Effect of short-chain chlorinated paraffins (SCCPs) on lipid membranes: Combination of molecular dynamics and membrane damage experiments

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.

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.

Microplastics Derived from Food Packaging Waste-Their Origin and Health Risks

Plastics are commonly used for packaging in the food industry. The most popular thermoplastic materials that have found such applications are polyethylene (PE), polypropylene (PP), poly(ethylene terephthalate) (PET), and polystyrene (PS). Unfortunately, most plastic packaging is disposable. As a consequence, significant amounts of waste are generated, entering the environment, and undergoing degradation processes. They can occur under the influence of mechanical forces, temperature, light, chemical, and biological factors. These factors can present synergistic or antagonistic effects. As a result of their action, microplastics are formed, which can undergo further fragmentation and decomposition into small-molecule compounds. During the degradation process, various additives used at the plastics' processing stage can also be released. Both microplastics and additives can negatively affect human and animal health. Determination of the negative consequences of microplastics on the environment and health is not possible without knowing the course of degradation processes of packaging waste and their products. In this article, we present the sources of microplastics, the causes and places of their formation, the transport of such particles, the degradation of plastics most often used in the production of packaging for food storage, the factors affecting the said process, and its effects.

Theoretical insights into the uptake of sulfonamides onto phospholipid bilayers: Mechanisms, interaction and toxicity evaluation

Sulfonamides (SAs) are now recognized as the main emerging environmental pollutants in aquatic environments. Although the bioaccumulation capacities of SAs have been confirmed, the pathway for the penetration of the SAs into lipid bilayer has been not fully understood. In this study, the bioaccumulation mechanism of four typical SAs onto the dipalmitoyl phosphatidylcholine (DPPC) lipid bilayer and their effects on the properties of DPPC bilayer were employed and evaluated respectively by using molecular dynamics simulations. Results show that from the viewpoint of thermodynamics, it is favorable for these SAs partitioning to DPPC bilayer. The accommodation of four SAs onto the lipid membrane needs to undergo several processes, which include the contact stage, transformation stage, and absorption stage. Besides, the sulfamethoxazole (SMX) and sulfamethazine (SMZ) show a strong preference for the DPPC phase rather than the interface region while the sulfadiazine (SDZ) and sulfametoxydiazine (SMD) have similar tendencies in the interface region and DPPC phase. Furthermore, the cytotoxicity of SAs is reflected in their ability to affect the electrostatic potential of the membrane and to reduce the thickness of phospholipid bilayers. This molecular-level study provided an insightful understanding of the toxicity and bioaccumulation of SAs.

Hormetic dose-response of halogenated organic pollutants on Microcystis aeruginosa: Joint toxic action and mechanism

Quinolones (QNs), dechloranes (DECs), and chlorinated paraffins (CPs) are three kinds of new halogenated organic pollutants (HOPs), which originate from the use of flame retardants, lubricants and pesticides. Since QNs, DECs, and CPs are frequently detected in waters and sediments, it is necessary to investigate the toxic effects of these HOPs with dwelling phytoplankton, especially for cyanobacteria, to explore their potential hormetic effects and contributions to algal blooms. In the present study, we investigate single and joint toxicity of QNs, DECs and CPs on Microcystis aeruginosa (M. aeruginosa), a cyanobacterium that is frequently implicated with algal blooms. The results indicate single QNs and DECs induce marked hormetic effects on the proliferation of M. aeruginosa but CPs do not. The stimulatory effect of hormesis is linked with accelerated replication of DNA, which is considered to stem from the moderate rise in intracellular reactive oxygen species (ROS). Joint toxicity tests reveal that both QNs & CPs mixtures and DECs & CPs mixtures show hormetic effects on M. aeruginosa, but QNs & DECs mixtures show no hormetic effect. QNs & DECs mixtures exhibit synergistic toxic actions, which may be caused by a sharp rise in intracellular ROS simultaneously produced by the agents. Joint toxic actions of both QNs & CPs, and DECs & CPs shift from addition to antagonism as concentration increases, and this shift may mainly depend on the influence of CPs on cell membrane hydrophobicity of M. aeruginosa. This study provides data and toxic mechanisms for the hormetic phenomenon of single and joint HOPs on M. aeruginosa. The hormetic effects of HOPs may benefit the proliferation of M. aeruginosa in the aquatic environment, aggravating the formation of algal blooms. This study also reflects the important role of hormesis in environmental risk assessment of pollutants.

Effects of Pressurized Aeration on the Biodegradation of Short-Chain Chlorinated Paraffins by Escherichia coli Strain 2

Short-chain chlorinated paraffins (SCCPs) were defined as persistent organic pollutants in 2017, and they can migrate and transform in the environment, accumulate in organisms, and amplify through the food chain. Although they pose a serious threat to environmental safety and human health, there are few papers on their removal. The current SCCP removal methods are expensive, require severe operating conditions, involve time-consuming biological treatment, and have poor removal specificities. Therefore, it is important to seek efficient methods to remove SCCPs. In this paper, a pressurized reactor was introduced, and the removal performance of SCCPs by Escherichia coli strain 2 was investigated. The results indicated that moderate pure oxygen pressurization promoted bacterial growth, but when it exceeded 0.15 MPa, the bacterial growth was severely inhibited. When the concentration of SCCPs was 20 mg/L, the removal rate of SCCPs was 85.61% under 0.15 MPa pure oxygen pressurization for 7 days, which was 25% higher than at atmospheric pressure (68.83%). In contrast, the removal rate was only 69.28% under 0.15 MPa air pressure. As the pressure continued to increase, the removal rate of SCCPs decreased significantly. The total amount of extracellular polymeric substances (EPS) increased significantly upon increasing the pressure, and the amount of tightly bound EPS (TB-EPS) was higher than that of loosely bound EPS (LB-EPS). The pressure mainly promoted the secretion of proteins in LB-EPS. Furthermore, an appropriate pure oxygen pressure of 0.15 MPa improved the dehydrogenase activity. The gas chromatography–mass spectrometry (GC–MS) results indicated that the degradation pathway possibly involved the cleavage of the C–Cl bond in SCCPs, which produced Cl⁻, followed by C–C bond breaking. This process degraded long-chain alkanes into short-chain alkanes. Moreover, the main degradation products detected were 2,4-dimethylheptane (C₉H₂₀), 2,5-dimethylheptane (C₉H₂₀), and 3,3-dimethylhexane (C₈H₁₈).