Development of matrix solid-phase dispersion method for the extraction of short-chain chlorinated paraffins in human placenta

In vitro assessment of potential endocrine disrupting activities of chlorinated paraffins of various chain lengths

The production of chlorinated paraffins (CPs) has risen in the past two decades due to their versatile industrial applications. Consequently, CPs are now widely detected in human food sources, the environment, and in human matrices such as serum, the placenta and breast milk. This raises concern about prenatal and postnatal exposure. While some studies suggest that certain short-chained CPs (SCCPs) may have endocrine disrupting properties, knowledge about potential endocrine disrupting potential of medium- (MCCP) and long-chained CPs (LCCPs) remains relativity sparse. Here, we used a panel of in vitro assays to investigate seven pure CPs and two technical mixtures of CPs. These varied in chain length and, chlorination degree. The in vitro panel covered androgen, estrogen, and retinoic acid receptor activities, transthyretin displacement, and steroidogenesis. One of the SCCPs inhibited androgen receptor (AR) activity. All SCCPs induced estrogen receptor (ER) activity. Some SCCPs and MCCPs increased 17β-estradiol levels in the steroidogenesis assay, though not consistently across all substances in these groups. SCCPs exhibited the most pronounced effects in multiple in vitro assays, while the tested LCCPs showed no effects. Based on our results, some CPs can have endocrine disrupting potential in vitro. These findings warrant further examinations to ensure that CPs do not cause issues in intact organisms, including humans.

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.

Prenatal and postnatal exposure risk assessment of chlorinated paraffins in mothers and neonates: Occurrence, congener profile, and transfer behavior

Gestation and lactation are very sensitive and vulnerable stages for human growth and development. During these two periods, short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) can be transported to neonates via transplacental and breastfeeding transfers, and eventually posing potential adverse effects to neonates. Up to date, no simultaneous investigation of prenatal and postnatal exposure of CPs is reported. To bridge this knowledge gap, we have analyzed SCCPs and MCCPs in 20 complete sets of maternal serum, umbilical cord serum, placenta, and breast milk. The levels of both ∑SCCP and ∑MCCP followed the order of maternal serum > breast milk > cord serum > placenta. The breastfeeding transfer ratios (R_BM, ≈ 1.0) of CPs were greater than the corresponding transplacental transfer ratios (R_CM, < 1.0), demonstrating the higher transport of CPs during the lactation period. The placental retention/or accumulation ratios (R_PM) showed that CPs were effectively retained by the placental barrier. Furthermore, the total exposure amount of SCCPs and MCCPs during the lactation period was> 100 times higher than the gestation exposure amounts. This study helps to better understand the prenatal and postnatal exposure of CPs and provides a solid basis for accurate human health risk assessment of CPs.

Methods for trace analysis of short-, medium-, and long-chain chlorinated paraffins: Critical review and recommendations

Many methods for quantifying chlorinated paraffins (CPs) yield only a total concentration of the mixture as a single value. With appropriate analytical instrumentation and quantification methods, more reliable and detailed analysis can be performed by quantifying total concentrations of short-, medium-, and long-chain CPs (SCCPs, MCCPs, and LCCPs), and in the current optimal situation by quantifying individual carbon-chlorine congener groups (C_nCl_m). Sample extraction and clean-up methods for other persistent organochlorines that have been adapted for recovery of CPs must be applied prior to quantification with appropriate quality assurance and quality control to ensure applicability of the methods for SCCPs, MCCPs, and LCCPs. Part critical review, part tutorial, and part perspective, this paper provides practical guidance to analytical chemists who are interested in establishing a method for analysis of CPs in their lab facilities using commercial reference standards, or for expanding existing analysis of total CPs or SCCPs to analysis of SCCPs, MCCPs, and LCCPs, or to analysis of C_nCl_m congener groups.

The thermal transformation mechanism of chlorinated paraffins: An experimental and density functional theory study

The increasing production and usage of chlorinated paraffins (CPs) correspondently increase the amount of CPs that experience thermal processes. Our previous study revealed that a significant amount of medium-chain chlorinated paraffins (MCCPs), short-chain chlorinated paraffins (SCCPs) as well as aromatic and chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) were formed synergistically during the thermal decomposition of CP-52 (a class of CP products). However, the transformation mechanisms of CP-52 to these compounds are still not very clear. This article presents a mechanistic analysis on the decomposition of CP-52 experimentally and theoretically. It was found that CP-52 initially undergoes dehydrochlorination and carbon chain cleavage and it transformed into chlorinated and unsaturated hydrocarbons. Cyclization and aromatization were the most accessible pathways at low temperatures (200-400°C), both of which produce mostly aromatic hydrocarbons. As the temperature exceeds 400°C, the hydrocarbons could decompose into small molecules, and the subsequent radical-induced reactions become the predominant pathways, leading to the formation of Cl-PAHs. The decomposition of CP-52 was investigated by using density functional theory and calculations demonstrating the feasibility and rationality of PCB and PCN formation from chlorobenzene. The results improve the understanding of the transformation processes from CP-52 to SCCPs and Cl-PAHs as well as provide data for reducing their emissions during thermal-related processes.

Elimination of short-chain chlorinated paraffins in diet after Chinese traditional cooking-a cooking case study

Short-chain chlorinated paraffins (SCCPs) were listed in the Stockholm Convention in 2017 yet are still used in large-tonnage in China. Diet is the main external exposure pathway of many persistent organic pollutants (POPs), but SCCP diet exposure has not been studied completely thus far. In this study, samples of 122 raw foods were collected from markets in Beijing, cooked with Chinese traditional cooking methods, and analyzed for SCCPs. Overall, SCCP levels in the raw food materials ranged from0.67 to 5100 ng g^-1 wet weight (ww). SCCP elimination was found in six out of seven kinds in the cooking case study. Concentrations in the raw food used for cooking ranged from 3.6 to 52 ng g^-1 ww, while the corresponding values in the cooked food ranged from 0.67 to 10.8 ng g^-1 ww. The SCCP elimination rate ranged from 12% to 93%. The daily average intake of SCCPs for the general population through raw food and cooked food was assessed. The total daily SCCP intake via these foods was 403 and 145 ng kg^-1 bw d^-1, which suggests that different assessing approaches may result in different estimated SCCP diet exposure amounts.