Compound degraded:Short-chain chlorinated paraffins (SCCPs)

General Description (About POP compound)

Chlorinated paraffins (CPs), also known as poly-chlorinated n-alkanes (PCAs), are complex halogenated mixtures which comprise various carbon chain lengths and chlorine atoms and are normally produced by the chlorination of n-alkane feed stocks with molecular chlorine under forcing conditions such as ultraviolet light and high temperature. CPs are generally hydrophobic and semi-volatile, ranging from colourless to yellowish liquids. The three subgroups of CPs are divided based on their carbon chain length: short-chain chlorinated paraffins (SCCPs, C10–C13), middle-chain chlorinated paraffins (MCCPs, C14–C17) and long-chain chlorinated paraffins (LCCPs, C > 18)

Biodegradation pathway

Publications

Abstract Title Authors Article Link
Short-chain chlorinated paraffins (SCCPs) are listed as persistent organic pollutants (POPs) under the Stockholm Convention. Such substances are toxic, bioaccumulating, transported over long distances and degrade slowly in the environment. Certain bacterial strains of the Sphingomonadacea family are able to degrade POPs, such as hexachlorocyclohexanes (HCHs) and hexabromocyclododecanes (HBCDs). The haloalkane dehalogenase LinB, expressed in certain Sphingomonadacea, is able to catalyze the transformation of haloalkanes to hydroxylated compounds. Therefore, LinB is a promising candidate for conversion of SCCPs. Hence, a mixture of chlorinated tridecanes was exposed in vitro to LinB, which was obtained through heterologous expression in Escherichia coli. Liquid chromatography mass spectrometry (LC-MS) was used to analyze chlorinated tridecanes and their transformation products. A chloride-enhanced soft ionization method, which favors the formation of chloride adducts [M+Cl]- without fragmentation, was applied. Mathematical deconvolution was used to distinguish interfering mass spectra of paraffinic, mono-olefinic and di-olefinic compounds. Several mono- and di-hydroxylated products including paraffinic, mono-olefinic and di-olefinic compounds were found after LinB exposure. Mono- (rt = 5.9–6.9 min) and di-hydroxylated (rt = 3.2–4.5 min) compounds were separated from starting material (rt = 7.7–8.5 min) by reversed phase LC. Chlorination degrees of chlorinated tridecanes increased during LinB-exposure from nCl = 8.80 to 9.07, indicating a preferential transformation of lower chlorinated (Cl<9) tridecanes. Thus, LinB indeed catalyzed a dehalohydroxylation of chlorinated tridecanes, tridecenes and tridecadienes. The observed hydroxylated compounds are relevant CP transformation products whose environmental and toxicological effects should be further investigated. Transformation of short-chain chlorinated paraffins by the bacterial haloalkane dehalogenase LinB – Formation of mono- and di-hydroxylated metabolites Knobloch et al., 2021 Link
Short chain chlorinated paraffins SCCPs are priority hazardous substances classified by the European Water Framework Directive and have been detected in sewage sludge of wastewater treatment plants worldwide. However, studies on the biodegradation of SCCPs presented in sewage sludge are very scarce. In this study, a bacterial strain that can utilize SCCPs as a sole source of carbon and energy was isolated from soil. This strain was identified as Pseudomonas sp. N35. The efficacy of SCCP degradation by strain N35 was tested in pure culture and sewage sludge microcosms containing 66.1?mg?kg–1 SCCPs. The results showed that 57.5% of chloride was released into the medium as chloride ions in pure culture within 20?days. Mesophilic temperature and near-neutral pH were most favorable for SCCP degradation. The addition of low concentrations of glucose, Tween-80 and acetone (20?mg?L–1) enhanced SCCP degradation. Bioaugmentation resulted in 73.4% removal of SCCPs in the sludge microcosm after 30?days of treatment. Bioaugmentation with specific strains may be of great significance in bioremediation of SCCP-containing sewage sludge. Degradation of short chain polychlorinated paraffins by a new isolate: tests in pure culture and sewage sludge Lu. 2012 Link
In the past decades, the environmental presence and ecological risks of chlorinated paraffins (CPs), an emerging class of organic halogen compounds, have been receiving increasing attention worldwide. Short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) constitute the important CPs of considerable concern. In this review article, the state-of-the-art research status on the environmental transformation of CPs, including thermal decomposition, photolytic and photocatalytic degradation, biological metabolism, and atmospheric transformation, was summarized and integrated in detail. The degradation efficiency and transformation products of CPs in these environmental processes were evaluated, in which dechlorination was considered as the major reaction pathway. Notably, waste incineration of CPs has been demonstrated to generate a variety of persistent chlorinated aromatic hydrocarbons such as polychlorinated biphenyls and polychlorinated naphthalenes, which have more significant environmental impacts. Additionally, photodegradation and photocatalysis are suggested as the feasible techniques for efficient removal of SCCPs from water matrices. Overall, the current transformation studies of CPs could facilitate the comprehensive understanding of their environmental behaviors and fate as well as the development of promising remediation strategies for pollution control. Transformation pathways of chlorinated paraffins relevant for remediation: a mini-review Yuan et al., 2021 Link
Chlorinated paraffins (CPs) have been applied as additives in a wide range of consumer products, including polyvinyl chloride (PVC) products, mining conveyor belts, paints, sealants, adhesives and as flame retardants. Consequently, CPs have been found in many matrices. Of all the CP groups, short-chain chlorinated paraffins (SCCPs) have raised an alarming concern globally due to their toxicity, persistence and long-range transportation in the environment. As a result, SCCPs were listed in the Stockholm Convention on Persistent Organic Pollutants (POPs) in May 2017. Additionally, a limit for the presence of SCCPs in other CP mixtures was set at 1% by weight. CPs can be released into the environment throughout their life cycle; therefore, it becomes crucial to assess their effects in different matrices. Although about 199 studies on SCCP concentration in different matrices have been published in other continents; however, there are scarce/or limited studies on SCCP concentration in Africa, particularly on consumer products, landfill leachates and sediment samples. So far, published studies on SCCP concentration in the continent include SCCPs in egg samples, e-waste recycling area and indoor dust in Ghana and South Africa, despite absence of any production of SCCPs in Africa. However, there still remains a huge research gap in the continent of Africa on SCCPs. Consequently, there is a need to develop robust SCCP inventories in Africa since the Stockholm Convention has already developed guidance document in this respect. This review, therefore, examines the state of knowledge pertaining to the levels and trends of these contaminants in Africa and further provides research gaps that need to be considered in order to better understand the global scale of the contaminant. Status of short-chain chlorinated paraffins in matrices and research gap priorities in Africa: a review Nevondo and Okonkwo. 2021 Link
Chlorinated paraffins (CPs) are widely used in domestic polymeric products as plasticizers and fire retardants. In this study, concentrations and congener profiles of short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) were investigated in domestic polymeric products, including plastics, rubber and food packaging in China. The average concentrations of SCCPs in polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE) and food packaging were 234, 3968, 150 and 188?ng/g, respectively and the corresponding average concentrations of MCCPs in these samples were 37.4, 2537, 208 and 644?ng/g, respectively. The concentrations of CPs in rubber and polyvinylchloride (PVC) were significantly higher than in other matrices. The highest concentrations of SCCPs and MCCPs were found in a PVC cable sheath with 191?mg/g and 145?mg/g, respectively. Congener group profiles analysis indicated C11- and C13-congener groups were predominant in carbon homologues of SCCPs, and C14-congener groups were predominant in MCCPs. High levels of SCCPs and MCCPs in domestic polymeric products implied that they might be a significant source to the environment and human exposure. Concentrations and congener profiles of chlorinated paraffins in domestic polymeric products in China Wang et al., 2018 Link
Polychlorinated n-alkanes (PCAs) or chlorinated paraffins are highly complex technical mixtures that contain a large number of structural isomers, including diastereomers and enantiomers. They are persistent organic pollutants of concern due to their toxicological properties, their capacity to bioaccumulate and their widespread, unrestricted use. Recently, these compounds were included in regulatory programs of international organizations, including the US Environmental Protection Agency and the European Union.We review the literature on the properties of PCAs, the existing data on production, uses, releases and fate, and concentrations found in the environment. In particular, we summarize and compare concentrations of PCAs in environmental compartments, including air, water, sediments, biota, terrestrial wildlife and human food.Estimates of concentrations in different environmental compartments suggest that significant amounts of PCAs are still in use and being released in several countries. Data are needed to evaluate exposure to PCAs in the environment, particularly in the light of their continued production and usage around the world. Occurrence, fate and analysis of polychlorinated n-alkanes in the environment Feo et al., 2009 Link
Concerns about the high production volumes, persistency, bioaccumulation potential and toxicity of chlorinated paraffin (CP) mixtures, especially short-chain CPs (SCCPs), are rising. However, information on their levels and fate in the environment is still insufficient, impeding international classifications and regulations. This knowledge gap is mainly due to the difficulties that arise with CP analysis, in particular the chromatographic separation within CPs and between CPs and other compounds. No fully validated routine analytical method is available yet and only semi-quantitative analysis is possible, although the number of studies reporting new and improved methods have rapidly increased since 2010. Better cleanup procedures that remove interfering compounds, and new instrumental techniques, which distinguish between medium-chain CPs (MCCPs) and SCCPs, have been developed. While gas chromatography coupled to an electron capture negative ionisation mass spectrometry (GC/ECNI-MS) remains the most commonly applied technique, novel and promising use of high resolution time of flight MS (TOF-MS) has also been reported. We expect that recent developments in high resolution TOF-MS and Orbitrap technologies will further improve the detection of CPs, including long-chain CPs (LCCPs), and the group separation and quantification of CP homologues. Also, new CP quantification methods have emerged, including the use of mathematical algorithms, multiple linear regression and principal component analysis. These quantification advancements are also reflected in considerably improved interlaboratory agreements since 2010. Analysis of lower chlorinated paraffins (<Cl5) remains, however, challenging and better approaches to analysing these homologues are needed. Furthermore, suitable quantification standards would facilitate improving the quality of CP analysis. Recent developments in capabilities for analysing chlorinated paraffins in environmental matrices: A review Mourik et al., 2015 Link