Chemicals sorbed to environmental microplastics are toxic to early life stages of aquatic organisms.

Microplastics are ubiquitous in aquatic ecosystems, but little information is currently available on the dangers and risks to living organisms. In order to assess the ecotoxicity of environmental microplastics (MPs), samples were collected from the beaches of two islands in the Guadeloupe archipelago, Petit-Bourg (PB) located on the main island of Guadeloupe and Marie-Galante (MG) on the second island of the archipelago. These samples have a similar polymer composition with mainly polyethylene (PE) and polypropylene (PP). However, these two samples are very dissimilar with regard to their contamination profile and their toxicity. MPs from MG contain more lead, cadmium and organochlorine compounds while those from PB have higher levels of copper, zinc and hydrocarbons. The leachates of these two samples of MPs induced sublethal effects on the growth of sea urchins and on the pulsation frequency of jellyfish ephyrae but not on the development of zebrafish embryos. The toxic effects are much more marked for samples from the PB site than those from the MG site. This work demonstrates that MPs can contain high levels of potentially bioavailable toxic substances that may represent a significant ecotoxicological risk, particularly for the early life stages of aquatic animals.

Polycyclic aromatic compounds in urban soils of Stockholm City: Occurrence, sources and human health risk assessment.

Polycyclic aromatic compounds (PACs) are ubiquitous pollutants that are found everywhere in our environment, including air, soil and water. The aim of this study was to determine concentrations, distribution, sources and potential health risk of 43 PACs in soils collected from 25 urban parks in Stockholm City, Sweden. These PACs included 21 PAHs, 11 oxygenated PAHs, 7 methylated PAHs, and 4 azaarenes whose concentrations ranged between 190 and 54 500, 30.5-5 300, 14.9-680, and 4.17-590 ng/g soil, respectively. Fluoranthene was found at the highest levels ranging between 17.7 and 9800 ng/g, benzo[a]pyrene between 9.64 and 4600 ng/g, and the highly potent carcinogen dibenzo[a,l]pyrene up to 740 ng/g. The most abundant oxy-PAH was 6H-benzo[cd]pyren-6-one (2.09-2300 ng/g). Primary sources of PAHs were identified by use of diagnostic ratios and Positive Matrix Factorization modelling and found to be pyrogenic including vehicle emissions and combustion of biomass. Estimating the incremental lifetime cancer risks (ILCRS) associated with exposure to PAHs in these soils indicated that the PAH levels in some parks constitute a considerable increased risk level for adults and children (total ILCR > 1 × 10-4). Compared to worldwide urban parks contamination, we conclude that the PAC soil levels in parks of Stockholm City in general are low, but that some parks are more heavily contaminated and should be considered for clean-up actions to limit human health risks.

Genotoxicity of TiO2 nanoparticles assessed by mini-gel comet assay and micronucleus scoring with flow cytometry.

The widespread production and use of nanoparticles calls for faster and more reliable methods to assess their safety. The main aim of this study was to investigate the genotoxicity of three reference TiO2 nanomaterials (NM) within the frame of the FP7-NANoREG project, with a particular focus on testing the applicability of mini-gel comet assay and micronucleus (MN) scoring by flow cytometry. BEAS-2B cells cultured under serum-free conditions were exposed to NM100 (anatase, 50-150nm), NM101 (anatase, 5-8nm) and NM103 (rutile, 20-28nm) for 3, 24 or 48h mainly at concentrations 1-30 µg/ml. In the mini-gel comet assay (eight gels per slide), we included analysis of (i) DNA strand breaks, (ii) oxidised bases (Fpg-sensitive sites) and (iii) light-induced DNA damage due to photocatalytic activity. Furthermore, MN assays were used and we compared the results of more high-throughput MN scoring with flow cytometry to that of cytokinesis-block MN cytome assay scored manually using a microscope. Various methods were used to assess cytotoxic effects and the results showed in general no or low effects at the doses tested. A weak genotoxic effect of the tested TiO2 materials was observed with an induction of oxidised bases for all three materials of which NM100 was the most potent. When the comet slides were briefly exposed to lab light, a clear induction of DNA strand breaks was observed for the anatase materials, but not for the rutile. This highlights the risk of false positives when testing photocatalytically active materials if light is not properly avoided. A slight increase in MN formation for NM103 was observed in the different MN assays at the lower doses tested (1 and 5 µg/ml). We conclude that mini-gel comet assay and MN scoring using flow cytometry successfully can be used to efficiently study cytotoxic and genotoxic properties of nanoparticles.

In vivo micronucleus screening in zebrafish by flow cytometry.

Micronucleus (MN) assay is extensively used to biomonitor aneuploidy and clastogenicity of genotoxic compounds. However, the suitability of this assay for early life stages of model fish species is still poorly documented. In this study, the determination of MN using flow cytometry was successfully applied for the first time to zebrafish (Danio rerio) larvae. Mitomycin C (MMC), etoposide (ETO), cyclophosphamide, demecolcine (COL), benzo[a]pyrene (BP) and dibenzo[def,p]chrysene (DBC) were selected as model genotoxicants. The method was first confirmed in human HepG2 liver cells and then applied in vivo on isolated cells from exposed 4 days post fertilisation zebrafish larvae. All tested compounds induced MN formation. The flow cytometry results were validated by a strong correlation with results from a standard MN microscopy analysis (P = 0.002). Moreover, flow cytometry analysis enabled the detection of an up to 3.7-fold increase of hypodiploidy in zebrafish exposed to MMC, COL, BP or DBC. MMC, COL and DBC induced more than a 2-fold MN increase by flow cytometry and were therefore considered as the most suitable positive controls for in vivo zebrafish MN determination. These findings make important contribution by proposing a new reliable and sensitive method for using zebrafish as a model for genotoxicity monitoring.

Environmental concentrations of benz[a]anthracene induce developmental defects and DNA damage and impair photomotor response in Japanese medaka larvae.

Benz[a]anthracene (BaA) is a ubiquitous polycyclic aromatic hydrocarbon found in numerous aquatic ecosystems. However, ecotoxicological data in aquatic organisms are scarce. To remedy this lack of data, Japanese medaka (Oryzias latipes) embryos were exposed to BaA and toxic effects were investigated at multiple toxicological endpoints. Japanese medaka embryos were incubated onto BaA-spiked artificial sediment for 9 days at low or moderate environmental concentrations ranging from 0.9 to 12 µgg(-1) dw. BaA-exposed embryos exhibited significant tachycardia. BaA exposure was also shown to increase CYP1A activity in the hepato-biliary tissue as well as craniofacial deformities and DNA damage in pro-larvae. The photomotor response of BaA-exposed larvae was reduced in comparison to the control group. According to this set of tests, the lowest tested and observed effect concentration (LOEC) for Japanese medaka early life stages was equivalent to 0.92 µgg(-1) dw of BaA. This concentration fall into the range of concentrations frequently encountered in sediments of polluted aquatic ecosystems. Taking into consideration these results, BaA represents a threat for fish early life stages in particular those developing onto or into contaminated sediments.

Temporal distribution of microplastics and other anthropogenic particles in four marine species from the Atlantic coast (France).

The characterization of microplastic (MP) contamination in marine species is increasing as concerns about environmental and food safety are more and more discussed. Here, we reported a quantitative and qualitative assessment of the contamination by anthropogenic particles (from visual sorting; AP) and MP (plastic-made) in the whole soft body or digestive tract of marine species. Four commercial species were studied, namely the Pacific oyster (Magallana gigas), the spiny spider crab (Maja sp.), the common sole (Solea solea) and seabass (Dicentrarchus labrax or punctatus). AP and MP uptake were studied over three to four seasons depending on the species. After tissues digestion, particles were extracted under a stereomicroscope and morphometric characteristics were reported. Then, polymers were identified by ATR-FTIR spectroscopy. Seasonal variations were mainly described in the Pacific oyster as AP uptake was lower in autumn and MP uptake was higher in spring. These variations may be linked to the reproduction and growth cycles of this species. Moreover, seabass ingestion was lower in autumn compared to winter. Contamination in spider crabs and soles showed either weak or no seasonal trends, both quantitatively and qualitatively. Overall, AP contamination in all studied species ranged from 1.17 ± 1.89 AP.ind-1 (in sole) to 4.07 ± 6.69 AP.ind-1 (in seabass) while MP contamination ranged from 0.10 ± 0.37 MP.ind-1 (in sole) to 1.09 ± 3.06 MP.ind-1 (in spider crab). Fibers were mostly reported in all species (at least 77.7%), along with cellulosic polymers (at least 43.7%). AP and MP uptake were detected in all species and at almost all seasons, with the only exception of the common sole during autumn. Therefore, this study emphasizes the ubiquity of AP and MP contamination in marine species and provides new knowledges about seasonal uptake by commercial species.

Spatial distribution of anthropogenic particles and microplastics in a meso-tidal lagoon (Arcachon Bay, France): A multi-compartment approach.

Assessment of microplastic (MP) contamination is still needed to evaluate this threat correctly and tackle this issue. Here, MP contamination was assessed for a meso-tidal lagoon of the Atlantic coast (Arcachon Bay, France). Sea surface, water column, intertidal sediments and wild oysters were sampled. Five different stations were studied to assess the spatial distribution of the contamination. Two were outside of the bay and three were inside the bay (from the inlet to the back). A distinction was made between all anthropogenic particles (AP, i.e. visually sorted) and MP (i.e. plastic polymer confirmed by ATR-FTIR spectroscopy). The length of particles recovered in this study ranged between 17 µm and 5 mm. Concentration and composition in sea surface and water column samples showed spatial variations while sediment and oyster samples did not. At outside stations, the sea surface and the water column presented a blended composition regarding shapes and polymers and low to high concentrations (e.g. 0.16 ± 0.08 MP.m-3 and 561.7 ± 68.5 MP.m-3, respectively for sea surface and water column), which can be due to coastal processes and nearby input sources. The inlet station displayed a well-marked pattern only at the sea surface. High AP and MP concentrations were recorded, and fragments along with polyethylene overwhelmed (respectively 76.0 % and 73.2 %). Higher surface currents could explain this pattern. At the bay back, AP and MP concentrations were lower and fibers were mainly recorded. Weaker hydrodynamics in this area was suspected to drive this contamination profile. Overall, fragments and buoyant particles were mainly detected at the sea surface while fibers and negatively buoyant particles prevailed in other compartments. Most of the studied samples presented an important contribution of fiber-shaped particles (from 31.5 % to 94.2 %). Finally, contamination was ubiquitous as AP and MP were found at all stations in all sample types.

Effect of an environmental microplastic mixture from the Seine River and one of the main associated plasticizers, dibutylphthalate, on the sentinel species Hediste diversicolor.

The aim of this study was to explore the adverse effects of a microplastic (MP) mixture obtained from litter accumulated in the Seine River (France) compared to those of their major co-plasticizer, dibutylphthalate (DBP), on the sentinel species Hediste diversicolor. A suite of biomarkers has been investigated to study the impacts of MPs (100 mg kg-1 sediment), DBP (38 µg kg-1 sediment) on worms compared to non-exposed individuals after 4 and 21 days. The antioxidant response, immunity, neurotoxicity and energy and respiratory metabolism were investigated using biomarkers. After 21 days, worms exposed to MPs showed an increasing aerobic metabolism, an enhancement of both antioxidant and neuroimmune responses. Energy-related biomarkers demonstrated that the energy reallocated to the defence system may come from proteins. A similar impact was depicted after DBP exposure, except for neurotoxicity. Our results provide a better understanding of the ecotoxicological effects of environmental MPs and their associated-contaminants on H. diversicolor.

Environmental microplastics disrupt swimming activity in acute exposure in Danio rerio larvae and reduce growth and reproduction success in chronic exposure in D. rerio and Oryzias melastigma.

Microplastics (MPs), widely present in aquatic ecosystems, can be ingested by numerous organisms, but their toxicity remains poorly understood. Toxicity of environmental MPs from 2 beaches located on the Guadeloupe archipelago, Marie Galante (MG) and Petit-Bourg (PB) located near the North Atlantic gyre, was evaluated. A first experiment consisted in exposing early life stages of zebrafish (Danio rerio) to MPs at 1 or 10 mg/L. The exposure of early life stages to particles in water induced no toxic effects except a decrease in larval swimming activity for both MPs exposures (MG or PB). Then, a second experiment was performed as a chronic feeding exposure over 4 months, using a freshwater fish species, zebrafish, and a marine fish species, marine medaka (Oryzias melastigma). Fish were fed with food supplemented with environmentally relevant concentrations (1% wet weight of MPs in food) of environmental MPs from both sites. Chronic feeding exposure led to growth alterations in both species exposed to either MG or PB MPs but were more pronounced in marine medaka. Ethoxyresorufin-O-deethylase (EROD) and acetylcholinesterase (AChE) activities were only altered for marine medaka. Reproductive outputs were modified following PB exposure with a 70 and 42% decrease for zebrafish and marine medaka, respectively. Offspring of both species (F1 generation) were reared to evaluate toxicity following parental exposure on unexposed larvae. For zebrafish offspring, it revealed premature mortality after parental MG exposure and parental PB exposure produced behavioural disruptions with hyperactivity of F1 unexposed larvae. This was not observed in marine medaka offspring. This study highlights the ecotoxicological consequences of short and long-term exposures to environmental microplastics relevant to coastal marine areas, which represent essential habitats for a wide range of aquatic organisms.

Chronic feeding exposure to virgin and spiked microplastics disrupts essential biological functions in teleost fish.

Toxicity of polyethylene (PE) and polyvinyl chloride (PVC) microplastics (MPs), either virgin or spiked with chemicals, was evaluated in two short-lived fish using a freshwater species, zebrafish, and a marine species, marine medaka. Exposures were performed through diet using environmentally relevant concentrations of MPs over 4 months. No modification of classical biomarkers, lipid peroxidation, genotoxicity or F0 behaviour was observed. A significant decrease in growth was reported after at least two months of exposure. This decrease was similar between species, independent from the type of MPs polymer and the presence or not of spiked chemicals, but was much stronger in females. The reproduction was evaluated and it revealed a significant decrease in the reproductive output for both species and in far more serious numbers in medaka. PVC appeared more reprotoxic than PE as were MPs spiked with PFOS and benzophenone-3 compared to MPs spiked with benzo[a]pyrene. Further, PVC-benzophenone-3 produced behavioural disruption in offspring larvae. These results obtained with two species representing different aquatic environments suggest that microplastics exert toxic effects, slightly different according to polymers and the presence or not of sorbed chemicals, which may lead in all cases to serious ecological disruptions.

Mixture effects of oxygenated PAHs and benzo[a]pyrene on cardiovascular development and function in zebrafish embryos.

Polycyclic aromatic compounds (PACs), including polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (oxy-PAHs), are common environmental pollutants known to cause health effects in humans and wild-life. In particular, vertebrate cardiovascular development and function are sensitive to PACs. However, the interactive effects of PAHs and oxy-PAHs on cardiovascular endpoints have not been well studied. In this study, we used zebrafish embryos (ZFEs) as a model to examine developmental and cardiovascular toxicities induced by the three environmental oxy-PAHs benzo[a]fluorenone (BFLO), 4H-cyclopenta[def]phenanthren-4-one (4H-CPO) and, 6H-benzo[cd]pyren-6-one (6H-BPO), and the PAH benzo[a]pyrene (BaP) either as single exposures or binary oxy-PAH + PAH mixtures. 6H-BPO induced developmental and cardiovascular toxicity, including reduced heartbeat rate and blood flow, at lower doses compared to the other compounds. Exposure to binary mixtures generally caused enhanced toxicity and induction of aryl hydrocarbon receptor (AhR)-regulated gene expression (ahr2 and cyp1a) compared to single compound exposure. This was associated with differential expression of genes involved in cardiovascular development and function including atp2a2, myh6, tbx5 and zerg. AhR-knock-down significantly reduced the cardiovascular toxicity of 6H-BPO and its binary mixture with BaP indicating a significant AhR-dependence of the effects. Measurements of internal concentrations showed that the toxicokinetics of BaP and 6H-BPO were altered in the binary mixture compared to the single compound exposure, and most likely due to CYP1 inhibition by 6H-BPO. Altogether, these data support that similar to interactions between PAHs, mixtures of PAHs and oxy-PAHs may cause increased developmental and cardiovascular toxicity in ZFEs through an AhR-dependent mechanism.

Environmental samples of microplastics induce significant toxic effects in fish larvae.

Microplastics (MPs) are present throughout aquatic ecosystems, and can be ingested by a wide variety of organisms. At present, the physical and chemical effects of environmental MPs on aquatic organisms are poorly documented. This study aims to examine the physiological and behavioral effects caused by fish consuming environmental microplastics at different life stages. MP samples were collected from beaches on three islands (Easter Island, Guam and Hawaii) located near the North and South gyres of the Pacific Ocean. Larvae and juveniles of Japanese Medaka were fed for 30days with three doses of MPs (0.01, 0.1 and 1% w/w in fish food) approximate to the concentrations measured in moderately and heavily contaminated ocean areas. Ingestion of MPs by medaka larvae caused (variously) death, decreased head/body ratios, increased EROD activity and DNA breaks and, alterations to swimming behavior. A diet of 0.1% MPs was the most toxic. Two-month-old juveniles fed with 0.01% MPs did not exhibit any symptoms except an increase in DNA breaks. Our results demonstrate ingestion and mainly sublethal effects of environmental MPs in early life stages of fish at realistic MP concentrations. The toxicity of microplastics varies from one sample to another, depending on polymer composition, weathering and pollutant content. This study examines the ecological consequences microplastic build-up in aquatic ecosystems, more particularly in coastal marine areas, which serve as breeding and growing grounds for a number of aquatic species.

High density polyethylene (HDPE) microplastics impair development and swimming activity of Pacific oyster D-larvae, Crassostrea gigas, depending on particle size.

Understanding the effects of plastic debris on marine ecosystems is essential in encouraging decision-makers to take action. The present study investigates the effect of a 24 h experimental exposure to high density polyethylene (HDPE) microplastics (MPs) of different sizes (4-6, 11-13 and 20-25 µm) and at three concentrations (0.1, 1 and 10 mg MP.L-1) on the development and locomotor activity of early stages of Pacific oyster, Crassostrea gigas. The bivalve embryo-larval assay (NF ISO 17244, 2015) was used in this study but with additional toxicity criteria: developmental arrests, abnormal D-larvae, maximum speed and swimming trajectory. Copper (Cu), was used as a positive control. Our results show that smaller MPs (4-6 and 11-13 µm) induced higher rates of malformations and developmental arrests than the larger ones (20-25 µm). In addition, a dose-dependent decrease of maximum swimming speed was observed for larvae exposed to MPs of 4-6 and 11-13 µm. On the other hand, there was no significant difference in swimming speed with the largest MPs size tested (20-25 µm). For all three sizes of MPs, there was a decrease in straight-line swimming trajectories, and an increase in circular trajectories. This abnormal swimming behaviour could affect larvae survival as well as colonization of new habitats.

Juvenile fish caging as a tool for assessing microplastics contamination in estuarine fish nursery grounds.

Estuaries serve as nursery grounds for many marine fish species. However, increasing human activities within estuaries and surrounding areas lead to significant habitat quality degradation for the juveniles. In recent years, plastic pollution has become a global environmental issue as plastic debris are found in all aquatic environments with potential adverse impacts on marine biota. Given the important ecological role of estuaries and implications of microplastics (MP) in ecosystems, here we assess the occurrence, number, size, and polymer types of MP ingested by wild and caged juvenile European flounder (Platichthys flesus). We deployed caged fish for 1 month at five sites in three estuaries in the eastern English Channel. The Seine estuary, heavily impacted by manmade modifications and one of the most contaminated estuaries in Europe, was compared to two smaller estuaries (Canche and Liane) less impacted by industrial activities. We found that juvenile flounders (7-9 cm) were vulnerable to plastic ingestion. Seventy-five percent of caged fish and 58% of wild caught fish had the presence of MP items in their digestive tract. Fibers (69%) dominated in the fish's digestive tract at all sites. An average of 2.04 ± 1.93 MP items were ingested by feral juvenile flounder and 1.67 ± 1.43 by caged juvenile flounder. For the caged fish, the three sites impacted by wastewater treatment plant (Liane, Le Havre harbor, and Rouen) were those with the highest percentage of individuals that has ingested MP items. Most of the isolated items were fibers and blue in color. Polymers identified by micro Raman spectroscopy were polycaprolactam, polyethylene terephthalate, and polyurethane. Although other environmental factors may have affected caged fish condition and mortality, we found no significant correlation with the number of ingested MP. However, the high occurrence of MP ingested by juvenile fish on nursery grounds raises concerns on their potential negative effects for fish recruitment success and population renewal. Finally, this study describes, for the first time, the feasibility of using caged juvenile fish as an assessing tool of MP contamination in estuarine nursery grounds.

Organic contaminants sorbed to microplastics affect marine medaka fish early life stages development.

The role of polyethylene microplastics 4-6 µm size (MPs) in the toxicity of environmental compounds to fish early life stages (ELS) was investigated. Marine medaka Oryzias melastigma embryos and larvae were exposed to suspended MPs spiked with three model contaminants: benzo(a)pyrene (MP-BaP), perfluorooctanesulfonic acid (MP-PFOS) and benzophenone-3 (MP-BP3) for 12 days. There was no evidence of MPs ingestion but MPs agglomerated on the surface of the chorion. Fish ELS exposed to virgin MPs did not show toxic effects. Exposure to MP-PFOS decreased embryonic survival and prevented hatching. Larvae exposed to MP-BaP or MP-BP3 exhibited reduced growth, increased developmental anomalies and abnormal behavior. Compared to equivalent waterborne concentrations, BaP and PFOS appeared to be more embryotoxic when spiked on MPs than when alone in seawater. These results suggest a relevant pollutant transfer by direct contact of MPs to fish ELS that should be included in the ecotoxicological risk assessment of MPs.

Gene expression patterns and related enzymatic activities of detoxification and oxidative stress systems in zebrafish larvae exposed to the 2,4-dichlorophenoxyacetic acid herbicide.

The present study aims to assess the effects of 2,4-D herbicide on biotransformation and oxidative stress status of zebrafish larvae. Animals were exposed to a range of sublethal concentrations (0.02-0.8 mg/L) and biomarkers at transcriptomic level and biochemical level were assessed. Chemical analysis with showed that the bioaccumulation of 2,4-D in 96 hpf zebrafish larvae were increased in a concentration-dependent manner. This herbicide induced significant effects at both gene expression and enzymatic activities levels after at 96 hpf. Results of mRNA expression showed a differential transcription regulation with all target genes depending on the tested concentrations. The mRNA level of gsr and cyp1a were up regulated at the highest dose of herbicide (0.8 mg/L). The gene expression of gstp1 showed an up regulation at lower dose (0.02 mg/L) and a down regulation at the highest dose (0.8 mg/L) of 2,4-D. A significant induction of EROD activity and inhibition of GST activity were noted in groups exposed to 0.8 mg/L of 2,4-D. Considering the antioxidant defenses, the activity of CAT was increased in larvae exposed to 0.8 mg/L of herbicide and GPx activity was induced at lower doses of 2,4-D (0.02 and 0.051 mg/L). Moreover, peroxidative damage, assessed as MDA content, was markedly increased in larvae exposed to high 2,4-D concentration. Overall, the present study data indicate that bioaccumulation of 2,4-D in 96 hpf zebrafish larvae and alterations in detoxification and oxidative stress related parameters, likely associated with ROS production, which may endanger the embryo-larval stages development of fish.

Induction and inhibition of human cytochrome P4501 by oxygenated polycyclic aromatic hydrocarbons.

Oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) are found in the environment together with PAHs. However, less is known concerning their biological activity including their impact on aryl hydrocarbon receptor (AHR) signalling and the subsequent modulation of the cytochrome P450 monooxygenases (CYP). In this study, the effects of 15 environmentally relevant oxy-PAHs on the induction and activity of the CYP1 enzymes were determined in vitro by measuring gene expression levels and enzyme activity. We found that nine of the tested oxy-PAHs significantly induced CYP1A1 and CYP1B1 gene expression in human keratinocytes (HaCaT cells) while only five of these also were potent inducers of CYP1-dependent ethoxyresorufin-O-deethylase (EROD) activity suggesting that some of the oxy-PAHs are both activators of AHR signalling and inhibitors of CYP1 function. Using a recombinant human CYP1A1 enzyme we showed that eleven of the oxy-PAHs potently inhibited enzyme activity with benz[a]anthracene-7,12-quinone (7,12-BAQ) and benzo[a]fluorenone (BFLO) being the most potent inhibitors (IC50 = 0.037 and 0.061 µM, respectively). We further exposed HaCaT cells to binary mixtures of oxy-PAHs and the model AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to investigate potential interaction effects. The results showed that oxy-PAHs can interfere with the TCDD-mediated effects leading to reduced CYP1A1 and 1B1 expression and EROD activity. These data represent the first demonstration that oxy-PAHs can be potent inhibitors of CYP1 expression and function and make important contributions towards understanding the mechanisms through which oxy-PAHs can contribute to the overall risk of polycyclic aromatic compounds.

Psychotropic drugs in mixture alter swimming behaviour of Japanese medaka (Oryzias latipes) larvae above environmental concentrations.

Psychiatric pharmaceuticals, such as anxiolytics, sedatives, hypnotics and antidepressors, are among the most prescribed active substances in the world. The occurrence of these compounds in the environment, as well as the adverse effects they can have on non-target organisms, justifies the growing concern about these emerging environmental pollutants. This study aims to analyse the effects of six psychotropic drugs, valproate, cyamemazine, citalopram, sertraline, fluoxetine and oxazepam, on the survival and locomotion of Japanese medaka Oryzias latipes larvae. Newly hatched Japanese medaka were exposed to individual compounds for 72 h, at concentrations ranging from 10 µg L(-1) to 10 mg L(-1). Lethal concentrations 50 % (LC50) were estimated at 840, 841 and 9,136 µg L(-1) for fluoxetine, sertraline and citalopram, respectively, while other compounds did not induce any significant increase in mortality. Analysis of the swimming behaviour of larvae, including total distance moved, mobility and location, provided an estimated lowest observed effect concentration (LOEC) of 10 µg L(-1) for citalopram and oxazepam, 12.2 µg L(-1) for cyamemazine, 100 µg L(-1) for fluoxetine, 1,000 µg L(-1) for sertraline and >10,000 µg L(-1) for valproate. Realistic environmental mixture of the six psychotropic compounds induced disruption of larval locomotor behaviour at concentrations about 10- to 100-fold greater than environmental concentrations.

Assessing the toxicity of sediments using the medaka embryo-larval assay and 2 other bioassays.

Sediments are sinks for aquatic pollutants, and analyzing toxicity in such complex matrices is still challenging. To evaluate the toxicity of bioavailable pollutants accumulated in sediments from the Bizerte lagoon (Tunisia), a novel assay, the medaka embryo-larval assay by sediment contact, was applied. Japanese medaka (Oryzias latipes) embryos were incubated in direct contact with sediment samples up to hatching. Lethal and sublethal adverse effects were recorded in embryos and larvae up to 20 d postfertilization. Results from medaka embryo-larval assay were compared with cytotoxicity (Microtox®), genotoxicity (SOS chromotest), and pollutant content of sediments. The results highlight differences in the contamination profile and toxicity pattern between the different studied sediments. A significant correlation was shown between medaka embryo-larval assay by sediment contact and SOS chromotest responses and concentrations of most organic pollutants studied. No correlation was shown between pollutant levels and Microtox. According to the number of sediment samples detected as toxic, medaka embryo-larval assay by sediment contact was more sensitive than Microtox, which in turn was more sensitive than the SOS chromotest; and medaka embryo-larval assay by sediment contact allowed sediment toxicity assessment of moderately polluted sediments without pollutant extraction and using an ecologically realistic exposure scenario. Although medaka embryo-larval assay by sediment contact should be tested on a larger sample set, the results show that it is sensitive and convenient enough to monitor the toxicity of natural sediments. Environ Toxicol Chem 2016;35:2270-2280. © 2016 SETAC.

Zebrafish Models for Human Acute Organophosphorus Poisoning.

Terrorist use of organophosphorus-based nerve agents and toxic industrial chemicals against civilian populations constitutes a real threat, as demonstrated by the terrorist attacks in Japan in the 1990 s or, even more recently, in the Syrian civil war. Thus, development of more effective countermeasures against acute organophosphorus poisoning is urgently needed. Here, we have generated and validated zebrafish models for mild, moderate and severe acute organophosphorus poisoning by exposing zebrafish larvae to different concentrations of the prototypic organophosphorus compound chlorpyrifos-oxon. Our results show that zebrafish models mimic most of the pathophysiological mechanisms behind this toxidrome in humans, including acetylcholinesterase inhibition, N-methyl-D-aspartate receptor activation, and calcium dysregulation as well as inflammatory and immune responses. The suitability of the zebrafish larvae to in vivo high-throughput screenings of small molecule libraries makes these models a valuable tool for identifying new drugs for multifunctional drug therapy against acute organophosphorus poisoning.