Occurrence, Spatial Distribution, and Bioaccumulation of Dissolved Synthetic Musks in Freshwaters across China

Commercial chemicals, such as synthetic musks, are of global concern, but data on their occurrence and spatial distribution in aquatic environments of large scale are scarce. Two sampling campaigns were conducted in the present study to measure freely dissolved synthetic musks in freshwaters across China using passive samplers, along with biological coexposure at selected sites. Polycyclic musks (PCMs) dominated synthetic musks, with a detection frequency of 95%. Higher concentrations of PCMs were observed in densely populated Mid, East, and South China compared to less populated regions, indicating the significance of anthropogenic activities for synthetic musks in water. The concentration ratios of galaxolide (HHCB)/tonalide (AHTN) were significantly higher in low-latitude areas than in high-latitude areas from June to September, suggesting that solar radiation played an important role in the degradation of HHCB/AHTN. Significant correlations were found between dissolved concentrations of HHCB and AHTN and their lipid-normalized concentrations in coexposed fish and clam. The estimated hazard quotients for HHCB and AHTN in freshwater fish consumed by humans were less than 0.01 at all sampling sites except the Yangtze River Basin. These results help to understand the environmental fate and ecological risks of synthetic musks on a large geographical scale.

Use of machine learning to identify key factors regulating volatilization of semi-volatile organic chemicals from soil to air

Volatilization from soil to air is a key process driving the distribution and fate of semi-volatile organic contaminants. However, quantifying this process and the key environmental governing factors remains difficult. To address this issue, the volatilization fluxes of polybrominated diphenyl ethers (PBDEs) and organophosphate esters (OPEs) from soil were determined in 16 batch experiments orthogonally with six variables (chemical property, soil concentration, air velocity, ambient temperature, soil porosity, and soil moisture) and analyzed with machine learning methods. The results showed that gradient-boosting regression tree models satisfactorily predicted the volatilization fluxes of PBDEs (r2 = 0.82 ± 0.07) and OPEs (r2 = 0.62 ± 0.13). Permutation importance analysis showed that partitioning potential of chemicals between soil and air was the most important factor regulating the volatilization of the target compounds from soil. Temperature and soil porosity played a secondary role in controlling the migration of PBDEs and OPEs, respectively, due to higher volatilization enthalpies of PBDEs than those of OPEs and dominant adsorption of OPEs on mineral surface. The effect of soil moisture was negative and positive for the volatilization fluxes of PBDEs and OPEs, respectively. These results suggested different responses in the soil-air diffusive transport of PBDEs and OPEs to high temperature and rainstorm induced by climate change.

Fluorescent Visualization of Chemical Profiles across the Air-Water Interface

Chemical transfer across the air-water interface is one of the most important geochemical processes of global significance. Quantifying such a process has remained extremely challenging due to the lack of suitable technologies to measure chemical diffusion across the air-water microlayer. Herein, we present a fluorescence optical system capable of visualizing the formation of the air-water microlayer with a spatial resolution of 10 μm and quantifying air-water diffusion fluxes using pyrene as a target chemical. We show for the first time that the air-water microlayer is composed of the surface microlayer in water (∼290 ± 40 μm) and a diffusion layer in air (∼350 ± 40 μm) with 1 μg L-1 of pyrene. The diffusion flux of pyrene across the air-water interface is derived from its high-resolution concentration profile without any pre-emptive assumption, which is 2 orders of magnitude lower than those from the conventional method. This system can be expanded to visualize diffusion dynamics of other fluorescent chemicals across the air-water interface and provides a powerful tool for furthering our understanding of air-water mass transfer of organic chemicals related to their global cycling.

Particle transfer mediates dermal exposure of consumers to plasticizers in eraser and pen accessories

Dermal exposure to chemicals released from daily consumer products is a rising concern, particularly for children who are susceptible to unintentional hand-to-mouth transfer and related chemical exposure risk. However, chemical transfer induced by tiny particles of intact products has yet to be adequately addressed. The objective of the present study was to determine the potentiality of particles release from intact erasers and pen grips upon dermal contact by measuring the migration rates of the embedded plasticizers (phthalates and its alternatives). The results showed that billions of particles were released from erasers (0.6-1.2 × 109) and pen grips (0.2-1.6 × 108) upon dermal contact at ambient temperature, with sizes mainly smaller than 1 μm. The composition of eraser leachates was identical to that of the corresponding bulk eraser, as confirmed by Fourier-transform infrared spectroscopy and pyrolysis. Migrated hydrophobic plasticizers may be used as indicators of particle release from erasers and pen grips. The potentiality of particle release was negatively correlated with the total plasticizer contents (r = -0.51; p < 0.05) for both erasers and pen grips. These findings indicated that particles directly released from school supplies and accessories could be a non-negligible source of human exposure to plasticizers.

Passive-Sampler-Derived PCB and OCP Concentrations in the Waters of the World─First Results from the AQUA-GAPS/MONET Network

Persistent organic pollutants (POPs) are recognized as pollutants of global concern, but so far, information on the trends of legacy POPs in the waters of the world has been missing due to logistical, analytical, and financial reasons. Passive samplers have emerged as an attractive alternative to active water sampling methods as they accumulate POPs, represent time-weighted average concentrations, and can easily be shipped and deployed. As part of the AQUA-GAPS/MONET, passive samplers were deployed at 40 globally distributed sites between 2016 and 2020, for a total of 21 freshwater and 40 marine deployments. Results from silicone passive samplers showed α-hexachlorocyclohexane (HCH) and γ-HCH displaying the greatest concentrations in the northern latitudes/Arctic Ocean, in stark contrast to the more persistent penta (PeCB)- and hexachlorobenzene (HCB), which approached equilibrium across sampling sites. Geospatial patterns of polychlorinated biphenyl (PCB) aqueous concentrations closely matched original estimates of production and use, implying limited global transport. Positive correlations between log-transformed concentrations of Σ₇PCB, ΣDDTs, Σendosulfan, and Σchlordane, but not ΣHCH, and the log of population density (p < 0.05) within 5 and 10 km of the sampling sites also supported limited transport from used sites. These results help to understand the extent of global distribution, and eventually time-trends, of organic pollutants in aquatic systems, such as across freshwaters and oceans. Future deployments will aim to establish time-trends at selected sites while adding to the geographical coverage.

Effects of organic carbon/elemental carbon and particle size on inhalation bioaccessibility of particle-bound PAHs

Bioaccessible fractions of particle-bound hydrophobic organic compounds (HOCs) are critical to evaluating human inhalation exposure risk. However, the key factors for controlling the release of HOCs into the lung fluid are not adequately examined. To address this issue, eight particle size fractions (0.056-18 μm) from different particle emission sources (barbecue and smoking) were collected and incubated with an in vitro method for determining inhalation bioaccessibilities of polycyclic aromatic hydrocarbons (PAHs). The bioaccessible fractions of particle-bound PAHs were 35-65 % for smoke-type charcoal, 24-62 % for smokeless-type charcoal, and 44-96 % for cigarette. The size distributions of bioaccessible fractions of 3-4 ring PAHs were symmetric with the patterns of their masses, characterized as a unimodal distribution with both the trough and peak at 0.56-1.0 μm. Analysis from machine learning showed that chemical hydrophobicity appeared to be the most significant factor affecting inhalation bioaccessibility of PAHs, followed by organic carbon and elemental carbon contents. Particle size seemed to have little effect on the bioaccessibility of PAHs. A compositional analysis of human inhalation exposure risk from total concentration, deposition concentration, and bioaccessible deposition concentration in alveolar region showed a shift in the key particle size from 0.56 to 1.0 μm to 1.0-1.8 μm and an increasing in the contributions of 2-3 ring PAHs to risk for cigarette due to the high bioaccessible fractions. These results suggested the significance of particle deposition efficiency and bioaccessible fractions of HOCs in risk assessment.

Size-resolved gas-particle partitioning characteristics of typical semi-volatile organic compounds in urban atmosphere

Understanding particle size distribution and size-resolved gas-particle partitioning of semi-volatile organic compounds (SVOCs) is important for characterizing their fate in atmosphere. However, the size-resolved gas-particle partitioning characteristics of SVOCs has not been adequately considered. To address this issue, the present study collected gaseous and size-fractioned particulate samples both in and outside of schools, offices, and residences in three districts of different urbanization levels in a megacity, Guangzhou, South China during two seasons. Typical SVOCs, including 15 polycyclic aromatic hydrocarbons (PAHs), six organophosphate esters and seven phthalic acid esters were measured. Emission sources, physicochemical properties, and environmental conditions at the sampling sites considerably impacted the spatiotemporal distribution patterns and particle size distribution of target SVOCs. Not all observed gas-particle partition coefficients (K_p) of target SVOCs were negatively correlated with subcooled liquid-vapor pressures (P_L⁰), probably because certain factors, such as the non-exchangeable part of the particle-bound SVOCs, were not considered in traditional gas-particle partition theories. Particle size was an important factor affecting gas-particle partitioning. Adsorption was the dominant mechanism for PAHs with high molecular weight in different particle modes. A new model was established to predict size-resolved K_p of PAHs with high molecular weight based on P_L⁰ and particle size.

Distribution profiles of bisphenols in school supplies and implications for human exposure

Bisphenol compounds (BPs) are usually applied in the production of school supplies, however, little is known on the occurrence of BPs in school supplies. In this study, 15 BPs were detected in 121 samples of school supplies collected from commercial market. Among all compounds studied, BPA, BPF, and BPS were the dominant compounds in school supplies with the detection frequency of 93.15 %, 85.62 % and 82.53 %, respectively, and at median concentrations of 161, 23.64 and 14.11 ng g^-1 dw. The total concentrations of BPs varied among types of school supplies in the following order: paper (median: 1347 ng g^-1 dw) > fabric (521.4 ng g^-1 dw) > plastic (472.7 ng g^-1 dw) > rubber (352.4 ng g^-1 dw). Risk assessment of BPs in school supplies was evaluated by the estimated daily intake (EDI) via dermal absorption, and the median EDIs of ∑15 BPs were 156.78 ng d^-1 (11.27-37,042.37 ng d^-1) and 432.75 ng d^-1 (32.44-91,624.22 ng d^-1) for general and occupational people, respectively.

Transfer of Frictional Contact Derived Phthalates from Pad Surface Enhances Dermal Exposure

Dermal exposure to chemicals derived from object surface contact is an important contributor to increased health risk. However, chemical transfer induced by mechanical friction between dermal and object surface has yet to be adequately addressed. To fill this knowledge gap, rubbing fabrics were used as surrogate skins to stimulate dermal mechanical friction with pad products with phthalates as target analytes. The results showed that the amounts of phthalates transferred increased linearly with contact burden (50-1000 g), contact duration (1-10 min), and sliding speed (3.0-9.0 cm s^-1). The surface texture of surrogate skins dictated the accumulation of phthalates. Net/pocket micro-surface structures of rubbing fabrics induced a higher accumulation of phthalates than U-shape structures of fabrics with a similar surface roughness. Covering of the pad surface by a layer of textile was effective in minimizing the transfer of phthalates induced by mechanical motion. The estimated transfer efficiency of bis(2-ethylhexyl) ester (DEHP) derived from rubbing friction (0.005-0.05%) upon the pad surface over 8 h was greater than those for gas-phase emission (0.00002-0.0005% over 24 h) and sweat transfer (0.008-0.012% over 24 h). These results indicated that dermal frictional contact with the surface of pad products was an important exposure pathway.

Riverine transport dynamics of PBDEs and OPFRs within a typical e-waste recycling zone: Implications for sink-source interconversion

Despite ample evidence on spreading of e-waste derived hazardous materials, riverine transport of organic contaminants from e-waste recycling zones to surrounding areas has not been evaluated. To address this issue, passive and grab sampling methods were used to assess sediment-water diffusion and horizontal transport of polybrominated diphenyl ethers (PBDEs) and organophosphorus flame retardant (OPFRs) at upstream and downstream sites of two rivers in a typical e-waste recycling zone. Sediment acted as a source of BDE-17 with fluxes of 0.007-0.04 ng m^-2 d^-1 at all sampling sites. BDE-47 and BDE-99 reached equilibrium between overlying water and sediment porewater. Sediment interconverted from a sink at the upstream site to a source of OPFRs at the downstream site with a flux varying between -7.3 and 234 ng m^-2 d^-1. The amounts of OPFRs (11-45 g d^-1) via horizontal riverine transport were greater than those of PBDEs (0.68-2 g d^-1). The vertical sediment-water diffusion of PBDEs and OPFRs was not significant compared to horizontal riverine transport. The annual riverine outputs of PBDEs and OPFRs from the downstream sites were 250-330 g and 12,000-16,500 g, respectively, indicating the significance of riverine transport of organic contaminants from e-waste recycling zones to surrounding areas.

[Two cases of acute chlorfenapyr poisoning and literature review]

In recent years, chlorfenapyr poisoning has gradually increased in clinical practice, but the case fatality rate remains high. At present, the research on its poisoning mechanism and clinical characteristics is limited, and there is no effective treatment. In order to summarize the clinical characteristics of chlorfenapyr poisoning, in order to guide the clinical treatment, this article reported 2 cases of acute chlorfenayr poisoning and 21 cases of literature review, and summarized the clinical characteristics of chlorfenapyr poisoning.Most of the symptoms of gastrointestinal symptoms, profuse sweating, high fever, and changes in consciousness after chlorfenapyr poisoning, and delayed exacerbations are common, which can involve multiple organ systems such as the central nervous system, providing a basis for clinical diagnosis and treatment.

Utility of benzothiazoles as markers of tire-derived inputs to estuarine waters assessed by polyethylene sheets

Tire-derived particles and polyethylene (PE) debris co-exist in estuaries and potentially deteriorate water quality. Chemicals can be emitted from tire-derived particles and resorb to PE debris. However, there was lack of information about the interaction (e.g., sorption and desorption) between tire-derived chemicals and PE debris. By combining batch sorption and desorption experiments along with in situ field deployment of PE sheets, we examined the utility of benzothiazoles (BTZs) sorbed in PE as suitable markers of tire-derived inputs. The sorptive characteristics and PE-water partition coefficients (often designated as K_pew) of selected tire-derived marker candidates, i.e., polycyclic aromatic hydrocarbons (PAHs), benzothiophenes (BTPs) and BTZs, were measured. Moderately polar BTPs and BTZs (except for 2-(4-morpholinyl) benzothiazole) reached equilibrium within 2-8 days, compared to 20 days for nonpolar PAHs. The measure K_pew values and octanol-water partition coefficients of PAHs and BTZs were linearly correlated with each other (r² > 0.80; p < 0.05). The desorption potentiality of PAHs and BTZs from tire particles is consistent with the hydrophilic properties of the target chemicals, while desorption ratios of BTZs and PAHs are 25-87% and <20%, respectively. Samplers with PE sheets as the sorbent phase were deployed in Hailing Bay, an urbanized estuary in South China, to measure concentrations of PAHs, BTPs and BTZs. Benzothiazoles sorbed in PE samples were associated with the massive utilization of automobile tires, while PAHs were linked to the boat maintenance facilities and BTPs were not detected in any tire particle and field PE samples. Therefore sorbed BTZs in PE can potentially serve as chemical markers of tire-derived inputs to estuaries.

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.

Development of an in vitro model to simulate migration of organic contaminants from pad products to human sweat and enhance dermal exposure risk assessment

Dermal sorption is an important route for human exposure to organic chemicals embedded in consumer products, but the related chemical migration from consumer products to sweats was often overlooked in assessing skin exposure risk. To address this issue, the present study selected polycyclic aromatic hydrocarbons (PAHs), phthalic acid esters (PAEs), and benzothiazoles (BTs) as the target compounds and developed an in vitro simulation model with two artificial sweats (i.e., acidic and alkaline), a sorbent, and a PVC standard material. An appropriate biological inhibitor (ampicillin) and incubation time of 20 d for assessing the maximum migration efficiency of chemicals were selected. The mass balance of the target compounds during the in vitro incubation was verified. The established in vitro simulation model was used to determine the migration ratios of PAEs and BTs in three types of mouse pads. The maximum migration ratios of DBP, DIBP, DEHP, and BT from leather pad to both sweats were less than those for silicone and rubber pads. Key controlling parameters in migration ratios should be examined in subsequent investigations. Risk assessment showed that the daily exposure doses of PAEs and BTs in mouse pads were higher than the literature data. The hazard index of PAEs in leather pad exceed 1, indicating that PAEs could induce non-carcinogenic effects to human health through hand contact. Overall, the established in vitro simulation model provides a feasible alternative for assessing the potential risk for dermal exposure to consumer products.

Microplastics on beaches and mangrove sediments along the coast of South China

Accumulation of microplastics (MPs) data on a global scale is key to supporting plastic waste management for protecting ecosystems. To respond this call, a sampling campaign was conducted in the summer and winter seasons of 2018 to collect beach and mangrove sediment samples from 32 sites along the coastline of South China. The MPs concentrations in the intertidal zone along the coast of South China were comparable to those in other regions around the world. Polystyrene foams and fibers were the most abundant debris in the 0.2-5 mm and 0.02-2 mm MPs, respectively. Principal component and correlation analyses indicated that the abundances of MPs were related to wind direction, wastewater discharge amount, and tourist and fishing activities. Risk assessments suggested that potential ecological risks induced by MPs on beaches and mangrove forest along the coast of South China should not be overlooked.

Determination of low-density polyethylene-water partition coefficients for novel halogenated flame retardants with the large volume model and co-solvent model

The partition coefficient (K_pew) of an analyte between low-density polyethylene (LDPE) film and water is a critical parameter for measuring freely dissolved concentrations of the analyte with PE passive sampling devices. Measuring log K_pew for super hydrophobic organic chemicals (HOCs) have been proven extremely difficult. The present study developed a large volume model for measuring log K_pew of super HOCs, i.e., novel halogenated flame retardants (NHFRs). Results showed that the measured log K_pew values of selected PAHs and PCBs obtained by the large volume model were in line with those from the co-solvent model and the literature data within less 0.3 log units of difference, while those of NHFRs (6.27-7.34) except for hexachlorocyclopentadienyldibromocyclooctane (HCDBCO) and Decabromodiphenyl ethane (DBDPE) were significantly lower than those (6.51-8.89) from the co-solvent model. A curvilinear relationship was observed between log K_pew and log K_ow of all target compounds, with the turning point at log K_ow = ∼8.0 in the large volume model, but that was not found for the co-solvent model. These can be attributed to the large molecular volumes (> 450 Å³) for NHFRs, which require high Gibbs free energy to penetrate into the inside structures of LDPE in the large volume model. However, the solvent swelling effects in the co-solvent model needs to be investigated. Therefore, the large volume model is robust to determine the K_pew values of super HOCs for facilitating the application of aquatic passive sampling techniques.

Response of rice (Oryza sativa L.) roots to nanoplastic treatment at seedling stage

Potential adverse effects of nanoplastics (NPs) on marine organisms have received increased attention in recent years. In contrast, few data are available on terrestrial plants, especially on the mechanisms for transport of NPs in plants and phytotoxicity (at both phenotypic and molecular levels) of plants induced by NPs. To address this knowledge gap, we conducted a microcosm study in which hydroponically-cultured rice (Oryza sativa L.) seedlings were exposed to polystyrene (PS)-NPs at 0, 10, 50, and 100 mg L^-1 for 16 d and examined for morphological and physiological phenotypes and transcriptomics. Laser confocal scanning micrographs confirmed PS-NPs were uptaken by rice roots, greatly benefitted from the transport activity of aquaporin in rice roots. The significant enhancement (p < 0.05) of antioxidant enzyme activities reflected the oxidative stress response of rice roots upon exposure to PS-NPs. Treatment by PS-NPs decreased root length and increased lateral root numbers. Carbon metabolism was activated (e.g., increased carbon and soluble sugar contents) whereas jasmonic acid and lignin biosynthesis were inhibited. The present study demonstrated the likelihood for transport of PS-NPs in rice roots and induced phytotoxicity by PS-NPs, which should inspire further investigations into the potential human health risks from rice consumption.

Plastics Are an Insignificant Carrier of Riverine Organic Pollutants to the Coastal Oceans

Global rivers act as a dominant transport pathway for land-based plastic debris to the marine environment. Organic pollutants (OPs) affiliated with riverine plastics can also enter the global oceans, but their amounts remain unknown. Microplastic (MP) samples were collected in a one-year sampling event from the surface water of the eight main riverine outlets in the Pearl River Delta (PRD), China, and analyzed for OPs affiliated with MPs, including 16 polycyclic aromatic hydrocarbons (PAHs), eight polybrominated diphenyl ethers (PBDEs), and 14 polychlorinated biphenyls (PCBs). The mean concentrations of MP-affiliated ∑₁₆PAH, ∑₈PBDE, and ∑₁₄PCB were 2010 (range: 25-40,100), 412 (range: 0.84-14,800), and 67.7 (range: 1.86-456) ng g^-1, respectively. Based on these and previous results, the annual riverine outflows of MP-affiliated OPs were 148, 83, and 8.03 g for ∑₁₆PAH, ∑₈PBDE, and ∑₁₄PCB, respectively. Assuming that plastic debris of different sizes contained the same concentrations of the target pollutants as MPs, the mean riverine outflows of plastic-bound ∑₁₆PAH, ∑₈PBDE, and ∑₁₄PCB were 6.75, 3.77, and 0.37 kg year^-1, respectively, which were insignificant compared with the riverine outflows of OPs through riverine water discharge (up to hundred tons per year). Apparently, plastics are an insignificant carrier of riverine OPs to the coastal oceans.

Effects of cooking on oral bioaccessibility of PBDEs, MeO-PBDEs, and OH-PBDEs in fish (tilapia) and chicken egg

Human health concerns are rising with polybrominated diphenyl ethers' (PBDEs) analogues, methoxylated and hydroxylated PBDEs (MeO-PBDEs and OH-PBDEs), due to their occurrences in foods and greater potential toxicological effects than PBDEs. While the oral bioaccessibilities (BA%) of PBDEs in foods are available, such information on MeO-PBDEs and OH-PBDEs, and the effects of cooking on them have not been adequately addressed. The present study was conducted with fish and chicken egg as typical foods to assess the bioaccessibility (BA%) of PBDEs, MeO-PBDEs, and OH-PBDEs using the colon extended physiologically based extraction test and examine the effects of cooking processes (boiling, frying, and steaming) on them. The results showed that thermal degradation or transformation of the target compounds did not occur during boiling and frying of fish. The BA% of individual PBDEs, MeO-PBDEs, and OH-PBDEs were 20-51% for boiled fish, 11-20% for pan-fried fish, 15-77% for steamed egg, and 42-68% for pan-fried egg. Cooking decreased the BA% of all target compounds in fish due to protein denaturation. However, the BA% of OH-PBDEs in pan-fried egg were greater than those in steamed egg. In addition, the substituent groups of CH₃O- and OH- did not pose any effects on the BA% of BDE-47 in fish, but OH-group decreased its BA% in egg. These findings suggested that MeO-PBDEs and OH-PBDEs exhibited the similar oral BA% in fish to PBDEs, but the underlying mechanism for the effects of cooking on BA% of OH-PBDEs in egg needs to be further investigated.

Selected antibiotics and current-use pesticides in riverine runoff of an urbanized river system in association with anthropogenic stresses

Antibiotics and current-use pesticides are ubiquitous in the environment. It is important to figure out their spatial distribution under the influences of anthropogenic activities and transport from rivers to coastal oceans. To address this knowledge gap, the present study conducted quarterly sampling in eight main runoff outlets of the Pearl River, South China, and obtained total concentrations of antibiotics and current-use pesticides at 24-296 ng L^-1. Higher total concentrations of these chemicals occurred in summer, attributed to seasonal consumption patterns and washout by rainfalls, respectively. The spatial distributions of target analytes were not significantly different between the eastern and western outlets with high and moderate urbanization levels, respectively. Approximately 16.4, 17.7, and 12.5 tons of antibiotics, organophosphorus pesticides, and neonicotinoids were discharged annually from the outlets to the South China Sea. These results suggested that usage amount and hydrology exhibited positive effects on the riverine inputs of the target chemicals. In addition, most target chemicals exhibited low risks to green algae, but erythromycin and parathion posed high ecological risks to aquatic organism (Daphnid and fish).

Global Riverine Plastic Outflows

Global marine plastic pollution, which is derived mainly from the input of vast amounts of land-based plastic waste, has drawn increasing public attention. Riverine plastic outflows estimated using models based on the concept of mismanaged plastic waste (MPW) are substantially greater than reported field measurements. Herein, we formulate a robust model using the Human Development Index (HDI) as the main predictor, and the modeled riverine plastic outflows are calibrated and validated by available field data. A strong correlation is achieved between model estimates and field measurements, with a regression coefficient of r² = 0.9. The model estimates that the global plastic outflows from 1518 main rivers were in the range of 57,000-265,000 (median: 134,000) MT year^-1 in 2018, which were approximately one-tenth of the estimates by MPW-based models. With increased plastic production and human development, the global riverine plastic outflow is projected to peak in 2028 in a modeled trajectory of 2010-2050. The HDI is a better indicator than MPW to estimate global riverine plastic outflows, and plastic pollution can be effectively assessed and contained during human development processes. The much lower global riverine plastic outflows should substantially ease the public's concern about marine plastic pollution and financial pressure for remediation.

Impact of passive sampler protection apparatus on sediment porewater profiles of hydrophobic organic compounds

Passive sampling techniques have been widely used to determine the dissolved concentration profiles of hydrophobic organic compounds (HOCs) in sediment porewater. However, the effects of having a protection for the passive sampler on profiling HOCs concentrations in sediment porewater, especially in deep sediment, have remained unclear. To address this issue, low density polyethylene passive samplers with and without protectors, which consisted of glass fiber filter and porous stainless steel shield, were simultaneously deployed in sediment of the Dongjiang River, South China. The results showed that the protectors retarded the dissipation of performance reference compounds (PRCs) from the sampler by a factor of 2-9. The protectors seemed to exert a negligible effect on the measured concentrations of PAHs, BDE-47, and BDE-99 in surficial sediment porewater (0-14 cm depth) from both samplers. However, the sediment porewater concentration profiles of PAHs and BDE-47 from the sampler with protectors were in agreement with those normalized by dry weight in deep sediment (16-34 cm depth), indicating that a diffusion layer established by the protectors may minimize the probability of local depletion of the target analytes in deep sediment. In addition, the log K_oc values of PAHs, BDE-47, and BDE-99 exhibited a slight increasing trend with sediment depth. This finding suggested that in situ passive sampling techniques could be a feasible tool in determining the site-specific log K_oc values of HOCs at different sediment depths.

Dermal exposure to particle-bound polycyclic aromatic hydrocarbons from barbecue fume as impacted by physicochemical conditions

Inhalation of size-dependent particle-bound polycyclic aromatic hydrocarbons (PAHs) has been extensively studied, whereas dermal absorption has not been adequately investigated. To address this knowledge gap, dermal absorption of size-dependent particle-bound PAHs was characterized through the collection of indoor air and forearm wipe samples in the setting of an indoor barbecue. The mass of size-fractioned PAHs associated with particulate matter was greater in fine particles (<1.8 μm) than in coarse particles (>1.8 μm). Gas-particle distribution of specific PAHs from barbecue fume was ascribed to both adsorption and absorption which would probably be close to equilibrium, while that from background air was dominated by absorption. Forearm-deposited amounts of particulate PAHs suggested that removal of coarse and fine particles could minimize exposure to low and high molecular-weight (MW) PAHs, respectively. Besides, the concentrations of particulate PAHs in forearms wipe were significantly correlated to their dry deposition fluxes with coarse particles, but weakly correlated to those with fine particles. This indicated that particle size would influence dermal absorption efficiency of particle-bound PAHs with fine particles prolonging dermal exposure to PAHs. Overall, higher MW particle-bound PAHs derived from barbecue fume may pose higher risk to human health by dermal absorption than lower MW PAHs.

[Prognosis analysis of 112 cases with Japanese encephalitis in adults]

Objective: To analyze the improvement of clinical symptoms and recovery of neurological function in adult Japanese encephalitis, and study the prognostic factors. Methods: Follow-up was conducted for 112 hospitalized patients with Japanese encephalitis (JE) in adults at the Department of Neurology of three hospitals in Gansu province from July to October 2016, from July to October 2017, 6 months and 1 year after onset, respectively. The neurological functional recovery was evaluated by modified Ranking Scale (mRS).The influencing factors were analyzed by logistic regression model. Results: Among the 112 adult patients with JE after 1year follow-up, 57% (64/112) were completely recovered (mRS score=0), and 14%(16/112) had mild neurological dysfunction (mRS score=1 or 2 points), 20% (22/112) had moderate to severe neurological dysfunction (mRS score 3 to 5), and 9% (10/112) died. In 102 survivors, decreased consciousness were fully recovered (100%), 75% of the mental and behavior disorders, 64% of cognitive/memory impairment, 71% of language function disorder, 61% of paralysis, 73% of extrapyramidal symptoms were fully recovered, and 92% of the seizures were controlled. Comparison of clinical data of initial on-set between good prognosis group (mRS score≤2, 80 cases) and poor prognosis group (mRS score>2, 32 cases) showed that initial clinical manifestation with seizures, consciousness (GCS score), cerebrospinal fluid pressure, and lesion of MRI involved in midbrain had statistically significant differences (all P<0.05) . Multivariate analysis demonstrated that cerebrospinal fluid (CSF) pressure>250 mmH(2)O and lesion of midbrain in MRI were independent risk factors of poor prognosis in adult patients with JE. Conclusion: JE is an acute and infectious viral encephalitis of the central nervous system with high disability and mortality. Most patients were completely recovered, and some had neurological sequelae. CSF pressure>250 mmH(2)O and lesion of midbrain in MRI are independent risk factors for poor prognosis.

Low Tar Level Does Not Reduce Human Exposure to Polycyclic Aromatic Hydrocarbons in Environmental Tobacco Smoke

Environmental tobacco smoke (ETS) is known to pose potential risk to human health, but the effects of tar level remain to be clarified. In the present study, ETS samples from two cigarette types with different tar levels in a 72.5 m3 room were collected for measurement of 16 polycyclic aromatic hydrocarbons (PAHs). Urine samples of volunteers participating in smoking events were collected and analyzed for eight hydroxyl-PAHs. The concentrations, compositions, and particle size distribution patterns of PAHs from higher-tar and lower-tar cigarettes were similar, while the emission factors of PAHs from higher-tar cigarettes were lower than those from lower-tar cigarettes. Furthermore, the change in the concentrations of PAH metabolites in urine samples before and after smoking was not attributed to tar level. Assuming that a single cigarette was smoked in a 100 m3 room, the estimated average inhalation cancer risks for different age groups from exposure to PAHs in ETS were below 1.0 × 10-6, but potential risks should not be overlooked, especially considering that only inhaled particle-bound PAHs in ETS were included in this assessment. Apparently, reduced tar levels would not necessarily lead to lowered risk of exposure to PAHs. Kicking the habit is perhaps the best choice to minimize any potential health risk.

Emissions and Occupational Exposure Risk of Halogenated Flame Retardants from Primitive Recycling of E-Waste

The production and usage of non-polybrominated diphenyl ether (PBDE) halogenated flame retardants (HFRs) have substantially increased after the ban of several PBDEs. This has resulted in widespread environmental occurrence of non-PBDE HFRs, further amplified by emissions from primitive recycling of obsolete electronics (e-waste). The present study conducted chamber experiments to characterize 15 HFRs (∑₁₅HFR) from thermal treatment and open burning of typical e-waste. Emission factors of ∑₁₅HFR from thermal treatment were 2.6 × 10⁴-3.9 × 10⁵ ng g^-1, slightly higher than those from open burning (8.8 × 10³-1.0 × 10⁵ ng g^-1). Greater output over input mass ratios of ∑₁₅HFR were obtained in thermal treatment than in open burning. Particulate and gaseous HFRs dominated the emissions in thermal treatment and open burning, respectively, largely because of the different temperatures used in the two processes. Particulate HFRs were primarily affiliated with fine particles (D_p < 1.8 μm) peaking at 0.56-1.0 or 0.32-0.56 μm in both thermal treatment and open burning. Occupational exposure to most FRs was relatively low, but several PBDEs may pose potential health risk to workers in e-waste home-workshops. Potentially accruing emissions and health risks of non-PBDE HFRs from primitive recycling of e-waste remain a great concern.

Riverine Microplastic Pollution in the Pearl River Delta, China: Are Modeled Estimates Accurate?

Plastic pollution has caused increasing global concern. Currently, model estimates of the riverine plastic inputs to the global oceans based on the concept of Mismanaged Plastic Waste (MPW) varied substantially, and no field measurements of riverine inputs were available. We conducted sampling at the eight major river outlets of the Pearl River Delta, South China with rapid economic growth and urbanization to provide field measured data for fine-tuning modeling results. Floating microplastics (MPs) were collected with a Manta net (mesh size of 0.33 mm) five times during 2018. Microplastic particles (0.3-5.0 mm) widely occurred in all sampling sites. The number and mass concentrations of MPs were in the ranges of 0.005-0.7 particles m^-3 and 0.004-1.28 mg m^-3 and were positively correlated with water discharges. The annual riverine input of MPs from the Pearl River Delta was estimated at 39 billion particles or 66 tons, which converts to 2400-3800 tons of plastic debris based on calculations described in Text S2. These values were substantially below the MPW-based model estimates (91,000-170,000 tons). The large difference between measured and modeling results may have derived from the large uncertainty in the MPW values assigned to the world's countries/regions.

A comprehensive risk assessment of human inhalation exposure to atmospheric halogenated flame retardants and organophosphate esters in an urban zone

Inhalation exposure to flame retardants used as additives to minimize fire risk and plasticizers is ubiquitous in human daily activities, but has not been adequately assessed. To address this research gap, the present study conducted an assessment of human health risk for four age groups through inhalation exposure to size fractionated particle-bound and gaseous halogenated flame retardants (polybrominated diphenyl ethers (PBDEs) and alternative halogenated flame retardants (AHFRs)) and organophosphate esters (OPEs) at indoor and outdoor environments (school, office, and residence) in three districts of a megacity (Guangzhou, China). Results demonstrated that OPEs were the dominant components among all targets. Indoor daily intakes of PBDEs and OPEs were 13-16 times greater than outdoor levels for all age groups. Gaseous OPEs contributed significantly greater than particle-bound compounds to daily intakes of all target compounds. Based on the different life scenarios, hazard quotient (HQ) and incremental life cancer risk (ILCR) from adults exposure to PBDEs and OPEs in indoor and outdoor settings were the greatest, followed by adolescents, children, and seniors. The estimated HQ and ILCR for all age groups both indoors and outdoors were lower than the safe level (HQ = 1 and ILCR = 10^-6), indicating that the potential health risk for local residents in Guangzhou via inhalation exposure to atmospheric halogenated flame retardants and OPEs was low.

Impacts of texture properties and airborne particles on accumulation of tobacco-derived chemicals in fabrics

Vapor-phase constituents of tobacco smoke are known to accumulate on clothing surfaces; however, the significance of texture properties, such as specific surface area, porosity, and surface roughness, and airborne particles to the sorption capacity of fabrics has not been adequately addressed. In the present study, cotton (t-shirt) and polyester (pajama and lab coat) fabrics were exposed to cigarette smoke containing gaseous and particulate tobacco-derived compounds (e.g., N-nitrosamines). Fabric-air distribution coefficients and particle deposition fluxes were then determined to evaluate the accumulation of the target analytes. Appreciable amounts of N'-nitrosoanabasine (NAB) and 4'-(nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK) were detected in all three fabric types although particle-bound NAB and NNK were found only in cigarette smoke. In addition, the root mean square surface roughness heights for three types of clothes were within the same order of magnitude. As such, the deposition fluxes of particle-bound N'-nitrosonornicotine (NNN) and NNK to fabric surface may have contributed to 6-20% and 56-100% of total NNN and NNK in fabrics, respectively, estimated based on the assumed deposition velocity of 0.65 m h^-1. Apparently, the sorption capacity of fabrics can be greatly influenced by particle-bound compounds on clothing surfaces, resulting in either over- or under-estimation of fabric-air distribution/partitioning coefficients.

Organophosphate flame retardants emitted from thermal treatment and open burning of e-waste

Organophosphate flame retardants (OPFRs) have been increasingly produced and consumed since the gradual phase-out of polybrominated diphenyl ethers. Primitive recycling of e-waste can be a significant input source of OPFRs to the environment. Thermal treatment and open burning of typical e-wastes were conducted in a closed chamber to examine the emissions and the size distribution patterns of particle-bound OPFRs from these processes. The sum emission factors of OPFRs were 3.70 × 10⁴-3.65 × 10⁵ ng g^-1 by thermal treatment and 5.22 × 10³-9.27 × 10⁴ ng g^-1 by open burning. The output-input mass ratios of OPFRs for plastic casings were 0.030-116 and 0.012-7.1 by thermal treatment and open burning, respectively, and were 0.11-40 and 0.0014-6.7 for printed circuit boards. The size distribution patterns of OPFRs were characterized by one unimodal peak (0.56-1.0 μm) for thermal treatment and bimodal peaks (0.56-1.0 or 1.0-1.8 and 10-18 μm) for open burning. Particle-bound OPFRs appeared to form in affiliation with particles rather than by adsorption or deposition from the gaseous phase to particulate organic matter. With increasing amounts of OPFRs used in a variety of consumer products, the emissions of OPFRs to the environment are expected to increase continuously in the future.

Characterizing PBDEs in fish, poultry, and pig feeds manufactured in China

A total of 53 feeds from 23 brands for four types of animals, i.e., fish, chicken, duck, and pig, as well as six types of raw materials, were bought from Guangxi, Hubei, Anhui, and Guangdong provinces in China and analyzed for polybrominated diphenyl ethers (PBDEs). The raw materials including super fish meal, ordinary fish meal, poultry ore, soybean, stone powder, and rapeseed were selected because they were added to all the animal feeds manufactured. The occurrence of PBDEs was ubiquitous in the feeds and raw materials, with BDE-209 as the most abundant congener. The average concentration of ∑₈PBDE was 1.1 and 0.44 ng g^-1 dry weight in feeds (range 0.25-5.7) and raw materials (range 0.27-0.84), respectively. No statistically significant differences in ∑₈PBDE concentrations were observed among the four groups of animal feeds. Feeds from Yangzhiyuan Brand (n = 11) contained statistically (p < 0.01) lower ∑₈PBDE concentrations than all other brands except for Baoshun Brand. Chicken was selected as a representative animal to assess health risk for human exposure to PBDEs via the consumption of chicken raised by the feeds under investigation. Hazard quotients based on per-capita consumption of chicken were all below 1, indicating low potential risk to humans consuming chicken raised with the feeds. Graphical abstract.

In vitro inhalation bioaccessibility for particle-bound hydrophobic organic chemicals: Method development, effects of particle size and hydrophobicity, and risk assessment

Bioaccessibility of particle-bound hydrophobic organic contaminants and related particle size effects are significant for assessing the potential human health risk via inhalation exposure, but have not been clearly evaluated. To fill this knowledge gap, the present study developed an in vitro method to estimate the inhalation bioaccessibility of particulate polycyclic aromatic hydrocarbons (PAHs) using simulated human lung fluids, i.e., a modified Gamble's solution (MGS) and artificial lysosomal fluid (ALF) with Tenax as the absorption media. Assay parameters, namely incubation time (10 d) and influence of filter use, were optimized for establishing the in vitro method. The results showed that the bioaccessibility of PAHs increased with increasing particle size, but other factors, such as total organic carbon and chemical hydrophobicity, also played a large role in the fate of these compounds. The results from this portion of the present study were then used to evaluate human health risk, which showed that the risk of these particle-bound PAHs by incorporating size-dependent PAHs bioaccessibility and deposition efficiency in the human respiratory tract into inhalation exposure risk calculations was reduced by >90% when compared to using total concentration. This suggested that the inhalation bioaccessibility and deposition efficiency of hydrophobic organic chemicals should be included in human health risk assessment.

Size distribution and clothing-air partitioning of polycyclic aromatic hydrocarbons generated by barbecue

Barbecue (BBQ) is one of the most popular cooking activities with charcoal worldwide and produces abundant polycyclic aromatic hydrocarbons (PAHs) and particulate matter. Size distribution and clothing-air partitioning of particle-bound PAHs are significant for assessing potential health hazards to humans due to exposure to BBQ fumes, but have not been examined adequately. To address this issue, particle and gaseous samples were collected at 2-m and 10-m distances from a cluster of four BBQ stoves. Personal samplers and cotton clothes were carried by volunteers sitting near the BBQ stoves. Particle-bound PAHs (especially 4-6 rings) derived from BBQ fumes were mostly affiliated with fine particles in the size range of 0.18-1.8 μm. High molecular-weight PAHs were mostly unimodal peaking in fine particles and consequently had small geometric mean diameters and standard deviations. Source diagnostics indicated that particle-bound PAHs in BBQ fumes were generated primarily by combustion of charcoal, fat content in food, and oil. The influences of BBQ fumes on the occurrence of particle-bound PAHs decreased with increasing distance from BBQ stoves, due to increased impacts of ambient sources, especially by petrogenic sources and to a lesser extent by wind speed and direction. Octanol-air and clothing-air partition coefficients of PAHs obtained from personal air samples were significantly correlated to each other. High molecular-weight PAHs had higher area-normalized clothing-air partition coefficients in cotton clothes, i.e., cotton fabrics may be a significant reservoir of higher molecular-weight PAHs.

CAPSULE

Particle-bound PAHs from barbecue fumes are generated largely from charcoal combustion and food-charred emissions and mainly affiliated with fine particles.

Polycyclic aromatic hydrocarbons affiliated with microplastics in surface waters of Bohai and Huanghai Seas, China

Microplastics (MPs) sized between 0.33 and 5 mm were collected using Manta trawls from ten surface seawater sites in Bohai and Huanghai Seas, China. A total of 1024 (Bohai Sea) and 132 (Huanghai Sea) microplastic pieces were classified, including polystyrene foams, polyethylene films and lines, and other plastic pellets, with concentrations of MPs ranging from 3 to 162 particles per 100 m³ (0.012-2.96 mg m^-3). A pretreatment of MPs with 30% H₂O₂ in water did not significantly lower polycyclic aromatic hydrocarbon (PAH) concentrations on MPs compared to no H₂O₂ pretreatment. Measurements of PAHs carried on the collected MPs indicated that the concentrations of the sum of 16 PAHs were in the range of 3400-119,000 ng g^-1. The sources of PAHs in Bohai and Huanghai Seas were highly similar, with petroleum and gasoline probably as the dominant sources. The present study shows the relative importance of MPs in regards to chemical transport in the marine environment. The combination of high concentrations of PAHs affiliated with MPs and the increasing magnitude of plastic pollution in the world's oceans demonstrates the considerable importance of MPs to the fate of PAHs in marine environments.

Characteristics and potential health risk of rural Tibetans' exposure to polycyclic aromatic hydrocarbons during summer period

Biomass fuels remain main energy sources in many remote rural regions, but potential health hazards from exposure to biomass combustion fumes have not been adequately assessed. Combustion of biomass fuels generates abundant polycyclic aromatic hydrocarbons (PAHs); hence residential exposure to PAHs can be used to evaluate the potential health risk to remote rural populations. The present study selected rural Tibetans to address the above-mentioned issue. Samples of indoor air and dust, human urine and local foods (Tsampa flour and buttered tea) were collected from five rural households in Langkazi County, an agricultural and pasturing region in Tibet of China in the summer season, which represented the best-case scenario as no heating was required. Residential exposure to PAHs by adults amounted to benzo[a]pyrene equivalent (BaP_eq) dosages of 110-760, 1.2-50 and 0.5-23 ng d^-1 for ingestion, inhalation and dermal contact, respectively. Daily intakes of naphthalene, fluorene, phenanthrene and pyrene estimated from urinary monohydroxy PAH metabolites and from diet and inhalation exposure to PAHs were comparable (3.9, 1.9, 12 and 3.3 μg d^-1 versus 9.5, 2.5, 5.1 and 1.1 μg d^-1), indicating the utility of external exposure in assessing daily intake of PAHs. The median incremental lifetime cancer risk was 32 × 10^-6 (95% confidence interval: 0.7-73 × 10^-6) for ingestion and 2.4 × 10^-6 (95% confidence interval: 0.02-12 × 10^-6) for inhalation and dermal contact combined, indicating moderate to slight potential cancer risk. Diet is the dominant source of health hazards for rural Tibetans, but cooking fumes also present a meaningful concern. The present study demonstrates that the pristine lifestyles of remote rural residents may be of global health concern, and merit further investigations.

Importance of Dermal Absorption of Polycyclic Aromatic Hydrocarbons Derived from Barbecue Fumes

Despite the ubiquity and carcinogenicity of polycyclic aromatic hydrocarbons (PAHs), their dermal absorption for the general population has not been adequately addressed. Aiming to verify the importance of dermal absorption of PAHs, barbecue (BBQ) in Guangzhou, China was chosen as a case study. Urine samples were collected and analyzed for nine hydroxyl (OH)-PAHs. Air, food, and cotton clothing samples were analyzed for 16 PAHs. Dietary exposure was the dominant exposure route with the greatest amounts of OH-PAH excretion and PAH intake. Dermal intake of low molecular-weight PAHs was greater than inhalation intake from the occurrence of atmospheric PAHs. In addition, the net excreted amounts of OH-naphthalene, OH-fluorene, OH-phenanthrene, and OH-pyrene via dermal absorption were 367, 63, 98, and 28 ng, respectively, upon 2.5-h exposure, comparable to those via combined dermal and inhalation exposure, which were 453, 98, 126, and 38 ng. The ratios of excretion to intake via dermal absorption were 0.11, 0.036, and 0.043 for fluorene, phenanthrene, and pyrene, respectively, lower than the ratios from dietary exposure (0.38, 0.14, and 0.060) but higher than the ratios from inhalation (0.097, 0.016, and 0.025). In the case of BBQ fumes, dermal absorption was a more important pathway for intake of low molecular-weight PAHs than inhalation.

Assessment of airborne polycyclic aromatic hydrocarbons in a megacity of South China: Spatiotemporal variability, indoor-outdoor interplay and potential human health risk

Although a number of studies have assessed the occurrence of atmospheric polycyclic aromatic hydrocarbons (PAHs) in indoor environment, few studies have systemically examined the indoor-outdoor interplay of size-dependent particulate PAHs and potential health risk based on daily lifestyles. In the present study, size-dependent particle and gaseous samples were collected both indoors and outdoors within selected schools, offices and residences located in three districts of Guangzhou, China with different urbanization levels during the dry and wet weather seasons. Results from measurements of PAHs showed that higher total PAH concentrations occurred in residential areas than in other settings and in indoor than in outdoor environments. Compositional profiles and size distribution patterns of particle-bound PAHs were similar indoors and outdoors, predominated by 4-and 5-ring PAHs and the 0.56-1.0 μm particle fraction. Statistical analyses indicated that outdoor sources may have contributed to 38-99% and 62-100% of the variations for indoor particle-bound and gaseous PAH concentrations, respectively. Incremental life cancer risk (ILCR) from human exposure to indoor and outdoor PAHs based on different lifestyles followed the order of adults > children > adolescents > seniors. All average ILCR values for four age groups were below the lower limit of the Safe Acceptable Range (10^-6). In addition, the ILCR value for adults (average: 7.2 × 10^-7; 95% CI: 5.4 × 10^-8‒2.5 × 10^-6), estimated from outdoor air PAH levels with 24-h exposure time, was significantly higher than our assessment results (average: 5.9 × 10^-7; 95% CI: 6.3 × 10^-8‒1.9 × 10^-6), suggesting the significance of assessing human inhalation exposure risks of indoor and outdoor PAHs in urban air based on daily lifestyles.

Characteristics of Polybrominated Diphenyl Ethers Released from Thermal Treatment and Open Burning of E-Waste

Primitive processing of e-waste potentially releases abundant organic contaminants to the environment, but the magnitudes and mechanisms remain to be adequately addressed. We conducted thermal treatment and open burning of typical e-wastes, that is, plastics and printed circuit boards. Emission factors of the sum of 39 polybrominated diphenyl ethers (∑₃₉PBDE) were 817-1.60 × 10⁵ ng g^-1 in thermal treatment and nondetected-9.14 × 10⁴ ng g^-1, in open burning. Airborne particles (87%) were the main carriers of PBDEs, followed by residual ashes (13%) and gaseous constituents (0.3%), in thermal treatment, while they were 30%, 43% and 27% in open burning. The output-input mass ratios of ∑₃₉PBDE were 0.12-3.76 in thermal treatment and 0-0.16 in open burning. All PBDEs were largely affiliated with fine particles, with geometric mean diameters at 0.61-0.83 μm in thermal degradation and 0.57-1.16 μm in open burning from plastic casings, and 0.44-0.56 and nondetected- 0.55 μm, from printed circuit boards. Evaporation and reabsorption may be the main emission mechanisms for lightly brominated BDEs, but heavily brominated BDEs tend to affiliate with particles from heating or combustion. The different size distributions of particulate PBDEs in emission sources and adjacent air implicated a noteworthy redisposition process during atmospheric dispersal.

[Spatial Distribution of DDTs and PCBs in Wild Fish from Hong Kong Coastal Areas and Potential Human Health Risk Assessment]

To examine the distributional patterns of persistent organic pollutants in the wild fish of Hong Kong and assess the health risks associated with consuming them, two typical kinds of persistent organic pollutants, such as dichlorodiphenyltrichloroethane (DDTs) and polychlorinated biphenyls (PCBs), were determined in 31 kinds of fishes caught from the coastal areas of Hong Kong. The results indicate that the concentrations of DDTs and PCBs in the wild fishes were in the ranges of 0.44-17 ng·g^-1 and 0.028-6.3 ng·g^-1, respectively, which were at the low end of the global ranges. Spatially, the lowest concentrations of DDTs and PCBs were found in the fishes occurring in the west of Lantau Island and Tolo Harbor. Furthermore, the feeding habits and living environments of the fishes could have some influence on the accumulation of DDTs and PCBs in them. Source diagnostics indicated that DDTs in these fishes mainly originated from historical residues, but the fishes which migrate for relatively longer distances may be subject to DDT contamination in the estuaries. Finally, human health risk assessments suggested that the increased potential lifetime cancer risk of local adolescences and adults exposed to DDTs and PCBs via wild fish consumption was high. Therefore, the local residents in Hong Kong should reduce their daily intake of wild fish caught from the surrounding coastal regions.

A review of methods for measuring microplastics in aquatic environments

An increasing number of reports have been published concerning microplastic (MP) pollution in aquatic environments. Methods used in these studies continue to be updated and lack standardization, so that an up-to-date review pertaining methods for MP research is needed. This critical review examines the analytical methods, including sampling, identification, and quantitation, for MP research. Samples are generally collected from water, sediment, and biota gastrointestinal tract. Manta nets or trawls are prevalently used in surface water sampling, while direct shoveling or box-corer grab are commonly applied in sediment sampling. Microplastics in biota are generally obtained by dissecting organisms and separating livers, gills, and guts. Density separation is frequently chosen to separate MPs from sample matrices. Chemical digestion can dissolve other organic materials and isolate MPs for further identification. Visual sorting should be combined with chemical composition analysis to better identify the polymer type. Pyrolysis or thermal decomposition gas chromatography coupled with mass spectrometry, Fourier transform infrared spectroscopy, and Raman spectroscopy are currently the main technologies for MP identification. Units prevalently used to express MP abundance in water, sediment, and biota are "particles per m³," "particles per m²," and "particles per individual," respectively. As MP abundances often varied with the methods used, we recommend that analytical protocols of MPs should better be standardized and optimized. Despite the important progress in analysis of MPs, detection technologies for identifying nano-sized plastic particles are still lacking, and therefore should be developed swiftly.

Intake, distribution, and metabolism of decabromodiphenyl ether and its main metabolites in chickens and implications for human dietary exposure

Diet is considered as the most important human exposure pathway for polybrominated diphenyl ethers (PBDEs). Metabolism and accumulation patterns of PBDEs in different growth periods of chickens are helpful for evaluating human dietary exposure, but such information is scarce. In this study, female chickens were fed with food spiked with BDE-209 at 85 mg kg^-1, and the intake, accumulation, and excretion of BDE-209 and its main metabolites in various tissues were examined. Concentrations of BDE-209 in chicken tissues increased over time in a tissue-specific manner; they were the greatest in liver and generally the lowest in breast meat during the entire exposure period. The kinetic patterns were dependent on both growth-dilution effects and accumulated concentrations of BDE-209. Tissue concentrations of ∑₈PBDE (sum of BDE-28, 47, 99, 100, 153, 154, 183, and 209) followed the sequence of liver > blood > skin > intestine > stomach > leg meat > breast meat. Different tissue partition coefficients and perfusion rates for blood may have resulted in different PBDE concentrations in tissues. The absorption efficiency of BDE-209 in chicken tissues followed the sequence of liver (0.15 ± 0.032%) > skin (0.14 ± 0.038%) > intestine (0.071 ± 0.021%) > breast meat (0.062 ± 0.020%) > leg meat (0.059 ± 0.016%) > stomach (0.021 ± 0.0095%), likely due in part to facilitated absorption of BDE-209 by transport proteins (P-glycoproteins). On average, 9.3 ± 1.7% of BDE-209 was excreted in feces. Estimated human average dietary intake via the consumption of chicken tissues of ∑₈PBDE for adults and children was 319 and 1380 ng day^-1 for liver, 211 and 632 ng day^-1 for leg meat, and 104 and 311 ng day^-1 for breast meat from the contaminated group. Liver clearly poses the highest exposure risk for human consumption, particularly if chickens are fed with contaminated feed.

Absorption, tissue distribution, metabolism, and elimination of decabrominated diphenyl ether (BDE-209) in rats after multi-dose oral exposure

Human and ecological risks of BDE-209 have drawn much attention, particularly with growing e-waste recycling activities in developing countries. To further address the issue of BDE-209 biotransformation, a laboratory-controlled study was conducted. Female Sprague-Dawley rats were dosed orally by gavage at a daily dose of 1 mg kg^-1 body weight for 7 d and a depuration period of 22 d, to characterize absorption, distribution, metabolism, and elimination dynamics of BDE-209 during multi-dose exposures simulating short-term oral exposure of e-waste workers. The concentrations of BDE-209 in all tissues increased exponentially during the 7-d exposure period, indicating that multi-dose exposure could lead to increased accumulation of BDE-209 in rats. The liver accumulated the greatest amount of BDE-209 on a wet-weight basis, while adipose tissue had the highest concentration by the end of the 22-d depuration period. Half-lives of BDE-209, 207, and 197 during depuration were 1.1 ± 0.1, 2.7 ± 0.3, and 10.5 ± 3.1 d in serum and 0.9 ± 0.1, 2.2 ± 0.2, and 11.8 ± 2.3 d in liver, i.e., the half-life increased with decreasing level of bromination from deca- to octa-BDEs and was similar in both serum and liver. By contrast, the half-life of the debromination metabolite BDE-207 (21.7 ± 7.7 d) was longer in small intestine than in serum and liver, suggesting slower depletion of BDE-209 metabolites in small intestine. The metabolism of BDE-209 was not responsible for the occurrence of low brominated BDE congeners and OH and MeO-PBDEs in human tissues.

Impact of Polymer Colonization on the Fate of Organic Contaminants in Sediment

Plastic pellets and microbes are important constitutes in sediment, but the significance of microbes colonizing on plastic pellets to the environmental fate and transport of organic contaminants has not been adequately recognized and assessed. To address this issue, low-density polyethylene (LDPE), polyoxymethylene (POM) and polypropylene (PP) slices were preloaded with dichlorodiphenyltrichloroethanes (DDTs), polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) and incubated in abiotic and biotic sediment microcosms. Images from scanning electron microscope, Lysogeny Broth agar plates and confocal laser scanning microscope indicated that all polymer slices incubated in biotic sediments were colonized by microorganisms, particularly the LDPE slices. The occurrence of biofilms induced higher dissipation rates of DDTs and PAHs from the LDPE slice surfaces incubated in the biotic sediments than in the abiotic sediments. Plastic colonization on LDPE slice surfaces enhanced the biotransformation of DDT and some PAHs in both marine and river sediments, but had little impact on PCBs. By comparison, PP and POM with unique properties were shown to exert different impacts on the physical and microbial activities as compared to LDPE. These results clearly demonstrated that the significance of polymer surface affiliated microbes to the environmental fate and behavior of organic contaminants should be recognized.

Significance of Anthropogenic Factors to Freely Dissolved Polycyclic Aromatic Hydrocarbons in Freshwater of China

Assessment of surface water pollution by organic pollutants is a top priority in many parts of the world, as it provides critical information for implementing effective measures to ensure drinking water safety. This is particularly important in China, where insufficient data of national scale have been acquired on the occurrence of any organic pollutants in the country's water bodies. To fill the knowledge gap, we employed passive samplers to survey polycyclic aromatic hydrocarbons (PAHs) in 42 freshwaters throughout the country. The dissolved Σ₂₄PAH concentrations ranged from 0.28 to 538 ng L^-1, with the highest and lowest values obtained in Southern Lake in Wuhan and in the Nam Co Lake in Tibet, respectively. Average Σ₂₄PAH concentrations in West, Central, and East China correlated well with the population densities in these regions. The composition profiles of PAHs showed a mixed PAH source of coal combustion, fossil fuel combustion, and oil spills. In addition, all dissolved PAH concentrations were below the water guidelines developed by the U.S. Environmental Protection Agency, the European Union, and the Canadian government, except for anthracene in Southern Lake. Our results also demonstrated the feasibility of establishing a global network of monitoring organic pollutants in the aquatic environment with passive sampling techniques.

Significance of Cooking Oil to Bioaccessibility of Dichlorodiphenyltrichloroethanes (DDTs) and Polybrominated Diphenyl Ethers (PBDEs) in Raw and Cooked Fish: Implications for Human Health Risk

The present study examined the bioacessibility of DDTs and PBDEs in cooked fish (yellow grouper; Epinephelus awoara) with and without heating using the colon extended physiologically based extraction test. The bioaccessibility of DDTs and PBDEs increased from 60 and 26% in raw fish to 83 and 63%, respectively, after the addition of oil to raw fish. However, they decreased from 83 to 66% and from 63 to 40%, respectively, when oil-added fish were cooked. Human health risk assessment based on bioaccessible concentrations of DDTs and PBDEs in fish showed that the maximum allowable daily fish consumption rates decreased from 25, 59, and 86 g day^-1 to 22, 53, and 77 g day^-1 for children, youths, and adults, respectively, after fish were cooked with oil. These findings indicated that the significance of cooking oil to the bioaccessibility of DDTs and PBDEs in food should be considered in assessments of human health risk.

Evaluating the effectiveness of pollution control measures via the occurrence of DDTs and HCHs in wet deposition of an urban center, China

Wet deposition is not only a mechanism for removing atmospheric pollutants, but also a process which reflects loadings of atmospheric pollutants. Our previous study on wet deposition examined the effectiveness of short-term control measures on atmospheric particulate pollution, which were partly effective for organic pollutants of current input sources. In the present study, dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs), representative of legacy contaminants, were measured in the same samples collected throughout the entire year of 2010 in Guangzhou, a large urban center in South China. Concentrations of ∑DDT (sum of o,p' and p,p'-DDT, o,p' and p,p'-DDE, o,p' and p,p'-DDD, and p,p'-DDMU) and ∑HCH (sum of α-, β-, γ-, and δ-HCH) in wet deposition were in the ranges of nd-69 (average: 1.8 ng L^-1) and nd-150 ng L^-1 (average: 5.1 ng L^-1), respectively. In addition, the results of source diagnostics and backward air mass trajectories appeared to suggest the transport of antifouling paint derived DDTs from the coastal region off South China to Guangzhou. The combined wet and dry deposition flux of ∑HCH in the first quarter (January to March) was greater than that in the fourth quarter (October to December), while those of ∑DDT were comparable in the first and fourth quarters. Similar trends were also observed for the concentrations of ∑HCH and ∑DDT in aerosol samples. These results suggested the short-term pollution control measures implemented during the 16th Asian Games and 10th Asian Para Games (held in November and December 2010, respectively) did not work well for DDTs. The reduced input of HCHs during the fourth quarter was probably associated with the strict ban on lindane for food safety, which also exposed the weakness of control measures focusing mainly on the removal of atmospheric particulate matter.

Aquatic Global Passive Sampling (AQUA-GAPS) Revisited: First Steps toward a Network of Networks for Monitoring Organic Contaminants in the Aquatic Environment

Organic contaminants, in particular persistent organic pollutants (POPs), adversely affect water quality and aquatic food webs across the globe. As of now, there is no globally consistent information available on concentrations of dissolved POPs in water bodies. The advance of passive sampling techniques has made it possible to establish a global monitoring program for these compounds in the waters of the world, which we call the Aquatic Global Passive Sampling (AQUA-GAPS) network. A recent expert meeting discussed the background, motivations, and strategic approaches of AQUA-GAPS, and its implementation as a network of networks for monitoring organic contaminants (e.g., POPs and others contaminants of concern). Initially, AQUA-GAPS will demonstrate its operating principle via two proof-of-concept studies focused on the detection of legacy and emerging POPs in freshwater and coastal marine sites using both polyethylene and silicone passive samplers. AQUA-GAPS is set up as a decentralized network, which is open to other participants from around the world to participate in deployments and to initiate new studies. In particular, participants are sought to initiate deployments and studies investigating the presence of legacy and emerging POPs in Africa, Central, and South America.

Examination of factors dominating the sediment-water diffusion flux of DDT-related compounds measured by passive sampling in an urbanized estuarine bay

The fate of hydrophobic organic compounds in aquatic environment are largely determined by their exchange at sediment-water interface, which is highly dynamic and subject to rapidly evolving environmental conditions. In turn, environmental conditions may be governed by both physicochemical parameters and anthropogenic events. To examine the importance of various impact factors, passive sampling devices were deployed at the seafloor of Hailing Bay, an urbanized estuarine bay in Guangdong Province of South China to measure the sediment-water diffusion fluxes of several metabolites of dichlorodiphenyltrichloroethane (DDT), p,p'-DDE, p,p'-DDD and o,p'-DDD. The physicochemical properties of water (temperature, pH, salinity and dissolved oxygen) and surface sediment (sediment organic matter, physical composition, pH, water content, colony forming unit and catalase activity) were also measured. The results showed that the diffusion fluxes of o,p'-DDD, p,p'-DDD and p,p'-DDE at sites A1 and A2 near a fishing boat maintenance facility ranged from 0.42 to 4.73 ng m^-2 d^-1 (from sediment to overlying water), whereas those at offshore sites varied between -0.03 and -3.02 ng m^-2 d^-1 (from overlying water to sediment), implicating A1 and A2 as the sources of the target compounds. The distribution patterns of the diffusion fluxes of the target compounds were different from those of water and sediment parameters (water temperature, salinity, sediment texture, pH, colony forming unit and catalase activity) at six sampling sites. This finding suggested that none of these parameters were critical in dictating the sediment-water diffusion fluxes. Besides, decreases in the contents of kerogen and black carbon by 6.7% and 11% would enhance the diffusion fluxes of the target compounds by 11-14% and 12-23%, respectively, at site A1, indicating that kerogen and black carbon were the key factors in mediating the sediment-water diffusion fluxes of DDT-related compounds in field environments.

Potential health risk for residents around a typical e-waste recycling zone via inhalation of size-fractionated particle-bound heavy metals

Health risk of residents dwelling around e-waste recycling zones has been a global concern, but has not been adequately examined. The present study was intended to evaluate the potential health risk of residents through inhalation exposure to size-fractionated particle-bound heavy metals in a typical e-waste recycling zone, South China. Anthropogenic metals (Zn, Se, Pb, Sb, As, and Cd) were predominantly enriched in fine particles (Dp<1.8μm), whereas the crustal elements (Ti, Fe, and Co) tended to accumulate in coarse particles (Dp>1.8μm). Although the daily inhalation intakes of the target metals were significantly lower than those through food consumption and ingestion of house dust, the hazard quotients of total metals for adults (95% CI: 1.0-5.5) and children (95% CI: 3.0-17) were greater than 1. Moreover, the incremental lifetime cancer risks of five carcinogenic metals (Cr, Co, Ni, As, and Cd) for adults and children were 1.3×10(-3) (95% CI: 4.1×10(-4)-3.0×10(-3)) and 3.9×10(-3) (95% CI: 1.3×10(-3)-8.6×10(-3)), respectively, substantially higher than the acceptable cancer risk range of 10(-6)-10(-4). All these findings suggested that health risks were high for local residents dwelling around the e-waste recycling zone through inhalation exposure to particle-bound heavy metals, for both adults and children.