Caffeine is a widespread pollutant in rivers and drinking water of a coastal tropical city (Esmeraldas, Ecuador).

Emerging contaminants, particularly pharmaceuticals, enter surface waters through untreated or partially treated wastewater and pose significant risks to human health and the environment due to their persistence in aquatic systems. This study evaluated the presence of diclofenac, acetaminophen, trimethoprim, sulfamethoxazole, and caffeine in surface and drinking water of Esmeraldas, Ecuador. Compounds were extracted using solid-phase extraction and detected by liquid chromatography and mass spectrometry. Caffeine was the most prevalent, detected in 66% of the samples, with significantly higher concentrations in surface waters than in domestic or commercial bottled water. It was also the only pharmaceutical detected in both domestic and commercial bottled water. Diclofenac and acetaminophen were detected less frequently (5% and 13% of samples, respectively), while trimethoprim and sulfamethoxazole were not detected. The maximum observed concentrations were 795 ng L-1 of caffeine, 895 ng L-1 of acetaminophen and 37.7 ng L-1 of diclofenac. This study highlights the importance of monitoring of PHs in surface and drinking waters to safeguard both public health and the environment.