Indoor and outdoor fine particulate matter (PM2.5) are both leading risk factors for death and disease, but making indoor measurements is often infeasible for large study populations.We developed models to predict indoor PM2.5 concentrations for pregnant women who were part of a randomized controlled trial of portable air cleaners in Ulaanbaatar, Mongolia. We used multiple linear regression (MLR) and random forest regression (RFR) to model indoor PM2.5 concentrations with 447 independent 7-day PM2.5 measurements and 87 potential predictor variables obtained from outdoor monitoring data, questionnaires, home assessments, and geographic data sets. We also developed blended models that combined the MLR and RFR approaches. All models were evaluated in a 10-fold cross-validation.The predictors in the MLR model were season, outdoor PM2.5 concentration, the number of air cleaners deployed, and the density of gers (traditional felt-lined yurts) surrounding the apartments. MLR and RFR had similar performance in cross-validation (R2 = 50.2%, R2 = 48.9% respectively). The blended MLR model that included RFR predictions had the best performance (cross validation R2 = 81.5%). Intervention status alone explained only 6.0% of the variation in indoor PM2.5 concentrations.We predicted a moderate amount of variation in indoor PM2.5 concentrations using easily obtained predictor variables and the models explained substantially more variation than intervention status alone. While RFR shows promise for modelling indoor concentrations, our results highlight the importance of out-of-sample validation when evaluating model performance. We also demonstrate the improved performance of blended MLR/RFR models in predicting indoor air pollution.

Climate change and pharmaceuticals contamination constitute two of the most relevant stressors on the aquatic ecosystems, however, there is a huge lack of information regarding the interactive effects of both stressors. For that, a mesocosm experiment was implemented where adult zebrafish were exposed to combined temperature and the progestin levonorgestrel (LNG) for 21 days. Considering that the liver is one of the organs where there is a greater metabolization and accumulation of toxicants, the main objective of this work was to assess the effects of both stressors on the female zebrafish hepatocytes morphology and functioning, through stereological and immunohistochemical techniques.Our results revealed an increase of coefficient of variation of the number distribution of hepatocytes volume (CVN(υ)) for individuals exposed to LNG, which denotes an increase of the hepatocytes size variability and is suggestive of functional impacts. This was corroborated by the signs of increased glycogen content with the exposure to increased LNG concentrations and temperature, indicating modified hepatocyte glycogen metabolism. Such disturbances can be considered indicators that the fish had to deal with impacts caused by the stress factors.Regarding the immunoreactivity, from the four proteins selected (catalase, CYP1A, HSP90 and Vtg), just in two of them (catalase and Vtg) were observed some responses to both stressors. For catalase there was a hormetic response, in which exposure to lower LNG concentrations caused a significant higher positive immunostaining than under higher LNG concentrations. While, for Vtg, significant effects of temperature and LNG existed, in which a decline in Vtg immunostaining was observed with exposure to higher temperature and lower LNG concentrations. These results should be seen as a warning sign about fine impacts of multiple stressors, such as temperature and progestogens, on the structure and functioning of zebrafish liver and potentially in other aquatic organisms, and on their health implications.

Microplastics are hardly biodegradable and thus accumulate rather than decompose in the environment. Due to sedimentation processes, meiobenthic fauna is exposed to microplastics. Within the meiofauna, nematodes are a very abundant taxon and occupy an important position in benthic food webs by connecting lower and higher trophic levels. However, the key determinants of the uptake of microplastics by freshwater nematodes are still unknown. To investigate the bioaccessibility of microplastics for nematodes, we performed single- and multi-species ingestion experiments in which the ability of seven nematode species (six bacterial and one fungal feeder), diverse in their buccal cavity morphology (1.3–10.5 μm), to ingest fluorescence-labelled polystyrene (PS) beads along with their natural diet was examined. Applied beads sizes (0.5, 1.0, 3.0 and 6.0 μm), exposure time (4, 24 and 72 h) and concentration (3 × 10⁶ PS beads ml⁻¹ and 10⁷ PS beads ml⁻¹) were varied. Ingested beads were localized and quantified via fluorescence microscopy in the nematodes. In contrast to fungal-feeding nematode species with a stylet, bacterial-feeding species ingested 0.5- and 1.0-μm PS beads with up to 249 and 255 beads after 24 h, respectively. Microplastics ≥0.5 μm could only be ingested and transported into the gastrointestinal tract, if the buccal cavities were considerably (>1.3 times) larger than the beads. At concentrations of 10⁷ PS beads ml⁻¹ ingestion rates were influenced by exposure time and PS bead concentration. In case of a known microplastic size distribution in the environment, predictions on the potential ingestion for nematode communities can be made based on the feeding type composition and the size of their buccal cavities.

The pollution of antibiotics and antibiotic resistance genes (ARGs) has been highlighted on a global scale because of their serious threats to the environment and human health. Typical urban water in cities with high population density are ideal mediums for the acquisition and spread of antibiotics and ARGs. The pollution level of a broad range of antibiotics and ARGs in hospital wastewater, groundwater and the Wenyu River, and their fates through three sewage treatment plants (STPs) were investigated in this study. The concentrations of the 11 detected antibiotics ranged from not detected (ND)-16800 ng L⁻¹ in diverse water samples from Beijing, and fluoroquinolones were detected at the highest concentration, especially in the hospital samples. The maximum concentrations of antibiotics in STPs and hospital were 1–3 orders of magnitude higher than those in the surface water from Wenyu River and groundwater. Good removal efficiencies by treatment processes were observed for tetracyclines and quinolones, and low removal efficiencies were observed for sulfonamides and macrolides. These results also revealed that the sulfonamide resistance genes (sul1, sul2) and macrolide resistance genes (ermB) were detected at the highest relative abundances (7.11 × 10⁻²-1.18 × 10⁻¹) in the water bodies of Beijing. It was worth noting that sul1 abundance was the highest in groundwater samples. The relative abundance of most ARGs in STPs exhibited a declining trend in the order of influent > secondary effluents > effluent. However, the relative abundance of sul 1, sul 2 and tetC in the effluent was higher than those in the influent. The incomplete removal of antibiotics and ARGs in STPs poses a serious threat to the receiving rivers, and affects ecosystem security. Overall, our findings provide favorable support for a further investigation of the spread and risk of antibiotics and ARGs from diverse sources (e.g., STPs and hospitals) to the aquatic environment.

As a widely used organotin acaricide nowadays, azocyclotin (ACT) could induce thyroidal endocrine disruption in fishes and amphibians, but its dominant disrupting mode remains unknown. In this study, zebrafish were firstly exposed to ACT (0.18–0.36 ng/mL) from 2 hpf (hours post fertilization) to 30 dpf (days post fertilization), and a series of developmental toxicological endpoints and thyroid hormones were measured. Result showed that no developmental toxicity to zebrafish was found in 0.18 and 0.24 ng/mL groups except decreased body weight (30 dpf, 0.24 ng/mL). However, exposed to 0.36 ng/mL ACT led to reductions in heartbeat (48 hpf), hatching rate (72 hpf) and bodyweight (30 dpf). General tendencies of decreases in free T3 but increases in free T4 and reductions in ratio of free T3/T4 were also found, inferring that type II deiodinase (Dio2) was repressed. This inference was confirmed by Western analysis that Dio2 expression reduced by 42.7% after 0.36 ng/mL ACT treatment. Moreover, RNA-Seq analysis implied that exposed to 0.36 ng/mL ACT altered the genome-wide gene expression profiles of zebrafish. Totally 5660 genes (involving 3154 down-regulated and 2596 up-regulated genes) were differentially expressed, and 13 deferentially expressed genes including down-regulated dio2 were significantly enriched in thyroid hormone signaling pathway. Subsequently, an in vitro thyroid receptor-reporter gene assay using GH3 cells was performed to further explore the potential disrupting mechanism. Result showed that luciferase activity slightly increased after exposure to ACT alone or ACT combined with low level T3, but was suppressed when combined with high level T3. It indicted there probably existed a competitive relationship in some extent between ACT and T3 in vivo. Overall, the present study provided preliminary evidences that long-term exposure to trace ACT repressed Dio2 expression, declined T3 and then activated thyroid receptor-mediated signaling, thereby leading to integrated thyroid endocrine disruption in zebrafish larvae.

Excessive use of nitrogenous fertilizers and their improper management in agriculture causes nitrate contamination of surface and groundwater resources. This study was conducted along the seasonally flooded alluvial agricultural area of Indus River Basin to determine the spatial and temporal dynamics of nitrate concentrations in the groundwater along the river. Total of 112 samples were collected from shallow (30–40 ft) and deep groundwater (120–150 ft) wells at seven sites, 25 km apart from each other and covered an area of 170 km along the river, during four sampling campaigns between October 2016 to May 2017 i.e. in start, mid and end of dry season. The study period covered the whole agricultural cycle including the wet summer season with no agricultural activities under flooding and the sampling sites were always less than 2 km from the river bank. Nitrate concentrations of shallow wells were 15–54 and 20–45 mg L⁻¹ during the start and middle of dry season, respectively. However, at the end of the dry season, the highest nitrate concentrations of 35–75 mg L⁻¹ were recorded and 70% of these samples contained nitrate concentrations above the permissible limit 50 mg L⁻¹. Similar seasonal patterns of nitrate concentrations were observed in deep wells, however, δ¹⁸O data suggested lower recharge in deep well than shallow wells. The results illustrated that high nitrate concentrations in shallow wells were associated with high δ¹⁸O values indicating that the quantity of evaporated water infiltrated from the floodplain, possibly from distribution channels, along with the nitrate polluting shallow wells more than the deep wells. At the end of the dry season, nitrate concentrations exceeded the permissible limits in both shallow and deep wells, which possibly happened due to the horizontal movement of groundwater along with the nitrate mixing during vertical seepage of river water to the aquifers.

The Deception Island, located in Maritime Antarctica, is a volcanic island with geothermal activity and one of the most visited by tourists. However, the extent of the anthropogenic impact remains largely unknown and the factors shaping the resistance/tolerance mechanisms in the microbiomes from Whalers Bay ecosystems have never been investigated. In this context, this study aimed to reveal the resistome profiles of Whalers Bay sediments and correlate them with environmental factors. Samples were collected at four sites during the summer 2014/2015 along a transect of 27.5 m in the Whalers Bay sediments. DNA isolated from sediment samples was sequenced using the Illumina HiSeq platform. Bioinformatic analyses allowed the assembly of contigs and scaffolds, prediction of ORFs, and taxonomic and functional annotation using NCBI RefSeq database and KEGG orthology, respectively. Microorganisms belonging to the genera Psychrobacter, Flavobacterium and Polaromonas were shown to dominate all sites, representing 60% of taxonomic annotation. Arsenic (As), copper (Cu) and iron (Fe) were the most abundant metal resistance/tolerance types found in the microbiomes. Beta-lactam was the most common class related to antibiotics resistance/tolerance, corroborating with previous environmental resistome studies. The acridine class was the most abundant amongst the biocide resistance/tolerances, related to antiseptic compounds. Results gathered in this study reveal a repertoire of resistance/tolerance classes to antibiotics and biocides unusually found in Antarctica. However, given the volcanic nature (heavy metals-rich region) of Deception Island soils, this putative impact must be viewed with caution.

As one of the most cost-effective and sustainable methods for contaminants' removal, sequestration and/or detoxification, phytoremediation has already captured comprehensive attention worldwide. Nevertheless, the accurate effects of various spatial pattern in enhancing phytoremediation efficiency is not yet clear, especially for the polluted mining areas. This study designed nine planting patterns (monocropping, double intercropping and triple intercropping) of three indigenous plant species (Setaria viridis (L.), Echinochloa crus-galli (L.) and Phragmites australis (Cav.) Trin. ex Steud.) to further explore the effects of plants spatial pattern on phytoremediation efficiency. Considering the uncertainties of the residual contaminants' concentration (RCC) caused by soil anisotropy, permeability and land types, the interval transformation was introduced into the plant uptake model to simulate the remediation efficiency. Then multi-criteria decision analysis (MCDA) were applied to optimal the planting patterns, with the help of criteria of (a) the amount of heavy metal absorption; (b) the concentration of residual contaminant in soil; (c) root tolerance of heavy metals; (d) the total investment cost. Results showed that (1) the highest concentrations of Zn, Cd, and Pb of the polluted area were 7320.02, 14.30, 1650.51 mg kg⁻¹ (2) During the 180 days simulation, the highest RMSE of residue trace metals in soil are 3.02(Zn), 2.67(Pb), 2.89(Cd), respectively. (3) The result of IMCDA shows that the planting patterns of Setaria viridis, Echinochloa crus-galli and Phragmites australis in alternative a9 (269 mg kg⁻¹ year⁻¹) had the highest absorption rate of heavy metals compared with a7 (235 mg kg⁻¹ year⁻¹) and a2 (240 mg kg⁻¹ year⁻¹). After 20 years of remediation, the simulated RCC in a9 is far below the national standard, and the root toxicity is 0.12 (EC ≤ EC₂₀). In general, the optimal alternative derived from interval residual contaminant concentration can effectively express the dynamic of contaminant distribution and then can be effectively employed to evaluate the sustainable remediation methods.

In the article the results of major and trace elements investigation in freshwater lakes of Vecherny Oasis (Enderby Land, East Antarctica) are considered. Water sampling was carried out during seasonal Belarusian Antarctic expeditions in 2011–2017. Totally 22 water samples from four lakes, three temporal ponds and one water course were collected for major and trace elements determination. The total concentrations of Ag, Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Na, Mg, Mn, Mo, Ni, Pb, Sb, Se, Th, Tl, V, W, Zn in all samples as well as more than 40 additional trace elements in 3 samples from lakes were determined using ICP-MS method.It is shown that increase of heavy metals concentration (Cd, Pb, Zn, Sb, Co, Ni, Se, Mn) and As in the lakes compared to temporary ponds can be explained by anthropogenic impact including previous human activity in the oasis in late 1970th – early 1990th. The maximum concentrations of a number of technophilic elements (Pb, Mo, Mn, V, Sb, Zn) in Lake Nizhneye are possibly connected with the its lowest hypsometric location in catchment and the drainage of the territory impacted by past and present human activity.

Environmental reservoirs of antibiotic resistance (AR) are a growing concern that are gathering more attention as potential sources for human infection. Carbapenem-resistant Enterobacteriaceae (CRE) are extremely dangerous, as carbapenems are often drugs of last resort that are used to treat multi-drug resistant infections. Among the genes capable of conferring carbapenem resistance to bacteria, the most transferrable are those that produce carbapenemase, an enzyme that hydrolyzes carbapenems and other β-lactam antibiotics. The goal of this review was to comprehensively identify global environmental reservoirs of carbapenemase-producing genes, as well as identify potential routes of transmission to humans. The genes of interest were Klebsiella pneumoniae carbapenemase (KPC), New Delhi Metallo-β-lactamase (NDM), Oxacillinase-48-type carbapenemases (OXA-48), and Verona Integron-Mediated Metallo-β-lactamase (VIM). Carbapenemase genes have been reported in the environment on almost every continent. Hospital and municipal wastewater, drinking water, natural waterways, sediments, recreational waters, companion animals, wildlife, agricultural environments, food animals, and retail food products were identified as current reservoirs of carbapenemase-producing bacteria and genes. Humans have been recorded as carrying CRE, without recent admittance to a hospital or long-term care facility in France, Egypt, and China. CRE infections from the environment have been reported in patients in Montpellier, France and Cairo, Egypt. This review demonstrates the need for 1) comprehensive monitoring of AR not only in waterways, but also other types of environmental matrices, such as aerosol, dusts, periphyton, and surfaces in indoor environments; and 2) action to reduce the prevalence and mitigate the effects of these potentially deadly resistance genes. In order to develop an accurate quantitative model for environmental dimensions of AR, longitudinal sampling and quantification of AR genes and bacteria are needed, using a One Health approach.