Effect assessment of reclaimed waters and carbamazepine exposure on the thyroid axis of Xenopus laevis: Gene expression modifications.

Reclaimed water (RW) obtained from wastewater treatment plants (WWTP) is used for irrigation, groundwater recharge, among other potential uses. Although most pollutants are removed, traces of them are frequently found, which can affect organisms and alter the environment. The presence of a myriad of contaminants in RW makes it a complex mixture with very diverse effects and interactions. A previous study, in which tadpoles were exposed to RW and RW spiked with Carbamazepine (CBZ), presented slight thyroid gland stimulation, as suggested by the development acceleration of tadpoles and histological findings in the gland provoked by RW, regardless of the CBZ concentration. To complement this study, the present work analysed the putative molecular working mechanism by selecting six genes coding for the thyroid-stimulating hormone (TSHß), thyroid hormone metabolising enzymes (DIO2, DIO3), thyroid receptors (THRA, THRB), and a thyroid hormone-induced DNA binding protein (Kfl9). Transcriptional activity was studied by Real-Time PCR (RT-PCR) in brains, hind limbs, and tails on exposure days 1, 7, and 21. No significant differences were observed between treatments for each time point, but slight alterations were noted when the time response was analysed. The obtained results indicate that the effects of RW or RW spiked with CBZ are negligible for the genes analysed during the selected exposure periods.

The effect of PFOs on the uptake and translocation of emerging contaminants by crops cultivated under soil and soilless conditions.

The Mediterranean is a region of substantial agriculture production that faces concurrent environmental stresses and freshwater pollution given the occurrence of emerging contaminants (ECs). Among these pollutants, the surface-active substances have been suggested to enhance the bioavailability of other ECs. This research evaluates a comparative uptake and translocation assessment of irrigation exposure to atenolol (ATN, 60 µg/L), carbamazepine (CBZ, 60 µg/L) and triclosan (TCS, 30 µg/L) alone vs. these combined with perfluorooctanesulfonic acid (PFOS, 10 µg/L) under semifield (i.e., soil experimental set) vs. hydroponics (i.e., soilless experimental set) growing conditions with lettuce, radish and tomato plants. Both experimental sets revealed efficient root uptake and translocation for the three ECs regardless of their co-existence with PFOS. The overall results of the uptake and translocation of the ECs in the lettuce and tomato plants suggested a simultaneous treatment-plant organ interaction, which was not affected by PFOS being present in both experimental sets. PFOS in irrigation water did not increase cellular perviousness to the other three ECs. These observations support the hypothesis of factors other than PFOS being responsible for the differential bioaccumulation and translocation potentials seen in both experimental sets. However, the radish plants co-irrigated with PFOS brought about increased movement of ECs from roots to aerial parts, more specifically ATN and CBZ in the soil experimental set, and ATN and TCS in the soilless set. These results support the notion that factors inherent to the physiological characteristics of this root vegetable contributed to ECs' increased tendency to move from roots to aerial parts. Despite the three ECs efficiently accumulating, the risk to humans from eating the edible parts of these plants grown under soil or soilless conditions was low.

The role of PFOS on triclosan toxicity to two model freshwater organisms.

Surface-active substances may enhance the bioavailability of certain pollutants by modifying the permeability of cell membranes. However, they could also interact in a positive manner by increasing toxicity to aquatic organisms. A comparative effects assessment of waterborne exposure to triclosan (TCS) alone vs. combined with perfluorooctanesulfonic acid (PFOS) was herein investigated in daphnids (Daphnia magna) and medaka (Oryzias latipes) early life stages (ELS) using a battery of non-invasive behavioral, physiological and anatomical endpoints. Additionally, TCS bioaccumulation was evaluated in medaka embryos to help discern differences in effects caused by either, changes in TCS permeability or by a positive interaction with PFOS. The TCS analytical measurements in the medaka ELS exposure media revealed fast dissipation with half-lives < 12 h. The D. magna immobilization and feeding inhibition assays suggested an increased response when TCS (≥200 and 37.50 µg/L, respectively) was co-exposed with PFOS. Concentrations <800 µg TCS/L did not affect medaka ELS. However, exposures to ≥400 µg TCS/L + PFOS had effects on the embryo and eleutheroembryo viability. The morphometric analysis of the embryonic gallbladder area and the oxidative stress, determined in vivo by the manifestation of reactive oxygen species (ROS), revealed a hormetic response in both experimental sets. The TCS + PFOS experimental set generally resulted in increased gallbladder areas and ROS activity levels compared to those quantified in the corresponding TCS set. The bioaccumulation studies in the medaka embryos revealed comparable TCS levels regardless of PFOS presence. Without disregarding any TCS's enhanced bioavailability caused by the surface-active substance, overall results primarily indicate increased biological effects of TCS due to a potentiation action of PFOS as a binary mixture with TCS.

Acute and chronic toxicity of emerging contaminants, alone or in combination, in Chlorella vulgaris and Daphnia magna.

This work presents the toxicity results of different compounds classified as emerging contaminants on primary producers and primary consumers in the aquatic compartment. The objectives were to (1) obtain acute and chronic toxicity results for algae and Daphnia magna using standardised or currently used tests, (2) study the relationship between the effects on the impaired feeding rate for daphnia and the effects of reproduction and (3) examine the responses on daphnia and algae after binary combinations of environmentally relevant compounds and perfluorooctane sulfonate (PFOS). Toxicity data on personal care products (PCPs), not reported in the scientific literature up to now, are presented. The results confirmed that the Daphnia feeding bioassay can be a sensitive, ecologically relevant endpoint to detect sublethal effects and could complement the information obtained with the reproduction test on Daphnia. The results also suggested that the concomitant occurrence of PFOS and other emerging contaminants in the aquatic compartment could affect the toxicity of some compounds according to their lipophilicity.

Use of a novel battery of bioassays for the biological characterisation of hazardous wastes.

Four toxicity bioassays were used for the biological characterisation of nine hazardous wastes and extracts. This evaluation included conventional and novel bioassays, and combined in vivo and in vitro tests in order to facilitate the effect characterisation. This test battery incorporated different relevant taxonomic groups for the aquatic compartment and covered several ecotoxicological endpoints. The toxicity bioassays used for this characterisation were the acute immobilisation daphnia test, an acute toxicity test with larvae of Xenopus laevis, an in vitro test with the fish cell line RTG-2 comprising endpoints for cellular defence and viability, and finally the DR-CALUX assay to detect dioxin-like compounds. The aim of this study is to contribute to the development of a cost-effective battery of toxicity tests for the acute screening of hazardous and toxic wastes for the aquatic compartment. For this objective, the correlations between toxicity data derived from all bioassay were studied using a multivariate analysis, including the Principal Component Analysis. The results showed that Daphnia and Xenopus were effective assays to detect toxicity and they could be incorporated to a screening test battery. On the other hand, the toxicity results with the in vitro test RTG-2 showed that this test could be a good alternative to in vivo tests, demonstrating an acceptable sensitivity for toxicity detection and contributing other advantages as reducing assays cost and animal testing. Finally DR-CALUX test implemented the tests-batteries in the screening of hazardous wastes when there is a suspicious that dioxin-like compounds are presented in the samples.