Estimating exposures to indoor contaminants using residential dust

Nail salon dust reveals alarmingly high photoinitiator levels: Assessing occupational risks

Photoinitiators (PIs) are chemical additives that generate active substances, such as free radicals to initiate photopolymerization. Traditionally, polymerization has been considered a green technique that seldomly generates contaminants. However, many researches have confirmed toxicity effects of PIs, such as carcinogenicity, cytotoxicity, endocrine disrupting effects. Surprisingly, we found high levels of PIs in indoor dust. Our analysis revealed comparable levels of PIs in dust from printing shops (geometric mean, GM: 1.33 ×103 ng/g) and control environments (GM: 874 ng/g), underscoring the widespread presence of PIs across various settings. Alarmingly, in dust samples from nail salons, PIs were detected at total concentrations ranging from 610 to 1.04 × 107 ng/g (GM: 1.87 ×105 ng/g), significantly exceeding those in the control environments (GM: 1.43 ×103 ng/g). Nail salon workers' occupational exposure to PIs through dust ingestion was estimated at 4.86 ng/kg body weight/day. Additionally, an in vitro simulated digestion test suggested that between 10 % and 42 % of PIs present in ingested dust could become bioaccessible to humans. This is the first study to report on PIs in the specific environments of nail salons and printing shops. This study highlights the urgent need for public awareness regarding the potential health risks posed by PIs to occupational workers, marking an important step towards our understanding of environmental pollution caused by PIs.

Predictors of pesticide levels in carpet dust collected from child care centers in Northern California, USA

BACKGROUND

Young children may be exposed to pesticides in child care centers, but little is known about determinants of pesticide contamination in these environments.

OBJECTIVE

Characterize pesticide contamination in early care and education (ECE) centers and identify predictors of pesticide concentrations and loading in dust collected from classroom carpets.

METHODS

Carpet dust samples were collected from 51 licensed child care centers in Northern California and analyzed for 14 structural and agricultural pesticides. Program characteristics were collected through administration of director interviews and observational surveys, including an integrated pest management (IPM) inspection. Pesticide use information for the prior year was obtained from the California Department of Pesticide Regulation to characterize structural applications and nearby agricultural pesticide use.

RESULTS

The most frequently detected pesticides were cis-permethrin (98%), trans-permethrin (98%), bifenthrin (94%), fipronil (94%), and chlorpyrifos (88%). Higher bifenthrin levels were correlated with agricultural applications within 3 kilometers, and higher fipronil levels were correlated with professional pesticide applications in the prior year. In multivariable models, higher IPM Checklist scores were associated with lower loading of chlorpyrifos and permethrin. Placement of the sampled area carpet was also a predictor of chlorpyrifos loading. The strongest predictor of higher pesticide loading for the most frequently detected pesticides was location in California's San Joaquin Valley.

SIGNIFICANCE

Our findings contribute to the growing understanding that pesticides are ubiquitous in children's environments. Pesticide levels in carpet dust were associated with some factors that ECE directors may have control over, such as IPM practices, and others that are beyond their control, such as geographic location. IPM is an important tool that has the potential to reduce pesticide exposures in ECE environments, even for pesticides no longer in use.

IMPACT

One million children in California under six years old attend child care programs where they may spend up to 40 h per week. Children are uniquely vulnerable to environmental contaminants; however early care settings are under researched in environmental health studies. Little is known about predictors of pesticide levels found in environmental samples from child care facilities. This study aims to identify behavioral and environmental determinants of pesticide contamination in California child care centers. Findings can empower child care providers and consumers and inform decision makers to reduce children's exposures to pesticides and promote lifelong health.

Gender-specific associations between mixture of polycyclic aromatic hydrocarbons and telomere length

Evidence shows the relationships of individual environmental PAHs by their urinary metabolites with relative telomere length (RTL), which may be affected by biological gender differences. Since plasma parent PAHs are not metabolized, it may reflect human exposure to PAHs more realistically in daily life. Thus, exploring joint associations between plasma parent PAHs and RTL is urgent, which may identify the major contributor to its adverse effect. In this study, 2577 participants were obtained from the Henan Rural Cohort. The level of PAHs in blood samples was detected by gas chromatography coupled with tandem mass spectrometry. RTL in blood samples was detected by quantitative polymerase chain reaction. Generalized linear models or quantile g-computation were performed to evaluate the associations between the individual or a mixture of PAHs and RTL. Results from generalized linear models showed that each unit increment in BghiP value corresponded to a 0.098 (95%CI: 0.067, 0.129) increment in RTL for men; each unit increment in BaP, BghiP and Flu value corresponded to a 0.041 (95%CI: 0.014, 0.068), 0.081 (95%CI: 0.055, 0.107) and 0.016 (95%CI: 0.005, 0.027) increment in RTL for women. Results from quantile-g computation revealed that each one-quantile increment in the mixture of 10 PAHs corresponded to a 0.057 (95%CI: 0.021, 0.094) and 0.047 (95%CI: 0.003, 0.091) increment in RTL values of women and men, but these associations were mainly ascribed to three PAHs for women (BaP, Flu and BghiP) and men (BaP, BghiP and Pyr), respectively. Similar results were found in smoking men and cooking women without smoking. Our study found that exposure to 10 PAHs mixture was positively associated with RTL across gender, mainly attributed to Flu, BaP and BghiP, implicating that gender-specific associations may be ascribed to tobacco and cooking smoke pollution. The findings provided clues for effective measures to control PAHs pollutants-related aging disease.Clinical trial registration The Henan Rural Cohort Study has been registered at the Chinese Clinical Trial Register (Registration number: ChiCTR-OOC-15006699). Date of registration: 06 July 2015. http://www.chictr.org.cn/showproj.aspx?proj=11375 .

Gas-particle partitioning of organophosphate esters in indoor and outdoor air and its implications for individual exposure

The extensive utilization of organophosphate esters (OPEs) has resulted in their widespread presence in the environment, raising concerns about potential human health risks. In this study, 13 OPEs were analyzed in both gas and particle phases as well as in indoor and outdoor atmospheric environments. Moreover, human exposure to OPEs were investigated within a university environment, focusing on forehead contact and individual PM2.5 inhalation. The results showed similar distribution patterns of OPEs indoors and outdoors, although higher concentrations were found indoors. The average atmospheric concentration of ∑OPEs (combining particle and gaseous OPEs) was 1575 pg/m3 in the outdoor environment and 6574 pg/m3 ∑OPEs in the indoor microenvironments. The overwhelming majority of OPEs exhibit a pronounced propensity to adsorb onto PM2.5 particles. Notably, the concentration of OPEs on the forehead differed significantly from that in the atmospheric environment, whereas individual PM2.5 exposure was consistent with the concentration of indoor PM2.5. Intriguingly, some OPEs with high octanol-water partition coefficient (log Kow) were not detected in the environment but found on human foreheads. Gas-particle partitioning was predicted using the Harner-Bidleman and Li-Ma-Yang models and the results were in agreement with the monitoring data for approximately half of the OPE monomers. Correlations between OPEs exposure and gas-particle partitioning were found to be more significant for novel OPEs. No non-cancer risk to humans through individual exposure to OPEs was identified via forehead exposure or inhalation. The previously unreported relationship between individual exposure and the environmental occurrence of traditional and novel OPEs demonstrated in this study highlights the importance of evaluating the potential health risks associated with actual OPE exposure.

An extensive assessment on the distribution pattern of organic contaminants in the aerosols samples in the Middle East

Nowadays, in spite of a significant progress in indoor air quality (IAQ), an assessable and predictive understanding of atmospheric aerosol sources, chemical composition, transformation processes, and environmental effects are still rather incomplete and therefore signifies a key research challenge in the atmospheric science. Thus, the current comprehensive review is concerned with the dominant sources, organic compositions, and potential health impacts of the organic contaminants in the atmospheric particle matters (PMs) in the Middle East (ME). The ME contributes a major impact of organic contaminants on the atmosphere along with other Asian and African countries. In the Gulf Cooperation Council (GCC) countries, the communities are noted for being the center of the great majority of the world’s oil reserves and infrastructure for producing crude oil. The review starts with a historical outlook on the scientific queries regarding major source of organic contaminants to the atmospheric aerosols over the past centuries, followed by an explanation of the distribution, sources, transformation processes, and chemical and physical properties as they are formerly assumed. Natural product chemicals from biota, manufactured organic compounds including pesticides, chlorinated hydrocarbons, and lubricants, as well as organic compounds from the use and combustion of fossil fuels make up the aerosol contamination. Thus, in the recent years, IAQ may be seen as a significant health issue because of the increase in industrial activity. Fugitive emissions from industrial processes, as well as natural and anthropogenic emissions from other sources such as forest fires, volcanic eruptions, incomplete combustion of fossil fuels, wood, agricultural waste, or leaves, are typical sources of organic pollutants to the aerosol. In the spring and early summer in the GCC countries, aerosol concentration increases because of dust storms; however, in winter, there are fewer dust storms and higher precipitation rates, and aerosol concentrations are lower. Significances of future research and major suggestions are also outlined to narrow the gap between the present understanding of the contribution of both anthropogenic and biogenic aerosols to radiative forcing, resulting from the spatial nonuniformity, intermittency of sources, unresolved composition, and reactivity.

Silicone wristbands as personal passive sampling devices: Current knowledge, recommendations for use, and future directions

Personal chemical exposure assessment is necessary to determine the frequency and magnitude of individual chemical exposures, especially since chemicals present in everyday environments may lead to adverse health outcomes. In the last decade, silicone wristbands have emerged as a new chemical exposure assessment tool and have since been utilized for assessing personal exposure to a wide range of chemicals in a variety of populations. Silicone wristbands can be powerful tools for quantifying personal exposure to chemical mixtures in a single sample, associating exposure with health outcomes, and potentially overcoming some of the challenges associated with quantifying the chemical exposome. However, as their popularity grows, it is crucial that they are used in the appropriate context and within the limits of the technology. This review serves as a guide for researchers interested in utilizing silicone wristbands as a personal exposure assessment tool. Along with briefly discussing the passive sampling theory behind silicone wristbands, this review performs an in-depth comparison of wristbands to other common exposure assessment tools, including biomarkers of exposure measured in biospecimens, and evaluates their utility in exposure assessments and epidemiological studies. Finally, this review includes recommendations for utilizing silicone wristbands to evaluate personal chemical exposure and provides suggestions on what research is needed to recognize silicone wristbands as a premier chemical exposure assessment tool.

Distribution and source of and health risks associated with polybrominated diphenyl ethers in dust generated by public transportation

Carcinogenic and neurotoxic polybrominated diphenyl ethers (PBDEs) are environmentally ubiquitous and have been widely investigated. However, little is understood regarding their pollution status, sources, and potential risk to persons in public transportation microenvironments (PTMs). We collected 60 dust samples from PTMs and then selected four materials typical of bus interiors to determine the sources of PBDEs in dust using principal component analysis coupled with Mantel tests. We then evaluated the risk of PBDEs to public health using Monte Carlo simulations. We found that PBDE concentrations in dust were 2-fold higher in buses than at bus stops and that brominated diphenyl ether (BDE)-209 was the main pollutant. The number of buses that passed through a bust stop contributed to the extent of PBDE pollution, and the primary potential sources of PBDEs in dust were plastic handles and curtains inside buses; BDE-209 and BDE-154 were the main contributors of pollution. We found that health risk was 8-fold higher in toddlers than in adults and that the reference doses of PBDEs in dust were far below the United States Environmental Protection Agency limits. Our findings provide a scientific basis that may aid in preventing PBDE pollution and guiding related pollution management strategies in PTMs.

An overview of organic contaminants in indoor dust, their health impact, geographical distribution and recent extraction/analysis methods

People spend a substantial proportion of their time indoors; therefore, exposure to contaminants in indoor dust is persistent and profuse. According to the findings of recent studies, contaminants such as flame retardants (FRs), organochlorines (OCs), and phthalate esters (PAEs) are more prevalent in indoor dust. The discrepancy in the geographical distribution of these chemicals indicates country-specific applications. However, many studies have revealed that chlorophosphates, polychlorinated biphenyls (PCBs) and di-2-ethylhexyl phthalate are frequently detected in indoor dust throughout the world. Although some chemicals (e.g., OCs) were banned/severely restricted decades ago, they have still been detected in indoor dust. These organic contaminants have shown clear evidence of carcinogenic, neurotoxic, immunogenic, and estrogenic activities. Recent extraction methods have shown their advantages, such as high recoveries, less solvent consumption, less extraction time and simplicity of use. The latest separation techniques such as two-dimensional gas/liquid chromatography, latest ionization techniques (e.g., matrix-assisted laser desorption/ionization (MALDI)), and modern techniques of mass spectrometry (e.g., tandem mass spectrometry (MS/MS), time-of-flight (TOF) and high-resolution mass spectrometry (HRMS)) improve the detection limits, accuracy, reproducibility and simultaneous detection of organic contaminants. For future perspectives, it is suggested that the importance of the study of dust morphology for comprehensive risk analysis, introducing standard reference materials to strengthen the analytical methods, adopt common guidelines for comparison of research findings and the importance of dust analysis in the developing world since lack of records on the production and usage of hazardous substances. Such measures will help to evaluate the effectiveness of prevailing legislations and to set up new regulations.

Detection of Mycotoxins in Highly Matrix-Loaded House-Dust Samples by QTOF-HRMS, IM-QTOF-HRMS, and TQMS: Advantages and Disadvantages

The analysis of (trace) contaminants in environmental samples represents an important tool for exposure assessment and for the evaluation of potential risks to human health. Currently, mass spectrometric detection using triple quadrupole (TQMS) systems is the established method of choice. However, screening methods using high resolution mass spectrometry (HRMS) find increasing application as they provide advantages such as enhanced selectivity. A complex composition of environmental samples is known to have enormous effects on mass analyzers. The present work therefore compares the impact of a highly matrix-loaded sample material like house-dust on the performance of mass spectrometric detection of the emerging indoor contaminant group of mycotoxins by quadrupole time-of-flight (QTOF) and TQMS after ultrahigh-performance liquid chromatographic separation. Furthermore, the role of ionization efficiencies of different ion sources in instrument sensitivity was compared using an electrospray ionization source and a newly developed heated electrospray ion source (Bruker VIP-HESI) during QTOF experiments. Finally, it was evaluated whether an additional dimension of separation enables increased sensitivity in QTOF-HRMS detection by applying mycotoxins in house-dust to an (trapped) ion mobility spectrometry instrument. The sensitivity of the QTOF detection was positively influenced by the application of the VIP-HESI ion source, and overall HRMS instruments provided enhanced selectivity resulting in simplified data evaluation compared to the TQMS. However, all performed experiments revealed strong signal suppression due to matrix components. QTOF results showed more severe effects, enabling a more sensitive detection of mycotoxins in house-dust by applying TQMS detection.

Silicone Wristbands in Exposure Assessment: Analytical Considerations and Comparison with Other Approaches

Humans are exposed to numerous potentially harmful chemicals throughout their lifetime. Although many studies have addressed this issue, the data on chronic exposure is still lacking. Hence, there is a growing interest in methods and tools allowing to longitudinally track personal exposure to multiple chemicals via different routes. Since the seminal work, silicone wristbands (WBs) have been increasingly used to facilitate human exposure assessment, as using WBs as a wearable sampler offers new insights into measuring chemical risks involved in many ambient and occupational scenarios. However, the literature lacks a detailed overview regarding methodologies being used; a comprehensive comparison with other approaches of personal exposure assessment is needed as well. Therefore, the aim of this review is fourfold. First, we summarize hitherto conducted research that employed silicone WBs as personal passive samplers. Second, all pre-analytical and analytical steps used to obtain exposure data are discussed. Third, we compare main characteristics of WBs with key features of selected matrices used in exposure assessment, namely urine, blood, hand wipes, active air sampling, and settled dust. Finally, we discuss future needs of research employing silicone WBs. Our work shows a variety of possibilities, advantages, and caveats associated with employment of silicone WBs as personal passive samplers. Although further research is necessary, silicone WBs have already been proven valuable as a tool for longitudinal assessment of personal exposure.

Human health risks from brominated flame retardants and polycyclic aromatic hydrocarbons in indoor dust

Exposure to dust particles containing toxic compounds is linked to serious health outcomes, including cancer. The purpose of this study was to determine if indoor dust from houses and cars contained harmful levels of brominated flame retardants (polybrominated diphenyl ethers, PBDEs) and polycyclic aromatic hydrocarbons (PAHs), and to assess their potential toxicity to adults and children. In Kuwait, the median concentration of total PBDEs (Ʃ14- PBDEs) was 408.55 μg PBDEs/kg dust in houses and twice as high in cars (838.52 μg PBDEs/kg dust), while total PAHs (Ʃ16-PAHs) were similar in houses (992.81 μg PAHs/kg) and cars (900.42 μg PAHs/kg). The PBDEs and PAHs concentrations in indoor dust were related to house age and square footage, car model year, and natural ventilation. Furthermore, a higher PBDEs concentration was associated with electronic devices that operate continuously, furniture containing foam treated with PBDEs, and cars that are parked outdoors, since PBDEs tend to be volatilized under these conditions. The PAHs concentration in indoor dust increased with smoking and proximity to major roads and industrial facilities, which are major PAHs sources. The hazard quotient and total cancer risk for PBDEs in indoor dust were within safe limits, but indoor dust with higher PAHs concentrations had hazard quotients from 5.51 to 11.23 and total cancer risk of 10^-3 for adults and children. We conclude that exposure to PAHs-contaminated indoor dust from houses and cars where smoking occurs can increase the cancer risk of adults and children.

Exposure of children and mothers to organophosphate esters: Prediction by house dust and silicone wristbands

Ubiquitous human exposure to organophosphorus tri-esters (tri-OPEs) has been reported worldwide. Previous studies investigated the feasibility of using house dust and wristbands to assess human OPE exposure. We hypothesized that these two approaches could differ in relative effectiveness in the characterization of children and adult exposure. In the participants recruited from Guangzhou, South China, urinary levels of major OPE metabolites, including diphenyl phosphate (DPHP) and bis(butoxyethyl) phosphate (BBOEP), were significantly higher in children than their mothers (median 6.6 versus 3.7 ng/mL and 0.11 versus 0.06 ng/mL, respectively). The associations of dust or wristband-associated OPEs with urinary metabolites exhibited chemical-specific patterns, which also differed between children and mothers. Significant and marginally significant associations were determined between dust concentrations of triphenyl phosphate (TPHP), tris(2-butoxyethyl) phosphate (TBOEP), trimethylphenyl phosphate (TMPP), or tris(1-chloro-2-propyl) phosphate (TCIPP) and their metabolites in children urine and between dust tris(1,3-dichloroisopropyl) phosphate (TDCIPP), TPHP or TMPP and urinary metabolites in mothers. By contrast, wristbands exhibited better efficiency of predicting internal exposure to TDCIPP. While both house dust and wristbands exhibited the potential as a convenient approach for assessing long-term OPE exposure, their feasibility requires better investigations via larger-scale studies and standardized sampling protocols.

Characteristics and health risk assessment of heavy metal contamination from dust collected on household HVAC air filters

Heavy metals associated with airborne particulate matter are detrimental to human health, but risk assessment is difficult due to the technical challenges of determining exposure rates. In houses and other buildings, the heating, ventilation and air conditioning (HVAC) system is equipped with an air filter that captures airborne particulate matter from the indoor air that enters the HVAC system. This study used the air filter dust as a proxy for the heavy metal exposure of children and adults, based on a household study in Kuwait. Air filter dust contained from 12.5 ± 5 mg Co/kg dust to 14 453 ± 5046 mg Fe/kg dust. Houses had high levels of Fe, Al, Zn, and Mn and relatively low concentrations of As and Co. Source apportionment revealed that metals in air filter dust were from natural and anthropogenic sources, including vehicular emissions, fossil fuel combustion, and metals-related industries. The total Hazard Index (HI; Σ exposure routes) for heavy metals was >1 for children and adults. Total cancer risks (TCR; Σ exposure routes) were 5.93 × 10^-3 (95% CI: 5.28 × 10^-3- 6.59 × 10^-3) for children and 5.16 × 10^-3 (95% CI: 4.59 × 10^-3 - 5.73 × 10^-3) for adults. Heavy metals, particularly the Cr and Pb concentrations, contribute to the non-carcinogenic and carcinogenic health risks of children and adults in Kuwait households.

Characteristics of indoor dust in an industrial city: Comparison with outdoor dust and atmospheric particulates

There is a considerable connection between indoor and outdoor environments. However, few studies have explored their intrinsic relationship until now. This study conducted morphologic observation, heavy metal monitoring and isotopes analysis in indoor and outdoor dust, as well as the atmospheric particulates in Hefei. Morphologic analysis demonstrated atmospheric particulates were affected by fly ash and construction, road dust mainly came from automobile exhaust and indoor dust particles were interfered by multiple sources, including the secondary reaction of fly ash. Chemical speciation analysis of heavy metals showed the exchange of heavy metals between atmospheric particulates and indoor dust was dominated by non-residual metals, while the exchange between road dust and indoor dust tended to rely on residual metals. The assessment results of heavy metals in particulates showed that indoor carcinogenic risks were greater than outdoor for children, however, for adults, outdoor carcinogenic risks were greater than indoor. Stable isotopes analysis indicated carbon in the dust outside buildings was derived from flying dust, and atmospheric particulates might derive from vehicle exhaust, or partly from natural gas. While sulfur in atmospheric particulates was derived mainly from coal combustion. The release from indoor activities, especially natural gas exhaust emitted from cooking had a certain impact on atmospheric particulates.

Anthropogenic chemicals and their impacts on microbes living in buildings

Humans spend the vast majority of their time indoors where complex interactions occur among indoor anthropogenic chemicals, indoor microbiomes and human occupants. This paper summarizes previous work addressing interactions between anthropogenic chemicals associated with indoor household products and building materials, and microorganisms found within the built environment. Water availability seems to determine the extent to which microbes are impacted by anthropogenic chemicals, since desiccation remains one of the primary stressors regulating microbial viability indoors. Several lines of evidence suggest that both fungi and bacteria are capable of transforming biodegradable ingredients originating from various products used indoors when water is present. Previous research also establishes positive and significant correlations between anthropogenic chemicals that are antimicrobial and antibiotic resistance gene abundance. As researchers move towards understanding complex indoor environments as well as the role of anthropogenic chemicals in shaping microbiomes, in situ activities associated with the viable indoor microbial population merit more attention.

Enhanced Nontarget Screening Algorithm Reveals Highly Abundant Chlorinated Azo Dye Compounds in House Dust

Humans spend 90% of their time indoors, but the majority of indoor pollutants remain unknown. In this study, a nontarget screening algorithm with reduced false discovery rates was developed to screen indoor pollutants using the Toxic Substances Control Act (TSCA) database. First, a putative lock mass algorithm was developed for post-acquisition calibration of Orbitrap mass spectra to sub-ppm mass accuracy. Then, a one-stop screening algorithm was developed by combining MS¹ spectra, isotopic peaks, retention time prediction, and in silico MS² spectra. A sufficient true positive rate (73%) and false discovery rate (5%) were achieved for the screening of halogenated compounds at a score cutoff of 0.28. Above this cutoff, 427 chemicals were detected from 24 house dust samples, including 39 chlorinated compounds. While some identified halogenated compounds (e.g., triclosan) are well known, 18 previously unrecognized chlorinated azo dyes were detected with high abundance as the largest class of chlorinated compounds. Two chlorinated azo dyes were confirmed with authentic standards, but the two most abundant chlorinated azo dyes were missed by the algorithm due to the limited breadth of the TSCA database. These compounds were annotated as chlorinated analogues of Disperse Blue 373 and Disperse Violet 93 using the DIPIC-Frag method. This study revealed the presence of highly abundant chlorinated azo dyes in house dusts, highlighting their potential health risks in the indoor environment.

Health risks associated with the polycyclic aromatic hydrocarbons in indoor dust collected from houses in Kuwait

Polycyclic aromatic hydrocarbons (PAHs) are a byproduct of combustion processes. They are common pollutants in oil-producing countries because fossil fuel processing generates PAHs that associate with dust. Airborne particles containing PAHs are transported into houses during dust storms, which are common in the arid oil-producing countries, and consequently the children and adults in the household are exposed to PAHs in indoor house dust. The goal of this study was to present a systematic survey of PAHs in indoor house dust in Kuwait. The PAHs concentrations and composition of indoor house dust was determined, along with their probable source and the potential carcinogenic risks. Total PAHs concentrations (ƩPAH) were, on average (±standard deviation) 1112 ± 347 μg/kg and ranged from 450 to 2242 μg/kg. Heavier congeners (4-6 ring PAHs) represented 61% of the ƩPAH. Petroleum combustion and traffic emissions were the major source of PAHs, based on the isomeric ratios of PAHs in indoor house dust. The incremental lifetime cancer risks (ILCRs) of exposure to PAHs in indoor house dust was 2.23 × 10^-3 (95% CI: 1.99 × 10^-3 - 2.48 × 10^-3) for children and 2.15 × 10^-3 (95% CI: 1.94 × 10^-3 - 2.37 × 10^-3) for adults, exceeding the US EPA safe limit of 1 × 10^-6. Therefore, exposure to PAHs present in indoor house dust increases the cancer risk for children and adults in Kuwait.

Polychlorinated biphenyls and organochlorines pesticides in indoor dust: An exploration of sources and health exposure risk in a rural area (Kopawa) of Nepal

While contamination of indoor environment with organochlorine compounds (OCs) is well documented worldwide, only a few studies highlighted the problem of indoor pollution in Indian sub-continent, including Nepal. This study insight the contamination level, distribution pattern, and sources of OCs in indoor dust from a rural area of Nepal. Additionally, daily exposure risk through different intake pathways was estimated in order to mark the potential risk of OCs to local residents. Results indicated the predominance of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in dust. Ʃ₂₆OCPs (median 87 ng/g) in dust was about 7-8 times greater than Ʃ₃₀PCBs (median 10.5 ng/g). DDT was the most abundant chemical among Ʃ₂₆OCPs, followed by HCHs and endosulfan, and accounted for 73%, 7%, and 4% of Ʃ₂₆OCPs, respectively. A relatively high level of ƩDDT than other OCPs suggests the existence of DDT source in the Nepalese environment. Among PCB, tetra-CBs were most prevalent, trailed by penta-CBs, hexa-CBs, and hepta-CBs, and comprised 28%, 21%, 17% and 17% of Ʃ₃₀PCBs, respectively. Dioxin like-PCBs (median 3.48 ng/g) was about two times higher than the total indicator-PCB (median 1.63 ng/g). High p,p-DDT/p,p-DDE ratio (median 2.89) suggested fresh application and minimal degradation of DDT in the local environment of Kopawa. While lower α-/γ-HCH ratio (median 0.75) indicated lindane contamination as the primary sources of HCH. Moreover, the low α-/β-endosulfan ratio (median 0.86) specified the fresh use of commercial endosulfan. Among OCPs, only DDT positively related to total organic carbon (TOC) (Rho = 0.55, p < 0.05) but not black carbon (BC), proposing minimal or zero impact of TOC and BC. For PCBs, PCB-126 was moderately and negatively correlated with TOC (Rho = -0.49, p < 0.05), but not BC. The daily risk exposure (DRE) assessment showed that children are more vulnerable to OCs than the adult. The DRE of OCs in this study were 2-4 order of magnitude lower than their corresponding reference dose (RfD), proposing insignificant risk.

Objective ranges of soil-to-dust transfer coefficients for lead-impacted sites

Residential yard soil and indoor dust datasets from eight communities near historical mining, smelting, and refining operations were used to quantify soil track-in, an important factor in evaluating indoor exposures to soil metals and to set residential soil cleanup levels. Regression analyses were used to derive slopes that represent mass soil-to-dust transfer coefficients or MSDs. Lead concentration data were available for all datasets. Arsenic data were available for six of the eight datasets. Cadmium and zinc data were available for one dataset, allowing limited comparison of MSDs for lead with other metals. Covariates that could indicate potential indoor sources of metals, such as house age and indoor heating source, were examined by multivariate regression analysis when available (three datasets). Covariates that could affect soil track-in, such as the amount of bare soil in the yard or having pets, were examined by stratified linear regression analysis when available (two datasets). Most of the R-squared values for lead, cadmium and zinc indicate a good to moderate fit (≥0.25), but for arsenic most indicate a poor fit (<0.25). Significant MSDs for models with a good to moderate fit range from 0.14 to 0.47 for lead, and 0.12 to 0.43 for the other metals (arsenic, cadmium, and zinc). The treatment of outliers was a significant methodological factor affecting the slope of the regressions. Substantial variability is expected among soils at residences due to both physical characteristics of each property and the ways in which residents interact with their home. Survey data providing information on various factors affecting soil track-in help to refine MSD estimates. For three of the datasets, covariate data were available that improved model fit by multivariate or stratified regression analysis for lead. When multivariate or stratified regression analyses were performed, the estimated MSD varied as little as <1% to as great as 200% depending on the dataset, but all estimates were below 0.4. Notably, the MSDs were lowest for the three datasets with the highest soil lead concentrations, i.e., those with average soil lead concentrations greater than 300 mg/kg after outlier removal. For five of the six datasets that had both arsenic and lead sampled, arsenic MSDs were much less than the lead MSDs; however, only two of the sites' arsenic models had significant MSDs and adequate fit. Cadmium and zinc were only included in one dataset, limiting our ability to draw any conclusions from comparison to those MSDs. The results of our study are consistent with prior studies suggesting that MSDs for metals without internal sources are 0.3-0.4, and application of MSDs in that range will provide more reliable exposure estimates than the 0.7 default value used by the United States Environmental Protection Agency in the Integrated Exposure Uptake Biokinetic (IEUBK) Model.

Levels and distribution of polybrominated diphenyl ethers in humans and environmental compartments: a comprehensive review of the last five years of research

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants (BFRs), present in the environment, animals, and humans. Their levels, distribution, and human exposure have been studied extensively, and over the last decade, various legal measures have been taken to prohibit or minimize their production and use due to the increasing amount of evidence of their harmful effects on human and animal health.Our aim here was to make a comprehensive and up-to-date review of the levels and distribution of PBDEs in the aquatic environment, air, and soil, in indoor dust, and in humans. To fulfill this, we searched through Web of Science for literature data reported in the last five years (2015-2019) on levels of at least six key PBDE congeners in abovementioned matrices. According to our summarized data, significant PBDE mass concentrations/fractions are still being detected in various sample types across the world, which implies that PBDE contamination is an ongoing problem. Secondary sources of PBDEs like contaminated soils and landfills, especially those with electronic and electrical waste (e-waste), represent a particular risk to the future and therefore require a special attention of scientists.

Human exposure and risk associated with trace element concentrations in indoor dust from Australian homes

This study examines residential indoor dust from 224 homes in Sydney, Australia for trace element concentrations measured using portable X-ray Fluorescence (pXRF) and their potential risk of harm. Samples were collected as part of a citizen science program involving public participation via collection and submission of vacuum dust samples for analysis of their As, Cr, Cu, Mn, Ni, Pb and Zn concentrations. The upper 95% confidence level of the mean values for 224 samples (sieved to <250 μm) were 20.2 mg/kg As, 99.8 mg/kg Cr, 298 mg/kg Cu, 247 mg/kg Mn, 56.7 mg/kg Ni, 364 mg/kg Pb and 2437 mg/kg Zn. The spatial patterns and variations of the metals indicate high homogeneity across Sydney, but with noticeably higher Pb values in the older areas of the city. Potential hazard levels were assessed using United States Environmental Protection Agency's (US EPA) carcinogenic, non-carcinogenic and Integrated Exposure Uptake Biokinetic (IEUBK) model human health risk assessment tools for children and adults. US EPA hazard indexes (HI) for Cr and Pb were higher than the safe level of 1.0 for children. HI > 1 suggests potential non-carcinogenic health effects. Carcinogenic risks were estimated for As, Cr and Pb whose carcinogenic slope factors (CSF) were available. Only the risk factor for Cr exceeded the US EPA's carcinogenic threshold (1 × 10^-4) for children. Children aged 1-2 years had the highest predicted mean child blood lead (PbB) of 4.6 μg/dL, with 19.2% potentially having PbB exceeding 5 μg/dL and 5.80% exceeding 10 μg/dL. The Cr and Pb levels measured in indoor dust therefore pose potentially significant adverse health risks to children.

Isopropylated and tert-butylated triarylphosphate isomers in house dust from South China and Midwestern United States

In the present study we determined the concentrations and compositions of a suite of isopropylated and tert-butylated triarylphosphate ester (ITP and TBPP) isomers in house dust from the city of Guangzhou located in South China and the city of Carbondale in Midwestern United States. These two groups of organophosphate esters (OPE) are structurally analogous to triphenyl phosphate (TPHP), but have rarely been investigated for environmental occurrences and human exposure risks. The majority of target ITP and TBPP isomers were 100% detected in house dust from the two locations. Median concentrations of ΣITPs (including all ITP isomers) and ΣTBPPs (including all TBPP isomers) were 63.4 ng/g (range: 16.0-500 ng/g) and 35.4 ng/g (8.1-198 ng/g) in South China house dust, respectively, compared with 476 ng/g (140-1610 ng/g) for ΣITPs and 81.3 ng/g (35.2-800 ng/g) for ΣTBPPs in Midwestern U.S. dust. The profiles of ITP or TBPP isomers were similar between the two locations and were dominated by 2-isopropylphenyl diphenyl phosphate (2IPPDPP) and 4-tert-butylphenyl diphenyl phosphate (4tBPDPP), respectively. Although the levels of ΣITPs and ΣTBPPs were generally one order of magnitude lower than those of TPHP in the same dust samples, the broad occurrences of most of these isomers in house dust from the two locations likely suggest their wide applications in household consumer products. Estimated intakes of ΣITPs and ΣTBPPs via dust ingestion were generally three orders of magnitude lower than the reference dose proposed for TPHP. However, these emerging OPE chemicals merit continuous environmental surveillance, given their possible applications as specific commercial mixtures or as components/impurities in other flame retardant/plasticizer mixtures.

Brominated and organophosphorus flame retardants in South African indoor dust and cat hair

Flame retardants (FRs), such as brominated flame retardants (BFRs) and organophosphorus flame retardants (OPFRs), are diverse groups of compounds used in various products related to the indoor environment. In this study concentrations of eight polybrominated diphenyl ethers (PBDEs), two alternative BFRs and ten OPFRs were determined in indoor dust (n = 20) and pet cat hair (n = 11) from South Africa. The OPFRs were the major FRs, contributing to more than 97% of the total FR concentration. The median Ʃ₁₀OPFRs concentrations were 44,800 ng/g in freshly collected dust (F-dust), 19,800 ng/g in the dust collected from vacuum cleaner bags (V-dust), and 865 ng/g in cat hair (C-hair). Tris(1-chloro-2-propyl) phosphate (TCIPP) was the dominant OPFR in the dust samples with median concentrations of 7,010 ng/g in F-dust and 3,590 ng/g in V-dust. Tris(2-butoxyethyl) phosphate (TBOEP) was the dominant OPFR in C-hair, with a median concentration of 387 ng/g. The concentrations of Ʃ₈PBDEs were higher in F-dust than in V-dust. BDE209 was the dominant BFR in all three matrices. Bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (BEH-TEBP) and 2-ethylhexyl-2,3,4,5- tetrabromobenzoate (EH-TBB) showed notable contributions to the BFR profile in cat hair. A worst-case dust exposure estimation was performed for all analytes. The estimated TCIPP daily intake through dust ingestion was up to 1,240 ng/kg bw for toddlers. The results indicate that OPFRs are ubiquitous in South African indoor environment. Indoor dust is a major source of human exposure to environmental contaminants. This can for example occur through hand-to-mouth contact of toddlers, and is an important route of exposure to currently used FRs accumulated on dust particles. The presence of FRs, in particular high concentrations of OPFRs, suggests that children and indoor pet cats may have greater exposure to FRs than adults.

PAH concentrations and exposure assessment from house dust retained in air-conditioning filters collected from Greater Doha, Qatar

Polycyclic aromatic hydrocarbons (PAHs) bound in dust retained in air-conditioning unit filters from 13 households in Greater Doha, Qatar, were quantified using GC-MS spectrometry. The median concentrations of ∑₁₆PAH and ∑₇PAH were 218.0 ng g^-1 (± 125.3) and 112.1 ng g^-1 (± 60.2) dry weight, respectively. Results show that except one sample, three- and four-benzene-ring PAHs were dominant in all dust samples. Phenanthrene, anthracene, pyrene, benzene(a)anthracene, and chrysene were dominant in 12 samples with maximum concentrations of 69.7 ng g^-1 (± 24.0), 92.9 ng g^-1 (± 28.1), 60.4 ng g^-1 (± 14.7), 38.6 ng g^-1 (± 7.3), and 14.7 ng g^-1 (± 3.5), respectively. Benzo(k)fluoranthene has the most abundance of the quantified PAHs in the dust samples accounting for 19% of the total PAHs. Although Kriging interpolation shows a spatial variation of PAHs from north to south of Greater Doha, the mean concentrations in both directions were statically insignificant. Five samples displayed levels of benzo(a)pyrene (BaP) with maximum and median concentrations at 110.8 ng g^-1 and 49.9 (± 28.4) dry weight, respectively. Benzo(a)pyrene equivalent approach [Formula: see text] was applied to assess carcinogenic exposure, and the resulting values (1.3-116.4 ng g^-1) indicate that the levels observed were below the values reported for other countries within the region. Estimated daily ingestion (EDI) rates of PAHs retained in ACU filters were assessed for five age-groups < 1, 1-2, 3-6, 11-16, and > 19 years and were 0.39 (± 0.1), 0.33 (± 0.1), 0.20 (± 0.02), 0.07 (± 0.02), and 0.05 (± 0.01) ng kg^-1/day, respectively. Source apportionment estimate indicates PAHs bound in dust retained in ACU filters are originated from pyrogenic sources.

Examining the role of total organic carbon and black carbon in the fate of legacy persistent organic pollutants (POPs) in indoor dust from Nepal: Implication on human health

Despite the fact that the consumption and import of legacy persistent organic pollutants (POPs) have been stopped in Nepal since 2001, they are still of worry for human prosperity and the environment because of their persistence behavior and constant release from sources that are presently being used. The essential objective of this study was to assess the concentration and spatial distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in residential dust from Nepal keeping in mind the end goal to evaluate the importance of total organic carbon (TOC) and black carbon (BC) in the fate of legacy POPs. Additionally, health risk exposure via dust ingestion and dermal absorption was estimated to evaluate the significance of dust media for human exposure. Results demonstrated that ∑OCPs in dust was 37 times greater than ∑PCBs. DDT was mostly dominated in the dust, and contributed 90% of the ∑OCPs, while hexa-CBs predominated among PCBs and represented 34% of ∑PCBs. Birgunj and Biratnagar had a relatively higher level of ∑OCPs and ∑PCBs than those of Kathmandu and Pokhara. TOC and BC showed a poor connection with OCPs, recommending little or no role. However, PCB in the dust, especially low congeners was strongly linked with TOC but not BC indicating the significant role of TOC. The daily risk exposure estimation indicated dermal absorption through dust as the principal means of OCPs/PCBs intake to both adult and children population. These estimated exposures were 2-4 orders of magnitude inferior to their corresponding reference dose showing insignificant risk.

Indoor phthalate concentrations in residences in Shihezi, China: implications for preschool children's exposure and risk assessment

Despite the risks associated with phthalate exposure, there are few studies emphasizing preschool children's exposure to phthalates in residences in Northwest China. In this study, seven phthalates from indoor dust samples were measured in 50 residences in Shihezi, China. Preschool children's exposure doses via non-dietary intake were calculated by Monte Carlo simulation. Risk assessment was conducted by comparing the simulated exposure dose with benchmarks for reproductive toxicity and cancer specified in Proposition 65 of California. The detection frequencies for all selected phthalates were more than 75%, with the exception of benzyl butyl phthalate (BBP) and di-n-octyl phthalate (DNOP). Bis(2-ethylhexyl) phthalate (DEHP) was the most principal compound in the dust samples (median = 455 μg/g and 462 μg/g in the bedroom and living room, respectively). The simulation displayed that the median DBP daily intake was 1.5-1.9 μg/day/kg for preschool children in Shihezi, which was considered a high level compared with similar studies around the world. The risk assessment indicated that almost all preschool children face potential reproductive risk due to dibutyl phthalate (DBP) exposure, with medians of hazard index (HI) from 9.6 to 12.4 for all age groups. Therefore, from a children's health perspective, attention should be paid to reducing indoor phthalate pollution and exposure in this area.

Human Indoor Exposome of Chemicals in Dust and Risk Prioritization Using EPA's ToxCast Database

Humans spend most of their time indoors and thus have long-term exposure to chemicals. Dust is a sink for most indoor chemicals, and its ingestion is an important pathway for chemical uptake. Therefore, the chemical atlas from dust is an ideal environmental sample to investigate the indoor exposome and associated risk. In this study, we aimed to establish an indoor exposome database through comprehensive data mining on the occurrence of identified compounds in dust, and we prioritize chemicals of health concern. Through an extensive literature review (2849 articles), 355 chemicals and their concentrations were documented and analyzed for human exposure. Together with 81 compounds without concentration and 75 volatile organic compounds, we have established an indoor exposome database with 511 chemicals. Sixteen toxicological end points were selected for toxicity prioritization. Toxic equivalency factor (TEF)-based toxicity, calculated from EPA's ToxCast database, revealed a comprehensive atlas of the chemicals that had a primary contribution. Many of the prioritized compounds are currently neglected or are not actively studied. Overall, this investigation provides one of the most comprehensive analyses on chemical occurrence in indoor dust and prioritizes their chemical toxicity. Our findings can be used as a database for future exposome studies of the indoor environment and provide guidance for indoor risk assessments.

Co-Existence of Organophosphate Di- and Tri-Esters in House Dust from South China and Midwestern United States: Implications for Human Exposure

Despite numerous studies on the contamination of organophosphate triesters (tri-OPEs) in indoor environments, organophosphate diesters (di-OPEs) have rarely been investigated. The present study aimed to investigate whether di-OPEs coexist with tri-OPEs in house dust collected from Guangzhou ( n = 30), South China and the city of Carbondale ( n = 17) located in the Midwestern United States (U.S.). Median concentrations of bis(2-butoxyethyl) phosphate (BBOEP), bis(1-chloro-2-propyl) phosphate (BCIPP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis(2-ethylhexyl) phosphate (BEHP), bis(2-methylphenyl phosphate) (BMPP), and diphenyl phosphate (DPHP) were determined to be 15.9, < LOQ, 33.6, 654, 9.5, and 605 ng/g in South China house dust, and 1580, 90.6, 234, 867, 4.0, and 6500 ng/g in Midwestern U.S. dust, respectively. The total concentrations of di-OPEs (referred to Σ_diOPEs) constituted an average of 22.9% and 21.3% of the total concentrations of tri-OPEs in dust from these two locations, respectively. Median concentration ratios of DPHP and BEHP to their respective tri-OPEs (i.e., TPHP and TEHP) were determined to be 1.1 and 1.0 in South China dust and 3.7 and 1.4 in Midwestern U.S. dust, respectively, indicating possible commercial applications for these two di-OPEs. Correlative analyses reveal chemical- and region-specific relationships between di-OPEs and their respective tri-OPEs, suggesting that the relative importance of different sources (e.g., direct commercial use, impurity in tri-OPE formulas, and tri-OPE degradation) could vary for different di-OPEs. Our findings demonstrate wide occurrences of di-OPEs in an indoor environment from the studied locations and raise concerns on human exposure to dust associated di-OPEs. Future studies are needed to explore more possible di-OPEs in indoor environments and elucidate their sources, human exposure pathways, and toxicokinetics.

Pyrethroid levels in toddlers' breathing zone following a simulated indoor pesticide spray

Application of pyrethroid insecticides in residential settings may result in children's exposures to these chemicals and possible adverse health effects. Household dust is a recognized reservoir for pyrethroids and a potential medium for multi-route pyrethroid exposure. Young children move and play in a manner that resuspends dust, and since their breathing zone is close to the floor, they will have higher inhalation exposure to pesticide-laden dust than other age groups. Directly measuring a toddler's exposure to household dust presents many logistic challenges. We simulated the dust resuspension induced by a toddler using a robot, which also served as a platform to collect air samples at the toddler's breathing zone height. We performed simulated pyrethroid residential spray and dust resuspension experiments on vinyl and carpeted floors. The mean pyrethroid airborne concentrations in the stationary and mobile samples were 0.065 μg/m³ and 0.143 μg/m³ for the vinyl floor with 1 g/m² dust loading, and 0.034 μg/m³ and 0.061 μg/m³ for the carpeted floor with 10 g/m² dust loading, respectively. Pyrethroids concentrations in the settled dust samples were significantly lower than that measured in the stationary and mobile samples in the carpeted floor experiments. Thus, the use of stationary samples and settled dust samples may underestimate a toddler's personal inhalation exposure to pyrethroids in residential houses.

Legacy and alternative flame retardants in house dust and hand wipes from South China

The present study investigated the occurrence of legacy and alternative halogenated flame retardants (FRs) in house dust (n = 51) from Guangzhou, South China and hand wipes collected from adults (n = 51) and children (n = 31). In addition to polybrominated diphenyl ether (PBDE) congeners (particularly BDE-209), several alternative FRs were also detected in >60% of dust samples, including decabromodiphenylethane (DBDPE; median: 4600 ng/g), bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (BEH-TEBP; 43.9 ng/g), 1,2-bis(2,4,6-tribormophenoxy)ethane (BTBPE; 9.2 ng/g), pentabromotoluene (PBT; 10.1 ng/g), and syn- and anti-dechlorane plus (DPs, 24.5 ng/g). BDE-47, BDE-209, DBDPE, BEH-TEBP, and DPs were also frequently detected on hand wipes from children (median mass: 0.1-1.1 ng) and adults (0.1-1.2 ng). Linear regression models suggest that dust concentrations of BDE-47 and DPs had significant or marginally significant associations with their masses on children's (10^β = 2.82; 95% CI: 1.20, 6.64 and 10^β = 5.57, 95% CI: 1.85, 16.75, respectively) and adults' hands (10^β = 4.46; 95% CI: 0.92, 21.58 and 10^β = 5.11; 95% CI: 1.74, 14.96, respectively), whereas no association was observed for any other FRs. Most of the investigated demographic, environmental, or behavioral factors did not significantly influence the levels of halogenated FRs on human hands. Estimation of human exposure risks via hand-to-mouth contact and dust ingestion indicates that children are subjected to elevated exposure than adults, and the relative importance of the two pathways is chemical-specific.

Measurement of legacy and emerging flame retardants in indoor dust from a rural village (Kopawa) in Nepal: Implication for source apportionment and health risk assessment

Under the Stockholm Convention, signatory countries are obliged to direct source inventories, find current sources, and provide ecological monitoring evidence to guarantee that the encompassing levels of persistent organic pollutants (POPs) are declining. However, such monitoring of different types of POPs are to a great degree constrained in most developing countries including Nepal and are primarily confined to suspected source area/ densely populated regions. In this study, 9 polybrominated diphenyl ethers (PBDEs), 2 dechlorane plus (DPs), 6 novel brominated flame retardants (NBFRs) and 8 organophosphate ester flame retardants (OPFRs) were investigated in indoor dust from a rural area (Kopawa) in Nepal in order to evaluate their occurrence/level, profile, spatial distribution and their sources. Additionally, health risk exposure was estimated to anticipate the possible health risk to the local population. The results showed that OPFRs was the most abundant FR measured in the dust. The concentration of ∑₈OPFRs was about 2, 3 and 4 orders of magnitude higher than the ∑₆NBFRs, ∑₉PBDEs, and ∑₂DPs, respectively. Tris (methylphenyl) phosphate (TMPP) and Tris (2-ethylhexyl) phosphate (TEHP) were the most abundant OPFRs analyzed in the dust; while decabromodiphenyl ethane (DBDPE) exceeded among NBFRs. Likewise, 2,2',3,3',4,4',5,5',6,6'-decabromodiphenylether (BDE-209) was the most identified chemical among PBDEs. The total organic carbon (TOC) content in dust was significantly and positively connected with octa-BDEs (Rho = 0.615, p < 0.01), BTBPE (Rho = 0.733, p < 0.01), TPHP (Rho = 0.621, p < 0.01), TEHP (Rho = 0.560, p < 0.01) and TMPPs (Rho = 0.550, p < 0.01), while black carbon (BC) was either weakly related or not related, suggesting little or no impact of BC in the distribution of FRs. Principal component analysis indicated the contribution from commercial penta-, octa- and deca-BDEs formulation, the adhesive substance, food packaging and paints, and degradation of BDE-209 as the essential sources of FRs. Health risk exposure estimates showed that dermal absorption via dust as the primary route of FRs intake. The estimated daily exposure of PBDEs, NBFRs and OPFRs were 2-10 orders of magnitude lower than their corresponding reference dose (RfD), suggesting insignificant risk. However, other routes such as inhalation and dietary intake might still be significant in the case of Kopawa which should be tested in future.

Novel and Traditional Organophosphate Esters in House Dust from South China: Association with Hand Wipes and Exposure Estimation

The present study investigated the occurrence of 20 organophosphate esters (OPEs) in house dust from 51 South China homes and the risks of human exposure to OPEs via two pathways: dust ingestion and hand-to-mouth contact. In addition to several traditional OPEs, five out of six novel OPEs, including bisphenol A bis(deiphenyl phosphate) (BPA-BDPP), t-butylphenyl diphenyl phosphate (BPDPP), cresyl diphenyl phosphate (CDP), isodecyl diphenyl phosphate (IDDPP), and resorcinol-bis(diphenyl)phosphate (RDP), were frequently detected in house dust (median concentration: 59.7-531 ng/g). Eight of the 20 target OPEs were frequently detected in hand wipes collected from adults and children ( n = 51 and 31, respectively), which in combination (referred to as Σ₈OPEs) had a median mass of 76.9 and 58.9 ng, respectively. Increasing dust concentrations of Σ₈OPEs or three individual substances among these eight OPEs, including tris(1-chloro-2-propyl) phosphate (TCIPP), tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), and triphenyl phosphate (TPHP), were strongly associated with their levels in children's hand wipes ( p < 0.05 in all cases). By contrast, in adults' hand wipes only TPHP exhibited a marginally significant association with dust concentrations ( p = 0.04). Levels of Σ₈OPEs in hand wipes from children, but not adults, were inversely influenced by hand washing frequency ( p = 0.002), while indoor temperature was inversely associated with hand wipe levels of Σ₈OPEs from both children and adults ( p = 0.01 and 0.002, respectively). Exposure estimation suggests that hand-to-mouth contact represents another important pathway in addition to dust ingestion and that children are subjected to higher OPE exposure than adults.

Concentrations of polychlorinated biphenyls in soil and indoor dust associated with electricity generation facilities in Lagos, Nigeria

Concentrations of 7 indicator polychlorinated biphenyls (PCBs) were measured in dust and soil samples from 12 power stations collected over the two major seasons of the Nigerian climate. Median ƩPCB₇ concentrations in soil ranged from 2 ng/g for power station A to 220 ng/g for power station I; while those in dust ranged from 21 ng/g for power station L to 2200 ng/g for power station I. For individual congeners, median PCB concentrations ranged from 3.8 ng/g for PCB 101 to 52 ng/g for PCB 180 in dust, and <0.07 ng/g for PCB 28 to 5.9 ng/g for PCB 153 in soil. The type of power station activity exerted a significant influence on concentrations of ΣPCB₇ in dust and soil (generation > transmission > distribution). Congener patterns in dust and soil samples were compared using principal component analysis (PCA) with those in transformer oil samples from 3 of the power stations studied and with common PCB mixtures (Aroclors). This revealed congener patterns in soil were more closely related to that in the transformer oil than dust. Congener patterns in most samples were similar to Aroclor 1260. Concentrations of PCBs in soil samples close to the transformers significantly exceeded those in soil sampled further away.

Toward Capturing the Exposome: Exposure Biomarker Variability and Coexposure Patterns in the Shared Environment

Many factors affect the variation in the exposome. We examined the influence of shared household and partner's sex in relation to the variation in 128 endocrine disrupting chemical (EDC) exposures among couples. In a cohort comprising of 501 couples trying for pregnancy, we measured 128 (13 chemical classes) persistent and nonpersistent EDCs and estimated 1) sex-specific differences; 2) variance explained by shared household; and 3) Spearman's rank correlation coefficients ( r_s) for females, males, and couples' exposures. Sex was correlated with 8 EDCs including per- and polyfluoroalkyl substances (PFASs) ( p < 0.05). Shared household explained 43% and 41% of the total variance for PFASs and blood metals, respectively, but less than 20% for the remaining 11 EDC classes. Coexposure patterns of the exposome were similar between females and males, with within-class r_s higher for persistent than for nonpersistent chemicals. Median r_ss of polybrominated compounds and urine metalloids were 0.45 and 0.09, respectively, for females (0.41 and 0.08 for males; 0.21 and 0.04 for couples). Our findings suggest that individual, rather than shared environment, could be a major factor influencing the covariation of the exposome. Understanding the correlations of exposures has important analytical and sampling implications for exposomics research.

Polychlorobiphenyl levels in the serum of cats from residential flats in Italy: Role of the indoor environment

The domestic cat (Felis catus) was used as a sentinel of exposure to polychlorobiphenyls (PCBs) in indoor urban environments y. Sera from 120 cats were pooled to form 30 different groups selected by age (<2 years; > 2 ≤ 8 years; > 8 years), sex, municipality (Bologna and Turin) and environment (indoor vs. outdoor). Test portions of 1 mL were analyzed by means of gas chromatography coupled to high-resolution mass spectrometry (GC-HRMS) for six selected indicators non-dioxin-like PCBs (∑6 PCBs: congeners #28, #52, #101, #132, #153 and #180) and the results were computed in the upper-bound mode. The internal dose of PCBs attributable to the cats' alimentary lipid intake ranged from 32.4 to 1,446 ng/g (P50 165; mean 258). The Wilcoxon test revealed significantly lower PCB burden in "outdoor" groups than in "indoor" groups. Age correlated well with the heptachlorinated and most bio-accumulative congener, PCB #180, and slightly with hexachlorinated PCBs #138 and #153. Contamination attributable to house dust collected in 15 living-rooms ranged from 10.0 to 279 ng/g dry weight (P50 97.4; mean 94.4). Exposure estimates indicated a 0.6-16 ng/kg bw range of daily ∑6 PCB intake from a default value of 200 mg/cat of dust ingestion. The intake of PCBs due to dust ingestion fell within the same order of magnitude as that computed from a 60 g daily intake of commercial dry pet foods, while inhalation accounted for 0.21-8.2 ng/kg bw/day, on setting the nominal ∑6 PCB contamination in outdoor and indoor air at 0.37 and 15 ng/m³, respectively. Italian indoor cats could be exposed to higher levels of ∑6 PCBs than the Reference Dose (RfD) of 10 ng/kg/bw/day; this supports the World Health Organization's statement that the quality of the indoor environment is a major determinant of health.

Organophosphate flame retardants in dust collected from United States fire stations

Firefighters are exposed to chemicals during fire events and we previously demonstrated that fire station dust has high levels of polybrominated diphenyl ethers (PBDEs). In conducting the Fire Station Dust Study, we sought to further characterize the chemicals to which firefighters could be exposed - measuring the emerging class of phosphorous-containing flame retardants (PFRs) in fire stations, for the first time, as well as PBDEs. Dust samples from 26 fire stations in five states were collected from vacuum-cleaner bags and analyzed for PFRs and PBDEs. PFR concentrations were found to be on the same order of magnitude as PBDE concentrations (maximum PFR: 218,000ng/g; maximum PBDE: 351,000ng/g). Median concentrations of tri-n-butyl phosphate (TNBP), tris (2-chloroisopropyl) phosphate (TCIPP), and tris(1,3-dichloroisopropyl)phosphate (TDCIPP) in dust from fire stations were higher than those previously reported in homes and other occupational settings around the world. Total PFR levels did not vary significantly among states. Levels of TDCIPP were higher in stations where vacuum cleaners were used to clean surfaces other than the floor. PBDE levels were comparable to those found in our previous study of 20 California fire stations and much higher than levels in California residences. PFR and PBDE levels in fire station dust are higher than in other occupational and residential settings, underscoring the need to identify and control sources of this contamination.

Emerging and legacy flame retardants in indoor dust from East China

To understand human exposure to dust-associated flame retardants in the biggest metropolitan area (city of Shanghai) of East China, our study determined a suite of legacy and emerging flame retardants in dust from dwellings, cars, and university computer labs. The results exhibited a consistent dominance of organophosphate flame retardants (OPFRs) over polybrominated diphenyl ethers (PBDEs) and other alternative flame retardants (AFRs) regardless of microenvironments. In addition to OPFRs, some alternative flame retardants, such as decabromodiphenyl ethane (DBDPE), 2-ethylhexyltetrabromobenzoate (EH-TBB), bis(2-ethylhexyl)-3,4,5,6-tetrabromobenzoate (BEH-TEBP), and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), were also frequently detected. Among them, DBDPE exhibited concentrations comparable to those of PBDEs. Comparison with international studies indicated that concentrations of ∑PBDEs (0.2-12.3 μg/g dry weight or dw) and ∑OPFRs (3.8-165.5 μg/g dw) from Shanghai dwellings (bedroom and living room) were generally in the middle of concentration ranges reported worldwide, whereas elevated DBDPE concentrations (0.1-9.5 μg/g dw) was observed compared with most other countries or regions. OPFR compositions in house dust from this study also differed from those from many other countries. This suggested inter-regional differences in market demands on the quantities and types of flame retardants. Human intake estimation suggested elevated exposure for toddlers when compared with adults, although the daily intake estimations of individual flame retardants were generally 2-4 orders of magnitude lower than the reference doses. The findings from this preliminary study developed a baseline for future evaluation of the sources and fate of emerging flame retardants and related human exposure risks in East China.

Phthalate and non-phthalate plasticizers in indoor dust from childcare facilities, salons, and homes across the USA

The quality of indoor environment has received considerable attention owing to the declining outdoor human activities and the associated public health issues. The prolonged exposure of children in childcare facilities or the occupational exposure of adults to indoor environmental triggers can be a culprit of the pathophysiology of several commonly observed idiopathic syndromes. In this study, concentrations of potentially toxic plasticizers (phthalates as well as non-phthalates) were investigated in 28 dust samples collected from three different indoor environments across the USA. The mean concentrations of non-phthalate plasticizers [acetyl tri-n-butyl citrate (ATBC), di-(2-ethylhexyl) adipate (DEHA), and di-isobutyl adipate (DIBA)] were found at 0.51-880 μg/g for the first time in indoor dust samples from childcare facilities, homes, and salons across the USA. The observed concentrations of these replacement non-phthalate plasticizer were as high as di-(2-ethylhexyl) phthalate, the most frequently detected phthalate plasticizer at highest concentration worldwide, in most of indoor dust samples. The estimated daily intakes of total phthalates (n = 7) by children and toddlers through indoor dust in childcare facilities were 1.6 times higher than the non-phthalate plasticizers (n = 3), whereas estimated daily intake of total non-phthalates for all age groups at homes were 1.9 times higher than the phthalate plasticizers. This study reveals, for the first time, a more elevated (∼3 folds) occupational intake of phthalate and non-phthalate plasticizers through the indoor dust at salons (214 and 285 ng/kg-bw/day, respectively) than at homes in the USA.

Organophosphate Flame Retardants in House Dust from South China and Related Human Exposure Risks

House dust associated with organic pollutants is not only a potential source of pollutants to the outdoor environment, but also a source to human exposure. The present study investigated the occurrence and concentrations of organophosphate flame retardants (OPFRs) in house dust collected from South China dwellings (n = 20). The results revealed a universal presence of most target OPFRs in house dust, with concentrations of ΣOPFRs ranging from 2.06 to 19.95 μg/g. The median concentration of ΣOPFR (9.20 μg/g) was one order of magnitude greater than that of polybrominated diphenyl ethers (0.80 μg/g). The composition of OPFR chemicals in house dust was dominated by chlorinated OPFRs, such as tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and tris(1-chloro-2-propyl) phosphate (TCPP). This compositional pattern was different from what has been reported in indoor dust from many other countries, where tris(2-butoxyethyl) phosphate (TBEP) was generally dominant. The daily intake of OPFRs by adults was estimated to be 1.6 and 4.2 ng/kg body weight/day under average and high exposure scenarios, respectively, and 31.7 and 127 ng/kg body weight/day for toddlers.

Impact of dust exposure on mixed bacterial cultures and during eukaryotic cell co-culture infections

On a daily basis, humans, and their colonizing microbiome, are exposed to both indoor and outdoor dust, containing both deleterious organic and inorganic contaminants, through dermal contact, inhalation, and ingestion. Recent studies evaluating the dust exposure responses of opportunistic pathogens, such as Escherichia coli and Pseudomonas aeruginosa, revealed significant increases in biofilm formation following dust exposure. In this study, the effects of dust exposure on mixed bacterial cultures as well as HT-29 co-cultures were evaluated. As it was observed in pure, single bacterial cultures earlier, neither indoor nor outdoor dust exposure (at concentrations of 100 μg/mL) influenced the growth of mixed bacterial liquid cultures. However, when in paired mixed cultures, dust exposure increased sensitivity to oxidative stress and significantly enhanced biofilm formation (outdoor dust). More specifically, mixed cultures (E. coli-Klebsiella pneumoniae, K. pneumoniae-P. aeruginosa, and E. coli-P. aeruginosa) exhibited increased sensitivity to 20 and 50 mM of H₂O₂ in comparison to their pure, single bacterial culture counterparts and significantly enhanced biofilm production for each mixed culture. Finally, bacterial proliferation during a eukaryotic gut cell (HT29) co-culture was significantly more robust for both K. pneumoniae and P. aeruginosa when exposed to both house and road dust; however, E. coli only experienced significantly enhanced proliferation, in HT29 co-culture, when exposed to road dust. Taken together, our findings demonstrate that bacteria respond to dust exposure differently when in the presence of multiple bacterial species or when in the presence of human gut epithelial cells, than when grown in isolation.

Organophosphate flame retardants in household dust before and after introduction of new furniture

Flame retardant compounds originating from household items collect in household dust, a reasonable proxy for human exposure. Contributions of specific items or behaviors to dust are difficult to separate. This study examined standardized college housing before and after the introduction of new, flame retardant couches in order to explore any effect that changing upholstered furniture may have on flame retardant concentrations in dust. Two contradictory hypotheses were posited: (1) that new furniture might increase flame retardant releases immediately after introduction due to initial off-gassing of new materials or (2) that older furniture would release more flame retardants due to mechanical breakdown of polyurethane foam. This study was designed to determine which of these processes dominated. Prior to the introduction of new furniture, TDCIPP was detected in 12/20 samples at a median concentration of 22 μg/g and TCEP was detected in 1/20 samples at a concentration of 16 μg/g. TDCIPP and TCEP were not detected in any samples (N = 29) after the introduction of new couches. TPHP was detected both before (in 11/20 samples) and after (in 5/29 samples) introduction of new couches; the median concentrations before and after were 63 ± 49 and 16 ± 11 μg/g (standard deviation shown). Introduced couches contained TDCIPP (and not TPHP) at ∼1.25% (w/w). These data support the second hypothesis and indicate that removal of older furniture decreases TDCIPP and TCEP concentrations in dust and may potentially reduce total flame retardant concentrations in dust, at least immediately after introduction of the new furniture.

Temporal Changes of PBDE Levels in California House Cats and a Link to Cat Hyperthyroidism

In this study, we measured serum PBDE levels in California (CA) house cats during two time periods: 2008-2010 and 2012-2013 to assess the impacts of the decline in use of these materials after the bans. The median ∑19PBDE level in CA household cats (age ≥10 yr) was 3479 ng/g lipid in 2008-2010 (1st time period, n = 21) and 1518 ng/g lipid in 2012-2013 (2nd time period, n = 22), about 2 times lower than in the first time period (p = 0.006). In contrast, PCB and OCP levels showed no statistically significant changes. With better matched group size and age (HT = 11 vs non-HT = 11, age ≥10 yr) in the second time period, we found that ∑19PBDE level (mean ± SE ng/g lipid) was significantly higher in the HT group (3906 ± 1442) than those in the non-HT group (1125 ± 244) (p = 0.0030). Higher levels of PCBs and OCPs were also found in HT group. Despite the declines of PBDE levels, our findings indicate that the current levels of PBDEs, as well as PCBs and OCPs, may still pose health effects for house cats and, possibly, humans.

A comparative assessment of human exposure to tetrabromobisphenol A and eight bisphenols including bisphenol A via indoor dust ingestion in twelve countries

Tetrabromobisphenol A (TBBPA) and eight bisphenol analogues (BPs) including bisphenol A (BPA) were determined in 388 indoor (including homes and microenvironments) dust samples collected from 12 countries (China, Colombia, Greece, India, Japan, Kuwait, Pakistan, Romania, Saudi Arabia, South Korea, U.S., and Vietnam). The concentrations of TBBPA and sum of eight bisphenols (ƩBPs) in dust samples ranged from <1 to 3600 and from 13 to 110,000 ng/g, respectively. The highest TBBPA concentrations in house dust were found in samples from Japan (median: 140 ng/g), followed by South Korea (84 ng/g) and China (23 ng/g). The highest ∑BPs concentrations were found in Greece (median: 3900 ng/g), Japan (2600 ng/g) and the U.S. (2200 ng/g). Significant variations in BPA concentrations were found in dust samples collected from various microenvironments in offices and homes. Concentrations of TBBPA in house dust were significantly correlated with BPA and ∑BPs. Among the nine target chemicals analyzed, BPA was the predominant compound in dust from all countries. The proportion of TBBPA in sum concentrations of nine phenolic compounds analyzed in this study was the highest in dust samples from China (27%) and the lowest in Greece (0.41%). The median estimated daily intake (EDI) of ∑BPs through dust ingestion was the highest in Greece (1.6-17 ng/kg bw/day), Japan (1.3-16) and the U.S. (0.89-9.6) for various age groups. Nevertheless, in comparison with the reported BPA exposure doses through diet, dust ingestion accounted for less than 10% of the total exposure doses in China and the U.S. For TBBPA, the EDI for infants and toddlers ranged from 0.01 to 3.4 ng/kg bw/day, and dust ingestion is an important pathway for exposure accounting for 3.8-35% (median) of exposure doses in China.

Insights into PBDE Uptake, Body Burden, and Elimination Gained from Australian Age-Concentration Trends Observed Shortly after Peak Exposure

BACKGROUND

Population pharmacokinetic models combined with multiple sets of age-concentration biomonitoring data facilitate back-calculation of chemical uptake rates from biomonitoring data.

OBJECTIVES

We back-calculated uptake rates of PBDEs for the Australian population from multiple biomonitoring surveys (top-down) and compared them with uptake rates calculated from dietary intake estimates of PBDEs and PBDE concentrations in dust (bottom-up).

METHODS

Using three sets of PBDE elimination half-lives, we applied a population pharmacokinetic model to the PBDE biomonitoring data measured between 2002-2003 and 2010-2011 to derive the top-down uptake rates of four key PBDE congeners and six age groups. For the bottom-up approach, we used PBDE concentrations measured around 2005.

RESULTS

Top-down uptake rates of Σ4BDE (the sum of BDEs 47, 99, 100, and 153) varied from 7.9 to 19 ng/kg/day for toddlers and from 1.2 to 3.0 ng/kg/day for adults; in most cases, they were--for all age groups--higher than the bottom-up uptake rates. The discrepancy was largest for toddlers with factors up to 7-15 depending on the congener. Despite different elimination half-lives of the four congeners, the age-concentration trends showed no increase in concentration with age and were similar for all congeners.

CONCLUSIONS

In the bottom-up approach, PBDE uptake is underestimated; currently known pathways are not sufficient to explain measured PBDE concentrations, especially in young children. Although PBDE exposure of toddlers has declined in the past years, pre- and postnatal exposure to PBDEs has remained almost constant because the mothers' PBDE body burden has not yet decreased substantially.

High levels of polybrominated diphenyl ethers in vacuum cleaner dust from California fire stations

Firefighters are exposed to chemicals during fire events and may also experience chemical exposure in their fire stations. Dust samples from used vacuum cleaner bags were collected from 20 fire stations in California and analyzed for polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) using gas chromatography-mass spectrometry. Median dust concentrations were higher for PBDEs (e.g., 47 000 ng/g for BDE-209) than for PAHs (e.g., 220 ng/g for benzo[a]pyrene) or PCBs (e.g., 9.3 ng/g for PCB-180). BDE-209 concentrations in dust from California fire stations were among the highest of any previously documented homes or occupational settings in the world. We examined factors such as the frequency of emergency responses, the number of fire vehicles on site, and building age, but we could not account for the high levels of BDE-209 observed in fire station dust. Based on the findings of our pilot study, we hypothesize that possible sources of BDE-209 in fire stations include contaminated ash tracked back from fire events via boots, clothing, and other equipment as well as specialized equipment treated with BDE-209, including turnout gear and fire vehicles. We suggest possible follow-up studies to confirm these hypotheses.