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

Mechanisms of haze influencing phase distribution and human exposure to airborne flame retardants with different uses: Emission, partition, and dry deposition

This study elucidated the mechanisms governing variations in the occurrence and human exposure to flame retardants (FRs) with diverse applications on haze days. The high atmospheric stability on haze days converts the atmospheric environment into a closed system, where local emissions (LM), gas-to-particle transport (GPT), and dry deposition of particles (DP) determine the fate and destination of FRs. When LM < GPT and DP, FRs are removed by DP, thereby decreasing human exposure. Conversely, when LM ≈ GPT and DP, the increase in airborne particles on haze days only affects occurrences and human exposure to FRs with gas-particle partitioning quotient (log KP) ranging from -3.95 to -1.45. We also analysed three types of FRs in 198 size-segregated particulate samples and 22 gaseous samples collected on non-haze and haze days in a Chinese city where haze frequently occurs. This study validated the aforementioned mechanisms and fundamentally accounted for the decreased levels of polybrominated diphenyl ethers (PBDEs) in skin-wipe samples on haze days in other published studies. These results suggest that haze has diverse influences on human exposure to FRs and provide a new basis for a comprehensive understanding of the health effects of haze.

Intersecting circular economy and child health: A scoping review of legacy brominated flame retardants in plastic childcare products and toys

Polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD) are persistent organic pollutants (POPs) banned under the Stockholm Convention due to their severe health effects, including endocrine disruption, neurodevelopmental problems, and cancer. Historically used in electrical and electronic equipment (EEE), vehicles, furniture, and building materials, these chemicals persist in recycled plastics and have been found in children's products. Our scoping review synthesized emerging literature to assess the extent of these chemicals in children's products. Of 799 initial results, 28 studies met our inclusion criteria after removing duplicates and excluding those that met exclusion criteria. The 28 studies revealed widespread presence of legacy PBDEs and HBCDD in plastic childcare products and toys, including toys embedded in chocolates, often at concentrations exceeding the Basel Convention's low POP content limits. This widespread contamination stems from weak regulation of recycling practices in the circular economy, the use of recycled and potentially contaminated virgin plastics, and the absence of specific standards for POP-BFRs content in recycled plastics and children's products. Children's unique vulnerabilities make this issue critical. Global actions are, therefore, needed to address this problem. The Basel Convention should adopt stricter POP content limits to prevent the recycling of plastics with high PBDEs and HBCDD levels. Both the Stockholm and Basel Conventions should establish safe limits for these chemicals in recycled plastics and ban contaminated recycled plastics in children's products to ensure a safer circular economy. Future research should apply a lifecycle approach to identify and mitigate all sources of legacy PBDEs and HBCDD in children's products.

Exposure experiments and machine learning revealed that personal care products can significantly increase transdermal exposure of SVOCs from the environment

We investigated the impacts of personal care products (PCPs) on dermal exposure to semi-volatile organic compounds (SVOCs), including phthalates, organophosphate esters, polycyclic aromatic hydrocarbons (PAHs), ultraviolet filters, and p-phenylenediamines, through an experiment from volunteers, explored the impact mechanisms of PCP ingredients on dermal exposure, and predicted the PCP effects on SVOC concentrations in human serum using machine learning. After applying PCPs, namely lotion, baby oil, sunscreen, and blemish balm, the dermal adsorption of SVOCs increased significantly by 1.63 ± 0.62, 1.97 ± 0.73, 1.91 ± 0.48, and 2.03 ± 0.59 times, respectively, probably due to the absorption effects of PCP ingredients. Ingredient tocopherol can increase dermal adsorption of SVOCs by 2.59 ± 1.60 times. PCPs can either increase or decrease the SVOC transdermal exposure risks, depending on the properties of their ingredients. Blemish balm caused the highest hazard quotient for certain SVOCs, while tris(2-chloroethyl) phosphate (TCEP) exhibited the highest hazard quotient. We predicted the SVOC concentrations in serum before and after applying PCPs based on the PCP-increased skin permeation doses and machine learning. PCPs can significantly increase the serum concentrations of PAHs with 2-3 rings and TCEP. This study first revealed that PCPs can significantly increase the dermal exposure of SVOCs from the surroundings, resulting in potentially higher health risks.

Comparison of indoor and outdoor atmospheric organophosphorus flame retardants (OPFRs) from the petrochemical industrial area in North China: Occurrence, gas-PM2.5 distribution, source appointment and health implications

The consumption of organophosphorus flame retardants (OPFRs) has surged significantly recent years since global banning of brominated flame retardants (BFRs). Industrial activity is an important source of OPFRs, however there are few studies on OPFRs contamination in the indoor and outdoor atmosphere of industrial areas. A study was conducted to analyze contamination of 15 OPFRs individuals in both indoor and outdoor air and PM2.5 of living and industrial sites of the petrochemical industrial area (outdoor and indoor sites of living area was LO and LI, outdoor and indoor sites of industrial area was IO and II). The average concentrations of OPFRs in PM2.5 of LO (16.40 ng/m3) and IO (17.83 ng/m3) were similar, while LI (60.46 ng/m3) was higher than that in II (33.43 ng/m3). The average concentrations of indoor OPFR in PM2.5 and air in summer were 4.10 and 2.22 times higher than those in winter, respectively. This seasonal concentration variation of OPFRs may attribute to the influence of temperature that accelerated the releasing of OPFRs from materials. Source apportionment results indicated that the indoor source (material emission) was the dominant contributor of indoor OPFRs in PM2.5 and air, and outdoor sources (industrial and traffic sources) had significant contribution to OPFRs in indoor and outdoor air and outdoor PM2.5. The gas-particle partitioning of OPFRs had not reached equilibrium state. The KOA absorption model has better fitting effect for OPFRs with logKOA > 10. The health risk of OPFRs for both adult and child was neglectable. While considering the high contribution of TCEP to carcinogenic risk, and high contribution of TCPP to none-carcinogenic risk, their health risk should be given special attention.

Global human exposure of atmospheric polybrominated diphenyl ethers: Variation patterns of exposure pathways and phase contributions

At present, there are still certain limitations in the research on the pathways and phase contributions of semi-volatile organic compounds (SVOCs) to human exposure in the atmosphere. This study clarified the contribution rates of inhalation and dermal exposure of particulate and gaseous polybrominated diphenyl ethers (PBDEs) on a global scale, as well as their influencing factors and mechanisms. Data on gaseous PBDEs were collected from 125 cities across 38 countries and regions to predict size-resolved particulate exposure levels, utilizing our previous method for inhalation alongside a size-dependent prediction method for dermal exposure developed in this study. The global distribution of PBDEs in gas phase showed a significant negative correlation (r = - 0.40, p < 0.05) with the level of per capita GDP, resulting in a similar pattern of human exposure to atmospheric PBDEs. The highest daily intake was found in Africa (75.4 pg/(kg·day)), followed by Asia (21.8 pg/(kg·day)), North America (5.38 pg/(kg·day)) and Europe (1.92 pg/(kg·day)). Inhalation pathways dominated human exposure to atmospheric PBDEs. The contributions of particle phase to the total human exposure presented a pattern of Europe (26.8 %) < North America (33.5 %) < Asia (43.7 %) < Africa (59.8 %), exhibiting a significant positive correlation with TSP (r = 0.79, p < 0.01). An important finding was that the fluctuation of TSP around 70 μg/m3 may lead to alterations in the primary exposure phase for humans. Temperature exerted negative effects on the particulate contribution of low-brominated PBDEs varying in different individuals. In this study, a web platform was also developed, which offered predictions of inhalation and dermal exposures to SVOCs, obviously improving the efficiency of evaluating human exposure to atmospheric PBDEs and researching their exposure patterns.

Advanced understanding of the polybrominated diphenyl ethers (PBDEs): Insights from total environment to intoxication

Polybrominated diphenyl ethers (PBDEs) are brominated compounds connected by ester bonds between two benzene rings. There are 209 congeners of PBDEs, classified according to the number and position of the bromine atoms. Due to their low cost and superior flame retardant properties, PBDEs have been extensively used as flame retardants in electronic products, plastics, textiles, and other materials since the 1970s. PBDEs are classified as persistent organic pollutants (POPs) under the Stockholm Convention because of their environmental persistence, bioaccumulation, and toxicity to both humans and wildlife. Due to their extensive use and significant quantities, PBDEs have been detected across a range of environments and biological organisms. These compounds are known to cause damage to the metabolic system, exhibit neurotoxicity, and pose reproductive hazards. This review investigates the environmental distribution and human exposure pathways of PBDEs. Using China-a country with significant PBDE use-as an example, it highlights substantial regional and temporal variations in PBDE concentrations and notes that certain environmental levels may pose risks to human health. The article then examines the toxic effects and mechanisms of PBDEs on several major target organs, summarizing recent research and the specific mechanisms underlying these toxic effects from multiple toxicological perspectives. This review enhances our understanding of PBDEs' environmental distribution, exposure pathways, and toxic mechanisms, offering valuable insights for further research and management strategies.

Infants exposure to chemicals in diapers: A review and perspective

Diapers are a staple care product for infants, yet concerns persist regarding the potential risks posed by dermal exposure to chemicals through their usage. This review provides a comprehensive summary of reported chemicals, highlighting the frequent detection of polychlorodibenzo-p-dioxins (PCDDs), phthalates (PAEs), volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), bisphenols (BPs), organotins, and heavy metals. Disposable diapers commonly exhibit higher concentrations of VOCs, PAEs, BPs, and heavy metals than other chemicals. Our estimation reveals formaldehyde as posing the highest dermal exposure dose, reaching up to 0.018 mg/kg bw/day. Conversely, perfluorooctanoic acid (PFOA) exhibits lower exposure, but its non-cancer hazard quotient (0.062) is the highest. In most scenarios, the risk of chemical exposure through diapers for infants is deemed acceptable, while the risk is higher under some extreme exposure scenarios. Using the cancer slope factor recently suggested by U.S. EPA, the cancer risk in diapers raised by PFOA is 5.5 × 10-5. It should be noted that our estimation is approximately 1000-10,000 folds lower than some previous estimations. The high uncertainties associated with exposure and risk estimations are primarily raised by unclear parameters related to chemical migration coefficients, absorption factors, concentrations, and toxicity data for skin exposure, which requires research attention in future. Besides that, future research endeavors should prioritize the identification of potential toxic chemicals and the development of hygiene guidelines and standards.

Children's exposure to halogenated flame retardants and organophosphate esters through dermal absorption and hand-to-mouth ingestion in Swedish preschools

Children are exposed to endocrine disrupting chemicals (EDCs) through inhalation and ingestion, as well as through dermal contact in their everyday indoor environments. The dermal loadings of EDCs may contribute significantly to children's total EDC exposure due to dermal absorption as well as hand-to-mouth behaviors. The aim of this study was to measure potential EDCs, specifically halogenated flame retardants (HFRs) and organophosphate esters (OPEs), on children's hands during preschool attendance and to assess possible determinants of exposure in preschool indoor environments in Sweden. For this, 115 handwipe samples were collected in winter and spring from 60 participating children (arithmetic mean age 4.5 years, standard deviation 1.0) and analyzed for 50 compounds. Out of these, 31 compounds were identified in the majority of samples. Levels were generally several orders of magnitude higher for OPEs than HFRs, and 2-ethylhexyl diphenyl phosphate (EHDPP) and tris(2-butoxyethyl) phosphate (TBOEP) were detected in the highest median masses, 61 and 56 ng/wipe, respectively. Of the HFRs, bis(2-ethyl-1-hexyl)-2,3,4,5-tetrabromobenzoate (BEH-TEBP) and 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE-209) were detected in the highest median masses, 2.8 and 1.8 ng/wipe, respectively. HFR and/or OPE levels were found to be affected by the number of plastic toys, and electrical and electronic devices, season, municipality, as well as building and/or renovation before/after 2004. Yet, the calculated health risks for single compounds were below available reference dose values for exposure through dermal uptake as well as for ingestion using mean hand-to-mouth contact rate. However, assuming a high hand-to-mouth contact rate, at the 95th percentile, the calculated hazard quotient was above 1 for the maximum handwipe mass of TBOEP found in this study, suggesting a risk of negative health effects. Furthermore, considering additive effects from similar compounds, the results of this study indicate potential concern if additional exposure from other routes is as high.

Quantitative characterization of resident' exposure to typical semi-volatile organic compounds (SVOCs) around a non-ferrous metal smelting plant

To comprehensively characterize residents' exposure to major semi-volatile organic compounds (SVOCs), samples of indoor floor wipes, size-segregated airborne particles, gaseous air, food, and paired skin wipes were simultaneously collected from residential areas around a large non-ferrous metal smelting plant as compared with the control areas, and three typical SVOCs (including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and halogenated PAHs (HPAHs)) were determined. Comparison and correlation analysis among matrices indicated PAHs were the major contaminants emitted from metal smelting activities compared to HPAHs and PCBs, with naphthalene verified as the most important characteristic compound, and their accumulation on skin may be a comprehensive consequence of contact with floor dust and air. While patterns of human exposure pathways for the SVOCs were found to be clearly correlated to their vapor pressure, dermal absorption was the major contributor (51.1-76.3%) to total carcinogenic risk (TCR) of PAHs and HPAHs for surrounding residents, especially for low molecular weight PAHs, but dietary ingestion (98.6%) was the dominant exposure pathway to PCBs. The TCR of PAHs exceeded the acceptable level (1 × 10-4), implying smelting activities obviously elevated the health risk. This study will serve developing pertinent exposure and health risk prevention measures.

Multi-source exposure and health risks of phthalates among university students in Northeastern China

The endocrine disruptor phthalates (PAEs) are widely used as important chemical additives in a variety of areas around the globe. PAEs are toxic to reproduction and development and may adversely affect the health of adolescents. Risk assessments of exposure to PAEs from different sources are more reflective of actual exposure than single-source assessments. We used personal exposure parameters to estimate the dose of PAEs to 107 university students from six media (including dormitory dust, dormitory air, clothing, food, disposable food containers, and personal care products (PCPs)) and three exposure routes (including ingestion, inhalation, and dermal absorption). Individual factors and lifestyles may affect PAE exposure to varying degrees. Based on a positive matrix factorization (PMF) model, the results indicated that the main sources of PAEs in dust were indoor building materials and plastics, while PCPs and adhesives were the major sources of airborne PAEs. The relative contribution of each source to PAE exposure showed that food and air were the primary sources of dimethyl phthalate (DMP) and dibutyl phthalate (DBP). Air source contributed the most to diethyl phthalate (DEP) exposure, followed by PCPs. Food was the most significant source of diisobutyl phthalate (DiBP), benzyl butyl phthalate (BBP), and bis(2-ethylhexyl) phthalate (DEHP) exposure. Additionally, the exposure of DEHP to dust was not negligible. The ingestion pathway was the most dominant among the three exposure pathways, followed by dermal absorption. The non-carcinogenic risk of PAEs from the six sources was within acceptable limits. DEHP exhibits a low carcinogenic risk. We suggest university students maintain good hygienic and living habits to minimize exposure to PAEs.

Composition of indoor organic surface films in residences: simulating the influence of sources, partitioning, particle deposition, and air exchange

Indoor surfaces are coated with organic films that modulate thermodynamic interactions between the surfaces and room air. Recently published models can simulate film formation and growth via gas-surface partitioning, but none have statistically investigated film composition. The Indoor Model of Aerosols, Gases, Emissions, and Surfaces (IMAGES) was used here to simulate ten years of nonreactive film growth upon impervious indoor surfaces within a Monte Carlo procedure representing a sub-set of North American residential buildings. Film composition was resolved into categories reflecting indoor aerosol (gas + particle phases) factors from three sources: outdoor-originating, indoor-emitted, and indoor-generated secondary organic material. In addition to gas-to-film partitioning, particle deposition was modeled as a vector for organics to enter films, and it was responsible for a majority of the film mass after ∼1000 days of growth for the median simulation and is likely the main source of LVOCs within films. Therefore, the organic aerosol factor possessing the most SVOCs contributes most strongly to the composition of early films, but as the film ages, films become more dominated by the factor with the highest particle concentration. Indoor-emitted organics (e.g. from cooking) often constituted at least a plurality of the simulated mass in developed films, but indoor environments are diverse enough that any major organic material source could be the majority contributor to film mass, depending on building characteristics and indoor activities. A sensitivity analysis suggests that rapid film growth is most likely in both newer, more air-tight homes and older homes near primary pollution sources.

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.

Screening and Evaluation of Children's Sensitively Toxic Chemicals in New Mosquito Repellent Products Based on a Nationwide Investigation

New mosquito repellent products (NMRPs) are emerging popular repellents among children. There are increasing reports on children's sensitization reactions caused by NMRPs, while regulations on their productions, sales, or usage are still lacking. One of the reasons could be the missing comprehensive risk assessment. We first conducted a nationwide investigation on children's NMRP usage preferences. Then, we high-throughput screened volatile or semivolatile organic chemicals (VOCs/SVOCs) in five representative NMRPs by the headspace gas chromatography-orbitrap high-resolution mass spectrometry analytical method. After that, toxic compounds were recognized based on the toxicity forecaster (ToxCast) database. A total of 277 VOCs/SVOCs were recognized, and 70 of them were identified as toxic compounds. In a combination of concentrations, toxicities, absorption, distribution, metabolism, and excretion characteristics in the body, 28 chemicals were finally proposed as priority-controlled compounds in NMRPs. Exposure risks of recognized toxic chemicals through NMRPs by inhalation and dermal intake for children across the country were also assessed. Average daily intakes were in the range of 0.20-7.31 mg/kg/day for children in different provinces, and the children in southeastern coastal provinces were found to face higher exposure risks. By controlling the high-priority chemicals, the risks were expected to be reduced by about 46.8% on average. Results of this study are therefore believed to evaluate exposure risks, encourage safe production, and promote reasonable management of NMRPs.

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.

Kindergarten dust heavy metal(loid) exposure associates with growth retardation in children

Heavy metal contamination from electronic waste recycling sites is present in dust found in indoor kindergartens located in e-waste recycling areas, and its potential impact on child health is a significant concern. The association between heavy metal(loid)s and the child developmental indicators is still unclear. In 2019 and 2020, we enrolled 325 and 319 children in an e-waste recycling town, respectively. Corresponding 61 and 121 dust samples were collected from roads, houses, and kindergartens in the two years. The median concentrations of metals, including Cr, Ni, Cu, Zn, and Pb exceeded the allowable limits. The highest amount of cumulative enrichment (cEF) was observed in indoor kindergarten dust (cEF = 112.3400), followed by house dust (cEF = 76.6950) and road dust (cEF = 39.7700). Children residing in the e-waste town had below-average height and weight compared to their Chinese peers. Based on linear regression analysis, the daily intake of Cd, V, Mn, and Pb in indoor kindergarten dust was found to be negatively associated with head circumference (HeC) (P < 0.05). Similarly, the daily intake of As, Cd, and Ba in indoor kindergarten dust was found to be negatively associated with chest circumference (ChC) (P < 0.05). In addition, the daily intake of As, Cd, and Ba in indoor kindergarten dust was negatively correlated with body mass index (BMI), as per the results of the study (P < 0.05). Cross-product term analysis revealed a negative correlation between daily intake of heavy metal(loid)s and HeC, ChC, and BMI, with age and sex serving as influencing factors. In conclusion, exposure to heavy metal(loid)s in indoor kindergarten dust increases the risk of growth retardation and developmental delay in children.

Derivation and application of indoor air screening values for inhalation exposure to semi-volatile organic compounds

Semi-volatile organic compounds (SVOCs) are being increasingly studied in indoor air. The absence of health-based inhalation exposure guidelines for most SVOCs impedes the interpretation of indoor air concentrations from a health risk context. To accelerate the derivation of screening values for a large number of SVOCs, a tiered framework was developed to evaluate and adjust published hazard assessments for SVOCs to calculate benchmarks relevant for evaluation of inhalation risk. Inhalation screening values were derived for 43 SVOCs considered in this study, most of which required extrapolation from oral exposure guidelines. The screening values were compared to published SVOC concentrations in homes in Canada to evaluate the potential health risks of chronic exposure to SVOCs in indoor residential environments. SVOCs that could be prioritized for further evaluation were dibutyl phthalates (DBP), di(2-ethylhexyl) phthalate (DEHP) and polybrominated diphenyl ethers (PBDEs). The framework could be applied more broadly in the future to derive screening values for other non-traditional indoor air contaminants with limited inhalation hazard data or assessments.

Estimation of indoor soil/dust-skin adherence factors and health risks for adults and children in two typical cities in southern China

Soil/dust (SD) skin adherence is key dermal exposure parameter used for calculating the health risk of dermal exposure to contaminants. However, few studies of this parameter have been conducted in Chinese populations. In this study, forearm SD samples were randomly collected using the wipe method from population in two typical cities in southern China as well as office staff in a fixed indoor environment. SD samples from the corresponding areas were also sampled. The wipes and SD were analyzed for tracer elements (aluminum, barium, manganese, titanium, and vanadium). The SD-skin adherence factors were 14.31 μg/cm² for adults in Changzhou, 7.25 μg/cm² for adults in Shantou, and 9.37 μg/cm² for children in Shantou, respectively. Further, the recommended values for indoor SD-skin adherence factors for adults and children in Southern China were calculated to be 11.50 μg/cm² and 9.37 μg/cm², respectively, which were lower than the U.S. Environmental Protection Agency (USEPA) recommended values. And the SD-skin adherence factor value for the office staff was small (1.79 μg/cm²), but the data were more stable. In addition, PBDEs and PCBs in dust samples from industrial and residential area in Shantou were also determined, and health risks were assessed using the dermal exposure parameters measured in this study. None of the organic pollutants posed a health risk to adults and children via dermal contact. These studies emphasized the importance of localized dermal exposure parameters, and further studies should be conducted in the future.

Exploratory analysis of the association between organophosphate ester mixtures with high blood pressure of children and adolescents aged 8-17 years: cross-sectional findings from the National Health and Nutrition Examination Survey

Epidemiological studies on the effect of organophosphate esters (OPEs) on high blood pressure (BP) among children and adolescents are scant. Therefore, the main objective of the present study was to explore the effect of exposure to OPEs on high BP among children and adolescents. A total of 1340 participants were included in the current analyses. Multivariable logistic regression models were implemented to calculate odds ratios (ORs) and corresponding 95% confidence intervals (CIs) to examine the association between OPE metabolites and high BP. We also assessed the modified effect of sex, age, and overweight/obesity on this association. Furthermore, quantile g-computation (Qgcomp) and Bayesian kernel machine regression (BKMR) were exhibited to analyze the association between multiple OPE metabolite mixtures and high BP. After adjusting for covariates, the highest (vs. lowest) tertiles of bis (1-choloro-2-propyl) phosphate (BCPP), bis-2-chloroethyl phosphate (BCEP), and di-n-butyl phosphate (DBUP) were associated with 1.23 (95% CI: 0.83, 1.83), 1.27 (95% CI: 0.85, 1.92), and 1.01 (95% CI: 0.67, 1.53) odds ratios for high BP, respectively. In the Qgcomp, a quartile increase in OPE metabolite mixtures was weakly associated with an elevated risk of high BP (adjusted OR: 1.06, 95CI%: 0.81, 1.37). The results from BKMR showed a positive trend of association between OPE metabolite mixture on the risk of high BP. In conclusion, our study demonstrated that higher levels of BCPP, BCEP, and DBUP were weakly associated with high BP among US children and adolescents. Moderate evidence suggested OPE metabolite mixtures had positive joint effects on high BP. Consequently, longitudinal studies with repeated measurements are warranted to examine the relationships between multiple OPE metabolites and high blood pressure among children and adolescents.

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.