Abstract:Settled dust is an important medium
for semivolatile organic compound
(SVOC) transport indoors. Understanding the mechanism of interaction
between SVOCs and settled dust can greatly improve the exposure assessment.
This study develops an analytical model to elucidate the mechanism
of direct contact between SVOC sources and settled dust. The model
incorporates the adsorption of SVOCs onto indoor surfaces, which was
ignored in previous numerical models. Based on this model, a hybrid
optimization method is applie… Show more
“…OPEs readily distribute among multiple indoor environmental mediums, including gas phase, airborne particles, dust phase, and indoor surfaces. , In the present study, three partitioning processes of gas-phase OPEs ( y ) were considered: airborne particle/gas (P/G, K P ), settled dust/gas (D/G, K D ), and surface/gas (S/G, K S ). The mechanisms governing the emission and distribution of OPEs in a room are illustrated in Figure S3.…”
Source characteristics and health risks of indoor organophosphate esters (OPEs) are limited by the lack of knowledge on emission processes. This study attempted to integrate the contents and emissions of OPEs from indoor building materials to assess human health effects. Thirteen OPEs were investigated in 80 pieces of six categories of building materials. OPEs are ubiquitous in the building materials and ∑ 13 OPE contents varied significantly (p < 0.05) from 72.8 ng/g (seam agent) to 109,900 ng/g (wallpaper). Emission characteristics of OPEs from the building materials were examined based on a microchamber method. Depending on the sample category, the observed initial area-specific emission rates of ∑ 13 OPEs varied from 154 ng/m 2 /h (carpet) to 2760 ng/m 2 /h (wooden floorboard). Moreover, the emission rate model was developed to predict the release levels of individual OPEs, quantify source contributions, and assess associated exposure risks. Source apportionments of indoor OPEs exhibited heterogeneities in multiple environmental media. The joint OPE contribution of wallpaper and wooden floorboard to indoor dust was up to 94.8%, while latex paint and wooden floorboard were the main OPE contributors to indoor air (54.2%) and surface (76.1%), respectively. Risk assessment showed that the carcinogenic risks of tris(2-chloroethyl) phosphate (3.35 × 10 −7 ) were close to the acceptable level (1 × 10 −6 ) and deserved special attention.
“…OPEs readily distribute among multiple indoor environmental mediums, including gas phase, airborne particles, dust phase, and indoor surfaces. , In the present study, three partitioning processes of gas-phase OPEs ( y ) were considered: airborne particle/gas (P/G, K P ), settled dust/gas (D/G, K D ), and surface/gas (S/G, K S ). The mechanisms governing the emission and distribution of OPEs in a room are illustrated in Figure S3.…”
Source characteristics and health risks of indoor organophosphate esters (OPEs) are limited by the lack of knowledge on emission processes. This study attempted to integrate the contents and emissions of OPEs from indoor building materials to assess human health effects. Thirteen OPEs were investigated in 80 pieces of six categories of building materials. OPEs are ubiquitous in the building materials and ∑ 13 OPE contents varied significantly (p < 0.05) from 72.8 ng/g (seam agent) to 109,900 ng/g (wallpaper). Emission characteristics of OPEs from the building materials were examined based on a microchamber method. Depending on the sample category, the observed initial area-specific emission rates of ∑ 13 OPEs varied from 154 ng/m 2 /h (carpet) to 2760 ng/m 2 /h (wooden floorboard). Moreover, the emission rate model was developed to predict the release levels of individual OPEs, quantify source contributions, and assess associated exposure risks. Source apportionments of indoor OPEs exhibited heterogeneities in multiple environmental media. The joint OPE contribution of wallpaper and wooden floorboard to indoor dust was up to 94.8%, while latex paint and wooden floorboard were the main OPE contributors to indoor air (54.2%) and surface (76.1%), respectively. Risk assessment showed that the carcinogenic risks of tris(2-chloroethyl) phosphate (3.35 × 10 −7 ) were close to the acceptable level (1 × 10 −6 ) and deserved special attention.
The concern about indoor air quality in various micro-environments has been on the rise as buildings are vulnerable to an array of contaminants generated from various sources. The study aims to investigate and highlight the pollutant sources and composition in middle-income residential spaces through a case study approach. With large migration from small towns and saturation of megacities, the middle-income population in tier-2 cities in India is on the rise, raising concern about the well-being of the dense urban population. It involves a careful selection of typical MIG housing to identify major pollution sources from outdoor and indoor environments. The focus lies in the findings stemming from continuous air quality monitoring of PM10, PM2.5, SO2, NO2, HCHO, TVOC, CO and C6H6 and an in-depth physio-chemical analysis facilitated by Fourier transform infrared (FTIR), Analytical Scanning Electron Microscope (A-SEM) and energy-dispersive X-ray (EDX) spectroscopy of settled household dust. Analysis unveiled indoor PM2.5 concentrations of 21.93 µg/m3, exceeding WHO standards, whereas, TVOC concentrations were higher indoors than outdoors. Stark disparities between indoor and outdoor dust compositions and sources were also observed. Despite limitations, it provides a portrait of middle-income housing conditions, offering insights for interventions and future research on indoor air quality challenges.
“…By comparing the stability and searching ability of different nonlinear fitting algorithms, we apply a hybrid optimization method by coupling particle swarm optimization with ant colony optimization, to perform nonlinear fitting on the gas-phase 6-MHO concentrations to obtain the two key parameters. The hybrid optimization method has been shown to be able to obtain relatively stable results when used to determine the key parameters of VOCs and SVOCs from building and vehicle cabin materials. ,− The details of the hybrid optimization method, including the iterative equations, parameter settings, and calculation steps, are given in SI Section S2.…”
Deep understanding of the chemical reaction and physical
transport
characteristics of 6-methyl-5-hepten-2-one (6-MHO) in different phases
(e.g., skin, clothing) is important for modeling the indoor squalene/ozone
reaction. In this study, we make the first attempt to accurately measure
the physical transport parameters, i.e., the diffusion coefficient
(D
m) and partition coefficient (K) of 6-MHO in different clothing (jeans, nylon, pure cotton
T-shirt). A ventilated–airtight–ventilated testing procedure
was designed, and relevant experiments were performed in 30 L small-scale
chambers. The key parameters of 6-MHO (D
m and K) are determined by nonlinearly fitting the
measured gas-phase concentration data with physical model using a
hybrid optimization method. The high fitting accuracy (R2 > 0.93), good replication (relative deviations of determined D
m and K less than 16% for duplicated
experiments), and further sensitivity analysis demonstrate the reliability
and robustness of the method. In addition, the variation of the key
parameters of 6-MHO in the pure cotton T-shirt with temperature (in
the range of 20–37 °C) is investigated. Results indicate
that D
m increases while K decreases with increasing temperature. This study provides some
of the fundamental data for characterizing the squalene/ozone reaction
and should be helpful for the subsequent dermal exposure in realistic
indoor environments.
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