Metabolomic mechanisms of short chain chlorinated paraffins toxicity in rats

Exposure to short-chain chlorinated paraffins induces mortality in marine medaka larvae through neurotoxicity and oxidative stress

Despite the strict regulation of short-chain chlorinated paraffins (SCCPs), they continue to be detected in marine environments and organisms worldwide. However, their toxicity to marine fish has been scarcely studied. In this study, the effect of different concentrations of SCCPs (0-1000 μg L⁻1) on the early life stages of the marine medaka Oryzias melastigma was evaluated. The impacts of SCCPs on the embryonic stage of O. melastigma were considered negligible, while significant growth retardation was observed during the larval stages after 13 days of exposure, with the median lethal concentration (LC50) determined as 227 μg L⁻1. Exposure to SCCPs for 4 days resulted in melanosome dispersion, immobilization, disruption of feeding activity, and an increase in acetylcholinesterase activity, suggesting that SCCPs induce neurotoxicity in the cholinergic system, leading to mortality through starvation. Dose-dependent DNA damage, fluctuations in mitochondrial respiration, and increases in intracellular reactive oxygen species content and apoptosis were observed after 4 days of exposure, indicating strong induction of oxidative stress. In addition, potential endocrine disruption was observed, as SCCPs significantly decreased cortisol content and modulated the mRNA expressions of genes involved in the hypothalamic-pituitary-interrenal axis. Taken together, exposure to SCCPs resulted in mortality and growth retardation, primarily through neurotoxicity and oxidative stress in marine medaka larvae.

Investigating the research landscape of chlorinated paraffins over the past ten decades

Chlorinated paraffins (CPs) are classified as emerging persistent organic pollutants (POPs). Due to their associated environmental and health impacts, these groups of chemicals have been a subject of interest among researchers in the past decades. Here we used a scientometric approach to understand the research landscape of CPs using literature published in the Web of Science and Scopus database. RStudio and VOSviewer programs were employed as scientometric tools to analyze the publication trends in global CP-related research from 1916 to 2024. A total of 1,452 articles were published over this period, with a publication/author and co-author/publication ratio of 0.43 and 5.49, respectively. China ranked first in publication output (n = 556, 43.3%), and the highest total citations (n = 12,007), followed by Sweden (n = 90), Canada (n = 77), and Germany (n = 75). Publications from developing countries were limited, with most contributions from Africa originating from Egypt (n = 7), South Africa (n = 5), and Nigeria (n = 3), primarily through international collaborations. The average annual growth rate of 4.3% suggests a significant future article output. This scientometric analysis allowed us to infer global trends in CPs, identify tendencies and gaps, and contribute to future research. Despite having similar toxicity to short-chain chlorinated paraffin (SCCP), long-chain chlorinated paraffin (LCCP) has received less attention. Therefore, future research should prioritize studying LCCP bioaccumulation and toxicity in diverse food webs, focusing on aquatic species vulnerable to CPs and effective toxicological models. Additionally, collaborative research with developing countries should be encouraged to enhance meeting the Stockholm Convention's demand.

Short-chain chlorinated paraffins induce liver injury in mice through mitochondrial disorders and disruption of cholesterol-bile acid pathway

Short-chain chlorinated paraffins (SCCPs) are pervasive organic pollutants recognized for their persistence and bio-toxicity. This study investigated the hepatotoxic mechanisms of SCCPs at environmentally relevant concentration (0.7 μg/kg). The results showed that SCCPs exposure in mice resulted in dysregulated blood and liver lipids, marked by elevated cholesterol levels. Additionally, liver function was compromised, as indicated by increased levels of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase. Histopathological examination of liver tissue post-SCCPs exposure revealed hepatocyte enlargement, vacuolar degeneration, and mild ballooning degeneration. Mechanistically, SCCPs induced mitochondrial abnormalities, evidenced by heightened Hoechst 33258 fluorescence, and augmented reactive oxygen species and malondialdehyde levels in liver tissue. This was accompanied by a reduction in total antioxidant capacity, culminating in elevated apoptosis markers, including cytochrome C and caspase-3. Moreover, SCCPs perturbed hepatocellular energy metabolism, characterized by increased glycolysis, lactic acid, and fatty acid oxidation, alongside a disruption in the tricarboxylic acid cycle and a decline in mitochondrial energy metabolic function. Furthermore, SCCPs exposure downregulated the expression of genes involved in bile acid synthesis (cyp27a1, fxr, and shp), thereby precipitating the cholesterol-bile acid metabolism disorders and cholesterol accumulation. Collectively, these findings underscore that SCCPs, even at environmentally relevant levels, can induce lipid dysregulation, mitochondrial disorders and cholesterol deposition in the hepatocytes, contributing to liver damage. The study's insights contribute to a comprehension of SCCPs-induced hepatotoxicity and may inform potential preventative and treatment targets for hepatic damage associated with SCCPs exposure.

Short Chain Chlorinated Paraffins Impaired Spermatogenesis Process in Mice via Inhibiting α-KG/TET Enzyme Activity

Short chain chlorinated paraffins (SCCPs) are widely found in various environmental media and potentially threaten human health. However, the toxicity mechanisms of SCCPs to the male reproductive system remain unclear. In this study, male BALB/c mice and GC-1 cells were used to investigate the reproductive toxicity of SCCPs and their molecular mechanisms. SCCPs decreased the content of the tricarboxylic acid cycle intermediate α-KG in testicular cells, thus inhibiting the activity of the DNA demethylase TET enzyme and resulting in an increase in the overall methylation level of the testicular genome. Correspondingly, the promoter demethylation and expression of spermatogenesis-related genes Rbm46, Sohlh1, Kit, and Dmrt1 were significantly reduced by SCCPs, which further prevented the transformation of spermatogonia to spermatocytes and reduced sperm quality in mice. The in vitro experiments suggested that the TGFβ pathway activated by oxidative stress might be an essential reason for inhibiting the tricarboxylic acid cycle and the reduction of α-KG content in testicular cells induced by SCCPs. Overall, this study reveals a novel metabolic regulatory mechanism of SCCPs-induced spermatogenesis disorders, which provides an essential theoretical basis for the prevention of reproductive toxicity of SCCPs.

The ototoxicity of chlorinated paraffins via inducing apoptosis, oxidative stress and endoplasmic reticulum stress in cochlea hair cells

Hearing loss is a common chronic sensory deficit that affects millions of people worldwide and has emerged as a significant public health concern. The association between environmental exposure to chemicals and the prevalence of hearing impairment has recently attracted increased attention. Chlorinated paraffins (CPs) are a type of chemical compound that has been widely used and commonly detected in samples of both environmental and human origin. The knowledge of the toxicological effects of CPs, particularly its ototoxicity, remains limited at present. In this study, six commercial CPs were selected and evaluated using cochlea hair HEI-OC1 cells for their cytotoxicity, apoptosis, DNA damage, reactive oxygen species (ROS) accumulation and oxidative response. The cytotoxicity was observed after CPs exposure at high concentrations except for C-40 and was positively related to the chlorine content (Cl-content) in both CCK-8 and trypan blue assays. All 6 CPs induced cells apoptosis through caspase-dependent apoptotic pathway. CPs exposure induced DNA damage and stimulated ROS overproduction. Antioxidant N-acetyl-L-cysteine (NAC) could reverse the cytotoxicity and ROS accumulation caused by CPs exposure. The overexpression of ATF4 and CHOP indicated that endoplasmic reticulum (ER) stress was involved in the CPs induced cytotoxicity. Thus, CPs induced cytotoxicity and apoptosis via ROS accumulation, ER stress and DNA damage and positively related to the Cl-content and our findings indicate that CPs may pose a risk of ototoxicity at environmental relevant exposure levels.

Imidacloprid-induced lung injury in mice: Activation of the PI3K/AKT/NF-κB signaling pathway via TLR4 receptor engagement

Significant impairment of pulmonary function has been demonstrated through long-term exposure to neonicotinoid insecticides, such as imidacloprid (IMI). However, the underlying mechanisms of lung injury induced by IMI remain unclear. In this study, a mouse model of IMI-induced pulmonary injury was established, and the toxicity and lung damage were assessed through mouse body weight, organ index, hematological parameters, and histopathological analysis of lung tissues. Furthermore, metabolomics and transcriptomics techniques were employed to explore the mechanistic aspects. Results from the toxicity assessments indicated that mouse body weight was significantly reduced by IMI, organ index was disturbed, and hematological parameters were disrupted, resulting in pulmonary injury. The mechanistic experimental results indicate that the differences in metabolites and gene expression in mouse lungs could be altered by IMI. Validation of the results through combined analysis of metabolomics and transcriptomics revealed that the mechanism by which IMI induces lung injury in mice might be associated with the activation of the TLR4 receptor, thereby activating the PI3K/AKT/NF-κB signaling pathway to induce inflammation in mouse lungs. This study provided valuable insights into the mechanisms underlying IMI-induced pulmonary damage, potentially contributing to the development of safer pest control strategies. The knowledge gained served as a robust scientific foundation for the prevention and treatment of IMI-related pulmonary injuries.

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.

Metabolic disturbance of short- and medium-chain chlorinated paraffins to zebrafish larva

Chlorinated paraffins (CPs) are widely produced chemicals. Short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) were listed as Persistent Organic Pollutants (POPs) and candidate POPs under the Stockholm Convention, respectively. The present study explored the developmental toxicity and metabolic disruption caused by SCCPs and MCCPs in zebrafish (Danio rerio) larvae. CPs exposure at environmentally relevant levels caused no obvious phenotypic changes with zebrafish larvae except that the body length shortening was observed after exposure to CPs at 1-200 μg/L for 7 day post fertilization. A further metabolomic approach was conducted to explore the early biological responses of developmental toxicity induced by CPs at low dose (1, 5, and 10 μg/L). The results of metabolic disorder, pathway analysis and chronic values indicated that, compared with SCCPs, MCCPs exhibited more risks to zebrafish larvae at low doses. Lipid metabolism was markedly affected in SCCPs exposure group, whereas MCCPs primarily disturbed lipid metabolism, amino acid, and nucleotide metabolisms. Compare with SCCPs, the relatively higher lipid solubility, protein affinity and metabolic rate of MCCPs can probably explain why MCCP-mediated metabolic disruption was significantly higher than that of SCCP. Notably, SCCPs and MCCPs have the same potential to cause cancer, but no evidence indicates the mutagenicity. In summary, our study provides insight into the potential adverse outcome for SCCP and MCCP at low doses.

Short- and medium-chain chlorinated paraffins in breast milk in Shanghai, China: Occurrence, characteristics, and risk assessment

As novel contaminants, short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) have been of great concern in the past several years. Shanghai was one of the provinces with the largest chlorinated paraffins (CPs) emission in China; nevertheless, there is currently little information on the human exposure to SCCPs and MCCPs, particularly MCCPs. In this study, 25 breast milk samples were collected in Shanghai from 2016 to 2017. The concentrations of SCCPs and MCCPs were determined using two-dimensional gas chromatography coupled with orbitrap high-resolution mass spectrometry (GC × GC-orbitrap-HRMS) to investigate their characteristics and assess the associated health risks for breast-fed infants. Compared with the previous studies in other areas, the current study presented the higher CPs concentrations, with median concentrations of SCCPs and MCCPs up to 771 and 125 ng/g lipid weight (lw), respectively. The exposure profiles of the CPs were characterized by C10 and Cl6-7 as the predominant congeners of SCCPs, while C14 and Cl7-9 were identified as the dominant groups of MCCPs. CP-42 and CP-52 were identified as potential sources of CPs found in breast milk samples collected in Shanghai. The concentrations of MCCPs exhibited a positive correlation (p value < 0.05) with the dietary consumption of meat and poultry. No significant positive correlations were observed for SCCPs and MCCPs with polychlorinated dibenzodioxins/furans (PCDD/Fs) congeners. A preliminary exposure assessment showed that SCCPs in breast milk potentially posed high risks to the breast-fed infants in Shanghai.

Detection of Bromochloro Alkanes in Indoor Dust Using a Novel CP-Seeker Data Integration Tool

Bromochloro alkanes (BCAs) have been manufactured for use as flame retardants for decades, and preliminary environmental risk screening suggests they are likely to behave similarly to polychlorinated alkanes (PCAs), subclasses of which are restricted as Stockholm Convention Persistent Organic Pollutants (POPs). BCAs have rarely been studied in the environment, although some evidence suggests they may migrate from treated-consumer materials into indoor dust, resulting in human exposure via inadvertent ingestion. In this study, BCA-C14 mixture standards were synthesized and used to validate an analytical method. This method relies on chloride-enhanced liquid chromatography-electrospray ionization-Orbitrap-high resolution mass spectrometry (LC-ESI-Orbitrap-HRMS) and a novel CP-Seeker integration software package for homologue detection and integration. Dust sample preparation via ultrasonic extraction, acidified silica cleanup, and fractionation on neutral silica cartridges was found to be suitable for BCAs, with absolute recovery of individual homologues averaging 66 to 78% and coefficients of variation ≤10% in replicated spiking experiments (n = 3). In addition, a total of 59 indoor dust samples from six countries, including Australia (n = 10), Belgium (n = 10), Colombia (n = 10), Japan (n = 10), Thailand (n = 10), and the United States of America (n = 9), were analyzed for BCAs. BCAs were detected in seven samples from the U.S.A., with carbon chain lengths of C8, C10, C12, C14, C16, C18, C24 to C28, C30 and C31 observed overall, though not detected in samples from any other countries. Bromine numbers of detected homologues in the indoor dust samples ranged Br1-4 as well as Br7, while chlorine numbers ranged Cl2-11. BCA-C18 was the most frequently detected, observed in each of the U.S.A. samples, while the most prevalent degrees of halogenation were homologues of Br2 and Cl4-5. Broad estimations of BCA concentrations in the dust samples indicated that levels may approach those of other flame retardants in at least some instances. These findings suggest that development of quantification strategies and further investigation of environmental occurrence and health implications are needed.

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.

Biomonitoring, exposure routes and risk assessment of chlorinated paraffins in humans: a mini-review

Chlorinated paraffins (CPs), which were conventionally classified into short- (SCCPs), medium- (MCCPs) and long- (LCCPs) chain CPs, have received growing attention due to their wide usage and extensive detection in environmental samples and biota. The number of studies regarding the biomonitoring of CPs in human beings increased rapidly and their health risk gained great concern. This review summarized their occurrence and homologue patterns in human matrices including blood/serum, placenta, cord serum and breast milk. As the production and usage of SCCPs was progressively banned after being listed in Annex A of the Stockholm Convention, the production of MCCPs and LCCPs was stimulated. Accordingly, the ratio of MCCPs/SCCPs in human samples has increased rapidly in the last 5 years. The current understanding of exposure routes and risk assessments of CPs was also reviewed. Oral dietary intake is the most predominant source of daily CP intake, but dust ingestion, inhalation and dermal exposure is also nonnegligible, especially for MCCPs and LCCPs. Furthermore, the reported upper bound of the estimated daily intakes (EDIs) in various risk assessment studies was close to or exceeded the tolerable daily intakes (TDIs). Considering the bioaccumulation and long-lasting exposure of CPs, their health impacts on humans and the ecosystem required continuous monitoring and evaluation.

An international investigation of chlorinated paraffin concentrations and homologue distributions in indoor dust

In this study, very short-, short-, medium-, and long-chain chlorinated paraffins (vSCCPs, SCCPs, MCCPs and LCCPs, respectively) were measured in 40 indoor dust samples from four countries including Japan (n = 10), Australia (n = 10), Colombia (n = 10) and Thailand (n = 10). Homologues of the chemical formula CxH(2x+2-y)Cly ranging C6-36 and Cl3-30 were analysed using liquid chromatography coupled to Orbitrap high resolution mass spectrometry (LC-Orbitrap-HRMS) and integrated using novel custom-built CP-Seeker software. CPs were detected in all dust samples with MCCPs the dominant homologue group in all countries. Overall median ∑SCCP, ∑MCCP and ∑LCCP (C18-20) concentrations determined in dust samples were 30 μg/g (range; 4.0-290 μg/g), 65 μg/g (range; 6.9-540 μg/g) and 8.6 μg/g (range; <1.0-230 μg/g), respectively. Of the quantified CP classes, overall concentrations were generally highest in the samples from Thailand and Colombia, followed by Australia and Japan. vSCCPs with C≤9 were detected in dust from each country with an overall frequency of 48%, while LCCPs (C21-36) were present in 100% of samples. Estimated daily intakes (EDIs) calculated for SCCPs and MCCPs relating to ingestion of contaminated indoor dust were considered not to represent health risks based on currently available toxicological data using the margin of exposure (MOE) approach. To the authors' knowledge, this study provides the first data on CPs in indoor dust from Japan, Colombia and Thailand, and is among the first reports of vSCCPs in indoor dust, globally. These findings indicate that further toxicological data and the availability of appropriate analytical standards are needed to evaluate the potential for negative health outcomes deriving from exposure to vSCCPs and LCCPs.

Effects of exposure to chlorinated paraffins on human health: A scoping review

Chlorinated paraffins (CPs) belong to an emerging class of persistent organic pollutants (POPs) widely detected in environmental matrices and human samples. The potential health risks of CPs on humans have initiated intense concerns but there have been few studies focusing on the said topic. Addressing the gap, we make a scoping review on the current global body of evidence from epidemiological and toxicological studies. Furthermore, the management strategies and regulations related to CPs are presented and discussed. There were 70 articles among 11,280 records, including four epidemiological studies, one case report, another twenty-nine studies reporting human body burden, and thirty-six toxicological studies, finally included in this review. Additionally, twenty-three management regulation relevant documents/websites were included. CPs exist in human blood, breast milk, placenta, and other tissues. Population-based and laboratory studies suggest that CPs may cause liver and kidney toxicity, developmental toxicity, neurotoxicity, endocrine disorder, immune dysfunction, and reproductive toxicity. CPs with shorter carbon chains and higher chlorine content may be more harmful. In particular, the combined effect of CPs with other pollutants is of great concern. Population-based studies are far from sufficient at present, and most of them are conducted in China or developed countries. Besides, the toxicity assessment studies of CPs are inadequate. In addition, most studies focus on short-chain CPs (SCCPs) while few studies explored the effect of long-chain CPs (LCCPs). Thus, conducting more epidemiological studies in larger populations and toxicological studies combined with new technology methods are of great significance for better understanding the adverse health effects of CPs, which may promote CPs management regulations.

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.

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.

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

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

Seasonal variation of short-, medium- and long-chain chlorinated paraffin distribution in Belgian indoor dust

Chlorinated paraffins (CPs) are high production volume plasticizers and flame retardants, which have exhibited bioaccumulative and toxic properties. CPs may be released from treated consumer goods and bind with indoor dust, leading to human exposure via unintentional dust ingestion. In this study, the concentrations and homologue distribution of CPs were measured in 50 indoor dust samples collected in paired winter and summer sampling campaigns from 25 homes in Flanders, Belgium. Short-, medium- and long-chain CPs (SCCPs (C_10-13), MCCPs (C_14-17) and LCCPs (C_18-20), respectively) were each detected in all Belgian indoor dust samples with overall median concentrations of 6.1 µg/g (range 0.61 to 120 µg/g), 45 µg/g (range 4.5 to 520 µg/g) and 4.5 µg/g (range 0.3 to 50 µg/g), respectively. Concentrations were significantly higher in the winter samples than summer for each of the three groups (p < 0.05). LCCPs homologues ranging from C_21-32 were also detected in dust samples and accounted for approximately half of the LCCP relative abundance based on instrumental peak area, although a lack of appropriate analytical standards prevented quantification of these homologues. While clear sources of CP contamination in dust could not be identified, significant associations between concentrations of ∑SCCPs, ∑MCCPs and ∑LCCPs (C_18-20) (p < 0.05) suggested the combined application within materials or products in homes. Based on typical exposure scenarios, estimated daily intake of ∑CPs (C_10-20) for adults and toddlers were 14 and 270 ng/kg bw/day, respectively, though margin of exposure assessments for SCCPs and MCCPs indicated that adverse health effects were unlikely for all exposure scenarios. This study presents the first evidence of seasonal variation in the levels and distribution for each of the SCCP, MCCP and LCCP classes in indoor dust and highlights the urgent need for appropriate analytical standards for LCCP quantification.

Subcellular-Level Mitochondrial Energy Metabolism Response in the Fat Body of the German Cockroach Fed Abamectin

Mitochondria are the leading organelle for energy metabolism. The toxic effects of environmental toxicants on mitochondrial morphology, energy metabolism, and their determination of cell fate have already been broadly studied. However, minimal research exists on effects of environmental toxicants such as pesticides on mitochondrial energy metabolism at in vitro subcellular level, particularly from an omics perspectives (e.g., metabolomics). Here, German cockroach (Blattella germanica) was fed diets with (0.01 and 0.001 mg/mL) and without abamectin, and highly purified fat body mitochondria were isolated. Swelling measurement confirmed abnormal mitochondrial swelling caused by abamectin stress. The activity of two key mitochondrial energy metabolism-related enzymes, namely succinic dehydrogenase and isocitrate dehydrogenase, was significantly affected. The metabolomic responses of the isolated mitochondria to abamectin were analyzed via untargeted liquid chromatography/mass spectrometry metabolomics technology. Fifty-two differential metabolites (DMs) were identified in the mitochondria between the 0.001 mg/mL abamectin-fed and the control groups. Many of these DMs were significantly enriched in pathways involved in ATP production and energy consumption (e.g., oxidative phosphorylation, TCA cycle, and pentose phosphate pathway). Nineteen of the DMs were typically related to energy metabolism. This study is valuable for further understanding mitochondrial toxicology under environmental toxicants, particularly its subcellular level.

Metabolomics as a valid analytical technique in environmental exposure research: application and progress

BACKGROUND

In recent years, studies have shown that exposure to environmental pollutants (e.g., radiation, heavy metal substances, air pollutants, organic pollutants) is a leading cause of human non-communicable diseases. The key to disease prevention is to clarify the harmful mechanisms and toxic effects of environmental pollutants on the body. Metabolomics is a high-sensitivity, high-throughput omics technology that can obtain detailed metabolite information of an organism. It is a crucial tool for gaining a comprehensive understanding of the pathway network regulation mechanism of the organism. Its application is widespread in many research fields such as environmental exposure assessment, medicine, systems biology, and biomarker discovery.

AIM OF REVIEW

Recent findings show that metabolomics can be used to obtain molecular snapshots of organisms after environmental exposure, to help understand the interaction between environmental exposure and organisms, and to identify potential biomarkers and biological mechanisms.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review focuses on the application of metabolomics to understand the biological effects of radiation, heavy metals, air pollution, and persistent organic pollutants exposure, and examines some potential biomarkers and toxicity mechanisms.

Concentrations and distribution of chlorinated paraffins in Belgian foods

This study reports on concentrations of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs, respectively) in a wide range of food samples (n = 211) purchased in Belgium during 2020. Samples were analysed by gas chromatography-mass spectrometry (GC-MS) and quantified using chlorine content calibration. ∑SCCPs were present above LOQ in 25% of samples with an overall range of <LOQ to 58 ng/g wet weight (ww), while ∑MCCPs were identified in 66% of samples ranging from <LOQ to 250 ng/g ww. ∑MCCP concentrations were greater than those of ∑SCCPs in all 48 samples in which both groups were detected with an average ∑MCCP/∑SCCP ratio of 5.8 (ranging from 1.3 to 81). In general, the greatest CP concentrations were observed in foods classified as animal and vegetable fats and oils and sugar and confectionary for both SCCPs and MCCPs. Significant correlations between lipid content in food samples and CP levels illustrated the role of lipids in accumulating CPs within foodstuffs, while industrial processing, food packaging and environmental conditions are each likely to contribute to overall CP loads. Selected samples (n = 20) were further analysed by liquid chromatography-high resolution MS (LC-HRMS) to investigate homologue profiles and the occurrence of long-chain CPs (LCCPs). LCCPs were detected in 35% of the 20 subset samples while the HRMS results for SCCPs and MCCPs matched closely with those obtained by GC-MS. This study reveals the widespread occurrence of SCCPs and MCCPs in Belgian food and indicates that LCCPs may represent a substantial contribution to overall CP levels in foodstuffs.