Because of its analgesic properties, acetaminophen (AAP) is widely used to relieve headache. AAP is generally considered safe for humans, but its effects on aquatic organisms are not well known. Here, we have hypothesis that effects of AAP on aquatic organisms would be environmental temperature dependent, because their physiological function depend on the temperature. To test this hypothesis, we used medaka (Oryzias latipes) as a model, because they can live at a wide range of temperatures (0–40 °C). We exposed medaka larvae to 0 (control), 50, or 150 mg/L of AAP at 15, 25 (optimal temperature), or 30 °C for 4 days. Egg yolk absorption was accelerated with raising temperature at any AAP dose. AAP exposure did not have biologically significant effects on survival ratio and body length of larvae at any tested temperature or dose, but heart rate decreased as the dose of AAP and environmental temperature increased. In addition, as the temperature increased, amount of ATP in individual larvae increased in control group, but decreased in AAP exposed group. Subsequently, exposure to 150 mg/L of AAP at 30 °C decreased the number of red blood cells in the gills; we used 150 mg/L of AAP in subsequent hematological and histological analyses. Hematological analysis showed that rising temperature increased the proportion of morphologically abnormal red blood cells in AAP-exposed larvae, suggesting that AAP induced anemia-like signs in larvae. Histological observation of the kidney, which is a hematopoietic organ in fish, revealed no abnormalities. However, in the liver, which is responsible for drug metabolism, the proportion of vacuoles increased with increasing temperature. Although the exposure concentration we tested was higher than environmentally relevant concentrations, our data indicated that rising temperature enhances the toxicity of AAP to medaka larvae, suggesting an ecological risk of AAP due to global warming.

Permeable reactive bio-barriers (Bio-PRBs) are a new and developing technique for in situ remediation of groundwater contamination. Some remediation technologies have often been impeded by insufficient understanding of contaminant transport and transformation in the subsurface environment. Therefore, advanced knowledge in contaminant transport and reactions in Bio-PRBs will be crucial to the successful practical application of this technique. A two-dimensional reaction model C1 was developed for predicting the multi-path chain kinetic reaction of 1,1,1-trichloroethane (1,1,1-TCA) in Bio-PRBs. This study demonstrates that model C1 is able to predict the 1,1,1-TCA breakthrough time and rapidly evaluate the Bio-PRBs retardation performance. The results show that microbial growth and immobilization are the key factors that affect the retardation and remediation performance of Bio-PRBs. The free growth of microorganisms had significant negative effects on hydraulic conductivity (K) in the zero-valent iron (ZVI) region of free microorganism Bio-PRBs (FM-PRBs). The total head loss in the FM-PRB was 9.0 cm, which was significantly greater than the head loss (6.5 cm) of immobilized microorganism Bio-PRBs (IM-PRBs). Compared to ZVI-PRBs and FM-PRBs, the numerical simulation results reveal that microbial immobilization significantly improves the remediation performance of IM-PRBs by 550.9% and 32.7%, respectively. The dual effect of microorganisms leads to significant differences in the 1,1,1-TCA and daughter products (1,1-dichloroethane, 1,1-dichloroethene, chloroethane and vinyl chloride) contaminant-plume evolution between FM-PRBs and IM-PRBs. In addition, model C1 can be utilized to design standard Bio-PRBs for real site of 1,1,1-TCA contanminated groundwater. To meet the safety standard of groundwater as potable water, the width of IM-PRBs needs to be increased by 24 cm. However, in FM-PRBs, the width needs to be increased by 42 cm. Therefore, IM-PRBs save costs significantly. This work has successfully used a model to optimize Bio-PRBs and to predict 1,1,1-TCA and daughter products contaminant-plume evolution in different Bio-PRBs.

Densely populated cities with a compact urban built environment have concerns over health risks derived from high levels of airborne particulate matter (PM) exposure. Understanding the association between PM and reactive oxygen species (ROS) is an important step towards unravelling the mechanisms behind. This study investigated the role of time-integrated PM sampling on cellular toxicity mechanism on a diurnal scale. The sampling took place in a highly urbanized part of Hong Kong at two contrast roadside and background sites, with simultaneous solid-PM and semi-volatile-PM (SV-PM) collection in both summer and winter seasons. A sampling day consisted three sampling intervals of 6 h each – 04:00–10:00, 12:00–18:00 and 20:00–02:00 h, representing morning rush hours, afternoon and night periods, respectively. Water and organic extracts of PM were prepared, with and without filtration, and exposed to RAW264.7 and A549 cell lines on a dose and time-dependent manner. Solid-PM and SV-PM contribution to total PM₂.₅ mass concentration was 9:1, with much higher SV-PM fraction at roadside over urban background (p < 0.001, n = 36). Also, the SV-PM mass concentration increased by 10–20% during 20:00–02:00 h compared to morning and afternoon sampling periods. Organic PM extract was observed to cause 23–29% higher cell death compared to water-soluble PM, which is complemented with increased ROS production in both cell lines. The cellular damage caused by oxidative stress, determined from increased HO-1 and TNF-α expression in RAW264.7 was higher compared to the A549, which demonstrated the greater induction of toxicity from organic PM extract over soluble PM. Similarly, the SV-PM induced greater than 2-fold cellular ROS generation on PM mass basis compared to solid-PM. Lack of phagocytic action in A549 compared to RAW264.7 suggested novel toxicity routes for water-soluble and organic PM that can be expected to occur during human PM inhalation-bronchi-alveolar exposure.

Microplastic pollution has received considerable attention in marine systems, but recent work shows substantial plastic pollution also occurs in freshwater ecosystems. Most freshwater research has focused on large rivers and lakes, but small streams are the primary interface between land, where plastic is used, and drainage networks. We examined variation in the amount and form of plastic occurring in small streams spanning an urbanisation gradient. All streams contained microplastics with concentrations similar to that found in larger systems (up to 303 particles m−3 in water and 80 particles kg−1 in sediment). The most abundant types were fragments and small particles (63–500 μm). Chemical types of plastic were quite variable and often not predictable based on size, form and colour. Variation in microplastic abundance across streams was high, but only partially explained by catchment scale parameters. There was no relationship between human population density or combined stormwater overflows and microplastic abundance. Residential land cover was related to microplastic abundance, but explanatory power was low. Our results suggest local-scale factors may be more important than catchment-scale processes in determining microplastic pollution in small streams.

The 6:2 chlorinated polyfluoroalkyl ether sulfonic acids (6:2 Cl-PFAES), 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoic acid (HFPO-DA) and perfluoroethylcyclohexane sulfonate (PFECHS) are emerging per- and polyfluoroalkyl substances (PFASs) that are being applied to replace phased-out PFASs, which have high persistency, high bioaccumulation potential and high toxicity. Recently, these emerging PFASs were observed in estuary and marine areas with a pollution level of ng/L. In this study, three levels (10 ng L⁻¹, 100 ng L⁻¹ and 1000 ng L⁻¹) for these PFASs were selected to investigate the response of marine Chlorella sp. to 14 days of exposure. The growth of Chlorella sp. was significantly inhibited by each PFAS over time. Treatments with 1000 ng/L exposure caused the most severe reduction in growth for each PFAS treatment. For the first half of the experimental period (from Day 0 to Day 6), the influence of each PFAS was not significant (p > 0.05). However, treatments with all concentrations of 6:2 Cl-PFAES, HFPO-DA and 1000 ng L⁻¹ PFECHS significantly reduced the growth of Chlorella sp. from Day 8. The superoxide dismutase (SOD) activities in Chlorella sp. were significantly increased (p < 0.05) when exposed to 6:2 Cl-PFAES, HFPO-DA and PFECHS. The catalase (CAT) and peroxidase (POD) activities in Chlorella sp. were significantly inhibited (p < 0.05) by each PFAS. The glutathione (GSH) contents in Chlorella sp. were significantly increased by each PFAS. However, the increases in GSH concentration in Chlorella sp. were low. The inhibition of algal growth was primarily due to the reduction of the activities of CAT and POD. PFECHS had the lowest toxicity among the three PFASs, and it induced less oxidized damage to Chlorella sp. In conclusion, as alternatives to phased-out PFASs, the emerging PFASs are not safe in aquatic environment, and attention should be paid to the management and restriction of these emerging PFASs.

Silver nanoparticles (AgNPs) have adverse impacts on plants when released into environments, but their toxic mechanism is still a matter of debate. Here we present a combined analysis of physiology and transcriptome of Arabidopsis thaliana leaves exposure to 30 mg L−1 AgNPs and Ag+ for six days to explore the toxicity mechanism of AgNPs on Arabidopsis. Both transcriptomic and physiological results showed that AgNPs induced reactive oxygen species (ROS) accumulation and damaged photosynthesis. The toxicity of AgNPs is not merely attributable to Ag+ release and much higher photosynthetic toxicity and ROS accumulation were observed in 30 mg L−1 AgNPs than that in 0.12 mg L−1 Ag+. About 60% genes were similarly up- or down-regulated at the same concentration of AgNPs and Ag+ and these genes were enriched in photosynthesis and response to the stimulus. However, 302 genes, including those involved in glucosinolates synthesis, were specifically regulated under AgNPs treatments. In conclusion, more than the released Ag+, nanoparticle-specific effects are responsible for the toxicity of AgNPs in Arabidopsis thaliana.

Boscalid as one of the most widely used succinate dehydrogenase inhibitor (SDHI) fungicides has been frequently detected in both freshwater and estuarine environments. Its acute toxic effects on zebrafish and freshwater algae have been reported in our previous studies. To further investigate its chronic toxic effects to aquatic organisms, adult zebrafish were exposed for 28 days to a series of environmentally relevant boscalid concentrations in this study. Growth indicators and histopathology were determined in this study. Results indicated that boscalid inhibited the growth of zebrafish and induced damage in the kidneys and liver. Carbohydrate and lipid metabolism as the key pathways of energy metabolism in growth of zebrafish were also investigated. Results showed boscalid caused an increase in the activity of hexokinase (HK), the content of glycogen, glucose-6-phosphatase (G6Pase), and insulin (INS) in liver and a decrease in blood glucose content and succinate dehydrogenase (SDH) activity. Boscalid reduced the total content of triacylglyceride (TG) and cholesterol (TC) and the activity of fatty acid synthase (FAS) and acetyl coenzyme A carboxylase (ACC) in the liver. Correspondingly, expression of the genes related to carbohydrate and lipid metabolism in liver and intestine was affected by boscalid, especially in the significant upregulation of G6Pase and pparα and downregulation of SGLT-1 and AMY. Results suggested that boscalid could affect carbohydrate metabolism of adult zebrafish via regulation of gluconeogenesis and glycolysis at 0.1 mg/L. Moreover, boscalid might induce an increase in β-oxidation and a decrease in lipid synthesis at 0.01 mg/L. In conclusion, our study identified that carbohydrate and lipid metabolism are the possible biological pathways that mediate boscalid-induced developmental effects.

Marine plastic debris, including microplastics (<5 mm in size), comprises a suite of chemical ingredients and sorbed chemical contaminants. Thus, microplastics are a potential, and debated, source of anthropogenic chemicals for bioaccumulation and biomagnification. Several studies have investigated the role of microplastics as a vector of contaminants to marine organisms via modeling exercises, laboratory experiments, and field studies. Here, we examined relationships among chemical contaminants and microplastics in lanternfish (family Myctophidae), an important link in marine food webs, from the North Pacific Ocean as a case study from the field. We compared the body burden of several chemical groups (bisphenol A [BPA], nonylphenol [4-NP], octylphenol [4n-OP], alkylphenol ethoxylates [APEs], pesticides, polychlorinated biphenyls [PCBs], and polybrominated diphenyl ethers [PBDEs]) in fish caught within and outside the North Pacific Subtropical Gyre where plastic is known to accumulate. We also tested whether there was a relationship between chemical concentrations in fish and plastic density at each sampling location. Mean concentrations of common plastic constituents (BPA, 4-NP, 4n-OP, APEs, and total PBDEs) were comparable between myctophids collected within and outside the North Pacific Gyre. Pesticides were higher in lanternfish caught outside the gyre and were associated with lower plastic density. Total PCBs were also higher in fish outside the gyre. In contrast, lower chlorinated PCB congeners were higher in fish residing in the accumulation zone and were correlated with higher plastic density. This finding is consistent with other studies demonstrating an association between lower chlorinated PCBs and plastics in biota and suggests that microplastic may be a transport mechanism for some chemicals in nature.

The co-occurrence of aquatic contaminants, such as antibiotics and herbicides, has motivated investigations into their interactive effects on aquatic organisms. We examined the combined effects of environmental concentrations of the antibiotic Enrofloxacin (Enro; 0–2.25 μg l−1) and Roundup OriginalDI (Roundup®; 0–0.75 μg active ingredient l−1), a glyphosate based-herbicide, on Elodea canadensis. Enro alone was not toxic, but the plants were highly sensitive to Roundup® whose toxicity is related to the induction of oxidative stress. The metabolism of Enro by plants into Ciprofloxacin (Cipro) was observed, and although former is not phytotoxic, oxidative events associated with Cipro generation were observed. The activity of cytochrome P450 was shown to be involved in Enro degradation in E. canadensis. As a cytochrome P450 inhibitor, Roundup® decreases Enro metabolism in plants. Enro, in turn, increases glyphosate uptake and toxicity, so that Enro and Roundup® have synergistic effects, disrupting the physiological processes of E. canadensis. Our results suggest E. canadensis as a potential candidate for the reclamation of Enro in contaminated waters, but not for Roundup® due to its high sensitivity to that herbicide.

Although the poultry production sector plays a key role in sustaining the majority of animal protein demand in Egypt, the deleterious effects of widespread antibiotic resistance on health and environment are currently not well recognized. Litter and dropping samples from broiler and layer poultry farms as well as, tilapia samples from the Nile River and aquaculture farms were collected from Upper Egypt. Samples were extracted and examined for tetracycline residues [tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC) and doxycycline (DC)] using HPLC. In addition, tetracycline resistance genes [tet (M), tet (W), tet (Q) and tet (G)] were screened from pooled intestinal contents collected from twelve broiler farms in Upper Egypt. The antibiotic resistance genes results revealed that tet (W) was confirmed to be expressed in all intestinal samples. In contrast, tet (Q) and tet (M) were detected only in 42% and 17% of the samples, respectively. CTC and OTC were the antimicrobial compounds with the highest concentrations in poultry litter and droppings, with concentrations of 6.05 and 2.47 μg g−1 (CTC) and 5.9 and 1.33 μg g−1 (OTC), respectively. However, the concentrations of DC were significantly higher than those of the other compounds in both aquaculture and Nile River tilapia. The tetracycline residue levels in aquaculture tilapia were significantly higher than those in Nile River tilapia. The hazard quotients (HQs) exceeded 1 for OTC, CTC and DC, which highlights the great risk of using broiler litter to fertilize agricultural land. Moreover, the presence of DC and CTC indicates that consumption of aquaculture tilapia poses a considerable health risk. Therefore, poultry litter or droppings containing tetracycline residues and tet resistance determinants used for aquaculture or as farmland fertilizers could be major sources of antibiotic resistance in fish, humans and environment.