Spatiotemporal Distribution and Alpine Behavior of Short Chain Chlorinated Paraffins in Air at Shergyla Mountain and Lhasa on the Tibetan Plateau of China

Tibetan lake sediment records reveal historical emission and long-range atmospheric transport of chlorinated paraffins

The Tibetan Plateau, a recognized global sink for Persistent Organic Pollutants (POPs), lies adjacent to two major emitting regions, inland China and India. This unique geographical setting makes it a pivotal site for examining the presence and compositional evolution of POPs following their long-range atmospheric transport (LRAT). This study focuses on the current predominant POPs, chlorinated paraffins (CPs). We comprehensively screened 675 homologues of the very short- (vSCCPs), short- (SCCPs), medium- (MCCPs), and long-chain CPs (LCCPs) in six dated sediment cores across the extensive Tibetan area. The findings unveiled pronounced temporal disparities in CP concentrations and compositions between Tibet's southern and eastern sectors, reflecting divergent usage and emission chronicles of inland China and India. Notably, a market shift in China from regulated SCCPs to the in-use MCCPs and LCCPs was observed in the 21st century, contrasting with India's unregulated production of SCCPs. The Organization for Economic Cooperation and Development (OECD) Screening Tool, developed to assess the overall persistence (POV) and long-range transport potential (LRTP) of organic chemicals, elucidated the erosion of CP source signatures induced by fractionation, a process that intensifies with transport distance from the source regions. This study enhances our understanding of the emission inventories and LRAT behavior of these transitional regulatory contaminants, highlighting the Tibetan Plateau's crucial role as an environmental sentinel in global pollution dynamics.

Characterizing organophosphate esters and chlorinated paraffins in surface soils affected by diverse e-waste disassembling process in South China: Occurrence, distinct emission, and risk assessment

E-waste recycling activities are a crucial emission source of organic pollutants, posing potential risks to the surrounding environment and human health. To understand the potential impact related to diverse e-waste dismantling activities, we investigated two categories of popular flame retardants (i.e., organophosphate esters (OPEs) and chlorinated paraffins (CPs) and their resultant possible ecological risk in 53 surface soil samples from Qingyuan, a well-known e-waste recycling region in South China. Varied concentrations of ΣOPEs (20.5-8720 ng/g) and ΣCPs (920-16800 ng/g) were observed at diverse dismantling sites, while relatively low levels of ΣOPEs (6.13-1240 ng/g) and ΣCPs (14.8-2870 ng/g) were found in surrounding soils. These results indicated that primitive e-waste dismantling processes were the primary emission source of OPEs and CPs in the studied area, with e-waste dumping and manual dismantling being the most important emission sources for OPEs and CPs. More importantly, CPs could be degraded/transformed into more toxic intermediates via dechlorination and decarbonization during the burning of e-waste. Furthermore, our results indicated the potential ecological risks posed by OPEs and CPs related to e-waste recycling.

Modeling Global Environmental Fate and Quantifying Global Source-Receptor Relationships of Short-, Medium-, and Long-Chain Chlorinated Paraffins

Decades-long emissions and long-range transport of chlorinated paraffins (CPs) have resulted in their pervasive presence in the global environment. The lack of an understanding of the global distribution of short-, medium-, and long-chain CPs (SCCPs, MCCPs, and LCCPs) hinders us from quantitatively tracing their origins in remote regions. Using the BETR-Global model and historical emission estimates, we simulate the global dispersion of CPs from 1930 to 2020. Whereas contamination trends in the main contaminated regions (East Asia, Europe, North America, and South Asia) diverge, CP concentrations in the Arctic, Antarctica, and the Tibetan Plateau all increase. By 2020, East Asian, European, and North American emissions contributed 38%, 26%, and 18% of CP contamination in the High Arctic, respectively, while Southern hemispheric emissions and emissions around the Tibetan Plateau primarily contribute to CP contamination in central Antarctica and on the Plateau, respectively. Our results emphasize the important contribution of (i) European and North American emissions to historical CP contamination in remote regions and current MCCP and LCCP contamination in the High Arctic and (ii) East Asian emission to current SCCP and MCCP contamination of all three remote regions. These results can help to evaluate the effectiveness of potential global and regional CP emission-reduction strategies.

First comprehensive assessment of dietary chlorinated paraffins intake and exposure risk for the rural population of the Tibetan Plateau, China

Knowledge regarding the occurrence of short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) in foodstuffs and their dietary exposure risks for rural Tibetan residents remains largely unknown. Herein, we collected main foodstuffs (including highland barley, vegetables, Tibetan butter, mutton, and yak beef) across the rural Tibetan Plateau and characterized the CP profiles and concentrations. The highest SCCPs concentrations were detected in Tibetan butter (geometric mean (GM): 240.6 ng/g wet weight (ww)), followed by vegetables (59.4 ng/g ww), mutton (51.4 ng/g ww), highland barley (46.3 ng/g ww), and yak beef (31.7 ng/g ww). For MCCPs, the highest concentrations were also detected in Tibetan butter (319.5 ng/g ww), followed by mutton (181.9 ng/g ww), vegetables (127.0 ng/g ww), yak beef (71.2 ng/g ww), and highland barley (30.3 ng/g ww). The predominant congener profiles of SCCPs were C13Cl7-8 in mutton and yak beef, C10Cl7-8 in Tibetan butter, and C10-11Cl6-7 in highland barley and vegetables. The predominant congener profiles of MCCPs were C14Cl7-9 in all sample types. Combined with our previous results of free-range chicken eggs, the median estimated daily intakes (EDIs) of SCCPs and MCCPs via diet for Tibetan rural adults and children was estimated to be 728.8 and 1853.9 ng/kg bw/day and 2565.6 and 5952.8 ng/kg bw/day, respectively. In the worst scenario, MCCPs might induce potential health risks for rural Tibetan population. To our knowledge, this is the first systematic dietary exposure research of SCCPs and MCCPs in the remote rural areas.

Bee colonies map the short- and medium-chain chlorinated paraffin contamination from the apiary environment

Chlorinated paraffins (CPs) are industrial chemicals that have potential adverse effects in the environment and on human health. This study investigated CPs in apiary environment, honeybees, and bee products from two rural areas of Beijing, China. The median concentrations of short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) were 22 and 1.6 ng/m3 in the ambient air, 1350 and 708 ng/g dry mass (dw) in bees, 1050 and 427 ng/g dw in flowers, 37 and 54 ng/g in honey, 78 and 53 ng/g dw in bee pollen, 36 and 30 ng/g dw in soil, and 293 and 319 ng/g dw in bee wax. C10Cl6-7 and C14Cl7-8 dominated SCCPs and MCCPs in these samples, respectively. The concentrations and distributions of CPs in samples from apiaries located in the two regions varied. Long-range transportation of air masses was identified as an important source of CPs in apiaries. A close relationship between CPs in bees and the apiary environment indicated that bees could act as bioindicators for CP contamination in the environment. A human health risk assessment found that there were low risks for adults and children exposed to CPs through consumption of honey and pollen from the studied regions.

Remarkable Contamination of Short- and Medium-Chain Chlorinated Paraffins in Free-Range Chicken Eggs from Rural Tibetan Plateau

Rapid social-economic development introduces modern lifestyles into rural areas, not only bringing numerous modern products but also new pollutants, such as chlorinated paraffins (CPs). The rural Tibetan Plateau has limited industrial activities and is a unique place to investigate this issue. Herein we collected 90 free-range chicken egg pool samples across the rural Tibetan Plateau to evaluate the pollution status of CPs. Meanwhile, CPs in related soils, free-range chicken eggs from Jiangxi, and farmed eggs from markets were also analyzed. The median concentrations of SCCPs (159 ng g-1 wet weight (ww)) and MCCPs (1390 ng g-1 ww) in Tibetan free-range chicken eggs were comparable to those from Jiangxi (259 and 938 ng g-1 ww) and significantly higher than those in farmed eggs (22.0 and 81.7 ng g-1 ww). In the rural Tibetan Plateau, the median EDI of CPs via egg consumption by adults and children were estimated to be 81.6 and 220.2 ng kg-1 bw day-1 for SCCPs and 483.4 and 1291 ng kg-1 bw day-1 for MCCPs, respectively. MCCPs might pose potential health risks for both adults and children in the worst scenario. Our study demonstrates that new pollutants should not be ignored and need further attention in remote rural areas.

Characterization of short-, medium-, and long-chain chlorinated paraffins in Tibetan butter and implications for local human exposure

Since short-chain chlorinated paraffins (SCCPs) were severely restricted under the Stockholm Convention in 2017, a shift to the production of other chlorinated paraffin (CP) groups has occurred, particularly medium-chain (MCCPs) and long-chain CPs (LCCPs), although data on the latter are sparser in the literature. This study described the occurrence of three types of CPs in butter samples from six livestock milk sources across 15 sites in Tibet. The median levels of SCCPs, MCCPs, and LCCPs were 132, 456, and 13.2 ng/g lipid, respectively. The detection rate of 97.6% suggests that LCCPs can be transmitted to humans. Thus, all CPs, regardless of their chain length and degree of chlorination, should be treated with caution. The differences in concentration were mainly caused by dynamic wet deposition and thermodynamic cold-trapping effects across the different districts. The homolog pattern of CPs varied widely across livestock species, which was attributed to the diverse impacts of the physicochemical properties of the homologs, especially the heterogeneity in the uptake and transfer of CPs across different organisms. Under three different criteria, the health risks associated with the daily intake of SCCPs should not be neglected, especially considering other intake exposure pathways and the degradation of longer-carbon-chain monomers.

Calibration and Application of PUF Disk Passive Air Samplers To Assess Chlorinated Paraffins in Ambient Air in Australia, China, and Vietnam

Ambient air samples were collected in Brisbane (Australia), Dalian (China), and Hanoi (Vietnam) during Mar 2013-Feb 2018 using polyurethane foam based passive air samplers. A sampling rate calibration experiment was conducted for chlorinated paraffins (CPs, i.e., short-chain, medium-chain, and long-chain CPs), where the sampling rates were 4.5 ± 0.7, 4.8 ± 0.3, and 4.8 ± 2.1 m3 day-1 for SCCPs, MCCPs, and LCCPs, respectively. The atmospheric concentration of CPs was then calculated and the medians of ∑CPs were 0.079, 1.0, and 0.89 ng m-3 in Brisbane, Dalian, and Hanoi, respectively. The concentration of CPs in Brisbane's air remained at low levels, with no significant differences observed between the city background site and the city center site, indicating limited usage and production of CPs in this city. The highest concentration of MCCPs was detected in Dalian, while the highest concentration of SCCPs was detected in Hanoi. A decrease of SCCP concentration and an increase of MCCPs' were found in Brisbane's air from 2016 to 2018, while increasing trends for both SCCPs and MCCPs were observed in Dalian. These results indicated impacts from different sources of CPs in the investigated cities.

An alkali-enhanced subcritical water treatment strategy of short-chain chlorinated paraffins: Dechlorination and hydrocarbons recovery

As persistent organic pollutants, short-chain chlorinated paraffins (SCCPs) have attracted wide attention in the field of environmental health risk and hazardous waste management. Efficient dechlorination of high content of SCCPs in plastic waste is the committed step for its detoxification and safety treatment. In this study, a high-efficiency and low-temperature process for dechlorination and hydrocarbons recovery from typical SCCPs (52#SCCPs) by subcritical water (SubCW) with alkali enhancer was developed. The introduction of alkali enhancer in the SubCW process had significantly enhanced effect on the dechlorination of 52#SCCPs, and the order of the enhanced effect of alkali enhancer for the dechlorination was NaOH > Na2CO3 > NaHCO3 > NH3·H2O > KOH. The dechlorination behaviors of 52#SCCPs in the NaOH-enhanced SubCW process were studied systematically under different conditions including temperature, residence time, alkali concentration, and volume ratio. The results showed that high-efficiency dechlorination (100 %) of 52#SCCPs could be achieved by the NaOH-enhanced SubCW process at low temperature for a short time (250 °C, 5 min). All of the chlorine released from the molecular chain of 52#SCCPs was transferred to the aqueous phase in the form of inorganic chlorine. The continuous HCl elimination reaction was the primary dechlorination mechanism for 52#SCCPs in the NaOH-enhanced SubCW process. After the dechlorination of 52#SCCPs, high value-added hydrocarbons such as 2,4-hexadiyne (31.74 %) could be obtained. The alkali-enhanced SubCW process proposed in this study is believed to be an environmentally friendly and high-efficiency method for dechlorination/detoxification and resource recovery of SCCPs.

Short- and medium-chain chlorinated paraffins in agricultural and industrial soils from Shanghai, China: surface and vertical distribution, penetration behavior, and health risk assessment

The widespread contamination of chlorinated paraffins (CPs) of the soil environment has raised global concern due to their highly persistent and toxic properties. However, little information is available regarding these industrial toxicants' spatial-vertical distribution and penetration potentials. In this study, short- and medium-chain chlorinated paraffins (SCCPs and MCCPs, respectively) were analyzed in pooled surface and core soils (0-45 cm) samples collected from agricultural and industrial areas in Shanghai. ∑SCCP concentrations in agricultural and industrial surface soils ranged from 52.6 to 237.6 and 98.3 to 977.1 ng/g dry weight (dw), respectively. ∑MCCP levels were comparatively higher and ranged from 417.2 to 1690.8 and 370.9 to 10,712.7 ng/g dw in agricultural and industrial soils, respectively. C10Cl5-10 SCCPs and C14-15Cl5-7 MCCPs were the predominant homologues in all samples. Analysis of the soil vertical profiles revealed that MCCP concentrations decreased significantly with depth (P < 0.01). SCCPs more efficiently penetrated into the soils than MCCPs because of their higher water solubility and less octanol-water partition coefficient (Kow) values. A preliminary risk assessment suggested no potential health risks caused by non-dietary exposure. The daily exposure doses of CPs via ingestion were significantly (P < 0.01) higher for children (5.41 ± 2.11 × 10-3 and 1.68 ± 1.03 × 10-2 μg kg-1 day-1) and adults (2.56 ± 0.99 × 10-4 and 7.94 ± 4.87 × 10-4 μg kg-1 day-1) than dermal permeation exposure. Furthermore, CPs at current levels posed low ecological risks (0.1 ≤ RQ < 1) according to the risk quotient model. This study enhanced our understanding of the fates and behaviors of CPs in the terrestrial environment.

Detection of trace chlorine pollutants in recycled pulp using gas chromatography-tandem mass spectrometry with response surface-optimized carbon structure online catalysis

RATIONALE

Chlorinated aromatics and alkanes are widely used for their flame retardancy, but they need to be monitored when used in recycled pulp. This paper reports the use of palladium acetate/activated carbon (Pa/Ac) activated by nitric acid as an online catalyst to determine chlorinated aromatics and chlorinated alkanes in recycled paper products using gas chromatography-tandem mass spectrometry (GC-MS/MS), which significantly improves the sensitivity of the method and remarkably lowers the detection limits.

METHODS

The Pa/Ac catalyst was prepared using a self-made catalytic device and used as key to the online catalytic conversion of target chlorinated aromatic hydrocarbons and chlorinated alkanes for GC-MS/MS analysis. The response surface model was used to optimize catalytic conditions. Then GC-MS/MS in the multireaction monitoring mode with online catalysis was applied for the analysis of polychlorinated biphenyls, polychlorinated terphenyls, polychlorinated naphthalene, and chlorinated paraffins (CP) in recycled paper products.

RESULTS

Compared with traditional methods, the Pa/Ac catalyst can transform chlorinated aromatic hydrocarbons into aromatic hydrocarbons through dechlorination hydrogenation, thus lowering the detection limit of the GC-MS/MS method significantly. It can transform paraffin chloride into the corresponding alkane to better distinguish short-chain, medium-chain, or long-chain CPs. Online catalytic conversion significantly improved the sensitivity and reproducibility (88.7%-113.1%) of the method. Tissue samples with various concentration levels of chlorinated aromatics and chlorinated alkanes were tested. The linearity range of the reduced target compounds in the reduction product solution was 0.02-1.00 μg/ml (R2  > 0.995). The quantitative detection limit was 0.03-0.05 μg/kg, and relative standard deviation was less than 6.9%.

CONCLUSION

This study was the first to introduce the Pa/Ac catalytic device as an online catalytic unit in the determination of chlorinated aromatics and chlorinated alkanes using the GC-MS/MS method. The target compounds were converted into alkanes and aromatic hydrocarbons with unchanged carbon structures, and the method could achieve a low detection limit with no need for high-end methods such as GC-chemical ionization ion source (CI)-MS or high-resolution mass spectrometry. These methods are suitable for the determination of chlorine pollutants in recycled paper and its raw materials.

Human exposure to short-chain chlorinated paraffins and organophosphate flame retardants in relation to paired multiple sources

In this study, the levels and distributions of short chain chlorinated paraffins (SCCPs) and organophosphate flame retardants (OPFRs) were determined in 10-88 aged human serum/hair and their paired multiple exposure sources, including one-day composite food, drinking water, and house dust. The average concentration of SCCPs and OPFRs were respectively 6313 and 176 ng/g lipid weight (lw) in serum, 1008 and 108 ng/g dry weight (dw) in hair, 1131 and 27.2 ng/g dw in food, not detected and 45.1 ng/L in drinking water, and 2405 and 864 ng/g in house dust. The levels of SCCPs in serum of adults were significantly higher than those of juvenile (Mann-Whitney U test, p < 0.05), whereas gender showed no statistically significant difference in SCCPs and OPFRs levels. In addition, there were significant relationships of OPFR concentrations between serum and drinking water as well as hair and food using the multiple linear regression analysis, whereas no correlation was observed for SCCPs. Based on the estimated daily intake, the major exposure pathway for SCCPs was food, while for OPFRs, it was food and drinking water with three order magnitude safety margin.

Characterization of short-, medium- and long-chain chlorinated paraffins in ambient PM2.5 from the Pearl River Delta, China

Research on the environmental occurrence of long-chain chlorinated paraffins (LCCPs) in ambient fine particulate matter (PM_2.5) is still scarce. In the present study, short-chain chlorinated paraffins (SCCPs), medium-chain chlorinated paraffins (MCCPs) and LCCPs were simultaneously quantified and profiled in PM_2.5 samples collected from 96 primary or secondary schools in the Pearl River Delta of South China. SCCPs, MCCPs and LCCPs were detected in higher than 90% samples with concentrations in the range of 0.832-109, 1.02-110, and 0.173-17.4 ng/m³, respectively. The dominant congener groups of SCCPs, MCCPs and LCCPs were C₁₃Cl_6-8, C₁₄Cl_7-8, and C₁₈Cl_7-9, respectively. The concentrations of SCCPs and MCCPs were higher in summer than in winter, while an opposite seasonal trend was observed for LCCPs. Principal components analysis showed there were seasonal variations in the congener group patterns with C₁₃Cl_6-7 and C₁₄Cl₇ more abundant in summer than in winter_. Concentrations of CPs also exhibited slight spatial variations. Exposure risk assessment based on different age groups suggested exposure to PM_2.5-associated CPs would not pose significant health risk. The present study expands the existing knowledge of CPs contamination in atmospheric environment.

Short and medium-chain chlorinated paraffins in indoor dust from a multistory residential building in Beijing, China: Vertical distribution and potential health risks

In this study, we conducted a preliminary investigation of the vertical distribution and potential health risks of short and medium-chain chlorinated paraffins (SCCPs and MCCPs) in indoor dust from a multistory residential building in Beijing, China. Forty-eight SCCP and MCCP congener groups in dust from different floors of the multistory residential building were determined by two-dimensional gas chromatography coupled with electron capture negative ionization mass spectrometry. The concentration ranges for SCCPs and MCCPs in the dust samples were 0.0239-207 μg/g and 0.135-2903 μg/g, respectively. MCCPs were the dominant group, on average accounting for 76.8 % of ∑CPs. Generally, the concentrations of both SCCPs and MCCPs greatly decreased as the floor level increased, which indicated that the CP contamination was attributed to exogenous atmospheric transport and deposition. C₁₃Cl_7-8 and C₁₄Cl_7-8 were the dominant SCCP and MCCP congener groups, possibly indicating the use of industrial CP-52 products was the main source of CPs. In the worst-case scenario using the maximum concentrations of CPs, the daily intake of SCCPs for toddlers was of the same order of magnitude as the reference dose. It should be noted that CPs exposure may be more serious when indoor decorations, furniture, and various plastic products are taken into consideration. Overall, more attention should be paid to CPs exposure and control measures in high-rise buildings.

The impact of three related emission industries on regional atmospheric chlorinated paraffins pollution

Identifying the contributions of various chlorinated paraffins (CPs) sources in the environment plays an important practical role in the prevention and control of the CPs contamination. However, little is known about how main CP-related emission industries affect the regional atmospheric characteristics of CPs, including CP products industry, metal working industry, and polyvinyl chloride (PVC) industry. In this study, 60 passive air samples were collected from five typical cities in Henan Province, China, which had serious CP pollution and different structures of CP-related emission industry. Short chain CPs (SCCPs) and medium chain CPs (MCCPs) were detected in all samples in concentrations ranging of 2.6-7.7 × 10² and 2.1-4.3 × 10² ng m^-3, respectively, which were higher than those in most reports. Moreover, Luoyang (LY) is different from other cities, showing a relatively severe MCCP contaminations. The CP pollution characteristics between different cities are obviously affected by the proportion of local CP-related industries. According to the results of cluster heatmaps, the local CP-related emission industrial structure had a greater impact on MCCPs pollution than SCCPs. Additionally, the contribution of metal working industry was beyond that of PVC production industry and CP products industry.

Dietary exposure and risk assessment of chlorinated paraffins in roots and rhizomes of traditional Chinese medicine herbs

Traditional Chinese medicine (TCM) provides therapeutic and health care effects through dietary intake. Owing to the susceptibility of plants to contaminations, a risk assessment system is urgently needed to ensure the safe use of TCMs. In this study, the contamination levels and risks associated with the dietary intake of short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) were investigated in six kinds of frequently-used TCM herbs. The concentrations varied from 144.4 to 1527.8 ng·g-1 dw for SCCPs and non-detect to 1214.1 ng·g-1 dw for MCCPs, with mean values of 551.5 and 259.8 ng·g-1 dw, respectively. A geographic distribution analysis indicated that the concentrations of CPs in TCMs were mainly associated with their levels of contamination in the ambient environment. Carbon atom-chlorine congener profiles of CPs were dominated by C10Cl7-8 and C14Cl7-8 congeners, accounting for 20.1% and 32.4% of the total SCCP and MCCP concentrations, respectively. Principal component analysis indicated that the TCM species might be the main factor influencing the accumulation of SCCPs congeners. Finally, a risk assessment reveals that the estimated daily intake and margin of exposure were far below levels that might pose a health risk, indicating an acceptable dietary intake of SCCPs and MCCPs in the studied TCMs. This is the first report of CPs in the TCM herbs and the obtained results are expected to aid in future evaluation of the quality of TCMs and ensuring diet and drug safety.

Occurrence, Distribution and Health Risk of Short-Chain Chlorinated Paraffins (SCCPs) in China: A Critical Review

With being listed in the Stockholm Convention, the ban on short-chain chlorinated paraffins (SCCPs) has been put on the agenda in China. Based on the literature over the past decade, this study comprehensively analyzed the occurrence, distribution of and human exposure to SCCPs in China, aiming to provide a reference for the changes in SCCPs after the ban. SCCPs were ubiquitous in environmental matrices, and the levels were considerably higher than those in other countries. SCCPs from the emission region were 2–4 orders of magnitude higher than those in the background area. Environmental processes may play an important role in the SCCP profiles in the environment, and C10 and Cl6 were identified as potential factors distinguishing their spatial distribution. River input was the dominant source in the sea areas, and atmospheric transport was the main source in the remote inland areas. Ingestion and dermal absorption and food intake may pose potential risk to residents, especially for children and infants. More studies are needed on their temporal trend, source emission and environmental degradation. The enactment of the restriction order will have a great impact on China’s CP industry; nevertheless, it will play a positive role in the remediation of SCCP pollution in the environment.

Biotic and Abiotic Transformation Pathways of a Short-Chain Chlorinated Paraffin Congener, 1,2,5,6,9,10-C10H16Cl6, in a Rice Seedling Hydroponic Exposure System

In this work, a typical congener of short-chain chlorinated paraffins (SCCPs) with six chlorine atoms (CP-4, 1,2,5,6,9,10-C₁₀H₁₆Cl₆, 250 ng/mL) was selected to elaborate the comprehensive environmental transformation of SCCPs in rice seedling exposure system. CP-4 was quickly absorbed, translocated, and phytovolatilized by seedlings with a small quality of CP-4 (5.81-36.5 ng) being detected in the gas phase. Only 21.4 ± 1.6% of an initial amount (10,000 ng) of CP-4 remained in the exposure system at the end of exposure. Among the transformed CP-4, some were attributed to the degradation of the rhizosphere microorganism (9.1 ± 5.8%), root exudates (2.2 ± 4.2%), and abiotic transformation (3.0 ± 2.8%) that were proved by several transformation products found in the root exudate exposure groups and unplanted controls, and a majority was phytotransformed by rice seedlings. Here, 61 products were determined through complex transformation pathways, including multihydroxylation, -HCl elimination, dechlorination, acetylation, sulfation, glycosylation, and amide acid conjugation. The acetylated and amide acid conjugates of CPs were first observed. Phase I and Phase II phytometabolic reactions of CPs were found intertwining. These findings demonstrate that multiactive transformation reactions contribute to the overlook of CPs accumulated in plants and are helpful for the environmental and health risk assessments of SCCPs in agricultural plants.

Occurrence, congener patterns, and potential ecological risk of chlorinated paraffins in sediments of Yangtze River Estuary and adjacent East China Sea

Chlorinated paraffins (CPs) are high production volume chemicals with immense scientific research interest due to their wide distribution, persistence, toxicity, and bioaccumulation potential. In this study, 87 surface sediments were collected from the Yangtze River Estuary (YRE) and the adjacent East China Sea (ECS). We investigated the concentrations, spatial distribution, and composition profiles of short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) using ultra-high-performance liquid chromatography coupled with Orbitrap Fusion Tribrid mass spectrometry. The sedimentary concentrations of SCCPs and MCCPs ranged from 2.85 to 94.7 ng·g^-1 (median 13.7 ng·g^-1) and 3.33 to 77.8 ng·g^-1 (median 13.3 ng·g^-1), respectively. Higher CP concentrations were found in YRE sediments. The values decreased away from the location, implying a direct influence of the Yangtze River. The SCCP concentrations were higher than those of MCCPs in most sediment samples. Overall, the predominant homologs were C₁₃Cl_5-7 and C₁₄Cl_6-8 for MCCPs and SCCPs, respectively. Overall, the sediment-dwelling organisms in the region are susceptible to low ecological risks.

Passive sampling of chlorinated paraffins by silicone: Focus on diffusion and silicone-water partition coefficients

Short-chain chlorinated paraffins (SCCPs) are under regulation through the European Water Framework Directive and were recently classified as POPs. Consecutively, the increasing use of middle-chain chlorinated paraffins (MCCPs) becomes of growing concern. Knowledge on the occurrence of chlorinated paraffins (CPs) is still scarce particularly in water phase. To achieve sufficient method sensitivity, the passive sampling approach, acting as a relevant alternative to usual grab sampling, has been considered only very recently for the monitoring of CPs in water. The present work aimed at determining the diffusion coefficients in silicone (D_s) and the silicone-water partition coefficients (K_sw) of various CP groups, having different chlorine contents and carbon chain lengths, in four commercial CP mixtures. Log D_s (-10.78 to -10.21) was found to vary little and to be high for the groups of CPs studied. Thus, their uptake in silicone is controlled by the water boundary layer, which allows to consider the release of performance and reference compounds for in-field estimation of the sampling rate. Moreover, CPs partitioned strongly towards silicone rubbers. Both the chlorination degree and the carbon chain length of CPs cause large uncertainties in the partitioning between silicone and water (log K_sw between 4.85 and 6.30), indicating that instead of an average value, differentiated K_sw should be used to estimate aqueous CPs more accurately. Even so, the probable influence of chlorine atoms position on polarity and partitioning may be an argument for favoring sampling in the kinetic stage.

Guidance on the Application of Polyurethane Foam Disk Passive Air Samplers for Measuring Nonane and Short-Chain Chlorinated Paraffins in Air: Results from a Screening Study in Urban Air

This study provides guidance on using polyurethane foam-based passive air samplers (PUF-PASs) for atmospheric nonane chlorinated paraffins (C₉-CPs) and short-chain CPs (SCCPs) and reports SCCP concentrations in air in the Greater Toronto Area (GTA), Canada. We estimated the partition coefficients between PUF and air (K_PUF-A) and between octanol and air (K_OA) for C₉-CP and SCCP congeners using the COSMO-RS method, so that PUF disk uptake profiles for each formula group could be calculated. We then measured SCCP concentrations in PUF disk samples collected from distinct source sectors in urban air across the GTA. Concentrations in samplers were used to calculate C₉-CP and SCCP concentrations in air and the PUF disk uptake profiles revealed that time-weighted linear phase sampling was possible for congeners having log K_OA values greater than 8.5. The highest SCCP concentrations, with an annual average concentration of 35.3 ng/m³, were measured at the industrial site, whereas lower but comparable SCCP concentrations were found in residential and background sites, with annual averages of 7.73 and 10.5 ng/m³, respectively. No consistent seasonal variation in SCCP concentrations was found in the six distinct source sectors. Direct measurements of K_PUF-A and K_OA values as a function of temperature could be used to increase accuracy in future studies.

Medium- and Short-Chain Chlorinated Paraffins in Mature Maize Plants and Corresponding Agricultural Soils

For the most complex artificial chlorinated environmental contaminants, much less is known for medium-chain CPs than short-chain CPs. In this research, the spatial distributions of MCCPs and SCCPs in farmland soil and maize leaves near a CP production facility were found marginally influenced by seasonal winds. The levels of ∑MCCPs and ∑SCCPs were in the ranges of <1.51-188 and 5.41-381 ng/g dw for soils; and 77.6-52930 and 119-61999 ng/g dw for maize leaf, respectively. Bioaccumulation and tissue distributions of the CPs within maize plants were specifically analyzed. Most of the CPs were contained in the tissues directly exposed to airborne CPs. Though the estimated risk of CPs to humans through ingestion of kernels appears to be minimal, the edible safety of MCCPs in maize plants for cattle was nearly in the designated range of adverse effects. To our knowledge, this is the first report on bioaccumulation of CPs in mature maize plants, especially in the parts eaten by humans and domestic animals. It provides a baseline reference to the edible risks of CPs in agricultural food plants and alerts us to the problematic environmental behavior of MCCPs, a probable future replacement for SCCPs commercially.

Long-Term Investigation of the Temporal Trends and Gas/Particle Partitioning of Short- and Medium-Chain Chlorinated Paraffins in Ambient Air of King George Island, Antarctica

The presence of anthropogenically emitted chlorinated paraffins (CPs) has been reported in the pristine regions, providing evidence of their long-range transport. This study comprehensively analyzed the short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) in both gas and particle phases at King George Island, West Antarctica (the Chinese Great Wall Station), from 2014 to 2018. The atmospheric levels of CPs ranged between 71.4 and 4230 pg/m³, with an increasing temporal trend during the sampling time. Three different models (J-P model, H-B model, and L-M-Y model) were built to estimate the progress of gas/particle partitioning of CPs at the measurement site. Furthermore, we compared the measured data of the gas/particle partitioning with the data estimated using three different models. We found that the steady-state model (L-M-Y model) was more suitable for investigating the gas/particle partitioning of CPs instead of equilibrium state models (J-P model and H-B model). The result indicated that steady-state approximation rather than the equilibrium state represents the most predominant contribution to the transport of CPs to the Antarctic region. The steady-state further made it conducive to sustaining the levels of CPs for a more extended period in the atmosphere of West Antarctica.

Long-range atmospheric transport and alpine condensation of short-chain chlorinated paraffins on the southeastern Tibetan Plateau

Pristine alpine regions are ideal regions for investigating the long-range atmospheric transport and cold trapping effects of short chain chlorinated paraffins (SCCPs). The concentrations and alpine condensation of SCCPs were investigated in lichen samples collected from the southeastern Tibetan Plateau. The concentrations of SCCPs ranged from 3098 to 6999 ng/g lipid weight (lw) and appeared to have an increasing trend with altitude. For congeners, C₁₀ dominated among all the congener groups. The different environmental behavior for different congener groups was closely related to their octanol-air partition coefficient (K_oa). C₁₀ congeners showed an increasing trend with altitude, whereas C₁₃ congeners were negatively correlated with altitude. Volumetric bioconcentration factors (BCF) of SCCPs reached 8.71 in lichens, which were higher than other semivolatile organic compounds (SVOCs) such as organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and hexabromocyclododecane (HBCD). These results suggested that SCCPs were prone to accumulate in the lichen from the air and provided evidence for the role of lichens as a suitable atmospheric indicator in the Tibetan Plateau.

Short-chain chlorinated paraffins in soils indicate landfills as local sources in the Tibetan Plateau

Background contamination levels of contemporary persistent organic pollutants (POPs) may be elevated due to local discharges, and hence it is of high importance to assess and monitor them in alpine and Polar Regions. This study investigated the role of waste disposal in the Tibetan plateau as the local source of short-chain chlorinated paraffins (SCCPs). SCCPs were determined in soils from the urban landfill and rural dumpsites, with a concentration range of 56.8-1348 ng/g dw. The gradient descent of SCCP levels from Lhasa landfill to the surrounding soils with increasing distances suggested a significant SCCP release from waste disposal. The transport pattern was well fitted by the Boltzmann equation after normalization in terms of soil organic carbon contents. Compared to the landfill cells closed in early years, the recently closed cells contained higher concentrations but lower proportions of the short-chain congener groups, likely reflecting the SCCP use history in Tibet. In open-burning dumpsites, higher SCCP levels and dominance of lighter congener groups indicates that such crude waste treatment process might cause an extra release of volatile SCCPs. This study elucidates local SCCP inputs to the background environment, and demonstrates that both urbanization and badly-managed landfill have been contributing to the presence of contemporary POPs in the Tibetan Plateau.

Terrestrial mercury transformation in the Tibetan Plateau: New evidence from stable isotopes in upland buzzards

Understanding the geochemical cycle of mercury (Hg) in the high-altitude Tibetan Plateau is of great value for studying the long-range transport of Hg. Herein, speciation and isotopic compositions of Hg in the muscle and feathers of upland buzzards (Buteo hemilasius) were studied to trace the terrestrial transformation of Hg in the Tibetan Plateau. Very low Hg content and relatively low δ²⁰²Hg values (feather: -0.77 ± 0.50‰, n = 9, muscle: -1.29 ± 0.29‰, n = 13, 1SD) were observed in upland buzzards. In contrast, the Δ¹⁹⁹Hg values could be as high as 2.89‰ in collected samples. To our knowledge, this is the highest Δ¹⁹⁹Hg value reported in avian tissues. Moreover, upland buzzards showed significantly different Δ¹⁹⁹Hg values from fish collected from the same region, suggesting different generation and transformation processes of methylmercury (MeHg) in terrestrial and aquatic ecosystems. We speculated that different percentages of Hg undergoing photochemical reactions and contributions of atmospheric MeHg were possible reasons for observed differences. The results provide new clues for different circulation histories of Hg in terrestrial and aquatic ecosystems, which will be critical for further study of geochemical cycle and ecological risk of Hg in the environment.

Passive air sampling for semi-volatile organic chemicals

During passive air sampling, the amount of a chemical taken up in a sorbent from the air without the help of a pump is quantified and converted into an air concentration. In an equilibrium sampler, this conversion requires a thermodynamic parameter, the equilibrium sorption coefficient between gas-phase and sorbent. In a kinetic sampler, a time-averaged air concentration is obtained using a sampling rate, which is a kinetic parameter. Design requirements for kinetic and equilibrium sampling conflict with each other. The volatility of semi-volatile organic compounds (SVOCs) varies over five orders of magnitude, which implies that passive air samplers are inevitably kinetic samplers for less volatile SVOCs and equilibrium samplers for more volatile SVOCs. Therefore, most currently used passive sampler designs for SVOCs are a compromise that requires the consideration of both a thermodynamic and a kinetic parameter. Their quantitative interpretation depends on assumptions that are rarely fulfilled, and on input parameters, that are often only known with high uncertainty. Kinetic passive air sampling for SVOCs is also challenging because their typically very low atmospheric concentrations necessitate relatively high sampling rates that can only be achieved without the use of diffusive barriers. This in turn renders sampling rates dependent on wind conditions and therefore highly variable. Despite the overall high uncertainty arising from these challenges, passive air samplers for SVOCs have valuable roles to play in recording (i) spatial concentration variability at scales ranging from a few centimeters to tens of thousands of kilometers, (ii) long-term trends, (iii) air contamination in remote and inaccessible locations and (iv) indoor inhalation exposure. Going forward, thermal desorption of sorbents may lower the detection limits for some SVOCs to an extent that the use of diffusive barriers in the kinetic sampling of SVOCs becomes feasible, which is a prerequisite to decreasing the uncertainty of sampling rates. If the thermally stable sorbent additionally has a high sorptive capacity, it may be possible to design true kinetic samplers for most SVOCs. In the meantime, the passive air sampling community would benefit from being more transparent by rigorously quantifying and explicitly reporting uncertainty.

Trophic Magnification of Short- and Medium-Chain Chlorinated Paraffins in Terrestrial Food Webs and Their Bioamplification in Insects and Amphibians during Metamorphosis

Studies on the biomagnification of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in terrestrial ecosystems and their bioamplification during metamorphosis in insects and amphibians are scarce. Therefore, this study sought to characterize the occurrence and trophic dynamics of SCCPs and MCCPs in an insect-dominated terrestrial food web in an e-waste recycling site in South China. Median ∑SCCPs and ∑MCCPs concentrations in the organisms ranged from 2200 to 34 000 ng/g lipid weight and from 990 to 19 000 ng/g lipid weight, respectively. The homologue profiles of CPs in the predators were distinct from those in insects, presenting more short chain-high chlorinated congeners (C_10-12Cl_8-10). The trophic magnification factors (TMFs) of ∑SCCPs and ∑MCCPs were 2.08 and 2.45, respectively, indicating biomagnification in the terrestrial food web. A significant positive relationship between the TMFs and octanol-air partition coefficients was observed. TMFs were also positively correlated with chlorination degree but did not correlate with carbon chain length. Nonlinear correlations between metamorphosis-associated bioamplification and the octanol-water partition coefficients of SCCPs and MCCPs were observed for insects, whereas negative linear correlations were observed for amphibians, which suggested species-specific alterations to the chemicals during metamorphosis.

Metabolism of SCCPs and MCCPs in Suspension Rice Cells Based on Paired Mass Distance (PMD) Analysis

Short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) are mixtures of complex chemical compounds with intensive usage. They are frequently detected in various environmental samples. However, the interaction between CPs and plants, especially the biotransformation behaviors of CPs within plants, is poorly understood. In this study, 1,2,5,6,9,10-hexachlorodecane (CP-4, a typical standard of individual SCCP congeners) and 52%-MCCP (a commercial mixture standard of MCCPs with 52% chlorine content by mass) were selected as representative chemicals to explore the metabolic behaviors of SCCPs and MCCPs using suspension rice cell culture exposure systems. Both 79.53% and 40.70% of CP-4 and 52%-MCCP were metabolized by suspension rice cells, respectively. A complementary suspected screening strategy based on the pair mass distances (PMD) analysis algorithm was used to study the metabolism of CPs mediated by the plant cells. Forty and 25 metabolic products for CP-4 and 52%-MCCP, respectively, were identified, including (multi-) hydroxylation, dechlorination, -HCl- elimination metabolites, (hydroxylation-) sulfation, and glycosylation conjugates. Here, we propose a comprehensive metabolic molecular network and provide insight on degradation pathways of SCCPs and MCCPs in plants for the first time, aiding in further understanding of the transformation behaviors of CPs.

Short- and medium-chain chlorinated paraffins in multi-environmental matrices in the Tibetan Plateau environment of China: A regional scale study

Research on the environmental fate and behavior of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs, respectively), especially in high-altitude remote mountain areas, has rarely been conducted. In this study, the distribution and profiles of SCCPs and MCCPs in soils, barks, needles, lichens, and mosses in the Tibetan Plateau area were investigated during the period from 2010 to 2016. The total CP concentrations in soils, barks, needles, lichens, and mosses increased with increasing altitude from 1983 to 5147 m a.s.l. (above sea level), covering a range of 1843.5 km × 370.6 km. Generally, the mean SCCP levels were higher than mean MCCP levels in different environmental matrices. Moreover, as-obtained linear relationships between CP concentrations in different environmental matrices and altitudes (p < 0.05) indicated that the mountain cold-trapping could affect the presence and congener patterns of both SCCPs and MCCPs in the Tibetan Plateau environment. C_10-11 and C₁₄ congener groups were found to be the dominant groups in SCCPs and MCCPs in the environmental samples, respectively. Finally, the back-trajectory model was employed to reveal the differences of the potential sources in different regions of the Tibetan Plateau.

Spatial variation of short- and medium-chain chlorinated paraffins in ambient air across Australia

Atmospheric levels of chlorinated paraffins (CPs) at five remote, six rural and four urban sites in Australia were measured using XAD-2 passive air samplers (XAD-PAS). While long-chain CP (LCCP, C_>17) levels were below method detection limits (MDLs), short-chain CPs (SCCPs, C_10-13) and, for the first time, medium-chain CPs (MCCPs, C_14-17) and CPs with a carbon chain length of nine (CP-C9) were found at many sites (88%, 81% and 88%, respectively) across the Australian continent, representing a range of environmental conditions. Applying preliminary sampling rates of the XAD-PAS for CPs, gaseous CP levels in Australian air were <MDL-1.3 and <MDL-1.8 ng/m³ for ΣSCCPs and ΣMCCPs, respectively, with a significant decreasing trend from more densely to less densely populated areas. Atmospheric median levels in this study (0.37 and 0.47 ng/m³ for SCCPs and MCCPs, respectively) were at the lower end of the median range (0.32-10 and 3.0-4.2 ng/m³ for SCCPs and MCCPs, respectively) reported for CPs at predominantly urban or industrial sites elsewhere (apart from China and extremely remote sites such as Antarctica). Principal component analysis matched the SCCP and MCCP congener group patterns in samples with those found in commercial mixtures, indicating a prevalence of less chlorinated congener groups in the Australian atmosphere. Information about the Australian production, use and disposal of CPs as well as their levels in other environmental matrices, including humans, is needed for assessing their emissions, behaviour, fate and potential exposure.

Advances in Studies on Toxic Effects of Short-Chain Chlorinated Paraffins (SCCPs) and Characterization of Environmental Pollution in China

Short-chain chlorinated paraffins (SCCPs) were included in the Stockholm Convention in 2017. SCCPs have persistence, bioaccumulation, long-range environmental mobility and biological toxicity, significant toxicity to aquatic organisms, and potential carcinogenicity. Little study was on the progress research on the current environmental pollution in China. We reviewed the pollution conditions of SCCPs in air, soil, and water and their accumulation in food and organisms in China, especially for the contaminations of aquatic ecosystem. Meanwhile, we summarize the recent studies on the toxic effects and toxicological mechanisms of SCCPs on aquatic organisms and mammals. Finally, the further direction and trends for SCCP research were proposed. More efforts are necessary to conduct a comprehensive risk assessment and evaluate the relative importance of the various exposure routes.

New classes of organic pollutants in the remote continental environment - Chlorinated and brominated polycyclic aromatic hydrocarbons on the Tibetan Plateau

Halogenated polycyclic aromatic hydrocarbons are carcinogenic and ubiquitous environmental organic pollutants. The abundance and sources of these compounds have not been studied in remote environments. We collected and analyzed air, soil, lichen, and moss samples from the Tibetan Plateau. Concentrations of chlorinated polycyclic aromatic hydrocarbons were 0.78-4.16 pg/m³ in air, 3.11-297 pg/g in soil, 260-741 pg/g in lichens, and 338-934 pg/g in mosses. Concentrations of brominated polycyclic aromatic hydrocarbons were 0.15-0.59 pg/m³ in air, 0.61-72.3 pg/g in soil, 33.5-64.9 pg/g in lichens, and 20.5-72.5 pg/g in mosses. The dominant congeners were 9- and 2-chlorophenanthrene, 1-chloropyrene, 3-chlorofluoranthene, and 1-bromopyrene. We found correlations between congener concentrations in lichens and in air, and lichens effectively predicted near-ground atmospheric concentrations of the pollutants. The enrichment of photochemically stable compounds in high-altitude environments is influenced by their physicochemical properties. Principal component analysis with multivariate linear regression of chlorinated polycyclic aromatic hydrocarbons measured in lichens provided an assessment of the relative source contributions, and suggested that in Medog County of Tibetan Plateau, 48% was likely from long-range combustion sources, 26% was from local burning sources, and 26% was from photochemical formation.

Dietary exposure and risk assessment of short-chain chlorinated paraffins in supermarket fresh products in Jinan, China

Dietary intake is the major route for the exposure of residents to short-chain chlorinated paraffins (SCCPs). SCCPs are classified as persistent organic pollutants (POPs) by the Stockholm Convention since May 2017. This study assessed the general population's dietary exposure to SCCPs through supermarket products. Five food categories, which included 40 food species, were collected from five supermarkets in April 2019. The SCCP concentrations in all food matrices varied between 58.6 and 1977 ng g^-1 dry weight (dw), with the average and standard deviation (SD) value of 301 ± 379 ng g^-1 dw. Generally, the SCCP concentrations in animal-origin food matrices were higher than those in plant-origin food matrices. The C₁₀Cl₇ congeners were predominant among the congener groups of SCCPs. The proportion of C₁₀ congeners in the animal-origin food samples (29.8%) was lower than that in the plant-origin food samples (39.7%), and the C₁₃ congeners showed a contrasting result. The estimated daily intake (EDI) of SCCPs through dietary intake for the residents was 3109 ng kg^-1 day^-1, which is much lower than the standards of European Food Safety Authority (10 mg kg^-1 day^-1) for SCCPs. Risk assessment based on the supermarket foods indicated that SCCP exposure through dietary intake does not cause adverse effects to human health according to the margin of exposure (MOE).

Spatial distribution and profile of atmospheric short-chain chlorinated paraffins in the Yangtze River Delta

Research on the atmospheric occurrence of short chain chlorinated paraffins (SCCPs) in industrialized areas is scarce. In this study, we investigated the concentrations, profile, and spatial distribution of SCCPs in the highly industrialized and developed areas of the Yangtze River Delta (YRD) in China using polyurethane foam passive air samplers. Sampling was performed during two separate periods in 2011. The concentrations of atmospheric SCCPs ranged from 6.1 to 63 ng m^-3 in summer and 6.2-42 ng m^-3 in winter. The C₁₀ and C₁₁ groups were the predominant carbon groups in all the samples. Different congener patterns between summer and winter were found, indicating that congeners in the air in winter may be influenced by local and external sources. The highest level of SCCPs was found in Suzhou, which is a highly industrialized area with many manufactories including electronic industries and plastic factories. Higher levels of SCCPs were found in the air than polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ether (PBDEs), suggesting that the production and use of SCCPs were much higher than prohibited or restricted persistent organic pollutants (e.g., PCBs, OCPs, and PBDEs). Future studies should investigate the different sources of atmospheric SCCPs by conducting a comprehensive assessment of SCCP exposure.

Chlorinated Paraffins in Two Snake Species from the Yangtze River Delta: Tissue Distribution and Biomagnification

Very-short, short-, medium-, and long-chain chlorinated paraffins (vSCCPs, SCCPs, MCCPs, and LCCPs, respectively) were analyzed in different tissues of the terrestrial short-tailed mamushi (Gloydius brevicaudus) and the semi-aquatic red-backed rat snake (Elaphe rufodorsata) from the Yangtze River Delta, China. The total CP concentrations in liver, muscle, and adipose tissues in the two snake species were in the range of 2500-24 000, 4900-48 000, and 12-630 ng/g lw, respectively. Tissue burdens indicated that vSCCPs (C_6-9) and SCCPs (C_10-13) preferentially distributed to snake liver, while adipose was an important storage site and sink of MCCPs (C_14-17) and LCCPs (C_>18). On a lipid weight basis, vSCCPs and SCCPs were found in highest concentrations in red-backed rat snake liver and MCCPs and LCCPs in muscle, whereas for short-tailed mamushi, all CP groups were predominant in muscle, probably reflecting ecosystem/food web differences. Moreover, vSCCPs, SCCPs, MCCPs, and LCCPs were found to be biomagnified from black-spotted frogs to red-backed rat snakes with mean (maximum) biomagnification factors of 2.2 (3.4), 1.9 (3.7), 1.8 (2.8), and 1.7 (4.5), respectively. This is the first field study of biomagnification potential involving vSCCPs and LCCPs and highlights the need to include all CPs in studies.

Transformation of 1,1,1,3,8,10,10,10-octachlorodecane in air phase increased by phytogenic volatile organic compounds of pumpkin seedlings

Short chain chlorinated paraffins (SCCPs) are widely distributed persistent organic pollutants (POPs). Airborne chlorodecanes were hypothesized to be transformed by reactive phytogenic volatile organic compounds (PVOCs) in our previous work. To test this hypothesis, PVOCs of pumpkin (Cucurbita maxima x C. moschata) were collected and reacted with 1,1,1,3,8,10,10,10-octachlorodecane in the air phase of a sealed glass bottle under illumination for 10 days (reaction system I, simulating atmospheric reaction conditions with PVOCs). The reaction control group (reaction system II) was set at the same conditions but only had chlorodecane (without PVOCs) inside the bottle. Transformation of SCCPs in the air phase of reaction control group was unexpectedly found. Results showed that 1,1,1,3,8,10,10,10-octachlorodecane was transformed to a great extent to C₁₀Cl_5-8, C₉Cl_6-8, and C₈Cl_7-8 in the air phase after 10-d illumination in both with and without the presence of PVOCs, which is explained by carbon chain decomposition, dechlorination and chlorine rearrangement products of the parent SCCP. Those transformation processes were increased to some extent by the PVOCs from pumpkin seedlings. This study provides the first experimental data on atmospheric transformation of SCCPs and also the first evidence that plant emissions (PVOCs) can increase the transformation of SCCPs in air under light and experimental conditions. It provides new insight into the potential transformation and fate of CPs in the environment.

Polychlorinated Naphthalene Congener Profiles in Common Vegetation on the Tibetan Plateau as Biomonitors of Their Sources and Transportation

Polychlorinated naphthalenes (PCNs) are globally transported, carcinogenic, persistent organic pollutants (POPs) that were recently added to the Stockholm Convention with 184 parties. The Tibetan Plateau plays an important role in the global transportation and distribution of POPs. Knowledge of PCN sources and transportation on the Tibetan Plateau is important for their control globally. In this study, we quantified the congener-specific concentrations of PCNs in lichen, moss, soil, and air samples collected on the Tibetan plateau and found that common lichens were effective biomonitors for predicting atmospheric PCNs in this area. The physiochemical properties of the PCNs, the temperatures, and the lichen lipid contents were identified as important factors influencing PCN partitioning between lichens and air. Lichen-air partitioning equations were established and used to predict PCN concentrations in air in Southeast Tibet. The lichens could be used as PCN biomonitors to clarify their spatial variations, sources, and transportation in the southeast of the plateau. PCN concentrations in lichens increased with altitude, suggesting that high-mountain cold-trapping influenced the PCN transportation behavior. Principal component analysis and linear discriminant analysis showed that the major source of PCNs in this region was long-range atmospheric transportation via the Indian monsoon in summer and wind from Southwest Asia in winter. This study provides a novel method using PCN congener profiles as fingerprints and statistical models for studying the geochemical effects of conditions in high-mountain regions on the contamination behaviors of 75 congeners of the notorious PCNs.

The environmental distribution and toxicity of short-chain chlorinated paraffins and underlying mechanisms: Implications for further toxicological investigation

Short-chain chlorinated paraffin (SCCP) pollution has become a global threat. Much attention has been paid to their environmental occurrence and toxicity. In this review, we summarized the wide distribution of SCCPs in various environmental matrices and biota, including human beings. Toxicokinetics and the toxicities of SCCPs, including lethality, hepatotoxicity, developmental toxicity, carcinogenicity, endocrine- and metabolism-disrupting effects, and immunomodulatory effects have been considered. The mechanisms of SCCP toxicity are mainly related to oxidative stress, metabolic disturbance, endocrine disruption and binding to biomacromolecules. In the future, further studies of SCCPs should focus on searching for their novel toxicity targets, and uncovering their toxic effects using transcriptomics, proteomics, metabolomics, and mutigenerational toxicity.

Trophic Dilution of Short-Chain Chlorinated Paraffins in a Plant-Plateau Pika-Eagle Food Chain from the Tibetan Plateau

Little is currently known about the trophic transfer behavior of short-chain chlorinated paraffins (SCCPs) in terrestrial ecosystems. The trophodynamics of SCCPs were investigated in a typical terrestrial food chain (plant-plateau pika-eagle) from the interior of the Tibetan Plateau with an altitude of 4730 m. Pervasive contamination by SCCPs was found in the Tibetan Plateau samples, and the average concentrations of SCCPs in soil, plant, plateau pika, eagle, and gut content of eagle samples were 81.6 ± 31.1, 173 ± 70.3, 258 ± 126, 108 ± 59.6, and 268 ± 93.9 ng/g (average ± standard deviation, dry weight, dw), respectively. The trophic magnification factor (TMF) of SCCPs was 0.37, implying the trophic dilution of SCCPs in this terrestrial food chain. The TMF values of individual congener groups were positively correlated with the values of log K_ow, log K_oa and biotransformation half-life. As a result of long-range transport, SCCPs congeners with low molecular weight dominated in Tibetan Plateau species (C₁₀₊₁₁ congeners = 76.9%, Cl₅₊₆₊₇ congeners = 71.5%), which could partly explain the low biomagnification factors (BMFs) of SCCPs in the Tibetan Plateau.

Altitude-dependent accumulation of short chain chlorinated paraffins in fish from alpine lakes and Lhasa river on the Tibetan Plateau

High mountain cold-trapping effects can play important roles in the global long-range transport of persistent organic pollutants (POPs). Short chain chlorinated paraffins (SCCPs) have recently been included into the Stockholm Convention as a new class of POPs. However, the long-range transport behavior and environmental fate of SCCPs still remain largely unknown in high-altitude mountain areas. In this study, a total of 51 fish samples were collected from five high-altitude mountain lakes and Lasha river across the Tibetan Plateau. SCCPs were positively detected in all fish samples, and the concentrations ranged from 3.9 to 107 ng g^-1 dry weight (dw) with an average of 26.6 ng g^-1 dw. Compared to aquatic organisms from the Artic and Antarctica, the SCCP levels found in alpine fish from the Tibetan Plateau were lower. A significant increasing trend in accumulation levels of SCCPs in alpine fish with the increasing altitude was found on the Tibetan Plateau (r = 0.98, p < 0.001). Shorter chain congener group C10 showed a significant increase in percentage contribution to total SCCPs with increasing altitude, but a contrary tendency was found for longer chain congener group C13. The widespread occurrence of SCCPs in Tibetan fish was mainly sourced from the long-range atmospheric transport, and the altitude-dependent distribution of SCCPs was due to the mountain cold-trapping effects and potential susceptibility to bioaccumulation. To our knowledge, this is the first report regarding the altitude-dependent accumulation of SCCPs in biota in the polar environment.

Analytical procedures for short chain chlorinated paraffins determination - How to make them greener?

The aim of the following paper was to gather current scientific information about the analytical protocols dedicated to measuring the content level of short-chain chlorinated paraffins (SCCPs) in various types of environmental samples. Moreover, the data about the basic validation parameters of applied procedures for SCCPs determination are listed. The main issue which is highlighted in the paper is the possibility of the application of green analytical chemistry (GAC) principals in the SCCPs measuring process to reduce the environmental impact of the applied methodology. Analytical methods dedicated to SCCPs determination contain a significant number of steps and require advanced analytical equipment during the quantitative and qualitative analysis. In addition, there is a substantial issue associated with the reliability of the obtained results, especially in the case of the quantification of individual SCCPs in the studied samples. Due to this fact, the paper attempts to discuss the various stages of the analytical procedure, in which appropriate changes in the formula or equipment solutions might be introduced to ensure a better quality of the analytical results, as well as to meet the requirements of the philosophy of green analytical chemistry. The most important case which concerns this subject is finding an optimal consensus between the economic and logistic aspects and the quality and "greenness" of the analytical procedure employed in SCCPs determination process.

Tissue-Specific Accumulation, Sexual Difference, and Maternal Transfer of Chlorinated Paraffins in Black-Spotted Frogs

The restriction on usage of short-chain chlorinated paraffins (SCCPs) under Stockholm Convention may promote the production and application of medium chain chlorinated paraffins (MCCPs) and long chain chlorinated paraffins (LCCPs) as substitutes. This study focused on the tissue-specific exposure to SCCPs, MCCPs, and LCCPs in black-spotted frog, a prevalent amphibian species in the Yangtze River Delta, China. The total CP concentrations in frog liver, muscle, and egg samples ranged of 35-1200, 6.3-97, and 6.8-300 ng/g wet weight (ww), respectively. Livers and eggs contained primary SCCPs (on average 78%) while MCCPs (43%) together with SCCPs (41%) were dominant in muscles. A significantly negative correlation was observed between hepatosomatic index and CPs concentration in liver ( p < 0.01), indicating that CP exposure may lower survival rates of frogs by suppressing the energy storage in liver. Additionally, maternal transfer, an important uptake pathway for CPs, was evaluated for the first time by calculating the ratios of CP levels in eggs to those in their paired liver tissues. The ratio of egg to liver for CP congener groups raised with the increasing of log K_ow values, indicating mother to egg transport of CPs was related to the lipophilicity of the chemicals.

Methods for trace analysis of short-, medium-, and long-chain chlorinated paraffins: Critical review and recommendations

Many methods for quantifying chlorinated paraffins (CPs) yield only a total concentration of the mixture as a single value. With appropriate analytical instrumentation and quantification methods, more reliable and detailed analysis can be performed by quantifying total concentrations of short-, medium-, and long-chain CPs (SCCPs, MCCPs, and LCCPs), and in the current optimal situation by quantifying individual carbon-chlorine congener groups (C_nCl_m). Sample extraction and clean-up methods for other persistent organochlorines that have been adapted for recovery of CPs must be applied prior to quantification with appropriate quality assurance and quality control to ensure applicability of the methods for SCCPs, MCCPs, and LCCPs. Part critical review, part tutorial, and part perspective, this paper provides practical guidance to analytical chemists who are interested in establishing a method for analysis of CPs in their lab facilities using commercial reference standards, or for expanding existing analysis of total CPs or SCCPs to analysis of SCCPs, MCCPs, and LCCPs, or to analysis of C_nCl_m congener groups.

Chlorinated paraffins in the indoor and outdoor atmospheric particles from the Pearl River Delta: Characteristics, sources, and human exposure risks

Chlorinated paraffins (CPs) are ubiquitously present in the environment due to their abundant production and consumption. Information on CPs as part of indoor particles is very limited although a significant amount of time is spent in indoor environments. Seventy-two indoor and 66 outdoor TSP/PM₁₀/PM_2.5 samples (particulate matters with aerodynamic diameter <100, 10, and 2.5μm) from 24 homes of the Pearl River Delta (PRD), China, were analyzed for CPs. PM_2.5 were found to be the dominant particles both indoors and outdoors. CPs were mainly distributed in PM_2.5 that accounted for 89.1% and 93.0% of the total particles indoors and outdoors, respectively. The geometric mean (GM) concentrations of medium-chain CPs (MCCPs) exceeded those of short-chain CPs (SCCPs) (22.0 vs. 9.2ng/m³) in all particle samples. Both SCCPs and MCCPs in the indoor particles (GM: 13.4 and 30.9ng/m³) were approximately twice as high as in the outdoor environment (GM: 6.1 and 15.2ng/m³). C₁₁ and C₁₄ carbon chains as well as six and seven chlorine homologues were found to be predominant in all samples with average percentages of 43.0% and 55.4%, respectively. The estimated daily CP intakes via PM_2.5 inhalation were 8.1-24.6 and 25.1-76.0ng/kg·bw/day for all age subgroups based on both mean and 95th percentile concentrations of CPs. However, the estimated daily uptakes decreased to 4.4-16.4 and 13.5-50.6ng/kg·bw/day, respectively, when the deposition fractions of PM_2.5 in the human lung were considered. Indoor PM_2.5 attributed to 93.8% exposure of CPs based on both total estimated daily intakes (EDIs) and estimated daily uptakes (EDUs), indicating that the indoor PM_2.5 exposure was very important. Infants and toddlers suffered higher exposure risks of CPs compared to other subgroups, indicating higher potential health risks; however, based on the margin of the exposure analysis these risks could be ignored.

Congener-specific C10C13 and C14C17 chlorinated paraffins in Chinese agricultural soils: Spatio-vertical distribution, homologue pattern and environmental behavior

A comprehensive spatio-vertical survey of short-chain (SCCPs, C_10-13) and medium-chain (MCCPs, C_14-17) chlorinated paraffins (CPs) was performed in surface and core soils from Chinese nation-wide agricultural lands in 2016, and a total of 48 congener groups were measured. The shorter carbon chain C_10-11 in SCCP and C_14-15 in MCCP homologue groups, and the lower chlorinated congeners (Cl_5-7) for both CP groups were predominant. The ∑SCCP and ∑MCCP concentrations in surface soils ranged from 39 to 1609 ng/g and 127-1969 ng/g, dry weight (dw), respectively. The spatial distribution trend showed that SCCP congener groups with relatively low octanol-water partition coefficient (K_OW) and octanol-air partition coefficient (K_OA) are uniformly distributed across surface soils compared to MCCP congener groups. Significant relationships were observed between the spatial variation of SCCP concentrations and the driving factors responsible for dispersion and deposition. The distribution behavior of SCCPs and MCCPs in highland and plain surface soils showed an increasing trend of MCCP concentrations with elevation, indicating the "mountain cold-trapping effect". Vertical distribution profile revealed similar homologue group composition patterns of SCCP and MCCP congener groups as those of surface soils. Furthermore, the penetration potential ratios (r) of chlorine and carbon atoms of CPs demonstrated that the lower chlorinated (Cl_5-7) and the shorter carbon chain (C_10-13) congener groups are more prone to vertical movement into deeper soil layers compared to the longer carbon chain (C_14-17) and highly chlorinated (Cl_8-10) congener groups.

The atmospheric transport and pattern of Medium chain chlorinated paraffins at Shergyla Mountain on the Tibetan Plateau of China

Large amounts of short chain and medium chain chlorinated paraffins (SCCPs and MCCPs) are released into the environment during production and usage. However, compared to SCCPs, there is a significant lack of attention for MCCPs. In this work, 83 air samples, collected between 2012 and 2015 from the Tibetan Plateau, were analyzed to investigate the airborne levels and distributions of MCCPs, further to evaluate their potential long-range transport behavior on the alpine area. The total air MCCP concentrations at Shergyla Mountain and Lhasa were between 50 and 690 pg/m³ and 800-6700 pg/m³, respectively. At Shergyla Mountain, MCCP concentrations in the air appeared an increasing trend with altitude, which indicated that MCCPs could potentially possess the ability of "mountain cold trapping". C₁₄ and C₁₅ congener groups were the dominant homologue groups. The mountain contamination potential (MCP) of different congener groups is closely related to their equilibrium partitioning coefficients between octanol and air (K_OA), and water and air (K_WA). Increasing MCCPs levels might be a potential threat to the environment and human exposure.

Validation of a HRGC-ECNI/LRMS method to monitor short-chain chlorinated paraffins in human plasma

Short-chain chlorinated paraffins (SCCPs) are produced in high volume and have the high potential to pose a threat to human health. However, little information is available for SCCP contamination in human blood/plasma/serum, mainly due to the difficulty of sample preparation and quantitative analysis. A method using high resolution gas chromatography coupled with electron capture negative ionization low resolution mass spectrometry (HRGC-ECNI/LRMS) was developed and validated to measure SCCPs in human plasma. The pretreatment process included protein denaturation and lipid elimination, liquid-liquid extraction with a mixture of n-hexane/dichloromethane (1:1, V/V), and cleanup on a multi-layer silica column. The blank controls, including procedural blank, vacuum blood collection tube blank, and instrumental blank, were the most pivotal points for the reliable analysis of SCCPs. The average value of procedural blanks was 9.0ng/g; and the method detection limit (MDL), calculated as the sum of the average procedural blank value and 3 times of the standard deviation of the procedural blanks, was 12.6ng/g plasma. The validated method was applied to measure the concentrations of the total SCCPs (∑SCCPs) in 50 plasma samples from a general population. The measured plasma concentrations of ∑SCCPs ranged from <MDL to 203ng/g wet weight (ww), with an average value of 32.0ng/g ww. The relative abundance profiles of SCCPs in plasma samples were dominated by C₁₀- and C₁₁-CP congener groups centered on Cl_6-7. The developed method can be used for the comprehensive and large-scale investigation of SCCP levels in human plasma.

Combined Effects of Dust and Dietary Exposure of Occupational Workers and Local Residents to Short- and Medium-Chain Chlorinated Paraffins in a Mega E-Waste Recycling Industrial Park in South China

Four types of dust samples and nine categories of locally produced staple foods were collected from a mega e-waste recycling industrial park and its surrounding regions, and simultaneously analyzed for short-chain and medium-chain chlorinated paraffins (CPs) to estimate dust and dietary exposure and their combined effects on occupational workers and local residents. All samples related to e-waste activities contained considerably high concentrations of CPs. The highest dust concentration was found in e-waste workshops. CPs were highly accumulated in local plant and animal origin foods, most markedly in fish, vegetables, and rice. The main contribution to CP intake under a median exposure scenario was from the diet, and vegetables, fish, and rice were the three largest dietary intake sources. Only the combined dust and food exposure from the present study has approached or even exceeded the highest tolerable daily intake (TDI) set up by the International Program on Chemical Safety (IPCS). However, due to lack of official threshold values for CP exposure on adverse human health, there are limitations on accurate risk assessment. Considering the presence of other exposure pathways, CPs' endocrine disrupter properties, as well as the multicomponent chemical "cocktails" effects, potential high risks from CP exposure may be posed to e-waste workers and local residents.

Air-Seawater Gas Exchange and Dry Deposition of Chlorinated Paraffins in a Typical Inner Sea (Liaodong Bay), North China

As a group of new persistent organic pollutants, short-chain chlorinated paraffins (SCCPs) and medium-chain CP (MCCPs) have attracted extensive worldwide interest in recent years. However, the data regarding to the environmental behavior, especially in atmospheric transfer and air-seawater exchange, are still sparse. In this study, seasonal marine boundary layer air and seawater samples were collected from Chinese Bohai sea and a fugacity model was built to evaluate the air-seawater diffusion and deposition flux of CPs. Generally, the total CP levels in atmosphere and seawater samples in summer were higher than those in spring, and CPs existed mostly in the gaseous phase in air and the dissolved phase in seawater. For SCCPs, C₁₀ and C₁₁ components were the most abundant homologue groups. For MCCPs, the C₁₄ homologue dominated in the particle phase of atmosphere and particulate phase of seawater. The logarithmic fugacity ratios (log f_a/ f_w) of higher chlorinated congeners (Cl₈ to Cl₁₀: 0.71 to 1.32 in May and 1.38 to 2.29 in August) indicated that net deposition was the predominant process, whereas lower chlorinated congeners, especially Cl₅ homologue groups in August, showed a trend of net volitization (log  f_a/ f_w < -0.5). The results of diffusion and dry deposition fluxes indicated that air-seawater gas exchange of CPs was significantly higher than dry deposition in the sampling areas.