Occurrence, fate and ecological risk of chlorinated paraffins in Asia: A review

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

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

From environment to free-range chickens: Broad exposure to short- and medium-chain chlorinated paraffins in rural Tibetan Plateau, China

Chlorinated paraffins (CPs) are widely employed in various consumer products. Rapid socioeconomic development drives the elevation of CPs contamination by increasing the usage of modern lifestyle products, but limited information exists about their occurrence in remote rural areas. In this study, the occurrence, and profiles of short- and medium-chain CPs (SCCPs and MCCPs) in soils, plants, chicken feeds, eggs, and free-range chicken tissues in the rural Tibetan Plateau were investigated. The median concentrations of SCCPs and MCCPs were 108 and 141 ng/g dry weight (dw) in soils, 1.76 × 103 and 1.16 × 103 ng/g dw in plants, 43.6 and 24.3 ng/g dw in chicken feeds, 299 and 251 ng/g lipid weight in free-range chicken eggs, and 182 -3.45 × 103 and 396 -7.75 × 103 ng/g lipid weight in chicken tissues, respectively. Correlation analysis demonstrated that soil was the primary source of CPs, and free-range chicken eggs were effective bioindicators for SCCPs and MCCPs contamination. Tissue distribution showed that SCCPs and MCCPs were highly accumulated in chicken tissues that local resident preferred to consume (such as muscle and stomach). Our findings lay the foundations for further evaluation of the potential risks of CPs on the ecosystem and human health in remote rural areas.

Spatial distribution and ecological risk assessment of short and medium chain chlorinated paraffins in water and sediments of river Ravi, Pakistan

Short (SCCPs) and medium (MCCPs) chain chlorinated paraffins being the emerging organic pollutants have raised serious concerns due to their widespread use and related human health risks. However, their occurrence in aquatic bodies like rivers and associated damage to ecological integrity is yet unknown in some regions of the world. The current study is the first ever assessment of SCCPs and MCCPs in sediment and water of river Ravi, Pakistan. Spatial occurrence and associated ecological risks were investigated from sediments (n = 16) and composite water samples (n = 8) collected at eight locations along the stretch of river Ravi. The concentrations of SCCPs and MCCPs varied from below limit of detection ( Collapse

Key Words

• Aquatic body
• Partitioning coefficient
• Risk assessment
• Source identification
• Total organic carbon

Collapse

MESH Headings

• Humans
• Animals
• Chlorine
• Hydrocarbons, Chlorinated/analysis
• Paraffin/analysis
• Rivers
• Pakistan
• Environmental Monitoring
• Risk Assessment
• Carbon
• China

Collapse

Grants Collapse

Affiliation(s)

Areej Tahir College of Earth and Environmental Sciences, University of the Punjab, Lahore 54590, Pakistan
Naeem Akhtar Abbasi College of Earth and Environmental Sciences, University of the Punjab, Lahore 54590, Pakistan.
Chang He Queensland Alliance for Environmental Health Science, The University of Queensland, Brisbane 4102, Australia; Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health, Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, PR China; Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, PR China
Sajid Rashid Ahmad College of Earth and Environmental Sciences, University of the Punjab, Lahore 54590, Pakistan
Mujtaba Baqar Sustainable Development Study Centre, Government College University, Lahore 54000, Pakistan
Abdul Qadir College of Earth and Environmental Sciences, University of the Punjab, Lahore 54590, Pakistan

Collapse

Health risk assessment and development of human health ambient water quality criteria for PCBs in Taihu Basin, China

Polychlorinated biphenyls (PCBs) are a class of typical persistent organic pollutants (POPs) with carcinogenicity and extensively found in diverse environmental mediums. The Taihu Basin is one of the most economically developed regions in China, and it has also caused a lot of historical legacy and unconscious emissions of PCBs, posing a threat to the health of people in the region. This study counted the concentrations of PCBs in five environmental media (water, soil, air, dust, and food) in the Taihu Basin from 2000 to 2020 and used Monte Carlo simulation to simulate the multi-channel exposure of PCBs in people of different ages (children, teenagers, and adults), and evaluated their noncarcinogenic and carcinogenic health risks. Finally, the human health ambient water quality standards (AWQC) for PCBs were obtained using regional exposure parameters and bioaccumulation factors. The results showed that the pollution of PCBs in the Taihu Basin was relatively serious in China. The concentration of PCBs in dust is higher than other environmental media. And exposure to water and food is the main exposure pathway for PCBs in the population of the region. Besides, PCBs pose no noncarcinogenic risk to people in this region, but their carcinogenic risk to residents exceeds the safety threshold. Among the three population groups, adults have the highest risk of cancer, and prevention measures need to be taken by controlling the intake of related foods and the concentration of PCBs in water. The following human health AWQC values of the PCBs in Taihu Basin is 3.2 × 10-9 mg/L.

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

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

Exploring long-term global environmental impacts of chlorinated paraffins (CPs) in waste: Implications for the Stockholm and Basel Conventions and the global plastic treaty

Chlorinated paraffins (CPs), mainly short-chain CPs (SCCPs) and medium-chain CPs (MCCPs), are currently the most produced and used industrial chemicals related to persistent organic pollutants (POPs) globally. These chemicals are widely detected in the environment and in the human body. As the release of SCCPs and MCCPs from products represents only a small fraction of their stock in products, the potential long-term release of CPs from a large variety of products at the waste stage has become an issue of great concern. The results of this study showed that, by 2050, SCCPs and MCCPs used between 2000 and 2021 will cumulatively generate 226.49 Mt of CP-containing wastes, comprising 8610.13 kt of SCCPs and MCCPs. Approximately 79.72 Mt of CP-containing wastes is predicted to be generated abroad through the international trade of products using SCCPs and MCCPs. The magnitude, distribution, and growth of CP-containing wastes subject to environmentally sound disposal will depend largely on the relevant provisions of the Stockholm and Basel Conventions and the forthcoming global plastic treaty. According to multiple scenarios synthesizing the provisions of the three conventions, 26.6-101.1 Mt of CP-containing wastes will be subject to environmentally sound disposal as POP wastes, which would pose a great challenge to the waste disposal capacity of China, as well as for countries importing CP-containing products. The additional 5-year exemption period for MCCPs is expected to see an additional 10 Mt of CP-containing wastes subject to environmentally sound disposal. Thus, there is an urgent need to strengthen the Stockholm and Basel Conventions and the global plastic treaty.

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

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

Short- and medium-chain chlorinated paraffins in sediment from the Haihe River Basin: Sources, distributions, and ecological risk assessment

Chlorinated paraffins (CPs) can accumulate in sediment and pose risks to ecological systems and human health. The Haihe River Basin is one of the seven main river basins in China and is mainly in the Beijing-Tianjin-Hebei region, which is densely populated and very urbanized. There is therefore a high probability of CP pollution in the Haihe River Basin. However, CP pollution and the environmental risks posed by CPs in the Haihe River are not well understood. In this study, the concentrations of short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) in sediment from six rivers in the Haihe River Basin system were determined using two-dimensional gas chromatography electron-capture negative ionization mass spectrometry. The total SCCP and MCCP concentrations in the sediment samples ranged from 131.83 to 1767.71 and from 89.72 to 1442.82 ng/g dry weight, respectively. The total organic carbon content did not significantly correlate with the CP concentrations. The dominant SCCP congener groups were C10Cl6-7 and the dominant MCCP congener groups were C14Cl7-8. Significant relationships (R = 0.700, p < 0.05) were found between the SCCP and MCCP concentrations, indicating that SCCPs and MCCPs may have similar sources. Hierarchical cluster analysis and principal component analysis indicated that sediment in the study area was contaminated with CPs through the use of the CP-42 and CP-52 commercial products in industrial processes and human activities. The ecological risks posed by CPs were assessed and SCCPs were found to pose high risks in the Yongding New River but moderate risks in the other rivers. MCCPs were found to pose minimal risks to the aquatic environment at most of the sampling points.

Short-chain chlorinated paraffin (SCCP) exposure and type 2 diabetes risk: A population-based case-control study in East China

Exposure to persistent organic pollutants may be associated to type 2 diabetes, but the studies on associations between short-chain chlorinated paraffin (SCCP) exposure and type 2 diabetes risk in humans are still scarce. Here, we conducted a case-control study involving 344 participants in Shandong Province, East China, to explore the effects of SCCPs on type 2 diabetes risk and their correlations with glycemic biomarker and serum lipid parameters. SCCPs were detected in all serum samples with a median concentration of 24 ng mL-1 in cases and 19 ng mL-1 in controls. Exposure to C10-CPs, C11-CPs, and ΣSCCPs were positively associated with the risk of type 2 diabetes after adjusting for confounders. The associations remained consistent in stratified analyses but stronger in male participants and obese individuals. In the control group, there were significant and positive correlations between SCCP exposure and levels of total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), total lipid, and non-high-density lipoprotein-cholesterol. Significant joint effects on SCCP exposure and lipid parameters were observed in females when analyzed by the quantile-based g-computation model, and C10-CPs showed the highest contribution. Mediation analysis showed that LDL-C had significant mediation effects on the associations between C10-CPs, C11-CPs, and ΣSCCPs exposure and risk of type 2 diabetes. Moreover, TC and high-density lipoprotein-cholesterol were mediators in the relationship between C11-CPs and type 2 diabetes. Taken together, our study revealed that human exposure to SCCPs may increase the risk of type 2 diabetes and disrupt lipid metabolism.

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.

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

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

Spatially Resolved Co-Imaging of Polyhalogenated Xenobiotics and Endogenous Metabolites Reveals Xenobiotic-Induced Metabolic Alterations

A large group of polyhalogenated compounds has been added to the list of persistent organic pollutants in a global convention endorsed by over 100 nations. Once entering the biotas, these pollutants are transported to focal sites of toxicological action and affected endogenous metabolites, which exhibited distinct tissue or organ distribution patterns. However, no study is available to achieve simultaneous mapping of the spatial distributions of xenobiotics and endogenous metabolites for clarifying the molecular mechanism of toxicities. Herein, we present a sensitive mass spectrometry imaging method─tetraphenyl phosphonium chloride-enhanced ionization coupled with air flow-assisted ionization-Orbitrap mass spectrometry─which simultaneously determined the spatial distributions of polyhalogenated xenobiotics and endogenous metabolites. The spatially resolved toxicokinetics and toxicodynamics of typical polyhalogenated compounds (chlorinated paraffins (CPs) and hexabromocyclododecane (HBCD)) were assessed in zebrafish. Co-imaging of polyhalogenated compounds and metabolites visualized the major accumulation organs and maternal transfer of HBCD and CPs, and it clarified the reproductive toxicity of HBCD. CPs were accumulated in the liver, heart, and brain and decreased the concentrations of polyamine/inosine-related metabolites and lipid molecules in these organs. HBCD accumulated in the ovary and was effectively transferred to eggs, and it also disrupted normal follicular development and impaired the production of mature eggs from the ovary by inhibiting expressions of the luteinizing hormone/choriogonadotropin receptor gene. The toxic effects of metabolic disruptions were validated by organ-specific histopathological examinations. These results highlight the necessity to assess the distributions and bioeffects of pollutants in a spatial perspective.

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.

Interlaboratory trial of short-chain chlorinated paraffin: comparison of mass fractions and homolog profiles in a simulation environmental sample

Short-chain chlorinated paraffins (SCCPs) are listed in the Stockholm Convention. Therefore, selecting suitable methods for their accurate quantification is essential. Nowadays, the quality of commercial reagents employed as quantification standards is not guaranteed. As a solution, we adopted an SCCP formulation reference material with known homolog composition ratios as the quantification standard to evaluate the appropriateness of the methods. By mixing the SCCP formulation and interferences, an analytical sample was independently prepared and used as the simulation environmental sample. The homolog compositional profiles of the SCCPs resembled those of the quantification standard and the analytical sample. The mass fractions and the homolog profiles, including the carbon chain length and chlorine homolog profiles, of the SCCPs were reported by 14 different laboratories. For the mass fraction, the results reported by participants were consistent, except for the participants that employed low-resolution gas chromatography (GC). The results generated from liquid chromatography (LC) and GC were slightly different, despite of the similar homolog composition ratios between the quantification standard and the analytical sample. Although there were discreet discrepancies in the overall chlorine homolog profiles, the carbon chain length profiles acquired from GC and LC were similar. The differences depended on the method employed. Additionally, compared with the low-resolution data, the high-resolution data displayed less fluctuation since the effect of the interferences on the analytical sample was reduced because of the mass accuracy of high-resolution instruments. Accordingly, the interlaboratory trial employing the similar homolog compositional profiles of the quantification standard and the analytical sample proved valuable in elucidating the differences among methods, considering equipment, resolution specification, and ionization.

Freshwater environment risk assessment and derivation of human health ambient water quality criteria for SCCPs in China

Short-chain chlorinated paraffins (SCCPs, CxH2x+2-yCly, where x = 10 to 13 and y = 3 to x) are a complex family of emerging contaminants that have been identified as persistent, bioaccumulative and toxic (PBT) substances. Because of their persistence, high toxicity, bioaccumulation and long-distance mobility, SCCPs were added to the list of controlled POPs in the Stockholm Convention in 2017. China is the largest producer and user of SCCPs all over the world, thus SCCPs have been widely distributed in the freshwater environment. But the ecological risk and human health risk of SCCPs in China were still less evaluated. This study collected and screened the exposure data of SCCPs in freshwater environment in China, and then evaluated the freshwater and sediments ecological risk of SCCPs by risk quotient (RQ) method and the human health risk by margin of exposure (MOE) method. Our results showed that the pollution of SCCPs in the freshwater environment in China was not optimistic. The ecological risks and human health risks had occurred, and even there were high ecological risks occurred in some regions in China. Besides, because of the absence of the concentration threshold of SCCPs to protect human health in freshwater at present, we derived the human health ambient water quality criteria (AWQC) values of SCCPs based on exposure data and bioaccumulation factor (BAF) in China. The human health AWQC values of SCCPs ranged from 14.99 ng L-1 to 154.54 ng L-1 in different regions in China, and the national human health AWQC value was determined as 24.08 ng L-1. This study will provide the scientific references for the management and control of SCCPs in China, especially for the formulation of standard of water environmental quality for SCCPs.

Distribution, sources, and ecological risk assessment of polychlorinated biphenyls (PCBs) in the estuary of Dagu River, China

Four different types of 0-30 cm soil/sediment samples were collected from aquaculture land, farmland, industrial land and river bottom sediment in the estuary area of Dagu River, and the pollution status and sources of 7 PCB congeners were analyzed. The results showed that the mean values of Σ7PCBs in soil/sediments of different land use types were 5.01 ng g-1 dw for industrial land, 3.6 ng g-1 dw for estuarine sediments, 2.09 ng g-1 dw for farmland soil and 1.78 ng g-1 dw for farming land. All samples were at low pollution levels and pose little ecological risks. PCBs in the samples are mainly comprised of highly chlorinated biphenyls, and their content decreases gradually with increasing sampling depth. Based on the principal component analysis, it is concluded that the main source of PCBs in the study area is shipping activities, in addition to atmospheric transport and sedimentation sources.

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.

Toxic effects and toxicological mechanisms of chlorinated paraffins: A review for insight into species sensitivity and toxicity difference

Chlorinated paraffins (CPs), a group of chlorinated alkane mixtures, are frequently detected in various environmental matrices and human bodies. Recently, CPs have garnered considerable attention owing to their potential to induce health hazards in wildlife and human. Several reviews have discussed short-chain CPs (SCCPs) induced ecological risk; however, a comprehensive understanding of the underlying toxic mechanisms and a comparison among SCCPs, medium-, and long-chain CPs (MCCPs and LCCPs, respectively) are yet to be established. This review summarizes the latest research progress on the toxic effects and the underlying molecular mechanisms of CPs. The main toxicity mechanisms of CPs include activation of several receptors, oxidative stress, disturbance of energy metabolism, and inhibition of gap junction-mediated communication. The sensitivity of different species to CP-mediated toxicities varies markedly, with aquatic organisms exhibiting the highest sensitivity to CP-induced toxicity. The toxicity comparison analysis indicated that MCCPs may be unsafe as potential substitutes for SCCPs.

Chlorinated paraffins and dechloranes in free-range chicken eggs and soil around waste disposal sites in Tanzania

Electronic waste is a source of both legacy and emerging flame retardants to the environment, especially in regions where sufficient waste handling systems are lacking. In the present study, we quantified the occurrence of short- and medium chain chlorinated paraffins (SCCPs and MCCPs) and dechloranes in household chicken (Gallus domesticus) eggs and soil collected near waste disposal sites on Zanzibar and the Tanzanian mainland. Sampling locations included an e-waste facility and the active dumpsite of Dar es Salaam, a historical dumpsite in Dar es Salaam, and an informal dumpsite on Zanzibar. We compared concentrations and contaminant profiles between soil and eggs, as free-range chickens ingest a considerable amount of soil during foraging, with potential for maternal transfer to the eggs. We found no correlation between soil and egg concentrations or patterns of dechloranes or CPs. CPs with shorter chain lengths and higher chlorination degree were associated with soil, while longer chain lengths and lower chlorination degree were associated with eggs. MCCPs dominated the CP profile in eggs, with median concentrations ranging from 500 to 900 ng/g lipid weight (lw) among locations. SCCP concentrations in eggs ranged from below the detection limit (LOD) to 370 ng/g lw. Dechlorane Plus was the dominating dechlorane compound in all egg samples, with median concentrations ranging from 0.5 to 2.8 ng/g lw. SCCPs dominated in the soil samples (400-21300 ng/g soil organic matter, SOM), except at the official dumpsite where MCCPs were highest (65000 ng/g SOM). Concentrations of dechloranes in soil ranged from below LOD to 240 ng/g SOM, and the dominating compounds were Dechlorane Plus and Dechlorane 603. Risk assessment of CP levels gave margins of exposure (MOE) close to or below 1000 for SCCPs at one location.

Comparison between pollutants found in breast milk and infant formula in the last decade: A review

Since ancient times, breastfeeding has been the fundamental way of nurturing the newborn. The benefits of breast milk are widely known, as it is a source of essential nutrients and provides immunological protection, as well as developmental benefits, among others. However, when breastfeeding is not possible, infant formula is the most appropriate alternative. Its composition meets the nutritional requirements of the infant, and its quality is subject to strict control by the authorities. Nonetheless, the presence of different pollutants has been detected in both matrices. Thus, the aim of the present review is to make a comparison between the findings in both breast milk and infant formula in terms of contaminants in the last decade, in order to choose the most convenient option depending on the environmental conditions. For that, the emerging pollutants including metals, chemical compounds derived from heat treatment, pharmaceutical drugs, mycotoxins, pesticides, packaging materials, and other contaminants were described. While in breast milk the most concerning contaminants found were metals and pesticides, in infant formula pollutants such as metals, mycotoxins, and packaging materials were the most outstanding. In conclusion, the convenience of using a feeding diet based on breast milk or either infant formula depends on the maternal environmental circumstances. However, it is important to take into account the immunological benefits of the breast milk compared to the infant formula, and the possibility of using breast milk in combination with infant formula when the nutritional requirements are not fulfilled only with the intake of breast milk. Therefore, more attention should be paid in terms of analyzing these conditions in each case to be able to make a proper decision, as it will vary depending on the maternal and newborn environment.

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.

Assessment of silicone wristbands for monitoring personal exposure to chlorinated paraffins (C8-36): A pilot study

Chlorinated paraffins (CPs) are a major environmental concern due to their ubiquitous presence in the environment. Since human exposure to CPs can significantly differ among individuals, it is essential to have an effective tool for monitoring personal exposure to CPs. In this pilot study, silicone wristbands (SWBs) were employed as a personal passive sampler to measure time-weighted average exposure to CPs. Twelve participants were asked to wear a pre-cleaned wristband for a week during the summer of 2022, and three field samplers (FSs) in different micro-environments were also deployed. The samples were then analyzed for CP homologs by LC-Q-TOFMS. In worn SWBs, the median concentrations of quantifiable CP classes were 19 ng/g wb, 110 ng/g wb, and 13 ng/g wb for ∑SCCPs, ∑MCCPs, and ∑LCCPs (C_18-20), respectively. For the first time, lipid content is reported in worn SWBs, which could be a potential impact factor in the kinetics of the accumulation process for CPs. Results showed that micro-environments were key contributors to dermal exposure to CPs, while a few outliers suggested other sources of exposure. CP exposure via dermal contact showed an increased contribution and thus poses a nonnegligible potential risk to humans in daily life. Results presented here provide proof of concept of the use of SWBs as a cheap and non-invasive personal sampler in exposure studies.

Occurrence of some legacy and emerging contaminants in feed and food and their ranking priorities for human exposure

The "feed-to-food" pathway is one of the most important routes for human exposure to manmade contaminants. The contaminants could threaten human health through the "feed-to-food" route and have recently become of great public concern. This review selects the representative legacy and emerging contaminants (ECs), such as polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), organophosphate esters (OPEs), short-chain chlorinated paraffins (SCCPs), and per- and polyfluoroalkyl substances (PFASs), regarding their occurrence in feed and food, as well as their metabolites and transport in farming and livestock ecosystems. Factors that might influence their presence and behavior are discussed. This review raises an approach to rank the priority of ECs using the EC concentrations in feed and food and using the hazard quotient (HQ) method for human health. Although SCCPs have the highest levels in feed and food, their potential risks appear to be the lowest. PFASs have the highest HQs on account of human exposure risk. Future research should pay more attention to the combined effects of multiple ECs.

Release Mechanism of Short- and Medium-Chain Chlorinated Paraffins from PVC Materials under Thermal Treatment

Chlorinated paraffins (CPs) as plasticizers are massively added to polyvinyl chloride (PVC) products, during whose life cycle CPs can be continuously released especially under thermal stress. In this study, a PVC cable sheath was adopted as a representative kind of PVC material to investigate the release behaviors of short- and medium-chain CPs (SCCPs and MCCPs) under thermal treatment. Release percentages of CPs with increasing temperature followed a Gaussian-like curve. At the unmolten stage of 80 °C, heating for 10 min caused 0.051% of added SCCPs and 0.029% of added MCCPs to be released. At the molten stage of 270 °C, accumulative release rates of SCCPs and MCCPs within 10 min were up to 30 and 14%, respectively. The developed emission model indicated that material-gas partitioning and internal diffusion simultaneously governed the release of CPs. During thermal treatment, the release of CPs could be remarkably affected by the thermal expansion of the PVC material and the formation of breakage and micropores. Congener group profiles of released CPs indicated a slight fractionation effect for SCCPs during the release process. Furthermore, the release risk of CPs from the whole life cycle of PVC products was preliminarily evaluated.

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.

A fast gas chromatography coupled with electron capture negative ion mass spectrometry in selected ion monitoring mode screening method for short-chain and medium-chain chlorinated paraffins

RATIONALE

Chlorinated paraffins (CPs) are a group of anthropogenic pollutants that consist of complex mixtures of polychlorinated n-alkanes of different chain lengths (~C₁₀ to C₃₀ ). Persistence, bioaccumulation, toxicity, and long-range transport of short-chain chlorinated paraffins (SCCPs, C₁₀ - to C₁₃ -CPs) have prompted their classification as persistent organic pollutants (POPs) by the Stockholm Convention in 2017. Due to the varying chain lengths and chlorination degrees, quantification of SCCPs and medium-chain chlorinated paraffins (MCCPs, C₁₄ - to C₁₇ ) using gas chromatography coupled with electron capture negative ion mass spectrometry in selected ion monitoring mode (GC/ECNI-MS-SIM) is not only challenging but also very time consuming. In particular, up to eight GC runs per sample are required for the comprehensive GC/ECNI-MS-SIM quantification of SCCPs and MCCPs. These efforts are high especially if the samples do not contain CPs above the limit of detection (LOD), subsequently.

METHODS

We developed a semi-quantitative and sensitive method for the examination of SCCPs and MCCPs in one GC run. This GC/ECNI-MS-SIM screening method was based on the recording of Cl^- (m/z 35 and 37), Cl₂ ^- (m/z 70 and 72), and HCl₂ ^- (m/z 71 and 73) isotope ions and evaluation of the ratios between them.

RESULTS

Correctness of the results of the screening method was verified by analysis of edible oils with and without CPs, CP standards, as well as a technical CP mixture. Polychlorinated biphenyls (PCBs) and other polyhalogenated aromatic compounds, as well as brominated flame retardants, do not form all of the fragment ions analyzed by the screening method.

CONCLUSIONS

After the screening, only CP-positive samples may need to be measured in detail. Measurement time will already be gained in the case of ~10% samples without CPs.

Characterization of chlorinated paraffin-degrading bacteria from marine estuarine sediments

This study explored chlorinated paraffin (CP)-degrading bacteria from the marine environment. Aequorivita, Denitromonas, Parvibaculum, Pseudomonas and Ignavibacterium were selected as the dominant genera after enrichment with chlorinated paraffin 52 (CP52) as the sole carbon source. Eight strains were identified as CP degraders, including Pseudomonas sp. NG6 and NF2, Erythrobacter sp. NG3, Castellaniella sp. NF6, Kordiimonas sp. NE3, Zunongwangia sp. NF12, Zunongwangia sp. NH1 and Chryseoglobus sp. NF13, and their degradation efficiencies ranged from 6.4% to 19.0%. In addition to Pseudomonas, the other six genera of bacteria were first reported to have the degradation ability of CPs. Bacterial categories, carbon-chain lengths and chlorination degrees were three crucial factors affecting the degradation efficiencies of CPs, with their influential ability of chlorinated degrees > bacterial categories > carbon-chain lengths. CP degradation can be performed by producing chlorinated alcohols, chlorinated olefins, dechlorinated alcohols and lower chlorinated CPs. This study will provide valuable information on CP biotransformation and targeted bacterial resources for studying the transformation processes of specific CPs in marine environments.

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.

Levels of Short- and Medium-Chain Chlorinated Paraffins in Edible Insects and Implications for Human Exposure

This study reports on the occurrence and distribution of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs, respectively) in edible insects purchased from Asia and Europe. A total of 36 edible insect samples (n = 24 from Asia, n = 12 from Europe) authorized and prepared for human consumption were purchased and analyzed for SCCPs and MCCPs via gas chromatography and mass spectrometry. SCCPs were detected in 83% of all edible insect samples with an overall median ∑SCCP concentration of 8.7 ng/g dry weight (dw) and a range of <2.0 to 410 ng/g dw, while MCCPs were present in 92% of samples with a median ∑MCCP concentration of 51 ng/g dw and a range of <6.0 to 380 ng/g dw. Median ∑SCCP and ∑MCCP levels in edible insects purchased in Asia were approximately two- and four-times higher, respectively, than those from Europe, while the difference was statistically significant for ∑MCCPs (p < 0.001). Differences in homologue patterns were also observed between Asian and European samples to suggest diverse sources of CP contamination to insects which may include environmental accumulation, industrial processing equipment and food additives. Estimated daily intake of SCCPs and MCCPs via consumption of edible insects suggested that adverse health outcomes were very unlikely, but that continued monitoring of insect farming and processing practices are warranted.

Semiquantitative Characterization of Bromo-chloro Paraffins and Olefins in the Australian Environment

A semiquantitative high-resolution mass spectrometry method was developed and applied to assess the occurrence of bromo-/chloro paraffins (BCPs) and olefins (BCOs) in the environment. More than 400 possible BCPs and BCO congener groups were detected in dust, air, and sewage sludge samples collected from Australia. Median chain analytes with the number of halogen atoms <7 (C_nH_mCl_xBr_y, 14 ≤ n ≤ 17, x + y < 7) prevailed in the dust and sludge samples, while short chain analytes (C_nH_mCl_xBr_y, 10 ≤ n ≤ 13, x + y < 7) predominated the air samples. The estimated concentrations of ∑BCPs and ∑BCOs in dust and sludge were approximately 20% that of the chlorinated paraffins (CPs) present, with the median concentrations of 5.4 μg/g (dust) and 0.18 μg/g (sludge) for ∑BCPs and 22 μg/g (in dust) and 0.50 μg/g (sludge) for BCOs. In the air samples, the concentrations of BCPs (0.020 pg/m³) and BCOs (0.032 pg/m³) were 3-4 orders of magnitudes lower than the concentrations of CPs (790 pg/m³). Significant correlations (P < 0.001) were found between the concentration of CPs, BCPs, and BCOs in all the matrices.

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.

Assessing Safety of Market-Sold Fresh Fish: Tracking Fish Origins and Toxic Chemical Origins

Increasing global and domestic food trade and required logistics create uncertainties in food safety inspection due to uncertainties in food origins and extensive trade activities. Modern blockchain techniques have been developed to inform consumers of food origins but do not provide food safety information in many cases. A novel food safety tracking and modeling framework for quantifying toxic chemical levels in the food and the food origins was developed. By integrating chemicals' multimedia environment exchange, food web, and source tracking systems, the framework was implemented to identify short-chain chlorinated paraffin (SCCP) contamination of fresh hairtail fish sold by a Walmart supermarket in Xi'an, northwestern China, and sourced in Eastern China Sea coastal waters. The framework was shown to successfully predict SCCP level with a mean of 17.8 ng g^-1 in Walmart-sold hairtails, which was comparable to lab-analyzed 21.9 ng g^-1 in Walmart-sold hairtails. The framework provides an alternative and cost-effective approach for safe food inspection compared to traditional food safety inspection techniques. These encouraging results suggest that the approach and rationale reported here could add additional information to the food origin tracking system to enhance transparency and consumers' confidence in the traded food they consumed.

A reference material (NMIJ RM 4076-a) for the determination of short-chain chlorinated paraffins

Chlorinated paraffins are primary industrial chemical products used for metalworking fluids and flame retardants. However, short-chain chlorinated paraffins (SCCPs) are registered in Annex A of the Stockholm Convention on Persistent Organic Pollutants. Therefore, since an accurate quantitative determination of SCCPs is crucial to monitor the level of pollution, analysis quality assurance with reference materials is needed. In this study, a reference material (RM), NMIJ RM 4076-a, was developed by the National Metrology Institute of Japan at the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) for the quantification of SCCPs. We determined the mass fraction of SCCPs by subtracting the impurities quantified using the mass-balance method, a combination of gas chromatography-flame ionization detection, Karl Fischer titrations, headspace-gas chromatography-mass spectrometry, and thermal gravimetric analysis. The mass fraction value of NMIJ RM 4076-a was concluded to be 0.9996 kg/kg. The standard uncertainty of this mass fraction was evaluated on the basis of the mass-balance method, the sample homogeneity, and stability obtained using the above analytical techniques. Accordingly, the expanded uncertainty estimated using a coverage factor of k = 2 was found to be 0.0013 kg/kg. The mass fraction of chlorine and the homologue compositional ratios are also given for this RM as supplementary technical information. This RM is expected to be applicable for use in the calibration of instruments, or for checking the validity of analytical methods or instruments for estimating the comparability of SCCP analyses.

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

Short chain chlorinated paraffins (SCCPs) have attracted increasing attention due to their potential risks to the ecosystem and human health. However, there is still a lack of systematic research on their environmental fate in the coastal marine environment. In this study, we collected paired seawater (n = 40) and surface sediment samples (n = 40) from East China Sea, and investigated their spatial distribution, partitioning behaviors and ecological risks. The total SCCP concentrations (∑SCCPs) in seawater and sediment samples were in the range of 12.2-430 ng/L and 89.6-351 ng/g (dry weight), respectively. C_10-11 SCCPs and Cl_5-7 SCCPs were the predominant homologues in all of the samples. This study first calculated the field-based logK_OC values for ∑SCCPs in the marine environment, which ranged from 5.0 to 6.5 (mean 5.5). The logK_OC values of SCCP homologues (range 3.6-8.0, mean 5.6) showed a weak correlation with their logK_OW (R = 0.214, p < 0.05). A preliminary risk assessment indicated that SCCPs at current levels posed no significant ecological risk. Overall, this study contributes to the further understanding of environmental behaviors of SCCPs in the marine environment.

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

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

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.

Environmental contamination and human exposure of polychlorinated biphenyls (PCBs) in China: A review

Polychlorinated biphenyls (PCBs), together with 11 other organic compounds, were initially listed as persistent organic pollutants (POPs) by the Stockholm Convention because of their potential threat to ecosystems and humans. In China, many monitoring studies have been undertaken to reveal the level of PCBs in environment since 2005 due to the introduced stricter environmental regulations. However, there are still significant gaps in understanding the overall spatial and temporal distributions of PCBs in China. This review systematically discusses the occurrence and distribution of PCBs in environmental matrices, organisms, and humans in China. Results showed that PCB contamination in northern and southern China was not significantly different, but the PCB levels in East China were commonly higher than those in West China, which might have been due to the widespread consumption of PCBs and intensive human activities in East China. Serious PCB contamination was found in e-waste disassembling areas (e.g., Taizhou of Zhejiang Province and Qingyuan and Guiyu of Guangdong Province). Higher PCB concentrations were also chronicled in megalopolises and industrial clusters. The unintentionally produced PCBs (UP-PCBs) formed during industrial thermal processes may play an increasingly significant role in PCB pollution in China. Low PCB levels were recorded in rural and underdeveloped districts, particularly in remote and high-altitude localities such as the Tibetan Plateau and the South China Sea. However, these data are limited. Human exposure to PCBs is closely related to the characteristics of environmental pollution. This review also discusses existing issues and future research prospects on PCBs in China. For instance, the accumulation characteristics and migration regularities of PCBs in food webs should be further studied. More investigations should be undertaken to assess the quantitative relationship between external and internal exposure to PCBs. For example, bioaccessibility and bioavailability studies should be supplemented to evaluate human health risks more accurately.

Inventory approach for short-chain chlorinated paraffins for the Stockholm Convention implementation in Brazil

Chlorinated paraffins (CPs) are chemicals with multipurpose applications. Their global production has increased despite their adverse impacts on the environment and human health. In 2017, short-chain chlorinated paraffins (SCCPs) were listed as persistent organic pollutants (POPs) in the Stockholm Convention. Yet, specific exemptions were granted for their applications despite the recycling prohibition for products containing SCCPs. Therefore, we aimed to produce the first Brazilian inventory of SCCPs following its respective guidance to evaluate the applicability of the SCCP inventory guidance and to provide technical insights regarding SCCPs in the update of the Brazilian National Implementation Plan (NIP). Moreover, we performed a review of SCCP occurrence in Brazil to fulfil data gaps in the inventory development. We identified and consulted nationwide stakeholders and assessed foreign trade data of CPs and products that might contain CPs in relevant amounts. The Brazilian production of CPs was discontinued in 1994. However, CPs are still imported and used in the country. CPs have been mostly applied as plasticizers, flame retardants and lubricants in Brazil. The import of products containing CPs also pose a significant route of CP entrance into Brazil. Thus, the current end-of-life management of CP-containing products is a bottleneck towards the Convention implementation. The guidance application was feasible and useful despite the low engagement of stakeholders. To assess foreign trade of CPs and CP-containing products, we recommend the use of more specific tracking codes. Besides, the review of SCCP occurrence is not a demanded part for an inventory but was a useful complementation.

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.

Groundwater contaminated with short-chain chlorinated paraffins and microbial responses

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

Differential Accumulation of Short-, Medium-, and Long-Chain Chlorinated Paraffin in Free-Range Laying Hens from an E-Waste Recycling Area

Chlorinated paraffins (CPs) are environmental pollutants of emerging concern. Long-chain CPs (LCCPs) are considered of lesser concern than other CPs in food due to their lower accumulation in most organisms. However, LCCPs have been shown to accumulate preferentially in birds. We used ultrahigh-performance liquid chromatography combined with electrospray ionization Orbitrap mass spectrometry (UPLC-ESI-Orbitrap MS) to analyze CPs (C_10-26Cl_4-12) in tissues of free-range hens, their feed, and local soils. Feed was found to be the main source of CP intake. The CP carbon chain length had little impact on their absorption. C₁₈-CPs were excreted in preference to C₁₃-CPs by laying. The metabolic elimination rates of CPs (0.2 μg/mL) estimated using chicken liver microsomes were in the order C₁₂Cl₆ (91%) > C₁₂Cl₈ (57%) > C₁₈Cl₆ (12%) > C₁₈Cl₈ (6%). CPs with longer carbon chains accumulated preferentially in muscle and adipose tissues, and the accumulation of specific carbon chain lengths was related to the content and composition of different CPs in the intake source.

Cross-Model Comparison of Transcriptomic Dose-Response of Short-Chain Chlorinated Paraffins

Short-chain chlorinated paraffins (SCCPs) have attracted attention because of their toxicological potential in humans and wildlife at environmentally relevant doses. However, limited information is available regarding mechanistic differences across species in terms of the biological pathways that are impacted by SCCP exposure. Here, a concentration-dependent reduced human transcriptome (RHT) approach was conducted to evaluate 15 SCCPs in HepG2 cells and compared with our previous results using a reduced zebrafish transcriptome (RZT) approach in zebrafish embryos (ZFEs). Generally, SCCPs induced a broader suite of biological pathways in ZFEs than HepG2 cells, and all of the 15 SCCPs were more potent in HepG2 cells compared to ZFEs. Despite these general differences, the transcriptional potency of SCCPs in both model systems showed a significant linear relationship (p = 0.0017, r² = 0.57), and the average ratios of transcriptional potency for each SCCP in RZT to that in RHT were ∼100,000. C₁₀H₁₄Cl₈ was the most potent SCCP, while C₁₀H₁₇Cl₅ was the least potent in both ZFEs and HepG2 cells. An adverse outcome pathway network-based analysis demonstrated model-specific responses, such as xenobiotic metabolism that may be mediated by different nuclear receptor-mediated pathways between HepG2 cells (e.g., CAR and AhR activation) and ZFEs (e.g., PXR activation). Moreover, induced transcriptional changes in ZFEs associated with pathways and molecular initiating events (e.g., activation of nicotinic acetylcholine receptor) suggest that SCCPs may disrupt neural development processes. The cross-model comparison of concentration-dependent transcriptomics represents a promising approach to assess and prioritize SCCPs.

Resolving mass fractions and congener group patterns of C8-C17 chlorinated paraffins in commercial products: Associations with source characterization

Commercial chlorinated paraffins (CPs) are a source of CPs in the environment, and clarification of the different CP groups present in commercial products is important for source characterization. Resolving CP congener groups is hindered by the complex CP compositions of commercial products. We used comprehensive two-dimensional gas chromatography coupled with electron capture negative ionization high-resolution time-of-flight mass spectrometry to profile 57 C₈ - C₁₇ CP congener groups in 18 CP-42, CP-52, and CP-70 commercial products. Very short-chain CPs (vSCCPs), including C₈Cl_5-8 and C₉Cl_5-9 CPs, and other chlorinated aromatic compounds were identified in the commercial products. The mass fractions of total vSCCPs, short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) in the commercial products ranged from 0.02% to 3.61%, 0.75% to 51.4%, and 0.39% to 69.1%, respectively. Two-dimensional hierarchical cluster analysis with a heat map plot highlighted variations in the C₈ - C₁₇ CP congener group patterns among different commercial CP formulations. The principal component analysis results indicated that commercial CPs products might be important contributors to vSCCPs, SCCPs, and MCCPs in various environmental matrices. This study provides comprehensive and well-resolved compositional data for CPs in commercial products, which will be helpful for CP source characterization.

Insights into the Occurrence, Fate, and Impacts of Halogenated Flame Retardants in Municipal Wastewater Treatment Plants

Halogenated flame retardants (HFRs) have been extensively used in various consumer products and many are classified as persistent organic pollutants due to their resistance to degradation, bioaccumulation potential and toxicity. HFRs have been widely detected in the municipal wastewater and wastewater treatment solids in wastewater treatment plants (WWTPs), the discharge and agricultural application of which represent a primary source of environmental HFRs contamination. This review seeks to provide a current overview on the occurrence, fate, and impacts of HFRs in WWTPs around the globe. We first summarize studies recording the occurrence of representative HFRs in wastewater and wastewater treatment solids, revealing temporal and geographical trends in HFRs distribution. Then, the efficiency and mechanism of HFRs removal by biosorption, which is known to be the primary process for HFRs removal from wastewater, during biological wastewater treatment processes, are discussed. Transformation of HFRs via abiotic and biotic processes in laboratory tests and full-scale WWTPs is reviewed with particular emphasis on the transformation pathways and functional microorganisms responsible for HFRs biotransformation. Finally, the potential impacts of HFRs on reactor performance (i.e., nitrogen removal and methanogenesis) and microbiome in bioreactors are discussed. This review aims to advance our understanding of the fate and impacts of HFRs in WWTPs and shed light on important questions warranting further investigation.

In vitro biotransformation and evaluation of potential transformation products of chlorinated paraffins by high resolution accurate mass spectrometry

Chlorinated paraffins (CPs) are high production chemicals, which leads to their ubiquitous presence in the environment. To date, few studies have measured CPs in humans and typically at relatively low concentrations, despite indications that exposure may be high compared to various persistent organic pollutants. The aim of this study is to investigate the in vitro biotransformation of CPs by human liver fractions. We determined the changes of the CP concentrations after the enzymatic transformation with human liver microsomes using a two-tiered in vitro approach. CP concentrations decreased with human liver microsomes, with the decreases of 33-94% after incubating with different groups of enzymes for 2 h. The profiles of CP rapidly shifted after the incubation with human liver microsomes. In addition, the concentrations of CPs and the biotransformation products were tentatively measured using high-resolution mass spectrometric analysis, including very short CP (carbon chain length <10), alcohols, ketones, and carboxylic acids. C‒C bond cleavage is a potential transformation pathway for CPs, and ketones are potential products of CP biotransformation, especially for long-chain CPs (C_>17). The ketone products may be investigated as CP exposure biomarker in biomonitoring studies.

Short- and medium-chain chlorinated paraffin exposure in South Germany: A total diet, meal and market basket study

Short- and medium-chain chlorinated paraffins (SCCPs, MCCPs) are high-production volume industrial chemicals that have been previously reported to occur in food, packaging material and the environment. This study presents an assessment of dietary exposure for consumers in Southern Germany based on three different sampling approaches: (i) a classical market basket study (n = 154), (ii) the analysis of ready-made meals from restaurants (n = 10), and (iii) a total diet approach (n = 21). In 35% of the samples, CPs were below the method limit of quantification. Highest amounts of SCCPs and MCCPs were found especially in extra virgin olive oils (EVOOs) and fish. Homologue patterns indicated the partial removal of CPs during the refining of (other) edible oils. Ready-made meals contained only low amounts of CPs equal to estimations based on market basket samples. Total diet samples from the same hospital were generally comparable with each other regardless of diet, although vegetarian meal plans with high amounts of cheese and other dairy products contained up to an order of magnitude more CPs than other diets. Taking all approaches into account, calculated daily exposures for adults ranged 35-420 ng/kg bw/day for ΣSCCPs and 22-840 ng/kg bw/day for ΣMCCPs, which is between one and two orders of magnitude higher than the current dietary intake of polychlorinated biphenyls (indicator PCBs) in Europe.

Transformation pathways of chlorinated paraffins relevant for remediation: a mini-review

In the past decades, the environmental presence and ecological risks of chlorinated paraffins (CPs), an emerging class of organic halogen compounds, have been receiving increasing attention worldwide. Short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) constitute the important CPs of considerable concern. In this review article, the state-of-the-art research status on the environmental transformation of CPs, including thermal decomposition, photolytic and photocatalytic degradation, biological metabolism, and atmospheric transformation, was summarized and integrated in detail. The degradation efficiency and transformation products of CPs in these environmental processes were evaluated, in which dechlorination was considered as the major reaction pathway. Notably, waste incineration of CPs has been demonstrated to generate a variety of persistent chlorinated aromatic hydrocarbons such as polychlorinated biphenyls and polychlorinated naphthalenes, which have more significant environmental impacts. Additionally, photodegradation and photocatalysis are suggested as the feasible techniques for efficient removal of SCCPs from water matrices. Overall, the current transformation studies of CPs could facilitate the comprehensive understanding of their environmental behaviors and fate as well as the development of promising remediation strategies for pollution control.