The occurrence of antimicrobial residues and antimicrobial resistance genes in urban drinking water and sewage in Southern Brazil.

Antimicrobial resistance (AMR) is currently discussed as an important issue worldwide, and the presence of antimicrobial residues (ARs) and antimicrobial resistance genes (ARGs) in the environment, especially in the water sources, is a challenge for public health. This study was conducted to evaluate the occurrence and diversity of AR and ARG in water sources from an urban center, in Southern Brazil. A total of thirty-two water samples from drinking water treatment plants (24) and sewage systems (8) were collected during two annual samplings, winter and summer. The PCR was performed by 18 ARGs, and the detection of 47 ARs was performed by LC-MS/MS. All sewage samples presented carbapenemases, ESBL, and mcr-1 genes as well as quinolones and sulfamethoxazole residues. In drinking water, we just detected blaTEM and tetB genes and doxycycline residues in samples before treatment. This study provides data about AR and ARG in drinking water and sewage systems showing that these sources are important reservoirs of both. The limited effectiveness of wastewater treatment processes to remove mainly AR demonstrates the need to implement better protocols of disinfection, in order to limit the spread of AMR in the environment.

Identification of pesticides in water samples by solid-phase extraction and liquid chromatography-electrospray ionization mass spectrometry.

The Contaminants of Emerging Concern (CECs), including pesticides, have been a trending topic and Brazil is the country with the highest usage of pesticides worldwide. This study aimed to measure the presence of pesticide residues in the water from different sources in the city of Porto Alegre. We analyzed 55 samples from drinking water treatment plants, public water sites, and sewage treatment plants from winter 2018 to summer 2020 by solid-phase extraction and high-performance liquid chromatography-electrospray ionization mass spectrometry. Among 184 pesticides evaluated, 107 matched validation criteria (linearity, trueness, accuracy, repeatability, reproducibility) and 15 of them were detected in different water samples, including seven insecticides, five antifungals, and three herbicides, with a wide range of toxicity levels and noticeable seasonal differences. For the worst-case scenario evaluation, 20 out of 22 (90.9%) samples exceeded the Risk Quotient of 1. The sum of pesticide concentrations exceeded 100 ng L-1 in 66.7% of samples in February 19 and in 75% of samples in February 20 and the total pesticide concentration has reached the worrisome mark of 1615 and 954.96 ng L-1 respectively. Therefore, our results make evident the need to promote public policies to achieve better water quality monitoring. PRACTITIONER POINTS: Among 184 pesticides evaluated, 107 matched validation criteria (linearity, trueness, accuracy, repeatability, reproducibility). A total of 55 different water samples were analyzed, and 15 pesticides were detected and five quantified. For the worst-case scenario evaluation, 20 out of 21 samples exceeded the Risk Quotient of 1 on Feb/20. The pesticide concentrations sum exceeded 100 ng L-1 in 66.7% of samples on February 19 and in 75% of samples on February 20. It is mandatory to improve water monitoring to guide the development of public policies concerning its quality.