Comparative embryotoxicity of pulp mill extracts in rainbow trout (Oncorhynchus mykiss), American flagfish (Jordanella floridae) and Japanese medaka (Oryzias latipes)

Sex-Related Embryotoxicity of Pulp Mill Effluent Extracts in Medaka (Oryzias latipes) Female Leucophore-free FLFII Strain

The aim of the present study was to evaluate the effects of exposure to Chilean pulp mill effluent extracts on developing postfertilized medaka embryos before and after sex definition relative to sex steroids (testosterone and 17beta-estradiol) and a wood phytoestrogen (beta-sitosterol). Our study included 2 waterborne semichronic exposure experiments, using a 24-h post fertilization (hpf) unknown-sex FLFII (female leucophore free) group and a second 72-hpf FLFII phenotypic sex-identified group (male autofluorescence leucophore) strain of medaka embryos. Chronic exposure of both FLFII strain embryo groups showed similar delay in time to hatch and decreased hatchability. Teratogenic responses such as vertebral malformation (fusion, incomplete formation, and lack of vertebral formation process) and pericardial edema were observed in both experiments, with a high percentage related to FLFII fluorescent leucophore-identified males. In addition, high mortality associated with severe malformations was observed in male and female embryos exposed to testosterone. Our research has demonstrated that exposure to Chilean mill effluent extracts caused severe male medaka embryotoxicity (in postfertilized embryos) before and after sex definition and, irrespective of the experimental group and effluent treatment, suggests partial removal following secondary treatment. Furthermore, differences in the severity and type of teratogenic effects with previous experiments (d-rR medaka strain), are associated with the unique phenotypes of this medaka mutant strain. Environ Toxicol Chem 2021;40:2297-2305. © 2021 SETAC.

Morphometric analysis of developing zebrafish embryos allows predicting teratogenicity modes of action in higher vertebrates

The early identification of teratogens in humans and animals is mandatory for drug discovery and development. Zebrafish has emerged as an alternative model to traditional preclinical models for predicting teratogenicity and other potential chemical-induced toxicity hazards. To prove its predictivity, we exposed zebrafish embryos from 0 to 96 h post fertilization to a battery of 31 compounds classified as teratogens or non-teratogens in mammals. The teratogenicity score was based on the measurement of 16 phenotypical parameters, namely heart edema, pigmentation, body length, eye size, yolk size, yolk sac edema, otic vesicle defects, otoliths defects, body axis defects, developmental delay, tail bending, scoliosis, lateral fins absence, hatching ratio, lower jaw malformations and tissue necrosis. Among the 31 compounds, 20 were detected as teratogens and 11 as non-teratogens, resulting in 94.44 % sensitivity, 90.91 % specificity and 87.10 % accuracy compared to rodents. These percentages decreased slightly when referred to humans, with 87.50 % sensitivity, 81.82 % specificity and 74.19 % accuracy, but allowed an increase in the prediction levels reported by rodents for the same compounds. Positive compounds showed a high correlation among teratogenic parameters, pointing out at general developmental delay as major cause to explain the physiological/morphological malformations. A more detailed analysis based on deviations from main trends revealed potential specific modes of action for some compounds such as retinoic acid, DEAB, ochratoxin A, haloperidol, warfarin, valproic acid, acetaminophen, dasatinib, imatinib, dexamethasone, 6-aminonicotinamide and bisphenol A. The high degree of predictivity and the possibility of applying mechanistic approaches makes zebrafish a powerful model for screening teratogenicity.

Choriogenin transcription in medaka embryos and larvae as an alternative model for screening estrogenic endocrine-disrupting chemicals

This study assessed the transcription levels of estrogen-responsive genes, such as vitellogenins (Vtg1 and Vtg2), choriogenins (ChgL, ChgH, and ChgHm), cytochrome P450 aromatase (CYP19a1b), and ER subtypes (ERα, ERβ1, and ERβ2), in 7 days-post-fertilization (dpf) embryos and 9 and 12 dpf larvae of medaka (Oryzias latipes) exposed to estrogenic endocrine-disrupting chemicals (EDCs). The <5 h-post-fertilization embryos were exposed to EDCs such as 17β-estradiol (E2), p-n-nonylphenol (NP), and bisphenol A (BPA). In E2 (0.10-222 nM)-treated 7 dpf embryos and 9 or 12 dpf larvae, ChgL, ChgH, and ChgHm expression was up-regulated in a concentration-dependent manner. By contrast, interestingly, Vtg1 and Vtg2 expression was not induced in E2-treated 7 dpf embryos but was significantly induced in 9 and 12 dpf larvae, suggesting a developmental-stage-specific regulatory mechanism underlying Vtg expression. The maximum concentrations of NP (0.09-1.5 μM) and BPA (1.8-30 μM) up-regulated Chg expression in 9 or 12 dpf larvae, and the relative estrogenic potencies (REPs) of E2, NP, and BPA were 1, 2.1 × 10^-4, and 1.0 × 10^-5, respectively. Chg messenger RNA (mRNA) in medaka embryos and larvae can be used as a sensitive biomarker for screening potential estrogenic EDCs. Our assay system using embryos and larvae can be used as an in vivo alternative model because independent feeding stages (e.g., embryonic and early larval stages) are suitable alternatives.

Assessing wild fish exposure to ligands for sex steroid receptors from pulp and paper mill effluents in the Biobio River Basin, Central Chile

Bioactive substances in the Biobio River Basin in Chile were examined by deploying Semi Permeable Membrane Devices (SPMDs) upstream and downstream of 4 pulp mill effluent discharges. Androgenic and estrogenic activity of SPMD extracts were then evaluated using in vitro fish sex steroid receptor binding assays. The results indicated the occurrence of estrogenic type compounds associated with one of the mill discharges. A significant correlation among the presence of these compounds, an increase in gonadosomatic index GSI and induction of hepatic EROD activity of two native fish species was observed. However, no significant presence of mature oocytes in female gonads was detected. Although EROD induction was observed in sites impacted by mill effluents, an increase of its activity occurred towards the downstream areas, suggesting other non-mill sources. More research is needed to understand the environmental changes in context of the new technological improvements in treatment systems to MBBR (Moving Bed Biofilm Reactor) recently implemented by the pulp mill industries.

The impact of kraft pulping effluent on egg survival and hatching success in two species of Clupeiformes (Teleostei)

The anchoveta (Engraulis ringens) and sardine (Strangomera bentincki) are coastal pelagic species with important spawning areas off the coast of Chile. The discharge of secondary-treated effluents from a kraft pulp plant near one of these spawning areas has raised environmental concerns. Therefore, effluent effects on the development of anchoveta and sardine eggs were assessed by in vitro exposure. Eggs were sampled between 2007 and 2010 off Talcahuano, Chile. Subsequent toxicity tests (96 h duration, 12 °C) were performed using increasing effluent concentrations, a filtered seawater control, and two potassium dichromate concentrations (to verify consistent embryonic sensitivity). Egg mortality and hatching success were evaluated. For anchoveta, mortality (9.9 ± 7.1%) did not significantly differ among groups in five toxicity tests except the final toxicity test that showed significant differences in mortality (5.6% control vs 27.8% in 100% effluent). For sardines, no differences in mortality existed between the effluent dilutions (2.6 ± 3.6%) and control (6.3 ± 3.9%). Notably, anchoveta egg survival and hatching success rates were inconsistent, i.e., the highest rates of hatching failure occurred on the same sampling date with the highest rates of survival for the 100% effluent group (72%). In conclusion, the obtained results indicate that (i) anchoveta egg mortality and hatching failure increase only under 100% effluent exposure, coinciding with decreased egg quality near the end of spawning season and (ii) high effluent dilutions not significantly increase sardine and anchoveta egg mortalities. Nevertheless, the recorded adverse effects to the hatching process should be studied in greater detail, particularly considering interspecific variability and the complexity of reproductive processes, especially during early development.

Nanosecond pulsed electric field incorporation technique to predict molecular mechanisms of teratogenicity and developmental toxicity of estradiol-17β on medaka embryos

Herein, we propose using a nanosecond pulsed electric field (nsPEF) technique to assess teratogenicity and embryonic developmental toxicity of estradiol-17β (E₂ ) and predict the molecular mechanisms of teratogenicity and embryonic developmental defects caused by E₂ on medaka (Oryzias latipes). The 5 hour post-fertilization embryos were exposed to co-treatment with 10 μm E₂ and nsPEF for 2 hours and then continuously cultured under non-E₂ and nsPEF conditions until hatching. Results documented that the time to hatching of embryos was significantly delayed in comparison to the control group and that typical abnormal embryo development, such as the delay of blood vessel formation, was observed. For DNA microarray analysis, 6 day post-fertilization embryos that had been continuously cultured under the non-E₂ and nsPEF condition after 2 hour co-treatments were used. DNA microarray analysis identified 542 upregulated genes and one downregulated gene in the 6 day post-fertilization embryos. Furthermore, bioinformatic analyses using differentially expressed genes revealed that E₂ exposure affected various gene ontology terms, such as response to hormone stimulus. The network analysis also documented that the estrogen receptor α in the mitogen-activated protein kinase signaling pathway may be involved in regulating several transcription factors, such as FOX, AKT1 and epidermal growth factor receptor. These results suggest that our nsPEF technique is a powerful tool for assessing teratogenicity and embryonic developmental toxicity of E₂ and predict their molecular mechanisms in medaka embryos.

Transient exposure to environmental estrogen affects embryonic development of brown trout (Salmo trutta fario)

Transient exposure of brown trout embryos from fertilization until hatch (70 days) to 17β-estradiol (E2) was investigated. Embryos were exposed to 3.8 and 38.0 ng/L E2 for 2h, respectively, under four scenarios: (A) exposure once at the day of fertilization (0 days post-fertilization, dpf), (B) once at eyeing stage (38 dpf), (C) weekly exposure until hatch or (D) bi-weekly exposure until hatch. Endpoints to assess estrogen impact on embryo development were fertilization success, chronological sequence of developmental events, hatching process, larval malformations, heart rate, body length and mortality. Concentration-dependent acceleration of development until median hatch was observed in all exposure scenarios with the strongest effect observed for embryos exposed once at 0 dpf. In addition, the hatching period was significantly prolonged by 4-5 days in groups receiving single estrogen exposures (scenarios A and B). Heart rate on hatching day was significantly depressed with increasing E2 concentrations, with the strongest effect observed for embryos exposed at eyeing stage. Estrogenic exposure at 0 dpf significantly reduced body length at hatch, not depending on whether this was a single exposure or the first of a series (scenarios A and D). The key finding is that even a single, transient E2 exposure during embryogenesis had significant effects on brown trout development. Median hatch, hatching period, heart rate and body length at hatch were found to be highly sensitive biomarkers responsive to estrogenic exposure during embryogenesis. Treatment effects were observable only at the post-hatch stage.

Developmental toxicity of PAH mixtures in fish early life stages. Part II: adverse effects in Japanese medaka

In aquatic environments, polycyclic aromatic hydrocarbons (PAHs) mostly occur as complex mixtures, for which risk assessment remains problematic. To better understand the effects of PAH mixture toxicity on fish early life stages, this study compared the developmental toxicity of three PAH complex mixtures. These mixtures were extracted from a PAH-contaminated sediment (Seine estuary, France) and two oils (Arabian Light and Erika). For each fraction, artificial sediment was spiked at three different environmental concentrations roughly equivalent to 0.5, 4, and 10 μg total PAH g(-1) dw. Japanese medaka embryos were incubated on these PAH-spiked sediments throughout their development, right up until hatching. Several endpoints were recorded at different developmental stages, including acute endpoints, morphological abnormalities, larvae locomotion, and genotoxicity (comet and micronucleus assays). The three PAH fractions delayed hatching, induced developmental abnormalities, disrupted larvae swimming activity, and damaged DNA at environmental concentrations. Differences in toxicity levels, likely related to differences in PAH proportions, were highlighted between fractions. The Arabian Light and Erika petrogenic fractions, containing a high proportion of alkylated PAHs and low molecular weight PAHs, were more toxic to Japanese medaka early life stages than the pyrolytic fraction. This was not supported by the toxic equivalency approach, which appeared unsuitable for assessing the toxicity of the three PAH fractions to fish early life stages. This study highlights the potential risks posed by environmental mixtures of alkylated and low molecular weight PAHs to early stages of fish development.

Dehydroabietic acid (DHAA) alters metabolic enzyme activity and the effects of 17β-estradiol in rainbow trout (Oncorhynchus mykiss)

Recent studies have shown that dehydroabietic acid (DHAA), a resin acid present in pulp and paper mill effluent, affects liver energy metabolism and may have anti-estrogenic effects in fish. A chronic-exposure toxicity experiment using immature rainbow trout (Oncorhynchus mykiss) was conducted in order to assess the endocrine disrupting and liver metabolic effects of the model estrogen 17β-estradiol (E2) and the wood extractives DHAA and β-sitosterol (BS), regularly present in pulp and paper mill effluents. Exposure to 5ppm of E2 significantly increased hepatosomatic index (HSI), vitellogenin (VTG) and plasma sorbitol dehydrogenase (SDH). This latter effect was reduced by mixing E2 with DHAA, indicating that DHAA does not cause its endocrine disrupting effects indirectly due to liver damage. Exposure to 0.5ppm of DHAA as well as all the DHAA mixed treatments caused significant increases in liver citrate synthase (CS), activity after 7 days, however, the fish returned to control values by 28 days. Results indicate that DHAA may alter metabolic enzyme activity as well as alter the effects of E2 in juvenile rainbow trout.

Biological removal of phyto-sterols in pulp mill effluents

Phyto-sterols and extractives found in pulp mill effluents are suspected to cause endocrine abnormalities in receiving water fish. The control of sterols in pulp mill effluents through biological secondary wastewater treatment was studied using two lab-scale bioreactor systems. After achieving a stable performance, both bioreactor systems successfully removed (>90%) sterols and the estimated biodegradation was up to 80%. Reactor 1 system operating at 6.7 ± 0.2 pH effectively treated pulp mill effluent sterols spiked up to 4500 μg/L in 11 h HRT and 11 day SRT. However, Reactor 2 system operating at 7.6 ± 0.2 pH performed relatively poorly. Retention time reductions beyond critical values deteriorated the performance of treatment systems and quickly reduced the sterols biodegradation. The biodegradation loss was indicated by mixed liquor sterols content that started increasing. This biodegradation loss was compensated by the increased role of bio-adsorption and the overall sterols removal remained relatively high. Hence, a relatively small (20-30%) loss in the overall sterols removal efficiency did not fully reflect the associated major (60-70%) loss in the sterols biodegradation because the amount of sterols accumulated in the sludge due to adsorption increased so the estimate of sterols removal through adsorption increased from 30-40% to 70-80% keeping the overall sterols removal still high.

Betulinol and wood sterols in sediments contaminated by pulp and paper mill effluents: dissolution and spatial distribution

The goal was to determine dissolution potency of betulinol and wood sterols (WSs) from pulp and paper mill-contaminated sediments and the current stratification for assessment the load due to potential erosion in the river-like watercourse. Both compounds are wood extractives, which may be toxic to benthos and fish. This research continues a study in which other wood extractives, resin acids and their derivative, retene, were analysed. Sediments were collected from 1, 3.5, 12, 15, and 33 km downstream from the pulp and paper mills, and from 2 upstream reference sites. The dissolution potency into sediment-water elutriates (1 + 4 v/v) was studied by two agitation times and temperatures. The vertical amounts of extractives were determined from the uppermost 20 cm of sediment. The amounts of extractives potentially released were estimated from the sediment layers 0-2 and 2-5 cm by using spatial interpolation. According to the interpolation, the total amount of betulinol and β-sitosterol was calculated as kg/ha in the whole sediment area. Significant concentrations of betulinol (1,666 μg/g, dw) and WSs (2,886 μg/g, dw) were measured from the sediments. According spatial interpolation, the highest calculated amount of betulinol (4,726 kg/ha) and that of the most abundant WS, β-sitosterol (3,571 kg/ha), were in the lake where the effluents were discharged. In the dissolution experiment, the highest concentration of betulinol in sediment (0-10 cm) and elutriate was 412 μg/g (dw) and 165 μg/l, respectively. For WSs, concentrations were 768 μg/g (dw) in sediment and 273 μg/l in elutriate. In a worst-case scenario, betulinol may be desorbed to water in concentrations which are hazardous to aquatic animals. Instead WSs are not a risk in this study area. The amount of desorption varied depending on the concentration of contaminants in sediment, the nature of disturbance, and the sediment organic carbon content.

Biotoxicity evaluation of coking wastewater treated with different technologies using Japanese medaka (Oryzias latipes)

The potential biotoxicity to the environment should be addressed during wastewater treatment. In this study, biotoxicity of coking wastewater effluent from MBR, Fenton, electro-Fenton and coagulation treatment processes was evaluated using embryos and larvae of Japanese medaka (Oryzias latipes). The acute toxicity based on 96-h larval mortality as well as the chronic toxicity based on embryo hatching, larvae swim-up failure, growth, and sexual ratio were determined. The results showed that different treatment processes have various biotoxicity levels. The acute toxicity of Fenton and electro-Fenton effluents was much higher than that of MBR and coagulation. For the chronic toxicity, the effluent of the Fenton/electro-Fenton process displayed lower embryo hatching, larvae survival and growth in comparison with the effluents of MBR and coagulation. No endocrine disruption was detected in MBR, Fenton and electro-Fenton effluents, but was contained in the coagulation effluent. The biotoxicity test indicated that the effluent of MBR was very safe for the environment. The toxicological indices were necessary for ecological safety maintenance in the industrial wastewater treatment.

DISCRISET: a battery of tests for fast waste classification--application of tests on waste extracts

The Hazardous Waste Directive (HWD, Council Directive 91/689/EC, 1991) provides a framework for classification of hazardous waste, based on 15 Hazard (H)-criteria. For complex wastes the HWD foresees the application of toxicity tests on the waste material itself to assess its toxic properties. However, these proposed test methods often involve mammalian testing, which is not acceptable from an ethical point of view, nor is it feasible economically. The DISCRISET project was initiated to investigate the use of alternative chemical and biological fast screening tests for waste hazard classification. In the first part of the project, different methods were reviewed and a testing strategy was proposed to minimize time and cost of analysis by a tiered approach. This includes as a first tier chemical analysis followed by a general acute toxicity screen as a second tier and as a third tier mechanistic toxicity tests to assess chronic toxicity (genotoxicity, hormone disturbance, teratogenic effects, immunologic activity). In this phase of the project, selected methods were applied to 16 different waste samples from various sources and industries. The first tier chemical tests are recommended for the full characterization of the leachate fraction (inorganics) but not for the organic fraction of samples. Here the chemical characterization is only useful if toxic content is known or suspected. As second tier the fast bacterial test Microtox is validated as a general toxicity screen for the organic fraction (worst case organic extract). Samples that are not classified in tier 1 or 2 are then further investigated in the third tier by the mechanistic toxicity tests and tested for their potential chronic toxicity: immune activity (TNF-α upregulation) is indicative for corrosive, irritating or sensitising effects (H4/H8/H15), reproductive effects (H10) are indicated by hormone disturbance and early life stage abnormalities in fish larvae when exposed to the extracts and mutagenicity and carcinogenicity (H7, H11) are indicated by SOS response induction and increased mutation frequency in the Ames test when exposed to the extracts. Results indicate that the combination of chemical tests and bioassays allows important hazardous properties to be addressed and the tiered approach ensures that the tests are performed quickly and economically. The suggested strategy provides a solid and ethical alternative to the methods described in the HWD and is a vast improvement on the current, arbitrary classification.

The acute and chronic effects of endosulfan pulse-exposure on Jordanella floridae (Florida flagfish) over one complete life-cycle

Endosulfan is an organochlorine pesticide, which is used worldwide and has known toxic effects on non-target organisms including fish. This research investigated the acute and chronic effects of pulse-exposed endosulfan on Florida flagfish (Jordanella floridae). A 4-h pulse-exposure of endosulfan to larval flagfish caused a significant increase in mortality after 96 h at nominal concentrations equal to or greater than 100 μg/L. Some of the acute sub-lethal observations included hyperactivity, convulsions, and axis malformation. Seven-eight day old post-hatch flagfish were pulse-exposed for 4h to endosulfan and then monitored over one full life-cycle for chronic effects on growth, reproduction, and survivability. There were no growth or reproductive effects of endosulfan pulse-exposure up to the highest exposure concentration of 10.8 μg/L. Thus, the life-cycle 4-h pulse-exposure no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) were 3.3 and 10.8 μg/L endosulfan, respectively, based on significantly higher larval and juvenile mortality.