Highly elevated levels, infant dietary exposure and health risks of medium-chain chlorinated paraffins in breast milk from China: Comparison with short-chain chlorinated paraffins

First comprehensive assessment of dietary chlorinated paraffins intake and exposure risk for the rural population of the Tibetan Plateau, China

Knowledge regarding the occurrence of short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) in foodstuffs and their dietary exposure risks for rural Tibetan residents remains largely unknown. Herein, we collected main foodstuffs (including highland barley, vegetables, Tibetan butter, mutton, and yak beef) across the rural Tibetan Plateau and characterized the CP profiles and concentrations. The highest SCCPs concentrations were detected in Tibetan butter (geometric mean (GM): 240.6 ng/g wet weight (ww)), followed by vegetables (59.4 ng/g ww), mutton (51.4 ng/g ww), highland barley (46.3 ng/g ww), and yak beef (31.7 ng/g ww). For MCCPs, the highest concentrations were also detected in Tibetan butter (319.5 ng/g ww), followed by mutton (181.9 ng/g ww), vegetables (127.0 ng/g ww), yak beef (71.2 ng/g ww), and highland barley (30.3 ng/g ww). The predominant congener profiles of SCCPs were C13Cl7-8 in mutton and yak beef, C10Cl7-8 in Tibetan butter, and C10-11Cl6-7 in highland barley and vegetables. The predominant congener profiles of MCCPs were C14Cl7-9 in all sample types. Combined with our previous results of free-range chicken eggs, the median estimated daily intakes (EDIs) of SCCPs and MCCPs via diet for Tibetan rural adults and children was estimated to be 728.8 and 1853.9 ng/kg bw/day and 2565.6 and 5952.8 ng/kg bw/day, respectively. In the worst scenario, MCCPs might induce potential health risks for rural Tibetan population. To our knowledge, this is the first systematic dietary exposure research of SCCPs and MCCPs in the remote rural areas.

Short- and medium-chain chlorinated paraffins in 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.

Quantification of chlorinated paraffins by chromatography coupled to high-resolution mass spectrometry - Part B: Influence of liquid chromatography separation

The analysis of chlorinated paraffins (CPs) is today an analytical challenge. Indeed, it is still impractical to describe their real composition in terms of polychlorinated alkanes (PCAs) homologue groups, which dominate technical mixtures. The co-elution of PCA congeners generates interferences due to the competition phenomena which occur during the ionisation process as well as to the dependence of the ionisation sources on the PCA chemistry. Therefore, the aim of this study was to investigate the influence of chromatographic separation, by LC-ESI-HRMS coupling, on the PCA homologue group pattern and, eventually, on their determination in food samples from interlaboratory studies. For this, three different mobile phases and six LC chromatographic columns were studied in order to optimise the analysis of CP mixtures. The first results showed that the use of a MeOH/H2O mobile phase reveals more appropriately the higher chlorinated PCAs. However, using ACN/H2O led to less ion species, with almost exclusively [M + Cl]- adducts, formed using post-column dichloromethane addition. Regarding the choice of the stationary phases, Hypercarb column provided a completely different homologue group pattern from the other chromatographic columns, in relation with the stronger retention of PCAs. Among the other columns, the C30 column better highlighted the short-chain PCAs compared to the C18 column conventionally used. Because the regulations now concern short-chain CPs, the quantification of food samples was then carried out on the C30 column. The optimised LC-ESI-HRMS conditions using C30 column and MeOH/H2O solvent mixture led to a quantification of PCAs in samples from interlaboratory studies with satisfactory accuracy (|Z-score| ≤ 2) and precision (<15%).

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.

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.

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

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

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.

Fluorinated liquid-crystal monomers in paired breast milk and indoor dust: A pilot prospective study

Fluorinated liquid-crystal monomers (FLCMs), one class of emerging persistent, bioaccumulative and toxic (PBT) compounds, are widely used in liquid-crystal displays (LCDs). As a result, they have been found in the environment and serum from occupational workers. However, little is known about their occurrence in non-occupational exposing populations. Herein, we provided an evaluation of the health risks of FLCMs for infants based on breastfeeding exposure and dust ingestion. The detection frequencies (DF) of FLCMs in indoor dust and breast milk was 100 %, with median concentrations of 12.00 ng/g dry weight (dw) and 133.40 ng/g lipid weight (lw), respectively. 1-butoxy-2,3-difluoro-4-(trans-4-propylcyclohexyl)benzene (BDPrB) was the predominant pollutant in indoor dust and human breast milk. Significant positive correlations were observed between the dust concentrations of seven FLCMs including BDPrB, and their breast milk concentrations (r = 0.275-0.660, P < 0.05). Further, associations were also found in some demographic and behavioral factors and concentrations of some FLCMs (P < 0.05). The highest EDI of ∑FLCMs was observed for infants who were < 1 month of age, with a median breast milk intake of 700.35 ng/kg bw/day, in which 1-ethoxy-2,3-difluoro-4-(trans-4-propylcyclohexyl)benzene (EDPrB), BDPrB, and 4'-[(trans, trans)-4'-butyl[1,1'-bicyclohexyl]-4-yl]-3,4-difluoro-1,1'-biphenyl (BBDB) collectively contributed 94.4 % of the total EDIs. Notably, the lactational intake of FLCMs was higher than that of some environmental pollutants (EPs). Overall, our results suggest higher exposure risks for infants and breastfeeding is the predominant exposure route for daily intake of FLCMs for infants.

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.

Distribution and exposure risk assessment of chlorinated paraffins and novel brominated flame retardants in toys

Chlorinated paraffins (CPs) and novel brominated flame retardants (NBFRs) were examined in children's toys collected from 13 families in China. The concentrations of short-chain CPs (SCCPs), medium-chain CPs (MCCPs) and NBFRs in toys were 32.8-1,220,954 ng/g, not detected-2,688,656 ng/g and 0.08-103,461 ng/g, respectively. Median concentrations of SCCPs and MCCPs in toys were 1355 and 1984 ng/g, respectively, while except for pentabromobenzene (median:0.04 ng/g), the median concentrations of the other 8 NBFRs were below method detection limits. Rubber and foam toys contained higher amounts of CPs and NBFRs. Among the SCCPs and MCCPs monitored, Cl_6-8-SCCPs/MCCPs and C₁₄-MCCPs were the most abundant congener groups. On the other hand, decabromodiphenyl ethane was the predominant NBFR in toys. Moreover, to understand the role of toys in children's daily exposure to CPs and NBFRs, hand-to-mouth contact, mouthing, and dermal exposure were assessed for children aged 3 months to 6 years. Hand-to-mouth contact is the primary exposure route for children's exposure to CPs (25.4-536 ng/kg/day) and NBFRs (1.24-26.2 ng/kg/day) through toys. A low deleterious risk associated with children's toys concerning CPs and NBFRs was investigated based on the margin of exposure and hazard quotient values.

Bioaccumulation and Biotransformation of Chlorinated Paraffins

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

Short- and medium-chain chlorinated paraffins in honey from China: Distribution, source analysis, and risk assessment

Chlorinated paraffins (CPs) are industrial chemicals produced in large quantities. Short-chain CPs (SCCPs) were classified as persistent organic pollutants under the Stockholm Convention in 2017. Medium-chain CPs (MCCPs) became candidate persistent organic pollutants in 2021. CPs are now ubiquitously found in the environment. Honey bees can be exposed to CPs during foraging, and this exposure subsequently results in the contamination of honey and other bee products along with colony food production and storage. Here, SCCP and MCCP concentrations in honey collected from Chinese apiaries in 2015 and 2021 were determined. Total CP concentrations in honey from 2021 to 2015 were comparable, but the ratio of MCCPs/SCCPs was higher in 2021 than in 2015. SCCP and MCCP congener group profiles in all honey samples were similar and dominated by C₁₀-₁₁Cl_6-7 and C₁₄Cl_6-7, respectively. MCCP concentrations were also higher than SCCP concentrations in bees, pollen, and wax but not in bee bread, which were all collected in 2021. The order of average CP concentrations was determined as wax > bee > pollen > bee bread > honey. Poor relationships were found between SCCP concentrations in honey and other samples, but a relationship between MCCP concentrations in honey and other samples was observed. Migration tests of CPs in plastic bottles showed essentially no migration into honey during storage. The risks to humans from CPs in honey are low.

Critical review on disposition of chlorinated paraffins in animals and humans

Even though the chlorinated paraffins (CPs) have been on the environmental pollution agenda throughout the last 50 years it is a class of chemicals that only now is discussed in terms of an emerging issue with extensive annual publication rates. Major reviews on CPs have been produced, but a deeper understanding of the chemical fate of CPs, including formation of metabolites in animals and humans, is still missing. Thus, the present review aims to critically compile our present knowledge on the disposition, i.e. Adsorption, Disposition, Metabolism, and Excretion (ADME) of CPs in biota and to identify research needs. We conclude that CPs could be effectively absorbed from the gastro-intestinal tract (GI) tract, and probably also from the lungs, and transported to various organs. A biphasic elimination is suggested, with a rapid initial phase followed by a terminal phase, the latter (e.g., fat tissues) covering half-lives of weeks and months. CPs are metabolized in the liver and excreted mainly via the bile and faeces, and the metabolic rate and type of metabolites are dependent on chlorine content and chain length. Results that strengthen CP metabolism are in vivo findings of phase II metabolites in bile, and CP degradation to carbon fragments in experimental animals. Still the metabolic transformations of CPs are poorly studied, and no metabolic scheme has yet been presented. Further, toxicokinetic mass balance calculations suggest that a large part of a given dose (not found as parent compound) is transformation products of CPs, and in vitro metabolism studies present numerous CP metabolites (e.g., chloroalkenes, chlorinated ketones, aldehydes, and carboxylic acids).