Compounds of emerging concern : occurrence, sources and environmental risk of pharmaceuticals in surface waters in Mexicali and its surrounding valley as a demonstration site in Latin America / [recurso electrónico] Melissa Valdez Carrillo ; director, Concepción Carreón Diazconti ; subdirector, Leif Abrell

Maestría y Doctorado en Ciencias e Ingeniería.

Tesis (Doctorado)--Universidad Autónoma de Baja California. Facultad de Ingeniería, Mexicali, 2019.

Incluye referencias bibliográficas.

Reports concerning the quantitative analysis of Pharmaceutical Active Compounds (PhACs) in the Latin American (LATAM) ecosystems are limited even though they are essential to determine the occurrence, sources and fate of pharmaceuticals in the environment and, ultimately, assess the risk of exposure of organisms and their habitats. Therefore, this dissertation includes an exploratory analysis of a decade of available data on the occurrence and sources of PhACs in LATAM. Said analysis is focused on the aquatic environment and involves a critical assessment of the current situation of PhACs in LATAM, compared with other regions of the world. References were obtained through a comprehensive revision of the state of the art in different sources of scientific information, such as academic and electronic database and search engines. The selected information was subjected to data management and statistical analyses. To elucidate the complexities of this endeavor, this investigation was strengthened with a study case on the occurrence and sources of PhACs, including an approach to the Environmental Risk Assessment (ERA) for aquatic organisms, in a specific site of LATAM, the city of Mexicali and its surrounding agricultural valley, in northwestern México. A total of 23 sites were selected in a non-parametric approach, including the influents and effluents of three Waste Water Treatment Plants (WWTPs), the three local river channels, and several irrigation canals and agricultural drains along the city and the valley. Twelve PhACs were selected taking care to consider the therapeutic classes of worldwide concern, i.e., antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), psychiatric drugs, lipid regulators, beta-blockers, and synthetic hormones. PhACs in environmental samples were determined using Solid Phase Extraction (SPE) and Liquid Chromatography tandem Mass Spectrometry (LC/MSMS) with electrospray ionization. Results from the critical analysis indicate that in LATAM there were only 66 investigation reports available along the last decade (2007-2017), whereas the quantification of PhACs in diverse environmental compartments was documented in barely ten countries of this region. Surface water was the most frequently analyzed compartment while Ibuprofen (IBF) and Diclofenac (DCF) were found to be the most investigated and detected compounds in LATAM. Wastewater, treated and untreated (no statically significant difference found between the two) proved to be the main source of PhACs in the environment. The concentration observed in LATAM were constantly higher
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than those reported elsewhere for all the analyzed compounds. On the other hand, only five out of twelve PhACs were detected in the aquatic environment of Mexicali and its surrounding valley, being Sulfamethoxazole (SMX) and Carbamazepine (CBZ) the most detected (85% of the times) followed by IBF, DCF and MTP, all showing much lower frequencies of detection. Results indicate that substantial concentrations of PhACs (up to 1705 ng/L of IBF and 830 ng/L of SMX) reached the aquatic environment during the spring of 2015 through the discharges of WWTPs effluents. Once in the environment, the PhACs concentrations decreased with distance from the source, although small amounts of all five compounds dissolved in the waters of the Nuevo River were inadvertently transferred toward the Salton Sea basin (USA). This situation also seems to occur in the opposite direction, when the waters of the Colorado River enter Mexican territory carrying some dissolved compounds. In general, the local WWTPs were able to reduce the concentrations of NSAIDs in their effluents, but not those from other compounds. Nevertheless, IBP was found as far south as the estuary zone of the Gulf of California probably due to additional not-identified sources. Additionally, concentrations of SMX where constantly higher than those reported elsewhere (0.2-830.9 ng/L), marking it as the compound of maximum environmental concern in the vicinity of Mexicali. ERA for the three key aquatic organisms in the trophic chain (algae, daphnia and fish) using the three most likely scenarios (single compound, mixing of compounds and dilution factor over a mixing) showed that only SMX posed high risk for algae, which resulted the most sensitive organism under each scenario. The rest of the compounds mostly posed low to medium risk, at the worst, for the three organisms and scenarios during the spring of 2015.