Unintentional emissions of polychlorinated naphthalenes in China: Sources, composition, and historical trends.

Polychlorinated naphthalenes (PCNs) are detrimental to human health and the environment. With the commercial production of PCNs banned, unintentional releases have emerged as a significant environmental source. However, relevant information is still scarce. In this study, provincial emissions for eight PCNs homologues from 37 sources in the Chinese mainland during the period of 1960-2019 were estimated based on a source-specific and time-varying emission factor database. The results showed that the total PCNs emissions in 2019 reached 757.0 kg with Hebei ranked at the top among all the provinces and iron & steel industry as the biggest source. Low-chlorinated PCNs comprised 90% of emissions by mass, while highly chlorinated PCNs dominated in terms of toxicity, highlighting divergent priorities for mitigating emissions and safeguarding human health. The emissions showed an overall upward trend from 1960 to 2019 driven by emission increase from iron & steel industry in terms of source, and from North China and East China in terms of geographic area. Per-capita emissions followed an inverted U-shaped environmental Kuznets curve while emission intensities decreased with increasing per-capita Gross Domestic Product (GDP) following a nearly linear pattern when log-transformed.

Hair and urinary 2-hydroxynaphthalene levels in the people living in a region with frequent oil pipeline incidents in Iran: Health risk assessment.

Oil spills from pipeline accidents can have long-lasting health effects on residents of polluted regions. Assessing the potential health risk of these accidents is crucial for effective environmental health management. This study analyzed the concentration of 2-OHNAP in urine and hair as biomarkers of PAHs exposure among the people living in a region with frequent oil pipeline incident in Iran. Fifty pairs of hair and urine samples were collected from residents along with demographic information and dietary habits via a questionnaire. The concentration of 2-OHNAP was analyzed using high performance liquid chromatography coupled with fluorescence detector (HPLC-FLD). 2-OHNAP was detected in 100% of urine and 88% of hair samples. The mean concentration of 2-OHNAP in urine was 16.65 ± 21.98 µg/g creatinine and in hair was 8.16±7.62 ng/g dry weight (dw). However, there was no significant correlations between the levels of 2-OHNAP in urine and hair. The mean values of HQ and CR were below 1 and 10-6, respectively. Moreover, some simulated health risk indices were near the threshold levels, and the carcinogenic risk above 70% of the simulated CRs was above 10-6 as well. Therefore, the health risk attributed to the exposure to the parent compound of 2-OHNAP in the study area is currently acceptable, but it is not negligible and may be worsened in the future. This study provides a valuable scientific information for regional decision makers and stakeholders about human health programs and identification of environmental health priorities.

Renal excretion of 1,2-dihydroxynaphthalene (DHN) in firefighting instructors after exposure to polycyclic aromatic hydrocarbons (PAHs) during live fire training.

Exposure of firefighting instructors to polycyclic aromatic hydrocarbons (PAHs) such as naphthalene is unavoidable during live fire training. The study aimed to investigate naphthalene uptake by measuring the urinary excretion of the naphthalene metabolite 1,2-dihydroxynaphthalene (DHN), to describe the DHN elimination kinetics and to evaluate the results by comparison to further biomarkers of PAH exposure. N = 6 male non-smoking firefighting instructors completed five training sessions each in a residential fire simulation unit under respiratory protection. All participants provided two urine samples before and another seven samples within an 18-h-interval after each session. DHN was detected by gas chromatography/tandem mass spectrometry (GC-MS/MS) in all samples (n = 237) with median concentrations ranging from 3.3 µg/g crea. (range 0.9-10.2) before exposure to 134.2 µg/g crea. (43.4-380.4) post exposure. Maximum elimination found 3.3 h (median) after onset of exposure decreased with a mean half-life of 6.6 h to 27.1 µg/g crea. (15.7-139.5) 18 h after training. DHN sensitively indicated a presumed dermal naphthalene intake during training, showing similar elimination kinetics like other naphthalene metabolites. Internal exposure of the participants transiently exceeded exposures determined for non-smokers in the general population, but was lower than at other workplaces with PAH exposure. Despite limited uptake, accumulation is possible with daily exposure.

Characteristics and degradation mechanisms of polychlorinated naphthalenes in surface soil in Yangtze River Delta, China.

Both thermal and environmental processes are significant factors influencing the existing characteristics, e.g., congener distributions, and existing levels, of polychlorinated naphthalenes (PCNs) in the environment. Soil plays an important role in the life cycle of PCNs, but degradation of PCNs in soils has never been reported. In this study, we collected surface soil samples from 13 cities in the Yangtze River Delta, which is one of the most crowded areas of China and analyzed the samples for 75 PCNs. The long-range transportation from polluted areas was the major source for PCNs in remote areas, but the PCN profiles in remote areas reported in our previous studies were different from those in human settlement in this study, indicating there is a transformation of PCNs after emissions from anthropogenic activities. Two experiments were then designed to reveal the degradation mechanisms, including influencing factors, products, and pathways, of PCNs in surface soils. Based on the experiments, we found that the major factor driving the losses of PCNs in surface soils was volatilization, followed by photo irradiation and microbial metabolism. Under photo-irradiation, the PCN structures would be destroyed through a process of dechlorination followed by oxidation. In addition, the dechlorination pathways of PCNs have been established and found to be significantly influenced by the structure-related parameters.

Assessment of polychlorinated naphthalenes in Korean foods: Levels, profiles, and dietary intake.

Concerns about dioxin-like compounds have increased; however, the monitoring of polychlorinated naphthalenes (PCNs) in food and the assessment of dietary intake remain limited. In this study, various foods were collected from Korean markets and analyzed for PCNs. Fishery products exhibited the highest mean concentration (48.0 pg/g ww) and toxic equivalent (TEQ) (0.0185 pg-TEQ/g ww). Agricultural products were the largest contributors (35.7%) to the total dietary intake of PCNTEQ, followed by livestock products (33.6%), fishery products (20.2%), and processed foods (10.5%). The mean intake of PCNTEQ for the Korean population was 0.901 pg-TEQ/day for males and 0.601 pg-TEQ/day for females. Generally, males and younger groups had higher daily intakes of PCNTEQ, but they did not exceed the tolerable weekly intakes. Nonetheless, it is important to manage potential health risks associated with PCNs and other dioxin-like compounds by identifying major food items contributing to PCN exposure and considering age and gender differences.

Determination of genotoxic impurities of aromatic aldehydes in pharmaceutical preparations by high performance liquid chromatography after derivatization with N-Cyclohexyl-4-hydrazino-1,8-naphthalenediimide.

The detection of aromatic aldehydes, considered potential genotoxic impurities, holds significant importance during drug development and production. Current analytical methods necessitate complex pre-treatment processes and exhibit insufficient specificity and sensitivity. This study presents the utilization of naphthalenediimide as a pre-column derivatisation reagent to detect aromatic aldehyde impurities in pharmaceuticals via high-performance liquid chromatography (HPLC). We screened a series of derivatisation reagents through density functional theory (DFT) and investigated the phenomenon of photoinduced electron transfer (PET) for both the derivatisation reagents and the resulting products. Optimal experimental conditions for derivatisation were achieved at 40 °C for 60 min. This approach has been successfully applied to detect residual aromatic aldehyde genotoxic impurities in various pharmaceutical preparations, including 4-Nitrobenzaldehyde, 2-Nitrobenzaldehyde, 1,4-Benzodioxane-6-aldehyde, and 5-Hydroxymethylfurfural. The pre-column derivatisation method significantly enhanced detection sensitivity and reduced the limit of detection (LOD), which ranged from 0.002 to 0.008 µg/ml for the analytes, with relative standard deviations < 3 %. The correlation coefficient (R2) >0.998 demonstrated high quality. In chloramphenicol eye drops, the concentration of 4-Nitrobenzaldehyde was measured to be 8.6 µg/mL below the specified concentration, with recoveries ranging from 90.0 % to 119.2 %. In comparison to existing methods, our work simplifies the pretreatment process, enhances the sensitivity and specificity of the analysis, and offers comprehensive insights into impurity detection in pharmaceutical preparations.

Aromatase (CYP19) gene as a biomarker for detection of naphthalene and phenanthrene in Colombo to Mirissa coastal water in Sri Lanka.

Naphthalene (NAP) and phenanthrene (PHE) are prevalent Polycyclic Aromatic Hydrocarbons (PAHs) in the environment. High-Performance Liquid Chromatography (HPLC) analysis was performed on marine water samples (n = 57) collected from 19 locations. Molecular screening of the aromatase (CYP19) gene expression was examined using quantitative Reverse Transcriptase PCR (qRT-PCR). The findings of the study showed a significant range of naphthalene concentrations along the coastline, spanning from 1.70 to 15.05 mg/L, where phenanthrene concentrations varied from undetectable to a maximum of 5.36 mg/L. The relative expression of the CYP19 gene ranged from 0.5 to 13.9 in the sampling sites. The ANOVA analysis showed a significant positive correlation (p < 0.05) between the concentrations of PAHs and CYP19 gene expression. The study concluded that the CYP19 gene could be useful in detecting contaminants such as naphthalene and phenanthrene in water. This study may help develop effective strategies to detect and mitigate PAH pollution in coastal areas.

Distributions of PCDD/Fs, PCBs, and PCNs in coastal sediments collected from major industrial bays in South Korea.

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs) were assessed in coastal sediments from industrial bays in South Korea to evaluate the pollution levels and their environmental impact. The mean sediment concentrations of Σ17 PCDD/Fs, Σ18 PCBs, and Σ15 PCNs were 198 ± 140, 3427 ± 7037, and 85 ± 336 pg/g dw, respectively. Generally, pollutant concentrations in the inner bay were higher than those in the outer bay, indicating the influence of industrial emissions and harbor activities. The primary sources were identified as steel manufacturing and wastewater treatment plants for PCDD/Fs, harbor and shipbuilding activities for PCBs, and combustion-related sources for PCNs. Notably, PCDD/F concentrations exceeded sediment guideline values. The combined effects of PCDD/Fs and PCBs demonstrated adverse impacts on aquatic organisms. Hence, the release of toxic pollutants into the marine environment could have potential biological effects due to the combined impact of these various compounds.

Risk assessment and predictors of the exposure to polycyclic aromatic hydrocarbons in Spanish adults by urinary human biomonitoring.

Polycyclic aromatic hydrocarbons (PAHs) are produced primarily during incomplete combustion of organic matter and in various industrial processes. They are widespread environmental pollutants that are of significant interest due to their potential toxicity. Humans can be exposed to PAHs through ingestion, inhalation and dermal contact. In the present study, ten urinary PAH biomarkers were determined in first-morning urine samples (n = 504) from the adult population (aged 18-65 years) residing in the Valencian Region of Spain. These samples were analysed using liquid-liquid extraction followed by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). All PAH biomarkers were quantified in more than 65 % of the urine samples. Naphthalene biomarkers, 1-hydroxynaphthalene (1OHNAP) and 2-hydroxynaphthalene (2OHNAP), exhibited the highest levels with geometric means (GMs) of 0.7 and 11.9 µg L-1, respectively. The 95th percentile of all PAH biomarkers ranged from 0.22 to 64.8 µg L-1. Estimated daily intakes (EDIs) for the analysed PAH families in the studied population ranged from 17 (pyrene) to 18581 (naphthalene) ng·kg-bw-1·day-1 (GM). Significant associations were observed between the quantified urinary metabolites of PAHs and smoking status, home location, annual household incomes, BMI, and the consumption of grilled food in the last 24 h. Hazard quotients (HQs) of naphthalene and consequently, hazard indexes (HIs) were above 1, especially for smokers. Therefore, potential health risks associated with PAH exposure in the target population could not be discarded.

Polychlorinated naphthalenes in freshwater fish from Beijing markets: Species-specific differences, effects of cooking, and health risk assessment.

Fish are an important source of human dietary exposure to polychlorinated naphthalenes (PCNs). The occurrence and sources of PCNs in different species of freshwater fish are unknown, and few studies have assessed human exposure risks to PCNs through freshwater fish. In this study, 140 freshwater fish samples from 10 species were collected from Beijing markets, China. The Σ75CNs concentration range in the fish was 20.7-1310 pg/g wet weight (ww). The highest median Σ75PCNs concentration (80.4 pg/g ww) was found in mandarin fish (Siniperca chuatsi), and the lowest (29.6 pg/g ww) in snakehead (Channa argus). Di- and tri-CNs were the dominant PCN homologues with contributions of 35.3 % and 30.8 %, respectively. Unintentionally produced PCNs from metal smelting might be the source of PCN contamination in freshwater fish. The cooking temperature and time did not significantly affect the PCN concentrations in fish or the PCN homologue profiles. The highest toxic equivalent (TEQ) value was observed in sturgeon (Acipenser sinensis), followed by mandarin fish. Hexa-CNs were the most abundant homologue for the PCN TEQs. A risk assessment indicated that the dietary exposure risks for local residents to PCNs through freshwater fish were low. However, the relatively high concentrations of PCNs in the samples deserve attention to avoid PCNs exposure risks for groups with high fish consumption rates. Furthermore, freshwater fish likely contain a mixture of contaminants including dioxin and furans which also display a similar mode of toxicity as the PCNs and could enhance the risk to fish consumers.

Assessing chronic gestational exposure to environmental chemicals in pregnant women: Advancing the co-PBK model.

Vulnerable populations, such as pregnant women and their fetuses, confront potential health risks due to exposure to environmental toxic compounds. Computational methods have been popular in assessing chemical exposure to populations, contrasting with traditional cohort studies for human biomonitoring. This study proposes a screening-level approach based on physiologically based kinetic (PBK) modeling to evaluate the steady-state exposure of pregnant women to environmental chemicals throughout pregnancy. To exemplify the modeling application, naphthalene was chosen. Simulation results indicated that maternal fat exhibited significant bioaccumulation potential, with the log-transformed BTF of naphthalene at 0.51 mg kg-1 per mg d-1 in the steady state. The placenta was primarily exposed to 0.83 mg/d naphthalene for a 75.2 kg pregnant woman, considering all exposure routes. In the fetal structure, single-organ fetal PBK modeling estimated a naphthalene exposure of 123.64 mg/d to the entire fetus, while multiple-organ fetal PBK modeling further revealed the bioaccumulation highest in fat tissue. The liver identified as the vital organ for metabolism, kBioT,LiverM was demonstrated with the highest sensitivity among rate constants in the maternal body. Furthermore, the first-order kinetic rate constants related to the placenta and blood were found to impact the distribution process of naphthalene in the fetus, influencing gestational exposure. In conclusion, urgent attention is needed to develop a computational biomonitoring tool for assessing toxic chemical exposure in vulnerable populations.

A cytotoxicity and mechanistic investigation of mono- and di-chloro naphthalenes.

Polychlorinated naphthalenes (PCNs) were characterized as persistent organic pollutants (POPs) that were widely distributed in the environment. Although the striking in vivo toxicity of these pollutants towards both animals and humans was well documented, their cytotoxicity and mechanism of action have not been extensively investigated. In this study, the in vitro antiproliferative activity of mono- and di-chloronaphthalenes as representative PCNs were evaluated and the results indicated strong growth inhibitory effects against mammalian cells, especially the human breast MCF-10A cell and human hepatic HL-7702 cells. 2-Chloronaphthalene with the most potent antiproliferative effects within the tested PCNs, which showed IC50 values ranging from 0.3 mM to 1.5 mM against selected human cell lines, was investigated for its working mechanisms. It promoted cellular apoptosis of MCF-10A cells upon the concentration of 200 µM. It also induced the autophagy of MCF-10A cells in a dose-dependent manner, resulting in cell death via the interaction of autophagy and apoptosis. Thus, these findings supported the theoretical foundation for interventional treatment of PCNs toxicity and also provided implications for the use of chemopreventive agents against the toxic chlorinated naphthalenes in the environments.

Target Analysis of Polychlorinated Naphthalenes and Nontarget Screening of Organic Chemicals in Bovine Milk, Infant Formula, and Adult Milk Powder by High-Resolution Mass Spectrometry.

Infant formula is intended as an effective substitute for breast milk but is the main source of polychlorinated naphthalenes (PCNs) to nonbreastfed infants. We performed target and nontarget analyses to determine PCNs and identify other organic contaminants in infant formula. The mean PCN concentrations in infant formula, milk powder, and bovine milk were 106.1, 88.8, and 78.2 µg kg-1 of dry weight, respectively. The PCN congener profiles indicated that thermal processes and raw materials were probably the main sources of PCNs in infant formula. A health risk assessment indicated that PCNs in infant formula do not pose health risks to infants. Using gas chromatography-Orbitrap mass spectrometry, 352, 372, and 161 organic chemicals were identified in the infant formula, milk powder, and bovine milk samples, respectively. Phthalate esters were detected in all four plastic-packed milk powder samples. The results indicated milk becomes more contaminated with organic chemicals during manufacturing, processing, and packaging.

[Benchmark dose estimation of polycyclic aromatic hydrocarbons exposure base on Bayesian kernel machine regression].

Objective: To explore benchmark dose (BMD) estimations of polycyclic aromatic hydrocarbons (PAHs) based on Bayesian kernel machine regression (BKMR) . Methods: A total of 155 adult residents of a coking plant in Shanxi Province who were surveyed in summer (June to August) from 2014 to 2019 were selected as the research objects. Fasting elbow vein blood of the subjects was collected in the morning for automatic analysis and detection of blood routine. Morning urine samples were collected for automatic analysis and detection of urine routine and urine creatinine detection. BKMR model combined with BMD method was used to calculate the acceptable doses of PAHs exposure on red blood cell damage in non-occupational population. Results: The concentration of hydroxylpolycyclic aromatic hydrocarbons (OH-PAHs) in the red blood cells abnormal group (n=117) was significantly higher than that in the normal group (n=38) (P<0.01). In the combined effect of OH-PAHs, 2-hydrol-naphthalene contributed the most, and the posterior inclusion probability (PIP) value was 0.9354. When OH-PAHs ≥P(55) concentration, the joint effect on the risk of red blood cell abnormalities increased as the concentration of the OH-PAHs mixture increased. When OH-PAHs were at P(65) and P(75) concentrations, respectively, the risk of red blood cell abnormalities in adults were 3.09 and 4.98 times that of OH-PAHs at P(50) concentrations, respectively. Compared with high concentration, low concentration of OH-PAHs exposure was more sensitive to red blood cell darmage. The acceptable doses of 8 kinds of OH-PAHs were 1.010 µmol/mol Cr (2-hydrol-naphthalene), 0.743 µmol/mol Cr (1-hydrol-naphthalene), 0.901 µmol/mol Cr (2-hydroxy-fluorene) and 0.775 µmol/mol Cr (1-hydroxy-phenanthrene), 0.737 µmol/mol Cr (1-hydroxy-pyrene), 0.607 µmol/mol Cr (9-hydroxy-fluorene), 0.713 µmol/mol Cr (2-hydroxy-phenanthrene) and 0.628 µmol/mol Cr (3-hydroxybenzo[a] pyrene), respectively. Conclusion: OH-PAHs mixture has positive combined effect on red blood cell damage in non-occupational population, and low concentration of OH-PAHs exposure is more sensitive to red blood cell damage. It is recommended that the exposure dose of PAHs should be controlled within 1 µmol/mol Cr.

Co-PBK: a computational biomonitoring tool for assessing chronic internal exposure to chemicals and metabolites.

Toxic chemicals are released into the environment through diverse human activities. An increasing number of chronic diseases are associated with ambient pollution, thus posing a threat to people. Given the high consumption of resources for human biomonitoring, this study proposed coupled physiologically-based kinetic (co-PBK) modeling matrices as a biomonitoring tool for simplifying chronic internal exposure estimates of environmental chemicals and their metabolites using naphthalene (NAP) and its metabolites (i.e., 1-OHN and 2-OHN) as simulation examples. According to the simulation of the steady-state mass among various organs/tissues via the co-PBK modeling matrices, fat had the highest potential bioaccumulation of NAP and its metabolites. With respect to body fluids, 1-OHN and 2-OHN tended to bioaccumulate more in the bile than in the urine. According to the sensitivity analysis, the calculated sensitivity factors for the first-order kinetics-based rate constants imply that due to the biotransformation process, target organs/tissues (e.g., liver and kidneys) would be continuously exposed to more NAP metabolites under chronic exposure. Meanwhile, 1-OHN may be more stably transported to the urine than 2-OHN for further human biomonitoring during long-term internal exposure. According to the case study of simulating population chronic exposure to NAP in Shenzhen, the co-PBK modeling estimated the population exposure to NAP with an intake rate of 8.77 × 10-2 mg d-1 and the aggregated urinary concentration of NAP metabolites of 2.60 µg L-1. Furthermore, the accuracy of the urinary levels between the real-world data and the values simulated by the co-PBK modeling was assessed and the root-mean-square error of c1-OHN,urine was found to be lower than that of c2-OHN,urine.

Biomarkers for polycyclic aromatic hydrocarbons in human excreta: recent advances in analytical techniques-a review.

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants that are generated by the incomplete combustion of organic materials. The main anthropogenic sources of PAHs are the combustion of solid fuels for heating purposes, illegal waste incineration, road transport and industries based on fossil fuels. PAHs can easily enter the body because they are present in all elements of the environment, including water, soil, air, and food. Due to their ubiquitous presence, PAHs, may exert a harmful effect on human health. Assessing PAH exposure through biomonitoring mostly involve techniques to measure the concentration of 1-hydroxypyrene in human urine. Nevertheless, through recent progress in analytical techniques, other common metabolites of PAHs in human biospecimens can be detected. A scientific literature search was conducted to determine which hydroxy derivatives of PAHs are markers of PAHs exposure and to reveal the leading sources of these compounds. Techniques for analyzing biological samples to identify OH-PAHs are also discussed. The most frequently determined OH-PAH in human urine is 1-hydroxypyrene, the concentration of which reaches up to a dozen ng/L in urine. Apart from this compound, the most frequently determined biomarkers were naphthalene and fluorene metabolites. The highest concentrations of 1- and 2-hydroxynaphthalene, as well as 2-hydroxyfluorene, are associated with occupational exposure and reach approximately 30 ng/L in urine. High molecular weight PAH metabolites have been identified in only a few studies. To date, PAH metabolites in feces have been analyzed only in animal models for PAH exposure. The most frequently used analytical method is HPLC-FLD. However, compared to liquid chromatography, the LOD for gas chromatography methods is at least one order of magnitude lower. The hydroxy derivatives naphthalene and fluorene may also serve as indicators of PAH exposure.

Disturbance of OH-PAH metabolites in urine induced by single PAH lab exposure.

Due to the high exposure toxicity and individual variability of polycyclic aromatic hydrocarbons (PAHs), it is difficult to accurately characterize the actual exposure of exposed individuals through external exposure detection. In this study, the monohydroxyl metabolites of naphthalene, phenanthrene, pyrene, and 9-fluorenone were identified in the urine of low-dose PAH-exposed individuals based on ultra-performance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS), and their concentrations were monitored for 15 consecutive days after exposure. The results showed that the metabolite concentrations of naphthalene, phenanthrene, and pyrene were basically the same, and all of them reached the maximum value at day 8. In contrast, the metabolite of 9-fluorenone reached its maximum value on day 2. This study showed that the four metabolites were strongly correlated with their parent PAH exposure, with a wide detection window, and their assays were specific, sensitive, and reliable, while the sampling difficulty was low, so the four hydroxylated PAHs may be potential low-dose biomarkers of PAH internal exposure. This study will provide methodological and data support for further health risk studies involving internal exposure to organic pollutants such as PAHs.

Monitoring microplastic-contaminant sorption processes in real-time using membrane introduction mass spectrometry.

Microplastics are environmentally ubiquitous and their role in the fate and distribution of trace contaminants is of emerging concern. We report the first use of membrane introduction mass spectrometry to directly monitor the rate and extent of microplastic-contaminant sorption. Target contaminant (naphthalene, anthracene, pyrene, and nonylphenol) sorption behaviours were examined at nanomolar concentrations with four plastic types: low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS). Under the conditions employed here, short-term sorption kinetics were assessed using on-line mass spectrometry for up to one hour. Subsequent sorption was followed by periodically measuring contaminant concentrations for up to three weeks. Short-term sorption followed first order kinetics with rate constants that scaled with hydrophobicity for the homologous series of polycyclic aromatic hydrocarbons (PAHs). Sorption rate constants on LDPE for equimolar solutions of naphthalene, anthracene, and pyrene were 0.5, 2.0, and 2.2 h-1, respectively, while nonylphenol did not sorb to pristine plastics over this time period. Similar trends among contaminants were observed for other pristine plastics with 4- to 10-fold faster sorption rates associated with LDPE when compared to PS and PP. Sorption was largely complete after three weeks, with the percent analyte sorbed ranging from 40-100% across various microplastic-contaminant combinations. Photo-oxidative ageing of LDPE had little effect on PAH sorption. However, a marked increase in nonylphenol sorption was consistent with increased hydrogen-bonding interactions. This work provides kinetic insights into surface interactions and describes a powerful experimental platform to directly observe contaminant sorption behaviours in complex samples under a variety of environmentally relevant conditions.

Health risk assessment from exposure to ambient VOCs and particulate matter in different functional zones in Dhanbad, India.

This study evaluates the non-cancer risks (NCR) and cancer risks (CR) in outdoor working personnel in Dhanbad city, exposed to volatile organic compounds (VOCs) and particulate matter (PM) present in the ambient air. Dhanbad is known for its coal mines and is one of the most polluted cities in India and the world. Sampling was conducted in different functional zones; namely, traffic intersections, industrial, and institutional areas, to estimate the concentration of different PM-bound heavy metals and VOCs in the ambient air using Inductively coupled plasma-optical emission spectrometry (ICP-OES) and gas chromatography (GC) respectively. Our results show that the concentration levels (of VOCs and PM) and health risks were maximum at the traffic intersection area, followed by the industrial and institutional areas. The major contribution to CR came from chloroform, naphthalene, and PM-bound chromium, while the contribution to NCR mainly came from naphthalene, trichloroethylene, xylenes, and PM-bound chromium, nickel, and cadmium. It was observed that CR and NCR from VOCs are quite comparable (average CRvoc 8.92E-05 and NCRvoc 6.82) to that from the PM-bound heavy metals (average CRPM 9.93E-05 and NCRPM 3.52). According to the sensitivity analysis performed using Monte-Carlo Simulation, it was also found that the output risk is most significantly influenced by the pollutant concentration followed by exposure duration and exposure time. The study reveals that Dhanbad city is not only a critically polluted area but also a highly hazardous and cancer-prone area due to the pollution arising from incessant coal mining activities and heavy vehicular movement. Given the paucity of data on exposure to VOCs in ambient air and their risk assessment pertaining to coal mining cities of India, our study provides useful information and insight for the regulatory and enforcing authorities to devise appropriate strategies for air pollution and health risk management in such cities.

Air-enclosed pores in graphene aerogel inhibit the adsorption of bisphenol A but accelerate the adsorption of naphthalene.

Graphene hydrogel (GH) and aerogel (GA) have great application potential as highly effective adsorbents, but the accessibility of their adsorption sites have not yet been identified, restricting our understanding on the adsorption mechanisms and manufacturing. This study comparatively studied the adsorption characteristics of bisphenol A (BPA) and naphthalene (NAP) on GH and GA, focussing on the accessibility of the adsorption sites. The adsorption of BPA on GA was much lower but faster than that on GH. NAP adsorption on GA was very close to that on GH but faster than that on the latter. Considering that NAP is volatilisable, we speculate that some unwetted sites in the air-enclosed pores are available to it, but not to BPA. We applied ultrasonic and vacuum treatments to remove the air in GA pores, which was verified using a CO2 replacement experiment. BPA adsorption was greatly enhanced but slowed, while that of NAP was not enhanced. This phenomenon suggested that some inner pores became accessible in the aqueous phase after air removal from pores. The enhanced accessibility of air-enclosed pores was verified by the increased relaxation rate of surface-bounded water on GA, based on a 1H NMR relaxation analysis. This study highlights that the accessibility of adsorption site plays a crucial role for the adsorption properties of carbon-based aerogel. The volatile chemicals may be quickly adsorbed in the air-enclosed pores, which be useful for immobilizing volatile contaminants.