and pathological relevance and functions of FA, fluorescent probes for FA imaging in live biological samples are of great significance. Herein we report a systematic investigation of 2-aza-Cope reactions between homoallylamines and FA for identification of a highly efficient 2-aza-Cope reaction moiety and development of fluorescent probes for imaging FA in living systems. By screening a set of N-substituted homoallylamines and comparing them to previously reported homoallylamine structures for reaction with FA, we found that N-p-methoxybenzyl homoallylamine exhibited an optimal 2-aza-Cope reactivity to FA. Theoretical calculations were then performed to demonstrate that the N-substituent on homoallylamine greatly affects the condensation with FA, which is more likely the rate-determining step. Moreover, the newly identified optimal N-p-methoxybenzyl homoallylamine moiety with a self-immolative β-elimination linker was generally utilized to construct a series of fluorescent probes with varying excitation/emission wavelengths for sensitive and selective detection of FA in aqueous solutions and live cells. Among these probes, the near-infrared probe FFP706 has been well demonstrated to enable direct fluorescence visualization of steady-state endogenous FA in live mouse brain tissues and elevated FA levels in a mouse model of breast cancer. This study provides the optimal aza-Cope reaction moiety for FA probe development and new chemical tools for fluorescence imaging and biological investigation of FA in living systems.

On the Flip Side of Mask Wearing: Increased Exposure to Volatile Organic Compounds and a Risk-Reducing Solution

Surgical masks have been worn by the public worldwide during the COVID-19 pandemic, yet hazardous chemicals in the petroleum-derived polymer layer of masks are currently ignored and unregulated. These organic compounds pose potential health risks to the mask wearer through dermal contact or inhalation. Here, we show that surgical masks from around the world are loaded with semivolatile and volatile organic compounds (VOCs), including alkanes, polycyclic aromatic hydrocarbons (PAHs), phthalate esters, and reactive carbonyls at ng to μg/mask levels. Naphthalene was the most abundant mask-borne PAH, accounting for over 80% of total PAH levels; acrolein, a mutagenic carbonyl, was detected in most of the mask samples, and di(2-ethylhexyl) phthalate, an androgen antagonist, was detected in one-third of the samples. Furthermore, there is large mask-to-mask variability of the residue VOCs, revealing the uneven quality of masks. We confirm that masks containing more residue VOCs lead to significantly higher exposure levels and associated disease risks to the wearer, which should warrant the attention of the general public and regulatory agencies. We find that heating the masks at 50 °C for as short as 60 min lowers the total VOC content by up to 80%, providing a simple method to limit our exposure to mask-borne VOCs.

Photocatalytic degradation of surface-coated tourmaline-titanium dioxide for self-cleaning of formaldehyde emitted from furniture

Formaldehyde emission is an intrinsic property derived from aldehyde-based resin that is used in wood-based composites. To reduce formaldehyde emission from plywood, the composite catalyst of tourmaline-titanium dioxide (T-TiO₂) was fabricated by the sol-gel method. Furthermore, the impregnated paper loaded with the T-TiO₂ composite catalyst was used to decorate the surface of 5-layer poplar plywood. The physicochemical structure, photocatalytic activity of T-TiO₂ composite catalyst and its mechanism of degrading gaseous formaldehyde and generating air negative ions were assessed. The results discovered that the synergistic influence of the tourmaline and TiO₂ anatase nanocrystals achieved good photodegradation of the gaseous formaldehyde. The neat T(20%)-TiO₂ catalyst offered a higher formaldehyde removal efficiency (92.2%) than other catalysts, possessing 800 ions/cm³ of air negative ions concentration after 10-h visible light irradiation. The poplar plywood with a load of 3% T(20%)-TiO₂ catalyst can stably induce the degradation formaldehyde into air negative ions with a concentration of 1200 ions/cm³ in visible light. The impregnation process of paper was feasible to be industrialized and the decorated wood-based composites can be widely applied in the furniture industry.

Crystal-structure dependent reaction pathways in photocatalytic formaldehyde mineralization on BiPO4

Formaldehyde as significant environmental hazard in air seriously harm the environment and human health. Although photocatalysis has demonstrated the possibility for HCHO degradation, it has long been limited by unsatisfied degradation efficiency and the unclear reaction mechanism. Here, we confirm that surface atomic arrangement of BiPO₄ plays a critical role in photooxidation of HCHO via modulating the reaction pathway, offering 2.63 times enhancement of HCHO degradation efficiency. We dissect the processes in the photocatalytic reaction by DFT calculation, ROS monitoring, and in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) investigation. Specifically, we reveal that the controlling surface atomic arrangement could modulate adsorption model from single-point to bridging, and promote activation of small molecules. Concurrently, the active surface dependent on crystal structure facilitates the efficient transformation of intermediates (HCOOH*) (reducing energy barrier from 0.41 to -0.35 eV), producing final-product (H₂CO₃, ∆G = -0.35 eV) while suppressing toxic by-product (CO, ∆G = 0.32 eV), which contributes to the sustained deep mineralization of HCHO with enhancement by 61.4%. The findings are crucial as they provide crystal-structure related insights into the design of efficient catalysts for photocatalytic HCHO degradation. Ultimately, current molecular understanding should unlock the solar-driven catalytic pathways for other oxidation reactions.

Photocatalytic oxidation technology for indoor air pollutants elimination: A review

As more people are spending the majority of their daily lives indoors, indoor air quality has been acknowledged as an important factor influencing human health, with increasing research attention in recent decades. Indoor air pollutants (IAPs), such as volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs), can cause acute irritation and chronic diseases. Photocatalytic oxidation (PCO) technology is an efficient approach for eliminating IAPs. In this review, the development of PCO technology was explained and discussed to promote future development of PCO technology for IAP elimination. First, the health effects and the measured concentrations of typical VOCs and SVOCs in indoor environments worldwide were briefly introduced. Subsequently, the development and limitations of some typical photocatalytic reactors (including packed-bed reactors, monolithic reactors, optical fiber reactors, and microreactors) were summarized and compared. Then, the influences of operating parameters (including initial concentration of contaminants, relative humidity, space velocity, light source and intensity, catalyst support materials, and immobilization method) and the degradation pathways as well as intermediates of PCO technology were elucidated. Finally, the possible challenges and future development directions regarding PCO technology for IAP elimination were critically proposed and addressed.

Real-time molecular characterization of air pollutants in a Hong Kong residence: Implication of indoor source emissions and heterogeneous chemistry

Due to the high health risks associated with indoor air pollutants and long-term exposure, indoor air quality has received increasing attention. In this study, we put emphasis on the molecular composition, source emissions, and chemical aging of air pollutants in a residence with designed activities mimicking ordinary Hong Kong homes. More than 150 air pollutants were detected at molecular level, 87 of which were quantified at a time resolution of not less than 1 hour. The indoor-to-outdoor ratios were higher than 1 for most of the primary air pollutants, due to emissions of indoor activities and indoor backgrounds (especially for aldehydes). In contrast, many secondary air pollutants exhibited higher concentrations in outdoor air. Painting ranked first in aldehyde emissions, which also caused great enhancement of aromatics. Incense burning had the highest emissions of particle-phase organics, with vanillic acid and syringic acid as markers. The other noteworthy fingerprints enabled by online measurements included linoleic acid, cholesterol, and oleic acid for cooking, 2,5-dimethylfuran, stigmasterol, iso-/anteiso-alkanes, and fructose isomers for smoking, C₂₈ -C₃₄ even n-alkanes for candle burning, and monoterpenes for the use of air freshener, cleaning agents, and camphor oil. We showed clear evidence of chemical aging of cooking emissions, giving a hint of indoor heterogeneous chemistry. This study highlights the value of organic molecules measured at high time resolutions in enhancing our knowledge on indoor air quality.

Hydrothermal synthesis of nitrogen-doped carbon quantum dots from lignin for formaldehyde determination

This work assessed the fabrication of nitrogen-doped CQDs (NCQDs) from alkali lignin (AL) obtained from spruce, representing a green, low-cost biomass generated by the pulp and biorefinery industries. The AL was found to retain its original lignin skeleton and could be used to produce NCQDs with excellent photoluminescence properties by one-pot hydrothermal treatment of AL and m-phenylenediamine. These NCQDs exhibited blue-green fluorescence (FL) with excitation/emission of 390/490 nm under optimal conditions. The NCQDs showed pH and excitation wavelength-dependent FL emission behaviors. On the basis of the exceptional selective response of these NCQDs to specific solvents, we developed a FL probe for the detection of formaldehyde (FA). The FL intensity of NCQDs was found to be directly proportional to the concentration of FA in the range of 0.05 to 2 mM (R² = 0.993), with a detection limit of 4.64 µM (based on 3σ/K). A composite film comprising NCQDs with poly(vinyl alcohol) was found to act as a sensor with a good FL response to FA gas. When exposed to gaseous FA, this film exhibited increased FL intensity and transitioned from blue-green to blue. A mechanism is proposed in which the NCQDs react rapidly with FA to generate Schiff bases that result in enhanced FL emission and the observed blue shift in color.

A hydrothermal method for synthesis of lignin-based N-doped carbon quantum dots (NCQDs) proposes a mechanism for rapid reaction of NCQDs with formaldehyde to generate Schiff bases, which leads to enhanced FL emission and the observed blue shift.

Assessment of the mutagenicity of two common indoor air pollutants, formaldehyde and toluene

Traditionally, direct-reading instruments have been used to directly determine the concentrations of indoor air pollutants that may exceed the regulation limits. However, these instruments cannot directly assess the potential health hazards of these pollutants to humans. In this study, we developed and improved a bacterial reverse mutation assay (Ames test) by using a direct gas exposure module to directly determine the mutagenicity of indoor air quality using five tester bacterial strains (TA98, TA100, TA102, TA1535, and TA1537). Thereafter, the module was used to evaluate the effects of exposure time, different concentrations of HCHO or toluene, and mutagenic activities. We found that TA100 was the most sensitive strain and was reverted by relatively lower concentrations of 0.035 ppm HCHO. Furthermore, 50 ppm of toluene exposures caused a significant increase in the number of revertant colonies of TA100 without S9 activation at the 1.5-8-h exposure time intervals. Our findings provide new evidence that gaseous HCHO exposure could display weak but direct, time-dependent, and dose-dependent mutagenic activities. The weak, direct-acting, indirect-acting, and time-dependent mutagen of 50 ppm toluene was also confirmed. Moreover, our improved Ames module and the exposure conditions provided in this study can be further applied to evaluate the mutagenicity of indoor air quality.

A Golgi Apparatus-Targeting, Naphthalimide-Based Fluorescent Molecular Probe for the Selective Sensing of Formaldehyde

Formaldehyde (FA) is a colorless, flammable, foul-smelling chemical used in building materials and in the production of numerous household chemical goods. Herein, a fluorescent chemosensor for FA is designed and prepared using a selective organ-targeting probe containing naphthalimide as a fluorophore and hydrazine as a FA-binding site. The amine group of the hydrazine reacts with FA to form a double bond and this condensation reaction is accompanied by a shift in the absorption band of the probe from 438 nm to 443 nm upon the addition of FA. Further, the addition of FA is shown to enhance the emission band at 532 nm relative to the very weak fluorescent emission of the probe itself. Moreover, a high specificity is demonstrated towards FA over other competing analytes such as the calcium ion (Ca2+), magnesium ion (Mg2+), acetaldehyde, benzaldehyde, salicylaldehyde, glucose, glutathione, sodium sulfide (Na2S), sodium hydrosulfide (NaHS), hydrogen peroxide (H2O2), and the tert-butylhydroperoxide radical. A typical two-photon dye incorporated into the probe provides intense fluorescence upon excitation at 800 nm, thus demonstrating potential application as a two-photon fluorescent probe for FA sensing. Furthermore, the probe is shown to exhibit a fast response time for the sensing of FA at room temperature and to facilitate intense fluorescence imaging of breast cancer cells upon exposure to FA, thus demonstrating its potential application for the monitoring of FA in living cells. Moreover, the presence of the phenylsulfonamide group allows the probe to visualize dynamic changes in the targeted Golgi apparatus. Hence, the as-designed probe is expected to open up new possibilities for unique interactions with organ-specific biological molecules with potential application in early cancer cell diagnosis.

Low Temperature HCHO Detection by SnO2/TiO2@Au and SnO2/TiO2@Pt: Understanding by In-Situ DRIFT Spectroscopy

In this work we analyze the effectiveness of decoration of nanocrystalline SnO2/TiO2 composites with gold nanoparticles (Au NPs) and platinum nanoparticles (Pt NPs) in enhancing gas sensor properties in low-temperature HCHO detection. Nanocrystalline SnO2/TiO2 composites were synthesized by a chemical precipitation method with following modification with Pt and Au NPs by the impregnation method. The nanocomposites were characterized by TEM, XRD, Raman and FTIR spectroscopy, DRIFTS, XPS, TPR-H2 methods. In HCHO detection, the modification of SnO2 with TiO2 leads to a shift in the optimal temperature from 150 to 100 °C. Further modification of SnO2/TiO2 nanocomposites with Au NPs increases the sensor signal at T = 100 °C, while modification with Pt NPs gives rise to the appearance of sensor responses at T = 25 °C and 50 °C. At 200 °C nanocomposites exhibited high selectivity toward formaldehyde within the sub-ppm concentration range among different VOCs. The influence of Pt and Au NPs on surface reactivity of SnO2/TiO2 composite and enhancement of the sensor response toward HCHO was studied by DRIFT spectroscopy and explained by the chemical and electronic sensitization mechanisms.

Evaluating Indoor Air Chemical Diversity, Indoor-to-Outdoor Emissions, and Surface Reservoirs Using High-Resolution Mass Spectrometry

Detailed offline speciation of gas- and particle-phase organic compounds was conducted using gas/liquid chromatography with traditional and high-resolution mass spectrometers in a hybrid targeted/nontargeted analysis. Observations were focused on an unoccupied home and were compared to two other indoor sites. Observed gas-phase organic compounds span the volatile to semivolatile range, while functionalized organic aerosols extend from intermediate volatility to ultra-low volatility, including a mix of oxygen, nitrogen, and sulfur-containing species. Total gas-phase abundances of hydrocarbon and oxygenated gas-phase complex mixtures were elevated indoors and strongly correlated in the unoccupied home. While gas-phase concentrations of individual compounds generally decreased slightly with greater ventilation, their elevated ratios relative to controlled emissions of tracer species suggest that the dilution of gas-phase concentrations increases off-gassing from surfaces and other indoor reservoirs, with volatility-dependent responses to dynamically changing environmental factors. Indoor-outdoor emissions of gas-phase intermediate-volatility/semivolatile organic hydrocarbons from the unoccupied home averaged 6-11 mg h^-1, doubling with ventilation. While the largest single-compound emissions observed were furfural (61-275 mg h^-1) and acetic acid, observations spanned a wide range of individual volatile chemical products (e.g., terpenoids, glycol ethers, phthalates, other oxygenates), highlighting the abundance of long-lived reservoirs resulting from prior indoor use or materials, and their gradual transport outdoors.

A Kinetic Analysis of DNA-Deoxy Guanine Adducts in the Nasal Epithelium Produced by Inhaled Formaldehyde in Rats-Assessing Contributions to Adduct Production From Both Endogenous and Exogenous Sources of Formaldehyde

Although formaldehyde is a normal constituent of tissues, lifetime inhalation exposures at 6 h/day, 5 days/week at concentrations ≥6 ppm caused a nonlinear increase in nasal tumors in rats with incidence reaching close to 50% at 15 ppm. Studies with heavy isotope labeled [¹³CD₂]-formaldehyde permit quantification of both the mass-labeled exogenous and endogenous DNA-formaldehyde reaction products. An existing pharmacokinetic model developed initially to describe ¹⁴C-DNA-protein crosslinks (DPX) provided a template for describing the time course of mass-labeled adducts. Published datasets included both DPX and N₂-HO¹³CD₂-dG adducts measured after a single 6-h exposure to 0.7, 2, 6, 9, 10, or 15 ppm formaldehyde, after multi-day exposures to 2 ppm for 6 h/day, 7 days/week with interim sacrifices up to 28 days, and after 28-day exposures for 6 h/day, 7 days/week to 0.3, 0.03, or 0.001 ppm. The existing kinetic model overpredicted endogenous adducts in the nasal epithelium after 1-day [¹³CD₂]-formaldehyde exposure, requiring adjustment of parameters for rates of tissue metabolism and background formaldehyde. After refining tissue formaldehyde parameters, we fit the model to both forms of adducts by varying key parameters and optimizing against all 3 studies. Fitting to all these studies required 2 nonlinear pathways—one for high-exposure saturation of clearance in the nasal epithelial tissues and another for extracellular clearance that restricts uptake into the epithelial tissue for inhaled concentrations below 0.7 ppm. This refined pharmacokinetic model for endogenous and exogenous formaldehyde acetal adducts can assist in updating biologically based dose-response models for formaldehyde carcinogenicity.

Indoor air quality in shopping and storage areas

In retail stores, workers are constantly exposed to new manufactured goods. The issue of the exposure of retail workers to volatile organic compounds (VOCs) should clearly be considered. Therefore, this study provides data regarding VOC concentrations in ten French retail stores. The stores were chosen to represent various products: sports goods, shoes and leather, furniture, car equipment, bazaars, online-sales storage, clothes, books, DIY (do-it-yourself), and household appliances. VOCs and aldehydes were actively sampled on the same day in five to seven locations per building and outdoors. Toluene and formaldehyde were omnipresent with indoor concentrations reaching 252 and 53 µg/m³ , respectively. The car equipment store, followed by clothing, shoes, and leather, and DIY stores showed the worst indoor air quality. High concentrations were measured, for example, the maximum α-pinene concentration in the furniture and DIY stores was 364 and 141 µg/m³ , respectively, and the heptane concentration in the car equipment store reached 1,316 µg/m³ . Two VOCs classified as toxic to reproduction were measured: hexane in the car equipment store and the bazaar, and dimethylformamide in the sports goods store. This study shows some disparities in the indoor concentrations among different locations in the same store, particularly between sales and storage areas.