Single and combined potential of polystyrene microparticles and fluoranthene in the induction of DNA damage in haemocytes of Mediterranean mussel (Mytilus galloprovincialis).

In this study, the possible 'vector effect' within the exposure of Mediterranean mussels (Mytilus galloprovincialis) to polystyrene microplastics with adsorbed fluoranthene was investigated by applying the multibiomarker approach. The major focus was placed on genotoxicological endpoints as to our knowledge there are no literature data on the genotoxicity of polystyrene microparticles alone or with adsorbed fluoranthene in the selected experimental organisms. DNA damage was assessed in haemocytes by comet assay and micronucleus test. For the assessment of neurotoxicity, acetylcholinesterase activity was measured in gills. Glutathione S-transferase was assessed in gills and hepatopancreas since these enzymes are induced for biotransformation and excretion of lipophilic compounds such as hydrocarbons. Finally, differences in physiological response within the exposure to polystyrene particles, fluoranthene, or particles with adsorbed fluoranthene were assessed by the variation of heart rate patterns studied by the noninvasive laser fibre-optic method. The uniform response of individual biomarkers within the exposure groups was not recorded. There was no clear pattern in variation of acetylcholinesterase or glutathione S-transferase activity which could be attributed to the treatment. Exposure to polystyrene increased DNA damage which was detected by the comet assay but was not confirmed by micronucleus formation. Data of genotoxicity assays indicated differential responses among the groups exposed to fluoranthene alone and fluoranthene adsorbed to polystyrene. Change in the heart rate patterns within the studied groups supports the concept of the Trojan horse effect within the exposure to polystyrene particles with adsorbed fluoranthene.

Wastewater-based epidemiology in countries with poor wastewater treatment - Epidemiological indicator function of SARS-CoV-2 RNA in surface waters.

Wastewater-based epidemiology (WBE) surveillance of COVID-19 and other future outbreaks is a challenge for developing countries as most households are not connected to a sewerage system. In December 2019, SARS-CoV-2 RNA was detected in the Danube River at a site severely affected by wastewaters from Belgrade. Rivers are much more complex systems than wastewater systems, and efforts are needed to address all the factors influencing the adoption of WBE as an alternative to targeting raw wastewater. Our objective was to provide a more detailed insight into the potential of SARS-CoV-2 surveillance in Serbian surface waters for epidemiological purposes. Water samples were collected at 12 sites along the Sava and Danube rivers in Belgrade during the fourth COVID-19 wave in Serbia that started in late February 2021. RNA was concentrated using Amicon Ultra-15 centrifugal filters and quantified using RT-qPCR with primer sets targeting nucleocapsid (N1 and N2) and envelope (E) protein genes. Microbiological (faecal indicator bacteria and human and animal genetic faecal source tracking markers), epidemiological, physicochemical and hydromorphological parameters were analysed in parallel. From 44 samples, SARS-CoV-2 RNA was detected in 31, but only at 4 concentrations above the level of quantification (ranging from 8.47 × 103 to 2.07 × 104 gc/L). The results indicated that surveillance of SARS-CoV-2 RNA in surface waters as ultimate recipients could be used as an epidemiological early-warning tool in countries lacking wastewater treatment and proper sewerage infrastructure. The performance of the applied approach, including advanced sampling site characterization to trace and identify sites with significant raw sewage influence from human populations, could be further improved by adaptation of the methodology for processing higher volumes of samples and enrichment factors, which should provide the quantitative instead of qualitative data needed for WBE.

Genotoxicity of fluoride subacute exposure in rats and selenium intervention.

The aims of this study were to: (i) examine the toxic effects of sodium fluoride (NaF) in blood, liver, spleen, and brain cells of Wistar rats after the subacute exposure; (ii) explore the potential protective properties of selenium (Se) against fluoride toxicity after the simultaneous administration. Twenty male Wistar rats, eight weeks old, weighing approximately 140-190 g, were divided into four experimental groups (n = 5) as follows: I control-tap water; II NaF 150 ppm; III NaF 150 ppm and Se 1.5 mg/L; IV Se 1.5 mg/L, and had available water with solutions ad libitum for 28 days. DNA damage detected by comet assay was confirmed in the liver, spleen, and brain cells, but not in blood. Selenium supplementation together with NaF decreased DNA damage in liver and spleen cells. According to the histological findings, no changes were observed in spleen and brain tissues after NaF administration. Unlike the observed Se protective effect on the DNA level, no significant reduction of liver tissue injury was observed after the NaF and Se treatment, resulting in mild inflammation. Data of this study suggest that DNA damage after NaF subacute exposure at moderately high concentration was reduced in liver and spleen cells due to Se supplementation, but a similar change was not seen in the brain.

Selection of assay, organism, and approach in biomonitoring significantly affects the evaluation of genotoxic potential in aquatic environments.

In this study, few different evaluation concepts were used for the assessment of genotoxic potential at the stretch of the Danube River identified as a significant hotspot of pollution originated through the untreated wastewaters. Three sites were chosen: one site upstream of the wastewater outlet in Novi Sad (Serbia), one at the outlet of wastewaters, and one site few kilometer downstream. Ex situ approach comprised prokaryotic SOS/umuC test on Salmonella typhimurium TA1535/pSK1005 and comet assay on human hepatoma cell line (HepG2). In situ approach was based on the active monitoring (cage approach) using freshwater mussels Sinanodonta woodiana and fish Cyprinus carpio. The comet and micronucleus assays were selected for evaluation of DNA damage in mussel haemocytes and fish blood cells. Within the ex situ part of the study, our results indicated that the eukaryotic model system is more sensitive compared to the prokaryotic one. In situ bioassays are recommended for obtaining a better insight into ecosystem status and in the case of our study the complete insight of genotoxic pressure. However, the choice of animals as bioindicators also has a significant impact on the quality of the obtained information. Differential response between fish and mussels was observed at the highly polluted site suggesting possible involvement of additional protective mechanism such as valve closure in mussels.