Formaldehyde exposure and health status in households

How can interventions of building renovation and household energy conversion effectively improve the physical and mental health outcomes? A systematic review and meta-analysis

Household energy efficiency measures can effectively reduce indoor air pollution and positively impact the health of residents, but there is no conclusive evidence on the effectiveness of different energy efficiency measures for various diseases. This study used systematic review and meta-analysis to research the effects of two interventions on residents’ physical and mental health: building renovation (heating, insulation, double-glazed windows and ventilation) and household energy conversion (stove upgrading and clean energy use). A total of 79 papers published between 1977 and 2023 were reviewed in this study, providing comprehensive meta-analytic evidence on the effectiveness of energy efficiency measures. The results show that household energy-saving measures have a minor but significant positive influence on residents’ physical and mental health, with the effect on mental health being larger than the impact on physical health. Stove upgrading is advantageous in respiratory and cardiovascular diseases; insulation can greatly reduce the risk of skin diseases; heating is beneficial in sensory and digestive diseases; and clean energy use can successfully mitigate integrative diseases. Furthermore, a combination of heating and insulation measures has the most favourable influence on mental health conditions such as depression, anxiety and social isolation. The study findings can help residents, policymakers and relevant organizations take appropriate interventions to promote residents’ physical and mental health.

VOC transport in an occupied residence: Measurements and predictions via deep learning

Monitoring and prediction of volatile organic compounds (VOCs) in realistic indoor settings are essential for source characterization, apportionment, and exposure assessment, while it has seldom been examined previously. In this study, we conducted a field campaign on ten typical VOCs in an occupied residence, and obtained the time-resolved VOC dynamics. Feature importance analysis illustrated that air change rate (ACR) has the greatest impact on the VOC concentration levels. We applied three multi-feature (temperature, relative humidity, ACR) deep learning models to predict the VOC concentrations over ten days in the residence, indicating that the long short-term memory (LSTM) model owns the best performance, with predictions the closest to the observed data, compared with the other two models, i.e., recurrent neural network (RNN) model and gated recurrent unit (GRU) model. We also found that human activities could significantly affect VOC emissions in some observed erupted peaks. Our study provides a promising pathway of estimating long-term transport characteristics and exposures of VOCs under varied conditions in realistic indoor environments via deep learning.

Shape memory luminescent cellulose/chitosan hydrogel for high sensitive detection of formaldehyde

Hybrid hydrogels containing biomacromolecules have been widely used in sensors, fluorescent probes, and other fields due to their high biocompatibility and nontoxicity. In this paper, tough hydrogels with interconnected macro-pores have been fabricated by freeze-induced chemical cross-linking of microfibrillated cellulose (MFC) and organic modified chitosan (CS). In this hydrogel materials, three-dimensional networks were formed by abundant hydrogen bonds and chemical cross-linking. Luminescent lanthanide complexes were covalently bonded to the hydrogel networks through coordination of Eu³⁺ ions with 2, 3-pyridine dicarboxylic acid modified chitosan. The luminescence of hydrogel materials was further improved by the replacement of coordination water with 2-thiophenyltrifluoroacetone (TTA). The prepared hydrogels showed excellent shape memory properties both under water and in air. The stress of the hybrid hydrogel at 80 % strain can reach 159 kPa, which is much higher than that of the traditional microfibrillated cellulose-based hydrogels. The obtained luminescent hybrid hydrogels exhibited an excellent fluorescence detection effect on formaldehyde. The detection limit for formaldehyde is 45.7 ppb, which is much lower than the WHO standard (80 ppb for indoor air). The novel, facile preparing procedure may extend the potential applications of hybrid lanthanide luminescent hydrogel as fluorescence probes for pollution monitoring, especially for formaldehyde and other organic aldehydes.

Recent advances in selective formaldehyde detection in biological and environmental samples by fluorometric and colorimetric chemodosimeters

Formaldehyde, a highly reactive carbonyl species, has been widely used in day-to-day life owing to its numerous applications in essential commodities, etc.; the extrusion of formaldehyde from these sources basically leads to increased formaldehyde levels in the environment. Additionally, formaldehyde is endogenously produced in the human body via several biological processes. Considering the adverse effects of formaldehyde, it is highly important to develop an efficient and reliable method for monitoring formaldehyde in environmental and biological samples. Several chemodosimeters (reaction-based sensing probes) have been designed and synthesized to selectively detect the presence of formaldehyde utilizing the photophysical properties of molecules. In this review, we have comprehensively discussed the recent advances in the design principles and sensing mechanisms of developed probes and their biological/environmental applications in selective formaldehyde detection and imaging endogenous formaldehyde in cells. We have summarized the literature based on three different categories: (i) the Schiff base reaction, (ii) the 2-aza-Cope sigmatropic rearrangement reaction and (iii) miscellaneous approaches. In all cases, reactions are accompanied by changes in color and/or emission that can be detected by the naked eye.

Effect of formaldehyde properties on SnO2 clusters gas sensitivity: A DFT study

Formaldehyde (CH₂O) properties such as flash point and autoignition temperature have a great effect on the temperature range of sensitivity of sensors applied to detect CH₂O gas. Tin dioxide nanocrystal interaction with formaldehyde is investigated from room temperature to 500 °C using transition state and density functional theory. Gibbs free energy, enthalpy, and entropy of activation and reaction are evaluated as a function of temperature. The sensitivity and response time of SnO₂ clusters towards formaldehyde are evaluated. Results show that the activation energy of SnO₂ clusters with formaldehyde increases with the rise of temperature while the reaction energy decreases (in negative value) with the rise of temperature. Response time is inversely proportional to formaldehyde concentration. The highest CH₂O gas-sensitive range of SnO₂ is confined between the formaldehyde flash point at 64 °C and the autoignition temperature at 430 °C. The effect of partial oxidation and dissociation of formaldehyde is discussed.

An inexpensive and sensitive turn-on luminescence protocol for sensing formaldehyde

Formaldehyde (FA), the simplest and most widely-used aldehyde, can pose serious health issues when present at elevated concentrations. Here, we report a "turn-on" terbium photoluminescence method for the efficient detection of FA. A pro-sensitizer molecule was designed and synthesised, which releases the sensitizer in the presence of FA inside the terbium cholate hydrogel matrix, resulting in a "turn-on" luminescence response. The introduction of a paper-based sensing approach makes the protocol simpler and cost-effective, and has a detection limit as low as 100 nM.

Atmospheric oxidation of 2-fluoropropene (CH3CFCH2) with Cl atom and aerial degradation of its product radicals by computational study

Primary degradation of 2-fluoropropene initiated by Cl atom and subsequent degradation of its product radials.

Tropospheric degradation of 2-fluoropropene (CH3CFCH2) initiated by hydroxyl radical: Reaction mechanisms, kinetics and atmospheric implications from DFT study

Degradation of hydrofluoro-olefins (HFOs) with oxidants plays a significant role in the troposphere. Thus, we have investigated detail theoretical calculations of hydroxyl radical (^•OH) initiated oxidation of 2-fluoropropene (CH₃CFCH₂) using M06-2X/6-311++G(d,p) level of theory. Here, we have considered different possible H-abstraction and OH addition for the degradation of CH₃CFCH₂ molecule. The potential energy analysis shows that OH-addition channels are more dominant than H-abstraction channels. The calculated reaction enthalpies (Δ_rH°) and Gibbs free energies (Δ_rG°) also suggest that OH-addition reaction channels are more favourable than H-abstraction channels. The overall rate coefficients for CH₃CFCH₂ + ^•OH reaction is calculated within the temperature range of 250-450 K. The observed overall rate coefficient (2.01 × 10^-11 cm³ molecule^-1 s^-1) at 298 K for the titled reaction is found to be in good agreement with the earlier reported experimental rate coefficient. The calculated percentage branching ratio shows that the contribution of OH-addition to α-carbon and β-carbon of CH₃CFCH₂ molecule are 85.10% and 14.20% to the overall rate coefficient while H-abstractions have a negligible contribution. Based on the kinetics calculations, the atmospheric lifetime of the titled molecule is found to be 0.6 days. Further, we have also explored the degradation pathways of OH-addition product radicals and found acetyl fluoride (CH₃CFO) and formaldehyde (HCHO) are the end degradation products.

Recyclable Fully Biobased Chitosan Adsorbents Spray-Dried in One Pot to Microscopic Size and Enhanced Adsorption Capacity

A facile one-pot spray-drying process was developed for fabrication and in situ crosslinking of chitosan microspheres to improve the adsorption capacity by microscopic design. A fully biobased nature was achieved by utilizing genipin (GP) as a crosslinking agent and chitosan-derived nanographene oxide (nGO) as a property tuner. The produced chitosan microspheres were further proven as powerful adsorbents for common wastewater contaminants such as anionic dyes and pharmaceutical contaminants, here modeled by methyl orange (MO) and diclofenac sodium (DCF). By regulating the amount of GP and nGO, as well as by controlling the process parameters including the spray-drying inlet temperature and postheat treatment, the surface morphology, size, zeta potential, and adsorption efficiency of the microspheres could be tuned accordingly. The adsorption efficiency for MO and DCF reached 98.9 and 100%, respectively. The microspheres retained high DCF adsorption efficiency after six adsorption and desorption cycles, and the recyclability was improved by the incorporated nGO. The fabricated microspheres, thus, have great potential as reusable and eco-friendly adsorbents.

An Aggregation-Induced Emission-Based "Turn-On" Fluorescent Probe for Facile Detection of Gaseous Formaldehyde

Gaseous formaldehyde (FA), a common indoor pollutant, presents a serious threat to human health. As an efficient tool for FA detection, fluorescent probes exhibit the advantages of low cost, ease of use, facile operation, etc. However, previously developed FA fluorescent probes are mostly based on fluorophores with aggregation-caused quenching features and thus require dispersion in solvent to detect FA. In this study, a fluorescent probe (TPE-FA) based on an aggregation-induced emission (AIE) fluorophore (tetraphenylethylene) has been developed for facile detection of gaseous FA through a fluorescence "turn-on" response. TPE-FA reacts with FA through 2-aza-Cope sigmatropic rearrangement. Based on the AIE features of TPE-FA, we fabricated a portable solid sensor, FA test plate, by directly loading TPE-FA on high performance thin-layer chromatography silica gel plate. The FA test plate achieved sensitive, selective, and quantitative detection of gaseous FA. The detection limit (0.036 mg/m³) of the FA test plate is lower than the air quality guideline value of gaseous FA (0.1 mg/m³) recommended by WHO. As a solid sensor for gaseous FA, the FA test plate based on AIE molecule is portable, which enables safer and more convenient use and transport compared to solution-based sensors.