Chromium (Cr) is an element present in nature in mineral form. It has a dual effect, both as an essential micronutrient and a carcinogenic agent depending on its chemical form and concentration. It is present in various environmental matrices such as water, soil, and air, coming from natural and anthropogenic sources, and causes harmful effects on biota, ecosystems, and even human beings. This study's objective was to evaluate chromium toxicity and teratogenicity in zebrafish embryos of Danio rerio exposed to chromium through the D. rerio teratology assay (DarTA) test by evaluating spine malformations. To this end, the chromium toxicity curve was calculated from zebrafish embryos exposed to potassium dichromate (K2Cr2O7), and the probit test was used to establish the mean lethal concentration (LC50) and three subtoxic concentrations LC25, LC12.5, and LC6.25 to evaluate the teratogenicity. The results showed that potassium dichromate was statistically positive for the teratogenic effect at the three highest concentrations evaluated. Potassium dichromate exposure causes abnormal embryonic development and teratogenic effects, including severe heart defects in zebrafish embryos. Therefore, we conclude that potassium dichromate is toxic to the zebrafish developmental stages. The finding that potassium dichromate is teratogenic in zebrafish embryos suggests that this metal should be tested and evaluate potential risk in mammalian systems.

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Background Due to the problems we face today, such as wastewater pollution of aquifers and climate change, it is necessary to search for environmental solutions that help us minimize this problem. An alternative solution might be the cultivation of microalgae that are efficient in the purification of wastewater, removal of greenhouse gases and production of biomass that can be used for the production of biofuels such as biodiesel, methane, bioethanol, among others. The aim of this work is to cultivate five strains of microalgae native in Mexico: Chlorella miniata, Coelastrella sp., Desmodesmus quadricauda, Neochloris oleoabundans and Verrucodesmus verrucosus. The cultivations were performed using municipal wastewater and a foliar fertilizer with the further purpose of assessing their capacity to produce various types of biomass, in particular lipids. Methods The experiments were carried out using triplicate 16-L glass bioreactors assays with a 12:12 light–darkness cycle at 25 °C ± 1 under constant aeration. Every 3rd day, a 1-mL sample was taken to determine cell density. In the stationary growth phase, each culture was harvested by sedimentation and lipid content analysis was performed. The biomass with the highest concentration of total lipids was subjected to an analysis of the methyl esters of fatty acids. Results An ANOVA test showed significant differences between the growth rates (F = 6.8, p = 0.0001). The species that were able to produce biomass with the highest concentrations of total lipids were Coelastrella sp. with 44–46%; Verrucodesmus verrucosus with 43–44% and Neochloris oleoabundans 35–37%. As the analysis of the methyl esters of fatty acids showed, the species Coelastrella sp. and V. verrucosus produced lipids composed of 82.9% and 91.28% of fatty acids, respectively, containing C16–C18 carbon chains. Conclusions All the species used in the present study were able to grow on wastewater and produce high concentrations of lipids. Therefore, the demands for biodiesel production could be met in the immediate future after continuing working with different microalgae species. Therefore, it is necessary to determine their adaptation potential to grow on contaminated effluents and produce lipids that can be used for the benefit of people and environment.

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Waste electrical and electronic equipment (WEEE) has brought negative effects to the environment produced by the materials that compose them. The proper implementation of management plans of WEEE should integrate measures to prevent, mitigate and correct these affectations. As an initial step, it is necessary to make a diagnosis of the current situation of WEEE management which is the objective of this work. The studied zone was composed by the municipalities of Tampico, Ciudad Madero and Altamira located in southeast Tamaulipas, Mexico. The descriptive analysis of technical and regulatory aspects of the current management system in the study area was developed, including generation rates and analysis of waste streams. Among the main results, the generation of WEEE was estimated in 2040.38 tons/year for 2013, distributed in the municipalities of Tampico with 830.93 tons/year, Altamira with 650.18 tons/year, and Ciudad Madero with 559.27 tons/year. This calculation was estimated using Mexico's WEEE generation indicators. The analysis of waste streams includes five categories of WEEE, Televisions with 61% of the total generation, followed by sound devices with 18%, personal computers with 17%; mobile phones with 2% as well as fixed phones with 1%. In the study area, reports of Tampico's municipality indicated that 96 tons of WEEE was collected in the city of Tampico in 2013. In México, the national legislation considers WEEE in the category of waste requiring special handling (WRSH), however, an inadequacy exists in the environmental laws about the specific classification of this kind of debris that makes their effective management more difficult. No companies who provide a management or treatment operations for WEEE are reported in Tampico, or in the near region. In addition, despite an initial interest for the municipality to attend the WEEE problematic, a lack of sensibility of the population exists in the absence of environmental education programs.