Hazy Weather-Induced Variation in Environmental Behavior of PCDD/Fs and PBDEs in Winter Atmosphere of A North China Megacity

Polybrominated diphenyl ethers in dust, hair and urine: Exposure, excretion

Polybrominated diphenyl ethers (PBDEs) have been detected in various environmental media and human tissues. PBDEs concentrations in dust from college buildings and homes and in paired hair and urine samples from students were determined. This is of great significance to explore the accumulation and excretion patterns of PBDEs in the human body. The median PBDEs concentrations in the dust (College: 84.59 ng/g; Home: 170.32 ng/g) and hair (undergraduate: 6.16 ng/g; Home: 3.25 ng/g) samples were generally lower than were found in the majority of previous studies. The PBDEs concentrations in the hair and urine samples were subjected to principal component analysis, and the results combined with the PBDEs detection rates confirmed that hair is a useful non-invasive sampling medium for assessing PBDEs exposure and the risks posed. Body mass indices (BMIs) were used to divide students who had not been exposed to large amounts of PBDEs into groups. Body fat percentage is an important factor affecting the accumulation of PBDE in the human body. Environmental factors were found to affect the PBDEs concentrations in the hair and urine samples less for normal-weight students (BMI≤24) than overweight students (BMI>24). Short-term environmental changes to more readily affect the PBDEs concentrations in the tissues of the normal-weight than overweight students. PBDEs with seven or more bromine substituents were found not to be readily excreted in urine. Performing molecular docking simulations of the binding of isomers BDE-99 and BDE-100 to megalin. The binding energy was higher for BDE-100 and megalin than for BDE-99 and megalin, meaning BDE-99 would be more readily excreted than BDE-100.

PM2.5-bound polyhalogenated carbazoles (PHCZs) in urban Beijing, China: Occurrence and the source implication

Polyhalogenated carbazoles (PHCZs) are recently raising much attention due to their toxicity and ubiquitous environmental distribution. However, little knowledge is known about their ambient occurrences and the potential source. In this study, we developed an analytical method based on GC-MS/MS to simultaneously determine 11 PHCZs in PM_2.5 from urban Beijing, China. The optimized method provided low method limit of quantifications (MLOQs, 1.45-7.39 fg/m³) and satisfied recoveries (73.4%-109.5%). This method was applied to analyze the PHCZs in the outdoor PM_2.5 (n = 46) and fly ash (n = 6) collected from 3 kinds of surrounding incinerator plants (steel plant, medical waste incinerator and domestic waste incinerator). The levels of ∑₁₁PHCZs in PM_2.5 ranged from 0.117 to 5.54 pg/m³ (median 1.18 pg/m³). 3-chloro-9H-carbazole (3-CCZ), 3-bromo-9H-carbazole (3-BCZ), and 3,6-dichloro-9H-carbazole (36-CCZ) were the dominant compounds, accounting for 93%. 3-CCZ and 3-BCZ were significantly higher in winter due to the high PM_2.5 concentration, while 36-CCZ was higher in spring, which may be related to the resuspending of surface soil. Furthermore, the levels of ∑₁₁PHCZs in fly ash ranged from 338 to 6101 pg/g. 3-CCZ, 3-BCZ and 36-CCZ accounted for 86.0%. The congener profiles of PHCZs between fly ash and PM_2.5 were highly similar, indicating that combustion process could be an important source of ambient PHCZs. To the best of our knowledge, this is the first research providing the occurrences of PHCZs in outdoor PM_2.5.

Release Behavior of Liquid Crystal Monomers from Waste Smartphone Screens: Occurrence, Distribution, and Mechanistic Modeling

Liquid crystal display (LCD) screens can release many organic pollutants into the indoor environment, including liquid crystal monomers (LCMs), which have been proposed as a novel class of emerging pollutants. Knowing the release pathways and mechanisms of LCMs from various components of LCD screens is important to accurately assess the LCM release and reveal their environmental transport behavior and fate in the ambient environment. A total of 47, 43, and 33 out of 64 target LCMs were detected in three disassembled parts of waste smartphone screens, including the LCM layer (LL), light guide plate (LGP), and screen protector (SP), respectively. Correlation analysis confirmed LL was the source of LCMs detected in LGP and SP. The emission factors of LCMs from waste screen, SP, and LGP parts were estimated as 2.38 × 10^-3, 1.36 × 10^-3, and 1.02 × 10^-3, respectively. A mechanism model was developed to describe the release behaviors of LCMs from waste screens, where three characteristics parameters of released LCMs, including average mass proportion (AP), predicted subcooled vapor pressures (P_L), and octanol-air partitioning coefficients (K_oa), involving coexistence of absorption and adsorption mechanisms, could control the diffusion-partitioning. The released LCMs in LGP could reach diffusion-partition equilibrium more quickly than those in SP, indicating that LCM release could be mainly governed through SP diffusions.

Emission characteristics, environmental impact assessment and priority control strategies derived from VOCs speciation sourcely through measurement for wooden furniture-manufacturing industry in China

Volatile organic compounds (VOCs) from wooden furniture-manufacturing industry is an important emission source. The VOC content levels, source profiles, emission factors and inventories, O₃ and SOA formation, and priority control strategies were investigated from the source. One hundred sixty-eight representative woodenware coatings were sampled, and VOC species and contents were determined. The VOC, O₃ and SOA emission factors per gram of coatings for three types of woodenware coatings were quantified. The total VOC, O₃ and SOA emissions from wooden furniture-manufacturing industry in 2019 were 976,976 t/a, 2,840,282 t/a, 24,970 t/a, and solvent-based coatings accounted for 98.53 %, 99.17 % and 99.6 % of the total VOC, O₃ and SOA emissions, respectively. Aromatics and esters were major organic groups, contributing 49.80 % and 36.03 % to total VOC emissions, respectively. Aromatics contributed 86.14 % and 100 % to total O₃ and SOA emissions, respectively. The top 10 species contributing to VOC, O₃ and SOA had been identified. Four benzene series, including o-Xylene, m-Xylene, toluene and ethylbenzene, were ranked as the first-class priority control species, accounting for 85.90 % and 99.89 % of the total O₃ and SOA, respectively. Priority should be given to solvent-based coatings, aromatics and four benzene series for future O₃ and SOA reduction for wooden furniture-manufacturing industry.

Urban particulate water-soluble organic matter in winter: Size-resolved molecular characterization, role of the S-containing compounds on haze formation

Water-soluble organic matter (WSOM), as a group of ubiquitous components in atmospheric PM, plays a crucial role in global climate change and carbon cycle. In this study, the size-resolved molecular characterization of WSOM in the range of 0.010-18 μm PM was studied to gain insights into their formation processes. The CHO, CHNO, CHOS, CHNOS compounds were identified by the ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry in ESI source mode. A bimodal pattern of the PM mass concentrations was found in the accumulation and coarse mode. The increasing mass concentration of PM was mainly attributed to the growth of large-size PM with the occurrence of haze. Both Aiken-mode (70.5-75.6 %) and coarse-mode (81.7-87.9 %) particles were proven the main carriers of the CHO compounds, the majority of which were indicated to be the saturated fatty acids and their oxidized derivatives. The S-containing (CHOS and CHNOS) compounds in accumulation-mode (71.5-80.9 %) increased significantly in hazy days, where organosulfates (C₁₁H₂₀O₆S, C₁₂H₂₂O₇S) and nitrooxy-organosulfates (C₉H₁₉NO₈S, C₉H₁₇NO₈S) were confirmed in majority. The S-containing compounds in accumulation-mode particle with high oxygen content (6-8 oxygen atoms), unsaturation degree (DBE < 4), and reactivity could facilitate the particle agglomeration and accelerate the haze formation.

PCDD/Fs in indoor environments of residential communities around a municipal solid waste incineration plant in East China: Occurrence, sources, and cancer risks

Prolonged exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) can pose several adverse outcomes on human health. However, there is limited information on public health associated with indoor PCDD/F exposure in residential environments. Here, we examined PCDD/F concentrations in indoor air and indoor dust samples obtained from households near a municipal solid waste incineration (MSWI) plant. Our measurements revealed that the toxic equivalent (TEQ) concentrations of PCDD/Fs in indoor air ranged from 0.01 to 0.05 pg TEQ/m³, which were below intervention thresholds (0.6 pg TEQ/m³). Additionally, the TEQ concentrations of PCDD/Fs in indoor dust ranged from 0.30 to 11.56 ng TEQ/kg. Higher PCDD/F levels were found in household dust in the town of Taopu compared to those in the town of Changzheng. Principal component analysis (PCA) of PCDD/Fs suggested that waste incineration was the primary source of PCDD/Fs in indoor air, whereas PCDD/Fs in indoor dust came from multiple sources. The results of the health risk assessment showed the carcinogenic risk due to indoor PCDD/F exposure was higher for adults than for nursery children and primary school children. The carcinogenic risks of PCDD/Fs for age groups residing near the MSWI plant were all less than the risk threshold (10^-5). Our findings will help to better understand the levels of PCDD/F exposure among urban populations living in residential communities around the MSWI plant and to formulate corresponding control measures to reduce probabilistic risk implications.

Steady-State Based Model of Airborne Particle/Gas and Settled Dust/Gas Partitioning for Semivolatile Organic Compounds in the Indoor Environment

Indoor semivolatile organic compounds (SVOCs), present in the air, airborne particles, settled dust, and other indoor surfaces, can enter the human body through several pathways. Knowing the partitioning between gaseous and particulate phases is important in identifying specific pathway contributions and thereby accurately assessing human exposure. Numerous studies have developed equilibrium equations to predict airborne particle/gas (P/G) partitioning in air (K_P) and dust/gas (D/G) partitioning in settled dust (K_D). The assumption that P/G and D/G equilibria are instantaneous for airborne and settled dust phases, commonly adopted by current indoor fate models, is not likely valid for compounds with high octanol-air partition coefficients (K_OA). Here, we develop steady-state based equations to predict K_P and K_D in the indoor environment. Results show that these equations perform well and are verified by worldwide monitoring data. It is suggested that instantaneous steady state could work for P/G and D/G partitioning of SVOCs in indoor environments, and the equilibrium is just a special case of the steady state when log K_OA < 11.38 for P/G partitioning and log K_OA < 10.38 for D/G partitioning. These newly developed equations and methods provide a tool for more accurate assessment for human exposure to SVOCs in the indoor environment.

p-Phenylenediamine Antioxidants in PM2.5: The Underestimated Urban Air Pollutants

The wide use and continuous abrasion of rubber-related products appears to be leading to an incredible release of p-phenylenediamine (PPD) antioxidants in the environment. However, no related research has been conducted on the pollution characteristics and potential health risks of PM_2.5-bound PPDs. We report for the first time the ubiquitous distributions of six emerging PPDs and a quinone derivative, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPDQ), in PM_2.5 from urban areas of China. Atmospheric contamination levels of PM_2.5-bound PPDs were found to be mostly in pg m^-3 amounts between 2018 and 2019. Urban vehicle rubber tire abrasion was found to probably contribute to the PPDs in PM_2.5 and accounted for their significant spatiotemporal-dependent concentration variations. Furthermore, 6PPDQ, an emerging oxidation product of 6PPD in the environment, was first quantified (pg m^-3) with a total detection rate of 81% in the urban PM_2.5, demonstrating its broad existence. On the basis of the determined ambient concentrations, the annual intakes of PPDs and 6PPDQ for adults were not low, indicating their possible human health risks induced by long-term exposure. This study confirms the widespread occurrence of PPDs and 6PPDQ in PM_2.5, showing that the pollution of such compounds in urban air should not be underestimated.

Prediction of the gas/particle partitioning quotient of PAHs based on ambient temperature

Gas/particle (G/P) partitioning is an important influencing factor for the environmental fate of semi-volatile organic compounds (SVOCs). The G/P partitioning of polycyclic aromatic hydrocarbons (PAHs) is an integrated complex process due to its formation and growth concurrently with particles. Based on the large dataset of gaseous and particulate samples in a wide ambient temperature range of 50 °C, the simple empirical equations based on ambient temperature were established to predict the G/P partitioning quotient (K_P) of PAHs at the temperature range from 252 K to 307 K (-21 °C to 34 °C). The performance of the empirical equations was validated by comparison with the monitoring K_P of PAHs worldwide. The empirical equations exhibited good performance for the prediction of K_P of PAHs based on ambient temperature. Two deviations with the prediction lines of the previous G/P partitioning models from the monitoring data of K_P were observed. It was found that the deviations might be attributed to some non-considered influencing factors with the previous G/P partitioning prediction models. Therefore, further research should be conducted to study the mechanism of the G/P partitioning of PAHs, and more influencing factors should be introduced into the establishment of G/P partitioning models of PAHs. In summary, the result of the present study provided a convenient method for the prediction of K_P of PAHs, which should be useful for the study of environmental fate of PAHs in atmosphere.

Release and Gas-Particle Partitioning Behavior of Liquid Crystal Monomers during the Dismantling of Waste Liquid Crystal Display Panels in E-Waste Recycling Facilities

Liquid crystal monomers (LCMs) are a class of emerging chemical pollutants; however, their release and gas-particle partitioning remain unknown. This study performed the first comprehensive analysis of a wide range of 93 LCMs in the ambient air of liquid crystal display (LCD) dismantling facilities. A total of 53 of the 93 target LCMs were detected in the air samples. The total atmospheric concentrations (gas and particles) of LCMs (∑LCMs) ranged from 68,800 to 385,000 (median of 204,000) pg/m³. Most LCMs were predominant in the gas phase, implying that their atmospheric transport would be mainly governed by gas rather than particle diffusions. Differential distribution patterns of the LCMs were observed due to their different atmospheric partitioning behaviors. Significant linear correlations were found between the gas-particle partitioning coefficients (K_P) and the predicted subcooled vapor pressures (P_L) and octanol-air partitioning coefficients (K_oa) (p < 0.01). Compared with two equilibrium-state models, the experimentally observed particulate fractions (ϕ) fit better with the predicted values based on the Li-Ma-Yang (L-M-Y) steady-state model, and K_oa was identified as a key factor determining the atmospheric fate pathways of LCMs. Our study highlights another new class of chemicals significantly contributing to the chemical mixture in the ambient air at e-waste recycling areas.

Characteristics of PAHs, PCDD/Fs, PCBs and PCNs in atmospheric fine particulate matter in Dalian, China

Organic species in fine particulate matter (PM_2.5) may exhibit significant health risks. The level, composition and sources of PM_2.5-bound organic pollutants are temporally and spatially highly variable. In this study, the pollution characteristics and health risks of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs) and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) in PM_2.5 of Dalian were investigated. PM_2.5-bound organic pollutants in Dalian were generally lower than other regions in China and other countries, significant seasonal changes were observed, higher levels appeared in winter than in summer. Concentrations of 16 PAHs were 2.07 ng/m³ and 13.99 ng/m³ in summer and winter, respectively. PAHs with 4-ring and 5-ring were the dominant components. Diagnostic analysis and principal component analysis (PCA) indicated that PAHs mainly originate from petroleum emissions and combustion. Concentrations of PCDD/Fs, PCBs and PCNs in PM_2.5 ranged from 0.05 to 3.27, 0.04-0.65 and 0.05-1.42 pg/m³, respectively. PCDD/Fs and PCBs were mainly consisted of high-chlorinated homologues during the sampling period. High-chlorinated PCNs were dominated only in winter, while low-chlorinated PCNs were dominated in summer, industrial thermal activity was one of the main sources of PCNs. The high correlation coefficients of the concentration of PAHs, PCBs, PCNs, and PCDD/Fs with that of SO₂ indicated that combustion sources contributed more to PM_2.5-bound organic pollutants than that of motor vehicle emissions. The incremental lifetime cancer risk induced by PM_2.5-bound POPs is relatively lower in Dalian than other regions.

Particle/gas partitioning for semi-volatile organic compounds (SVOCs) in Level III multimedia fugacity models: Gaseous emissions

Atmospheric transport is a global-scale process that moves semi-volatile organic compounds (SVOCs) rapidly from source regions to remote locations, where these chemicals have never been produced or used. Particle/gas (P/G) partitioning of SVOCs during atmospheric transport governs wet and dry deposition, and thereby controls the efficiency and scope of long-range atmospheric transport and fate for these sorts of compounds. Previous work has shown that the assumption of steady state between particulate and gaseous phases in the atmosphere leads to model results that more closely match observations especially for compounds that strongly favor the particulate phase. Here, the practical application of steady-state P/G partitioning in the atmosphere in multimedia fugacity models is presented in greater detail. A method is developed whereby the fugacity of a chemical in the particle-phase is set equal to that in the gaseous phase (a pseudo equilibrium) but still maintains steady state of the chemical between air and aerosols in the atmosphere. This procedure greatly simplifies the application of multimedia fugacity models. Using this approach, a condition of steady state between air and aerosols is developed and applied in a Level III six-compartment six-fugacity model, which becomes a much simpler Level III six-compartment four-fugacity model. This newly-developed model is then applied to data observed during a monitoring program.

Commodity plastic burning as a source of inhaled toxic aerosols

Commodity plastic is ubiquitous in daily life and commonly disposed of via unregulated burning, particularly in developing regions. We report here the much higher emission factors (13.1 ± 7.5 g/kg) and toxicities of inhalable aerosols emitted from the unregulated burning of plastic waste based on field measurements and cellular experiments, including oxidative stress and cytotoxic tests in A549 cells. Plastic foam burning emitted aerosols possesses the highest EFs (34.8 ± 4.5 g/kg) and toxicities, which are 4.2- to 13.4-fold and 1.1- to 2.7-fold higher than those emitted from the burning of other waste types. These quantified toxicities are mainly attributed to aerosols containing carbonaceous matter, especially persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins, which originate from incomplete combustion processes. The aerosol emission amounts were estimated from the obtained experimental results. Approximately 70.2 million tons (29%) of plastic waste was burned without regulation worldwide in 2016, leading to 0.92 ± 0.53 million tons of toxic aerosols being released into the air, a majority of which occurred in developing regions. The results indicate improved combustion technology and control strategies are urgently needed in developing regions for discarded plastic -waste to mitigate toxic exposure risks and achieve sustainable development.

Factors affecting multiple persistent organic pollutant concentrations in the air above Japan: A panel data analysis

Numerous reports have elucidated different statistical approaches to identify temporal trends in atmospheric persistent organic pollutant (POP) time series. However, the correlation of industrial activity with concentrations of atmospheric POPs in Japan has not yet been determined. Herein, a panel data analysis of a 16-year monitoring program (2003-2018) conducted by the Japanese Ministry of Environment was used to investigate a range of POPs in the atmosphere above Japan. This work focuses on polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB), and pentachlorobenzene (PeCBz) collected each year at 53 sites across Japan. The panel analysis revealed that PCB, PCN, and PBDE concentrations were influenced by a combination of factors including year, industrial activity (municipal and industrial waste incinerators, cement kilns, steel industry, and secondary zinc production), population, temperature, and atmospheric boundary layer. However, HCB and PeCBz were not significantly affected by these factors. Industrial activity showed stronger positive correlations with all homologues of PCBs, PCNs, and PBDEs as compared to those demonstrated by population. Significant decreasing trends were identified for the atmospheric ∑PBDEs (half-life t_1/2 = 9.4 years), ∑PCNs (t_1/2 = 8.9 years), and ∑PCBs (t_1/2 = 13.5 years) concentrations, while HCB and PeCBz showed slightly increasing or steady levels. As a statistical tool, panel data analysis can contribute to the assessment of spatial and temporal trends of POPs at a national scale, while elucidating different behavioral responses to numerous environmental variables.

Probing Legacy and Alternative Flame Retardants in the Air of Chinese Cities

An increasing number of alternative flame retardants (FRs) are being introduced, following the international bans on the use of polybrominated diphenyl ether (PBDE) commercial mixtures. FRs' production capacity has shifted from developed countries to developing countries, with China being the world's largest producer and consumer of FRs. These chemicals are also imported with e-waste to China. Therefore, it is important to understand the current status of regulated brominated FRs, their phase-out in China, and their replacement by alternatives. In this study, a broad suite of legacy and alternative FRs, including eight PBDEs, six novel brominated FRs (NBFRs), two dechlorane plus variants (DP_S), and 12 organophosphate FRs (OPFRs) were evaluated in the air of 10 large Chinese cities in 2018. OPFRs are the most prevalent FRs in China, exhibiting a wide range of 1-612 ng/m³, which is several orders of magnitude higher than PBDEs (1-1827 pg/m³) and NBFRs (1-1428 pg/m³). BDE 209 and DBDPE are the most abundant compounds in brominated FRs (>80%). The North China Plain (NCP, excluding Beijing), Guangzhou, and Lanzhou appear to be three hotspots, although with different FR patterns. From 2013/2014 to 2018, levels of PBDEs, NBFRs, and DPs have significantly decreased, while that of OPFRs has increased by 1 order of magnitude. Gas-particle partitioning analysis showed that FRs could have not reached equilibrium, and the steady-state model is better suited for FRs with a higher log K_OA (>13). To facilitate a more accurate FR assessment in fine particles, we suggest that, in addition to the conventional volumetric concentration (pg/m³), the mass-normalized concentration (pg/g PM_2.5) could also be used.

Accumulation characteristics and estimated dietary intakes of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls in plant-origin foodstuffs from Chinese markets

The levels and accumulation characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were investigated in nine pools of representative plant-origin foodstuffs randomly collected from markets located in five regions of the Chinese mainland during 2018-2019. The collected foodstuffs consisted of cereals, beans, potatoes, leafy vegetables, root and stem vegetables, melon vegetables, legume vegetables, edible fungi, and mixed vegetable oil. In the fresh plant food pools, the concentrations of toxic equivalency (WHO-TEQ) were in the ranges of 0.9-14.5 pg/kg in upperbound (UB) scenario and 0.002-7.3 pg/kg in lowerbound (LB) scenario on a fresh weight basis; and TriCDFs and TeCBs were the predominant PCDD/F and PCB homologues, respectively. In the mixed vegetable oil, the WHO-TEQ concentrations were 129.4 pg/kg and 103.6 pg/kg on a lipid weight basis in UB and LB scenarios, respectively; and high-chlorinated PCDD/F and PCB homologues were much more abundant. The estimated plant food-borne dietary intakes of WHO-TEQ by a standard adult in the five surveyed regions were in the ranges of 3.39-4.20 and 1.57-2.13 pg WHO-TEQ/kg body weight/month in UB and LB scenarios, respectively. Among all surveyed regions, consumption of cereals and vegetable oil made up the primary contributions to the estimated dietary intakes of WHO-TEQ. TriCDFs accounted for 41.1-83.9% of the PCDD/Fs dietary intakes via consumption of plant foods, and TeCBs made up 61.2-73.0% of the PCBs dietary intakes via consumption of plant foods, suggesting that the potential toxic effects of TriCDFs and TeCBs on human health should be concerned.

Slopes and intercepts from log-log correlations of gas/particle quotient and octanol-air partition coefficient (vapor-pressure) for semi-volatile organic compounds: I. Theoretical analysis

Gas/particle partitioning governs the transport and fate of semi-volatile organic compounds (SVOCs) released to the atmosphere. The partition quotient of SVOCs, K_P, is related to their subcooled liquid vapor pressure (logK_P = m_p logP_L + b_p) and to their octanol-air partition coefficient (logK_P = m_o logK_OA + b_o). Previous theory predicts that -m_p and m_o should be close to, or equal to 1 based on the assumption that gas- and particle-phases are at equilibrium in the atmosphere. Here, we develop analytical equations to calculate m_o and b_o as functions of logK_OA and m_p and b_p as functions of logP_L. We find that experimental, analytical, or statistical artifacts and other reported factors are not the leading causes for deviations of the slopes, m_p and m_o, from -1 and 1, respectively. Rather, it is the inherent parameter, K_OA, that determines m_o and b_o, and equivalently, P_L is the major parameter determining m_p and b_p, and such deviations are evidence that equilibrium is an inappropriate assumption. In contrast, the actual steady-state between gas and particle phases of SVOCs leads that their -m_p and m_o should range from 0 to 1, implying that equilibrium is a reasonable assumption only when -m_p and m_o are larger than 0.49. To illustrate these points, we provide a detailed discussion of the global atmospheric transport of polybrominated diphenyl ethers (PBDEs) with emphasis on Polar Regions where low air temperatures favor a special steady-state, where their slopes m_p and m_o can reach 0, indicating a constant value of logK_P (-1.53).

Slopes and intercepts from log-log correlations of gas/particle quotient and octanol-air partition coefficient (vapor-pressure) for semi-volatile organic compounds: II. Theoretical predictions vs. monitoring

The logarithm of gas/particle (G/P) partition quotient (logK_P) has been found to have a linear relationship with logK_OA (octanol-air partition coefficient) with slope m_o and intercept b_o and logP_L (subcooled liquid vapor pressure) with slope m_p and intercept b_p. In the sister paper of the present work, analytical equations to predict the slope m_o and intercept b_o based on logK_OA and predict the slope m_p and intercept b_p based on logP_L are developed using steady state theory. In this work, the equations are evaluated using world-wide monitoring data (262 pairs for m_o and b_o values and 292 pairs for m_p and b_p values produced from more than 10,000 monitiring data worldwide) for selected seven groups of semi-volatile organic compounds (SVOCs), including polybrominated diphenyl ethers (PBDEs), polychlorinated dibenzo-p-dioxins and polychorinated dibenzofurans (PCDD/Fs), polyclorinated biphenyl (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated naphthalenes (PCNs), organochlorinated pesticides (OCPs), novel brominated flame retardants (NBFRs), and other selected halogenated flame retardants. The slopes and intercepts predicted by the steady state equations reproduce the trends observed in monitoring regression results for the seven SVOC groups, with 44.4% of the variation of monitoring m_o values accounted for by logK_OA and 48.2% of the variation of monitoring m_p values accounted for by logP_L. Theoretically, the values of m_o can be any value between 0 and 1 dependent on the values of K_OA, and are not constrained to 1 as in equilibrium theory. Likewise, the values of m_p can be any value between 0 and -1 dependent on the values of P_L, and not constrained to -1 predicted by the equilibrium theory. The influence of sampling artifacts on the G/P partitioning of SVOCs has most likely been overemphasized by the equilibrium theory. Thus, the equilibrium approach should be abandoned in favor of the steady state approach for calculating the G/P partition quotients for SVOCs with high K_OA values (>10^11.38) or low P_L values (<10^-4.92).

Extreme Exposure Levels of PCDD/Fs Inhaled from Biomass Burning Activity for Cooking in Typical Rural Households

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), emitted during biomass combustion, are carcinogenic chemicals. The association between indoor biomass burning and PCDD/Fs inhalation exposure levels is still poorly understood. This study first reports direct measurement of personal exposure to PCDD/Fs in real-world households with wood combustion. In homes where biomass burning is used for cooking, toxic equivalent quantity (TEQ) PCDD/Fs concentrations were found to be 545 ± 251 fg I-TEQ/m³ in kitchens, with levels of 4.5-, 6.9-, and 13.3-fold higher than those in living rooms (122 ± 92 fg I-TEQ/m³), bedrooms (79 ± 27 fg I-TEQ/m³), and ambient air (41 ± 15 fg I-TEQ/m³), respectively. PCDD/Fs exposure levels in populations using biomass fuels for cooking (353 ± 110 fg I-TEQ/m³) were 4.3-fold higher than those in the control groups (82 ± 32 fg I-TEQ/m³). Additionally, the average cancer risks for biomass cooking person were approximately 3.1-fold higher than those in factory workers. Overall, residents of household that use biomass fuels for cooking have the highest known risk of PCDD/Fs exposure. These results highlight that aiming to mitigate the PCDD/Fs exposure risk in the general population, the focus of dioxin emission source control measures should shift from industrial sectors to residential biomass combustion.

Treatment of particle/gas partitioning using level III fugacity models in a six-compartment system

In this paper, two level III fugacity models are developed and applied using an environmental system containing six compartments, including air, aerosols, soil, water, suspended particulate matters (SPMs), and sediments, as a "unit world". The first model, assumes equilibrium between air and aerosols and between water and SPMs. These assumptions lead to a four-fugacity model. The second model removes these two assumptions leading to a six-fugacity model. The two models, compared using four PBDE congeners, BDE-28, -99, -153, and -209, with a steady flux of gaseous congeners entering the air, lead to the following conclusions. 1. When the octanol-air partition coefficient (K_OA) is less than 10^11.4, the two models produce similar results; when K_OA > 10^11.4, and especially when K_OA > 10^12.5, the model results diverge significantly. 2. Chemicals are in an imposed equilibrium in the four-fugacity model, but in a steady state and not necessary an equilibrium in the six-fugacity model, between air and aerosols. 3. The results from the six-fugacity model indicate an internally consistent system with chemicals in steady state in all six compartments, whereas the four-fugacity model presents an internally inconsistent system where chemicals are in equilibrium but not a steady state between air and aerosols. 4. Chemicals are mass balanced in air and aerosols predicted by the six-fugacity model but not by the four-fugacity model. If the mass balance in air and aerosols is achieved in the four-fugacity model, the condition of equilibrium between air and aerosols will be no longer valid.

4-Mercaptobenzoic acid as a MALDI matrix for highly sensitive analysis of metals

4-Mercaptobenzoic acid (MBA) is introduced as a matrix for laser desorption/ionization time-of-flight mass spectrometry (MS) analysis of metals, exhibiting matrix-interference-free background, greatly enhanced MS signal intensity, and excellent reproducibility. The developed method was successfully extended for the rapid screening and sensitive determination of ultratrace metals in fine particulate matter (PM_2.5).

The effect of toxic components on metabolomic response of male SD rats exposed to fine particulate matter

PM_2.5 pollution was associated with numerous adverse health effects. However, PM_2.5 induced toxic effects and the relationships with toxic components remain largely unknown. To evaluate the metabolic toxicity of PM_2.5 at environmentally relevant doses, investigate the seasonal variation of PM_2.5 induced toxicity and the relationship with toxic components, a combination of general pathophysiological tests and metabolomics analysis was conducted in this study to explore the response of SD rats to PM_2.5 exposure. The result of general toxicology analysis revealed unconspicuous toxicity of PM_2.5 under environmental dose, but winter PM_2.5 at high dose caused severe histopathological damage to lung. Metabolomic analysis highlighted significant metabolic disorder induced by PM_2.5 even at environmentally relevant doses. Lipid metabolism and GSH metabolism were primarily influenced by PM_2.5 exposure due to the high levels of heavy metals. In addition, high levels of organic compounds such as PAHs, PCBs and PCDD/Fs in winter PM_2.5 bring multiple overlaps on the toxic pathways, resulting in larger pulmonary toxicity and metabolic toxicity in rats than summer.

Occurrence and human exposure assessment of organophosphate esters in atmospheric PM2.5 in the Beijing-Tianjin-Hebei region, China

Organophosphate esters (OPEs) in atmospheric fine particles (PM_2.5) were comprehensively investigated in the Beijing-Tianjin-Hebei (BTH) region from April 2016 to March 2017. The concentrations of Σ₈OPEs in all the five sampling sites ranged from 90 to 8291 pg/m³ (mean 1148 ± 1239 pg/m³; median 756 pg/m³). The highest level (median 1067 pg/m³) was found at one of the urban sites in Beijing, followed by Tianjin (746 pg/m³) and Shijiazhuang (724 pg/m³). Tris(2-chloroethyl) phosphate (TCEP) and tri[(2R)-1-chloro-2-propyl] phosphate (TCPP) were the dominant compounds across the five sampling locations. Generally, the concentrations of chlorinated OPEs were relatively higher in summer than in winter (p < 0.05), but no significant seasonal difference was discovered for non-chlorinated individual OPEs. The concentrations of tri-n-butyl phosphate (TBP), TCEP, TCPP and triphenyl phosphate (TPP) were positively correlated with the meteorological parameters (i.e. temperature and relative humidity) (p < 0.05), indicating an evident influence of meteorological condition on OPE distribution. We observed a negative correlation (p < 0.05) between octanol-air partition coefficients (logK_oa) and the ratio of PM_2.5-bound OPE concentrations to total suspended particulates-bound OPE concentrations, suggesting that physicochemical properties affect the particle-size distribution of OPEs. Furthermore, the median value of cancer hazard quotients (HQs) of TCEP was higher than TBP and tris(2-ethylhexyl) phosphate (TEHP). The health risk assessment showed that HQ values for children were ~1.6 times higher than those for adults. Relatively higher health risk induced by PM_2.5-bound OPEs via inhalation was found during severe hazy days than in clear days.

New equation to predict size-resolved gas-particle partitioning quotients for polybrominated diphenyl ethers

Gas/particle (G/P) partition quotients of semi-volatile organic compounds (SVOCs) for bulk air have been widely discussed in experimental and theoretical contexts, but research on size-resolved G/P partition quotients (K_Pi) are scarce and limited in scope. To investigate G/P partition behavior of polybrominated diphenyl ethers (PBDEs) for size-segregated particles in the atmosphere, 396 individual size-segregated particulate samples (36 batches × 11 size-ranges), and 108 pairs of concurrent gaseous and bulk particulate samples were collected in Harbin, China. A steady-state equation based on bulk particles is derived to determine G/P partition quotients of PBDEs for size-segregated particles, which depends on the organic matter contents of size-segregated particles (f_OMi). This equation can well predict K_Pi with knowledge of bulk partition quotient (K_PS), ambient temperature, and f_OMi, the results of which match well with monitoring data in Harbin and other published data collected in Shanghai and Guangzhou of China and Thessaloniki of Greece, and remedies a defect of over-estimate K_Pi for high-brominated PBDEs by the previous equation. In particular, the new equation contributes to obtaining the PBDEs concentrations in all atmospheric phase from partial phase, then provides a credible path to evaluate healthy exposure dose from the airborne PBDEs, by co-utilization with exposure models.

Legacy and novel halogenated flame retardants in seawater and atmosphere of the Bohai Sea: Spatial trends, seasonal variations, and influencing factors

Seventeen halogenated flame retardants (HFRs) were concurrently analyzed in surface seawater and low atmospheric samples from the Bohai Sea during four research cruises. HFRs mainly existed in particulate phases, and in general decabromodiphenyl ethane (DBDPE) was the predominant compound in both air and water samples. Relatively high concentrations were observed in the water of Laizhou Bay (LB), where the largest manufacturing base of brominated flame retardants (BFRs) in China is located and weak water exchange occurs. Transport from LB by coastal currents may be the main source of BFRs in some areas without emission sources. The HFRs in seawater exhibited distinct seasonal variation, with significantly higher concentrations in winter than those in summer. The controlling factors include the resuspension of sediment induced by large wind waves in winter and phytoplankton scavenging in spring and seawater stratification in summer. HFRs composition varied largely in different seasons, due to the different extents of riverine input and atmospheric deposition. Normally, for air masses passing through the nearby industrial regions, high concentrations of DBDPE (up to 1780 pg m^-3) co-existed with high total suspended particle (TSP) levels (up to 150 μg m^-3). The estimated atmospheric deposition fluxes of HFRs were 19, 51, and 80 kg season^-1 in spring, summer, and winter, respectively, indicating that the Bohai Sea is a sink of HFRs via atmospheric deposition. This study has increased our understanding of the behaviors and fates of the legacy and novel HFRs in the shallow coastal sea.

Sources and health risks of PM2.5-bound polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in a North China rural area

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) are typical persistent organic pollutants (POPs), which have high toxicity, bioaccumulation and long-distance transfer capability. Daily variation, sources of PCBs and OCPs in PM_2.5 are rarely explored in polluted rural area. Here, the sources and health risks of the PCBs and OCPs were evaluated for 48 PM_2.5 samples collected in winter 2017 in Wangdu, a heavy polluted rural area in the North China Plain. The average diurnal and nocturnal concentrations of Σ₁₈PCBs and Σ₁₅OCPs were 1.74-24.37 and 1.77-100.49, 11.67-408.81 and 16.89-865.60 pg/m³, respectively. Hexa-CBs and penta-CBs accounted for higher proportions (29.0% and 33.6%) of clean and polluted samples, respectively. Hexachlorobenzene (HCB) was the dominant contributor to OCPs with an average concentration of 116.17 pg/m³. Hexachlorocyclohexane (ΣHCHs) and dichlorodiphenyltrichloroethane (ΣDDTs) were the other two main classes in OCPs with the average concentrations of 4.33 and 15.89 pg/m³, respectively. β-HCH and p,p'-DDE were the main degradation products of HCHs and DDTs, respectively. The principal component analysis and characteristic ratio method indicated both waste incineration and industrial activities were the main sources of PCBs, contributing 76.8% and 12.7%, respectively. The loadings of OCPs were attributed to their application characteristics and the characteristic ratio method reflected a current or past use of OCPs. Health risk assessment showed that the respiratory exposure quantity of doxin-like PCBs (DL-PCBs) and the lifetime cancer risk from airborne OCPs exposure was negligible, while the other exposure modes may pose a risk to human bodies.

Modeling gas/particle partitioning of polybrominated diphenyl ethers (PBDEs) in the atmosphere: A review

Gas/particle (G/P) partitioning of semi-volatile organic compounds (SVOCs) such as polybrominated diphenyl ethers (PBDEs), is an important atmospheric process due to its significance in governing atmospheric fate, wet/dry deposition, and long-range atmospheric transport. In this article, eight models published to predict the G/P partitioning of PBDEs are reviewed. These eight models are used to calculate the G/P partitioning quotient and particulate phase fraction of selected PBDE congeners. A comparison of the predicted results from the eight models with monitoring data published by several research groups worldwide leads to the following conclusions: 1) when the values of the logarithm of the octanol-air partition coefficient (logK_OA) fall below 11.4 (the first threshold value, logK_OA1), all 8 models perform well in predicting the G/P partitioning of PBDEs in the atmosphere, and 2) when logK_OA is >11.4, and especially above 12.5 (the second threshold value, logK_OA2), the Li-Ma-Yang model, a steady-state model developed based on wet and dry deposition of the particles (Li et al., Atmos. Chem. Phys. 2015; 15:1669-1681), shows the best performance with highest conformity to the measurements for selected PBDEs (94.4 ± 1.6% data points within ±1 log unit). Overall, the Li-Ma-Yang model appears to capture the most important factors that affect the partitioning of PBDEs between gaseous and particular phases in the atmosphere.

Gas/particle partitioning of semi-volatile organic compounds in the atmosphere: Transition from unsteady to steady state

We derive differential equations to determine the kinetics of gas/particle partitioning of semi-volatile organic compounds (SVOCs). These equations model the transient states from initiation of sorption to particles (non-steady state) through the establishment of steady state. Two hypothetical scenarios are examined: (1) exchange of SVOCs between gas- and particle-phases alone; and (2) both gas/particle partitioning and wet and dry deposition of particles. The differential equations show that, under Scenario 1, a steady state is reached as an equilibrium between gas- and particle-phases, whereas under Scenario 2, the attained steady state is not in equilibrium. Our model shows that SVOCs in atmosphere where particle deposition is occurring reach a steady non-equilibrium state sooner than they would reach equilibrium under Scenario 1. We infer that SVOCs in the atmosphere will reach steady state instead of equilibrium between gaseous and particulate phases in circumstances where wet and dry deposition of particles cannot be neglected. In addition, our study indicates that the time for SVOCs to reach steady state in the atmosphere is fast, most likely within minutes or hours, suggesting that SVOCs are in steady or quasi-steady state in the atmosphere. Our analysis also reveals that gas/particle partitioning and particle deposition of SVOCs are dependent on each other.

Characteristics, sources and health risks of toxic species (PCDD/Fs, PAHs and heavy metals) in PM2.5 during fall and winter in an industrial area

Particulate toxic species, such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals may have significant health risks. This study investigated characteristics, sources and health risks of all three classes of toxic species in PM_2.5 (particles with aerodynamic diameter ≤2.5 μm) samples collected at an industrial area in Changzhou, a big city in the Yangtze Delta region of China. Fourteen heavy metals altogether constituted 2.87% of PM_2.5 mass, with Fe, Al and Zn as the major elements. Principal component analysis (PCA) suggested that heavy metals came from four sources: vehicles, industry, crustal dust, mixed coal combustion and industrial process. The daily average concentration of 18 PAHs was 235.29 ng/m³, accounting for 0.21% of PM_2.5 mass. The dominant PAHs were high molecular weight ones, contributing 73.5% to the total PAHs. Diagnostic analyses indicated that sources of PAHs included vehicle/coal combustion and petroleum emissions, wherein diesel emission played a more important role than gasoline emission. PCA showed that the largest contributor of PAHs was vehicle exhaust mixed with coal combustion, followed by three industry-related sources. Total concentration of 17 PCDD/Fs varied between 3.14 and 37.07 pg/m³, with an average of 14.58 pg/m³. The 10 PCDFs accounted for 70.5% of total concentration of 17 PCDD/Fs. Health risk assessments showed that the carcinogenic risk of heavy metals was acceptable, while risks from PAHs and PCDD/Fs cannot be ignored. Back trajectory analysis indicated that local/regional transported air masses from northern China was the major source areas of the toxic species.

Higher health risk resulted from dermal exposure to PCBs than HFRs and the influence of haze

To investigate the influence of haze on human dermal exposure to a series of halogenated flame retardants (HFRs) and polychlorinated biphenyls (PCBs), paired forehead wipes were collected from 46 volunteers (23 males, 23 females) using gauze pads soaked in isopropyl alcohol under heavy and light haze pollution levels. The median levels of ∑₂₇HFRs and ∑₂₇PCBs in all 92 samples were 672 and 1300ng/m², respectively. Decabromodiphenyl ether (BDE-209) (171ng/m²) and decabromodiphenylethane (DBDPE) (134ng/m²) were the dominant components of HFRs, indicating that dermal exposure may also be the significant pathway for non-volatile compounds. PCB-37 contributed the most to ∑₂₇PCBs, with a median concentration of 194ng/m², followed by PCB-60 (141ng/m²). Generally, PBDE, PCB and DD (dehalogenated derivatives of DPs) levels on the foreheads of female participants (291, 1340, 0.92ng/m²) were higher (p=0.037, 0.001, and 0.031, respectively) than those of male participants (226, 989, and 0.45ng/m²). A significant difference (p=0.001) in PCBs was found between light (1690ng/m²) and heavy (996ng/m²) haze pollution conditions. Nevertheless, HFR levels under heavy (median=595ng/m², ranging from 295 to 1490ng/m²) and light haze pollution conditions (ranging from 205 to 1220ng/m² with a median of 689ng/m²) did not show significant differences (p=0.269). The non-carcinogenic health risk resulting from dermal exposure to ∑₈HFRs and ∑₂₇PCBs was 8.72×10^-5 and 1.63×10^-2, respectively, raising more concern about populations' exposure to PCBs than HFRs.

Brominated flame retardants in atmospheric fine particles in the Beijing-Tianjin-Hebei region, China: Spatial and temporal distribution and human exposure assessment

Atmospheric fine particle (PM_2.5) samples were collected over a whole year (April 2016 - March 2017) across five sampling locations in the Beijing-Tianjin-Hebei (BTH) region, to investigate the occurrence of novel brominated flame retardants (NBFRs) and polybrominated diphenyl ethers (PBDEs). The concentrations of ∑₉NBFRs were in the range of 0.63-104 pg/m³ (15.6 ± 16.8 pg/m³) in atmospheric PM_2.5, while the levels of ∑₉PBDEs (excluding BDE-209) ranged from 0.05 to 19.1 pg/m³ (2.9 ± 3.8 pg/m³) and BDE-209 concentrations ranged from 0.88 to 138 pg/m³ (22 ± 28 pg/m³). Relatively higher levels of NBFRs and PBDEs were found at urban sampling sites in Beijing City and Shijiazhuang City. Decabromodiphenylethane (DBDPE) and BDE-209 were the dominant compounds with the relative abundances of 72% in ∑₉NBFRs and 90% in ∑₁₀PBDEs, respectively. Generally, the levels of most target BFRs in summer were lower than those in other seasons. However, there were no notable seasonal differences in levels of DBDPE and BDE-209 in atmospheric PM_2.5 samples across the BTH region. Significant and positive correlations were found between the concentrations of BFRs and PM_2.5. Daily human exposure via inhalation revealed that children have a higher probability of suffering from the adverse effects of BFRs than that of adults. In addition, residents living near sampling locations across the BTH region may suffer high exposure risks to BDE-209 and NBFRs.