Movement of synthetic organic compounds in the food web after the introduction of invasive quagga mussels (Dreissena bugensis) in Lake Mead, Nevada and Arizona, USA

Fish Health Altered by Contaminants and Low Water Temperatures Compounded by Prolonged Regional Drought in the Lower Colorado River Basin, USA

The goal of this study was to assess health of male Common Carp (carp, Cyprinus carpio) at four sites with a wide range in environmental organic contaminant (EOC) concentrations and water temperatures in Lake Mead National Recreation Area NV/AZ, US, and the potential influence of regional drought. Histological and reproductive biomarkers were measured in 17-30 carp at four sites and 130 EOCs in water per site were analyzed using passive samplers in 2010. Wide ranges among sites were noted in total EOC concentrations (>10Xs) and water temperature/degree days (10Xs). In 2007/08, total polychlorinated biphenyls (tPCBs) in fish whole bodies from Willow Beach (WB) in the free-flowing Colorado River below Hoover Dam were clearly higher than at the other sites. This was most likely due to longer exposures in colder water (12-14 °C) and fish there having the longest lifespan (up to 54 years) for carp reported in the Colorado River Basin. Calculated estrogenicity in water exceeded long-term, environmentally safe criteria of 0.1-0.4 ng/L by one to three orders of magnitude at all sites except the reference site. Low ecological screening values for four contaminants of emerging concern (CEC) in water were exceeded for one CEC in the reference site, two in WB and Las Vegas Bay and three in the most contaminated site LVW. Fish health biomarkers in WB carp had 25% lower liver glycogen, 10Xs higher testicular pigmented cell aggregates and higher sperm abnormalities than the reference site. Sperm from LVW fish also had significantly higher fragmentation of DNA, lower motility and testis had lower percent of spermatozoa, all of which can impair reproduction. Projections from a 3D water quality model performed for WB showed that EOC concentrations due to prolonged regional drought and reduced water levels could increase as high as 135%. Water temperatures by late 21st century are predicted to rise between 0.7 and 2.1 °C that could increase eutrophication, algal blooms, spread disease and decrease dissolved oxygen over 5%.

Bioaccumulation, trophic transfer and risk assessment of polycyclic musk in marine food webs of the Bohai Sea

Galaxolide (HHCB) and tonalide (AHTN) are dominant musks added to personal care products. However, the accumulate and trophic transfer of SMs through the marine food chain are unclear. In this study, organisms were collected from three bays in Bohai Sea to investigate the bioaccumulation, trophic transfer, and health risk of SMs. The HHCB and AHTN concentrations in the muscles range from 2.75 to 365.40 μg/g lw and 1.04-4.94 μg/g lw, respectively. The median HHCB concentrations in muscles were the highest in Bohai Bay, followed by Laizhou Bay and Liaodong Bay, consistent with the HHCB concentrations in sediments. The different fish tissues from Bohai Bay were analyzed, and the HHCB and AHTN concentrations followed the heart > liver > gill > muscles. The trophic magnification factors (TMF) were lower than 1 and the health risk assessment showed no adverse health effects. The results provide insights into the bioaccumulation and trophic transfer behavior of SMs in marine environments.

Metabolic disturbance and transcriptomic changes induced by methyl triclosan in human hepatocyte L02 cells

PURPOSE

Methyl triclosan (MTCS) is one of the biomethylated by-products of triclosan (TCS). With the increasing use of TCS, the adverse effects of MTCS have attracted extensive attention in recent years. The purpose of this study was to investigate the cytotoxicity of MTCS and to explore the underlining mechanism using human hepatocyte L02 cells as in vitro model.

RESULTS

The cytotoxicity results revealed that MTCS could inhibit cell viability, disturb the ratio of reduced glutathione (GSH) and oxidized glutathione (GSSG), and reduce the mitochondrial membrane potential (MMP) in a dose-dependent manner. In addition, MTCS exposure significantly promoted the cellular metabolic process, including enhanced conversion of glucose to lactic acid, and elevated content of intracellular triglyceride (TG) and total cholesterol (TC). RNA-sequencing and bioinformatics analysis indicated disorder of glucose and lipid metabolism was significantly induced after MTCS exposure. Protein-protein interaction network analysis and node identification suggested that Serine hydroxy methyltransferase 2 (SHMT2), Methylenetetrahydrofolate dehydrogenase 2 (MTHFD2), Asparagine synthetase (ASNS) and Phosphoglycerate dehydrogenase (PHGDH) are potential molecular markers of metabolism imbalance induced by MTCS.

CONCLUSION

These results demonstrated that oxidative stress and metabolism dysregulation might be involved in the cytotoxicity of MTCS in L02 cells.

Global distribution and ecological risk assessment of synthetic musks in the environment

Synthetic musks, as an alternative product of natural musks, are widely used in almost all fragrances of consumer products, such as perfumes, cosmetics and detergents. During the past few decades, the production of synthetic musks has been increasing year by year, subsequently followed by large concern about their adverse effects on ecosystems and human beings. Until now, several studies have reviewed the latest development of analytical methods of synthetic musks in biological samples and cosmetics products, while there is still lack of a systematic analysis of their global distribution in different environmental media. Thus, this review summarizes the occurrence of synthetic musks in the environment including biota around the world and explores their global distribution patterns. The results show that galaxolide (HHCB), tonalide (AHTN), musk xylene (MX) and musk ketone (MK) are generally the most frequently detected synthetic musks in different samples with HHCB and AHTN being predominant. Higher concentrations of HHCB and AHTN are normally found in western countries compared to Asian countries, indicating more consumptions of these musks in western countries. The persistence, bioaccumulation and toxicity (PBT) of synthetic musks (mainly for polycyclic musks and nitro musks) are also discussed. The risk quotients (RQs) of HHCB, AHTN, MX and MK in most waters and sediments are below 0.1, reflecting a low risk to aqueous and sediment-dwelling species. In some sites, e.g., close to STPs, high risks (RQs>1) are characterized. Currently, limited data are available for macrocyclic musks and alicyclic musks in terms of either occurrence or PBT properties. More studies with an expanded scope of chemical type, geographical distribution and (synergic) toxicological effects especially from a long-term point of view are needed.

Environmental fate and trophic transfer of synthetic musk compounds and siloxanes in Geum River, Korea: Compound-specific nitrogen isotope analysis of amino acids for accurate trophic position estimation

Despite the extensive usage of synthetic musk compounds (SMCs) and siloxanes in various personal care products (PCPs), trophic magnification of such chemicals in aquatic environments remains unexplored. In June and September 2020, eleven SMCs and nineteen siloxanes were measured in water, sediments, and biota. Samples were collected from two sites where levels were expected to be influenced by the distance from the wastewater treatment plant (WWTP) in the Geum River, Republic of Korea, were expected. High concentrations of SMCs and siloxanes entered through WWTP were measured in water, sediment, and biota at the both sites and both seasons. The δ¹⁵N of amino acids provided a high-resolution food web and accurate trophic position (TP), which is an important factor for determining the trophic magnification factor (TMF). Among 24 TMFs, 19 of them were <1, ranging 0.7-0.8 for 1,3,4,6,7,8‑hexahydro‑4,6,6,7,8,8‑hexamethyl‑cyclopenta‑γ‑2‑benzopyran (HHCB), 0.6-0.8 for 6-Acetyl-1,1,2,4,4,7-hexamethyltetralin (AHTN), 0.7-0.8 for 4-tert-Butyl-3,5-dinitro-2,6-dimethylacetophenone (MK), 0.7-0.9 for octamethylcyclotetrasiloxane (D4), 0.1-0.4 for decamethylcyclopentasiloxane (D5), and 0.04-0.8 for dodecamethylcyclohexasiloxane (D6), and the remaining ones including HHCB, AHTN, MK, and D4 showed values close to 1 or slightly higher (TMF range: 1.0-2.3) indicating no or a little trophic magnification. The TMFs of these compounds were constant across sites and seasons. The TMF values of PCPs might be affected by species specificity and food web structure rather than by chemical properties such as log K_ow, which describes a wide range of TMF values in various environments. This study presents valuable implications for assessing risk and managing environmental fate and trophic transfer of SMCs and siloxanes in freshwater environments.

Hormesis Effect of Methyl Triclosan on Cell Proliferation and Migration in Human Hepatocyte L02 Cells

Methyl triclosan (mTCS) is a methylated derivative of triclosan (TCS), which is extensively used as an antimicrobial component of various nursing products and disinfectants. Current research studies of mTCS mainly focused on the environmental persistence and bioaccumulation potential. Knowledge regarding the toxicity and carcinogenicity of mTCS is limited until now. In this study, the human hepatocyte L02 cells were used to investigate the cellular effects of mTCS under different concentrations (0.1-60 μM). The hormesis effect was observed where a low dose of mTCS (≤5 μM) exposure stimulated the cell proliferation ability, while high-dose exposure (≥20 μM) inhibited cell proliferation. In the same time, low doses of mTCS (0.5 and 1 μM) induced enhanced anchorage-independent proliferation ability and cell migration ability, indicating a positive effect on malignant transformation in L02 cells. Moreover, reactive oxygen species productions were significantly increased after mTCS exposure (≥1 μM), as compared with the control group. Furthermore, expressions of tumor-related genes, mouse double minute 2 (MDM2), matrix metalloproteinase 9 (MMP9), and proliferating cell nuclear antigen (PCNA), and proto-oncogene MYC (c-Myc), Jun, and FosB were significantly upregulated, while no significant changes were observed on expressions of apoptosis-related and cell cycle-related genes in L02 cells after exposure of low-dose mTCS. In conclusion, these results indicated that a low dose of mTCS had a hormesis effect in L02 cells on cell proliferation and malignant transformation in vitro, which might be mediated through oxidative stress response.