Direct and Air-Mediated Transfer of Labeled SVOCs from Indoor Sources to Dust

Bis(2-ethylhexyl) phthalate transfer from polyvinyl chloride sheet to several kinds of particles

Bis(2-ethylhexyl) phthalate (DEHP) transfer from a polyvinyl chloride (PVC) sheet to 9 kinds of particles, namely, polyethylene particles (1-10, 45-53, 90-106 μm), soda lime glass particles (1-38, 45-53, 90-106 μm), black forest soil, carbon black, and cotton linter, for the particle weights of 0.3, 1, 3, and 12 mg/cm2, were determined for 1, 3, 7, and 14 days using a passive flux sampler (PFS), as well as standard dust. Transfer amounts to small polyethylene particles (1-10 μm), black forest soil, and carbon black were large (8.5, 16, and 48 μg/mg-particle, respectively, for 0.3 mg/cm2 for 14 days) and were similar to standard house dust (35 μg/mg-particle). On the other hand, transfer amount to large polyethylene particles (0.056-0.12 μg/mg-particle), soda lime glass (0.18-0.31 μg/mg-particle), and cotton linter (0.42-0.78 μg/mg-particle) were much lower. The DEHP transfer amount to the particles was proportional to the surface area of the particles, but not associated with the organic content. The DEHP transfer amount per surface area to small polyethylene particles was larger than that of other particles, suggesting the contribution of absorption into the polyethylene particle. However, for the larger polyethylene particles with different manufacturing process that may have different crystallinity, the contribution of absorption was small. The amount of DEHP transferred to soda lime glass did not differ from 1 to 14 days, suggesting that an adsorption equilibrium was reached after 1 day. The estimated value of particle/gas partition coefficients of DEHP, Kpg, of small polyethylene, black forest soil and carbon black were much higher (3.6, 7.1, and 18 m3/mg, respectively) than those of large polyethylene and soda lime glass particles (0.028-0.11 m3/mg).

Atmospheric micro (nano) plastics: future growing concerns for human health

ABSTRACT

Plastics are an integral but largely inconspicuous part of daily human routines. The present review paper uses cross-disciplinary scientific literature to examine and assess the possible effects of nanoplastics (NPs) concerning microplastics (MPs) on human health and summarizes crucial areas for future research. Although research on the nature and consequences of MPs has seen a substantial rise, only limited studies have concentrated on the atmospheric nanosized polymeric particles. However, due to the intrinsic technological complications in separating and computing them, their existence has been difficult to determine correctly. There is a consensus that these are not only existing in the environment but can get directly released or as the outcome of weathering of larger fragments, and it is believed to be that combustion can be the tertiary source of polymeric particles. NPs can have harmful consequences on human health, and their exposure may happen via ingestion, inhalation, or absorption by the skin. The atmospheric fallout of micro (nano) plastics may be responsible for contaminating the environment. Apart from this, different drivers affect the concentration of micro (nano) plastics in every environment compartment like wind, water currents, vectors, soil erosion, run-off, etc. Their high specific surface for the sorption of organic pollutions and toxic heavy metals and possible transfer between organisms at different nutrient levels make the study of NPs an urgent priority. These NPs could potentially cause physical damage by the particles themselves and biological stress by NPs alone or by leaching additives. However, there is minimal understanding of the occurrence, distribution, abundance, and fate of NPs in the environment, partially due to the lack of suitable techniques for separating and identifying NPs from complex environmental matrices.

HIGHLIGHTS

Micro (nano) plastics generated may reach the soil, water, and atmospheric compartments.Atmospheric currents serve as a way to transport, leading to micro (nano) plastics pollution.Exposure to micro (nano) plastics may happen via ingestion, inhalation, or absorption by the skin.Nanoplastics may be environmentally more harmful than other plastic particles; the focus should be on defining the exact size range.Visual classification of micro (nano) plastics is poor in reliability and may also contribute to microplastics being misidentified.

Partition of phthalates among air, PM2 .5 , house dust and skin in residential indoor environments

As a group of typical endocrine disrupters, phthalates are simultaneously present in a variety of environmental media and enter human body through multiple exposure pathways. In this study, field monitoring data were used to characterize the skin-air (K_lg ), dust-air (K_d ), and PM_2.5 -air (K_p ) partition coefficients of DiBP, DnBP, and DEHP. The median values of log(K_lg ) in the summer and winter were 7.654 and 7.932, 7.265 and 7.902, 9.419 and 9.015 for DiBP, DnBP, and DEHP, respectively, and K_lg was significantly higher in the winter. The median K_d (m³ /mg) in the summer (0.036-0.151 for DiBP, 0.021-0.036 for DnBP and 1.479-4.069 for DEHP) were significantly higher than the counterparts in the winter (0.027-0.065 for DiBP, 0.022-0.245 for DnBP, and 0.140-3.250 for DEHP). In addition, K_d was associated with material of surface and residence time of dust. The K_p values (m³ /μg) of DiBP, DnBP, and DEHP in the summer (0.053, 0.015, and 0.021) were also significantly higher than the counterparts in the winter (0.011, 0.004, and 0.025). The partition of phthalates was influenced by built environment, such as temperature, humidity, ventilation, indoor chemistry, smoking, and building age. Except K_lg , there was substantial discrepancy between the estimates of K with empirical equations and the values of K based on field monitoring data in our study.

Identification of Phthalates from Artificial Products in Chinese Kindergarten Classrooms and the Implications for Preschool Children's Exposure Assessments

Phthalates are typical chemical pollutants in kindergarten classrooms since numerous artificial products (e.g., polyvinyl chloride (PVC) floorings, soft polymers and plastic toys) that might contain phthalates are widely distributed in kindergarten classrooms. Although Chinese preschool children spend a considerable amount of their waking hours (>8 h/day) in kindergartens, phthalate exposure in such indoor environment has not been given much attention. In this study, the mass fractions of six phthalates in twenty-six artificial products (fifteen flat decoration materials and eleven plastic toys) commonly found in Chinese kindergarten classrooms were measured. Di-2-ethylhexyl phthalate (DEHP) was the most predominant compound in all materials. The emission characteristics of the DEHP from these materials were further investigated. The measured emission characteristics were used for predicting multi-phase DEHP concentrations in kindergarten classrooms by applying a mass transfer model. The modeled concentrations were comparable with those measured in the real environment, indicating that these products might be the major sources of DEHP in Chinese kindergarten classrooms. Preschool children’s exposure to DEHP was found to be 0.42 μg/kg/day in kindergartens under baseline conditions, accounting for 18% of the total exposure to DEHP in Chinese indoor environments.

OBOMod - Integrated modelling framework for residents' exposure to pesticides

BACKGROUND

Pesticides can be transported from the site of application to homes via different routes and lead to exposure of residents, raising concerns regarding health effects. We built a deterministic model framework (OBOmod) to assess exposure of residents living near fields where pesticides are applied.

METHODS

OBOmod connects five independent models operating on an hourly timescale and high spatial resolution (meters). Models include descriptions of spray drift, volatilization, atmospheric transport and dispersion, exchange between outdoor and indoor air and exchange between indoor air and dust. Fourteen bulb field applications under different weather conditions and comprising 12 pesticides were simulated. Each simulation included the first seven days after the application. The concentrations computed with OBOmod were compared with those measured in outdoor and indoor air and the amounts measured in indoor dust samples.

RESULTS

Model evaluation indicated suitability of the developed framework to estimate outdoor and indoor air concentrations. For most pesticides, model accuracy was good. The framework explained about 30% to 95% of the temporal and spatial variability of air concentrations. For 20% of the simulations, the framework explained more than 35% of spatial variability of concentrations in dust. In general, OBOmod estimates remained within one order of magnitude from measured levels. Calculations showed that in addition to spray drift during application, volatilization from the field after spraying and pesticides in house dust are important routes for residents' exposure to pesticides.

CONCLUSIONS

Our framework covers many processes needed to calculate exposure of residents to pesticides. The evaluation phase shows that, with the exception of the dust model, the framework can be used in support of health and epidemiological studies, and can serve as a tool to support development of regulations and policy making regarding pesticide use.

Investigation on the Direct Transfer of SVOCs from Source to Settled Dust: Analytical Model and Key Parameter Determination

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 applied to determine the key parameters of SVOC transport, i.e., the diffusion coefficient in the dust, the dust-air partition coefficient, and the chamber surface-air partition coefficient. Experiments of direct contact between SVOC source materials containing organophosphorus flame retardants (OPFRs) and settled dust were conducted in chambers. The key parameters were determined by performing curve fitting using data collected from the OPFR chamber tests and from the literature on phthalates. The reliability and robustness of the model and measurement method are demonstrated by the high fitting accuracy and sensitivity analysis. The obtained key parameters are more accurate than those from correlations in prior studies. Further analysis indicates that dust-air partition coefficient plays an important role and the adsorption effect on surfaces cannot be neglected for SVOC transport.

Temperature and indoor environments

From the thermodynamic perspective, the term temperature is clearly defined for ideal physical systems: A unique temperature can be assigned to each black body via its radiation spectrum, and the temperature of an ideal gas is given by the velocity distribution of the molecules. While the indoor environment is not an ideal system, fundamental physical and chemical processes, such as diffusion, partitioning equilibria, and chemical reactions, are predictably temperature-dependent. For example, the logarithm of reaction rate and equilibria constants are proportional to the reciprocal of the absolute temperature. It is therefore possible to have non-linear, very steep changes in chemical phenomena over a relatively small temperature range. On the contrary, transport processes are more influenced by spatial temperature, momentum, and pressure gradients as well as by the density, porosity, and composition of indoor materials. Consequently, emergent phenomena, such as emission rates or dynamic air concentrations, can be the result of complex temperature-dependent relationships that require a more empirical approach. Indoor environmental conditions are further influenced by the thermal comfort needs of occupants. Not only do occupants have to create thermal conditions that serve to maintain their core body temperature, which is usually accomplished by wearing appropriate clothing, but also the surroundings must be adapted so that they feel comfortable. This includes the interaction of the living space with the ambient environment, which can vary greatly by region and season. Design of houses, apartments, commercial buildings, and schools is generally utility and comfort driven, requiring an appropriate energy balance, sometimes considering ventilation but rarely including the impact of temperature on indoor contaminant levels. In our article, we start with a review of fundamental thermodynamic variables and discuss their influence on typical indoor processes. Then, we describe the heat balance of people in their thermal environment. An extensive literature study is devoted to the thermal conditions in buildings, the temperature-dependent release of indoor pollutants from materials and their distribution in the various interior compartments as well as aspects of indoor chemistry. Finally, we assess the need to consider temperature holistically with regard to the changes to be expected as a result of global emergencies such as climate change.

Phthalates in house dust in Chinese urban residences: Concentrations, partition, origin and determinants

Exposure to phthalates poses adverse health impacts to human beings. In this study, we analyzed 7 phthalates in dust samples, which were collected with vacuum cleaner from 40 to 31 residences in Beijing in summer and winter, respectively. The major phthalates (median concentration in the summer and winter, respectively) were DiBP (55 and 40 ng/mg), DnBP (99 and 30 ng/mg) and DEHP (795 and 335 ng/mg). The concentrations were significantly influenced by season and residence time of house dust. The concentrations of phthalates in dust on plastic surfaces were highest, followed by those on wooden and fabric surfaces. The dust-air partition coefficients (K_d) were calculated: the median values were 0.13, 0.02 and 5.62 m³/mg in the summer and 0.06, 0.018 and 0.76 m³/mg in the winter for DiBP, DnBP and DEHP, respectively. A comparison with K_d* at equilibrium state suggested that partition between air and dust deviated from equilibrium state in both seasons. The results also revealed that dust-phthalates in the summer may completely originate from source materials via direct transfer and external physical process; while dust-phthalates in the winter may come from both air (via partition) and source material (via direct transfer and external physical process). The influence of temperature on dust-phthalate concentrations differed by season, owing to different origin of dust-phthalates in two seasons. Polar organic components in dust, which are products of reactions between O₃ and unsaturated hydrocarbons in dust, likely played an important role in fate and transport of phthalates. The presence of them resulted in the significant associations between dust-phthalate concentrations and air humidity in the summer. Moreover, the impacts of indoor PM_2.5 concentrations, traffic conditions surrounding residence, household lifestyle and number of occupants were also observed. The mechanisms behind those observations were discussed.

Assessing exposure of semi-volatile organic compounds (SVOCs) in car cabins: Current understanding and future challenges in developing a standardized methodology

Semi-volatile organic compounds (SVOCs) can be found in air, dust and on surfaces in car cabins, leading to exposure to humans via dust ingestion, inhalation, and dermal contact. This review aims at describing current understanding concerning sampling, levels, and human exposure of SVOCs from car cabin environments. To date, several different methods are used to sample SVOCs in car cabin air and dust and there are no standard operating procedures for sampling SVOCs in cars detailed in the literature. The meta-analysis of SVOCs in car cabin air and dust shows that brominated flame retardants (BFRs) and organophosphate flame retardants (OPFRs) have been most frequently studied, primarily focusing on concentrations in dust. In dust, detected concentrations span over three to seven orders of magnitude, with highest median concentrations for OPFRs, followed by BFRs and, thereafter, polychlorinated biphenyls (PCBs). In air, the variation is smaller, spanning over one to three orders of magnitude, with phthalates and siloxanes having the highest median concentrations, followed by OPFRs, fluorotelomer alcohols (FTOHs) and BFRs. Assessments of human exposures to SVOCs in cars have, so far, mainly focused on external exposure, most often only studying one exposure route, primarily via dust ingestion. In order to perform relevant and complete assessments of human exposure to SVOCs in cars, we suggest broadening the scope to which SVOCs should be studied, promoting more comprehensive external exposure assessments that consider exposure via all relevant exposure routes and making comparisons of external and internal exposure, in order to understand the importance of in-car exposure as a source of SVOC exposure. We also suggest a new sampling approach that includes sampling of SVOCs in both car cabin air and dust, aiming to reduce variability in data due to differences in sampling techniques and protocols.

Phthalates in Chinese vehicular environments: Source emissions, concentrations, and human exposure

Phthalates are typical air pollutants in vehicular environment since numerous synthetic materials that might contain phthalates are widely used to fabricate vehicle interiors (e.g., seat cushions, floor mats and dashboards). Hitherto, the importance of phthalate pollution in vehicular environment is not well-recognized because people spend only a small portion (around 8%) of their time in vehicles. In this study, the mass fractions of six phthalates in nine materials commonly used in Chinese vehicles (floor mats and seat cushions) were measured. Two phthalates, di-n-butyl phthalate (DnBP) and di-2-ethylhexyl phthalate (DEHP), were identified in most materials (the other phthalates were not detected). The emission characteristics of DnBP and DEHP from these materials were further investigated. The measured emission parameters were used as input for a mass-transfer model to estimate DnBP and DEHP concentrations in cabin air. Finally, the ratios between human exposures (via inhalation and dermal absorption from the gas phase) in vehicular environment and the total exposures in typical indoor environments (e.g., residences and offices) were estimated to be up to 110% and 20% for DnBP and DEHP, respectively. Based on these results, the vehicular environment might be a considerable site for human exposure to airborne phthalates.

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.

Sorption and migration of organophosphate flame retardants between sources and settled dust

Dust serves as a strong sink for indoor pollutants, such as organophosphorus flame retardants (OPFRs). OPFRs are semivolatile chemicals that are slow in emissions but have long-term effects in indoor environments. This research studied the emission, sorption, and migration of OPFRs tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, and tris(1,3-dichloro-2-propyl) phosphate, from different sources to settled dust on OPFR source surfaces and OPFR-free surfaces. Four sink effect tests and six dust-source migration tests, including direct contact and sorption tests were conducted in 53 L stainless steel small chambers at 23 °C and 50% relative humidity. OPFR emission concentrations, and sorption and migration rates were determined. The dust-air and dust-material partition coefficients were estimated based on the experimental data and compared with those from the literature obtained by empirical equations. They are in the range of 1.4 × 10⁷ to 2.6 × 10⁸ (dimensionless) for the dust-air equilibrium partition coefficients and 2.38 × 10^-3 to 0.8 (dimensionless) for the dust-material equilibrium partition coefficients. It was observed that the dust with less organic content and smaller size tended to absorb more OPFRs, but different dust did not significantly affect OPFRs emission from the same source to the chamber air. The dust-air partition favored the less volatile OPFRs in the house dust, whereas the emission from the source favored the volatile chemicals. Volatility of the chemicals had much less effect on dust-source partitioning than on dust-air partitioning. The results from this work improve our understating of the fate and mass transfer mechanisms between OPFRs sources, indoor air, surface, and dust.

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.

Sorption of PCB from air to settled house dust in a contaminated indoor environment

Investigation of human exposure pathways to PCB in a high-rise estate in Denmark motivated an experiment with sorption of PCB from air to settled house dust. Three sieved house dust samples (<75 μm) of different origin were exposed to elevated air concentrations of PCB in a vacated apartment from seven to 40 days. Within the 40 days, most of the dust samples were close to equilibrium for the congeners PCB-8 to -101 and dust-air partition coefficients were determined. The dust samples of different origin showed comparable partitioning, though small differences were seen. The determined partition coefficients were in agreement with values found in literature. Further, the partition coefficients were compared to three sets of predicted estimates based on absorption of PCB into the organic matter of the dust and octanol-air partition coefficients derived from different sources. Comparing measured and predicted values (log-log), two sets of predicted values showed strong correlation, though overestimated 20-40%, while one set showed similar absolute levels, but with a few deviating congeners. Dust-air ratios were calculated for samples taken from a field investigation in homes with elevated air concentrations of PCB in the high-rises. The partitioning in the field samples were in agreement with the results from the exposure experiment and indicate near steady state conditions for the congeners in the dust from the homes. Dust exposed directly on the floorboards showed lower concentrations than samples placed on foil, indicating an ongoing sorption to the varnish being a tertiary source contaminated by the air.

Direct Transfer of Phthalate and Alternative Plasticizers from Indoor Source Products to Dust: Laboratory Measurements and Predictive Modeling

Phthalate and alternative plasticizers are semivolatile organic compounds (SVOCs) and among the most abundant indoor pollutants. Although ingestion of dust is one of the major exposure pathways to them, migration knowledge from source products to indoor dust is still limited. Systematic chamber measurements were conducted to investigate the direct transfer of these SVOCs between source products and dust in contact with the source. Substantial direct source-to-dust transfer of SVOCs was observed for all tests. The concentration of bis(2-ethylhexyl)phthalate in dust was 12 times higher than the pre-experimental level after only two days of source-dust contact. A mechanistic model was developed to predict the direct transfer process, and a reasonable agreement between model predictions and measurements was achieved. The octanol/air partition coefficient (K_oa) of SVOCs, the emission parameter of the source product (y₀), and the characteristics of the dust layer (i.e., porosity and thickness) control the transfer, affecting the SVOC concentration in dust, the kinetics of direct transfer, or both. Dust mass loading has a significant influence on the transfer, while relative humidity only has a limited effect. The findings suggest that minimizing the use of SVOC-containing products and house vacuuming are effective intervention strategies to reduce young children's exposure to SVOCs.

Addressing uncertainty in mouthing-mediated ingestion of chemicals on indoor surfaces, objects, and dust

In indoor environments, humans ingest chemicals present as surface residues and bound to settled particles (dust), through mouthing hands (hand-to-mouth transfer) and objects (object-to-mouth transfer). Here, we introduce a novel modeling approach in support of systematic investigation into the mouthing-mediated ingestion of chemicals present in indoor environments. This model explicitly considers the indoor dynamics of dust and chemicals, building on mechanistic links with physicochemical properties of chemicals, features of the indoor environment, and human activity patterns. The evaluation of this model demonstrates that it satisfactorily reproduces chemical hand loadings and exposure data reported in the literature. We then use the evaluated model to investigate the response of mouthing-mediated ingestion to chemical partitioning between the gas phase and solid phases, expressed as the octanol-air partition coefficient (K_OA). Assuming a unit emission rate to the indoor environment, we find that low-volatility chemicals (with a K_OA greater than 10⁹) are more efficiently enriched in hand skin, resulting in higher mouthing-mediated ingestion than other compounds. For individuals living in a room with a typical level of dustiness, more than half of the chemical mass found in their hands comes from dust transfer, whereas more than half of the chemical mass ingested is the fraction present as residues on hands. We also use the new model to explore how the mouthing-mediated ingestion of chemicals is dependent on factors describing the indoor environment and human behavior. The model predicts that less frequent cleaning leads to higher accumulation of dust on indoor surfaces, thereby transferring more chemicals to hands and mouth in each contact. Introducing more dust into the room, but maintaining the same cleanup frequency, increases the dustiness of indoor surfaces, which promotes the transfer of relatively volatile chemicals (with a K_OA lower than 10⁹) to hands and mouth but decreases the transfer of chemicals with low volatility. More frequent hand contact with indoor surfaces increases both the hand loading and mouthing-mediated ingestion of chemicals, but the increases are more remarkable for adults than children because the higher surface contact frequency of children "saturates" hand loadings. An increase in handwashing frequency lowers the hand loading and mouthing-mediated ingestion of chemicals and this mitigating process is more prominent for relatively volatile chemicals. The new evaluated modeling approach can facilitate the prediction of mouthing-mediated ingestion for various age groups and the model predictions can be used to aid future fate and (bio)monitoring studies focusing on indoor contamination.

Airborne phthalates in indoor environment: Partition state and influential built environmental conditions

Exposure to phthalates has recently become a major public health concern. The information of indoor airborne phthalates and their air-particle partition in real indoor environmental condition is still limited. In this study, the gas- and PM_2.5-concentrations of 7 phthalates in 40 residences were concurrently measured in summer and winter. The major phthalates (median concentration in the summer and winter, respectively) in indoor air were DMP (2442.3 and 2403.4 ng/m³), DiBP (801.0 and 640.0 ng/m³) and DnBP (5173.2 and 1379.6 ng/m³), whereas the major phthalates in PM_2.5 were DiBP (1055.1 and 585.9 ng/m³) and DnBP (1658.5 and 1517.0 ng/m³) and DEHP (215.1 and 344.9 ng/m³). Air-PM_2.5 partition coefficients (K_p) of DiBP, DnBP and DEHP were calculated: the summer and winter median values (m³/μg) were 0.053 and 0.011 for DiBP, 0.010 and 0.004 for DnBP, 0.021 and 0.025 for DEHP, respectively. Air-PM_2.5 partition of DiBP and DnBP approached equilibrium, while that of DEHP did not reach equilibrium in either season. The impacts of built environmental conditions on phthalate concentrations were characterized. Elevated temperature resulted in accumulation of airborne phthalates. Higher air humidity led to more water absorption of aerosols in summer, facilitated mass transfer of phthalates from air to PM_2.5, and resulted in greater K_p of DiBP and DnBP in the summer. Any factors such as proximity to local traffic highway and indoor smoking activities, which can increase indoor PM_2.5 concentrations, resulted in significantly higher airborne phthalate concentrations. Improving ventilation was not an effective measure to reduce indoor airborne phthalate concentrations.

Phthalates: Relationships between Air, Dust, Electronic Devices, and Hands with Implications for Exposure

Exposure to phthalates is pervasive and is of concern due to associations with adverse health effects. Exposures and exposure pathways of six phthalates were investigated for 51 women aged 18-44 years in Ontario, Canada, based on measured phthalate concentrations in hand wipes and indoor media in their residences. All six phthalates had detection frequencies of 100% in air (∑₆670 ng m^-3 geomean) and floor dust (∑₆630 μg g^-1), nearly 100% detection frequencies for hand palms and backs that were significantly correlated and concentrations were repeatable over a 3 week interval. Phthalates on hands were significantly correlated with levels in air and dust, as expected according to partitioning theory. Total exposure was estimated as 4860 ng kg bw^-1 day^-1 (5th and 95th percentiles 1980-16 950 ng kg bw^-1 day^-1), with dust ingestion, followed by hand-to-mouth transfer, as the dominant pathways. With the exception of diethyl phthalate (DEP), phthalates had over 50% detection frequencies in surface wipes of most electronic devices sampled, including devices in which the use of phthalates was not expected. Phthalate concentrations on surfaces of hand-held devices were ∼10 times higher than on non-hand-held devices and were correlated with levels on hands. The data are consistent with phthalate emissions from sources such as laminate flooring and personal care products (e.g., scented candles), followed by partitioning among air, dust, and surface films that accumulate on electronic devices and skin, including hands. We hypothesize that hands transfer phthalates from emission sources and dust to hand-held electronic devices, which accumulate phthalates due to infrequent washing and which act as a sink and then a secondary source of exposure. The findings support those of others that exposure can be mitigated by increasing ventilation, damp cloth cleaning, and minimizing the use of phthalate-containing products and materials.

Diethylhexyl phthalate (DEHP) emission to indoor air and transfer to house dust from a PVC sheet

Diethylhexyl phthalate (DEHP) emission to air and transfer to house dust from a polyvinyl chloride (PVC) sheet were quantified for periods of 1, 3, 7, and 14 days using a passive flux sampler (PFS). Japanese Industrial Standards (JIS) test powders class 15 was used as the test house dust in settled weights of 0.3, 1, 3, and 12 mg/cm². DEHP concentrations in the surface air on the PVC sheet were estimated as 2.6-3.3 μg/m³ according to an emission test without dust. Although DEHP transfer rates from the PVC sheet to the house dust decreased over time, the adsorption did not reach an equilibrium state within 14 days. The transfer rates per dust weight increased with decreasing dust weight on the PVC sheet. The transfer rates per PVC sheet area increased nonlinearly with increasing dust weight on the PVC sheet. DEHP emission from a PVC sheet to air was one to three orders of magnitude lower than DEHP transfer from a PVC sheet to dust. In the case of 0.3 mg/cm² of settled house dust for 7 days, the emission rates to air were 35, 15, 9.1, 6.4, and 3.8 μg/m²/h for a diffusion distance of 0.90, 1.85, 2.75, 3.80, and 5.75 mm, respectively, and the transfer rate to dust was 5.3 × 10² μg/m²/h (no difference among the five diffusion distances). Compared to residents who clean the floor every day, exposure to DEHP in house dust could be 10 times higher for residents who clean the floor once every two weeks based on the time-weighted average concentrations in house dust.

Time series of hexabromocyclododecane transfers from flame-retarded curtains to attached dust

While the production and new use of hexabromocyclododecane (HBCD) mostly ceased after being listed as a persistent organic pollutant under the Stockholm Convention in 2013, its emission from treated products in use to indoor environments still deserves attention. To examine the transfer of HBCD diastereomers to dust on the surface of flame-retarded curtains and to better characterize the potential of treated fabrics to be sources of HBCD in dust, we carried out a series of 196-day experiments using two types of curtains and attached dusts. Concurrently, the physicochemical properties (vapor pressure, water solubility, and octanol-water partition coefficient) of the HBCD diastereomers were measured. HBCD diastereomers migrated from curtains to dust with half-saturation times of about 20-50 days. By day 196, mean HBCD concentrations in dust had reached 13-290 μg/g, depending on the types of curtains and dusts. The composition of HBCD, dominated by γ-HBCD in the curtains, was dominated by α-HBCD in the post-experiment dusts, probably because of the higher vapor pressure of α-HBCD compared to γ-HBCD. The initial HBCD contents of the two curtains were comparable, but the concentrations and profiles of HBCD diastereomers in the post-experiment dusts differed markedly, probably because differences between the texture and/or surface finishing of the treated fabrics affected HBCD transfer to the attached dust.

Distribution of five SVOCs in a model room: effect of vacuuming and air cleaning measures

With regard to the application of semi-volatile organic compounds (SVOCs) in products for indoor use, a distinct trend towards substitutions can currently be observed. Among the possible phthalate alternatives, in particular the adipic acid esters have gained in market importance. The chemical-physical and thermodynamic properties of the phthalates and adipates allow the conclusion to be drawn that they are distributed between different compartments (gas phase, particle phase, dust, material surfaces) of the indoor space. There are, however, hardly any data in existence which were collected in a real environment over six months and longer. Diisobutyl adipate (DiBA), di-n-butyl adipate (DnBA), dipentyl phthalate (DPP), butyl benzyl phthalate (BBzP) and di-2-ethylhexyl adipate (DEHA) were selected as model substances. By means of spiked latex paint and spiked house dust, these SVOCs were introduced into two identically equipped test rooms. One room was cleaned regularly, whilst the reference room was not entered for a 133 day experimental period. The concentrations of the five target substances were determined in the air and in material samples (carpet, vacuum-cleaner bags, filters). During the operation of an air purifier, the air concentration of the target substances in a room could be reduced by more than 50%. In the reference room, a correlation between the logarithmic air concentration and the reciprocal room temperature was found. The results show with great clarity the complexity of the conditions in an indoor room. Models can therefore depict the exposure as a statistical average but not, however, describe the individual case.

Characterizing Airborne Phthalate Concentrations and Dynamics in a Normally Occupied Residence

Phthalate esters, commonly used as plasticizers, can be found indoors in the gas phase, in airborne particulate matter, in dust, and on surfaces. The dynamic behavior of phthalates indoors is not fully understood. In this study, time-resolved measurements of airborne phthalate concentrations and associated gas-particle partitioning data were acquired in a normally occupied residence. The vapor pressure and associated gas-particle partitioning of measured phthalates influenced their airborne dynamic behavior. Concentrations of higher vapor pressure phthalates correlated well with indoor temperature, with little discernible influence from direct occupant activity. Conversely, occupant-related behaviors substantially influenced the concentrations and dynamic behavior of a lower vapor pressure compound, diethylhexyl phthalate (DEHP), mainly through production of particulate matter during cooking events. The proportion of airborne DEHP in the particle phase was experimentally observed to increase under higher particle mass concentrations and lower indoor temperatures in correspondence with theory. Experimental observations indicate that indoor surfaces of the residence are large reservoirs of phthalates. The results also indicate that two key factors influenced by human behavior-temperature and particle mass concentration-cause short-term changes in airborne phthalate concentrations.

Enhanced emissions of brominated flame retardants from indoor sources by direct contact with dust

The emissions of brominated flame retardants (BFRs) from consumer products have been considered the major to the ubiquitous occurrence of contaminants in indoor environments. Direct contact with dust covering the surface of source materials in a real environment could introduce significant uncertainty. This study investigated the effects of dust coverage on the emissions of four BFRs, including 1, 2, 5, 6, 9, and 10-hexabromocyclododecane (HBCD), bis(2-ethyl-1-hexyl) tetrabromophthalate (BEHTBP), tetrabromobisphenol A (TBBPA), and hexabromobenzene (HBBZ), from decorative laminate, cotton sound insulation, PVC floor, and carpet. Direct contact with dust was confirmed to increase the total emissions by 30.8-98.1% compared with the emissions in the non-dust group. The emissions of HBCD, TBBPA, and HBBZ from cotton sound insulation were obviously enhanced by dust with smaller particles but did not linearly increase along with the dust amounts. Thus, these findings have practical implications in that the frequent removal of dust could be important to minimize the exposure risk from indoor emissions of BFRs.

PVC flooring at home and uptake of phthalates in pregnant women

Phthalates are used as plasticizers in polyvinyl chloride (PVC) materials and it is known that phthalates may migrate into the surrounding environment and then become a source for human uptake. The aim of the study was to investigate whether residential PVC flooring was related to the urinary levels of phthalate metabolites determined in pregnant women. The data were from the Swedish SELMA study where sampling was conducted during the time period 2007-2010. Spot urine samples from 1674 women at the end of the first trimester were analyzed for 14 metabolites from seven phthalates and one phthalate alternative. Data on flooring material in the kitchen and the parents' bedrooms as well as potential confounders were collected by postal questionnaires at the same time as the urine samples were taken. Multiple regression modeling by least square geometric mean and weighted quantile sum regression was applied to log-transformed and creatinine-adjusted phthalate metabolite concentrations adjusted for potential confounders from questionnaire data. This study has found significantly higher urinary levels of the BBzP metabolite (MBzP) in pregnant women living in homes with PVC flooring as compared to homes with other flooring materials.

Phthalates and organophosphates in settled dust and HVAC filter dust of U.S. low-income homes: Association with season, building characteristics, and childhood asthma

Phthalates and organophosphates are ubiquitous indoor semi-volatile organic contaminants (SVOCs) that have been widely used as plasticizers and flame retardants in consumer products. Although many studies have assessed their levels in house dust, only a few used dust samples captured by filters of building heating, ventilation, and air conditioning (HVAC) systems. HVAC filters collect particles from large volumes of air over a long period of time (potentially known) and thus provide a spatially and temporally integrated concentration. This study measured concentrations of phthalates and organophosphates in HVAC filter dust and settled floor dust collected from low-income homes in Texas, United States, in both the summer and winter seasons. The most frequently detected compounds were benzyl butyl phthalate (BBzP), di-(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DnOP), tris (1-chloro-2-propyl) phosphate (TCIPP), triphenyl phosphate (TPHP), and tris (1,3-dichloroisopropyl) phosphate (TDCIPP). The median level of TCIPP in settled dust was 3- to 180-times higher than levels reported in other studies of residential homes. Significantly higher concentrations were observed in HVAC filter dust as compared to settled dust for most of the frequently detected compounds in both seasons, except for several phthalates in the winter. SVOC concentrations in settled dust in winter were generally higher than in summer, while different seasonality patterns were found for HVAC filter dust. Settled dust samples from homes with vinyl flooring contained significantly higher levels of BBzP and DEHP as compared to homes with other types of floor material. The concentration of DEHP and TDCIPP in settled dust also significantly associated with the presence of carpet in homes. Cleaning activities to remove dust from furniture actually increased the levels of certain compounds in HVAC filter dust, while frequent vacuuming of carpet helped to decrease the concentrations of some compounds in settled dust. Additionally, the size and age of a given house also correlated with the levels of some pollutants in dust. A statistically significant association between DEHP concentration in HVAC filter dust in summer and the severity of asthma in children was observed. These results suggest that HVAC filter dust represents a useful sampling medium to monitor indoor SVOC concentrations with high sensitivity; in contrast, when using settled dust, in addition to consideration of seasonal influences, it is critical to know the sampling location because the type and level of SVOCs may be related to local materials used there.

Stabilizing mixed fatty acid and phthalate ester monolayer on artificial seawater

Phthalate esters which are widely used as industrial chemicals have become widespread contaminants in the marine environment. However, little information is available on the interfacial behavior of phthalate esters in the seawater, where contaminants generally occur at elevated concentrations and have the potential to transfer into the atmosphere through wave breaking on sea surface. We used artificial seawater coated with fatty acids to simulate sea surface microlayer in a Langmuir trough. The interactions of saturated fatty acids (stearic acid (SA) and palmitic acid (PA)) with one of the most abundant phthalate esters (di-(2-ethylhexyl) phthalate (DEHP)), were investigated under artificial seawater and pure water conditions. Pure DEHP monolayer was not stable, while more stable mixed monolayers were formed by SA and DEHP on the artificial seawater at relatively low surface pressure. Sea salts in the subphase can lower the excess Gibbs free energy to form more stable mixed monolayer. Among the ten components in the sea salts, Ca²⁺ ions played the major role in condensation of mixed monolayer. The condensed characteristic of the mixed SA (or PA)/DEHP monolayers suggested that the hydrocarbon chains were ordered on artificial seawater. By means of infrared reflection-absorption spectroscopy (IRRAS), we found that multiple sea salt mixtures induced deprotonated forms of fatty acids at the air-water interface. Sea salts can improve the stability and lifetime of mixed fatty acid and phthalate ester monolayer on aqueous droplets in the atmosphere. Interfacial properties of mixed fatty acid and phthalate ester monolayers at the air-ocean interface are important to help understand their behavior and fate in the marine environment.

Concentration and factors affecting the distribution of phthalates in the air and dust: A global scenario

Phthalates are ubiquitously present environmental contaminants. Air and dust are the most important mediums of exposure to phthalates. The present study reviews the presence of phthalates in the air and dust reported from different countries in the last ten years (2007-2017). The phthalate concentrations revealed wide heterogeneity with a mean and median value 6 ± 19 μg/m³ and 0.5 μg/m³ respectively in the air and 1.5 × 10³ ± 2.2 × 10³ μg/g and 7.8x10²μg/g respectively in the dust. The highest phthalates levels in the air were reported from India (1.1 × 10² μg/m³) and in dust from Bulgaria (1.2 × 10⁴ μg/g). Overall higher levels were reported from developing countries as compared to developed countries. Di (2-ethylhexyl) phthalate (DEHP) and Di-n-butyl phthalate (DBP) were found to be predominant in both air and dust. Temperature, humidity, air exchange rate, building material and indoor maintenance were reported as the important factors influencing the levels of phthalates in the air and dust. In addition to policy level interventions, reducing the use of phthalate containing materials and controlling the factors which enhance the emission from existing sources can help in reducing human exposure to phthalates.

Oral bioaccessibility of semi-volatile organic compounds (SVOCs) in settled dust: A review of measurement methods, data and influencing factors

Many semi-volatile organic compounds (SVOCs), suspected of reprotoxic, neurotoxic or carcinogenic effects, were measured in indoor settled dust. Dust ingestion is a non-negligible pathway of exposure to some of these SVOCs, and an accurate knowledge of the real exposure is necessary for a better evaluation of health risks. To this end, the bioaccessibility of SVOCs in dust needs to be considered. In the present work, bioaccessibility measurement methods, SVOCs' oral bioaccessibility data and influencing factors were reviewed. SVOC bioaccessibilities (%) ranged from 11 to 94, 8 to 100, 3 to 92, 1 to 81, 6 to 52, and 2 to 17, for brominated flame retardants, organophosphorus flame retardants, polychlorobiphenyls, phthalates, pesticides and polycyclic aromatic hydrocarbons, respectively. Measurements method produced varying results depending on the inclusion of food and/or sink in the model. Characteristics of dust, e.g., organic matter content and particle size, also influenced bioaccessibility data. Last, results were influenced by SVOC properties, such as octanol/water partition coefficient and migration pathway into dust. Factors related to dust and SVOCs could be used in prediction models. To this end, more bioaccessibility studies covering more substances should be performed, using methods that are harmonized and validated by comparison to in-vivo studies.

Influence of indoor environmental factors on mass transfer parameters and concentrations of semi-volatile organic compounds

Semi-volatile organic compounds (SVOCs) in indoor environments can partition among the gas phase, airborne particles, settled dust, and available surfaces. The mass transfer parameters of SVOCs, such as the mass transfer coefficient and the partition coefficient, are influenced by indoor environmental factors. Subsequently, indoor SVOC concentrations and thus occupant exposure can vary depending on environmental factors. In this review, the influence of six environmental factors, i.e., indoor temperature, humidity, ventilation, airborne particle concentration, source loading factor, and reactive chemistry, on the mass transfer parameters and indoor concentrations of SVOCs was analyzed and tentatively quantified. The results show that all mass transfer parameters vary depending on environmental factors. These variations are mostly characterized by empirical equations, particularly for humidity. Theoretical calculations of these parameters based on mass transfer mechanisms are available only for the emission of SVOCs from source surfaces when airborne particles are not present. All mass transfer parameters depend on the temperature. Humidity influences the partition of SVOCs among different phases and is associated with phthalate hydrolysis. Ventilation has a combined effect with the airborne particle concentration on SVOC emission and their mass transfer among different phases. Indoor chemical reactions can produce or eliminate SVOCs slowly. To better model the dynamic SVOC concentration indoors, the present review suggests studying the combined effect of environmental factors in real indoor environments. Moreover, interactions between indoor environmental factors and human activities and their influence on SVOC mass transfer processes should be considered.

Indoor residential exposure to semivolatile organic compounds in France

Multiple chemicals are emitted in residential accommodation. Aggregate Daily Doses (ADD) (ng/kg-bw/d) were estimated for 32 semivolatile organic compounds (SVOCs) of different chemical families that are frequently detected in French dwellings in both air and settled dust. Daily doses were determined using steady-state models for the population, categorized into 11 age groups covering birth to age 30. Three routes of exposure were taken into account: dust ingestion, inhalation (gaseous and particulate phases) and dermal contact with the gaseous phase of air. Contamination levels were preferentially retrieved from large, nationwide representative datasets. A two-dimensional probabilistic approach was used to assess parametric uncertainty and identify the most influential factors. For children aged 2 to 3years, ADD estimates spanned orders of magnitude, with median values ranging from 8.7pg/kg-bw/d for 2,2',3,4,4'-pentabromodiphenylether (BDE 85) to 1.3μg/kg-bw/d for di-isobutyl phthalate (DiBP). Inhalation, ingestion and dermal pathway contributed at varying levels, and depending on compound, air was the dominant medium for 28 of the 32 compounds (either by inhalation or dermal contact). Indoor exposure estimate variance was mainly driven by indoor contamination variability, and secondarily by uncertainty in physical and chemical parameters. These findings lend support to the call for cumulative risk assessment of indoor SVOCs.