Polychlorinated biphenyls (PCBs) are persistent organic pollutants that, due to their high toxicity, lipophilic property and widespread dispersal in the global environment, present a danger for human health and ecological systems. Although the inventory and use of PCBs are extensively reported worldwide, the status of PCBs in Iran is still unknown. In this study, the concentrations of PCBs were determined in the environmental matrices and in five commercially important fish species from Larak coral Island, Persian Gulf, Iran, in winter and summer 2015. A positive correlation was found among PCBs levels and congeners profiles in seawater (0.97–3.10 ng L⁻¹), surface sediments (2.95–7.95 ng g⁻¹dw) and fish samples (7.20–90.19 ng g⁻¹dw), indicating fish as suitable bioindicator of environmental PCBs contamination. In all matrices, a high contribution of light and medium chlorinated congeners was detected in both seasons. In fish, the higher PCBs levels were found for both sexes in both seasons in liver and kidney than other tissues (skin, gonad, muscle) due to their high lipid content and PCBs lipophilicity. More importantly, the risks for human health associated with fish consumption were also evaluated, and it was found that all the toxicity indices measured for PCBs were within the World Health Organization (WHO) permissible limit of food consumption. However, it is highly recommended to inform the local population about potential risks attributable to dietary incorporation of locally caught fish, and establish a surveillance monitoring programme on PCBs in this region.

Metal pollution has been associated with anthropogenic activities, such as effluents and emissions from mines. Soil could be exposure route of wild rats to metals, especially in mining areas. The aim of this study was to verify whether soil exposure under environmentally relevant circumstances results in metal accumulation and epigenetic modifications. Wistar rats were divided to three groups: 1) control without soil exposure, 2) low-metal exposure group exposed to soil containing low metal levels (Pb: 75 mg/kg; Cd: 0.4), and 3) high-metal exposure group exposed to soil (Pb: 3750; Cd: 6). After 1 year of exposure, the metal levels, Pb isotopic values, and molecular indicators were measured. Rats in the high-group showed significantly greater concentrations of Pb and Cd in tissues. Higher accumulation factors (tissue/soil) of Cd than Pb were observed in the liver, kidney, brain, and lung, while the factor of Pb was higher in the tibia. The obtained results of metal accumulation ratios (lung/liver) and stable Pb isotope ratios in the tissues indicated that the respiratory exposure would account for an important share of metal absorption into the body. Genome-wide methylation status and DNA methyltransferase (Dnmt 3a/3b) mRNA expressions in testis were higher in the high-group, suggesting that exposure to soil caused metal accumulation and epigenetic alterations in rats.

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.

Bats are particularly suited as bioindicators of trace element pollution due to their longevity and their position in the trophic chain. In this study, the concentrations of ten non-essential trace elements (Al, As, Ba, Cd, Hg, Pb, Sb, Sr, Th, Tl) were determined in the tissues (whole body, skin-fur, skinned body, liver, kidney and bone) of lactant Tadarida teniotis from a nursery colony in Rome. A large number of bats from this nursery died before fledging and had bone deformities and fractures. The concentrations of non-essential trace elements in bone and whole body were also analysed in adult specimens of Miniopterus schreibersii from a colony located in a natural park in Northern Italy. In lactant T. teniotis, the Pb concentration decreased in the following order: bone>liver>skinned body>whole body>skin-fur>kidney, and exceeded the toxic threshold associated with negative effects reported for different mammalian species. The levels of the other non-essential trace elements were within a range indicative of low environmental contamination in both species. Significant interspecies differences (P < 0.05) were observed for concentrations of Pb and Ba, higher in the bones of T. teniotis, and of Cd, Hg and Sr, higher in the bones of M. schreibersii. In lactant T. teniotis, the different sources of Pb exposure, through inhalation and/or food, may represent a potential threat to the colony of this synanthropic European bat.

Chemical mixtures represent environmentally-realistic exposures of contaminants to aquatic biota. However, there remains a limited understanding of how toxicant mixtures may impact biological function, relative to their individual components. In the current study, oxidative stress responses of the freshwater galaxiid fish inanga (Galaxias maculatus) were examined following exposure to the pro-oxidant trace metal cadmium (2 or 9 μg L⁻¹), and the anti-oxidant pharmaceutical drug diclofenac (770 μg L⁻¹), individually or in simple binary mixtures. Cadmium exposure in the absence of diclofenac significantly decreased renal catalase activity, increased hepatic catalase activity, decreased renal superoxide dismutase (SOD) and decreased glutathione-S-transferase activity, effects that are suggestive of anti-oxidant defense inhibition and/or generation of increased reactive oxygen species. Diclofenac exposure in the absence of cadmium resulted in a decreased renal lipid peroxidation, consistent with its known anti-oxidant properties. The presence of waterborne diclofenac altered the effects of cadmium on catalase activity in the liver, SOD activity in the gill, and lipid peroxidation in the liver. Co-exposure with cadmium modulated diclofenac effects on lipid peroxidation in the kidney. These data indicate the capacity of each of these toxicants to offset biological effects of the other when both co-occur in urban waters at specific concentrations. This study also demonstrates the complexity of outcomes in contaminant mixtures, even when these stressors are presented as simple binary combinations.

Recent studies have demonstrated the occurrence of microplastic fibers (MFs) in soil environments. To determine whether MFs are harmful for soil biota, we evaluated toxic effects on terrestrial snails (Achatina fulica) after 28 d exposure to polyethylene terephthalate MFs at concentrations of 0.01–0.71 g kg−1 (dry soil weight). Digestion kinetics experiments on 24 snails showed that MFs can be ingested and excreted within 48 h. We found the appearance of cracks and deterioration on the surface of MFs after depuration by the digestive system. Prolonged exposure to 40 snails showed that 0.14–0.71 g kg−1 MFs caused an average reduction of 24.7–34.9% food intake and 46.6–69.7% excretion. 0.71 g kg−1 MFs induced significant villi damage in the gastrointestinal walls of 40% snails, but did not influence the histology of the liver and kidney. Moreover, 0.71 g kg−1 MFs exposure reduced glutathione peroxidase (59.3 ± 13.8%) and total antioxidant capacity (36.7 ± 8.5%), but elevated malondialdehyde level (58.0 ± 6.4%) in the liver, which indicates oxidative stress is involved in the toxic mechanism. Our results suggest that MFs have adverse impacts on the fitness of soil organisms, and highlight the ecological risks of microplastic pollution in terrestrial ecosystems.

Water, sediment, and wild aquatic species were collected from an electronic waste (e-waste) polluted pond in South China. This study aimed to investigate the bioaccumulation, tissue distribution, and trophic transfer of organophosphorus flame retardants (PFRs) in these aquatic organisms. The concentrations of PFRs detected in the analyzed organisms were between 1.7 and 47 ng/g wet weight (ww). Oriental river prawn and snakehead exhibited the highest and lowest levels, respectively. Tri-n-butyl phosphate (TnBP), tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP) and triphenyl phosphate (TPhP) were dominant contaminants, accounting for approximately 86% of the total sum. The mean values of bioaccumulation factors (BCFs) and logarithmic biota-sediment accumulation factors (log BSAFs) for individual PFRs varied from 6.6 to 1109 and from −2.0 to 0.41, respectively. Both log BCFs and log BSAFs of PFRs were significantly and positively correlated with their octanol-water partitioning coefficient (log KOW). The concentrations of PFRs in tissues of large mud carp and snakehead were significantly and positively correlated with the lipid content (each p < 0.05) and the liver, kidney, and gill exhibited high PFR levels. When the concentration was expressed on a lipid basis, liver exhibited the lowest level, indicating the probable effects of metabolism. Significantly positive correlation was also found between lipid content and total PFR concentration in muscle of all aquatic organisms, given the strong correlation between lipid content and the concentration of TnBP. Trophic magnification factors (TMF) of TnBP and TPhP were lower than 1 (0.57 and 0.62), indicating that these PFRs undergo trophic dilution in this aquatic food web.

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.

Selenium and mercury were evaluated in tissues and stomachs of the dolphinfish Coryphaena hippurus from two sites in the Southeastern Gulf of California. Hg levels were consistently low and exhibited the following patterns: muscle (0.14 ± 0.01 μg/g wet weight) followed by kidney (0.12 ± 0.02 μg/g), liver (0.11 ± 0.01 μg/g), and gonads (0.04 ± 0.00 μg/g). The maximum of Se was found in the kidney (5.60 ± 0.40 μg/g) and the minimum in muscle (0.60 ± 0.01 μg/g). All the Se:Hg molar ratios were between 3.7 and 697.1, with the minimum in muscle and the highest in gonads. The results indicate a contrasting behavior biomagnification of Hg and Se; smaller fish (<80 cm FL) did not exhibit biomagnification, in contrast with larger fish (>90 cm FL: 100% for Hg; 65% for Se). These results appear to be related to different feeding habits and availability of prey.

Silver (Ag) is a non-essential metal known to bioaccumulate in aquatic organisms. We determined Ag concentrations in five false killer whales stranded in South America. Silver concentrations (in dry weight basis) range as 6.62–10.78 μg g⁻¹ in liver, 0.008–7.41 μg g⁻¹ in spleen, 0.004–5.71 μg g⁻¹ in testis, 0.757–1.69 μg g⁻¹ in kidney, 0.011–0.078 μg g⁻¹ in lung and < 0.01–0.038 μg g⁻¹ in muscle, whereas in the single samples of uterus and ovary were 0.051 and 0.023 μg g⁻¹; respectively. Overall, Ag concentration in liver and kidney exceeded the cetacean toxic thresholds, proposed as “unhealthy concentrations” and “critically dangerous” in liver and kidney. These results warrant further eco-toxicological studies, to examine biological effects of elevated silver levels for individuals and to assess the species' conservation status with respect to marine pollution.