Indoor Semi-volatile Organic Compounds Research Articles

Emissions of Semi-Volatile Organic Compounds from Architectural Coatings and Polyvinyl Chloride Floorings: Microchamber Method.

Semi-volatile organic compounds (SVOCs) are modern chemical substances that are present in large quantities in indoor environments. Understanding the emission of SVOCs from building materials is essential to identify the main sources of indoor SVOCs and to improve indoor air quality. In this study, a reference method employing custom-designed microchambers (630 mL) was optimized by improving the structure of the gas path and adding polytetrafluoroethylene inner coating to the chamber. After optimization, the recoveries of the microchamber method were significantly improved (75.4-96.7%), and the background in the microchamber was greatly reduced (<0.02 μg/h). By using the microchamber method, 33 SVOCs (including two alkanes, one aromatic, one nitrogen compound, and twenty-nine oxygenated compounds) and 32 SVOCs (including seven alkanes, eight aromatics, and seventeen oxygenated compounds) were detected in the emissions of the architectural coating and the PVC flooring samples, respectively. The area-specific emission rates (SERa) of total SVOCs emitted from architectural coatings and PVC floorings were in the range of 4.09-1309 μg/m2/h) (median: 10.3 μg/m2/h) and 0.508-345 μg/m2/h (median: 11.9 μg/m2/h), respectively. Propanoic acid had the highest SERa (3143 μg/m2/h) in architectural coatings, while methylbenzene (345 μg/m2/h), 2-methylnaphthalene (65.2 μg/m2/h), and naphthalene (60.3 μg/m2/h) were main SVOCs emitted from PVC floorings. Meanwhile, the average second-stage (adsorbed phase) emission mass of the total SVOCs accounts for 66.3% and 47.3% in architectural coatings and PVC floorings, respectively, suggesting that the SVOCs emitted from building materials have a strong tendency to be absorbed on the surface of the room, e.g., the interior wall, the desk or even the skin.

An in-situ versatile screening method for identifying SVOC sources in indoor environments

Indoor semivolatile organic compounds (SVOCs) pose a substantial threat to human health. However, identifying the sources of these emissions has been challenging owing to the scarcity of convenient and practical on-site methodologies. Herein, a novel method for source screening was proposed using aluminum silicate sampling strips to adsorb SVOCs from the surface air of indoor materials. The adsorbed SVOC levels indicate the emission intensity of these materials into indoor environments. Additionally, compact sampling strips can be readily fixed to any vertical surface using a static sticker, facilitating the characterization of various materials in practical settings. Laboratory-simulated experiments demonstrated the capability of the proposed method to differentiate between source and non-source materials within a 10-cm distance in the same space. In practical scenarios, the primary emission sources identified via this method exhibited a consistent correlation with the contents of the corresponding materials obtained from the traditional solvent-extraction method. As the adsorbed SVOCs were directly transferred to a GC–MS through thermal desorption instead of the solvent-extraction procedure, the proposed method demonstrated several-fold improvements in analytical sensitivity and efficiency. Using this versatile screening technique, some emerging and important SVOC species were identified within specific indoor materials. Eliminating these sources has been demonstrated as an effective approach to mitigate SVOC pollution. Overall, the proposed method offers a powerful tool for managing indoor pollutants and safeguarding human health.

Characterizing PM2.5 Emissions and Temporal Evolution of Organic Composition from Incense Burning in a California Residence.

The chemical composition of incense-generated organic aerosol in residential indoor air has received limited attention in Western literature. In this study, we conducted incense burning experiments in a single-family California residence during vacancy. We report the chemical composition of organic fine particulate matter (PM2.5), associated emission factors (EFs), and gas-particle phase partitioning for indoor semivolatile organic compounds (SVOCs). Speciated organic PM2.5 measurements were made using two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC×GC-HR-ToF-MS) and semivolatile thermal desorption aerosol gas chromatography (SV-TAG). Organic PM2.5 EFs ranged from 7 to 31 mg g-1 for burned incense and were largely comprised of polar and oxygenated species, with high abundance of biomass-burning tracers such as levoglucosan. Differences in PM2.5 EFs and chemical profiles were observed in relation to the type of incense burned. Nine indoor SVOCs considered to originate from sources other than incense combustion were enhanced during incense events. Time-resolved concentrations of these SVOCs correlated well with PM2.5 mass (R2 > 0.75), suggesting that low-volatility SVOCs such as bis(2-ethylhexyl)phthalate and butyl benzyl phthalate partitioned to incense-generated PM2.5. Both direct emissions and enhanced partitioning of low-volatility indoor SVOCs to incense-generated PM2.5 can influence inhalation exposures during and after indoor incense use.

Thermal desorption-based method for quantifying semi-volatile organic compounds in house dust: Method development and evaluation

As an important storage medium of semi-volatile organic compounds (SVOC) in indoor environments, house dust has been extensively used to assess the pollution level of indoor SVOC. SVOC in house dust are commonly quantified using solvent-extraction methods, which are however solvent-consuming, time-consuming and laborious. Thermal desorption (TD, solvent-free and easy-to-use) is a good alternative to solvent extractions, but its performance for analyzing house dust is still unverified. Therefore, we proposed a TD-based method for quantifying SVOC in house dust by incorporating the TD technique with GC-MS. Laboratory experiments (48 samples with high SVOC concentrations) and field-test experiments (12 samples with low SVOC concentrations) were performed to justify the proposed method by comparing its results to those of a traditional solvent-extraction method (Soxhlet extraction). For laboratory dusts, the accuracy (relative deviation &lt; 20%) and repeatability (relative standard deviation &lt; 13%) of the TD-based method were comparable to the solvent-extraction method. For field-test dusts, higher SVOC concentrations were typically obtained by the TD-based method, implying its superior performance. These results gave evident confidence in the performance of the TD-based method, which facilitated the simple, solvent-free and accurate quantification of SVOC in house dust.

Gas-Particle Partitioning of Semivolatile Organic Compounds in a Residence: Influence of Particles from Candles, Cooking, and Outdoors.

Semivolatile organic compounds (SVOCs) represent an important class of indoor pollutants. The partitioning of SVOCs between airborne particles and the adjacent air influences human exposure and uptake. Presently, little direct experimental evidence exists about the influence of indoor particle pollution on the gas-particle phase partitioning of indoor SVOCs. In this study, we present time-resolved gas- and particle-phase distribution data for indoor SVOCs in a normally occupied residence using semivolatile thermal desorption aerosol gas chromatography. Although SVOCs in indoor air are found mostly in the gas phase, we show that indoor particles from cooking, candle use, and outdoor particle infiltration strongly affect the gas-particle phase distribution of specific indoor SVOCs. From gas- and particle-phase measurements of SVOCs spanning a range of chemical functionalities (alkanes, alcohols, alkanoic acids, and phthalates) and volatilities (vapor pressures from 10-13 to 10-4 atm), we find that the chemical composition of the airborne particles influences the partitioning of individual SVOC species. During candle burning, the enhanced partitioning of gas-phase SVOCs to indoor particles not only affects the particle composition but also enhances surface off-gassing, thereby increasing the total airborne concentration of specific SVOCs, including diethylhexyl phthalate.

Role of dust loading in dynamic transport of semi-volatile organic compounds (SVOCs) into house dust: From multilayer to monolayer

House dust is an important transfer and storage medium of semi-volatile organic compounds (SVOCs) in indoor environments. Dust loading (dust weight per surface area) has been identified as a key factor affecting SVOC transport into dust. As the increment of dust loading, house dust can be classified as monolayer and multilayer dusts. Most of existing studies have only investigated the multilayer dust though the monolayer dust is also ubiquitous on indoor surfaces, precluding the comprehensive explanation of dust loading effects. Therefore, this study proposed a mass transfer model to describe SVOC transport into house dust by differentiating SVOC diffusion distance in monolayer and multilayer dusts. High consistence between model predictions and measurements justified the model performance. Characteristic parameters of SVOCs in house dust, dust-air partition coefficient (Kd) and diffusion coefficient (Dd), were determined by fitting the model to the measurements. Further analysis indicated that: (1) SVOC transport mechanism in monolayer dust (dust size-dependent) was different from that in multilayer dust (dust loading-dependent), and (2) dust loading (in the range of 2.55–30 g/m2) might have insignificant effects on Kd. This study should be helpful for the deep understanding of SVOC transport into house dust and the accurate exposure assessment of indoor SVOCs.

Strong temperature influence and indiscernible ventilation effect on dynamics of some semivolatile organic compounds in the indoor air of an office.

Many manmade organic air pollutants are semivolatile and primarily used and exposed indoors. It remains unclear how indoor environmental parameters affect indoor air dynamics of semivolatile organic compounds (SVOCs) in real-world indoor conditions, which directly relates to human exposure. By making time-resolved SVOC measurements over multiple weeks in an office, we characterized the indoor air dynamics of six representative SVOCs which were mainly present in the gas phase and of indoor origins, and investigated the effects of the temperature and ventilation rate. The six species include di-isobutyl phthalate and di-n-butyl phthalate, as well as two n-alkanes and two siloxanes. Airborne concentrations of all six SVOCs responded strongly and quickly to changes in the indoor temperature. The temperature dependence of individual species can be well fitted in the form of the van't Hoff equation, and explained 65-86% of the observed variation in the logarithm-transformed concentrations. In contrast, increasing the ventilation rate by a factor of 3-5 for hours at a constant temperature had no discernible influence on the SVOC concentrations. Further kinetic modeling analysis suggests that the observed fast temperature response and indiscernible ventilation effect are both associated with SVOC sorption onto indoor surfaces, which dramatically slows the response of SVOC concentration to changes in the ventilation rate and speeds up the response to changes in the temperature. These results highlight the importance of sorption reservoirs on regulating indoor SVOC dynamics and also have important implications for controlling and assessing indoor air exposure to SVOCs.

Steady-State Based Model of Airborne Particle/Gas and Settled Dust/Gas Partitioning for Semivolatile Organic Compounds in the Indoor Environment.

Indoor semivolatile organic compounds (SVOCs), present in the air, airborne particles, settled dust, and other indoor surfaces, can enter the human body through several pathways. Knowing the partitioning between gaseous and particulate phases is important in identifying specific pathway contributions and thereby accurately assessing human exposure. Numerous studies have developed equilibrium equations to predict airborne particle/gas (P/G) partitioning in air (KP) and dust/gas (D/G) partitioning in settled dust (KD). The assumption that P/G and D/G equilibria are instantaneous for airborne and settled dust phases, commonly adopted by current indoor fate models, is not likely valid for compounds with high octanol-air partition coefficients (KOA). Here, we develop steady-state based equations to predict KP and KD in the indoor environment. Results show that these equations perform well and are verified by worldwide monitoring data. It is suggested that instantaneous steady state could work for P/G and D/G partitioning of SVOCs in indoor environments, and the equilibrium is just a special case of the steady state when log KOA < 11.38 for P/G partitioning and log KOA < 10.38 for D/G partitioning. These newly developed equations and methods provide a tool for more accurate assessment for human exposure to SVOCs in the indoor environment.

Occurrence, exposure and risk assessment of semi-volatile organic compounds in Chinese homes

Indoor semi-volatile organic compounds (SVOCs) can have a significant impact on human health. Previous studies involved the detection of limited classes of indoor SVOCs in different regions of China. However, overall indoor pollution profiles and the associated health risks via multiple exposure pathways remain unclear. High-throughput screening of SVOCs would help clarify the overall indoor pollution status and identify high-risk pollutants. We collected indoor air and dust samples from 35 Chinese homes and investigated the occurrence of a wide range of SVOCs. Ninety-seven SVOCs including phthalate esters (PAEs), polycyclic aromatic hydrocarbons (PAHs), organophosphate esters, alcohols, fatty acids, phenols, etc., were detected in the air (total concentrations: 0.13–48 μg/m3; median: 3.4 μg/m3) and dust (total concentrations: 120–1500 μg/g; median: 490 μg/g) samples. PAEs were the most abundant, accounting for 55.3 ± 28.6% and 43.4 ± 16.9% of the total SVOC concentrations in the air and dust samples respectively. Human exposure and health risks of 34 SVOCs with detection frequencies >10% were assessed based on inhalation, ingestion and dermal absorption of SVOCs from air and dust by infants and adults. In the case of indoor SVOCs with log Koa < 9, inhalation and dermal contact with air was >90% for adults and >69% for infants. The following five SVOCs in air samples posed significant non-carcinogenic risks and are listed based on their decreasing risk level: dibutyl phthalate > phenanthrene > stearic acid > methyl palmitate > lauryl alcohol. Four PAHs with 2–4 rings posed potential carcinogenic risks, with phenanthrene exceeding the acceptable risk level of 10−4. The high risks posed by SVOCs were due to inhalation exposure. Therefore, keeping the air concentrations of SVOCs, especially that of PAEs and PAHs under check would greatly benefit human health in indoor environments.

Quantitative Analysis of Indoor Gaseous Semi-Volatile Organic Compounds Using Solid-Phase Microextraction: Active Sampling and Calibration

Semi-volatile organic compounds (SVOCs) are important pollutants in indoor environments. Quantification of gaseous SVOC concentrations is essential to assess the pollution levels. Solid-phase microextraction (SPME) is considered to be an attractive sampling technique with merits, including simplicity of use, rapid sampling, and solvent free. However, the applications of SPME for sampling gaseous SVOCs are often limited by the fluctuating velocity of indoor air (leading to an unstable sampling rate) and the uncertainties associated with the traditional calibration of SPME. Therefore, we established an SPME-based active sampler to ensure the stable sampling of SVOCs in fluctuating air and developed a two-step calibration method based on the sampling principle of SPME. The presented method and a traditional method (sorbent tubes packed with Tenax TA) were simultaneously used to measure SVOC concentrations in an airstream generated in experiments. Three typical indoor SVOCs, diisobutyl phthalate (DiBP), tris (1-chloro-2-propyl) phosphate (TCPP), and benzyl butyl phthalate (BBzP) were chosen as the analytes. Mean concentrations measured by SPME agreed well with the sorbent tubes (relative deviations &lt;12%), supporting the feasibility of the presented method. Further studies are expected to facilitate the application of the presented method (especially the problem associated with the sampling-tube loss of low volatile SVOCs).

A modular mechanistic framework for estimating exposure to SVOCs: Next steps for modeling emission and partitioning of plasticizers and PFAS.

Estimates of human exposure to semi-volatile organic compounds (SVOCs) such as phthalates, phthalate alternatives, and some per- and polyfluoroalkyl substances (PFAS) are required for the risk-based evaluation of chemicals. Recently, a modular mechanistic modeling framework to rapidly predict SVOC emission and partitioning in indoor environments has been presented, in which several mechanistically consistent source emission categories (SECs) were identified. However, not all SECs have well-developed emission models. In addition, data on model parameters are missing even for frequently studied SVOCs. These knowledge gaps impede the comprehensive prediction of the fate of SVOCs indoors. In this paper, sets of high-priority phthalates, phthalate alternatives, and PFAS were identified based on chemical occurrence indoors and additional selection criteria. These high-priority chemicals served as the basis for exploring model parameter availability for existing indoor SVOC emission and partitioning models. The results reveal that additional experimental and modeling work is needed to fully understand the behavior of SVOCs indoors and to predict exposures with greater confidence and lower uncertainty. Modeling approaches to fill some of the identified gaps are proposed. The prioritized sets of chemicals and proposed new modeling approaches will help guide future research. The inclusion of polar phases in the framework will further expand its applicability and scope. IMPACT STATEMENT: This paper compiles data on high-priority chemicals commonly found indoors and information on the availability of applicable models and model parameters to predict emission, partitioning, and subsequent exposure to these chemicals. Modeling approaches for a selection of the missing SECs (source emission categories) are proposed, to illustrate the path forward. The comprehensive data set helps inform researchers, exposure assessors, and policy makers to better understand the state of the science regarding modeling of indoor exposure to semi-volatile organic compounds (SVOCs) and per- and polyfluoroalkyl substances (PFAS).

Numerical Investigation on the Effect of Ventilation on the Distribution of Phthalate Esters in the Residential Environment

Semi-volatile organic compounds (SVOCs), such as phthalates and brominated flame retardants, is a kind of emerged pollutants due to wide application in indoor environment. Certain indoor SVOCs have been found to be associated with various adverse health effects, attracting large attentions of researchers. Due to relatively low vapor pressure, SVOCs are easily adsorbed on various surfaces including particles. Therefore, airborne SVOCs are always simultaneously presented in the gas-phase and particle-phase. Ventilation is an important means to improve indoor air quality. Different forms of indoor air distribution will affect the distribution of indoor pollutants and further affect the exposure to the human body. Therefore, in this paper, we selected Di (2-ethylhexyl) phthalate (DEHP) as the target compound and employed computational fluid dynamics (CFD) technique to simulate the emission of DEHP and the concentration distribution with different phases in a modeled room. Euler-Lagarian model is applied to simulate flow field, particle tracks and UDF (user defined function) was implemented to describe the dynamic adsorption of DEHP by the suspended particles. Furthermore, the effect of location of vent and airflow rate on indoor fate of DEHP were discussed and the effect of particle age on indoor fate of DEHP was also investigated.

Surface-Enhanced Raman Sensing of Semi-Volatile Organic Compounds by Plasmonic Nanostructures.

Facile detection of indoor semi-volatile organic compounds (SVOCs) is a critical issue to raise an increasing concern to current researchers, since their emissions have impacted the health of humans, who spend much of their time indoors after the recent incessant COVID-19 pandemic outbreaks. Plasmonic nanomaterial platforms can utilize an electromagnetic field to induce significant Raman signal enhancements of vibrational spectra of pollutant molecules from localized hotspots. Surface-enhanced Raman scattering (SERS) sensing based on functional plasmonic nanostructures has currently emerged as a powerful analytical technique, which is widely adopted for the ultra-sensitive detection of SVOC molecules, including phthalates and polycyclic aromatic hydrocarbons (PAHs) from household chemicals in indoor environments. This concise topical review gives updated recent developments and trends in optical sensors of surface plasmon resonance (SPR) and SERS for effective sensing of SVOCs by functionalization of noble metal nanostructures. Specific features of plasmonic nanomaterials utilized in sensors are evaluated comparatively, including their various sizes and shapes. Novel aptasensors-assisted SERS technology and its potential application are also introduced for selective sensing. The current challenges and perspectives on SERS-based optical sensors using plasmonic nanomaterial platforms and aptasensors are discussed for applying indoor SVOC detection.

Catalytic oxidation of dimethyl phthalate over titania-supported noble metal catalysts

Semi-volatile organic compounds (SVOCs) are organic compounds with the boiling point ranging between 240/260 ℃ and 380/400 ℃. Detailed knowledge regarding catalytic removal of SVOCs from indoor environment is very limited as it remains challenge to explore such reaction due to the viscosity nature of target contaminants. Here, we established a facile methodology to explore the heterogeneous catalytic oxidation reaction of dimethyl phthalate (DMP), a model SVOC, over the surface of supported catalyst. DMP was found to be gradually oxidized over the surface of titania supported catalysts including palladium (Pd), platinum and ruthenium with increasing temperature. The cleavage of side chain of DMP occurs at 75 ℃ over the surface of Pd/TiO2, which is significantly lower than that of the other two catalysts. Carbon dioxide was observed as the main product of the catalytic oxidation reaction. However, aromatic products and small molecule products were still observed as side-product in different temperature range. Density functional theory calculations further show that DMP can react with reactive oxygen species to form phthalic acid. While the cleavage of the DMP side chain occurs to form products such as methyl benzoate. This work thus provides basic knowledge about indoor SVOCs catalytic oxidation removal.

Numerical investigation of dust sedimentation effects on wall adsorption of indoor SVOC by the immersed boundary-lattice Boltzmann method

In this work the lattice Boltzmann method (LBM) is used to investigate semi-volatile organic compounds (SVOCs) mass transfer under the influence of particle sedimentation in the boundary-layer scale region. For the fluid-particle interaction, the direct-forcing immersed boundary (IB) method is applied to calculate the hydro-dynamic force. A mass-transfer IB method is employed to calculate the fluid-particle SVOC flux. Particles with zero and saturated initial-concentrations are studied to investigate the effects of clean and polluted particles. Effects of fluid/particle equilibrium coefficients, as well as particle diameters, are discussed. Wall adsorptions under the influence of multiple particles are also investigated. Numerical simulations reveal that a particle always intensifies wall adsorption independent of its initial SVOC concentration. The influences of particles on wall adsorption are associated with disturbance effect (disturbing air due to particle moving) and medium effect (SVOC mass transfer between particles and their surrounding air). Disturbance effect of clean particles overwhelms their medium effect while medium effect is dominant for saturated particles. Disturbance effect and medium effect both increase with particle diameter, and medium effect is more sensitive to particle diameter. Competitive adsorption occurs in presence of a number of particles and has an indirect impact on wall adsorption.

Surface Emissions Modulate Indoor SVOC Concentrations through Volatility-Dependent Partitioning.

Measurements by semivolatile thermal desorption aerosol gas chromatography (SV-TAG) were used to investigate how semivolatile organic compounds (SVOCs) partition among indoor reservoirs in (1) a manufactured test house under controlled conditions (HOMEChem campaign) and (2) a single-family residence when vacant (H2 campaign). Data for phthalate diesters and siloxanes suggest that volatility-dependent partitioning processes modulate airborne SVOC concentrations through interactions with surface-laden condensed-phase reservoirs. Airborne concentrations of SVOCs with vapor pressures in the range of C13 to C23 alkanes were observed to be correlated with indoor air temperature. Observed temperature dependencies were quantitatively similar to theoretical predictions that assumed a surface-air boundary layer with equilibrium partitioning maintained at the air-surface interface. Airborne concentrations of SVOCs with vapor pressures corresponding to C25 to C31 alkanes correlated with airborne particle mass concentration. For SVOCs with higher vapor pressures, which are expected to be predominantly gaseous, correlations with particle mass concentration were weak or nonexistent. During primary particle emission events, enhanced gas-phase emissions from condensed-phase reservoirs partitioned to airborne particles, contributing substantially to organic particulate matter. An emission event related to oven-usage was inferred to deposit siloxanes in condensed-phase reservoirs throughout the house, leading to the possibility of reemission during subsequent periods with high particle loading.

A novel model for predicting the semivolatile organic compound partition coefficient of multicomponent airborne particles

Semivolatile organic compounds (SVOCs) are highly susceptible to sorption by particles, so the presence of particles will have a significant impact on indoor SVOC distribution. The partition coefficient of SVOCs between the air and particles was closely related to indoor environmental parameters, particle composition, and physical structure. However, owing to the complexity of indoor particle composition and the variety of SVOCs, theoretical models of the particle partition coefficient are still not comprehensive in characterizing the SVOC sorption process by different components, and most only consider the sorption of elemental carbon and organic carbon. Studies have demonstrated that inorganic particles have nonnegligible sorption capacity on SVOCs. In this study, experimental results in the literature were compared with the theoretical values predicted by the widely used equilibrium model of the SVOC particle/gas partition coefficient. It was found that neglecting the inorganic components in particles led to a low predictive value of the partition coefficient. Therefore, based on the two-parameter equilibrium model, a novel model considering the sorption of SVOCs on inorganic substances was proposed. This model could describe the formation mechanism of the particle/air partition coefficient more comprehensively, and the experimental data in many relevant studies were used to verify the model. In addition, based on this model, the quantitative relationship between particle property and its sorption of SVOCs was calculated and analyzed. This study aimed to improve the predictive accuracy of indoor SVOC concentrations and help to make more accurate estimates of the risk of human health exposure in further research.

Linking past uses of legacy SVOCs with today's indoor levels and human exposure

Semivolatile organic compounds (SVOCs) emitted from consumer products, building materials, and indoor and outdoor activities can be highly persistent in indoor environments. Human exposure to and environmental contamination with polychlorinated biphenyls (PCBs) was previously reported in a region near a former PCB production facility in Slovakia. However, we found that the indoor residential PCB levels did not correlate with the distance from the facility. Rather, indoor levels in this region and those reported in the literature were related to the historic PCB use on a national scale and the inferred presence of primary sources of PCBs in the homes. Other SVOCs had levels linked with either the activities in the home, e.g., polycyclic aromatic hydrocarbons (PAHs) with wood heating; or outdoor activities, e.g., organochlorine pesticides (OCPs) with agricultural land use and building age. We propose a classification framework to prioritize SVOCs for monitoring in indoor environments and to evaluate risks from indoor SVOC exposures. Application of this framework to 88 measured SVOCs identified several PCB congeners (CB-11, -28, -52), hexachlorobenzene (HCB), benzo(a)pyrene, and γ-HCH as priority compounds based on high exposure and toxicity assessed by means of toxicity reference values (TRVs). Application of the framework to many emerging compounds such as novel flame retardants was not possible because of either no or outdated TRVs. Concurrent identification of seven SVOC groups in indoor environments provided information on their comparative levels and distributions, their sources, and informed our assessment of associated risks.

Lattice Boltzmann method simulation of SVOC mass transfer with particle suspensions

Semi-volatile organic compounds (SVOC) exist in indoor air at very low concentrations (usually less than 100 µg/m3), but do great harm to human health. SVOC pollutants transfer in indoor air with suspended particles so complicatedly that traditional experimental methods are hardly to reveal the mass-transfer mechanism. This study employs Lattice Boltzmann method (LBM) to investigate the mass transfer behaviours of two-phase SVOC pollutants (gas- and particle-phase), and compare two widely-used gas/particle partition models (the instantaneous equilibrium model and the dynamic model). LBM is used to simulate the fluid flows and SVOC mass transfer, and the cell automation (CA) probabilistic model is applied to simulate the particle transport. The interaction between the gas- and particle-phase of SVOC is considered in the source term of the Lattice Boltzmann equations. One particle is firstly simulated in order to focus on the particle-phase concentration, then a large number of particles are simulated to focus on the effect of particles on the concentration field of SVOC. The simulation results show: (i) particles in the instantaneous equilibrium model for gas/particle partition always help gas-phase SVOC transport in indoor air by particle-mediation effect, while such an effect in the dynamic model is greatly determined by Kp and residence time of particles; (ii) particle-mediation effect can also increase the emission rate, and a non-uniform distribution of particles predicted by our numerical model indicates that such an additional emission rate increases exponentially with particle concentration, because a small number of particles have little possibility of approaching emission surface. (iii) Our numerical model can effectively estimate SVOC concentration in the presence of airborne particles by tracking each particle. These results highlight the roles of airborne particles in the transport of indoor SVOC pollutants, and are expected to be useful to consider dust deposition and resuspension when particles are in a realistic size distribution.

Effect of residential air cleaning interventions on risk of cancer associated with indoor semi-volatile organic compounds: a comprehensive simulation study

Human exposure to multiphase semi-volatile organic compounds (SVOCs) via multiple routes has been associated with health risks. Residential air cleaning interventions remove SVOCs adsorbed on airborne particles, which subsequently affects indoor concentrations of SVOCs in other phases. We aimed to investigate the effect of residential air cleaning interventions on the overall cancer risk associated with multiphase SVOCs. We simulated concentrations of eight multiphase SVOCs (including seven polycyclic aromatic hydrocarbons [PAHs] and di(2-ethylhexyl) phthalate [DEHP]) using a kinetic partition mass balance model for three exposure scenarios: naturally ventilated residences without intervention (scenario 1), naturally ventilated residences with portable air purifiers (scenario 2), and mechanically ventilated residences with air filtration units (scenario 3). We converted indoor concentrations of the individual PAHs into indoor concentrations of equivalent benzo[a]pyrene (BaPeq) using the BaP cancer potency equivalent factor for each PAH. We estimated indoor exposure to SVOCs via inhalation, dermal absorption, and ingestion. For each scenario, we calculated the incremental lifetime cancer risk (ILCR) associated with indoor exposure to each SVOC via the three routes and the total ILCR (all three routes combined). Mean total ILCRs associated with exposure to BaPeq were 4·42 × 10-6 (SD 2·84) for scenario 1, 2·36 × 10-6 (1·53) for scenario 2, and 4·88 × 10-6 (4·86) for scenario 3. Mean total ILCRs associated with exposure to DEHP were 3·61 × 10-6 (3·60) for scenario 1, 7·51 × 10-7 (5·34) for scenario 2, and 1·48 × 10-5 (2·02) for scenario 3. Ingestion of settled dust was the most important contributor to the total ILCR for both BaPeq and DEHP in all the studied scenarios. The large-scale use of mechanical ventilation systems in urban residences in China needs to be evaluated owing to their potential exacerbation of the cancer risks associated with common indoor SVOCs. National Key Project of the Ministry of Science and Technology and Natural Science Foundation of China.