Estimation of Exposure to Organic Flame Retardants via Hand Wipe, Surface Wipe, and Dust: Comparability of Different Assessment Strategies

A review of liquid crystal monomers (LCMs) as emerging contaminants: Environmental occurrences, emissions, exposure routes and toxicity

The widespread occurrence of liquid crystal monomers (LCMs) in the environment has raised concerns about their persistence, bioaccumulation, and toxicity (PBT). Here we review the lifecycle of environmental LCMs, focusing on their occurrences, emission sources, human exposure routes, and toxicity. Industrial emissions from Liquid Crystal Display (LCD) manufacturing and e-waste recycling are the primary point sources of LCMs. In addition, emissions from LCD products, air conditioning units, wastewater treatment plants, and landfills contribute to environmental occurrence of LCMs as secondary sources. Dietary routes were identified as the primary exposure pathways to humans. E-waste dismantling workers and infants/children are vulnerable populations to LCMs exposure. Exposure to LCMs has been shown to potentially induce oxidative stress, metabolic disorders, and endocrine disruption. Accumulation of LCMs in the brain and liver tissues of exposed animals highlights the need for toxicokinetic studies.

Human dermal exposure to short- and medium-chain chlorinated paraffins: Effect of populations, activities, gender, and haze pollution

Human dermal exposure to chlorinated paraffins (CPs) has not been well documented. Therefore, hand wipes were collected from four occupational populations to analyze short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) in order to estimate dermal uptake and oral ingestion via hand-to-mouth contact. The total CP levels (∑SCCPs and ∑MCCPs) in wipes ranged from 71.4 to 2310 µg/m2 in security guards, 37.6 to 333 µg/m2 in taxi drivers, 20.8 to 559 µg/m2 in office workers, and 20.9 to 932 µg/m2 in undergraduates, respectively. Security guards exhibited the highest levels of ∑SCCPs among four populations (p < 0.01). In undergraduates engaged in outdoor activities, C13 emerged as the most dominant SCCPs homologue group, followed by C12, C11, and C10. The levels of ∑SCCPs and ∑MCCPs in males in light haze pollution were significantly higher than that in heavy haze pollution (p < 0.05). The median estimated dermal absorption dose of SCCPs and MCCPs via hand was 22.2 and 104 ng (kg of bw)-1 day-1, respectively, approximately 1.5 times the oral ingestion [12.3 and 74.4 ng (kg of bw)-1 day-1], suggesting that hand contact is a significant exposure source to humans.

The impact of brominated flame retardants (BFRs) on pulmonary function in US adults: a cross-sectional study based on NHANES (2007-2012)

Brominated flame retardants (BFRs) are a group of chemicals widely used in various applications to prevent or slow down the spread of fire. However, they have adverse effects on human health. There is a relative scarcity of population-based studies regarding BFRs, particularly their impact on the respiratory system. This study aimed to investigate the influence of BFRs on pulmonary function using data from the National Health and Nutrition Examination Survey. The study found that elevated serum concentrations of certain BFRs were associated with pulmonary ventilatory dysfunction. Adjusted analyses revealed positive correlations between PBDE47, PBDE183, and PBDE209 concentrations and ventilatory dysfunction. The analysis of mixed BFRs showed a positive relationship with pulmonary ventilation dysfunction, with PBDE47 making the most significant contribution. Our study demonstrates that both individual and combined BFRs exposure can lead to impaired pulmonary ventilation function. These findings provide evidence of the adverse effects of BFRs on lung function, emphasizing the importance of further investigating the potential health consequences of these compounds. Further large-scale longitudinal studies are needed to investigate this relationship in the future.

Global patterns of human exposure to flame retardants indoors

To fill the knowledge gaps regarding the global patterns of human exposure to flame retardants (FRs) (i.e., brominated flame retardants (BFRs) and organophosphorus flame retardants (OPFRs)), data on the levels and distributions of FRs in external and internal exposure mediums, including indoor dust, indoor air, skin wipe, serum and urine, were summarized and analysed. Comparatively, FR levels were relatively higher in developed regions in all mediums, and significant positive correlations between FR contamination and economic development level were observed in indoor dust and air. Over time, the concentration of BFRs showed a slightly decreasing trend in all mediums worldwide, whereas OPFRs represented an upward tendency in some regions (e.g., the USA and China). The occurrence levels of FRs and their metabolites in all external and internal media were generally correlated, implying a mutual indicative role among them. Dermal absorption generally contributed >60% of the total exposure of most FR monomers, and dust ingestion was dominant for several low volatile compounds, while inhalation was found to be negligible. The high-risk FR monomers (BDE-47, BDE-99 and TCIPP) identified by external exposure assessment showed similarity to the major FRs or metabolites observed in internal exposure mediums, suggesting the feasibility of using these methods to characterize human exposure and the contribution of indoor exposure to the human burden of FRs. This review highlights the significant importance of exposure assessment based on multiple mediums for future studies.

A comprehensive assessment of external exposure to persistent halogenated organic pollutants for residents in an e-waste recycling site, South China

Human skin wipes from 30 participants, air, dust, and food items were collected from a former electronic waste site in South China to provide a comprehensive understanding of residents' exposure to halogenated flame retardants (HFRs) and polychlorinated biphenyls (PCBs). The total concentration of halogenated organic pollutants (HOPs) in the dust, air, food and skin wipes ranged 240-25000 ng/g, 130-2500 pg/m3, 0.08-590 ng/g wet weight, and 69-28000 ng/m2, respectively. Wild fish, vegetables, and air were dominated by PCBs, whereas dust, livestock, and poultry were dominated by HFRs. The HOP concentrations were several orders of magnitude higher in local foodstuffs than in market foodstuffs. The chemical composition on the forehead was remarkably different from that on the hand. The importance of different exposure routes depends on the residents' food choices, except decabromodiphenyl ethane (DBDPE). For residents who consumed a 100-foot diet (mainly egg) and local wild fish, diet ingestion overwhelmed other exposure routes, and PCBs were mainly contributed by fish and HFRs by egg. For residents who consumed market food, the dermal absorption of most PCB congeners and dust ingestion of highly brominated flame retardants were relatively prominent. Inhalation was found to be a crucial route for pentabromoethylbenzene (PBEB).

Methods for the characterisation of dermal uptake: Progress and perspectives for organophosphate esters

Organophosphate esters (OPEs) are a group of pollutants that are widely detected in the environment at high concentrations. They can adversely affect human health through multiple routes of exposure, including dermal uptake. Although attention has been paid to achieving an accurate and complete quantification of the dermal uptake of OPEs, existing evaluation methods and parameters have obvious weaknesses. This study reviewed two main categories of methodologies, namely the relative absorption (RA) model and the permeability coefficient (PC) model, which are widely used to assess the dermal uptake of OPEs. Although the PC model is more accurate and is increasingly used, the most important parameter in this model, the permeability coefficient (Kp), has been poorly characterised for OPEs, resulting in considerable errors in the estimation of the dermal uptake of OPEs. Thus, the detailed in vitro methods for the determination of Kp are summarised and sorted. Furthermore, the commonly used skin membranes are identified and the factors affecting Kp and corresponding mechanisms are discussed. In addition, the experimental conditions, conclusions, and available data on Kp values of the OPEs are thoroughly summarised. Finally, the corresponding knowledge gaps are proposed, and a more accurate and sophisticated experimental system and unknown Kp values for OPEs are suggested.

Multi-pathway exposure assessment of organophosphate flame retardants in a southern Chinese population: Main route identification with compound-specificity

In this study, we conducted comprehensive organophosphorus flame retardant (PFR) exposure assessments of both dietary and non-dietary pathways in a rural population in southern China. Skin wipes were collected from 30 volunteers. Indoor and outdoor air (gas and particles), dust in the houses of these volunteers, and foodstuffs consumed by these volunteers were simultaneously collected. The total PFR concentrations in dust, gas, and PM2.5 varied from 53.8 to 5.14 × 105 ng/g, 0.528 to 4.27 ng/m3, and 0.390 to 16.5 ng/m3, respectively. The forehead (median of 1.36 × 103 ng/m2) and hand (median of 920 ng/m2) exhibited relatively high PFR concentrations, followed by the forearm (median of 440 ng/m2) and upper arm (median of 230 ng/m2). The PFR concentrations in the food samples varied from 0.0700 to 10.9 ng/g wet weight in the order of egg > roast duck/goose and vegetable > pork > chicken > fish. Tris(1-chloro-isopropyl) phosphate (TCPP) was the main PFR in the non-diet samples, whereas the profiles of PFR individuals varied by food type. Among the multiple pathways investigated (inhalation, dermal exposure, dust ingestion, and food ingestion), dermal absorption and dust ingestion were the predominant pathways for tris(2-chloroethyl) phosphate (TCEP) and bisphenol A-bis(diphenyl phosphate) (BDP), respectively, whereas dietary exposure was the most important route for other chemicals.

Co-occurrence of phthalate and non-phthalate plasticizers in dust and hand wipes: A comparison of levels across various sources

E-waste dismantlers' occupational exposure to plasticizers, particularly non-phthalate (NPAE) plasticizers, is poorly understood. This study monitored 11 phthalates (PAEs) and 16 NPAEs in dust and hand wipe samples from Central China e-waste workplace and ordinary homes. Concentrations of plasticizers in dust from e-waste dismantling workshops (median: 217 μg/g) were significantly lower than that from ordinary homes (462 μg/g; p < 0.01), however, the trend was similar but not significant in hand wipes from these two scenarios (50.2 vs. 72.3 μg/m2; p = 0.139). PAEs were still the dominant plasticizers, which is, on average, 5.46 and 3.58-fold higher than NPAEs. In all samples, di-(2ethylhexyl) phthalate (65.4%) and tri-octyl trimellitate (44.9%) were the most common PAE and NPAE plasticizers. Increasing dust concentrations of di-iso-nonyl ester 1,2-cyclohexane dicarboxylic acid, citrates and sebacates were significantly associated with their levels in worker's hand wipe, by contrast, this trend was not found in general population. Dust ingestion was the main channel, followed by hand-to-mouth contact, all participants' daily plasticizer intakes (median: 154 ng/kg bw/day) are within safety limits. Our work highlights knowledge gaps about co-exposure to PAEs and NPAEs by multiple pathways in occupational e-waste workers, which could provide baseline data in the future.

A systematic characterization of soil/dust ingestion for typical subpopulations in China

An accurate assessment of human exposure to pollutants through the ingestion of dust and/or soil particles depends on a thorough understanding their rate of human ingestion. To this end, we investigated the load and size distribution patterns of dust/soil particles on the hands of three typical subpopulations, including preschoolers, college students, and security guards (outdoor workers). The geometric mean diameter of dust/soil particles on hands was observed to be 38.7 ± 11.2, 40.0 ± 12.1, and 36.8 ± 10.4 μm for preschoolers, college students, and security guards, respectively. The particle size distribution differed between subpopulations: Preschoolers were more exposed to fine particles, whereas security guards were exposed to more coarse particles. The geometric means of dust/soil particle loading on the hands were 0.126, 0.0163, and 0.0377 mg/cm2 for preschoolers, college students, and security guards, respectively. Males had statistically higher dust/soil particle loadings on hands than females, notably for preschoolers and college students; preschoolers with frequent hand contact with the bare ground had higher dust/soil particle loadings compared to those of peers in contact with commercial and residential grounds. The mean total dust/soil particle ingestion rate was estimated to be 245, 19.7, and 33.1 mg/day for preschoolers, college students, and security guards, respectively. Our estimates for college students and security guards are close to the consensus central-tendency values recommended by the U.S. EPA's Exposure Factor Handbook for American adults, whereas the estimates for children are much higher than the upper percentile values recommended for American children.

Occurrence of hexabromocyclododecanes (HBCDs) and tetrabromobisphenol A (TBBPA) in indoor dust from different microenvironments: levels, profiles, and human exposure

The levels and distributions of hexabromocyclododecane diastereoisomers (HBCDs) (including α, β, and γ-HBCD) and tetrabromobisphenol A (TBBPA) were investigated in indoor dust from bedrooms and offices. HBCDs diastereoisomers were the most abundant compounds in the dust samples, and the concentrations of ∑HBCDs in the bedrooms and offices ranged from 10.6 to 290.1 ng/g and 17.6 to 1521.9 ng/g, respectively. The concentrations of target compounds in the offices were generally higher than those in the bedrooms, probably due to the presence of more electrical equipment in the offices. In this study, highest levels of target compounds were all found in the electronics. In the bedrooms, the highest mean level of ∑HBCDs was found in air conditioning filter dust (118.57 ng/g), while the personal computer table surface dust showed the peak mean concentrations of ∑HBCDs (290.74 ng/g) and TBBPA (539.69 ng/g) in the offices. Interestingly, a significantly positive correlation was observed between the concentrations of ∑HBCDs in windowsills and beddings dust in the bedrooms, suggesting beddings was one of the crucial sources of ∑HBCDs in the bedrooms. The high dust ingestion values of ∑HBCDs and TBBPA were 0.046 and 0.086 ng/kg bw/day for adults, while 0.811 and 0.04 ng/kg bw/day for toddlers, respectively. The high dermal exposure values of ∑HBCDs were 0.026 and 0.226 ng/kg bw/day for adults and toddlers, respectively. Except for dust ingestion, other human exposure pathways (such as the dermal contact with beddings and furniture) should be paid attention.

Health Risk Assessment of Organophosphate Flame Retardants in Soil Across China Based on Monte Carlo Simulation

Health risks from exposure to contaminants are generally estimated by evaluating concentrations of the contaminants in environmental matrixes. However, accurate health risk assessment is difficult because of uncertainties regarding exposures. This study aims to utilize data on the concentrations of organophosphate flame retardants (OPFRs) in surface soil across China coupled with Monte Carlo simulations to compensate for uncertainties in exposure to evaluate the health risks associated with contamination of soil with this class of flame retardants. Results revealed that concentrations of ∑OPFRs were 0.793-406 ng/g dry weight (dw) with an average of 23.2 ng/g dw. In terms of spatial distribution, higher OPFRs concentrations were found in economically developed regions. Although the values of health risk of OPFRs in soil across China were below the threshold, the high concentrations of OPFRs in soil in some regions should attract more attentions in future. Sensitivity analysis revealed that concentrations of OPFRs in soil, skin adherence factor, and exposure duration were the most sensitive parameters in health risk assessment. In summary, the study indicated that the national scale soil measurement could provide unique information on OPFRs exposure and health risk assessment, which was useful for the management of soil in China and for better understanding of the environmental fate of OPFRs in the global perspective.

Underlying Degradation of Phthalates via Microbials in Dust from Different Microenvironments

Phthalate monoesters (me-PAEs) have been used as biomarkers for assessing human exposure to phthalate esters (PAEs) for a long time, and studies on the sources and distribution of me-PAEs in the environment are limited. In this study, dust samples from microenvironments were collected to measure the occurrence of PAEs and me-PAEs, as well as the bacterial diversity. The results indicated that me-PAEs coexisted with PAEs in different microenvironmental dust samples, with concentrations of nine PAEs and 16 me-PAEs ranging from 108 to 1450 μg/g (median range) and 6.00 to 21.6 μg/g, respectively. The concentrations of several low molecular weight me-PAEs (e.g., monomethyl phthalate and monoethyl phthalate) in dust were even significantly higher than those of their parents. The bacteria in the dust were mainly predominant with Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes (total abundance >90%). Bacteria from bus and air conditioning dust samples had the highest species richness and species diversity. Seven genes of suspected enzymes with the ability to degrade PAEs were selected, and the concentration of me-PAEs increased with increasing abundance of enzyme function. Our findings will provide useful information on the profiles of me-PAEs and their potential sources in indoor dusts, which will benefit the accurate estimation of human exposure.

Exposure to novel brominated and organophosphate flame retardants and associations with type 2 diabetes in East China: A case-control study

The alternative flame retardants, novel brominated flame retardants (NBFRs) and organophosphate flame retardants (OPFRs) are ubiquitous in the environment and biota and may induce endocrine disruption effects. Associations between traditional endocrine-disrupting chemicals and type 2 diabetes have been extensively reported in epidemiological studies. However, the effects of NBFRs and OPFRs in humans have not been reported to date. This paper reports a case-control study of 344 participants aged 25-80 years from Shandong Province, East China, where potential associations between serum NBFR and OPFR concentrations and type 2 diabetes are assessed for the first time. After adjusting for covariates (i.e., age, sex, body mass index, smoking status, alcohol consumption, triglycerides, and total cholesterol), serum concentrations of pentabromotoluene, 2,3-dibromopropyl 2,4,6-tribromophenyl ether, tri-n-propyl phosphate, triphenyl phosphate, and tris (2-ethylhexyl) phosphate were significantly positively associated with type 2 diabetes. In the control group, decabromodiphenyl ethane and triphenyl phosphate were significantly positively associated with fasting plasma glucose, triglycerides, and high-density lipoprotein cholesterol. In the quantile g-computation model, significant positive mixture effect was found between the flame retardants mixtures and high-density lipoprotein cholesterol levels, and decabromodiphenyl ethane contributed the largest positive weights to the mixture effect. Overall, these findings suggest that exposure to NBFRs and OPFRs may promote type 2 diabetes.

Health Risks Posed by Dermal and Inhalation Exposure to High Concentrations of Chlorinated Paraffins Found in Soft Poly(vinyl chloride) Curtains

Chlorinated paraffins (CPs) are used in many products, including soft poly(vinyl chloride) curtains, which are used in many indoor environments. Health hazards posed by CPs in curtains are poorly understood. Here, chamber tests and an indoor fugacity model were used to predict CP emissions from soft poly(vinyl chloride) curtains, and dermal uptake through direct contact was assessed using surface wipes. Short-chain and medium-chain CPs accounted for 30% by weight of the curtains. Evaporation drives CP migration, like for other semivolatile organic plasticizers, at room temperature. The CP emission rate to air was 7.09 ng/(cm² h), and the estimated short-chain and medium-chain CP concentrations were 583 and 95.3 ng/m³ in indoor air 21.2 and 172 μg/g in dust, respectively. Curtains could be important indoor sources of CPs to dust and air. The calculated total daily CP intakes from air and dust were 165 ng/(kg day) for an adult and 514 ng/(kg day) for a toddler, and an assessment of dermal intake through direct contact indicated that touching just once could increase intake by 274 μg. The results indicated that curtains, which are common in houses, could pose considerable health risks through inhalation of and dermal contact with CPs.

A new insight into the emission source of DDT in indoor environment from rural area of South China and comprehensive human health exposure assessment

Human exposure to dichlorodiphenyltrichloroethanes (DDTs) and the subsequent risk to human health remain an important concern due to the "new" input of DDTs in the environment, especially since exposure to DDTs in indoor microenvironments is often ignored. In this study, we identified a new source of DDT emission in indoor environments and evaluated the health risk from the exposure to DDTs by investigating DDTs in indoor and outdoor dust, air, and coatings of household items in rural areas of Qingyuan, South China. The concentrations of DDTs in house dust and air were < MQL (method quantification limit)-3450 ng/g (median 42.4 ng/g) and 22.7-965 pg/m³ (median 49.5 pg/m³), respectively, which were significantly higher than the outdoor DDT values. Dichlorodiphenyldichloroethylene (DDE) was the main isomer in air samples, while DDT was the dominant isomer in indoor dust. Significant correlations between different DDT isomers were observed in indoor samples but not in outdoor samples. Furniture coating was identified as a source of DDTs in the indoor dust. The total daily exposure dose of DDTs (1.75 × 10^-2 ng/kg bw/day for adults and 1.28 × 10^-1 ng/kg bw/day for toddlers) through inhalation, dust ingestion, and dermal contact was found unlikely to pose a health risk. Our findings provide new insights into the emission sources and health risks caused by DDT indoors, highlighting the need to further investigate the toxicity mechanisms of parent DDT compound.

Handwipes as indicators to assess organophosphate flame retardants exposure and thyroid hormone effects in e-waste dismantlers

Dermal exposure is increasingly recognized as an important pathway for organic pollutant exposure. However, data on dermal exposure are limited, particularly with respect to the health effects. This study evaluated association between organophosphorus flame retardants (OPFRs) in handwipes and internal body burden on workers and adult residents in an electronic waste (e-waste) dismantling area. The impact of dermal exposure to OPFRs on thyroid hormones (THs) served as a biomarker for early effects. Triphenyl phosphate (TPhP) was the most detected compound in handwipes, with median levels of 1180, 200, and 24.0 ng in people identified as e-waste bakers, e-waste dismantlers, and adult residents. Among e-waste dismantlers, TPhP levels in handwipes were positively correlated with paired serum TPhP and urinary diphenyl phosphate (DPhP) levels. In multiple linear regression models controlling for sex, age and smoking, TPhP levels in handwipes of e-waste dismantlers were significantly negatively correlated with three THs used to evaluate thyroid function: serum reverse 3,3',5-triiodo-L-thyronine (rT3), 3,3'-diiodo-L-thyronine (3,3'-T2), and 3,5-diiodo-L-thyronine (3,5-T2). These findings suggest that handwipes can act as non-invasive exposure indicators to assess body burden of dermal exposure to TPhP and health effects on THs of e-waste dismantlers. This study highlights importance of OPFR effect on human THs through dermal exposure.

Tetrabromobisphenol A and hexabromocyclododecanes from interior and surface dust of personal computers: implications for sources and human exposure

Tetrabromobisphenol A (TBBPA) and hexabromocyclododecane isomers (HBCDs) are widely detected in indoor environments, but the research on the accumulation, contamination, and human exposure of TBBPA and HBCDs in electronic products dust is still limited. It is unclear whether electronic products might pose human health risk via dust ingestion and dermal absorption. In this study, the levels and distributions of TBBPA and HBCDs were investigated in the personal computer (PC) interior dust and PC surface (upper and bottom) wipes. The median concentrations of TBBPA in PC interior dust, upper, and bottom surface wipes were 168.1 ng/g, 13.2 ng/m², and 15.2 ng/m², respectively. These levels were generally higher than those of HBCDs, which were 95.2 ng/g, 11.7 ng/m², and 12.3 ng/m², respectively. No significant correlations were found among the PC upper and bottom surface wipes, and interior dust, indicating different sources of TBBPA and HBCDs in PC interior and surface dust. The TBBPA and HBCDs in the PC interior dust were mainly released from inner PC materials, while the sources of target compounds on the surface wipes were likely from external environments. The exposure values of two occupational populations (including PC owners and PC repair workers) to TBBPA and HBCDs were measured by PC interior dust and upper surface wipes. The results imply dust ingestion (including hand-to-mouth uptake) is the main contributor of the exposure route to TBBPA and HBCDs for both PC owners and repair workers. Compared to PC owners, PC repair workers showed the greater risk in exposure assessment, which should be paid more attention.

Distribution of flame retardants among indoor dust, airborne particles and vapour phase from Beijing: spatial-temporal variation and human exposure characteristics

The occurrence and distribution of 10 brominated flame retardants (BFRs) and 10 organophosphate flame retardants (OPFRs) were investigated in indoor dust, total suspended particles (TSP), and vapour phase from offices (n = 10), homes (n = 9), and day-care centres (n = 10) in Beijing, China. Three types of samples were collected biweekly from one office and one home over a year to examine temporal trends. BFRs in dust significantly correlated with those in TSP, while OPFRs significantly correlated among all three matrices. In addition, BFRs in dust (ng/g) and TSP (pg/m³) exhibited similar temporal trends with higher levels in the cold season, whereas OPFRs in TSP and vapour phase (pg/m³) showed similar temporal trends with higher levels in the warm season. The geometric mean concentrations of BFRs and OPFRs in the three matrices from the above mentioned three types of indoor microenvironments were used for exposure and health risk estimation, and ∑₇OPFRs showed much higher hazard index (HI) values than ∑₁₀BFRs for all subpopulations, and inhalation of OPFRs was a major risk source. With the volatility of flame retardants (FRs) decreasing, the contribution of dust ingestion and dermal absorption showed an increasing trend, and the contribution of inhalation exhibited a gradual decreasing trend, which implied the dominant exposure pathway to FRs is strongly related to the vapour pressure (25 °C, Pa) of these substances. Using a single type of microenvironment or the collection of samples at a single point in time can lead to overestimation or underestimation of overall exposure and risk for people to some extent. The correlations of FRs in dust, TSP, and vapour phase from indoor microenvironments, as well as their temporal trends were first reported in this study, which will provide a basis for more accurate FR exposure assessments in the future.

Ubiquitin proteasomal system is a potential target of the toxic effects of organophosphorus flame retardant triphenyl phosphate

The consumption of the widely used flame retardant Triphenyl phosphate (TPP) is increasing. It is now frequently detected in the environment and also domestically. Although the possibility of dermal exposure to TPP is quite high, little is known about its potential molecular toxicity mechanisms. In this study, we found that TPP caused cytotoxicity on human skin keratinocytes (HaCaT) and significantly inhibited the proliferation and cell migration in a concentration-dependent manner. Additionally, HaCaT cells were sensitive to TPP-induced apoptosis. Reactive oxygen species production was induced with TPP, which increased the protein carbonylation and lipid peroxidation levels. Moreover, TPP inhibited proteasome activity and increased the accumulation of ubiquitinated proteins. Exposure to TPP significantly increased the HSP90, HSP70, GRP94 and GRP78 protein levels. Overall, our findings indicate that TPP may pose a risk to human health and contribute to the current understanding of the risks of TPP at the molecular level.

Occupational exposure to rare earth elements: Assessment of external and internal exposure

Our study investigated occupational exposure to rare earth elements (REEs) in a major REE processing plant from North China by assessing both external exposure and internal exposure in the workers. An exposure group, including 50 workers in the processing plant, and a control group, including 50 workers from a liquor factory located 150 km away from the exposure group, were recruited in the study. Portable air sampler was employed to accurately measure individual exposure to the external environment, and the data demonstrating significantly higher contamination in the REE processing plant compared with the control group (i.e., 87.5 versus 0.49 μg/m³ of ΣREEs). Blood concentrations were also significantly higher in the exposure group (3.47 versus 2.24 μg/L of ΣREEs). However, the compositional profiles of REEs resembled between the exposure and control group in blood or air particles, indicating the influence of mining/processing activities on the surrounding regions. External exposure in the occupational environment appeared to significantly influence internal REE exposure in the REE processing workers. Some other sociodemographic and occupational factors, including the residence time and the type of work, could also influence occupational exposure to selected REEs. Our data clearly demonstrated the highly elevated REE contamination in both working environment and human bodies compared with the control subjects, raising the critical need for better assessing the health risks from occupational REE exposure and efficient management for occupational hazards.

Indoor exposure to selected flame retardants and quantifying importance of environmental, human behavioral and physiological parameters

Indoor exposure to organic flame retardants (FRs) has raised extensive concern due to associated adverse health effects. Indoor-exposure induced daily intakes of six widely used FRs individually ranged 0.002-611 ng/day and 0.02-463 ng/day, respectively, for adults and 2-6-year-old children; and resulting internal exposure levels ranged 0.1-159 and 2.1-4500 ng/g lipid, respectively. A proportion of 0.001-5.9% and 0.006-10.3% of individual FRs emitted into indoor air ultimately entered bodies of adults and children respectively. Tris(2-chloroisopropyl)phosphate dominated in emissions, whilst 2-ethylhexyl-2,3,4,5-tetrabromobenzoate dominated in human bodies. Hand-to-mouth contact was the most important exposure pathway for less volatile FRs including most brominated FRs, whilst inhalation was the predominant intake pathway of tris(2-chloroisopropyl)phosphate. Relative importance of 29 environmental, behavioral and physiological parameters was ranked to explore key drivers influencing exposure and accumulation of FRs in humans. Results suggested that frequent bathing and handwashing can reduce exposure effectively, especially for children. Bodyweight and lipid fraction were only positively related to internal accumulation and body-weight-normalized concentrations of compounds with low metabolic rates (half-lives ≥10³ h) in humans. Our findings help control indoor exposure to FRs and are supportive of human exposome studies in the future.

Identification of Fluorescent Brighteners as Another Emerging Class of Abundant, Ubiquitous Pollutants in the Indoor Environment

Fluorescent brighteners (FBs) are extensively used as important chemical additives in multiple industrial fields worldwide. The history of the use of global FBs spans over 60 years, but knowledge on their environmental occurrence and risks remains largely unknown. Here, we screened indoor dust and hand wipes from South China for a broad suite of 17 emerging FBs using a new comprehensive analytical method. All 17 FBs were detected in the indoor environment for the first time, most of them having been rarely investigated or never reported in prior environmental studies. Ionic FBs were found to be more abundant than nonionic ones. The median total concentrations of the 17 detectable FBs reached 11,000 ng/g in indoor dust and 2640 ng/m² in hand wipes, comparable to or higher than those of well-known indoor pollutants. Human exposure assessment indicated that hand-to-mouth contact is a significant pathway for exposure to FBs, with a comparable contribution to that of dust ingestion. Most of the newly identified FBs are predicted to have persistent, bioaccumulative, or toxic properties. Our work demonstrates that FBs are another class of highly abundant, hazardous, and ubiquitous indoor pollutants that have been overlooked for decades and points to an emerging concern.

E-waste dismantling-related occupational and routine exposure to melamine and its derivatives: Estimating exposure via dust ingestion and hand-to-mouth contact

Melamine (MEL) and its derivatives are increasingly applied as nitrogenous flame retardants in consumer products. Nevertheless, limited information is available on their environmental occurrence and subsequent human exposure via multiple exposure pathways. In this study, we analysed MEL and its derivatives in dust (indication of the dust ingestion route) and hand wipe samples (indication of the hand-to-mouth route) collected in various microenvironments. The levels of ∑MELs in both dust (median: 24,100 ng/g) and participant hand samples (803 ng/m²) collected in e-waste dismantling workshops were significantly higher than those in samples collected in homes (15,600 ng/g and 196 ng/m², respectively), dormitories (13,100 ng/g and 227 ng/m², respectively) and hotel rooms (11,800 ng/g and 154 ng/m², respectively). Generally, MEL dominated in dust samples collected in e-waste dismantling workshops, whereas cyanuric acid dominated in hand wipe samples. This may occur partly because the latter is an ingredient in disinfection products, which are more frequently employed in daily lives during the COVID-19 pandemic. Exposure assessment suggests that dust ingestion is an important exposure pathway among dismantling workers and the general population, whereas hand-to-mouth contact could not be overlooked in certain populations, such as children and dismantling workers not wear gloves at work.

Gas-particle partition and size-segregated distribution of flame retardants in indoor and outdoor air: Reevaluation on the role of fine particles in human exposure

In this study, we investigated the distribution of brominated and organophosphate flame retardants (BFRs and OPFRs) in the paired gaseous and nine size-segregated particulate samples collected from 8 typical indoor compartments and monthly outdoor in Xinxiang, China, respectively. For the indoor environments, total concentrations of FRs (Σ₁₉FRs) in bulk air ranged from 3.9 ng/m³ to 37.5 ng/m³, with that in children recreation center (37.5 ng/m³) and furniture store (28.7 ng/m³) showing highest levels. In the outdoor air, Σ₁₉FRs ranged from 3.1 ng/m³ to 13.6 ng/m³ among the 12 months, with that from late spring and summer being the highest. OPFRs had higher concentration than BFRs, with the total concentration of OPFRs accounting for 77%-99% of ∑₁₉FRs. TCIPP (tris(chloroiso-propyl) phosphate), TCEP (tris(2-chloroethyl) phosphate), TEP (triethyl phosphate) and DBDPE (decabromodiphenyl ethane), BDE-209 (decabromodiphenyl ether) were the predominant analogs. Specifically, BFRs tended to enrich in gas phase indoors and coarse particles (aerodynamic diameters >3.3 μm) outdoors, but OPFRs mainly distributed in coarse particles both indoors and outdoors. The size distribution patterns varied among FRs, with the higher volatile FRs (e.g., TCEP, TCIPP) distributed more uniformly across particulate size. Although the distribution patterns of FRs in air were driven by multiple factors, organic carbon and element carbon in particulate matter had an influence to a certain extent. Health risks from exposure to FRs were characterized via the hazard quotient approaches. The total noncarcinogenic risks of ∑₁₆FRs from inhalation were higher than that from air to skin transport, and the risks resulted from coarse particle-bound ∑₁₆FRs (>3.3 μm) and gas phase were both significantly higher than that from fine fraction (<3.3 μm) in all scenarios, implying that FRs in coarse particles should not be underestimated.

Identifying dermal exposure as the dominant pathway of children's exposure to flame retardants in kindergartens

Exploration of multiple sources of brominated (BFRs) and organophosphate flame retardants (OPFRs) for children promotes the understanding of exposure pathways and health risk. 10 BFRs and 9 OPFRs were measured in skin wipes from hands, forehead, and arms of 30 children, and surface wipe samples from sills, toys, desks and floors, and indoor air samples of kindergartens from Xinxiang, China. Higher ∑₉OPFRs concentrations were observed in the forehead (1840 ng/m²), followed by hand (1420 ng/m²) and arm wipes (1130 ng/m²), and the ∑₈BFRs concentrations in forehead, hand and arm wipes were 116, 315 and 165 ng/m², respectively. The total concentration of OPFRs and BFRs in floor wipes (66.1 and 24.5 ng/m²) were lower than those in toy (205 and 535 ng/m²), sill (227 and 30.1 ng/m²) and desk (84.4 and 139 ng/m²) wipes. Concentrations of FRs in forehead wipes were significantly correlated with those in gaseous air (p < 0.05), moderate correlations were found between the hand wipes and surface wipes (p = 0.054). We estimated the daily average dosages (DADs) of children exposure to FRs via multiple pathways. Compared to DADs via inhalation and hand-to-mouth transfer, dermal exposure was determined to be the predominant exposure pathway to ∑₉OPFRs and ∑₈BFRs.

Electronic-Waste-Driven Pollution of Liquid Crystal Monomers: Environmental Occurrence and Human Exposure in Recycling Industrial Parks

Liquid crystal monomers (LCMs) in liquid crystal displays (LCDs) may be released into the environment, especially in electronic waste (e-waste) recycling industrial parks with a high pollution risk. However, little has been known about the environmental release and human exposure to LCMs until now. Herein, a total of 45 LCMs were detected in LCDs of commonly used smartphones and computers by high-resolution mass spectrometry with suspect screening analysis. Fluorinated biphenyls and their analogs were the dominant LCMs. Based on available standards of the screening results and previous studies, 55 LCMs were quantified in samples from an e-waste recycling industrial park in Central China. The LCMs were frequently detected in outdoor dust (n = 43), workshop #1 indoor dust (n = 53), and hand (n = 43) and forehead wipes (n = 43), with median concentrations of 6950 ng/g, 67,400 ng/g, 46,100 ng/m², and 62,100 ng/m², respectively. The median estimated daily intake values of the LCMs via dust ingestion and dermal absorption were 48.3 and 16.5 ng/kg body weight/day, respectively, indicating a high occupational exposure risk of these compounds. In addition, 16 LCMs were detected in the serum of eight elderly people (≥60 years old) with over 5 years of experience in e-waste dismantling operations, resulting in a total concentration range of 3.9-26.3 ng/mL.

Perfluoroalkyl acids in dust on residential indoor/outdoor window glass in Chinese cities: occurrence, composition, and toddler exposure

The dust on indoor and outdoor surfaces of the window glasses were collected using sterile cotton balls in 11 cities from China. Two sampling campaigns were conducted with the time interval of 7 days to investigate the accumulation especially during the Spring festival holidays. Twenty-nine perfluoroalkyl acids (PFAA) were quantified to investigate concentration, composition, and toddlers' exposure. The concentrations of ∑PFAA ranged from no detection (nd) to 43 ng/m2 (mean 8.9 ± 10 ng/m2). Perfluorobutanoic acid (PFBA) was detected in 78% samples and accounted for 55 ± 21% of ∑PFAA concentrations. 6:2 fluorotelomer sulfonic acid (6:2 FTSA) and hexafluoropropylene oxide dimer acid (HFPO-DA) were detected in more than 50% samples indicating the use of alternatives. Fluorotelomer carboxylic acid (FTCA) and fluorotelomer unsaturated acid (FTUCA) were found in the dust, implying the degradation of fluorotelomer alcohols (FTOH). The highest concentration of ∑PFAA (43 ng/m2) was found in outdoor dust from Xinzhou, Shanxi Province. Higher ∑PFAA concentrations were found in indoor dust than outdoor in 6 paired samples (3 from Feb. 14 and 3 from Feb. 21). In Tianjin and Handan, the concentrations of ∑PFAA from outdoor surfaces were higher in sampling campaign I (SC I, Feb. 21) than in sampling campaign II (SC II, Feb. 14), implying intensive outdoor release. The exposure of 2-year-old toddlers to PFAA via hand-to-mouth ingestion and dermal absorption was estimated; the mean values of intake were 2.1 and 1.5 pg/kg body weight, respectively, assuming an exposure time of 1 h.

Measurement of polychlorinated biphenyls with hand wipes and matched serum collected from Chinese E-waste dismantling workers: Exposure estimates and implications

To date, dermal/hand-to-mouth exposure to chemicals in the e-waste recycling environment has not been sufficiently understood, and the importance of dermal absorption of chemicals in e-waste dismantling workers remains controversial. In this study, we utilized hand wipes and matched sera to characterize dermal/hand-to-mouth exposure to PCBs for e-waste dismantling workers, and potential effects on thyroid hormones were also assessed. PCB loadings in hand wipes varied from 0.829-265 ng wipe^-1 (11.3-2850 ng m^-2 wipe^-1), with 37.2 ng wipe^-1 (432 ng m^-2 wipe^-1) as the median value. Serum concentrations of PCBs ranged from 32.3-3410 ng g^-1 lipid weight (lw) with 364 ng g^-1 lw as the median value. Between wipes and sera, lower-chlorinated congeners (e.g. CB-28, -66, -74, -99,-105 and -118) showed significant associations (p < 0.01), but higher-chlorinated congeners (e.g. CB-138, -153, -156, -170, and -180) did not. These lower-chlorinated CBs were the major contributors to estimated dermal/hand-to-mouth average daily doses (ADDs) and the hazard index (HI). Correspondingly, their estimated contributions to serum levels by dermal absorption were also significant, with the contribution of CB-28 being as high as 21.4%. As a consequence, dermal absorption of some low-chlorinated congeners was a non-negligible route for e-waste dismantling workers. Although insignificant association was shown between serum PCBs and thyroid hormones, the potential health risk should be of concern due to the high levels of PCBs observed in workers' sera.

A Novel Personal Passive Sampler for Collecting Gaseous Phthalates

Dermal absorption of gaseous chemicals is an important contributor to increased health risk and has yet to be adequately addressed due to the lack of available sampling techniques. In the present study, a novel personal passive sampler consisting of a housing (embracing a polydimethylsiloxane (PDMS) disk as the sorbent phase, a membrane filter, and a stainless-steel mesh) and a watchband (traditional wristband) was constructed and used to characterize gaseous phthalates (PAEs) near the air-skin interface. In a real-life setting, the utility of the passive sampler was validated by comparing the composition profiles of PAEs in the PDMS disks and in active samples and watchbands. The compositions of PAEs were consistent in disks and gaseous constituents from ambient air, with low-molecular-weight (<306 g mol^-1) PAEs accounting for 87-100% and approximately 100%, respectively. Appreciable amounts of diisononyl phthalate, diisodecyl phthalate, dinonyl phthalate, and skin lipid (e.g., squalene) were detected in watchbands but not in disks. Apparently, the passive sampler can prevent particles and skin-related chemicals from adhering to the disk and collect gaseous PAEs only. The vast majority of PAEs in watchbands was associated with nongaseous constituents. The present study demonstrated that the sampling strategy is a key factor in exposure assessment.

Occurrence of novel organophosphate esters derived from organophosphite antioxidants in an e-waste dismantling area: Associations between hand wipes and dust

Electronic waste (e-waste) is a well-known source of plastic additives in the environment. However, the e-waste-related occupational exposure to organophosphite antioxidants (OPAs) and the relevant oxidation products-novel organophosphate esters (NOPEs)-via different pathways is still unknown. In this study, six OPAs and three NOPEs were measured in 116 dust and 43 hand-wipe samples from an e-waste dismantling area in Central China. The median concentrations of ΣOPAs and ΣNOPEs were 188 and 13,900 ng·g^-1 in workshop dust and 5,250 ng·m^-2 and 53,600 ng·m^-2 on workers' hands, respectively. The increasing concentrations of dust in the form of triphenyl phosphate (TPHP) (p < 0.01) and tris(2,4-di-tert-butylphenyl) phosphate (AO168 = O) (p < 0.05) were strongly associated with the corresponding concentration on workers' hands. Furthermore, men had significantly lower levels of NOPEs on their hands than did women (p < 0.01). Moreover, the hand wipe levels of AO168 = O (41,600 ng·m^-2) was significantly higher than that of the typical OPE (TPHP, 7370 ng·m^-2), and the hand-to-mouth contact (ΣOPAs, 9.48 ng·kg bw^-1·day^-1; ΣNOPEs, 109 ng·kg bw^-1·day^-1) was a more significant and integrated pathway than dust ingestion (ΣOPAs, 0.10 ng·kg bw^-1·day^-1; ΣNOPEs, 5.01 ng·kg bw^-1·day^-1) of e-waste related occupational exposure to these "new" chemicals.

Approach to Predicting the Size-Dependent Inhalation Intake of Particulate Novel Brominated Flame Retardants

The risk of human exposure to particulate novel brominated flame retardants (NBFRs) in the atmosphere has received increasing attention from scientists and the public, but currently, there is no reliable approach to predict the intake of these compounds on the basis of their size distribution. Here, we develop a reliable approach to predict the size-dependent inhalation intake of particulate NBFRs, based on the gas/particle (G/P) partitioning behavior of the NBFRs. We analyzed the concentrations of eight NBFRs in 363 size-segregated particulate samples and 99 paired samples of gaseous and bulk particles. Using these data, we developed an equation to predict the G/P partitioning quotients of NBFRs in particles in different size ranges (K_Pi) based on particle size. This equation was then successfully applied to predict the size-dependent inhalation intake of particulate NBFRs in combination with an inhalation exposure model. This new approach provides the first demonstration of the effects of the temperature-dependent octanol-air partitioning coefficient (K_OA) and total suspended particle concentration (TSP) on the intake of particulate NBFRs by inhalation. In an illustrative case where TSP = 100 μg m^-3, inhalation intake of particulate NBFRs exceeded the intake of gaseous NBFRs when log K_OA > 11.4.

Identifying Dermal Uptake as a Significant Pathway for Human Exposure to Typical Semivolatile Organic Compounds in an E-Waste Dismantling Site: The Relationship of Contaminant Levels in Handwipes and Urine Metabolites

Dermal exposure to semivolatile organic compounds (SVOCs) has recently attracted widespread attention; understanding these exposures is particularly important for people whose skin is frequently exposed to different pollution surfaces. In this study, handwipes were collected from exposed occupational workers and local residents near a typical electronic waste (e-waste) dismantling area; urine samples were also sampled. The wipes were analyzed for three typical SVOCs: polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), and organophosphate flame retardants (OPFRs). The median levels of PAHs, OPFRs, and PBDEs in handwipes from e-waste dismantlers were 96.0, 183, and 238 ng, respectively. The analytes were higher in the handwipes collected from workers than those from residents, indicating that they were subjected to greater dermal exposure during primitive e-waste dismantling activities. Among the three SVOCs, the strongest correlation was found between triphenyl phosphate (TPhP) in handwipes and diphenyl phosphate (DPhP) in paired urine; the next strongest correlations were between PAHs and PBDEs and their corresponding urinary metabolites. The results showed that TPhP contributed the highest exposure to e-waste dismantlers via dermal exposure. Our research highlights the importance of dermal exposure to TPhP, which should be considered in future exposure risk assessments.

Plastic additives and personal care products in south China house dust and exposure in child-mother pairs

Indoor environment constitutes an important source of industrial additive chemicals to human exposure. We hypothesized that the influence of residential environment on human exposure varies among different types of additive chemicals and differs between children and mothers. This study determined a suite of additive chemicals in house dust from South China dwellings (n = 47) and urine from child-mother pairs. Concentrations of phthalates (PAEs; median 601 μg/g) were 2-3 orders of magnitude greater than those of parabens (0.82 μg/g), bisphenols (3.31 μg/g), and benzophenone-related chemicals (2.69 μg/g). Urinary concentrations differed between children and mothers, but the pattern of differences varied between chemical groups. Children exhibited greater urinary levels of mono-PAEs than mothers (510 versus 395 ng/mL, p = 0.152), while the latter population exhibited greater levels of parabens and benzophenones. Regression analyses indicate a lack of association between dust and urinary levels for most chemicals, suggesting that other exposure pathways can complicate human exposure scenarios. Indeed, we estimated that the daily intake via dust ingestion only constituted 0.002-0.81% of total daily intake estimated based on urine data for mothers and 0.04-5.61% for children. Future efforts are needed to better characterize source-specific exposure for different populations.

Identifying dust as the dominant source of exposure to heavy metals for residents around battery factories in the Battery Industrial Capital of China

Heavy metals (HMs) are constantly released into the environment during the production and use of batteries. Battery manufacturing has been ongoing for over six decades in the "Battery Industrial Capital" (located in Xinxiang City) of China, but the potential exposure pathways of residents in this region to HMs remain unclear. To clarify the exposure pathways and health risk of human exposure to HMs, hand wipe samples (n=82) and fingernail samples (n=36) were collected from residents (including young children (0-6 years old), children (7-12 years old) and adults (30-60 years old)) living around battery factories. The total concentrations of the target HMs (Zn, Mn, Cu, Pb, Ni, Cr, Cd, Co) in hand wipes ranged from 133 to 8040 μg/m², and those in fingernails ranged from 9.7-566 μg/g. HM levels in the hand wipe and fingernail samples both decreased with age, and higher HM levels were observed for males than females. The HM composition profiles in these two matrices represented a high degree of similarity, with Zn as the predominant element, and thus, oral ingestion and dermal exposure via dust were expected to be the most important HM exposure pathways for residents in this region. The non-carcinogenic risks (HQs) from dermal and oral ingestion exposure to Cd, Cr, and Pb were higher than those of the other five elements for all three populations, and the HQ_derm of Cd for young children was 2.1 (HQ_oral=0.6). Moreover, the hazard index (HI) values of ∑₈HMs for young children (HI_total=5.2, HI_oral=2.0, HI_dermal=3.2) and children (HI_total=1.6, HI_oral=1.3, HI_dermal=0.3) exceeded the safe threshold (1.0). Therefore, young children and children should be prioritized for protection from HM pollution, and more attention should be paid to young children's dermal exposure to Cd in this region.

Organophosphate flame retardants and diesters in the urine of e-waste dismantling workers: associations with indoor dust and implications for urinary biomonitoring

Indoor dust ingestion is one of the main pathways for human exposure to organophosphate flame retardants (PFRs). The urinary concentrations of diesters (DAPs) are usually used as biomarkers to assess human exposure to PFRs. In this study, the PFR and DAP levels were measured in morning and evening urine samples of 30 workers from an e-waste dismantling site in southern China. The indoor dust samples were also collected from workshops and houses for analyzing associations between PFR and DAP levels in urine and dust. Tris(1-chloro-2-propyl) phosphate (TCIPP) and triphenyl phosphate (TPHP) were the dominant PFRs in dust, while bis(2-chloroethyl) phosphate (BCEP) and diphenyl phosphate (DPHP) were the major DAPs in dust. A significant positive correlation was observed between TPHP and DPHP concentrations in dust (p < 0.001), suggesting their potentially same source and the degradation of TPHP to form DPHP. TCIPP and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were the predominant PFRs, and BCEP, bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), and DPHP were the main DAPs in both the morning and evening urine samples. The DPHP levels in evening urine samples were significantly correlated with TPHP and DPHP levels (p < 0.01) in dust. A similar correlation was found for the BCEP levels in the evening urine samples and the TCEP and BCEP levels (p < 0.01) in dust. These results indicated that in addition to being biotransformed from their respective parent PFRs, direct ingestion from indoor dust could also be the potential source for urinary DPHP and BCEP. Since relatively low detection frequencies were observed for bis(1-chloro-2-propyl) phosphate (BCIPP) and bis(butoxyethyl) phosphate (BBOEP) in urine, they may not be the major metabolites of TCIPP and tris(2-butoxyethyl) phosphate (TBOEP), respectively, in the human body. However, BDCIPP can be considered a useful biomarker because it is a unique metabolite of TDCIPP and has high detection frequencies in urine samples. The results of this study indicated the limitations of solely using urinary DAPs as biomarkers for the evaluation of human exposure to PFRs, and certain PFRs as well as hydroxylated PFRs (OH-PFRs) should also be considered for urinary biomonitoring in future studies.

Brominated and phosphate flame retardants from interior and surface dust of personal computers: insights into sources for human dermal exposure

It remains unclear whether internal or external sources play the more significant role in flame retardant (FR) contamination of surface dust from personal computers (PCs), which may lead to bias on dermal exposure assessment of FRs. In the present study, the occurrence and profiles of several brominated and phosphate FRs were measured in the interior dust, and the upper surface (keyboard) and bottom surface (bottom cover) wipes of PCs. BDE 209 (639 ng/g), decabromodiphenyl ethane (DBDPE, 885 ng/g), and triphenyl phosphate (TPHP, 1880 ng/g) were the most abundant chemicals in interior PC dust, while tris(2-chloroisopropyl) phosphate (TCIPP), TPHP, and DBDPE were dominant on both surfaces of PCs. No significant correlation between interior dust and both PC surfaces was observed for concentrations of most FRs except BDE 183. Different sources of FRs for interior and surface dust of PCs were further revealed by principal component analysis (PCA). FRs from external sources, rather than emission from inner PC components, are likely the main contributor for FR profiles on PC surfaces. Exposure assessment results demonstrated a minor contribution from PC dermal contact, compared with hand-to-mouth uptake, to total exposure. The applicability of surface wipes to assess dermal exposure to FR-treated products needs to be further investigated.

A review of organophosphate esters in indoor dust, air, hand wipes and silicone wristbands: Implications for human exposure

The ubiquity of organophosphate esters (OPEs) in various environmental matrices inevitably pose human exposure risks. Numerous studies have investigated human exposure pathways to OPEs, including air inhalation, dust ingestion, dermal contact, and dietary and drinking water intake, and have indicated that indoor dust and indoor air routes are frequently the two main human exposure pathways. This article reviews the literature on OPE contamination in indoor air and dust from various microenvironments and on OPE particle size distributions and bioavailability in dust conducted over the past 10 years. Ways in which sampling strategies are related to the uncertainty of exposure assessment results and comparability among different studies in terms of sampling tools, sampling sites, and sample types are addressed. Also, the associations of OPEs in indoor dust/air with human biological samples were summarized. Studies on two emerging matrices, hand wipes and silicone wristbands, are demonstrated to be more comprehensive and accurate in reflecting personal human exposure to OPEs in microenvironments and are summarized. Given the direct application of some diester OPEs (di-OPEs) in numerous products, research on their existence in indoor dust and food and on their effects on human urine are also discussed. Finally, related research trends and avenues for future research are prospected.

Exposure pathways, levels and toxicity of polybrominated diphenyl ethers in humans: A review

Polybrominated diphenyl ethers (PBDEs) are extensively used as brominated flame retardants (BFRs) in different types of materials, which have been listed as Persistent Organic Pollutants (POPs) by the Stockholm Convention in 2009 and 2017. Due to their ubiquities in the environment and toxicities, PBDEs have posed great threat to both human health and ecosystems. The aim of this review is to offer a comprehensive understanding of the exposure pathways, levels and trends and associated health risks of PBDEs in human body in a global scale. We systematically reviewed and described the scientific data of PBDE researches worldwide from 2010 to March 2020, focusing on the following three areas: (1) sources and human external exposure pathways of PBDEs; (2) PBDE levels and trends in humans; (3) human data of PBDEs toxicity. Dietary intake and dust ingestion are dominant human exposure pathways. PBDEs were widely detected in human samples, especially in human serum and human milk. Data showed that PBDEs are generally declining in human samples worldwide as a result of their phasing out. Due to the common use of PBDEs, their levels in humans from the USA were generally higher than that in other countries. High concentrations of PBDEs have been detected in humans from PBDE production regions and e-waste recycling sites. BDE-47, -153 and -99 were proved to be the primary congeners in humans. Human toxicity data demonstrated that PBDEs have extensively endocrine disruption effects, developmental effects, and carcinogenic effects among different populations.

Estimation of internal human daily intakes of organophosphate esters using one-compartment toxicokinetic model in the whole blood from Hebei Province, China

To evaluate the human health risks attributed by organophosphate ester (OPE) exposure, it is very important to estimate the daily intakes (DIs) of OPEs in human. In this study, the DIs of OPEs were estimated using a simplified one-compartment toxicokinetic model based on their total clearance rates in human and their whole blood concentrations. Thirty paired human whole blood and plasma samples were collected from participants in Hengshui, Hebei Province, China. The detection frequencies of most OPEs in the whole blood were lower than 50.0%. Thus, the OPE levels in whole blood were converted from the corresponding plasma levels using the fractions of OPEs in plasma (F_p), which were estimated from an in vitro partition assay and the values were in the range of 0.52-0.98. The measured whole blood concentrations of triphenyl phosphate (TPHP) and tris(chloroethyl) phosphate (TCEP) were comparable to those converted from the plasma concentrations, suggesting that the conversion method was reliable. The estimated total DIs of TPHP, TCEP, and tris(2-chloroisopropyl) phosphate were 1-30 times of those derived by the external exposure method, which usually excluded many exposure sources. The estimated human health risks based on the DIs indicated that the carcinogenic and non-carcinogenic effects of OPEs for the participants in Hengshui, Hebei Province, China, were negligible. This study recommended a more reliable and simpler method to estimate the human health risks attributed to the exposure of OPEs.

Complex Mixtures of Chlorinated Paraffins Found in Hand Wipes of a Norwegian Cohort

Up to 18000 ng of total chlorinated paraffins (CPs) was found in hand wipes of individual adult participants in a Norwegian cohort study (n = 60), with a geometric mean (SD) value of 870 (2700) ng. The CPs covered a wide range of alkane chain lengths from C₇ to C₄₈ with variable chlorine substitution. Complex mixtures of very-short-chain (vSCCPs, C_<10), short-chain (SCCPs, C_10-13), medium-chain (MCCPs, C_14-17), and long-chain (LCCPs, C_>17) CPs were found, contributing on average 0.3%, 20%, 58%, and 22%, respectively, of the total CPs. Significant positive correlations were found between CP levels and factors related to the indoor environment and product use, including living in a house/apartment built before the ban of SCCPs, having a sofa, the number of TVs in the home, and owning a car, which mirrors CP usage as flame retardants and/or plasticizers in consumer products. Compared to previous studies of other organic contaminants in hand wipe samples from the same cohort, CPs were the most abundant flame retardants. This is the first report of CPs in hand wipes, and dermal exposure based on these data suggested that hand contact could be an important human exposure pathway for LCCPs.

Halogenated Organic Pollutant Residuals in Human Bared and Clothing-Covered Skin Areas: Source Differentiation and Comprehensive Health Risk Assessment

To comprehensively clarify human exposure to halogenated flame retardants (HFRs) and polychlorinated biphenyls (PCBs) through dermal uptake and hand-to-mouth intake, skin wipe samples from four typical skin locations from 30 volunteers were collected. The total concentration of the target chemicals (24 HFRs and 16 PCBs) ranged from 203 to 4470 ng/m². BDE-209 and DBDPE accounted for about 37 and 40% of ∑₂₄HFRs, respectively, and PCB-41 and PCB-110 were the dominant PCB congeners, with proportion of 24 and 10%, respectively. Although exhibiting relatively lower concentrations of contaminants than bared skin locations, clothing-covered skin areas were also detected with considerable levels of HFRs and PCBs, indicating clothing to be a potentially significant exposure source. Significant differences in HFR and PCB levels and profiles were also observed between males and females, with more lower-volatility chemicals in male-bared skin locations and more higher-volatility compounds in clothing-covered skin locations of female participants. The mean estimated whole-body dermal absorption doses of ∑₈HFRs and ∑₁₆PCBs (2.9 × 10^-4 and 6.7 × 10^-6 mg/kg·d) were 1-2 orders of magnitude higher than ingestion doses via hand-to-mouth contact (6.6 × 10^-7 and 3.1 × 10^-7 mg/kg·d). The total noncarcinogenic health risk resulted from whole-body dermal absorption and oral ingestion to ∑₇HFRs and ∑₁₆PCBs were 5.2 and 0.35, respectively.

Beyond Phthalate Diesters: Existence of Phthalate Monoesters in South China House Dust and Implications for Human Exposure

Despite phthalate monoesters (mono-PAEs) being commonly recognized as metabolic products of phthalate diesters (di-PAEs), investigations on their environmental occurrences, particularly in indoor environments, remain limited. The present study demonstrated the presence mono-PAEs, along with a variety of di-PAEs, in house dust collected from 83 South China families. Among 15 target mono-PAEs, monobutyl phthalate (median concentration, 21.54 μg/g) dominated over other mono-PAEs in indoor dust, followed by monoethylhexyl phthalate (9.44 μg/g), monoisobutyl phthalate (5.14 μg/g), monomethyl phthalate (MMP; 2.05 μg/g), and several others. The total concentrations of detectable mono-PAEs (median, 45.40 μg/g) constituted an average of 6.7 ± 3.7% of the total concentrations of their parent diesters in the same dust. Molar concentration ratios of mono-PAEs to their respective di-PAEs varied greatly among chemicals (median, 0.001-3.1), with the highest ratios determined for the MMP/dimethyl phthalate and mono-/diisopropyl phthalate pairs (i.e., 3.1 and 1.5, respectively). In addition, no significant associations were observed between dust-associated mono- or di-PAEs and urinary mono-PAEs detected in both children (n = 48) and adult participants (n = 41). We hypothesized that mono-PAEs in dust could originate from different sources (e.g., impurities in di-PAE formulas, degradation from di-PAEs, and direct application as commercial additives), while the relative importance of various origins could differ between chemicals. Our findings demonstrate broad occurrences of mono-PAEs in indoor environments, but future studies are needed to better elucidate their sources, fate in indoor and outdoor environments, and potential human health risks.

Biomonitoring of organophosphate triesters and diesters in human blood in Jiangsu Province, eastern China: Occurrences, associations, and suspect screening of novel metabolites

Since organophosphate (OP) triesters are ubiquitous in environmental matrices, there is an increasing concern regarding human exposure to OP triesters or their metabolites. In this study, we measured levels of 16 OP triesters and 4 OP diesters in n = 99 human blood samples of non-occupationally exposed adults (aged 18-87) from Jiangsu Province, eastern China. Based on the measured concentrations, statistical difference and correlativity were calculated to characterize the population diversity and potential sources of OP triester and diester. Di (2-ethylhexyl) phosphate (DEHP) and 2-ethylhexyl diphenyl phosphate (EHDPP) were found in many participants' blood, with median concentrations of 1.2 (range: n.d. - 44.7, detection frequency: 99%) and 0.85 (n.d. - 28.8, 68%) ng mL^-1, respectively. Blood samples of older participants contained significantly lower concentrations of OP diesters or triesters than their younger counterparts (p < 0.01). Regional- and age-specific differences in the blood concentrations of OP triesters and diesters were attributed to disparities in environmental exposure intensity. EHDPP and tris (phenyl) phosphate (TPHP), the predominant OP triesters, exhibited significant positive correlation (p < 0.01, r = 0.84) suggestive of analogous transport behavior from similar exposure sources to humans. The increased correlations between diphenyl phosphate (DPHP) and TPHP as well as with EHDPP as observed from the multivariate regression suggests that DPHP could be derived from the metabolism of both TPHP (the crucial precursor) and EHDPP. When the blood samples were subsequently screened using high-resolution spectrometry, we detected five novel OP metabolites: glucuronide conjugates of hydroxylated DEHP (OH-DEHP glucuronide conjugate), 2-ethylhexyl monophenyl phosphate (EHMPP), hydroxylated EHMPP (OH-EHMPP), dihydroxylated bis(2-butoxyethyl) phosphate (di-OH-BBOEP), and dihydroxylated tris(butyl) phosphate (di-OH-TNBP). Overall, this study provides novel information regarding the occurrence of OP triesters and diesters, and further suggested several novel OP metabolites in human blood.

Influence of Air Pollution on Inhalation and Dermal Exposure of Human to Organophosphate Flame Retardants: A Case Study During a Prolonged Haze Episode

The health impact of haze is of great concern, but few studies have explored its influence on human inhalation and dermal exposure to trace pollutants. Size-segregated atmospheric particles ( n = 72) and forehead wipe samples ( n = 80) from undergraduates were collected in Xinxiang, China, during a prolonged haze episode and analyzed for 10 organophosphate flame retardants (OPFRs). ∑TCPP and TCEP were the most abundant OPFR substances in all samples. The arithmetic mean particle-bound and forehead OPFR concentrations under a heavy pollution condition (air quality index (AQI), 350-550) were 41.9 ng/m³ (∑₈OPFRs) and 7.4 μg/m² (∑₆OPFRs), respectively, apparently greater than the values observed under a light pollution condition (AQI, 60-90) (19.5 ng/m³ and 3.9 μg/m², respectively). Meteorological conditions played distinctive roles in affecting the OPFR occurrence in atmospheric particles (statistically significant for TCEP and ∑TCPP) and forehead wipes (excluding TPHP), implying that OPFR exposure through inhalation and dermal absorption was synchronously influenced by air quality, and OPFRs on the forehead may be mainly absorbed from the air. Inhalation contributed dominantly to the total OPFR exposure dose for humans when using the relative absorption method to assess dermal exposure, while according to the permeability coefficient method, dermal exposure was much more significant than inhalation. The results of this study indicate that OPFR exposure should attract particular concern in regions with heavy air pollution.

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.

Spatial and Temporal Trends (2004-2016) of Selected Alternative Flame Retardants in Fish of the Laurentian Great Lakes

Following the phase-out of polybrominated diphenyl ether (PBDE) and hexabromocyclododecane (HBCDD) flame retardants (FRs) from North American markets, the use of alternative FRs has increased. In this study the occurrence and spatiotemporal distributions of 18 dechlorane analogues (collectively referred to as DECs) and 20 alternative brominated FRs (referred to as ABFRs, i.e., brominated FRs other than PBDEs and HBCDD) were investigated in top predator fish megacomposites (i.e., a composite of all 50 fish) collected yearly from each of the Great Lakes from 2004 to 2016. Frequently detected substances include dechlorane 602, 603, 604 Component B, anti- and syn-dechlorane plus, and chlordene plus, as well as several brominated benzene FRs (i.e., hexabromobenzene, pentabromotoluene, and tetrabromo- o-chlorotoluene). Concentrations of ΣDECs and ΣABFRs ranged from 0.33-31.9 ng/g lipid weight (lw) (0.01-8.3 ng/g wet weight or ww) and 0.91-54.7 ng/g lw (0.09-7.1 ng/g ww), respectively. Flame retardant contamination exhibited chemical-specific spatial variations across the five lakes. Concentrations of ΣABFRs in Lake Erie fish were generally lower than those from other lakes. By contrast, fish ΣDEC concentrations were highest in Lake Ontario and the composition of dechlorane analogues differed significantly between Lake Ontario and the other lakes, indicating likely point-source influences. Temporal analyses revealed declining trends of ΣDECs and ΣABFRs in most lakes except Lake Erie, with age corrected trend slopes of -13.5% to -8.8% and -20.1% to -7.0% per year, respectively.