Tracking and optimizing toxic chemical exposure pathways through food trade: A case study in SCCPs contaminated seafood in China.

Food safety is related to human health and sustainable development. International food trade poses food safety risks through the collateral transport of toxic chemicals that are detrimental to human health. Domestic interprovincial trade has similar effects within countries but has not been comprehensively investigated previously. Here, we assessed the effects of interprovincial trade on food safety and human dietary exposure to short-chain chlorinated paraffins (SCCPs), a group of emerging persistent toxic chemicals, in seafood across China by synthesizing data from field observation and various models. Our findings indicate that there is a higher level of SCCPs exposure risk in coastal provinces compared to inland provinces. Approximately, 70.3% of human exposure to SCCPs through seafood consumption in China was embodied in the interprovincial seafood trade in 2021. Specifically, the domestic trade led to a remarkable increase in SCCPs exposure in the coastal provinces in South China, attributable to low SCCPs pollution in these provinces and imported seafood from those provinces with high SCCPs pollution. In contrast, human exposure to SCCPs decreased in those coastal provinces in East China due to importing seafood from those provinces with low SCCPs concentrations. The interprovincial seafood trade routes were optimized by linear programming to minimize human exposure to SCCPs considering both shipping cost and health risk constraints. The optimized trade routes reduced the national per capita SCCPs exposure through seafood consumption by over 12%. This study highlights the importance of interprovincial food trade in the risk assessment of toxic chemicals.

Characterization and health risks of short- and medium-chain chlorinated paraffins in the gas and size-fractionated particulate phases in ambient air.

Short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) have garnered significant attention because they have persistence and potential toxicity, and can undergo long-distance transport. Chlorinated paraffins (CPs) inhaled in the size-fractionated particulate phase and gas phase can carry different risks to human health due to their ability to accumulate in different regions of the respiratory tract and exhibit varying deposition efficiencies. In our study, large-volume ambient air samples in both the size-fractionated particulate phase (Dp < 1.0 µm, 1.0-2.5 µm, 2.5-10 µm, and Dp ≥ 10 µm) and gas phase were collected simultaneously in Beijing using an active sampler. The overall levels of SCCPs and MCCPs were relatively high, the ranges being 57-881 and 30-385 ng/m3, respectively. SCCPs tended to be partitioned in the gas phase (on average 75% of the ΣSCCP concentration), while MCCPs tended to be partitioned in the particulate phase (on average 62% of the ΣMCCP concentration). Significant correlations were discovered between the logarithm-transformed gas-particle partition coefficients (KP) and predicted subcooled vapor pressures (PL0) (p < 0.01 for SCCPs and MCCPs) and between the logarithm-transformed KP values and octanol-air partition coefficients (KOA) (p < 0.01 for SCCPs and MCCPs). Thus, the slopes indicated that organic matter absorption was the dominant process involved in gas-particle partitioning. We used the ICRP model to calculate deposition concentrations for particulate-associated CPs in head airways region (15.6-71.4 ng/m³), tracheobronchial region (0.8-4.8 ng/m³), and alveolar region (5.1-21.9 ng/m³), then combined these concentrations with the CP concentrations in the gas phase to calculate estimated daily intakes (EDIs) for inhalation. The EDIs for SCCPs and MCCPs through inhalation of ambient air for the all-ages group were 67.5-184.2 ng/kg/day and 19.7-53.7 ng/kg/day, respectively. The results indicated that SCCPs and MCCPs in ambient air do not currently pose strong risks to human health in the study area.

Developmental toxicity of short-chain chlorinated paraffins on early-stage chicken embryos in a shell-less (ex-ovo) incubation system.

Short-chain chlorinated paraffins (SCCPs) are listed as a category of globally controlled persistent organic pollutants (POPs) by the Stockholm Convention in 2017. However, SCCP toxicity, particularly their developmental toxicity in avian embryos, has not been well studied. In this study, we observed the early development of chicken embryos (Gallus gallus domesticus) by applying a shell-less (ex-ovo) incubation system developed in our previous studies. After exposing embryos at Hamburger Hamilton stage (HHS) 1 to SCCPs (control, 0.1% DMSO; SCCPs-L, 200 ng/g; SCCPs-M, 2000 ng/g; SCCPs-H, 20,000 ng/g), we observed the development of embryos from the 3rd to 9th incubation day. Exposure to SCCPs-M and -H induced a significant reduction in survival, with an LD50 of 3100 ng/g on the 9th incubation day. Significant dose-dependent decreases in body length were observed from days 4-9. We also found that SCCPs-H decreased the blood vessel length and branch number on the 4th incubation day. Additionally, SCCPs-H significantly reduced the heart rate on the 4th and 5th incubation days. These findings suggest that SCCPs may have potential of developmental and cardiovascular toxicity during the early stages of chicken embryos. Quantitative PCR of the mRNA of genes related to embryonic development showed that SLC16A10 (a triiodothyronine transporter) level decreased in the SCCPs-H group, showing a significant positive correlation with the body length of embryos. THRA level, a thyroid hormone receptor, was significantly decreased in the SCCPs-H group, whereas that of DIO3 level, a deiodinase was significantly increased. These results suggest that SCCPs exposure induces developmental delays via the thyroxine signaling pathway. Analysis of thyroid hormones (THs) in blood plasma also indicated a significant reduction in thyroxine (T4) levels in the SCCPs-H group on the 9th incubation day of embryos. In conclusion, SCCPs induce developmental toxicity by disrupting thyroid functions at the early-life stage of chicken embryos.

Effects of environmentally relevant concentration of short-chain chlorinated paraffins on BV2 microglia activation and lipid metabolism, implicating altered neurogenesis.

Short-chain chlorinated paraffins (SCCPs), a class of persistent organic pollutants, have been found to cause diverse organ and systemic toxicity. However, little is known about their neurotoxic effects. In this study, we exposed BV2, a mouse microglia cell line, to environmentally relevant concentration of SCCPs (1 µg/L, 10 µg/L, 100 µg/L) for 24 h to investigate their impacts on the nervous system. Our observations revealed that SCCPs induced the activation of BV2 microglia, as indicated by altered morphology, stimulated cell proliferation, enhanced phagocytic and migratory capabilities. Analysis at the mRNA level confirmed the activation status, with the downregulation of TMEM119 and Tgfbr1, and upregulation of Iba1 and CD11b. The upregulated expression of genes such as cenpe, mki67, Axl, APOE and LPL also validated alterations in cell functions. Moreover, BV2 microglia presented an M2 alternative phenotype upon SCCPs exposure, substantiated by the reduction of NF-κB, TNF-α, IL-1ß, and the elevation of TGF-ß. Additionally, SCCPs caused lipid metabolic changes in BV2 microglia, characterized by the upregulations of long-chain fatty acids and acylcarnitines, reflecting an enhancement of ß-oxidation. This aligns with our findings of increased ATP production upon SCCPs exposure. Intriguingly, cell activation coincided with elevated levels of omega-3 polyunsaturated fatty acids. Furthermore, activated microglial medium remarkably altered the proliferation and differentiation of mouse neural stem cells. Collectively, exposure to environmentally relevant concentrations of SCCPs resulted in activation and lipid metabolic alterations in BV2 microglia, potentially impacting neurogenesis. These findings provide valuable insights for further research on the neurotoxic effect of SCCPs.

[Metabolomic interference induced by short-chain chlorinated paraffins in human normal hepatic cells].

Short-chain chlorinated paraffins (SCCPs) are an emerging class of persistent organic pollutants (POPs) that are widely detected in environmental matrices and human samples. Because of their environmental persistence, long-range transport potential, bioaccumulation potential, and biotoxicity, SCCPs pose a significant threat to human health. In this study, metabolomics technology was applied to reveal the metabolomic interference in human normal hepatic (L02) cells after exposure to low (1 µg/L), moderate (10 µg/L), and high (100 µg/L) doses of SCCPs. Principal component analysis (PCA) and metabolic effect level index (MELI) values showed that all three SCCP doses caused notable metabolic perturbations in L02 cells. A total of 72 metabolites that were annotated by MS/MS and matched with the experimental spectra in the Human Metabolome Database (HMDB) or validated by commercially available standards were selected as differential metabolites (DMs) across all groups. The low-dose exposure group shared 33 and 36 DMs with the moderate- and high-dose exposure groups, respectively. The moderate-dose exposure group shared 46 DMs with the high-dose exposure group. In addition, 33 DMs were shared among the three exposure groups. Among the 72 DMs, 9, 9, and 45 metabolites participated in the amino acid, nucleotide, and lipid metabolism pathways, respectively. The results of pathway enrichment analysis showed that the most relevant metabolic pathways affected by SCCPs were the lipid metabolism, fatty acid ß-oxidation, and nucleotide metabolism pathways, and that compared with low-dose exposure, moderate- and high-dose SCCP exposures caused more notable perturbations of these metabolic pathways in L02 cells. Exposure to SCCPs perturbed glycerophospholipid and sphingolipid metabolism. Significant alterations in the levels of phosphatidylcholines, phosphatidylethanolamines, and sphingomyelins indicated SCCP-induced biomembrane damage. SCCPs inhibited fatty acid ß-oxidation by decreasing the levels of short- and medium-chain acylcarnitines in L02 cells, indicating that the energy supplied by fatty acid oxidation was reduced in these cells. Furthermore, compared with low- and moderate-dose SCCPs, high-dose SCCPs produced a significantly stronger inhibition of fatty acid ß-oxidation. In addition, SCCPs perturbed nucleotide metabolism. The higher hypoxanthine levels observed in L02 cells after SCCP exposures indicate that SCCPs may induce several adverse effects, including hypoxia, reactive oxygen species production, and mutagenesis in L02 cells.

Investigating the levels, spatial distribution, and trophic transfer patterns of short-chain chlorinated paraffins in the Southern Bohai Sea, China.

The marine environment of the southern Bohai Sea is severely polluted by short-chain chlorinated paraffins (SCCPs). To improve understanding of how SCCPs occur and of how they migrate, are transformed, and transferred in this area, we collected seawater, sediment, and organism samples, and determined the SCCP contents using a new approach based on high-resolution mass spectrometry. The ΣSCCP concentrations in the seawater, sediment, and organism samples ranged from 57.5 to 1150.4 ng/L, 167.7-1105.9 ng/g (dry weight), and 11.4-583.0 ng/g (wet weight), respectively. Simulation of the spatial distribution of SCCPs using Kriging interpolation showed that SCCPs were markedly influenced by land-based pollution. Substantial quantities of SCCPs were transported to the marine environment via surface runoff from rivers that passed through areas of major SCCP production. Once discharged from such rivers into the Bohai Sea, these SCCPs were further dispersed under the influence of ocean currents. Furthermore, the logarithmic bioaccumulation factor that varied from 2.12 to 3.20 and the trophic magnification factor that reached 5.60 (r2 = 0.750, p < 0.01) suggest that organisms have the ability to accumulate and biomagnify SCCPs through the food chain, which could potentially present risks to both marine ecosystems and human health.

Uptake, accumulation and toxicity of short chain chlorinated paraffins to wheat (Triticum aestivum L.).

Short chain chlorinated paraffins (SCCPs) are ubiquitous persistent organic pollutants. They have been widely detected in plant-based foods and might cause adverse impacts on humans. Nevertheless, uptake and accumulation mechanisms of SCCPs in plants remain unclear. In this study, the soil culture data indicated that SCCPs were strongly absorbed by roots (root concentration factor, RCF>1) yet limited translocated to shoots (translocation factor<1). The uptake mechanism was explored by hydroponic exposure, showing that hydrophobicity and molecular size influenced the root uptake and translocation of SCCPs. RCFs were significantly correlated with logKow values and molecular weights in a parabolic curve relationship. Besides, it was extremely difficult for SCCPs to translocate from shoots back to roots via phloem. An active energy-dependent process was proposed to be involved in the root uptake of SCCPs, which was supported by the uptake inhibition by the low temperature and metabolic inhibitor. Though SCCPs at environmentally relevant concentrations had no negative impacts on root morphology and chlorophyll contents, it caused obvious changes in cellular ultrastructure of root tip cells and induced a significant increase in superoxide dismutase activity. This information may be beneficial to moderate crop contamination by SCCPs, and to remedy soils polluted by SCCPs with plants.

[Determination of short- and medium-chain chlorinated paraffins in different components of human blood using gas chromatography-electron capture negative ion-low resolution mass spectrometry].

Short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) have attracted significant attention because of their persistence, biotoxicity, bioaccumulation, and long-range migration. Given their worldwide detection in a variety of environmental matrices, concerns related to the high exposure risks of SCCPs and MCCPs to humans have grown. Thus, knowledge of the contamination patterns of SCCPs and MCCPs and their distribution characteristics in the vivo exposure of humans is of great importance. However, little information is available on the contamination of SCCPs and MCCPs in human blood/plasma/serum, mainly because of the difficulty of sample preparation and quantitative analysis. In this study, a new blood sample pretreatment method based on Percoll discontinuous density gradient centrifugation was developed to separate plasma, red blood cells, white blood cells, and platelets from human whole blood. A series of Percoll sodium chloride buffer solutions with mass concentrations of 1.095, 1.077, and 1.060 g/mL were placed in a centrifuge tube from top to bottom to establish discontinuous density gradients. The dosage for each density gradient was 1.5 mL. Human whole blood samples mixed with 0.85% sodium chloride aqueous solution were then added to the top layer of the Percoll sodium chloride solution. After centrifugation, the whole blood was separated into four components. The plasma was located at the top layer of the centrifuge tube, whereas the platelets, white blood cells, and red blood cells were retained at the junction of the various Percoll sodium chloride solutions. The sampling volume of human whole blood and incubation time were optimized, and results indicated that an excessively long incubation time could lead to hemolysis, resulting in a decrease in the recoveries of SCCPs and MCCPs. Therefore, a sampling volume of 1.5 mL and incubation time of 10 min at 4 ℃ were adopted. The cells of the blood components were further broken and extracted by ultrasonic pretreatment, followed by multilayer silica gel column chromatography for lipid removal. The use of 80 mL of n-hexane-dichloromethane (1∶1, v/v) and 50 mL of dichloromethane as the elution solvents (collected together) for the gel column separated the SCCPs and MCCPs from the lipid molecules in the blood samples. Gas chromatography-electron capture negative ion-low resolution mass spectrometry (GC-ECNI-LRMS) was used to determine the SCCPs and MCCPs. Quantification using the corrected total response factor with degrees of chlorination was achieved with linear corrections (R2=0.912 and 0.929 for the SCCPs and MCCPs, respectively). The method detection limits (MDLs) for the SCCPs and MCCPs were 1.57 and 8.29 ng/g wet weight (ww, n=7), respectively. The extraction internal standard recoveries were 67.0%-126.6% for the SCCPs and 69.5%-120.5% for the MCCPs. The developed method was applied to determine SCCPs and MCCPs in actual human whole blood samples. The contents of SCCPs and MCCPs were 10.81-65.23 and 31.82-105.65 ng/g (ww), respectively. Red blood cells exhibited the highest contents of CPs, followed by plasma, white blood cells, and platelets. The proportions of SCCPs and MCCPs in red blood cells and plasma were 70% and 66%, respectively. In all four components, the MCCP contents were higher than the SCCP contents, and the ratios of MCCPs to SCCPs ranged from 1.04 to 3.78. Similar congener patterns of SCCPs and MCCPs were found in the four components of human whole blood. C10-CPs and C14-CPs were predominantly observed in the SCCPs and MCCPs, respectively. In summary, a simple and efficient method was proposed to determine low concentrations of SCCPs and MCCPs in human blood with high sensitivity and selectivity. This method can meet requirements for the quantitative analysis of SCCPs and MCCPs in human blood components, thereby providing technical support for human health risk assessment.

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.

Levels and diverse composition profiles of chlorinated paraffins in indoor dust: possible sources and potential human health related concerns.

Chlorinated paraffins (CPs), a group of mixtures with different carbon chain lengths and chlorine contents, are widely used as plasticizers and flame retardants in various indoor materials. CPs could be released from CP-containing materials into the ambient environment and then enter the human body via inhalation, dust ingestion and dermal absorption, resulting in potential effects on human health. In this study, we collected residential indoor dust in Wuhan, the largest city in central China, and focused on the co-occurrence and composition profiles of CPs as well as the resultant human risk via dust ingestion and dermal absorption. The results indicated that CPs with C9-40 were ubiquity in indoor dust with medium-chain CPs (MCCPs, C14-17) as the main components (6.70-495 µg g-1), followed by short-chain CPs (SCCPs, C10-13) (4.23-304 µg g-1) and long-chain (LCCPs, C≥18) CPs (3.68-331 µg g-1). Low levels (not detected-0.469 µg g-1) of very short-chain CPs (vSCCPs, C9) were also found in partial indoor dust. The dominant homolog groups were C9 and Cl6-7 groups for vSCCPs, C13 and Cl6-8 groups for SCCPs, C14 and Cl6-8 groups for MCCPs, and C18 and Cl8-9 groups for LCCPs. Based on the measured concentrations, vSCCPs, SCCPs, MCCPs, and LCCPs posed limited human health risks to local residents via dust ingestion and dermal absorption.

Gas/particle partitioning of short and medium chain chlorinated paraffins from a CP production plant using passive air sampler and occupational exposure assessment.

Short and medium chain chlorinated paraffins (SCCPs and MCCPs) attract increasing attentions due to their persistence, long-range transport capacity. Their gas/particle partitioning from the production emission source, the effects to the ambient environment and exposure for employees are worth revealing. Polyurethane foam based passive air samplers (PUF-PAS) was deployed to determine the environmental levels of SCCPs (63.4-719.7 ng/m3) and MCCPs (151.6-1009.2 ng/m3) in the gas-phase and particle-phase both in the outdoor air in a CP production plant and the indoor air in the workshops. Extremely high SCCPs were found in the chlorination workshop and outdoor samples nearby, attributing to the release during the production. In the workshops, dramatically higher SCCP concentrations were determined than outdoors. SCCPs and MCCPs predominated in the gas-phase with a proportion >80 %. C10-CPs and C14-CPs were dominated with a proportion higher than 20 % and 50 %, respectively. Significant correlations between log Kp' and log PL0 and log KOA were observed in the outdoor air in a CP production plant and the indoor air in the workshops, respectively. A multivariate mechanism based on adsorption by organic matters and influenced by absorption processes might determine the gas/particle partitioning of CPs in the production source area. Two scenarios of occupational exposure i.e. working in the workshops and working outdoors were considered. Higher occupational exposure via inhalation to MCCPs was found for employees than SCCPs in the workshops, which was estimated to be 137.1 ng/kg/day at a worst case. No obvious adverse effects were observed for occupational employees in this CP production plant.

Exposure to short-chain chlorinated paraffins induces astrocyte activation via JAK2/STAT3 signaling pathway.

In the last few decades, short-chain chlorinated paraffins (SCCPs) have become the most heavily produced monomeric organohalogen compounds, and have been reported to induce multiple organ toxicity. However, the effects of SCCPs on the central nervous system are unknown. In the present study, we show that SCCP exposure induced astrocyte proliferation and increased the expression of two critical markers of astrocyte activation, glial fibrillary acidic protein and inducible nitric oxide synthase, in vivo and in vitro. SCCP exposure also increased inflammatory factory gene expression. Moreover, SCCP treatment triggered Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signalling, as shown by increased phosphorylation and STAT3 translocation to the nucleus. Both JAK2 and STAT3 inhibition effectively attenuated SCCP-induced astrocyte activation. Finally, JAK2 inhibition significantly rescued STAT3 phosphorylation and nuclear translocation. Taken together, JAK2/STAT3 pathway activation contributed to SCCP-induced astrocyte activation. These data will help elucidate the molecular mechanism underlying SCCP-induced neurotoxicity.

Transplacental transfer of plasticizers and flame retardants in fin whales (Balaenoptera physalus) from the North Atlantic Ocean.

Marine mammals are one of the groups of animals most affected by marine pollution including that by organic compounds which, besides bearing recognised harmful effects to adults, they may also affect foetuses through placental transfer. In this study we analysed samples of fin whale (Balaenoptera physalus) females and their foetuses collected in the western Iceland summer feeding grounds in 2018. Three different families of organic pollutants: organophosphate esters (OPEs); halogenated flame retardants (HFRs); and short chain chlorinated paraffins (SCCPs), were analysed and their placental transfer investigated. HFRs were detected in 87.5% of females and 100% of foetus samples with concentrations that ranged between nd-15.4 and 6.37-101 ng/g lipid weight (lw), respectively. OPEs were detected in all samples, both from females (85.8-567 ng/g lw) and foetuses (nq-1130 ng/g lw). SCCPs were detected in 87.5% of female samples and 100% of foetal samples with concentrations that ranged between nd-30.9 and nq-574 ng/g lw, respectively. For OPE compounds, a significant negative correlation was observed between the logarithm maternal transfer ratio and their log Kow, indicating that a high lipophilicity reduced placental transfer rate. Interestingly, the decabromodiphenyl ethane (DBDPE) was the compound with the highest log Kow but also the one that was transferred the most from mothers to foetuses, calling for in-depth research on this pollutant. These results constitute the first evidence of mother-calf transfer of plasticizers and flame retardants in fin whales. Further investigations are needed to determine their potential effects on this species and other groups of animals.

Effects of Pressurized Aeration on the Biodegradation of Short-Chain Chlorinated Paraffins by Escherichia coli Strain 2.

Short-chain chlorinated paraffins (SCCPs) were defined as persistent organic pollutants in 2017, and they can migrate and transform in the environment, accumulate in organisms, and amplify through the food chain. Although they pose a serious threat to environmental safety and human health, there are few papers on their removal. The current SCCP removal methods are expensive, require severe operating conditions, involve time-consuming biological treatment, and have poor removal specificities. Therefore, it is important to seek efficient methods to remove SCCPs. In this paper, a pressurized reactor was introduced, and the removal performance of SCCPs by Escherichia coli strain 2 was investigated. The results indicated that moderate pure oxygen pressurization promoted bacterial growth, but when it exceeded 0.15 MPa, the bacterial growth was severely inhibited. When the concentration of SCCPs was 20 mg/L, the removal rate of SCCPs was 85.61% under 0.15 MPa pure oxygen pressurization for 7 days, which was 25% higher than at atmospheric pressure (68.83%). In contrast, the removal rate was only 69.28% under 0.15 MPa air pressure. As the pressure continued to increase, the removal rate of SCCPs decreased significantly. The total amount of extracellular polymeric substances (EPS) increased significantly upon increasing the pressure, and the amount of tightly bound EPS (TB-EPS) was higher than that of loosely bound EPS (LB-EPS). The pressure mainly promoted the secretion of proteins in LB-EPS. Furthermore, an appropriate pure oxygen pressure of 0.15 MPa improved the dehydrogenase activity. The gas chromatography-mass spectrometry (GC-MS) results indicated that the degradation pathway possibly involved the cleavage of the C-Cl bond in SCCPs, which produced Cl-, followed by C-C bond breaking. This process degraded long-chain alkanes into short-chain alkanes. Moreover, the main degradation products detected were 2,4-dimethylheptane (C9H20), 2,5-dimethylheptane (C9H20), and 3,3-dimethylhexane (C8H18).

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.

Air-soil exchange of and risks posed by short- and medium-chain chlorinated paraffins: Case study in a contaminated area in China.

Short-chain (SC) and medium-chain (MC) chlorinated paraffins (CPs) are found widely in the environment. Little research into air-soil exchange of SCCPs and MCCPs has been performed. In this study, CP concentrations, congener group profiles, and air-soil exchange in a typical contaminated area were investigated. A total of 10 soil samples and 10 air samples were collected from Zhoushan, an island in China. The samples were analyzed by two-dimensional gas chromatography electron capture negative ionization mass spectrometry. The SCCP and MCCP concentrations in the soil samples were 72-3842 and 117-8819 ng/g, respectively, and the SCCP and MCCP concentrations in the air samples were 57-208 and 1.8-25 ng/m3, respectively. The highest CP concentrations in both soil and air were found in samples from near shipyards, possibly because of CPs being emitted from metal cutting fluids and marine paints used at the shipyards. C14-15Cl7-9 were the dominant CP congener groups in the soil samples. C10Cl6-7 were the dominant CP congener groups in the air samples. Chlorinated decane and undecane and penta-, hexa-, and hepta-chlorinated CPs were enriched in the air relative to the soil. These congeners may have been released from the commercial CP-42 and CP-52. The fugacity fractions (ffs) of 48 homologs decreased as Koa increased. The ffs indicated that SCCPs and MCCPs dominated deposition. The net air-soil exchange fluxes of CPs were 201-769 ng/(m2·h). A preliminary risk assessment indicated that CPs pose low ecological risk except at sampling site S7 and do not pose significant health risks.

Comparison of short-chain chlorinated paraffin concentrations and homolog profiles by interlaboratory trial using a candidate reference material.

Chlorinated paraffins (CPs) are industrial chemicals that have been primarily used in applications involving metalworking fluids. Among CPs, short-chain chlorinated paraffins (SCCPs) are a well-known environmental pollutant and are listed under Annex A of the Stockholm Convention on Persistent Organic Pollutants. CPs are alkanes substituted with chlorine atoms, and SCCPs are comprised of 10-13 carbon atoms. Reliable quantification of SCCPs is a critical issue because of the large number of SCCP isomers that are in use across multiple industries. Some interlaboratory comparisons of SCCP analyses have been conducted, and the reliability of these results was overwhelmingly determined as inferior to that of comparable PCB and dioxin analyses because of variations in the quality of commercial reagents that were employed as quantification standards. In order to address such inconsistencies, this study endeavored to prepare and evaluate a novel SCCP formulation as a candidate reference material for use as a reliable quantification standard. A subject trial study was hence performed to evaluate methods such as gas- and liquid-chromatography mass spectrometry (GC/MS and LC/MS) on sample matrices (without a clean-up process), and to subsequently elucidate the interpreted specifications for their candidacy as a reliable quantification standard. Results ultimately showed that the SCCP concentrations obtained from GC and LC were comparable. When the homologs reported by a subset of 14 separate laboratories were unified (excluding all results for Cl4 homologs), the carbon chain length profiles obtained from GC and LC were found to be similar; however, the overall chlorine homolog profiles did exhibit slight differences. Moreover, the results from high-resolution MS showed less variation than those from low-resolution MS. Thus, it was overarchingly determined that the deployment of this candidate reference material would serve as an effective mechanism for estimating the comparability of SCCP quantifications/evaluations of standard materials.

Spatial distribution, partitioning, and ecological risk of short chain chlorinated paraffins in seawater and sediment from East China Sea.

Short chain chlorinated paraffins (SCCPs) have attracted increasing attention due to their potential risks to the ecosystem and human health. However, there is still a lack of systematic research on their environmental fate in the coastal marine environment. In this study, we collected paired seawater (n = 40) and surface sediment samples (n = 40) from East China Sea, and investigated their spatial distribution, partitioning behaviors and ecological risks. The total SCCP concentrations (∑SCCPs) in seawater and sediment samples were in the range of 12.2-430 ng/L and 89.6-351 ng/g (dry weight), respectively. C10-11 SCCPs and Cl5-7 SCCPs were the predominant homologues in all of the samples. This study first calculated the field-based logKOC values for ∑SCCPs in the marine environment, which ranged from 5.0 to 6.5 (mean 5.5). The logKOC values of SCCP homologues (range 3.6-8.0, mean 5.6) showed a weak correlation with their logKOW (R = 0.214, p < 0.05). A preliminary risk assessment indicated that SCCPs at current levels posed no significant ecological risk. Overall, this study contributes to the further understanding of environmental behaviors of SCCPs in the marine environment.

Bioaccumulation and trophic magnification of short chain chlorinated paraffins in marine organisms from East China Sea.

As new persistent organic pollutants, short chain chlorinated paraffins (SCCPs) have recently received particular attention. However, knowledge on their bioaccumulation and trophic magnification in marine organisms from East China Sea (ECS) is still scare. In this study, we investigated the concentrations of SCCPs in seawater (n = 15) and marine organisms (n = 88) collected from ECS. The total concentrations of SCCPs (∑SCCPs) ranged from 12.5 to 242 ng/L in seawater and from 12.8 to 1819 ng/g wet weight (ww) in organisms. C10-11 SCCPs and Cl5-7 SCCPs were the predominant homologues in all samples, with the mean proportions of 70 ± 6.5% and 80 ± 7.8% in seawater, as well as 52-77% and 61-84% in marine organisms, respectively. The logarithm bioaccumulation factor (log BAF) values of ∑SCCPs were in the range of 2.04-3.79 in zooplankton, fish, shrimp, crab, shellfish, snail, and cephalopod. The log BAF values of SCCP homologues (1.33-4.75) increased significantly with the increase of their logarithm octanol-water partition coefficients (log KOW) values, indicating that hydrophobicity is the major factor controlling the bioaccumulation of SCCPs. The trophic magnification factor (TMF) value of ∑SCCPs was calculated to be 3.98, indicating the potential trophic magnification of SCCPs in this marine food web from ECS. A slightly increasing trend was observed between the TMF values of SCCP homologues and their log KOW values. Overall, for the first time, this study systematically examined the bioaccumulation and trophic magnification of SCCPs in the marine food web from East China Sea.

Groundwater contaminated with short-chain chlorinated paraffins and microbial responses.

The vertical migrations of toxic and persistent short-chain chlorinated paraffins (SCCPs) in soils as well as the microbial responses have been reported, however, there is a paucity of data on the resulting groundwater contamination. Here, we determined the concentration and congener profile of SCCPs in the groundwater beneath a production plant of chlorinated paraffins (CPs) and characterized the microbial community to explore their responses to SCCPs. Results showed that SCCPs ranged from not detected to 70.3 µg/L, with C13-CPs (11.2-65.8%) and Cl7-CPs (27.2-50.6%), in mass ratio, as the dominant groups. Similar to the distribution pattern in soils, SCCPs in groundwater were distributed in hotspot pattern. CP synthesis was the source of SCCPs in groundwater and the entire contamination plume significantly migrated downgradient, while there was an apparent hysteresis of C13-CP migration. Groundwater microbial community was likely shaped by both hydrogeological condition (pH and depth) and SCCPs. Specifically, the microbial community responded to the contamination by forming a co-occurrence network with "small world" feature, where Desulfobacca, Desulfomonile, Ferritrophicum, Methylomonas, Syntrophobacter, Syntrophorhabdus, Syntrophus, and Thermoanaerobaculum were the keystone taxa. Furthermore, the interrelations between bacterial taxa and SCCPs indicated that the microbial community might cooperate to achieve the dechlorination and mineralization of SCCPs through either anaerobic organohalide respiration mainly functioned by the keystone taxa, or cometabolic degradation processes functioned by Aquabacterium and Hydrogenophaga. Results of this study would provide a better understanding of the environmental behavior and ecological effects of SCCPs in groundwater systems.