Dispersion of Short- and Medium-Chain Chlorinated Paraffins (CPs) from a CP Production Plant to the Surrounding Surface Soils and Coniferous Leaves

Environmental fate and transformation mechanisms of chlorinated organic pollutants from the petrochemical industry: Insights for pollution control and remediation

Chlorinated organic pollutants (Cl-OPs), highly toxic and environmentally persistent, have become the spotlight, particularly from petrochemical industry. This study focuses on environmental fate of Cl-OPs from petrochemical industry, and transformation mechanisms in multi-media, aiming to enhance pollution control and remediation strategies. Emitted from leakage and waste discharge, Cl-OPs, encompassing chlorinated volatile organic compounds (Cl-VOCs), traditional and emerging persistent organic pollutants (POPs), were prevalent with average concentrations of 10-6-103 μg/m3 in the atmosphere, 10-2-105 μg/kg in soil and 100-105 μg/L in groundwater. Significantly, emerging POPs, particularly hexachlorobutadiene (HCBD) and short-chain chlorinated paraffins (SCCPs), with concentrations comparable to Cl-VOCs, urgently need attention. Once into the environment, Cl-OPs are naturally transformed primarily through atmospheric oxidation and water photolysis induced by hydroxyl radical (‧OH), and microbial degradation. Despite challenges in atmospheric complete degradation, ‧OH in water effectively photolytically degrade chlorinated benzenes and paraffins facilitated by dissolved oxygen and organic matter. Microbial degradation, influenced by oxygen, temperature, and pH, is essential for Cl-OPs removal from water and soil, where oxidation make complete mineralization possible whereas dechlorination may generate higher toxic intermediates. Hence, Cl-OPs control necessitates an attentive to leakage and waste management. Furthermore, advanced ‧OH oxidation and microbial treatment are of effective remediation prospect.

First report on liquid crystal monomers in tree barks surrounding a display manufacturer: Insights for atmospheric transport and establishment of priority list

Tree bark has been proven as an effective passive air sampler, particularly where access to active sampling methods is limited. In this study, 60 target liquid crystal monomers (LCMs; comprising 10 cyanobiphenyl and analogs (CBAs), 13 biphenyl and analogs (BAs), and 37 fluorinated biphenyl and analogs (FBAs)) were analyzed in 34 tree barks collected from the vicinity of a liquid crystal display (LCD) manufacturer situated in the Pearl River Delta, South China. The concentrations of LCMs in tree barks ranged from 1400 to 16000 ng/g lipid weight, with an average of 5900 ng/g lipid weight. Generally, bark levels of BAs exponentially decreased within 5 km of the LCD manufacturer. The profiles of LCMs in tree barks are similar to previously reported patterns in gaseous phase, suggesting bark's efficacy as a sampler for gaseous LCMs. The inclusion of different congeners in existing studies on the environmental occurrence of LCMs has hindered the horizontal comparisons. Therefore, this study established a list of priority LCMs based on environmental monitoring data and the publicly accessible production data. This list comprised 146 LCMs, including 63 REACH registered LCMs that haven't been analyzed in any study and 56 belonging to 4 types of mainstream LCMs.

Assessing the impact of mining on cyclic and linear methylsiloxane distribution in Tibetan soils: Source contribution and transport pattern

The pervasive presence of methylsiloxanes (MSs), comprising linear and cyclic congeners, in the environment poses significant ecological risks, yet the understanding of their transport mechanisms and deposition patterns remains limited. This study analyzed the concentrations of 12 linear-MSs (L3-L14) and 7 cyclic-MSs (D3-D9) in 29 surface soil samples collected across varying altitudes (3726 to 4863 m) near the Jiama mining sector in Tibet, aiming to investigate the distribution and transport dynamics of MSs from the emission source. The distribution of total MS concentration (ranging from 50.1 to 593 ng/g) showed a remarkable correlation with proximity to the mining site, suggesting the emergent source of mining activities for the MSs in the remote environment of the Tibetan Plateau. Employing the innovative model of robust absolute principal component scores-robust geographically weighted regression (RAPCS-RGWR), the analysis predicted that the mining operations contributing 57.1 % of the total soil MSs, would significantly surpass contributions from traffic emissions (14.7 %), residential activities (13.2 %), and the environmental factor of total organic matter content (14.9 %). The Boltzmann equation effectively modeled the distribution pattern of soil MSs, highlighting atmospheric transport and gravitational settling as key distribution mechanisms. However, linear-MSs exhibited longer transport distances than cyclic-MSs and were more profoundly affected by prevailing wind directions, suggesting their differential environmental behaviors and risks. Our study underscored that the mining sector possibly emerged as a significant source of Tibetan MSs, and provided insights into the transport and fate of MSs in remote, high-altitude environments. The findings emphasize the need for targeted pollution control strategies to mitigate the environmental footprint of mining activities in Tibet and similar regions.

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.

Short- and medium-chain chlorinated paraffins in surface sediment from Lake Ontario

Concentrations of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) were analyzed and investigated in surficial sediment collected in 2018 from ten different nearshore sites in Lake Ontario and the St. Lawrence River influenced by inputs from varying urban and historical land uses. Sites were grouped into two categories of tributary and lake according to their location. Results show that tributary sites had higher concentrations of total chlorinated paraffin (CP) than lake sites. Humber Bay, a lake site, had the highest total CP concentration (55,000 ng/gTOC) followed by Humber River, a tributary site (50,000 ng/gTOC). The lowest concentrations were found in eastern Lake Ontario and Lake St. Francis in the St. Lawrence River (540 ng/gTOC). Higher concentrations of chlorinated paraffins (CPs) were found where runoff and wastewater inputs from urban areas, current industrial activities, and population were the greatest. Levels of MCCPs were higher than SCCPs at all sites but one, Lake St. Francis. Among the SCCPs, C13 and among the MCCPs C14 were the dominant chain length alkanes, with C14 being the highest among both groups. The SCCPs and MCCPs profiles suggest that they can be used to distinguish between sites impacted by local sources vs. sites impacted by short-/long-range transport of these chemicals.

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.

Positive association between chlorinated paraffins and the risk of allergic diseases in children and adolescents

Contaminants may induce immune response polarization, leading to immune diseases, such as allergic diseases. Evidence concerning the effects of chlorinated paraffins (CPs), an emerging persistent organic pollutant, on immune system is scarce, particularly for epidemiological evidence. This study explores the association between CPs exposure and allergic diseases (allergic rhinitis, atopic eczema, and allergic conjunctivitis) in children and adolescents in the Pearl River Delta (PRD) in China. Herein, 131,304 children and adolescents from primary and secondary schools in the PRD were included and completed the questionnaire survey. The particulate matter (PM) samples were collected in the PRD and the PM2.5-bound CP concentrations were analyzed. In the multivarious adjustment mixed effect model (MEM), an IQR increase in ∑CPs was significantly associated with allergic diseases (rhinitis, eczema, and conjunctivitis) with the estimated odds ratios (ORs) for 1.11 (95% CI: 1.10, 1.13), 1.17 (95% CI: 1.15, 1.19), and 1.82 (95% CI: 1.76, 1.88), respectively. Interaction analysis indicated that overweight and obese individuals might have greater risk. Similar effect estimates were observed in several sensitivity analyses. This study provided epidemiological evidence on the immunotoxicity of CPs. More studies to confirm our findings and investigate mechanisms are needed.

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.

Occurrence and Formation Mechanism of PCDD/Fs and SCCPs in Chlorinated Paraffin Products

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and short-chain chlorinated paraffins (SCCPs) can be formed during the production of chlorinated paraffins (CPs). Detection and accurate quantification of PCDD/Fs in CPs are challenging because of their matrix complexity. Therefore, the occurrence and formation mechanisms of PCDD/Fs from CPs have not been studied extensively in the past. In this study, 15 commercial samples including solid and liquid CPs were collected in 2022 from China. The average ΣSCCP concentrations detected in the solid and liquid CPs were 158 and 137 mg/g, respectively. The average International Toxic Equivalent (I-TEQ) values of 2,3,7,8-PCDD/F in solid and liquid CPs were 15.8 pg I-TEQ/g and 15.0 pg I-TEQ/g, respectively. The solid and liquid CPs had different predominant congener groups for SCCPs and PCDD/Fs. Possible formation routes for the generation of PCDD/Fs were analyzed by screening precursors in paraffin and laboratory-scale thermochemical experiments of CPs. The transformation between 2,3,7,8-PCDD/Fs and non-2,3,7,8-PCDD/Fs was recognized by calculating the successive chlorination preference. The first reported occurrence of PCDD/Fs in CP commercial products indicated that exposure to CPs and downstream products might be an assignable source of PCDD/F emission, which is of great significance to further explore the control factors of PCDD/Fs in the whole life cycle of CPs.

Homologue Composition of Technical Chlorinated Paraffins Used in Several Countries over the Last 50 Years─SCCPs Are Still Out There

Chlorinated paraffins (CPs) are widely produced chemicals, with certain CP subgroups facing global restrictions due to their environmental dispersion, persistence, bioaccumulation, and toxicity. To evaluate the effectiveness of these international restrictions, we assessed the homologue group contribution and the mass fraction of short-chain CPs (SCCPs: C10-C13), medium-chain CPs (MCCPs: C14-C17), and long-chain CPs (LCCPs: ≥C18) in 36 technical CP mixtures used worldwide over the last 50 years. Using low-resolution mass spectrometry (LC-ESI-MS/MS), we quantified 74 CP homologue groups (C10Cl4-C20Cl10). Additionally, high-resolution mass spectrometry (LC-ESI-QTOF-MS) screening was employed to identify unresolved CP contents, covering 375 CP homologue groups (C6Cl4-C30Cl30). Overall, 1 sample was mainly composed of Collapse

Key Words

• chemical additive
• chlorinated n-alkane
• flame retardant
• persistent organic pollutant
• plasticizer
• polychlorinated alkane
• suspect screening analysis

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MESH Headings

• Paraffin
• Tandem Mass Spectrometry
• Chromatography, Liquid

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Grants Collapse

Affiliation(s)

Yago Guida Material Cycles Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, 21941-902 Rio de Janeiro, Brazil
Hidenori Matsukami Material Cycles Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
Gabriel Oliveira de Carvalho Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, 21941-902 Rio de Janeiro, Brazil
Roland Weber POPs Environmental Consulting, 73527 Schwäbisch Gmünd, Germany
Walter Vetter Institute of Food Chemistry (170b), University of Hohenheim, DE-70593 Stuttgart, Germany
Natsuko Kajiwara Material Cycles Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan

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Size distributions of molecular markers for biogenic secondary organic aerosol in urban Beijing

To understand the source, formation, and seasonality of biogenic secondary organic aerosol (BSOA), a nine-stage cascade impactor was utilized to collect size-segregated particulate samples from April 2017 to January 2018 in Beijing, China. BSOA tracers derived from isoprene, monoterpene, and sesquiterpene were measured with gas chromatography-mass spectrometry. Isoprene and monoterpene SOA tracers exhibited significant seasonal variations, with a summer maximum and a winter minimum. Dominance of 2-methyltetrols (isoprene SOA tracers) with a good correlation with levoglucosan (a biomass burning tracer), which was combined with the detection of methyltartaric acids (possible indicators for aged isoprene) in summer, implies possible biomass burning and long-range transport. In contrast, sesquiterpene SOA tracer (β-caryophyllinic acid) was dominant in winter and was probably associated with the local burning of biomass. Bimodal size distributions were observed for most isoprene SOA tracers, consistent with previous laboratory experiments and field studies showing that they can be formed not only in the aerosol phase but also in the gas phase. Monoterpene SOA tracers cis-pinonic acid and pinic acid showed a coarse-mode peak (5.8-9.0 μm) in four seasons due to their volatile nature. Sesquiterpene SOA tracer β-caryophyllinic acid showed a unimodal pattern with a major fine-mode peak (1.1-2.1 μm), which is linked to local biomass burning. The tracer-yield method was used to quantify the contributions of isoprene, monoterpene, and sesquiterpene to secondary organic carbon (SOC) and SOA. The highest isoprene SOC and SOA concentrations occurred in summer (2.00 μgC m^-3 and 4.93 μg m^-3, respectively), contributing to 1.61% of OC and 5.22% of PM_2.5, respectively. These results suggest that BSOA tracers are promising tracers for understanding the source, formation, and seasonality of BSOA.

The potential health risks of short-chain chlorinated paraffin: A mini-review from a toxicological perspective

Short-chain chlorinated paraffins (SCCPs) are ubiquitously distributed in various environmental matrics due to their wide production and consumption globally in the past and ongoing production and use in some developing countries. SCCPs have been detected in various human samples including serum, milk, placenta, nail, and hair, and internal SCCP levels were found to be positively correlated with biomarkers of some diseases. While the environmental occurrence has been reported in a lot of studies, the toxicity and underlying molecular mechanisms of SCCPs remain largely unknown. The current tolerable daily intakes (TDIs) recommended by the world health organization/international programme on chemical safety (WHO/IPCS, 100 μg/kg bw/d) and the UK Committee on Toxicity (COT, 30 μg/kg bw/d) were obtained based on a no observed adverse effect level (NOAEL) of SCCP from the repeated-dose study (90 d exposure) in rodents performed nearly 40 years ago. Importantly, the health risks assessment of SCCPs in a variety of studies has shown that the estimated daily intakes (EDIs) may approach and even over the established TDI by UK COT. Furthermore, recent studies revealed that lower doses of SCCPs could also result in damage to multiple organs including the liver, kidney, and thyroid. Long-term effects of SCCPs at environmental-related doses are warranted.

Health Risks Posed by Dermal and Inhalation Exposure to High Concentrations of Chlorinated Paraffins Found in Soft Poly(vinyl chloride) Curtains

Chlorinated paraffins (CPs) are used in many products, including soft poly(vinyl chloride) curtains, which are used in many indoor environments. Health hazards posed by CPs in curtains are poorly understood. Here, chamber tests and an indoor fugacity model were used to predict CP emissions from soft poly(vinyl chloride) curtains, and dermal uptake through direct contact was assessed using surface wipes. Short-chain and medium-chain CPs accounted for 30% by weight of the curtains. Evaporation drives CP migration, like for other semivolatile organic plasticizers, at room temperature. The CP emission rate to air was 7.09 ng/(cm² h), and the estimated short-chain and medium-chain CP concentrations were 583 and 95.3 ng/m³ in indoor air 21.2 and 172 μg/g in dust, respectively. Curtains could be important indoor sources of CPs to dust and air. The calculated total daily CP intakes from air and dust were 165 ng/(kg day) for an adult and 514 ng/(kg day) for a toddler, and an assessment of dermal intake through direct contact indicated that touching just once could increase intake by 274 μg. The results indicated that curtains, which are common in houses, could pose considerable health risks through inhalation of and dermal contact with CPs.

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.

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.

Accumulative levels, temporal and spatial distribution of common chemical pollutants in the blood of Chinese adults

China has been in a rapid development period in recent decades, the mass production and use of chemical industrial products and pesticides have resulted in a large amount of pollutants in the environment. These pollutants enter the human body through environmental exposure and dietary intake, causing adverse health effects. Although many of them have been banned and restricted in the production and use in China, these pollutants still remain in the human body due to their high persistence and strong bioaccumulation. In this review, we aim to reveal the accumulation levels and profiles, as well as the temporal and spatial distribution of common chemical pollutants including chlorinated paraffins (CPs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers, organophosphorus flame retardants (OPFRs), new halogenated flame retardants (NHFRs), polychlorinated biphenyls, phthalic acid esters, perfluorinated compounds, bisphenols, organophosphorus pesticides and pyrethroid insecticides in the blood (including whole blood, serum and plasma) of Chinese adults by extracting 93 related studies published from 1990 to 2021. Results have shown that CPs, OCPs and PAHs were the main pollutants in China, the levels of short-chain chlorinated paraffin, p,p'-DDE and phenanthrene in blood even reached 11,060.58, 740.41 and 498.28 ng/g lipid respectively. Under the strict control of pollutants in China, the levels of most pollutants have been on a downward trend except for perfluoro octanoate and perfluoro nonanoate. Besides, OPFRs, NHFRs and PAHs may have a potential upward trend, requiring further research and observation. As for spatial distribution, East China (Bohai Bay and Yangtze River Delta) and South China (Pearl River Delta) were the major polluted regions due to their fast development of industry and agriculture.

Medium- and long-chain chlorinated paraffins in air: A review of levels, physicochemical properties, and analytical considerations

Chlorinated paraffins (CPs) are synthetic chemicals that are produced at high volumes and have a global presence. CPs are generally divided into three groups based on their carbon chain lengths: short-chain CPs (SCCPs, C_10-13), medium-chain CPs (MCCPs, C_14-17), and long-chain CPs (LCCPs, C_≥18). SCCPs have been formally recognized as persistent organic pollutants (POPs) and have been listed under the Stockholm Convention on POPs. Concerns about increases in MCCP and LCCP production as replacements for SCCP products are rising, given their similar properties to SCCPs and the fact that they remain relatively understudied with only a few reported measurements in air. Passive air samplers with polyurethane foam disks (PUF-PAS), which have been successfully applied to SCCPs, provide an opportunity to expand the existing body of data on MCCP and LCCP air concentrations, as they are inexpensive and require little maintenance. The uptake of MCCPs and LCCPs by PUF disk samplers is characterized in this paper based on newly derived PUF-air partitioning coefficients using COSMOtherm. The ability of PUF disk samplers to capture both gas-phase and particle fractions is important because MCCPs and LCCPs have reduced volatility compared to SCCPs and therefore are mainly associated with particulate matter in air. In addition, due to their use as additives in plastics and rubber products, they are associated with micro- and nanoplastics, which are considered to be potential vectors for the long-range atmospheric transport (LRAT) of these chemicals. The review has highlighted other limitations to reporting of MCCPs and LCCPs in air, including the lack of suitable analytical standards and the requirement for advanced analytical methods to detect and resolve these complex mixtures. Overall, this review indicates that further research is needed in many areas for medium- and long-chain chlorinated paraffins in order to better understand their occurrence, transport and fate in air.

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.

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. C₁₄-₁₅Cl_7-9 were the dominant CP congener groups in the soil samples. C₁₀Cl_6-7 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.

Identifying emerging environmental concerns from long-chain chlorinated paraffins towards German ecosystems

Germany is one of several major European producers of chlorinated paraffins (CPs). This study showed that not only the legacy short-chain products (SCCPs, C_10-13), but also the current-use medium- and long-chain products (MCCPs, C_14-17; LCCPs, C_>17) as well as the very-short-chain impurities (vSCCPs, C_<10) are ubiquitous in the 72 samples collected from the coastal, terrestrial, and freshwater ecosystems across the country. The concentrations of LCCPs surpassed those of the other CPs in 40% of the biota samples. Archived bream samples collected downstream of a CP-manufacturing factory showed decreasing temporal trends of (v)SCCPs and relatively constant levels of MCCPs from 1995 to 2019; however, the overall levels of LCCPs have increased by 290%, reflecting the impact of chemical regulation policies on changes in CP production. A visualization algorithm was developed for integrating CP results from various matrices to illustrate spatial tendencies of CP pollution. Higher levels of (v)SCCPs were indicated in the former West Germany region, while MCCP and LCCP concentrations did not seem to differ between former East and West Germany, suggesting relatively equal production and use of these chemicals after the German Reunification. The results provide an early warning signal of environmental concerns from LCCPs on the eve of their booming global production and use.

Short- and medium-chain chlorinated paraffins in soil from an urban area of northern China: Levels, distribution, and homolog patterns

Short-chain chlorinated paraffins (SCCPs) are persistent organic pollutants that are present in relatively high concentrations in various environmental media in China. Many studies have focused on chlorinated paraffins in soil from agricultural land and contaminated areas. There are limited data on the levels of chlorinated paraffins in soil from urban areas. In this study, to investigate the levels, distribution, and homolog patterns of chlorinated paraffins (CPs) in soil from a typical urban area, 130 soil samples were collected and combined to form 26 pooled samples. The samples were analyzed for 50 CP congener groups (C_9-17Cl_5-10). The concentration ranges for SCCPs, medium-chain CPs (MCCP), and chlorinated nonane paraffin (C₉-CP) were 19-1456 ng/g (average: 234 ng/g), <10-385 ng/g (average: 54 ng/g), and 1-39 ng/g (average: 11 ng/g), respectively. The CP concentrations were not significantly correlated with the total organic carbon content (P > 0.05). Compared with other areas worldwide, the SCCP and C₉-CP concentrations in soil in this area were at the medium level, and the concentrations of MCCPs were at a low level. The CP concentrations were higher in soil samples collected near factories and domestic garbage disposal sites. C₁₀Cl_6-7 were the main SCCP homologs and C₁₄Cl_7-8 were the main MCCP homologs. Principal component analysis showed that the sources of C₉-CPs, SCCPs, and MCCPs in the soils were similar. Risk assessment showed that the concentrations of SCCPs and MCCPs in soil in this area did not pose a significant risk to soil organisms or human health.

Release of phthalate esters from a local landfill in the Tibetan Plateau: Importance of soil particle-size specific association

High loads of phthalate esters (PAEs) in background regions can be directly attributed to the local sources, and their association with soil particles may determine the environment behaviors. However, little is known about the particle-size specific distributions of PAEs in soils from point source to the surroundings. In this study, 12 PAE congeners were measured in clay (< 2 μm), silt (2-63 μm) and sand fractions (63-250 μm) from surficial soils and soil profiles (0-200 cm) around the Lhasa landfill. The total concentrations of PAEs in bulk soils varied from 0.44 to 22.3 μg/g, with a dominance of bis(2-ethylhexyl) phthalate (DEHP). The clay-sorbed PAEs exhibited a decreasing trend with the increasing distance from landfill. This distribution pattern was well described by the Gaussian air pollution model, suggesting the airborne particles/gaseous transport of clay-sorbed PAEs. The Boltzmann equation explained the spatial variation of silt-sorbed PAEs, reflecting the atmospheric dispersion of silt-sorbed PAEs. In comparison, the sand-sorbed PAEs in surrounding soils showed downslope accumulation possibly due to the aeolian transport of sand particles. Half-life of the most abundant PAE congener DEHP was assumed based on the soil inventories from observed concentration and the Level III fugacity model simulations, and the results indicated significant longer half-life of DEHP in deeper soils (~24,000 h) than in surficial soils (5500 h). This study elucidates that the distribution and fate of soil PAEs would depend on their association with particles in the source area, and the relative stability of DEHP in deeper soils would further increase PAE inventory in soil compartment.

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.

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.

Status of short-chain chlorinated paraffins in matrices and research gap priorities in Africa: a review

Chlorinated paraffins (CPs) have been applied as additives in a wide range of consumer products, including polyvinyl chloride (PVC) products, mining conveyor belts, paints, sealants, adhesives and as flame retardants. Consequently, CPs have been found in many matrices. Of all the CP groups, short-chain chlorinated paraffins (SCCPs) have raised an alarming concern globally due to their toxicity, persistence and long-range transportation in the environment. As a result, SCCPs were listed in the Stockholm Convention on Persistent Organic Pollutants (POPs) in May 2017. Additionally, a limit for the presence of SCCPs in other CP mixtures was set at 1% by weight. CPs can be released into the environment throughout their life cycle; therefore, it becomes crucial to assess their effects in different matrices. Although about 199 studies on SCCP concentration in different matrices have been published in other continents; however, there are scarce/or limited studies on SCCP concentration in Africa, particularly on consumer products, landfill leachates and sediment samples. So far, published studies on SCCP concentration in the continent include SCCPs in egg samples, e-waste recycling area and indoor dust in Ghana and South Africa, despite absence of any production of SCCPs in Africa. However, there still remains a huge research gap in the continent of Africa on SCCPs. Consequently, there is a need to develop robust SCCP inventories in Africa since the Stockholm Convention has already developed guidance document in this respect. This review, therefore, examines the state of knowledge pertaining to the levels and trends of these contaminants in Africa and further provides research gaps that need to be considered in order to better understand the global scale of the contaminant.

Exposure to short-chain chlorinated paraffins inhibited PPARα-mediated fatty acid oxidation and stimulated aerobic glycolysis in vitro in human cells

Short-chain chlorinated paraffins (SCCPs) could disrupt fatty acid metabolism in male rat liver through activating rat PPARα signaling. However, whether this mode of action can translate to humans remained largely unclear. In this study, based on luciferase assays, C_10-13-CPs (56.5% Cl) at concentrations greater than 1 μM (i.e., 362 μg/L) showed weak agonistic activity toward human PPARα (hPPARα) signaling. But in HepG2 cells, exposure to C_10-13-CPs (56.5% Cl) at the human internal exposure level (100 μg/L) down-regulated expressions of most of the tested hPPARα target genes, which encode for enzymes that oxidize fatty acids. In line with the gene expression data, metabolomics further confirmed that exposure to four SCCP standards with varying chlorine contents at 100 μg/L significantly suppressed oxidation of fatty acids in HepG2 cells, mainly evidenced by elevations in both total fatty acids and long-chain acylcarnitines. In addition, exposure to these SCCPs also caused a shift in carbohydrate metabolism from the tricarboxylic acid cycle (TCA cycle) to aerobic glycolysis. Overall, the results revealed that SCCPs could inhibit hPPARα-mediated fatty acid oxidation, and stimulated aerobic glycolysis in HepG2 cells.

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.

Disentangling the contributions of urban and production sources in short- and medium-chain chlorinated paraffin concentrations in a complex source region

Short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) were measured in tree bark samples. These samples were collected around a chemical industrial park containing several chlorinated paraffin (CP) production plants, in a nearby city (Zhengzhou), and along a transect between the industrial park and city. Theoretical air concentrations were back-calculated from concentrations in bark using a predictive equation for estimating equilibrium bark-air partition coefficients. We developed this equation from a series of previously published K_bark-air measurements. Comparison of the normalized concentration profiles along south to north transects showed that wind played only a minor role in CP concentrations and profiles in the region. Three distinct source profiles were found in the complex source region. A fingerprint analysis technique was used to quantify the contribution of each source to the CP burden at various locations along the transect. We found that CP profiles at sites up to 6 km from the industrial park were strongly influenced by CP plant emissions, whereas the sites located in the rural zone and rural-urban interface were influenced by a mixture of CP plant emissions and the neighboring city.

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.

Protein-affinity guided identification of chlorinated paraffin components as ubiquitous chemicals

Chlorinated paraffins (CPs) have been extensively examined to identify their components. Short-chain CPs with a carbon number of 10-13 have been strictly restricted or banned due to their addition to the list of Persistent Organic Pollutants in the world. However, more constituents with potential toxicities in these complicated mixtures are still unclear. In the present study, a purification method based on the protein affinity of thyroid hormone-related proteins (transthyretin and thyroid receptor) was established. The protein-based affinity extraction coupled with high-throughput scanning successfully discover a new group of chlorinated compounds (CP(O₂)) in commercial CP mixtures. The CP(O₂)s were purified from the commercial mixtures and identified to be chlorinated fatty acid methyl esters (CFAMEs) with a carbon chain length of 17-19 and 3-11 chlorines by a combination of liquid-liquid extraction, hydrolysis, Fourier transform infrared spectrometry and Orbitrap mass spectrometry. The newly identified CFAMEs were found to be ubiquitous in the environmental matrices, and concentration ratios of ∑CFAMEs/∑CPs ranged from 0.01 to 35 in air, soil and food samples. CFAMEs were also detected in blood samples of general populations, and accumulated in humans through dietary uptake. CFAMEs can compete with T4 for binding TTR with higher potencies than CPs, possibly leading to disruptions of thyroid hormone homeostasis.

Occurrence of short- and medium-chain chlorinated paraffins in soils and sediments from Dongguan City, South China

As a group of emerging organic pollutants, chlorinated paraffins (CPs) have attracted rising global attention due to their persistence and toxicity. In this study, we have investigated the concentration levels and profiles of short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) in soils and sediments from Dongguan City, an industrial area in South China, and have also screened very short-chain chlorinated paraffins (vSCCPs) by means of ultra-high resolution liquid chromatograph coupled with an Orbitrap Fusion Tribrid mass spectrometer. The results indicated that total SCCP concentrations ranged from 6.75 to 993 ng/g (mean 172 ng/g) in soils and from 4.00 to 613 ng/g (mean 153 ng/g) in sediments, respectively. Higher MCCP levels were observed with a range of 23.9-2427 ng/g (mean 369 ng/g) in soils and 14.0-1581 ng/g (mean 493 ng/g) in sediments, respectively. The results indicated that MCCPs dominated over SCCPs in the studied region. The dominant homologues in soils and sediments were C₁₃Cl_6-7 and C₁₄Cl_7-8, C₁₃Cl₇, and C₁₄Cl_7-8, respectively. Furthermore, six vSCCP homologues (C₈Cl_7-8 and C₉Cl_5-8) in soils and four vSCCPs (C₉Cl_5-8) in sediments have been identified. Because of their higher detection frequencies, further studies should focus on the transformation mechanisms and toxicities of these vSCCPs in environmental media and biota.

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.

Distributions of chlorinated paraffins and the effects on soil microbial community structure in a production plant brownfield site

The distributions of chlorinated paraffins (CPs) in soils and their ecological effects attract much attention, while site-scale data are still scarce. In this study, a comprehensive investigation was performed to understand the CP distributions at a CP production plant brownfield site, as well as their effects on soil microbial community. Short-, medium- and long-chain CPs (SCCPs, MCCPs, LCCPs) were detected in most samples with total contents ranging ND-5,090, ND-6,670, and ND-1450 ng g^-1 (dw), respectively. A CP-hotspot was observed 10 m beneath the synthesis workshop, indicating the downward migration of CPs. The consistence of soil SCCP congener profiles with commercial product CP-52 suggested the leakage of CP products as the contamination source. Besides CPs, petroleum hydrocarbons (PHC) contamination also occurred beneath the synthesis workshop. Soil microbial community composition and diversity were significantly influenced by SCCPs (p < 0.05) despite their lower contents compared to other concerned contaminants. Microbial network analysis indicated nonrandom co-occurrence patterns, with Acinetobacter, Brevibacterium, Corynebacterium, Microbacterium, Stenotrophomonas, and Variibacter as the keystone genera. Genera from the same module showed significant ecological links (p < 0.05) and were involved in the degradation of PHCs and chlorinated organic contaminants. This study provides the first phylogenetic look at the microbial communities in CP contaminated soils, indicating that the long-term exposure to CPs and PHCs may lead to microbial group assemblages with the potential for degradation.

Spatial distributions and homolog profiles of chlorinated nonane paraffins, and short and medium chain chlorinated paraffins in soils from Yunnan, China

To preliminarily investigate the occurrence, spatial distributions, homolog compositions, and ecological risks of chlorinated paraffins (CPs) in Yunnan, China, 110 soil samples were collected from an area part of Yunnan, representative of the whole Yunnan area, where had similar characteristics to most parts of Yunnan and 22 pooled soil samples were analyzed for 50 CP congener groups (C₉-₁₇Cl_5-10). The chlorinated nonane paraffin (C₉-CP), short chain (SCCP), and medium chain chlorinated paraffin (MCCP) concentrations in soil samples were 8-109 ng/g (average 39 ng/g), 79-948 ng/g (average 348 ng/g), and 20-1206 ng/g (average 229 ng/g), respectively. The C₉-CP homologs contributed 5%-16% of the C_9-13-CP concentrations in soils. No significant correlation was found between CP concentrations and the total organic carbon content (P > 0.05). The CP levels in soils from Yunnan were at a medium level compared with those in other areas worldwide. Human activity and atmosphere deposition would influence the levels and spatial distributions of CPs in this area. The concentrations of CPs in east area were higher than those in west area. C₁₀Cl_6-7 were the major SCCP congeners and C₁₄Cl_6-7 were the major MCCP congeners. Principal component analysis indicated that SCCPs and MCCPs came from different sources. A preliminary risk assessment indicated that these concentrations of CPs in soil from Yunnan do not pose a significant ecological risk for soil organisms.

Spatiotemporal variations of chlorinated paraffins in PM2.5 from Chinese cities: Implication of the shifting and upgrading of its industries

To highlight the levels and distributions and to assess the risk of human exposure of chlorinated paraffins (CPs) in PM_2.5 in China, the concentrations and homologue patterns of short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) in PM_2.5 from 10 cities in China were studied in 2013 and 2014. The mean concentrations of ΣSCCPs and ΣMCCPs were 19.9 ± 41.1 ng m^-3 and 15.6 ± 18.6 ng m^-3, respectively. Unexpectedly, the highest pollution levels occurred in two central cities (Xinxiang and Taiyuan) rather than in well-known eastern megacities such as Beijing, Nanjing, Shanghai, and Guangzhou. By comparing with earlier research, it has indicated the trend of CPs industry shifting from large eastern cities to small and medium-sized cities in central China to some extent. In addition, the composition pattern of SCCPs demonstrated an obviously differences from previous studies, with C₁₁ and Cl₇ predominating and accounting for 45.1% and 24.9%, respectively. Meanwhile, the ratio of MCCPs/SCCPs in most cities was less than 1.00 except for Guangzhou (1.92), Shanghai (1.29), and Taiyuan (1.11). Combined with the results of correlation analysis and principal component analysis, the observed pollution characteristics of CPs in PM_2.5 had similar sources, which were more influenced by the ratio of MCCPs/SCCPs than by organic carbon, elemental carbon, temperature, population, and gross domestic product. Overall, the composition of CPs reflected the characteristics of local industrial production and consumption, and also implied efforts of Chinese enterprises to reduce the content of short carbon groups of CPs production. The CPs mainly deposited in head airways during the process of entering the human respiratory system. However, at the present levels, there was no significant carcinogenic effect for human health.

Soil pollution at a major West African E-waste recycling site: Contamination pathways and implications for potential mitigation strategies

Organic contaminants (polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and chlorinated paraffins (CPs)) and heavy metals and metalloids (Ag, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Zn) were analysed in surface soil samples from the Agbogbloshie e-waste processing and dumping site in Accra (Ghana). In order to identify which of the pollutants are likely to be linked specifically to handling of e-waste, samples were also collected from the Kingtom general waste site in Freetown (Sierra Leone). The results were compared using principal component analyses (PCA). PBDE congeners found in technical octa-BDE mixtures, highly chlorinated PCBs and several heavy metals (Cu, Pb, Ni, Cd, Ag and Hg) showed elevated concentrations in the soils that are likely due to contamination by e-waste. PCAs associated those compounds with pyrogenic PAHs, suggesting that burning of e-waste, a common practice to isolate valuable metals, may cause this contamination. Moreover, other contamination pathways, especially incorporation of waste fragments into the soil, also appeared to play an important role in determining concentrations of some of the pollutants in the soil. Concentrations of several of these compounds were extremely high (especially PBDEs, heavy metals and SCCPs) and in some cases exceeded action guideline levels for soil. This indicates that exposure to these contaminants via the soil alone is potentially harmful to the recyclers and their families living on waste sites. Many organic contaminants and other exposure pathways such as inhalation are not yet included in such guidelines but may also be significant, given that deposition from the air following waste burning was identified as a major pollutant source.

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.

Short-chain chlorinated paraffins (SCCPs) disrupt hepatic fatty acid metabolism in liver of male rat via interacting with peroxisome proliferator-activated receptor α (PPARα)

Short-chain chlorinated paraffins (SCCPs) are frequently detected in environmental matrices and human tissues. It was hypothesized that SCCPs might interact with the peroxisome proliferator-activated receptor α (PPARα). In the present study, an in vitro, dual-luciferase reporter gene assay and in silico molecular docking analysis were employed together to study the interactions between SCCPs congeners and PPARα. Expressions of genes downstream in pathways activated by PPARα in liver of rats exposed to 1, 10, or 100 mg/kg bm/d of C_10-13-CPs (56.5% Cl) for 28 days were examined to confirm activation potencies of SCCPs toward PPARα signaling. Effects of exposure to C_10-13-CPs (56.5% Cl) on fatty acid metabolism in rat liver were also explored via a pseudo-targeted metabolomics strategy. Our results showed that C_10-13-CPs (56.5% Cl) caused a dose-dependent greater expression of luciferase activity of rat PPARα. Molecular docking modeling revealed that SCCPs had a strong capacity to bind with PPARα only through hydrophobic interactions and the binding affinity was dependent on the degree of chlorination in SCCPs congeners. In livers of male rats, exposure to 100 mg/kg bm/d of C_10-13-CPs (56.5% Cl) resulted in up-regulated expressions of 11 genes that are downstream in the PPARα-activated pathway and regulate catabolism of fatty acid. Consistently, accelerated fatty acid oxidation was observed mainly characterized by lesser concentrations of ∑fatty acids in livers of rats. Overall, these results demonstrated, for the first time, that SCCPs could activate rat PPARα signaling and thereby disrupt metabolism of fatty acid in livers of male rats.

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.

Short-chain chlorinated paraffins in soil, sediment, and seawater in the intertidal zone of Shandong Peninsula, China: Distribution and composition

Short-chain chlorinated paraffins (SCCPs) are components of chlorinated paraffins (CPs) with high persistence, bioaccumulation potential, and toxicity, and SCCPs have been listed on Stockholm Convention as persistent organic pollutants. In this work, we investigated the distribution and homologue group patterns of SCCPs in the intertidal zone of the Shandong Peninsula, which is surrounded by the Bohai Sea (BS) and Yellow Sea (YS). Total SCCP concentrations (ΣSCCPs) in the samples from the sites along the coast of BS were 64.14-452.9 ng/g (mean = 181.0 ng/g), which were higher than those of the YS (17.59-155.5 ng/g, mean = 108.5 ng/g). ΣSCCPs were generally higher in intertidal sediments than in coastal soils along the BS, which could be ascribed to local industrial emissions through river runoff and mid-estuarine maximum phenomenon that resulted from seawater intrusion. In contrast, the opposite trend was observed along the YS. The contribution of shorter chain (C₁₀) and lower chlorinated (Cl_5-7) SCCP congeners was higher when the sampling sites were more proximal to the sea than heavier ones because of their greater potential for long-range transportation. Similar homologue group patterns were observed in the intertidal zone of Shandong, thus indicating a uniform use of commercial CP mixtures. High SCCP concentrations and similar homologue group patterns as those of the STP effluent were observed in seawater samples, thus suggesting that massive insufficiently purified or nonpurified industrial effluents were discharged into the BS.

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.

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.

Short-chain chlorinated paraffin (SCCP) pollution from a CP production plant in China: Dispersion, congener patterns and health risk assessment

China is the largest chlorinated paraffin (CP) producer in the world. Given that CP production is a major source of short-chain CP (SCCP) pollution in China, the effects of CP production on the environment inside and outside of CP production plants are worth revealing. The concentrations and specific congener group patterns of SCCPs in various environmental matrices, such as air, soil and dust, inside and outside of a chosen CP production plant surrounded by farmlands and villages were analyzed to explore SCCP pollution and transportation behaviors. SCCP concentrations in air (129-1442 ng/m³) and soil (28-554 μg/g) samples inside the CP production plant were dramatically higher than those in air (91-333 ng/m³) and soil (102-441 ng/g) samples outside the CP production plant. Based on the congener abundance patterns among these samples, lighter groups (C_10-11 and Cl_5-6) were dominant in atmospheric environment, with greater long-range transport potential, whereas heavier groups (C_12-13 and Cl_7-10) were inclined toward deposition. It was clear that substantial amounts of SCCPs were released from the CP production plant, which contaminated the environment inside and outside of the plant. The daily occupational SCCP exposure of employees in the production hall (21.8 μg/day-kg) exceeded the tolerable daily intake (TDI, 10 μg/day-kg) given by Canadian Environmental Protection Act, suggesting that production employees were confronted with high health risk from SCCP exposure; while daily SCCP exposure of employees in office areas (0.57 μg/day-kg) and residents near the CP plant (1.22-25.5 × 10^-2 μg/day-kg) were significantly lower, representing low health risk.

Short- and medium-chain chlorinated paraffins in the Henan section of the Yellow River: Occurrences, fates, and fluxes

Short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) were measured in sediment and suspended particulate matter (SPM) from the middle and lower reaches of the Yellow River in the three seasons to elucidate their environmental behavior. The mean concentrations of ∑SCCPs and ∑MCCPs were 262 and 97.1 ng g^-1 dw (dry weight) in sediment and 17,055 and 2573 ng g^-1 dw in SPM, respectively, and higher SCCP levels did not clearly reflect a shift to more MCCPs in this section of the Yellow River. The predominant homologue groups were C₁₀-CP and C₁₁-CP for SCCPs and C₁₄-CP for MCCPs. The CPs possibly mainly derived from the use of CP commercial mixtures, mainly included CP-42 and CP-52. The spatial distributions and principal component analysis indicated that industrial inputs, dams, and topography played important roles in influencing the environmental behavior of CPs in both sediment and SPM. In addition, decreasing fluxes of CPs were observed in SPM from Tongguan to Aishan stations, particularly in reservoirs, which implies that CPs may have accumulated in the Henan section of the Yellow River.

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.

Insight into the photocatalytic mineralization of short chain chlorinated paraffins boosted by polydopamine and Ag nanoparticles

Short chain chlorinated paraffins (SCCPs) have attracted increasing attention recently due to their widespread occurrence and persistence in the environment, long-distance transport, and bioaccumulation and toxicity. For the sake of photocatalytic elimination of SCCPs, a kind of polydopamine (PDA) based photocatalyst, echinus-like Fe₂O₃@PDA-Ag hybrids have been synthesized via coating Fe₂O₃ with PDA by self-polymerization of dopamine and further loading silver nanoparticles by in situ reduction onto the surface of PDA shell. The photogenerated charges of Fe₂O₃@PDA-Ag hybrids exhibit long lifetime from transient photovoltage signal, which is of benefit to participate in various subsequent reaction processes before their recombination. Benefiting from the coating of PDA shell and the deposition of Ag nanoparticles, Fe₂O₃@PDA-Ag hybrids exhibit enhanced photocatalytic activity for the removel of SCCPs as investigated by the in situ Fourier transform infrared spectroscopy, 2.9 times as high as that of Fe₂O₃, due to the reactive OH radicals. The density functional theory simulation demonstrates the key mechanism of the formation of conjugate bond in the dechlorination process as well as the final product of HCl. The simulation indicates that there are no regularities for the H-abstraction but the dechlorination usually occurs in the adjacent Cl atoms next to the C with H-abstraction.