Concentrations and accumulation rates of polychlorinated biphenyls in soil along an urban-rural gradient in Shanghai

Exposure to polychlorinated biphenyls selectively dysregulates endothelial circadian clock and endothelial toxicity

Polychlorinated biphenyls (PCBs) are lipophilic and persistent environmental toxicants, which pose health threats to the exposed population. Among several organs and cell types, vascular tissue and endothelial cells are especially prone to PCB-induced toxicity. Exposure to PCBs can exert detrimental impacts on biological pathways, expression of transcription factors, and tight junction proteins that are integral to the functionality of endothelial cells. Because biological and cellular processes are tightly regulated by circadian rhythms, and disruption of the circadian system may cause several diseases, we evaluated if exposure to PCBs can alter the expression of the major endothelial circadian regulators. In addition, we studied if dysregulation of circadian rhythms by silencing the brain and muscle ARNT-like 1 (Bmal1) gene can contribute to alterations of brain endothelial cells in response to PCB treatment. We demonstrated that diminished expression of Bmal1 enhances PCB-induced dysregulation of tight junction complexes, such as the expression of occludin, JAM-2, ZO-1, and ZO-2 especially at pathologically relevant longer PCB exposure times. Overall, the obtained results imply that dysregulation of the circadian clock is involved in endothelial toxicity of PCBs. The findings provide new insights for toxicological studies focused on the interactions between environmental pollutants and regulation of circadian rhythms.

A practice study of land and water comprehensive remediation in urban-rural fringe-with Sichuan River Shaanxi Province, Northwest China, as an example

Urban-rural fringe area (URFa) is an active and expansive region, and its environment is complex and frangible. Previous studies have focused on the landscape spatial pattern changes, the spatial-temporal variability of soil pollutants and the land management and policy issues, etc., but it is lack of the practice study of land and water comprehensive remediation in URFa. This article is taking the Sichuan River, a typical URFa, as an example. Based on field investigation and lab tests, the main characteristic form of the URFa and land and water comprehensive remediation measures are summarized in this paper. The results show that it is feasible to turn wasteland, low-efficiency land, and old deserted beach into farm land, residential land, and ecological land by comprehensive land improvement. For the farm land reconstruction, the texture is an important indicator. The content of soil organic matter (SOM), carbon, nitrogen, and phosphorus has increased after remediation. For the SOM, 58.3% are more than 10.0 g·kg^-1, and 79.2% are more than 8.0 g·kg^-1. For the frequent dry-off and polluted low flow river channels in URFa, the river bottom consolidation and water purification is the important measures. The water quality meets IV standard of the "Environmental Quality Standards for Surface Water" (GB3838-2002) (State EPA of China, 2002) by pollution treatment after remediation, and water volume keeps balance. The findings of this study are expected to provide support for better construction practices in arid and semiarid area in China and for the improvement of the ecological environment in URFa.

Simulation experiment on OH-PCB being ingested through daily diet: Accumulation, transformation and distribution of hydroxylated-2, 2', 4, 5, 5'-pentachlorobiphenyl (OH-PCB101) in mice

Animals exposure to polychlorinated biphenyls (PCBs) may result in retention of hydroxylated PCBs (OH-PCBs). OH-PCBs can be accumulated in animals, including humans, through the transmission of food chain. However, there are few studies on the accumulation and metabolism of OH-PCBs exposed to the body through daily diet. Therefore, this study was conducted to investigate the fate of OH-PCBs after being ingested through dietary intake. By adding 3-OH-PCB101 and 4-OH-PCB101 to the edible tissue of crucian carp, which were used as raw materials to prepare mouse feed, with an exposure concentration of 2.5 μg/kg ww. The exposure experiment lasted for a total of 80 days. The blood, feces and 11 tissues of mice at different times were analyzed qualitatively and quantitatively. It was found that major OH-PCB101 were accumulated in intestine or excreted with feces. A small part was accumulated in heart, lung and spleen. For the first time that the conversion from OH-PCB101 to PCB101 in mice was discovered, which shows from another perspective that persistent organic pollutants are difficult to be completely degraded in the environment. 4-MeO-PCB101, 3-MeSO₂-PCB101, and 4-MeSO₂-PCB101 were also found in various tissues. The results of this study show that after OH-PCBs accumulated in animals re-enter the organism through the food chain, they can be metabolized again and may be reversely transformed into the parent compounds. The present research shed new light on simulating the metabolic transformation process of OH-PCBs exposed to mammals through ingestion of fish. Available data show that second-generation persistent organic pollutants in the environment still need to be continuously concerned.