A method using porous media to deliver gas-phase phthalates rapidly and at a constant concentration: Effects of temperature and media

Tuning multi-scale pore structures in carbonaceous films via direct ink writing and sacrificial templates for efficient indoor formaldehyde removal

The primary challenges impeding the extensive application of adsorption for indoor air purification have been low efficiency and effective capacity. To fill the research gap, we developed carbonaceous net-like adsorption films featuring multi-scale porous structures for efficient indoor formaldehyde removal. By optimizing the interfacial mass transfer and internal diffusion, we designed macro- to mesoscale meshes on the film surface and micro- to nano-scale pores within the materials, which were achieved by direct-ink-writing (DIW) printing and sacrificial template methods, respectively. Compared to unmodified planar films, the developed films exhibited a significant increase in the initial single-pass efficiency of formaldehyde from 68.1 % to 89.0 %, with the 8-hour effective adsorption capacity (EACad) spiking from 2.74 mg/g to 8.60 mg/g. Through thermal regeneration, the film demonstrated stable operation for 30 days through a long-term experiment over 250 hours, and EACad significantly increased to 241.7 mg/g. The multi-scale adsorption films achieved nearly the highest purification rates and capacities among existing physisorption and chemisorption technologies, with the lowest energy cost of 0.37 kW·h per day. The innovative design and fabrication of multi-scale adsorption films evidence its substantial application for indoor formaldehyde purification and provide a viable solution for carbon capture and gas separation in environmental engineering.

Global perspectives on indoor phthalates and alternative plasticizers: Occurrence and key transport parameters

Phthalates and emerging alternative plasticizers have garnered significant attention due to their ubiquitous presence indoors and potential adverse health effects. However, the occurrences and key transport parameters of indoor alternative plasticizers have not been sufficiently summarized and analyzed, complicating exposure evaluation and pollution control efforts. This study addresses the gap by providing a comprehensive overview of the occurrence and key transport parameters of the most reported plasticizers, including 10 phthalates and 14 alternative plasticizers. The plasticizer content in source materials was found to range up to 27.6 wt%. An empirical formula was developed to predict the surface-adjacent gaseous plasticizer concentration (y0) of source materials, with values ranging from 0.015 to 64.7 μg/m3. Variations in plasticizer concentrations across source, gas, particle, and dust phases were thoroughly analyzed over both temporal and spatial dimensions from a global perspective, indicating significant differences between continents over time. A detailed investigation of phthalate regulations across continents suggests that the earlier enactment of phthalate bans in Europe is likely a key factor contributing to the most significant decrease in indoor phthalate concentrations. Furthermore, after systematically reviewing mass-transfer and partitioning theories, we developed empirical formulas to predict mass-transfer coefficients (hm) and partition coefficients (K) for both phthalates and alternative plasticizers. Notably, the hm and K parameters of the plasticizers were thoroughly calculated for typical indoor interfaces, including airborne particles, settled dust, and impermeable and permeable materials. Overall, this study advances the understanding of indoor plasticizers, facilitating health-risk assessment and the development of suitable control and monitoring technologies.

A novel method for assessing indoor di 2-ethylhexyl phthalate (DEHP) contamination and exposure based on dust-phase concentration

Phthalates (PAEs) are a group of typical semivolatile organic compounds that are widely present in indoor environments with multiple phases. Indoor air, airborne particle and settled dust are considered to be typical indicators of PAE contamination as well as media of human exposure, and the interactions between them are complex. Among various phthalate compounds, di 2-ethylhexyl phthalate (DEHP) was identified as the predominant individual phthalate in settled dust. The existing DEHP contamination assessment requires multiphase sampling or solving the dynamic mass transfer models with multiple partial differential equations, which are both complicated and time-consuming. This study investigated the influence of the indoor source loading rate, surface type, particle size and cleaning frequency on the partitioning between the settled dust-phase, airborne particle-phase and gas-phase. The concentration correlations of DEHP between multiphases were consequently derived, which balance accuracy and complexity well. By comparison with field sampling data in the literatures, the rationality and accuracy of the concentration correlations were validated. Based on the concentration correlations, a new method of directly using dust-phase concentration to estimate the non-dietary exposure to DEHP was proposed. The results indicated that ingestion of settled dust contributes the most to non-dietary exposure. Special attention should be given to infants and toddlers, who suffer the highest daily exposure to DEHP among all age groups. This study provides a new and efficient solution for estimating indoor DEHP pollution loads conveniently and rapidly, offering valuable insights for future research in this field.

Phthalates in glass window films are associated with dormitory characteristics, occupancy activities and habits, and environmental factors

Phthalates are environmental endocrine disruptors that enter the human body through a variety of pathways and harm human health. The study aimed to explore the associations between phthalate concentrations in glass window films with dormitory characteristics, occupancy activities and habits, and environmental factors, of university dormitories. We surveyed these associations and measured the indoor environmental parameters of 144 dormitories from 13 universities in Beijing. Based on the results, we further explored the factors affecting phthalate concentrations using multivariate logistic regression. The results showed that phthalate concentrations in glass window films were associated with dormitory type, duration of occupancy, daily ventilation duration, window cleaning frequency, indoor relative humidity, light intensity, temperature, and particulate matter (PM₁₀) concentration. To date, there have only been a few studies on the factors that influence phthalate concentrations in glass window films; therefore, further study is needed. Our findings determined the influence of external factors on the different types of phthalates in window films, which helps understand indoor phthalate pollution and evaluate human exposure based on phthalate concentrations in glass window films.

Assessment of gas-phase concentrations of organophosphate flame retardants at the material surface using a midget emission cell coupled to solid-phase microextraction

Actual methods for on-site measurement of gaseous concentrations of Semi-Volatile Organic Compounds (SVOCs) at the material surface (y⁰) are not yet sufficiently developed mainly due to sampling difficulties. These concentrations are the key data to improve knowledge about indoor sources and human exposure to SVOCs. To the end, a specific emission cell coupled to solid-phase microextraction (SPME) was developed. The main challenge with this method is calibration because of very low volatility of SVOCs and static sampling mode. In this study, a generating system of organophosphate flame retardants (OFRs) using polyurethane foam as source combined with an active sampling method with Tenax tubes was proposed as a novel calibration device for SPME-based method. The generating system delivered stable OFR concentrations after 190 h of operation with a variation not exceeding ±5%. It allowed to obtain robust calibrations for tris-(2-chloropropyl)-phosphate (TCPP) and tri-butyl-phosphate (TBP) measured with the emission cell coupled to SPME-based method, define the optimal sampling requirements and achieve reproducible and accurate measurements of y⁰ at μg.m^-3 level. TCPP and TBP gas-phase concentrations at the polyurethane foam surface (y⁰) were followed up over more 228 days under controlled temperature conditions. A high stability of these concentrations was observed showing that polyurethane foam acts as a stable and continuous source of organophosphate flame retardants indoors. This novel method should be useful for assessing the dynamic of emissions from indoor sources and potential exposure to SVOCs in indoor environments.

The gas/particle partitioning behavior of phthalate esters in indoor environment: Effects of temperature and humidity

Phthalate esters (PAEs) are ubiquitous and among the most abundant semi-volatile organic compounds (SVOCs) in indoor environments. Due to their low saturated vapor pressure, SVOCs tend to adhere to indoor surfaces and particulate matters, which may result in higher total concentrations than occur in the gas phase alone. Thus, gas/particle partitioning of PAEs plays an important role in their indoor fates and health risks. However, the influence of indoor environmental parameters, including temperature and humidity, on the partitioning of PAEs between air and particles is rarely known. In this study, a novel experimental system was designed to investigate the effects of temperature and humidity on partitioning behavior between gas- and particle-phase PAEs. The chamber experiments were conducted at temperatures of 12.5 °C, 17.5 °C, 24.0 °C, 29.5 °C and 40.0 °C and moisture contents of 3.5 g/kg, 5.0 g/kg, 6.5 g/kg, 8.0 g/kg and 9.5 g/kg dry air. The results showed that higher temperatures led to stronger emission of phthalate esters from the PVC panel, which resulted in higher gas-phase concentrations of phthalate esters and particle-phase concentrations. In addition, temperature has a strong negative effect on the gas/particle partition coefficient (K_p), and an order of magnitude difference in K_p was observed between 12.5 and 40 °C. There are exponential decay laws between K_p and the absolute temperature. However, a smaller effect of humidity than of temperature on K_p was revealed, and no obvious law was found. Moreover, K_p of compounds with larger molecular weights are more obviously influenced by the variations in environmental factors. This study is of positive significance for reducing the health risks of PAEs by guiding the regulation of indoor environmental parameters.