Characterizing Airborne Phthalate Concentrations and Dynamics in a Normally Occupied Residence

Gas-phase and air-solid interface behavior of phthalate plasticizer and ozone: The influence of indoor mineral dust

Indoor environments serve as reservoirs for a variety of emerging pollutants (EPs), such as phthalates (PAE), with intricate interactions occurring between these compounds and indoor oxidants alongside dust particles. However, the precise mechanisms governing these interactions and their resulting environmental implications remain unclear. By theoretical simulations, this work uncovers multi-functional compounds and high oxygen molecules as important products arising from the interaction between DEP/DEHP and O3, which are closely linked to SOA formation. Further analysis reveals a strong affinity of DEP/DEHP for mineral dust surfaces, with an adsorption energy of 22.11/30.91 kcal mol-1, consistent with a higher concentration of DEHP on the dust surface. Importantly, mineral particles are found to inhibit every step of the reaction process, albeit resulting in lower product toxicity compared to the parent compounds. Thus, timely removal of dust in an indoor environment may reduce the accumulation and residue of PAEs indoors, and further reduce the combined exposure risk produced by PAEs-dust. This study aims to enhance our understanding of the interaction between PAEs and SOA formation, and to develop a fundamental reaction model at the air-solid surface, thereby shedding light on the microscopic behaviors and pollution mechanisms of phthalates on indoor dust surfaces.

The chemical assessment of surfaces and air (CASA) study: using chemical and physical perturbations in a test house to investigate indoor processes

The Chemical Assessment of Surfaces and Air (CASA) study aimed to understand how chemicals transform in the indoor environment using perturbations (e.g., cooking, cleaning) or additions of indoor and outdoor pollutants in a well-controlled test house. Chemical additions ranged from individual compounds (e.g., gaseous ammonia or ozone) to more complex mixtures (e.g., a wildfire smoke proxy and a commercial pesticide). Physical perturbations included varying temperature, ventilation rates, and relative humidity. The objectives for CASA included understanding (i) how outdoor air pollution impacts indoor air chemistry, (ii) how wildfire smoke transports and transforms indoors, (iii) how gases and particles interact with building surfaces, and (iv) how indoor environmental conditions impact indoor chemistry. Further, the combined measurements under unperturbed and experimental conditions enable investigation of mitigation strategies following outdoor and indoor air pollution events. A comprehensive suite of instruments measured different chemical components in the gas, particle, and surface phases throughout the study. We provide an overview of the test house, instrumentation, experimental design, and initial observations - including the role of humidity in controlling the air concentrations of many semi-volatile organic compounds, the potential for ozone to generate indoor nitrogen pentoxide (N2O5), the differences in microbial composition between the test house and other occupied buildings, and the complexity of deposited particles and gases on different indoor surfaces.

The triple exposure nexus of microplastic particles, plastic-associated chemicals, and environmental pollutants from a human health perspective

The presence of microplastics (MPs) is increasing at a dramatic rate globally, posing risks for exposure and subsequent potential adverse effects on human health. Apart from being physical objects, MP particles contain thousands of plastic-associated chemicals (i.e., monomers, chemical additives, and non-intentionally added substances) captured within the polymer matrix. These chemicals are often migrating from MPs and can be found in various environmental matrices and human food chains; increasing the risks for exposure and health effects. In addition to the physical and chemical attributes of MPs, plastic surfaces effectively bind exogenous chemicals, including environmental pollutants (e.g., heavy metals, persistent organic pollutants). Therefore, MPs can act as vectors of environmental pollution across air, drinking water, and food, further amplifying health risks posed by MP exposure. Critically, fragmentation of plastics in the environment increases the risk for interactions with cells, increases the presence of available surfaces to leach plastic-associated chemicals, and adsorb and transfer environmental pollutants. Hence, this review proposes the so-called triple exposure nexus approach to comprehensively map existing knowledge on interconnected health effects of MP particles, plastic-associated chemicals, and environmental pollutants. Based on the available data, there is a large knowledge gap in regard to the interactions and cumulative health effects of the triple exposure nexus. Each component of the triple nexus is known to induce genotoxicity, inflammation, and endocrine disruption, but knowledge about long-term and inter-individual health effects is lacking. Furthermore, MPs are not readily excreted from organisms after ingestion and they have been found accumulated in human blood, cardiac tissue, placenta, etc. Even though the number of studies on MPs-associated health impacts is increasing rapidly, this review underscores that there is a pressing necessity to achieve an integrated assessment of MPs' effects on human health in order to address existing and future knowledge gaps.

Pollution characteristics, sources, and health risks of phthalate esters in ambient air: A daily continuous monitoring study in the central Chinese city of Nanchang

In recent years, the atmospheric pollution caused by phthalate esters (PAEs) has been increasing due to the widespread use of PAE-containing materials. Existing research on atmospheric PAEs lacks long-term continuous observation and samples from cities in central China. To investigate the pollution characteristics, sources, and health risks of PAEs in the ambient air of a typical city in central China, daily PM2.5 samples were collected in Nanchang from November 2020 to October 2021. In this study, the detection and quantification of six significant PAE contaminants, namely diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), diisobutyl phthalate (DIBP), Di-2-ethylhexyl phthalate (DEHP), di-n-octyl phthalate (DnOP), and diisodecyl phthalate (DIDP), were accomplished using gas chromatography and mass spectrometry. The results revealed that the concentrations of DEP, DnBP, DEHP, and DnOP were relatively high. Higher temperatures promote the volatilization of PAEs, leading to an increase in the gaseous and particulate PAE concentrations in warm seasons and winter pollution scenarios. The results of principal component analysis show that PAEs mainly come from volatile products and polyvinylchloride plastics. Using positive matrix factorization analysis, it is shown that these two sources contribute 67.0% and 33.0% in atmosphere PAEs, respectively. Seasonally, the contribution of volatile products to both gaseous and particulate PAEs substantially increases during warm seasons. The residents in Nanchang exposed to PAEs have a negligible non-cancer risk and a potential low cancer risk. During the warm seasons, more PAEs are emitted into the air, which will increase the toxicity of PAEs and their impact on 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.

Reducing Transdermal Uptake of Semivolatile Plasticizers from Indoor Environments: A Clothing Intervention

Models and laboratory studies suggest that everyday clothing influences the transdermal uptake of semivolatile organic compounds, including phthalate plasticizers, from indoor environments. However, this effect has not been documented in environmental exposure settings. In this pilot study, we quantified daily excretion of 17 urinary metabolites (μg/day) for phthalates and phthalate alternatives in nine participants during 5 days. On Day 0, baseline daily excretion was determined in participants' urine. Starting on Day 1, participants refrained from eating phthalate-heavy foods and using personal care products. On Days 3 and 4, participants wore precleaned clothing as an exposure intervention. We observed a reduction in the daily excretion of phthalates during the intervention; mono-n-butyl phthalate, monoisobutyl phthalate (MiBP), and monobenzyl phthalate were significantly reduced by 35, 38, and 56%, respectively. Summed metabolites of di(2-ethylhexyl)phthalate (DEHP) were also reduced (27%; not statistically significant). A similar reduction among phthalate alternatives was not observed. The daily excretion of MiBP during the nonintervention period strongly correlated with indoor air concentrations of diisobutyl phthalate (DiBP), suggesting that inhalation and transdermal uptake of DiBP from the air in homes are dominant exposure pathways. The results indicate that precleaned clothing can significantly reduce environmental exposure to phthalates and phthalate alternatives.

The plastic health map: A systematic evidence map of human health studies on plastic-associated chemicals

BACKGROUND

The global production and use of plastic materials has increased dramatically since the 1960s and there is increasing evidence of human health impacts related to exposure to plastic-associated chemicals. There is, however, no comprehensive, regulatory, post-market monitoring for human health effects of plastic-associated chemicals or particles and it is unclear how many of these have been investigated for effects in humans, and therefore what the knowledge gaps are.

OBJECTIVE

To create a systematic evidence map of peer-reviewed human studies investigating the potential effects of exposure to plastic-associated particles/chemicals on health to identify research gaps and provide recommendations for future research and regulation policy.

METHODS

Medline and Embase databases were used to identify peer-reviewed primary human studies published in English from Jan 1960 - Jan 2022 that investigated relationships between exposures to included plastic-associated particles/chemicals measured and detected in bio-samples and human health outcomes. Plastic-associated particles/chemicals included are: micro and nanoplastics, due to their widespread occurrence and potential for human exposure; polymers, the main building blocks of plastic; plasticizers and flame retardants, the two most common types of plastic additives with the highest concentration ranges in plastic materials; and bisphenols and per- or polyfluoroalkyl substances, two chemical classes of known health concern that are common in plastics. We extracted metadata on the population and study characteristics (country, intergenerational, sex, age, general/special exposure risk status, study design), exposure (plastic-associated particle/chemical, multiple exposures), and health outcome measures (biochemical, physiological, and/or clinical), from which we produced the interactive database 'Plastic Health Map' and a narrative summary.

RESULTS

We identified 100,949 unique articles, of which 3,587 met our inclusion criteria and were used to create a systematic evidence map. The Plastic Health Map with extracted metadata from included studies are freely available at https://osf.io/fhw7d/ and summary tables, plots and overall observations are included in this report.

CONCLUSIONS

We present the first evidence map compiling human health research on a wide range of plastic-associated chemicals from several different chemical classes, in order to provide stakeholders, including researchers, regulators, and concerned individuals, with an efficient way to access published literature on the matter and determine knowledge gaps. We also provide examples of data clusters to facilitate systematic reviews and research gaps to help direct future research efforts. Extensive gaps are identified in the breadth of populations, exposures and outcomes addressed in studies of potential human health effects of plastic-associated chemicals. No studies of the human health effects of micro and/or nanoplastics were found, and no studies were found for 26/1,202 additives included in our search that are of known hazard concern and confirmed to be in active production. Few studies have addressed recent "substitution" chemicals for restricted additives such as organophosphate flame retardants, phthalate substitutes, and bisphenol analogues. We call for a paradigm shift in chemical regulation whereby new plastic chemicals are rigorously tested for safety before being introduced in consumer products, with ongoing post-introduction biomonitoring of their levels in humans and health effects throughout individuals' life span, including in old age and across generations.

Seasonal variations of airborne phthalates and novel non-phthalate plasticizers in a test residence in cold regions: Effects of temperature, humidity, total suspended particulate matter, and sources

As a class of plasticizers widely used in consumer products, some phthalate esters (PAEs) have been restricted due to their adverse health effects and ubiquitous presence, leading to the introduction of alternative non-phthalates plasticizers (NPPs) to the market. However, few studies focus on the influence of environmental parameters on the presence of these plasticizers and the potential human health risks for people living in poorly ventilated indoor spaces in cold regions. We investigated the trends of PAEs and NPPs in air in a typical indoor residence in northern China for over one year. The air concentrations of PAEs were significantly higher than those of NPPs (p < 0.05), indicating that PAEs are still the dominant plasticizers currently being used in the studied residence. PAEs showed seasonal fluctuation patterns of the highest levels found in summer and autumn. The temperature and relative humidity dependence for most PAEs and NPPs decreased with decreasing vapor pressure. Concentrations of the high molecular weight NPPs and PAEs positively correlated with total suspended particles (TSP). It is worth noting that the peak concentrations of PAEs and NPPs were found when the haze occurred in autumn. Principal component analysis (PCA) suggested the diverse applications of PAEs and NPPs in the indoor environment. The hazard index (HI) values observed in this study were all below international guidelines (<1); however, the average carcinogenic risk (CR) values for some compounds exceeded acceptable levels (One in a million), which raised concerns about the possibility of carcinogenicity for people living indoors for long periods of time in cold regions.

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

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

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.

Exposure Characteristics and Cumulative Risk Assessment for Phthalates in Children Living near a Petrochemical Complex

BACKGROUND

School-aged children living near plastics-producing factories may have higher risk of exposure to phthalates released during the manufacturing processes.

OBJECTIVES

We aimed to investigate the urinary concentrations of phthalate metabolites in school-aged children living near a petrochemical complex and estimate the cumulative risk of phthalate exposure.

METHODS

We used a well-established cohort (Taiwan Petrochemical Complex Cohort for Children, TPE3C) of school-aged children (6-13 years old) living near polyvinyl chloride (PVC) and vinyl chloride monomer (VCM) factories in central Taiwan from October 2013 to September 2014. A total of 257 children were included from five elementary schools: Syu-Cuo Branch (n = 58, school A, ~0.9 km), Feng-An (n = 40, school B, ~2.7 km), Ciao-Tou (n = 58, school C, ~5.5 km), Mai-Liao (n = 37, school D, ~6.9 km), and Lung-Feng (n = 57, school E, ~8.6 km). We analyzed 11 metabolites of seven phthalates (including di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DnBP)) in urine. Daily intakes (DIs) were compared with acceptable intake levels to calculate the hazard quotient (HQ) for individual phthalates, and the cumulative risk for each child was assessed using a hazard index (HI), which was the sum of the the individual HQs.

RESULTS

The geometric mean and proportion of participants with HIs exceeding one for hepatic (HI_hep) and reproductive (HI_rep) effects were 0.33 (13.2%) and 0.24 (7.8%), respectively. The major contributors to phthalate exposure risk were DEHP, di-iso-butyl phthalate (DiBP) and DnBP in all children. Moreover, we observed a U shaped distribution of DEHP exposure by school distance from the PVC and VCM factories (school A: 7.48 μg/kg/day and school E: 80.44 μg/kg/day). This may be due to emissions (closest) and and being located downwind of PVC scrap incineration (farthest).

CONCLUSIONS

Our findings suggest that children living near a petrochemical complex were at a greater risk of phthalate exposure than normal school-aged children and that phthalate exposure was mainly attributed to DEHP, DiBP and DnBP. In addition, inhalation may have been a risk factor for people living near to PVC and VCM factories.

A review of indoor Gaseous organic compounds and human chemical Exposure: Insights from Real-time measurements

Gaseous organic compounds, mainly volatile organic compounds (VOCs), have become a wide concern in various indoor environments where we spend the majority of our daily time. The sources, compositions, variations, and sinks of indoor VOCs are extremely complex, and their potential impacts on human health are less understood. Owing to the deployment of the state-of-the-art real-time mass spectrometry during the last two decades, our understanding of the sources, dynamic changes and chemical transformations of VOCs indoors has been significantly improved. This review aims to summarize the key findings from mass spectrometry measurements in recent indoor studies including residence, classroom, office, sports center, etc. The sources and sinks, compositions and distributions of indoor VOCs, and the factors (e.g., human activities, air exchange rate, temperature and humidity) driving the changes in indoor VOCs are discussed. The physical and chemical processes of gas-particle partitioning and secondary oxidation processes of VOCs, and their impacts on human health are summarized. Finally, the recommendations for future research directions on indoor VOCs measurements and indoor chemistry are proposed.

Construction of an In Vitro Air-Liquid Interface Exposure System to Assess the Toxicological Impact of Gas and Particle Phase of Semi-Volatile Organic Compounds

Anthropogenic activities and industrialization render continuous human exposure to semi-volatile organic compounds (SVOCs) inevitable. Occupational monitoring and safety implementations consider the inhalation exposure of SVOCs as critically relevant. Due to the inherent properties of SVOCs as gas/particle mixtures, risk assessment strategies should consider particle size-segregated SVOC association and the relevance of released gas phase fractions. We constructed an in vitro air-liquid interface (ALI) exposure system to study the distinct toxic effects of the gas and particle phases of the model SVOC dibutyl phthalate (DBP) in A549 human lung epithelial cells. Cytotoxicity was evaluated and genotoxic effects were measured by the alkaline and enzyme versions of the comet assay. Deposited doses were assessed by model calculations and chemical analysis using liquid chromatography tandem mass spectrometry. The novel ALI exposure system was successfully implemented and revealed the distinct genotoxic effects of the gas and particle phases of DBP. The empirical measurements of cellular deposition and the model calculations of the DBP particle phase were concordant.The model SVOC DBP showed that inferred oxidative DNA damage may be attributed to particle-related effects. While pure gas phase exposure may follow a distinct mechanism of genotoxicity, the contribution of the gas phase to total aerosol was comparably low.

Significant riverine inputs of typical plastic additives-phthalate esters from the Pearl River Delta to the northern South China Sea

Phthalate esters (PAEs) are representative additives used extensively in plastics. In this study, 15 PAEs were investigated at the eight riverine outlets of the Pearl River Delta (PRD). The total concentrations of Σ₁₅PAEs, including both the dissolved and particulate phases, ranged from 562 to 1460 ng/L and 679 ng/L-2830 ng/L in the surface and bottom layers, respectively. Dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) dominated in the dissolved and suspended particulate matter (SPM) phases, respectively, accounting for >50 % and > 80 % of Σ₁₅PAEs. Riverine input of wastewater from the PRD was possibly the primary source of the contamination. Higher levels of PAEs occurred at the eastern outlets than at the western ones. The dissolved and particulate PAEs varied seasonally, with significantly higher concentrations observed in the dry season than in the wet season. However, no significant differences of PAE levels in both phases were observed among low, medium, and high tides. The partitioning results demonstrated that SPM is important in the transportation of pollutants in estuaries, where more hydrophobic DEHP was predominantly transported by the SPM phase, while those more hydrophilic ones were regularly transported by the dissolved phase. The total annual flux of Σ₁₅PAEs through the eight outlets to the SCS reached 1390 tons.

Physiologically-based toxicokinetic modeling of human dermal exposure to diethyl phthalate: Application to health risk assessment

Diethyl phthalate (DEP) has been most frequently detected in personal care products (PCPs) as a solvent followed by indoor air as one of the semi-volatile organic compounds (SVOCs). Human exposure to DEP predominantly occurs via dermal uptake. However, the available physiologically based toxicokinetics (PBTK) models are developed in rats for risk assessment of DEP exposure resulting from the oral than dermal pathway. To address this issue, DEP in simulated PCPs was dermally administrated to five adult volunteers at real population levels. Following the construction of a dermal absorption model for DEP, the dermal PBTK modeling of DEP involving PCPs and air-to-skin exposure routes in humans was developed for the first time. The data of monoethyl phthalate (MEP) in serum or urine obtained from published human studies and this study were applied to calibrate and validate the developed dermal PBTK model. Monte Carlo simulation was used to evaluate model uncertainty. The dermal absorption fraction of DEP was obtained to be 56.2% for PCPs exposure and 100% for air-to-skin exposure, respectively. Approximate 24.9% of DEP in exposed skin became absorbed into systemic circulation. Model predictions were generally within 2-fold of the observed MEP levels in human serum or urine. Uncertainty analysis showed 90% of the predicted variability (P₉₅/P₅) fell within less than one order of magnitude. Assuming human intake of 5 mg/kg bw per day, the predicted serum area under the curve at steady state of DEP from the dermal route was 1.7 (PCPs) and 2.4 (air) times of those from the peroral route, respectively. It suggested that dermal exposure to DEP would pose greater risk to human health compared with oral exposure. The application of the developed dermal PBTK model provides a valuable insight into health risk assessment of DEP in humans.

Cytotoxicity Assessment of Nanoplastics and Plasticizers Exposure in In Vitro Lung Cell Culture Systems—A Systematic Review

Emerging contaminants such as nanoplastics (NPs), as well as manufacturing by-products such as plasticizers, have gained global attention and concern due to their limited biodegradability and their potential impact on human health, in particular the effects on respiratory tissue. In parallel, in vitro cell culture techniques are key to the assessment and characterization of toxic effects and cellular mechanisms in different types of tissues and should provide relevant information to understand the hazardous potential of these emergent contaminants. This systematic review presents the main results on the current knowledge of the effects of NPs and plasticizers on lung cells, as assessed with the use of in vitro cell culture techniques. From the selected studies (n = 10), following the PRISMA approach, it was observed that cell viability was the most frequently assessed endpoint and that most studies focused on epithelial cells and exposures to polystyrene (PS). It was observed that exposure to NPs or plasticizers induces cytotoxicity in a dose-dependent manner, regardless of the size of the NPs. Furthermore, there is evidence that the characteristics of NPs can affect the toxic response by promoting the association with other organic compounds. As such, further in vitro studies focusing on the combination of NPs with plasticizers will be essential for the understanding of mechanisms of NPs toxicity.

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.

PM2.5-bound phthalates and phthalate substitutes in a megacity of southern China: spatioseasonal variations, source apportionment, and risk assessment

Plasticizers are ubiquitous pollutants in the environment, whereas few efforts have been made to elucidate their emission sources in the atmosphere. In this research, the spatioseasonal variations and sources of particle-bound (PM_2.5) phthalates (PAEs) and their substitutes (APs) at residential sites in seven districts and at four potential point-source sites across a megacity in South China were revealed. The total concentrations of PAEs ranging from 10.7 to 528 ng/m³ were substantially higher than those of APs (1.45.58.5 ng/m³). Significant spatial variations in the concentrations of the pollutants were observed, which were generally higher at the sites with intensive industrial activities and the point-source sites. Most atmospheric plasticizer levels peaked in summer, probably due to the temperature-promoted volatilization. Seven sources of plasticizers were identified by the positive matrix factorization (PMF) model. The sources in less industrialized districts are mainly associated with domestic and commercial emissions and with industry in the industrialized districts. Specifically, plastics and personal care products together contributed 60% of the plasticizers in the atmosphere of this city, followed by solvents and polyester industry sources. The incremental lifetime cancer risk of inhalation exposure to bis(2-ethylhexyl) phthalate in the study city is below the acceptable level. Relatively higher risks were found for residents living around sites with intensive industrial activities and around wastewater treatment plant.

Dynamic variations of phthalate esters in PM2.5 during a pollution episode

Phthalate esters (PAEs) as hazardous air pollutants can be easily released during the life cycle of plastic products. In this study, a thermal desorption aerosol comprehensive two-dimensional gas chromatography mass spectrometer coupled with a dual-trap was developed and used to measure the hourly-resolved PAEs characteristics in atmospheric PM_2.5 at an urban site. Dimethyl phthalate (DMP), diethyl (DEP), dibutyl (DnBP), benzyl butyl (BBP), di(2-ethylhexyl) (DEHP), and di-n-octyl phthalate (DnOP) in PM_2.5 were analyzed. The most abundant compounds were DEHP and DMP, followed by DnBP and DEP. The mass concentrations of the detected PAEs are comparable to those at other urban sites measured using offline methods with a lower time resolution. The concentrations of PAEs showed intense change with the variation of PM_2.5 mass concentration. The proportion of DEHP increased while that of DMP decreased with the increase in PM_2.5 pollution. Positive correlations between PAEs and PM_2.5, organic carbon, and elemental carbon were observed, while PAEs had negative correlation with the ambient temperature. Our observation provides evidences on understanding the volatile and semi-volatile PAEs in the ambient aerosols.

Emission characteristics, sources, and airborne fate of speciated organics in particulate matters in a Hong Kong residence

A growing number of studies warn of the adverse health effects of indoor particulate matters (PM). However, little is known about the molecular compositions and emission characteristics of PM-bound organics (OM) indoors, a critical group of species with highest concentration and complexity in indoor PM. In a Hong Kong residence where prescribed activities were performed with normal frequency and intensity, we found that the activities significantly elevated not only the total concentration but also the fraction of OM in indoor PM. However, the concentration of the total PM-bound OM outdoors (10.3 ± 0.7 μg/m³ ) surpassed that for the indoor counterpart during the undisturbed period (8.2 ± 0.1 μg/m³ ), that is, period when there was no activity with high emission of PM but the residual effects of previous activities might remain. Emissions of indoor activities involving combustion or high-temperature processes significantly elevated the indoor-to-outdoor (I/O) ratios for a majority of organic species. In addition, gas-to-particle partitioning, secondary formation, carrying-over (residues of pollutants in the air), and re-emission also modulated the I/O ratios of some compounds. Chemically comprehensive emission profiles of speciated organics were obtained for 5 indoor activities in the residence. While the indoor contribution to PM-bound OM was estimated to be not higher than 13.1% during the undisturbed period, carrying-over and/or re-emission seemed to exist for certain compounds emitted from cigarette smoking and incense burning. This study enhances knowledge on emissions and airborne fate of speciated organics in indoor PM.

Firefighter exposures to potential endocrine disrupting chemicals measured by military-style silicone dog tags

Studies suggest that exposure to potential endocrine disrupting chemicals (pEDCs) may contribute to adverse health outcomes, but pEDC exposures among firefighters have not been fully characterized. Previously, we demonstrated the military-style silicone dog tag as a personal passive sampling device for assessing polycyclic aromatic hydrocarbon exposures among structural firefighters. This follow-up analysis examined the pEDC exposures based on department call volume, duty shift, and questionnaire variables. Structural firefighters (n = 56) were from one high and one low fire call volume department (Kansas City, MO metropolitan area) and wore separate dog tags while on- and off-duty (n_dogtags = 110). The targeted 1530 analyte semi-quantitative screening method was conducted using gas chromatography mass spectrometry (n_pEDCs = 433). A total of 47 pEDCs were detected, and several less-frequently-detected pEDCs (<75%) were more commonly detected in off- compared to on-duty dog tags (conditional logistic regression). Of the 11 phthalates and fragrances detected most frequently (>75%), off-duty pEDC concentrations were strongly correlated (r = 0.31-0.82, p < 0.05), suggesting co-applications of phthalates and fragrances in consumer products. Questionnaire variables of "regular use of conventional cleaning products" and "fireplace in the home" were associated with select elevated pEDC concentrations by duty shift (paired t-test). This suggested researchers should include detailed questions about consumer product use and home environment when examining personal pEDC exposures.

Exploring personal chemical exposures in China with wearable air pollutant monitors: A repeated-measure study in healthy older adults in Jinan, China

The health impact of airborne contaminants has been challenging to assess due to current limitations in measurement technologies. The emergence of wearable passive samplers coupled with high resolution mass spectrometry (HR-MS) chemical analysis has enabled comprehensive characterization of personal exposures. We conducted a repeated-measure study among 84 older adults in Jinan, China, as part of the Biomarkers for Air Pollutants Exposure (China BAPE) study. Study objectives were: 1) to characterize the occurrence, magnitude, and distribution of personal exposure to airborne contaminants; 2) to evaluate the temporal variation of chemical exposures across the study population; and 3) to identify behavioral and environmental factors that influence the observed variance in chemical exposures. The FreshAir wristband was worn by participants for three consecutive days each month from September 2018 to January 2019 and collected with paired time-activity logs. Passive air samplers were also deployed in parallel at a local outdoor air monitoring station. Spearman's Rho trend test and trajectory cluster analysis were used to identify exposure trends and variation patterns, respectively. Out of the 70 airborne compounds of potential concern screened, 26 compounds from 10 chemical classes were found to be above detection thresholds across >70% of the study population. Personal exposures were predominantly characterized by nine polycyclic aromatic hydrocarbons (PAHs), four phthalates, three nitroaromatics, and two volatile organic compounds (VOCs). Phthalate personal exposures were positively correlated with outdoor temperatures while the inverse relationship was observed for certain PAHs (p < 0.05). Specifically, dimethyl phthalate (r_s = 0.31) decreased as temperatures declined, while nitrobenzene (r_s = -0.35) and naphthalene (r_s = -0.40) increased as temperatures decreased. Compared to levels measured at the outdoor air monitoring site, personal exposure of phthalates was elevated (p < 0.05) and hexachlorobutadiene was lower across participants (p < 0.01). Personal exposure of these chemicals was further found to be weakly associated with daily duration participants spent outdoors. Individuals formed distinct clusters based on trajectories of chemical exposures across the sampling period (September to January), potentially suggestive of distinct emission sources. In conclusion, we demonstrate the feasibility of characterizing the occurrence and magnitude of personal exposure to airborne chemical contaminants using passive wristband samplers. The temporal variability of these personal exposure profiles was highlighted and with distinct trends identified across different groups of individuals. Future studies will integrate this data with other omics datasets collected from this population of Chinese older adults to investigate associations between exposure profiles and health relevant biomarkers, to provide evidence in feasibility of disease prevention through environmental improvements.

Three-dimensional non-isothermal numerical model for predicting semi-volatile organic compound transport process in a room

In this paper, a three-dimensional non-isothermal computational model for predicting indoor SVOC distribution is proposed, considering the effects of turbulence diffusion and suspended particles. The realizable k-ε model is introduced for turbulent flow simulation in a room. The Euler-Euler method is adopted to deal with the gas-particle two-phase flow coupled problem. Inertia slip velocity and irreversible first-order absorption boundary are employed for more accurate prediction of particle motion. The simulated curve of outlet gas-phase di-2-ethylhexyl phthalate (DEHP) concentration with emission time is verified by available experimental data. The emission process of DEHP in a 15 m² room in Beijing during 100 days with or without air cleaner is simulated by the developed model considering air leak through window and door gaps. It is found that if the air cleaner keeps on all the time during 100 days the gas-phase DEHP concentration in the room will tend to be uniform, while the emission process is far from equilibrium without an air cleaner even the emission lasts 100 days. Results also suggest that floor heating, decrease of particle concentration, weaken of heat transfer, enhancement of mass transfer, and air infiltration in window gap contribute to decrease DEHP concentration.

On the Flip Side of Mask Wearing: Increased Exposure to Volatile Organic Compounds and a Risk-Reducing Solution

Surgical masks have been worn by the public worldwide during the COVID-19 pandemic, yet hazardous chemicals in the petroleum-derived polymer layer of masks are currently ignored and unregulated. These organic compounds pose potential health risks to the mask wearer through dermal contact or inhalation. Here, we show that surgical masks from around the world are loaded with semivolatile and volatile organic compounds (VOCs), including alkanes, polycyclic aromatic hydrocarbons (PAHs), phthalate esters, and reactive carbonyls at ng to μg/mask levels. Naphthalene was the most abundant mask-borne PAH, accounting for over 80% of total PAH levels; acrolein, a mutagenic carbonyl, was detected in most of the mask samples, and di(2-ethylhexyl) phthalate, an androgen antagonist, was detected in one-third of the samples. Furthermore, there is large mask-to-mask variability of the residue VOCs, revealing the uneven quality of masks. We confirm that masks containing more residue VOCs lead to significantly higher exposure levels and associated disease risks to the wearer, which should warrant the attention of the general public and regulatory agencies. We find that heating the masks at 50 °C for as short as 60 min lowers the total VOC content by up to 80%, providing a simple method to limit our exposure to mask-borne VOCs.

Textile Washing Conveys SVOCs from Indoors to Outdoors: Application and Evaluation of a Residential Multimedia Model

Indoor environments have elevated concentrations of numerous semivolatile organic compounds (SVOCs). Textiles provide a large surface area for accumulating SVOCs, which can be transported to outdoors through washing. A multimedia model was developed to estimate advective transport rates (fluxes) of 14 SVOCs from indoors to outdoors by textile washing, ventilation, and dust removal/disposal. Most predicted concentrations were within 1 order of magnitude of measurements from a study of 26 Canadian homes. Median fluxes to outdoors [μg·(year·home)^-1] spanned approximately 4 orders of magnitude across compounds, according to the variability in estimated aggregate emissions to indoor air. These fluxes ranged from 2 (2,4,4'-tribromodiphenyl ether, BDE-28) to 30 200 (diethyl phthalate, DEP) for textile washing, 12 (BDE-28) to 123 200 (DEP) for ventilation, and 0.1 (BDE-28) to 4200 (bis(2-ethylhexyl) phthalate, DEHP) for dust removal. Relative contributions of these pathways to the total flux to outdoors strongly depended on physical-chemical properties. Textile washing contributed 20% tris-(2-chloroisopropyl)phosphate (TCPP) to 62% tris(2-butoxyethyl)phosphate (TBOEP) on average. These results suggest that residential textile washing can be an important transport pathway to outdoors for SVOCs emitted to indoor air, with implications for human and ecological exposure. Interventions should try to balance the complex tradeoff of textile washing by minimizing exposures for both human occupants and aquatic ecosystems.

Fates and spatial variations of accumulation mode particles in a multi-zone indoor environment during the HOMEChem campaign

Studying the indoor dynamics that impact particles is crucial in order to understand indoor air chemistry and assess overall human exposure to particles. This work investigates spatial gradients in particle concentration, caused by indoor transport and loss mechanisms. We conducted a variety of cooking experiments during the House Observations of Microbial and Environmental Chemistry (HOMEChem) campaign in June 2018 that allowed us to probe these mechanisms. We measured size-resolved (0.06-1 μm and 0.13-3 μm) particle number concentrations from cooking experiments using optical instruments at four locations throughout the house simultaneously. The particle number concentration in the kitchen was 40 ± 10% and 70 ± 10% higher than the concentrations in the living room and the bedroom, respectively. There was a minor size dependence, with larger differences in the smaller sizes of the accumulation mode (0.1-2.5 μm) than the larger end of the range. Dilution accounts for the majority of these concentration differences. Surface deposition was the dominant fate of particles within a zone, with observed deposition velocities ranging from 0.1 to 0.6 m h-1.

Deep Dive into Plastic Monomers, Additives, and Processing Aids

A variety of chemical substances used in plastic production may be released throughout the entire life cycle of the plastic, posing risks to human health, the environment, and recycling systems. Only a limited number of these substances have been widely studied. We systematically investigate plastic monomers, additives, and processing aids on the global market based on a review of 63 industrial, scientific, and regulatory data sources. In total, we identify more than 10'000 relevant substances and categorize them based on substance types, use patterns, and hazard classifications wherever possible. Over 2'400 substances are identified as substances of potential concern as they meet one or more of the persistence, bioaccumulation, and toxicity criteria in the European Union. Many of these substances are hardly studied according to SciFinder (266 substances), are not adequately regulated in many parts of the world (1'327 substances), or are even approved for use in food-contact plastics in some jurisdictions (901 substances). Substantial information gaps exist in the public domain, particularly on substance properties and use patterns. To transition to a sustainable circular plastic economy that avoids the use of hazardous chemicals, concerted efforts by all stakeholders are needed, starting by increasing information accessibility.

High-Resolution Exposure Assessment for Volatile Organic Compounds in Two California Residences

Time spent in residences substantially contributes to human exposure to volatile organic compounds (VOCs). Such exposures have been difficult to study deeply, in part because VOC concentrations and indoor occupancy vary rapidly. Using a fast-response online mass spectrometer, we report time-resolved exposures from multi-season sampling of more than 200 VOCs in two California residences. Chemical-specific source apportionment revealed that time-averaged exposures for most VOCs were mainly attributable to continuous indoor emissions from buildings and their static contents. Also contributing to exposures were occupant-related activities, such as cooking, and outdoor-to-indoor transport. Health risk assessments are possible for a subset of observed VOCs. Acrolein, acetaldehyde, and acrylic acid concentrations were above chronic advisory health guidelines, whereas exposures for other assessable species were typically well below the guideline levels. Studied residences were built in the mid-20th century, indicating that VOC emissions even from older buildings and their contents can substantially contribute to occupant exposures.

Emerging investigator series: chemical and physical properties of organic mixtures on indoor surfaces during HOMEChem

Organic films on indoor surfaces serve as a medium for reactions and for partitioning of semi-volatile organic compounds and thus play an important role in indoor chemistry. However, the chemical and physical properties of these films are poorly characterized. Here, we investigate the chemical composition of an organic film collected during the HOMEChem campaign, over three cumulative weeks in the kitchen, using both Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) and offline Aerosol Mass Spectrometry (AMS). We also characterize the viscosity of this film using a model based on molecular formulas as well as poke-flow measurements. We find that the film contains organic material similar to cooking organic aerosol (COA) measured during the campaign using on-line AMS. However, the average molecular formula observed using FT-ICR MS is ∼C50H90O11, which is larger and more oxidized than fresh COA. Solvent extracted film material is a low viscous semisolid, with a measured viscosity <104 Pa s. This is much lower than the viscosity model predicts, which is parametrized with atmospherically relevant organic molecules, but sensitivity tests demonstrate that including unsaturation can explain the differences. The presence of unsaturation is supported by reactions of film material with ozone. In contrast to the solvent extract, manually removed material appears to be highly viscous, highlighting the need for continued work understanding both viscosity measurements as well as parameterizations for modeled viscosity of indoor organic films.

Phthalate levels in indoor dust and associations to croup in the SELMA study

Phthalates are ubiquitous indoor pollutants which have been associated with child airway disease although results are inconclusive. This study examined associations between phthalate levels in residential indoor dust and croup during infancy. Settled indoor dust was collected in 482 homes of 6-month-old infants in the Swedish Environmental Longitudinal, Mother and child, Asthma and allergy (SELMA) study and analysed for seven phthalates and one phthalate replacement using gas chromatography tandem mass spectrometry. The incidence of parental reported croup at 12 months was 6.4% for girls and 13.4% for boys. Associations between phthalate dust levels and croup were analysed by logistic regression adjusted for potential confounders. We found significant associations between di-ethyl phthalate (DEP) and di-ethyl-hexyl phthalate (DEHP) in residential dust and parental reported croup (adjusted odds ratio (aOR) = 1.71; 95% CI: 1.08-2.73 and 2.07; 1.00-4.30, respectively). Stratified results for boys showed significant associations between DEP and butyl-benzyl phthalate (BBzP) in dust and infant croup (aOR = 1.86; 95% CI: 1.04-3.34 and 2.02; 1.04-3.90, respectively). Results for girls had questionable statistical power due to few cases. Our results suggest that exposure to phthalates in dust is a risk factor for airway inflammatory responses in infant children.

Real-time organic aerosol chemical speciation in the indoor environment using extractive electrospray ionization mass spectrometry

Understanding the sources and composition of organic aerosol (OA) in indoor environments requires rapid measurements, since many emissions and processes have short timescales. However, real-time molecular-level OA measurements have not been reported indoors. Here, we present quantitative measurements, at a time resolution of five seconds, of molecular ions corresponding to diverse aerosol-phase species, by applying extractive electrospray ionization mass spectrometry (EESI-MS) to indoor air analysis for the first time, as part of the highly instrumented HOMEChem field study. We demonstrate how the complex spectra of EESI-MS are screened in order to extract chemical information and investigate the possibility of interference from gas-phase semivolatile species. During experiments that simulated the Thanksgiving US holiday meal preparation, EESI-MS quantified multiple species, including fatty acids, carbohydrates, siloxanes, and phthalates. Intercomparisons with Aerosol Mass Spectrometer (AMS) and Scanning Mobility Particle Sizer suggest that EESI-MS quantified a large fraction of OA. Comparisons with FIGAERO-CIMS shows similar signal levels and good correlation, with a range of 100 for the relative sensitivities. Comparisons with SV-TAG for phthalates and with SV-TAG and AMS for total siloxanes also show strong correlation. EESI-MS observations can be used with gas-phase measurements to identify co-emitted gas- and aerosol-phase species, and this is demonstrated using complementary gas-phase PTR-MS observations.

Chemical Composition, Spatial Homogeneity, and Growth of Indoor Surface Films

Organic films on indoor surfaces are ubiquitous, but details about their composition and growth over timescales less than a month are not fully understood. To address these gaps in understanding, organic film samples in an apartment unit were collected over the course of 17 days using passive samplers and analyzed in a non-targeted manner using direct analysis in real-time mass spectrometry (DART-MS). Overall, the chemical composition observed across various locations within the apartment are very similar. Mass spectra also show clear evidence for the growth of semi-volatile compounds from natural sources and consumer products, such as carboxylic acids and plasticizers. Certain compounds show evidence for equilibration, mostly consistent with surface partitioning models based on octanol-air partition coefficients (K_oa). Compounds which have higher molecular weight or larger K_oa values tend to equilibrate later, leading to an overall shift in the composition of the film as a function of collection time. Growth rates of film thickness are at least 0.05 nm/day based on a limited number of individually calibrated ions.

Phthalates and Bisphenol A: Presence in Blood Serum and Follicular Fluid of Italian Women Undergoing Assisted Reproduction Techniques

Background: folliculogenesis is a strictly regulated process that may be affected by endocrine disrupting chemicals (EDCs) through sometimes not so clear molecular mechanisms. Methods: we conducted a multicentric observational study involving six fertility centers across Italy, prospectively recruiting 122 women attending a fertility treatment. Recruited women had age ≤42 years, and normal ovarian reserve. Blood and follicular fluid samples were taken for EDCs measurement using liquid chromatography tandem mass spectrometry and each woman completed an epidemiological questionnaire. Results: The main EDCs found were monobutyl phthalate (MBP) (median blood: 8.96 ng/mL, follicular fluid 6.43 ng/mL), monoethylhexyl phthalate (MEHP) (median blood: 9.16 ng/mL, follicular fluid 7.68 ng/mL) and bisphenol A (BPA) (median blood: 1.89 ng/mL, follicular fluid 1.86 ng/mL). We found that serum MBP concentration was significantly associated with the considered area (p < 0.001, adj. mean: 7.61 ng/mL, 14.40 ng/mL, 13.56 ng/mL; Area 1: Milan–Turin, Area 2: Rome–Naples; Area 3: Catania–Bari, respectively) but negatively with home plastic food packaging (p = 0.004). Follicular MBP was associated with irregular cycles (p = 0.019). No association was detected between EDCs and eating habits and other clinical and epidemiological features. Conclusions: This study represents the first Italian biomonitoring of plastic EDCs in follicular fluid, laying the basis for future prospective evaluation on oocyte quality before assisted reproduction techniques (ART).

Transient Multimedia Model for Investigating the Influence of Indoor Human Activities on Exposure to SVOCs

Empirical evidence suggests that human occupants indoors, through their presence and activities, can influence the dynamics of semivolatile organic compounds (SVOCs). To better understand these dynamics, a transient multimedia human exposure model was developed (Activity-Based Indoor Chemical Assessment Model (ABICAM)). This model parametrizes mass-balance equations as functions of time-dependent human activities. As a case study, ABICAM simulated exposures of an archetypal adult and toddler over 24 h to diethyl phthalate (DEP), butyl benzyl phthalate (BBzP), and di-2-ethylhexyl phthalate (DEHP) that span a wide range of gas-particle partitioning tendencies. Under baseline (no activities beyond respiration), the toddler's time-average internal doses were three to four times higher than the adult's, due to differences in physical human attributes (e.g., inhalation rate). When time-dependent activities were considered, interindividual (e.g., adult vs toddler) variability was accentuated by up to a factor of 3 for BBzP. Activities with the greatest influence on time-average internal dose were showering (-71% for BBzP), cooking (+27% for DEHP), and sleeping (-26% for DEHP). Overall, the results support the hypotheses that (1) transient indoor activities can give rise to intraindividual variability in estimated internal doses of SVOCs, and (2) interindividual variability in such exposure can result from differences in activity patterns and physical human attributes, according to a compound's physical-chemical properties.

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.

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.

Surface reservoirs dominate dynamic gas-surface partitioning of many indoor air constituents

Human health is affected by indoor air quality. One distinctive aspect of the indoor environment is its very large surface area that acts as a poorly characterized sink and source of gas-phase chemicals. In this work, air-surface interactions of 19 common indoor air contaminants with diverse properties and sources were monitored in a house using fast-response, on-line mass spectrometric and spectroscopic methods. Enhanced-ventilation experiments demonstrate that most of the contaminants reside in the surface reservoirs and not, as expected, in the gas phase. They participate in rapid air-surface partitioning that is much faster than air exchange. Phase distribution calculations are consistent with the observations when assuming simultaneous equilibria between air and large weakly polar and polar absorptive surface reservoirs, with acid-base dissociation in the polar reservoir. Chemical exposure assessments must account for the finding that contaminants that are fully volatile under outdoor air conditions instead behave as semivolatile compounds indoors.