Removal of Chromium (III) and Reduction in Toxicity in a Primary Tannery Effluent Using Two Floating Macrophytes.

Trivalent chromium (Cr(III)) is a contaminant with toxic activity. Its presence in waters and soils is usually related to industrial activities such as tanneries. The aim of this study was to compare the removal of Cr(III) in hydroponic solutions and tannery effluents using two floating macrophytes: Salvinia auriculata and Eichhornia crassipes. First, to determine the chromium removal capacity in solution and the bioaccumulation factor (BAF) in tissues of each plant, experiments were set up with contaminated solutions with Cr(III) concentrations of 2, 5, 10, 20, and 40 mg/L. Subsequently, both plant species were exposed to a primary tannery effluent contaminated with 12 mg/L of Cr(III) in order to study the removal capacity of organic and inorganic matter, as well as the acute toxicity in the water flea (Daphnia magna) and genotoxicity in zebrafish (Danio rerio). Tests carried out on nutrient solutions revealed that both plants have a high capacity for removing Cr(III) in solution. The BAF in tissues was higher in E. crassipes compared to S. auriculata. In the experiments with a tannery effluent, both species presented low nutrient and organic matter removal efficiency, but they showed good Cr(III) removal capacity, with average reduction values of 57% for S. auriculata and 54% for E. crassipes after 72 h of exposure. E. crassipes contributed most to the reduction in acute toxicity in D. magna, while S. auriculata did not show a similar effect. However, both plant species managed to reduce the genotoxicity marker in D. rerio when compared with the initial effluent and the control.

Physical Evidence of Oil Uptake and Toxicity Assessment of Amphiphilic Grafted Nanoparticles Used as Oil Dispersants.

Herein, we report the toxicity evaluation of a new prototype dispersant system, silicon dioxide nanoparticles (NPs) functionalized with (3-glycidoxypropyl)triethoxysilane (GPS) and grafted poly(ε-caprolactone)-block-poly[oligo(ethylene glycol)methyl methacrylate mono-methyl ether] (NP-PCL-POEGMA). This serves as a follow up of our previous study where grafted silicon dioxide NPs functionalized with GPS and grafted hyperbranched poly(glycidol) (NP-HPG) were evaluated for reducing the toxicity in embryo, juvenile, and adult fish populations. In this study, the NP-HPG sample is used as a baseline to compare against the new NP-PCL-POEGMA samples. The relative size was established for three NP-PCL-POEGMA samples via cryogenic transmission electron microscopy. A quantitative mortality study determined that these NPs are non-toxic to embryo populations. An ethoxyresorufin-O-deethylase assay was performed on these NP-PCL-POEGMA samples to test for reduced cytochrome P450 1A after the embryos were exposed to the water-accommodated fraction of crude oil. Overall, these NP-PCL-POEGMA NPs better protected the embryo populations than the previous NP-HPG sample (using a protein activity end point), showing a trend in the right direction for prototype dispersants to replace the commercially utilized Corexit.

Towards regulation of Endocrine Disrupting chemicals (EDCs) in water resources using bioassays - A guide to developing a testing strategy.

Endocrine disrupting chemicals (EDCs) are found in every environmental medium and are chemically diverse. Their presence in water resources can negatively impact the health of both human and wildlife. Currently, there are no mandatory screening mandates or regulations for EDC levels in complex water samples globally. Bioassays, which allow quantifying in vivo or in vitro biological effects of chemicals are used commonly to assess acute toxicity in water. The existing OECD framework to identify single-compound EDCs offers a set of bioassays that are validated for the Estrogen-, Androgen-, and Thyroid hormones, and for Steroidogenesis pathways (EATS). In this review, we discussed bioassays that could be potentially used to screen EDCs in water resources, including in vivo and in vitro bioassays using invertebrates, fish, amphibians, and/or mammalians species. Strengths and weaknesses of samples preparation for complex water samples are discussed. We also review how to calculate the Effect-Based Trigger values, which could serve as thresholds to determine if a given water sample poses a risk based on existing quality standards. This work aims to assist governments and regulatory agencies in developing a testing strategy towards regulation of EDCs in water resources worldwide. The main recommendations include 1) opting for internationally validated cell reporter in vitro bioassays to reduce animal use & cost; 2) testing for cell viability (a critical parameter) when using in vitro bioassays; and 3) evaluating the recovery of the water sample preparation method selected. This review also highlights future research avenues for the EDC screening revolution (e.g., 3D tissue culture, transgenic animals, OMICs, and Adverse Outcome Pathways (AOPs)).

Toxicity assessment of a novel oil dispersant based on silica nanoparticles using Fathead minnow.

Oil spill accidents are a major concern for aquatic organisms. In recent history, the Deepwater Horizon blowout spilled 500 million liters of crude oil into the Gulf of Mexico. Corexit 9500A was used to disperse the oil since it was the method approved at that time, despite safety concerns about its use. A better solution is necessary for dispersing oil from spills that reduces the toxicity to exposed aquatic organisms. To address this challenge, novel engineered nanoparticles were designed using silica cores grafted with hyperbranched poly(glycidol) branches. Because the silica core and polymers are known to be biocompatible, we hypothesized that these particles are nontoxic to fathead minnows (Pimephales promelas) and would decrease their exposure to oil polyaromatic hydrocarbons. Fathead minnow embryos, juveniles and adult stages were exposed to the particles alone or in combination with a water-accommodated fraction of oil. Acute toxicity of nanoparticles to fish was tested by measuring mortality. Sub-lethal effects were also measured including gene expression of cytochrome P450 1a (cyp1a) mRNA and heart rate in embryos. In addition, a mixture of particles plus the water-accommodated fraction was directly introduced to adult female fathead minnows by gavage. Three different nanoparticle concentrations were used (2, 10, and 50 mg/L) in either artificial fresh water or the water-accommodated fraction of the oil. In addition, nanoparticle-free controls were carried out in the two solutions. No significant mortality was observed for any age group or nanoparticle concentration, suggesting the safety of the nanoparticles. In the presence of the water-accommodated fraction alone, juvenile and adult fathead minnows responded by increasing expression of cyp1a. The addition of nanoparticles to the water-accommodated fraction reduced cyp1a gene expression in treatments. Heart rate was also restored to normal parameters in embryos co-exposed to nanoparticles and to the water-accommodated fraction. Measurement of polyaromatic hydrocarbons confirmed their presence in the tested solutions and the reduction of available PAH in WAF treated with the nanoparticles. Our findings suggest the engineered nanoparticles may be protecting the fish by sequestering polyaromatic hydrocarbons from oil, measured indirectly by the induction of cypa1 mRNAs. Furthermore, chemical analysis showed a reduction in PAH content in the water accommodated fraction with the presence of nanoparticles.