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

Short-chain chlorinated paraffins induce hippocampal damage and glycerophospholipids disruption contributing to neurobehavioral deficits in mice

Short-chain chlorinated paraffins (SCCPs), a class of widely used industrial chemicals, have raised significant health concerns due to their persistence, bioaccumulation, and potential neurotoxicity. This study investigated the neurotoxic effects of SCCPs on the hippocampus and their impact on brain glycerophospholipid metabolism in mice. Behavioral tests revealed that 50 mg/kg SCCPs exposure significantly reduced spontaneous activity and impaired learning and memory. Pathological examination showed neuronal damage, including nuclear pyknosis and cytoplasmic vacuolization, in the hippocampus. Biochemical analyses indicated elevated oxidative stress markers (reactive oxygen species, malondialdehyde) and decreased antioxidant levels (glutathione, superoxide dismutase), alongside reduced levels of neurotransmitters (5-Hydroxytryptamine, dopamine, brain-derived neurotrophic factor). Lipidomics analysis identified significant alterations in glycerophospholipid metabolites, such as decreased levels of phosphatidylcholine and phosphatidylserine. Immunohistochemistry demonstrated downregulation of tight junction proteins (Claudin-1, ZO-1), suggesting blood-brain barrier disruption. These findings highlight SCCPs' potential to induce hippocampal oxidative stress, neurotransmitter dysregulation, decreased claudin-1 expression and glycerophospholipid metabolism disruption, contributing to neurobehavioral deficits. This study provides insights into the mechanisms of SCCPs-induced neurotoxicity and emphasizes their potential implications for brain health.

Automated detection and recognition of oocyte toxicity by fusion of latent and observable features

Oocyte quality is essential for successful pregnancy, yet no discriminant criterion exists to assess the effects of environmental pollutants on oocyte abnormalities. We developed a stepwise framework integrating deep learning-extracted latent features with observable human-concept features focused on toxicity detection, subtype and strength classification. Based on 2126 murine oocyte images, this method achieves performance surpassing human capabilities with ROC-AUC of 0.9087 for toxicity detection, 0.7956-0.9034 for subtype classification with Perfluorohexanesulfonic Acid(PFHxS) achieving highest score of 0.9034 and 0.6434-0.9062 for toxicity strength classification with PFHxS achieving highest score of 0.9062. Notably, Ablation studies confirmed feature fusion improved performance by 18.7-23.4 % over single-domain models, highlighting their complementary relationship. Personalized heatmaps and feature importance revealed biomarker regions such as polar body and cortical areas aligning with clinical knowledge. AI-driven oocyte selection predicts embryo competence under pollutants, bridging computational toxicology to mitigate infertility.

Medium-Chain Chlorinated Paraffins Induced Reproductive Toxicity in Female Rats by Interfering with Oocyte Meiosis and Triggering DNA Damage

Medium-chain chlorinated paraffins (MCCPs) are among the most prevalent chemicals detected in human serum. As an emerging persistent organic pollutant, their toxicity mechanisms, particularly concerning the female reproductive system, remain poorly understood. In this study, we present both in vivo and in vitro evidence of ovarian toxicity induced by MCCPs and insights into their underlying molecular mechanisms. MCCP exposure induced chromatin condensation in the nucleus and mitochondria vacuolization of ovarian granulosa cells in rats and significantly increased the levels of serum gonadotropins and sex hormones, while reducing gonadotropin-releasing hormone levels. Transcriptomics analysis of ovaries revealed a predominant effect of MCCPs on the cell cycle, oocyte meiosis, and DNA damage repair pathways. Moreover, dual-omics integrative analysis indicated significant disturbance of steroid hormone biosynthesis caused by MCCPs, as well as amino acid metabolism related to TCA cycle. Furthermore, in vitro assays demonstrated that MCCP exposure disrupts intracellular Ca2+ homeostasis and generates reactive oxygen species, ultimately leading to DNA damage. In conclusion, this study revealed potential mechanisms by which MCCPs affect ovary function. These findings can provide valuable insights for the mechanism-based risk assessment of MCCPs on female reproduction.

Human exposure to polychlorinated alkanes (C8-36) in soil and dust from Nigerian e-waste sites: Occurrence, homologue pattern and health risk assessment

Electronic waste (e-waste) dismantling and dumpsite processes are recognized as significant sources of chlorinated paraffin (CP) exposure. This study aims to investigate the environmental occurrence and distribution of polychlorinated alkanes (PCAs-C8-36), specifically in soil and outdoor dust samples collected from e-waste dumpsites and automobile dismantling and resale sites in Nigeria. The results revealed a widespread occurrence of PCAs across all sampled locations. For the PCAs homologue groups ∑PCAs-C10-13, ∑PCAs-C14-17, and ∑PCAs-C18-20, the median concentrations were 1150 ng/g dry weight (dw), 1180 ng/g dw, and 370 ng/g dw in the dust samples, and 2840 ng/g dw, 1820 ng/g dw, and 830 ng/g dw in the soil samples, respectively. Notably, the homologue distribution patterns of PCAs-C8-36 were similar in both dust and soil samples. However, PCAs-C10-13 was found to be higher in the soil samples, likely due to the wet and/or dry deposition effect of the aerosols, given these chemicals' volatile nature and ease of atmospheric dispersion. Pearson correlation analysis further revealed a co-occurrence of contaminants in the soil samples, supporting the hypothesis that soil acts as a sink for persistent organic pollutants (POPs). Additionally, lower molecular weight polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) showed reduced correlation with the PCAs. Health risk assessments indicated that working on e-waste sites could potentially pose a risk to the workers' health. This study highlights the urgent need for mitigating occupational exposure to PCAs, especially in informal e-waste processing environments where personal protective measures are often lacking.

Short- and medium-chain polychlorinated alkanes in the air of Athens, Greece

The atmospheric occurrence and partition between the gas and particulate phase of short- (PCAs-C10-13) and medium-chain (PCAs-C14-17) polychlorinated alkanes (PCAs) were investigated during two sampling campaigns in Athens city, Greece. The concentrations of PCAs ranged between 1.46 and 43.6 ng m-3 in the gas phase, and between 5.8 and 40.3 ng m-3 in the particulate phase, which were within the reported levels in Europe. Significant seasonal variation was observed for PCAs-C10-13 and PCAs-C14-17 in the gas phase. C10Cl6-7 and C14Cl6-8 were the predominant short- and medium-chain congeners, respectively. Gas-phase PCAs exhibited significant positive correlation with temperature, and negative correlation with relative humidity. Diagnostic ratios of medium to short-chain PCAs suggested that ΣPCAs in total suspended particle (TSP) mainly originated from local sources. Furthermore, the relationship between partitioning coefficient Kp and the subcooled liquid pressure (PL°) was investigated. Moreover, Positive Matrix Factorization (PMF) analysis was employed to identify the potential ΣPCAs groups of sources. Finally, the estimated risk of inhalation exposure to ΣPCAs for adults and children was found to be low.

Temporal trends and spatial variations of chlorinated paraffins and olefins in sewage sludge from eight Swiss wastewater treatment plants from 1993 to 2020

High production rates of chlorinated paraffins (CPs) and their widespread use resulted in a global contamination. Since 2017, short-chain CPs (SCCPs, C10-C13) are listed as persistent organic pollutants (POPs) in the Stockholm Convention. Technical CP mixtures contain hundreds of homologues and side products such as chlorinated olefins (COs), diolefins (CdiOs) and triolefins (CtriOs). Sewage sludge from wastewater treatment plants (WWTPs) is a suitable indicator to assess anthropogenic emissions of POPs. We studied 40 sewage sludge samples from eight WWTPs taken in 1993, 2002, 2007, 2012 and 2020. These samples represent effluents of households of ∼344000 inhabitants corresponding to 4% of the Swiss population. Extracts were studied by liquid chromatography high-resolution mass spectrometry (LC-MS, R > 100000). Respective mass spectra contained more than 20000 m/z values which were evaluated with the R-based automated spectra evaluation routine (RASER). We assigned ∼4300 ions to 226 CP, 94 CO, 32 CdiO and 26 CtriO homologues. Proportions of olefinic material were on average 8%, 1% and <1%, respectively. Homologue distributions from 1993 sludge were rich in SCCPs (26%) and SCCOs (36%). Average SCCP levels dropped by 85% from 15600 ± 14300 (1993) to 2370 ± 840 ng/g dry matter (2020). Thus, SCCP emissions from Swiss households and industry were reduced successfully from 1993 to 2020. Levels of medium- (MCCPs, C14-C17), long- (LCCPs, C18-C21) and very long-chain CPs (vLCCPs, C ≥ 22) decreased by 67%, 11% and 11%. 2020 samples contained some (<1%) very short-chain CPs (vSCCPs, C ≤ 9). Spatial variations for different WWTPs are minor, except for one, which received high MCCP loads from 2002 to 2012. We assume that wastewater from a point source has reached this plant in those years. According to the levels of sludge from WWTPs, we conclude that the use of SCCPs in Swiss households and thus the exposure of people was reduced in the last three decades.

Investigating polychlorinated alkanes in technical chlorinated paraffin mixtures and polymer products available in Vietnam

Chlorinated paraffins (CPs) are chemical additives mostly composed of polychlorinated alkanes (PCAs) which may impact on the environment and human health; however, little is known about their presence in Southeast Asia. To fill this knowledge gap, we assessed 74 PCA homolog groups commonly referred to as short-chain (SCCPs: PCAs-C10-13), medium-chain (MCCPs: PCAs-C14-17), and long-chain CPs (LCCPs: PCAs-C18-20) in technical CP mixtures (n = 4) and polymer samples (n = 49), including recycled plastics, collected in Vietnam in 2023. The contents of measured PCA homolog groups in technical CP mixtures were 86,000-930,000 mg/kg for PCAs-C10-13; 85,000-990,000 mg/kg for PCAs-C14-17; and 23,000-180,000 mg/kg for PCAs-C18-20. Total PCAs-C10-20 levels in polymer samples varied from 0.26 to 28,000 mg/kg and decreased in the order: soft plastic bag, electrical cable sheath, football pitch rubber, polyurethane hose, heat shrinkable tubing, spiral cable cover, plastic powder, and plastic drawstring. In polymer samples, PCAs-C14-17 were found at greater levels (mean/median: 3000/65 mg/kg) than PCAs-C18-20 (1300/9.5 mg/kg) and PCAs-C10-13 (740/16 mg/kg). The contents of total measured PCAs-C10-20 in polyvinyl chloride samples varied according to their life cycle stages, with higher levels found in recycled plastics than in feedstock and commercial product samples. The occurrence of PCAs-C10-13 in polymer samples above internationally proposed limits for PCAs-C10-13 in consumer goods and waste pose a conundrum for the implementation of a safe circular economy and may impact human health in Vietnam. Therefore, this study highlights key challenges for the through implementation of the Basel, Rotterdam, and Stockholm Conventions and the importance of further comprehensive investigations in Vietnam and other developing countries.

Long-chain chlorinated paraffins (LCCPs) exposure causes senescence and inflammatory damage in cardiomyocytes

Humans can be exposed to LCCPs through air and diet, leading to their accumulation in the body. Given the significance of understanding potential health risks, a thorough investigation into the detrimental health impacts of LCCPs is paramount. In this study, we conducted a series of experiments to investigate the effects of LCCPs on cardiomyocytes, employing techniques such as flow cytometry, western-blot, indirect immunofluorescence, and confocal microscopy. We initially observed that LCCPs caused senescence damage to cardiomyocytes. Under the stimulation of LCCPs, the number of SA-β-Gal positive cardiomyocytes increased, along with an elevation in the protein expression levels of cellular senescence markers (p21, p16). The cell cycle was arrested in the S phase. Subsequently, we observed that LCCPs also induced an increase in ROS and inflammatory cytokines (IL-6, IL-8, TNF-α), as well as a decrease in MMP in cardiomyocytes. Mechanistic studies revealed that LCCPs activated the innate immune response pathway-cGAS-STING pathway, and the cellular senescence damage caused by LCCPs was alleviated upon the addition of a cGAS-STING inhibitor. In conclusion, our findings suggest that LCCPs can induce aging damage in cardiomyocytes by activating the cGAS-STING signaling pathway. This study indicates that LCCPs possesses potential cardiotoxicity and offers necessary experimental data for their rational and regulated utilization.

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.

Chlorinated paraffins in particulate matter associated with asthma and its relative symptoms in school-aged children and adolescents: A cross-sectional survey in South China

Particulate matter (PM) and contaminants attached to PM can increase the risk of respiratory diseases. However, the health risk assessment of chlorinated paraffins (CPs), an emerging pollutant occupying a high proportion of persistent organic pollutants (POPs) in PM, remains scarce. This study aimed to evaluate the association between PM2.5-bound CPs and asthma, along with relative symptoms, in school-aged children and adolescents. A large sample size cross-sectional study (n = 131,304) was conducted in the Pearl River Delta (PRD). The results showed that increased quantiles of ∑CPs were associated with odds ratios (ORs) of 1.22 (95%CI: 1.20-1.25), 1.38 (95%CI: 1.35-1.41), 1.17 (95%CI: 1.15-1.19), 1.52 (95%CI: 1.48-1.56), 1.66 (95%CI: 1.61-1.71), and 1.33 (95%CI: 1.30-1.37) for ever diagnosed asthma, current asthma, wheeze, current wheeze, persistent phlegm, and persistent cough, respectively. Additionally, C11-, C12-SCCPs and C14-, C17-MCCPs contributed the most positive weight to the risk of asthma and relative symptoms. These findings provide cutting-edged evidence for the health risk assessment of CPs, which is crucial for developing effective CPs management strategy.

Impact of anthropogenic activities on atmospheric chlorinated paraffins in Ghana using polyurethane foam disk - passive air sampler

Chlorinated paraffins (CPs) are a global concern due to their high production, ubiquity in the environment and potential toxicity. In Ghana, there is a significant research gap on the concentration and sources of CPs in the air, as well as insufficient regular monitoring programs to track CP levels over time. This study utilized polyurethane foam-based passive air samplers (PUF-PAS) to examine the concentrations, sources and potential human health risks of CPs in the atmosphere surrounding e-waste sites, urban areas, commercial areas and control/background areas in Ghana. The medium-chain CPs (MCCPs) dominated with an average concentration of 26.0 ± 40.1 ng/m3 and ranged from 1.78 to 240 ng/m3. Short-chain CPs (SCCPs) ranged from 0.05 to 15.2 ng/m3 and had an average concentration of 3.48 ± 3.99 ng/m3. The very short-chain CPs (C9-CPs), had an average concentration of 0.544 ± 0.524 ng/m3 and ranged from 0.091 to 2.14 ng/m3. MCCPs exceeded SCCPs by a factor of 7.5 and C9-CPs by a factor of 48. C14Cl8 was the dominant congener in MCCPs and C10Cl7 was also the dominant congener in SCCPs. E-waste was the main contributor to SCCPs and MCCPs (>30 %) in Ghana. The assessed non-cancer risks associated with CP exposure were within acceptable ranges. For cancer risk, MCCPs indicated high potential health risk but C9-CPs and SCCPs showed low risk. To the best of our knowledge, this is the first study on CPs in Ghana's atmosphere, and e-waste was identified as the country's main source of CPs. This study will help regulatory bodies create policies and procedures to control the use and disposal of chlorinated paraffins.

Spatial distribution and air-soil exchange of short and medium chain chlorinated paraffins in Lahore, Pakistan

This study provides the first systematic data on the distribution of short- (SCCPs) and medium chlorinated paraffins (MCCPs) in the atmosphere and surface soils of Lahore, Pakistan. The spatial distribution of SCCPs and MCCPs in air (n = 12) and soil (n = 15) was investigated from industrial, residential, commercial, conventional e-waste burning and background areas of Lahore. The concentrations ranged from below the limit of detection ( Collapse

Key Words

• Exchange flux
• Fugacity fraction
• Land-use
• Risk assessment
• TOC

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MESH Headings

• Pakistan
• Environmental Monitoring
• Paraffin/analysis
• Soil Pollutants/analysis
• Air Pollutants/analysis
• Hydrocarbons, Chlorinated/analysis
• Soil/chemistry

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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

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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.

Physicochemical properties dominating the behaviors of short/medium chain chlorinated paraffins in the atmosphere

Chlorinated paraffins (CPs) are chlorinated alkane mixtures widely used as flame retardants and plasticizers in multiple industrial products. Systematic research on how homolog-specific properties affect their atmospheric behaviors is limited. Herein, we investigated the levels of short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) in long-timescale, seasonal, and size-fractioned particles in the urban area of Dalian, a coastal city in northern China. The average SCCP and MCCP concentrations in particles with diameters ≤ 10 µm were 3.36 and 4.89 ng/m3, respectively, and a general increase in the SCCP concentration was observed from 2.59 ng/m3 in 2018 - 2019 to 7.84 ng/m3 in 2021 - 2023. CP levels and patterns showed significant seasonal variation, with a higher abundance of C11-13Cl7-9 in winter and C10-12Cl5 in summer. Elevated particle levels in winter and high temperatures in summer contributed to the seasonal variations. SCCPs and MCCPs were concentrated on particles with diameters of < 1 µm and their geometric mean diameter increased with the increasing carbon and chlorine numbers. Total Daily intake of SCCP and MCCP was calculated to be 0.15 and 0.22 ng/kg bw/day for adults. 53.1 %, 8.5 %, and 38.4 % of inhaled SCCPs, and 60.6 %, 7.6 %, and 31.8 % of inhaled MCCPs deposited into the head airway, tracheobronchial region, and alveolar region, respectively. This study reports on how homolog-specific physicochemical properties alter the temporal variations, size distributions, and inhaled fractions of CPs.

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.

Exposure to Short- and Medium-Chain Chlorinated Paraffins and the Risk of Gestational Diabetes Mellitus: A Nested Case-Control Study in Eastern China

Toxicological studies have indicated that exposure to chlorinated paraffins (CPs) may disrupt intracellular glucose and energy metabolism. However, limited information exists regarding the impact of human CP exposure on glucose homeostasis and its potential association with an increased risk of developing gestational diabetes mellitus (GDM). Here, we conducted a prospective study with a nested case-control design to evaluate the link between short- and medium-chain CP (SCCPs and MCCPs) exposures during pregnancy and the risk of GDM. Serum samples from 102 GDM-diagnosed pregnant women and 204 healthy controls were collected in Hangzhou, Eastern China. The median (interquartile range, IQR) concentration of SCCPs was 161 (127, 236) ng/mL in the GDM group compared to 127 (96.9, 176) ng/mL in the non-GDM group (p < 0.01). For MCCPs, the GDM group had a median concentration of 144 (117, 174) ng/mL, while the control group was 114 (78.1, 162) ng/mL (p < 0.01). Compared to the lowest quartile as the reference, the adjusted odds ratios (ORs) of GDM were 7.07 (95% CI: 2.87, 17.40) and 3.34 (95% CI: 1.48, 7.53) in the highest quartile of ∑SCCP and ∑MCCP levels, respectively, with MCCPs demonstrating an inverted U-shaped association with GDM. Weighted quantile sum regression evaluated the joint effects of all CPs on GDM and glucose homeostasis. Among all CP congeners, C13H23Cl5 and C10H16Cl6 were the crucial variables driving the positive association with the GDM risk. Our results demonstrated a significant positive association between CP concentration in maternal serum and GDM risk, and exposure to SCCPs and MCCPs may disturb maternal glucose homeostasis. These findings contribute to a better understanding of the health risks of CP exposure and the role of environmental contaminants in the pathogenesis of GDM.

Polychlorinated alkanes in paired blood serum and breast milk in a Swedish cohort study: Matrix dependent partitioning differences compared to legacy POPs

BACKGROUND

Polychlorinated alkanes (PCAs) constitute a large group of individual congeners originating from commercial chlorinated paraffin (CP) products with carbon chain lengths of PCAs-C10-13, PCAs-C14-17, and PCAs-C18-32, occasionally containing PCAs-C6-9 impurities. The extensive use of CPs has led to global environmental pollution of PCAs. This study aimed to quantify PCAs in paired serum and breast milk of lactating Swedish mothers, exploring their concentration relationship.

METHODS

Twenty-five paired samples of mothers' blood serum and breast milk were analysed and concentrations were determined for PCAs C6-32 and compared to 4,4'-DDE, the PCB congener 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153), and hexachlorobenzene (HCB).

RESULTS

The median concentrations of PCAs-C6-9, PCAs-C10-13, PCAs-C14-17, PCAs-C18-32 and ΣPCAs in serum were 14, 790, 520, 16 and 1350 ng/g lipid weight (lw), respectively, and in breast milk 0.84, 36, 63, 6.0 and 107 ng/g lw. Levels of 4,4'-DDE, CB-153 and HCB were comparable in the two matrices, serum and breast milk at 17, 12 and 4.9 ng/g lw. The results show significant differences of PCAs-C10-13 and PCAs-C14-17 in breast milk with 22- and 6.2-times lower lw-based concentrations than those measured in serum. On wet weight the differences serum/breast milk ratios of PCAs-C6-9, PCAs-C10-13, PCAs-C14-17, PCAs-C18-32 and ΣPCAs were 1.7, 3.2, 1.0, 0.4 and 1.6, respectively, while the ratio for 4,4'-DDE, CB-153 and HCB were each close to 0.1.

CONCLUSION

Swedish lactating mothers had high serum concentrations of PCAs-C10-13 and PCAs-C14-17, with the ΣPCAs median serum concentration of 1350 ng/g lw. The breast milk concentration, although considerably lower at 107 ng/g lw, still surpassed those of 4,4'-DDE, CB-153 and HCB, suggesting an exposure risk of infants to PCAs. The variation in blood and breast milk accumulation between PCAs and studied legacy POPs, is rarely discussed but warrants further studies on partitioning properties as well as associated toxicological implications.