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

Legacy and novel brominated flame retardants in outdoor settled dusts and pine needles in a megacity of Eastern China: Interpretation of plant uptake

Brominated flame retardants, considered emerging contaminants, are widespread and persist in the environment. This study investigated the contamination of legacy and novel brominated flame retardants in paired outdoor settled dusts and pine needles sampled from a megacity in the Eastern China. The measured total concentrations of PBDEs (∑27PBDEs) in outdoor settled dusts and pine needles were in the range of 77.4-345.2 ng/g dw and 20.7-120.0 ng/g dw, respectively, and equivalent ranges for novel brominated flame retardants (∑11NBFRs) were 25.7-1917.2 ng/g dw and 9.4-38.7 ng/g dw, respectively. BDE-209 and DBDPE dominated PBDEs and NBFRs profiles, respectively, in both dusts and pine needles. Outdoor settled dusts exhibited greater potentials to accumulate high-brominated PBDE homologues and EH-TBB while pine needles tended to accumulate low-brominated PBDE homologues, BTBPE and TBC. The plant uptake of BFRs was interpreted by McLachlan's framework on the assumption that the levels of BFRs in outdoor settled dusts and particle phase of air were positively correlated. The accumulation of PBDEs in pine needles was dominated by equilibrium partitioning between the vegetation and the gas phase when log KOA values <10 and by particle-bound deposition when log KOA values >13. However, NBFRs exhibited more complicated accumulation behavior. The predicted 50th percentile of the estimated daily intakes of ∑27PBDEs via outdoor settled dusts exposure for adults and children were 3.5 × 10-2 and 1.4 × 10-1 ng/kg body weight (bw)/day, respectively, and equivalent values for ∑11NBFRs were 1.6 × 10-2 ng/kg bw/day and 6.3 × 10-2 ng/kg bw/day, respectively. The calculated hazard index (HI) values were far <1, indicating exposure of BFRs via outdoor settled dust intake would not pose potential non-carcinogenic health risks to both adults and children.

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.

Current advances of chlorinated organics degradation by bioelectrochemical systems: a review

Chlorinated organic compounds (COCs) are typical refractory organic compounds, having high biological toxicity. These compounds are a type of pervasive pollutants that can be present in polluted soil, air, and various types of waterways, such as groundwater, rivers, and lakes, posing a significant threat to the ecological environment and human health. Bioelectrochemical systems (BESs) are an effective strategy for the degradation of bio-refractory compounds. BESs improve the waste treatment efficiency through the application of weak electrical stimulation. This review discusses the processes of BESs configurations and degradation performances in different environmental media including wastewater, soil, waste gas and groundwater. In addition, the degradation mechanisms and performance-enhancing additives are summarized. The future challenges and perspectives on the development of BES for COCs removal are briefly discussed.

Soil's Hidden Power: The Stable Soil Organic Carbon Pool Controls the Burden of Persistent Organic Pollutants in Background Soils

Persistent organic pollutants (POPs) tend to accumulate in cold regions by cold condensation and global distillation. Soil organic matter is the main storage compartment for POPs in terrestrial ecosystems due to deposition and repeated air-surface exchange processes. Here, physicochemical properties and environmental factors were investigated for their role in influencing POPs accumulation in soils of the Tibetan Plateau and Antarctic and Arctic regions. The results showed that the soil burden of most POPs was closely coupled to stable mineral-associated organic carbon (MAOC). Combining the proportion of MAOC and physicochemical properties can explain much of the soil distribution characteristics of the POPs. The background levels of POPs were estimated in conjunction with the global soil database. It led to the proposition that the stable soil carbon pools are key controlling factors affecting the ultimate global distribution of POPs, so that the dynamic cycling of soil carbon acts to counteract the cold-trapping effects. In the future, soil carbon pool composition should be fully considered in a multimedia environmental model of POPs, and the risk of secondary release of POPs in soils under conditions such as climate change can be further assessed with soil organic carbon models.

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.

The transport and distribution of novel brominated flame retardants (NBFRs) and organophosphate esters (OPEs) in soils and moss along mountain valleys in the Himalayas

Although the Himalayas act as a natural barrier, studies have demonstrated that certain traditional persistent organic pollutants (POPs) can be transported into the Tibetan Plateau (TP) through the mountain valleys. Herein, we selected five mountain valleys in the Himalayas to investigate novel flame retardants (NFRs), as representative novel POPs, their concentration, distribution, transport behavior, potential sources and ecological risk. The results revealed that total concentrations of 7 novel brominated flame retardants (NBFRs) ranged from 4.89 to 2853 pg/g dry weight (dw) in soil and from not detected (ND) to 4232 pg/g dw in moss. Additionally, total concentrations of 10 organophosphate esters (OPEs) ranged from ND to 84798 pg/g dw in soil. Among the NFRs, decabromodiphenylethane (DBDPE) and tri-phenyl phosphate (TPhP) were the predominant compounds. NBFRs and OPEs concentrations were slightly higher than those in the polar regions. The correlation between different compounds and altitude varies in different areas, indicating that the NFRs distribution in the mountain valleys result from a combination of long-range transport and local sources. The ecological risk assessment using risk quotient (RQs) revealed that TPhP and tris (2-chloroisopropyl) phosphate (TCIPP) exhibited medium or high risks at some sites. This study sheds light on the transport pathways and environmental behaviors of the NFRs in the valleys and highlights the need for increased attention to the ecological risks posed by OPEs in the TP.

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.

Advances and challenges in biocathode microbial electrolysis cells for chlorinated organic compounds degradation from electroactive perspectives

Microbial electrolysis cell (MEC) is a promising in-situ strategy for chlorinated organic compound (COC) pollution remediation due to its high efficiency, low energy input, and long-term potential. Reductive dechlorination as the most critical step in COC degradation which takes place primarily in the cathode chamber of MECs is a complex biochemical process driven by the behavior of electrons. However, no information is currently available on the internal mechanism of MEC in dechlorination from the perspective of the whole electron transfer procedure and its dependent electrode materials. This review addresses the underlying mechanism of MEC on the fundamental of the generation (electron donor), transmission (transfer pathway), utilization (functional microbiota) and reception (electron acceptor) of electrons in dechlorination. In addition, the vital role of varied cathode materials involved in the entire electron transfer procedure during COC dechlorination is emphasized. Subsequently, suggestions for future research, including model construction, cathode material modification, and expanding the applicability of MECs to removal gaseous COCs have been proposed. This paper enriches the mechanism of COC degradation by MEC, and thus provides the theoretical support for the scale-up bioreactors for efficient COC removal.

Chlorinated Paraffin Pollution in the Marine Environment

Chlorinated paraffins (CPs) are ubiquitous in the environment due to their large-scale usage, persistence, and long-range atmospheric transport. The oceans are a critical environment where CPs transformation occurs. However, the broad impacts of CPs on the marine environment remain unclear. This review describes the sources, occurrence and transport pathways, environmental processes, and ecological effects of CPs in the marine environment. CPs are distributed in the global marine environment by riverine input, ocean currents, and long-range atmospheric transport from industrial areas. Environmental processes, such as the deposition of particle-bound compounds, leaching of plastics, and microbial degradation of CPs, are the critical drivers for regulating CPs' fate in water columns or sediment. Bioaccumulation and trophic transfer of CPs in marine food webs may threaten marine ecosystem functions. To elucidate the biogeochemical processes and environmental impacts of CPs in marine environments, future work should clarify the burden and transformation process of CPs and reveal their ecological effects. The results would help readers clarify the current research status and future research directions of CPs in the marine environment and provide the scientific basis and theoretical foundations for the government to assess marine ecological risks of CPs and to make policies for pollution prevention and control.

Source toxicity characteristics of short- and medium-chain chlorinated paraffin in multi-environmental media: Product source toxicity, molecular source toxicity and food chain migration control through silica methods

Short and medium-chain chlorinated paraffin (SCCP/MCCP) have been widely studied because of their extensive environmental hazards. In this study, product source toxicity, molecular source toxicity and food chain migration of SCCP and MCCP in multi-environmental media were comprehensively considered. The additive combination of SCCP and MCCP in the air, water and soil environment was adjusted, and PVC, PU and rubber products with the lowest source toxicity were screened. The source toxicity of SCCP and MCCP in the water environment was inhibited by design of the feed additive addition scheme (highest inhibition was 16.29 %), and the source toxicity of SCCP and MCCP in the soil environment was affected by different field management measures (highest inhibition was 38.22 %). A forage fertilizer addition plan, a cattle feed addition plan and a special population healthy complementary food regulation plan were developed to prevent the migration step by step and absorption of SCCP and MCCP in the terrestrial food chain. In addition, by means of density functional theory and analysis of key amino acid residues, the mechanism of toxicity difference between SCCP and MCCP was analyzed from the level of chemical interaction, and rationality of the inhibition scheme designed in this study was verified.

Short- and medium-chain chlorinated paraffins in urban road dust of Shanghai, China: concentrations, source apportionment and human exposure assessment

Chlorinated paraffins (CPs) are ubiquitous anthropogenic contaminants that have been found in various environmental media. The objective of this study was to determine concentrations, spatial distribution, possible sources and potential health risk of SCCPs and MCCPs in urban road dust collected from Shanghai, China. The concentrations ranged from 9.74 to 11,400 ng g^-1 for ΣSCCPs, 44.1 to 49,900 ng g^-1 for ΣMCCPs and 53.9 to 61,400 ng g^-1 for total CPs, respectively. MCCPs were the dominant component in all road dust, averagely accounting for 82.8% of total CPs. The concentrations of CPs in dust collected from traffic and commercial areas were significantly higher than those from campus, industrial, park and residential areas (p < 0.01), which could be attributed to tire wear in heavy traffic. All dust samples were divided into two groups by hierarchical cluster analysis for both SCCPs and MCCPs, and the most abundant homologue groups in most samples were C₁₀Cl_7-10 and C₁₃Cl_7-9 for SCCPs, and C₁₄Cl_7-9 and C₁₅Cl_8-9 for MCCPs. Correlation analysis showed that all carbon homologues in road dusts were highly correlated each other, suggesting SCCPs and MCCPs in dust maybe came from similar sources. Three sources for CPs in dust samples were apportioned by the PMF model; their relative contributions to the total CPs burden in dust were 25.6% for factor 1 (commercial CP mixture), 13.7% for factor 2 (long-distance transport) and 60.7% for factor 3 (commercial CP mixture). The median estimated daily intakes of total CPs via road dust were 1.78 × 10^-5 for children and 3.0 × 10^-6 mg kg^-1 day^-1 for adults, respectively. Quantitative risk assessment using non-cancer hazard index and total margin of exposure of total CPs indicated that total CPs at the present level in road dust pose no significant risk for both children and adults in Shanghai.

Occurrence, spatial distribution, and risk assessment of short- and medium-chain chlorinated paraffins in sediment from black-odorous rivers across China

Chlorinated paraffins (CPs) were massively produced for varied industrial purposes, of which improper handling and consequent environmental release resulted in worldwide contamination. The present study investigated the occurrence and spatial distribution of short- and medium-chain chlorinated paraffins (SCCP/MCCPs) in 171 sediment samples from black-odorous urban rivers across China. Total SCCP and MCCP concentrations ranged from 8.3 to 9.4 × 10⁴ (median: 1.1 × 10³) ng/g dw, and from not-detected-value to 1.0 × 10⁶ (median: 1.3 × 10⁴) ng/g dw, respectively. No clear spatial distribution of SCCPs and MCCPs was observed since black-odorous urban rivers were polluted by point-sources of the SCCP/MCCPs. Significant positive correlations were identified between SCCP/MCCPs and total organic carbon, and between SCCP/MCCPs and other persistent organic matter, including polybrominated diethyl ethers, polychlorinated biphenyls, antibiotics, and plasticizers. The average ratios of MCCPs to SCCPs in most samples were divided into 11 and 16, implying the manufacturing and use of at least two types of CP technical mixtures in China. The composition of SCCP/MCCPs were similar to that in their commercial products. Ecological risk assessments by two approaches, including the Federal Environmental Quality Guidelines and Risk Quotient, both revealed that SCCP/MCCP in surface sediments confer an ecological risk. ENVIRONMENTAL IMPLICATION: SCCPs and MCCPs can be considered "hazardous materials" because of their massive production and their potential persistence, long-distance transfer, bioaccumulation potential, and toxicity. This research conducted a comprehensive study on SCCP/MCCP in black-odorous urban river sediments across China and revealed their environmental risk, which may improve understanding of SCCP/MCCP contamination characteristics.

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 K_p' and log P_L⁰ and log K_OA 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.

Bioaccumulation and Biotransformation of Chlorinated Paraffins

Chlorinated paraffins (CPs), a class of persistent, toxic, and bioaccumulated compounds, have received increasing attention for their environmental occurrence and ecological and human health risks worldwide in the past decades. Understanding the environmental behavior and fate of CPs faces a huge challenge owing to the extremely complex CP congeners. Consequently, the aims of the present study are to summarize and integrate the bioaccumulation and biotransformation of CPs, including the occurrence of CPs in biota, tissue distribution, biomagnification, and trophic transfer, and biotransformation of CPs in plants, invertebrates, and vertebrates in detail. Biota samples collected in China showed higher CP concentrations than other regions, which is consistent with their huge production and usage. The lipid content is the major factor that determines the physical burden of CPs in tissues or organs. Regarding the bioaccumulation of CPs and their influence factors, inconsistent results were obtained. Biotransformation is an important reason for this variable. Some CP congeners are readily biodegradable in plants, animals, and microorganisms. Hydroxylation, dechlorination, chlorine rearrangement, and carbon chain decomposition are potential biotransformation pathways for the CP congeners. Knowledge of the influence of chain length, chlorination degree, constitution, and stereochemistry on the tissue distribution, bioaccumulation, and biotransformation is still scarce.

Comparative in vitro metabolism of short chain chlorinated paraffins (SCCPs) by human and chicken liver microsomes: First insight into heptachlorodecanes

Short chain chlorinated paraffins (SCCPs) are emerging persistent organic pollutants of great concern due to their ubiquitous distribution in the environment. However, little information is available on the biotransformation of SCCPs in organisms. In this study, a chlorinated decane: 1, 2, 5, 5, 6, 9, 10-heptachlorodecanes (HeptaCDs) was subjected to in vitro metabolism by human and chicken liver microsomes at environmentally relevant concentration. Using ultra-performance liquid chromatography-Q-Exactive Orbitrap mass spectrometry, two metabolites: monohydroxylated hexachlorodecane (HO-HexCD) and monohydroxy heptachlorodecane (HO-HeptaCD) were detected in human liver microsomal assays, while only one metabolite (HO-HexCD) was identified in chicken liver microsomal assays. The formation of HO-HexCD was fitted to a Michaelis-Menten model for chicken liver microsomes with a V_max (maximum metabolic rate) value of 4.52 pmol/mg/min. Metabolic kinetic parameters could not be obtained for human liver microsomes as steady state conditions were not reached under our experimental conditions. Notwithstanding this, the observed average biotransformation rate of HeptaCDs was much faster for human liver microsomes than for chicken liver microsomes. Due to the lack of authentic standards for the identified metabolites, the detailed structure of each metabolite could not be confirmed due to the possibility of conformational isomers. This study provides first insights into the biotransformation of SCCPs, providing potential biomarkers and enhancing understanding of bioaccumulation studies.

Land-Ocean Exchange Mechanism of Chlorinated Paraffins and Polycyclic Aromatic Hydrocarbons with Diverse Sources in a Coastal Zone Boundary Area, North China: The Role of Regional Atmospheric Transmission

The marine environment is regarded as a crucial "sink" of numerous land-origin pollutants. As typical boundary regions, the coastal and offshore areas are used to evaluate the dominating transfer process and land-ocean exchange mechanism of semivolatile organic compounds. In air samples collected from a coastal area in North China over a whole year, chlorinated paraffins (CPs), including short-chain CPs and medium-chain CPs, and prior control 16 polycyclic aromatic hydrocarbons (PAHs) were determined, with mean concentrations of 25.8 and 94.7 ng/m³, respectively. Results of different gas-particle partitioning models indicated that the steady-state hypothesis provides a better description of the possible land-ocean exchange molecular mechanism. The source-sink influences for CPs and PAHs were affected by the predominant atmospheric motion, which alternated between gaseous diffusion and particulate sedimentation in different seasons. Source apportionment results indicated that different transfer characteristics contributed to the source divergence of ambient CPs and PAHs within 12 nautical miles in the same area. Coal/biomass combustion and diesel/natural gas combustion were the main PAH sources in the coast site (43.1%) and sea site (35.3%), respectively. Similar industrial sources CP-52 and CP-42 were the main CP sources in the coast site (41.4%) and sea site (40.8%), respectively.

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.

Concentrations, homolog profiles, and risk assessment of short- and medium-chain chlorinated paraffins in soil around factories in a non-ferrous metal recycling park

Chlorinated paraffins (CPs) are used as additives in metal processing in the metal smelting industry. Data on CPs in the environment near metal smelting plants are limited. The objectives of this study were to investigate the concentrations and congener profiles of CPs in soil around factories in a non-ferrous metal recycling park located in Hebei, China, and to investigate human exposure to CPs in the soil. The concentrations of short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) were determined by two-dimensional gas chromatography with electron capture negative ionization mass spectrometry. The SCCP and MCCP concentrations in the soil samples were 121-5159 ng/g and 47-6079 ng/g, respectively. Generally, the CP concentrations in soils around the factories were relatively high compared with those near other contaminated sites and in rural and urban areas. There were significant correlations between the MCCP concentrations, some SCCP carbon homologs, and the total organic carbon content (p < 0.05). The major SCCP and MCCP congener groups were C₁₀Cl_6-7 and C₁₅-₁₆Cl₅, respectively. Hierarchical cluster analysis and principal component analysis indicated that SCCPs and MCCPs in the soil might originate from extreme pressure additives containing CP-42 and CP-52 and CP-containing waste material from the factories. The concentrations in two samples collected near a metal recycling factory posed a moderate risk according to a risk assessment conducted using risk quotients. Further risk assessment showed that the CPs concentrations in soil did not pose significant health risks to either children or adults.

Novel brominated flame retardants (NBFRs) in soil and moss in Mt. Shergyla, southeast Tibetan Plateau: Occurrence, distribution and influencing factors

Research on the environmental fate and behavior of novel brominated flame retardants (NBFRs) remains limited, especially in the remote alpine regions. In this study, the concentrations and distributions of NBFRs were investigated in soils and mosses collected from two slopes of Shergyla in the southeast of the Tibetan Plateau (TP), to unravel the environmental behaviors of NBFRs in this background area. The total NBFR concentrations (∑₇NBFRs) ranged from 34.2 to 879 pg/g dw in soil and from 72.8 to 2505 pg/g dw in moss. ∑₇NBFRs in soil samples collected in 2019 were significantly higher than those in 2012 (p < 0.05). Decabromodiphenyl ethane (DBDPE) was the predominant NBFR, accounting for 90% of ∑₇NBFRs on average. The ratio of the concentrations in moss and soil showed significantly positive correlations with LogK_OA except for DBDPE (p < 0.05), indicating that the role of mosses as accumulators compared to soils are more pronounced for more volatile NBFRs. In addition, the concentrations of NBFRs generally decreased with increasing altitude on the south-facing slope, whereas on the north-facing slope some NBFRs exhibited different trends, suggesting concurrent local and long-range transport sources. Normalization based on total organic carbon/lipid concentrations strengthened the correlation with altitude, implying that the altitude gradient of the mountain slope and forest cover could jointly affect the distribution of NBFRs in the TP. Furthermore, principal components analysis (PCA) with multiple linear regression analysis (MLRA) showed that the average contribution of the mountain cold trapping effect (MCTE) accounted for the major (77%) contribution and forest filter effect (FFE) has only a modest contribution to the deposition of NBFRs in soil.

The effect of anthropogenic activities on the environmental fate of chlorinated paraffins in surface soil in an urbanized zone of northern China

Chlorinated paraffins (CPs) have been widely used as halogenated flame retardants and plasticizers since the mid-20th century. The prevalence of CPs in soil has been widely reported, but the distribution pattern of CPs in urbanized zones and their association with multiple socioeconomic variables have not been adequately explored. Herein, short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) were investigated in surface soil samples from Tianjin, China, a typical urbanized area. The concentration distributions of SCCPs and MCCPs showed similar trends in different administrative divisions and land use types: urban areas > suburbs > outer suburbs (p < 0.001) and residential areas > greenbelts > agricultural areas (p < 0.001). The CP congeners in residential surface soils mainly included those with longer carbon chains and high degree of chlorination, while the CP congeners in agricultural surface soils mainly consisted of those with shorter carbon chains and fewer chlorine substituents. Multiple statistical approaches were used to explore the association between socioeconomic factors and CP distribution. CP concentration was significantly correlated to population density and gross domestic product (GDP) (p < 0.001), and structural equation models incorporating administrative regional planning showed an indirect impact on the distribution of MCCP concentration due to the influence of regional planning on population density. These results highlight the association between CP contamination and the degree of urbanization, and this paper provides useful information toward mitigating the exposure risk of CPs for urban inhabitants.

Nickel spreading assessment in New Caledonia by lichen biomonitoring coupled to air mass history

Lichen biomonitoring and air mass trajectories were used to study the influence of mining activities in the atmospheric dispersion of metallic elements to assess the exposure of the population to dust emitted by mining activities. A map of forward trajectory densities from open mine surfaces throughout New Caledonia was computed and allowed to identify three preferred wind directions (trade wind, bent trade winds and oceanic winds) that could arise in mining particles dispersion all over New Caledonia. Areas where an air quality monitoring would be advisable to evaluate the exposure of the population to the Nickel dusts have been identified. Lichens collected around the industrial mining site KNS and in North Provence of New Caledonia were analysed for their Ni, Co, Cr, Zn and Ti contents. Backward trajectories were simulated from the lichen sampling point using FLEXTRA fed with ECMWF meteorological data, and densities of trajectories having overflown a mine were calculated. Ratio metal/Ti was then plotted as a function of air mass trajectory densities having overflown open pits. A positive correlation between trajectory densities and titanium-normalized metal in lichen for Ni, Co, Cr was highlighted, indicating that mining is a source of dispersion of these metals. For Zn, which is a tracer of fossil fuel or biomass (wood) combustion activity, no correlation was found. Graphical abstract.

Impurities in technical mixtures of chlorinated paraffins show AhR agonist properties as determined by the DR-CALUX bioassay

Chlorinated paraffins (CPs) are produced at more than one million tons per year. Technical CPs mixtures may contain impurities, which end up in consumer products. In the present study, 17 technical CPs mixtures were investigated for the potential occurrence of potential impurities. By applying the DR-CALUX bioassay, 3 out of 17 technical mixtures were shown to elicit responses at 4 h exposure time, but much lower at 48 h. Constitutional defined CPs materials did not show responses. Subsequently different groups of known AhR-agonists and compounds suspected to be present in technical CPs mixtures were investigated. Benzene, (poly)chlorobenzene, non-dioxin like polychlorinated naphthalenes (PCNs), and three-ringed polyaromatic hydrocarbons (PAHs) did not result in a significant response at 4 h or 48 h. TCDD, non-ortho PCBs, dioxin-like PCNs, four or five ringed PAHs and their chlorinated analogues resulted in a significant response. TCDD and the non-ortho PCBs showed the highest potency and stability, while dioxin-like PCNs, PAHs, and the chlorinated PAHs were clearly inactivated (metabolized) at longer incubation. Altogether, the present findings substantiate that AhR-mediated responses of CPs technical mixtures in the DR-CALUX bioassay are caused by impurities, most likely some intermediate stable AhR-agonists such as dioxin-like PCNs or (chlorinated) PAHs. The current study shows that impurities in CPs technical mixtures need to be investigated for assessing the safety of technical CPs mixtures.

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.