Formation of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) in the electrochemical oxidation of polluted waters with pharmaceuticals used against COVID-19

Detrimental impact of photo-Fenton treated COVID-19 drugs on liver function: A thorough investigation in Danio rerio

The widespread usage of dexamethasone, metformin, and paracetamol during the COVID-19 pandemic has resulted in the pervasive contamination of aquatic ecosystems, necessitating the development of effective degradation strategies. Among these, photocatalysis has emerged as a potential solution, yet concerns persist regarding forming degradation by-products that may exhibit enhanced toxicity relative to the parent compounds. Despite the importance of this issue, research on the toxicity of these by-products remains limited, particularly concerning their effects on aquatic organisms. This study addressed these gaps by examining the efficacy of Fe-pillared clays (Fe-PILCs) combined with hydrogen peroxide (H2O2) in degrading dexamethasone, metformin, paracetamol, and their mixtures. Additionally, the study evaluated the toxicity of the by-products in zebrafish liver tissue, revealing variations in toxicity before and after degradation. Results show complete degradation of metformin and dexamethasone within 10 and 420 min, respectively, while paracetamol removal ranged from 88.27 % to 99.67 % over 60 min. Moreover, ternary mixtures achieved mineralization levels of 71.13 %-85.24 % after 7 h. Regarding toxicological impact, although zebrafish liver tissue exposed to treated drugs exhibited oxidative damage and increased gene expression related to apoptosis, energy regulation, endoplasmic reticulum stress, and inflammation, these effects were less severe than those observed before treatment.

Investigating the presence of dioxins in drinking water: implications for public health

The presence of highly toxic dioxins, specifically polychlorinated dibenzo-p-dioxins (PCDDs), in drinking water is a matter of great concern due to their long-lasting nature and harmful effects. In this study, we detected three out of the five dioxin congeners: 2, 3, 7, 8-tetrachlorodibenzodioxin (TCDD), 1, 2, 3, 7, 8-pentachlorodibenzo-p-dioxin (PeCDD), and octachlorodibenzo-p-dioxin (OCDD). The investigation revealed that three dioxins were present in water samples of winter season, while TCDD and OCDD were found in the summer season. The geometric mean concentrations of PCDDs were 229.9 ng/L (winter) and 108.4 ng/L (summer), exceeded the maximum contaminant level of 30 pg/L set by the USEPA in surface water. The estimated daily intake of PCDDs for residents through drinking water was 273.97 ng-WHO2005-TEQ/kg/days during winter and 78.875 ng-WHO2005-TEQ/kg/days during summer. Our study emphasizes the urgent need for further research on persistent organic pollutants in drinking water to safeguard public health and community well-being.

Electrochemical degradation of key drugs to treat COVID-19: Experimental analysis of the toxic by-products formation (PCDD/Fs)

Drug consumption has grown exponentially in recent decades, particularly during the COVID-19 pandemic, leading to their presence in various water sources. In this way, degradation technologies for pollutants, such as electrochemical oxidation (ELOX), have become crucial to safeguard the quality of natural resources. This study has as its starting point a previous research, which demonstrated the efficacy of ELOX in the removal of COVID-19 related-drugs, such as dexamethasone (DEX), paracetamol (PAR), amoxicillin (AMX), and sertraline (STR), using the electrolytes NaCl and Na2SO4. The present research aims to study the potential risks associated with the generation of toxic by-products, during the ELOX of cited drugs, specifically focusing on the highly chlorinated persistent organic pollutants (POPs), such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Dioxins and furans can be formed potentially in electrochemical systems from precursor molecules or non-precursor molecules in chloride medium. First, the degradation of the parent compounds was found to be complete. At this point, a comprehensive investigation was conducted to identify and analyse the by-products formed during the degradation process; precursors of PCDD/Fs, such as chlorophenols or hydroquinones were identified. Additionally, in continuation of the previous study, PCDD/Fs congeners were investigated, revealing elevated concentrations; the highest concentration obtained was for the congener 1,2,3,4,6,7,8-HpCDF (234.6 pg L-1 in NaCl) during degradation of the AMX. Finally, an assessment of the toxicity based on TEQ values was conducted, with DEX exhibiting the highest concentration among all compounds: 30.1 pg L-1 for NaCl medium. Therefore, the formation of minor by-products should not be underestimated, as they can significantly enhance the toxicity of the final sample, so the selection of the appropriate remediation technology, as well as the optimization of experimental operating variables, is determining in the treatment of pharmaceutical-contaminated waters.