Existing mutagenicity tests for metazoans lack the direct observation of enhanced germline mutation rates after exposure to anthropogenic substances, therefore being inefficient. Cadmium (Cd) is a metal described as a mutagen in mammalian cells and listed as a group 1 carcinogenic and mutagenic substance. But Cd mutagenesis mechanism is not yet clear. Therefore, in the present study, we propose a method coupling short-term mutation accumulation (MA) lines with subsequent whole genome sequencing (WGS) and a dedicated data analysis pipeline to investigate if chronic Cd exposure on Chironomus riparius can alter the rate at which de novo point mutations appear. Results show that Cd exposure did not affect the basal germline mutation rate nor the mutational spectrum in C. riparius, thereby arguing that exposed organisms might experience a range of other toxic effects before any mutagenic effect may occur. We show that it is possible to establish a practical and easily implemented pipeline to rapidly detect germ cell mutagens in a metazoan test organism. Furthermore, our data implicate that it is questionable to transfer mutagenicity assessments based on in vitro methods to complex metazoans.

Disinfection is considered as a vital step to ensure the supply of clean and safe drinking water. Various approaches are adopted for this purpose; however, chlorination is highly preferred all over the world. This method is opted owing to its several advantages. However, it leads to the formation of certain by-products. These chlorination disinfection by-products (DBPs) are genotoxic, carcinogenic and mutagenic. Still chlorination is being practiced worldwide. Present review gives insights into the occurrence, toxicity and factors affecting the formation of regulated (THMs, HAAs) and emerging DBPs (N-DBPs, HKs, HAs and aromatic DBPs) found in drinking water. Furthermore, remediation techniques used to control DBPs have also been summarized here. Key findings are: (i) concentration of regulated DBPs surpassed the permissible limit in most of the regions, (ii) high chlorine dose, high NOM, more reaction time (up to 3 h) and high temperature (up to 30 °C) enhance the formation of THMs and HAAs, (iii) high pH favors the formation of THMs while low pH is suitable of the formation of HAAs, (iv) high NOM, low temperature, low chlorine dose and moderate pH favors the formation of unstable DBPs (N-DBPs, HKs and HAs), (v) DBPs are toxic not only for humans but for aquatic fauna as well, (vi) membrane technologies, enhanced coagulation and AOPs remove NOM, (vii) adsorption, air stripping and other physical and chemical methods are post-formation approaches (viii) step-wise chlorination is assumed to be an efficient method to reduce DBPs formation without any treatment. Toxicity data revealed that N-DBPs are found to be more toxic than C-DBPs and aromatic DBPs than aliphatic DBPs. In majority of the studies, merely THMs and HAAs have been studied and USEPA has regulated just these two groups. Future studies should focus on emerging DBPs and provide information regarding their regulation.

Excessive nutrient balance is a very crucial issue for environmental hazards. The constant addition of high-amounts of nutrient sources in agricultural production generates negative environmental conditions in Korea and Japan yet to be resolved. Therefore, it is obligatory to comprehend the nutrient (nitrogen (N) and phosphorus (P)) balance that is assessed by the difference between nutrient input and output in the soil surface in Korea and Japan. Among 34 Economic Co-operation and Development (OECD) countries, Korea and Japan had the highest N and P balances and thus both countries are primarily responsible for severe environmental pollution via nutrient release. The cultivable land area in both countries has constantly decreased during 1990–2017 at approximately 20 and 15% in Korea and Japan, respectively. Even N and P use efficiency sharply decreased with increasing N and P balance in both targeted countries. Japanese P balance, Korean N and P balances were decreased after the mid-1990s whereas, Japanese N balance almost unchanged for the last 28 years. Unlike chemical fertilizer input, Korean manure input level significantly increased from 78 kg N ha⁻¹ in 1990 to 157 kg N ha⁻¹ in 2017. Japanese manure input level was higher than that of chemical fertilizer without any big change for the last 28 years. The lion share of high N and P balance in both countries could generate from manure inputs, therefore, the number of livestock and their produced debris need to be used with more cautious for the reduction of national N and P surpluses at a benchmark level. These findings ensure to make a more environment friendly policy that can further reduce nutrient balance as well as improve soil health.

Micro-crustaceans are important grazers that control the algal blooms in eutrophic lakes. However, we know little about how these key species may be affected by long-term exposure to contaminants and when the transgenerational effects are reversible and irreversible. To address this, we investigated the effects of lead (Pb, 100 μg L⁻¹) exposure on morphology and reproduction of Moina dubia for nine consecutive generations (F1–F9) in three treatments: control, Pb, and pPb (M. dubia from Pb-exposed parents returned to the control condition). In F1–F2, Pb did not affect morphology, and reproduction of M. dubia. In all later generations, Pb-exposed M. dubia had a smaller body and shorter antennae than those in control. In F3–F6, pPb-exposed animals showed no differences in body size and antennae compared to the control, suggesting recoverable effects. In F7–F9, the body size and antennae of pPb-exposed animals did not differ compared to Pb-exposed ones, and both were smaller than the control animals, suggesting irreversible effects. Pb exposure reduced the brood size, number of broods and total neonates per female in F3–F9, yet the reproduction could recover in pPb treatment until F7. No recovery of the brood size and number of broods per female was observed in pPb-exposed animals in the F8–F9. Our study suggests that long-term exposure to metals, here Pb, may cause irreversible impairments in morphology and reproduction of tropical urban micro-crustaceans that may lower the top-down control on algal blooms and functioning of eutrophic urban lakes.

The abuse or misuse of antibiotics is directly linked to the emergence of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) in the environment. Most fish farms located on Jeju Island operate a flow-through system that pumps in seawater for fish farming and discharges it back to the ocean. To investigate the amount of ARGs that these fish farm effluents discharge into the marine environment, we conducted a metagenomic-based resistome analysis. We observed higher levels of ARGs in fish farm effluents than in seawater at beach and residential areas. A greater proportion of ARGs was found on plasmid rather than on chromosomal DNA, especially for sulfonamide and phenicol classes. The distribution of ARGs did not differ between summer and winter, but the microbial community did. In addition, fish farm samples contained significantly more opportunistic pathogens (i.e., Vibrio, Photobacterium, Aliivibrio, and Tenacibaculum) and virulence factors than non-fish farm samples. Vibrio was the most frequently identified host of ARGs and virulence factors. The presence of Vibrio in the coastal area has been increasing owing to the recent rise in the temperature of seawater. This study suggests the need for actions to treat or monitor ARGs in the coastal areas where fish farms operating a flow-through system are located.

Contamination status, potential emission sources, environmental fate, and human exposure risk of polybrominated diphenyl ethers (PBDEs) are reviewed for indoor and outdoor dust from Southeast Asian countries, under an international comparison point of view. PBDEs have been widely detected in house, workplace, car, and road dust samples collected from Indonesia, Philippines, Singapore, Thailand, and Vietnam. The highest PBDE levels up to hundreds of μg/g were found in settled dust from some e-waste processing areas in Thailand and Vietnam. Concentrations of PBDEs in house, car, and road dust from this region were generally lower than those reported in China and Western developed countries. BDE-209 was the most predominant congener in almost all analyzed samples, reflecting the widespread application of materials and products treated with commercial deca-BDE mixtures in this region. The market demand and application rate of commercial PBDE mixtures in Southeast Asia were lower than those documented for other regions in the world. As a result, PBDE contamination levels in the environments (e.g., indoor and outdoor dust) and associated risks in these countries were not significantly high. However, more attention should be paid to informal processing activities and management strategies for modern wastes such as e-waste, plastics, and end-of-life vehicles. There exist several knowledge gaps about spatiotemporal trends, potential sources, risk assessment, inventory, management, and legislation regarding PBDEs in dust from this region, which should be filled by additional comprehensive, detailed studies with relevant inter-country/regional monitoring schemes.

Pyriproxyfen is a juvenile hormone analogue insecticide used worldwide. At present, the potential threat of pyriproxyfen to aquatic organism has not been well explored. In this work, the bioaccumulation, metabolic profile and toxicity of pyriproxyfen and its metabolites to zebrafish were studied, and the enantioselectivity of pyriproxyfen and the major chiral metabolites were also determined. Sixteen metabolites of pyriproxyfen in zebrafish were identified. Hydroxylation, ether linkage cleavage and oxidation in phase I metabolism, followed by sulfate and glucuronic acid conjugation. The bioconcentration factors ranged from 1175 to 1246. Hydroxylation metabolites of pyriproxyfen showed enantioselective behavior in zebrafish with enantiomer fractions (EFs) of 4′–OH– pyriproxyfen and 5″–OH– pyriproxyfen ranged from 0.50 to 0.71. Toxicological indexes including acute toxicity, joint toxicity and oxidative stress were tested. Among all the metabolites, 4′–OH– pyriproxyfen was found 2 folds more toxic to zebrafish than pyriproxyfen. (−)-Pyriproxyfen was found 2 folds more toxic than rac- and (+)-pyriproxyfen. Antagonistic effects were found in binary joint toxicity of pyriproxyfen and its hydroxylated metabolites. Pyriproxyfen and its metabolites also showed oxidative stress damage by inhibiting the activity of CAT and SOD and increasing MDA. This work provided deep insight into the metabolism and the potential risks of pyriproxyfen to aquatic organisms.

Potential suppression of fertility due to mobile phone radiation remains a focus of researchers. We conducted meta-analyses on the effects of mobile phone radiation on sperm quality using recent evidence and propose some perspectives on this issue. Using the MEDLINE/PubMed, Embase, WOS, CENTRAL, and ClinicalTrials.gov databases, we retrieved and screened studies published before December 2020 on the effects of mobile phone use/mobile phone RF-EMR on sperm quality. Thirty-nine studies were included. Data quality and general information of the studies were evaluated and recorded. Sperm quality data (density, motility, viability, morphology, and DFI) were compiled for further analyses, and we conducted subgroup, sensitivity, and publication bias analyses. The pooled results of human cross-sectional studies did not support an association of mobile phone use and a decline in sperm quality. Different study areas contributed to the heterogeneity of the studies. In East Europe and West Asia, mobile phone use was correlated with a decline in sperm density and motility. Mobile phone RF-EMR exposure could decrease the motility and viability of mature human sperm in vitro. The pooled results of animal studies showed that mobile phone RF-EMR exposure could suppress sperm motility and viability. Furthermore, it reduced sperm density in mice, in rats older than 10 weeks, and in rats restrained during exposure. Differences regarding age, modeling method, exposure device, and exposure time contributed to the heterogeneity of animal studies. Previous studies have extensively investigated and demonstrated the adverse effects of mobile phone radiation on sperm. In the future, new standardized criteria should be applied to evaluate potential effects of mobile phone RF-EMR dosages. Further sperm-related parameters at the functional and molecular levels as well as changes in biological characteristics of germ cells should be evaluated. Moreover, the impact of mobile phone RF-EMR on individual organs should also be examined.

Polychlorinated biphenyls (PCBs) are one of the most refractory organic environmental pollutants that ubiquitous existence in nature. Due to the polymorphism of their metabolic pathway and corresponding downstream metabolites, PCBs’ toxicities are complicated and need extended investigation. In the present study, we discovered a novel regulatory mechanism of PCB quinone metabolite-driven programmed cell death (PCD), namely, necroptosis. We first confirmed that PCB quinone induces cancerous HeLa and MDA-MB-231 cells necroptosis via the phosphorylation of mixed lineage kinase domain-like MLKL (p-MLKL). Then, we found that PCB quinone-stimulated p-MLKL enhances exosome biogenesis and secretion. Exosome interacts with p-MLKL and releases p-MLKL to the outside of the cell, and ultimately alleviating PCB quinone-induced necroptosis. The inhibition of exosome secretion by GW4869 significantly elevated necroptotic level, indicating the establishment of a short negative feedback loop of MLKL-exosome secretion upon PCB quinone challenge. Since exosome-mediated signaling showed great implications in various human diseases, this work may provide a new mechanism for PCBs-associated toxicity.

The sedimentary history of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) over the past 140 years in a lake sediment core from Huixian karst wetland was reconstructed. The total PAHs and OCPs concentrations ranged from 40.0 to 210 ng g⁻¹ and 0.98 to 31.4 ng g⁻¹, respectively. The vertical distribution of PAHs and OCPs in different stages was great consistent with the history of regional socio-economic development and the usage of OCPs. As the indicators of socio-economic development, gross domestic product (GDP), population, energy consumption, highway mileage, and private vehicles correlated with the PAHs concentrations, indicating the impact of human activities on PAHs levels. The PAHs and OCPs concentrations were also affected by environmental changes in the wetland, as reconstructed by total organic carbon (TOC), sand, silt, clay, quartz, and calcite in sediments. Redundancy analysis (RDA) results showed TOC was the dominant factor to explain the concentrations of PAHs and OCPs with the explanation of 86.7% and 43.5%, respectively. In addition, TOC content had significantly positive correlation with PAHs (0.96, p < 0.01) and OCPs (0.78, p < 0.01). In particular, the significantly positive correlation (p < 0.05) between calcite and PAHs and OCPs inferred that karstification might play an important role in the migration of PAHs and OCPs in the karst area. Therefore, the lake in Huixian wetland tended to be a sink more than a source of PAHs and OCPs influenced by the increasing TOC content and karstification under climate warming.