Urban sanitation is a major challenge during the rapid urbanization being experienced by developing countries, as a low sewerage infrastructure capacity and irregular onsite wastewater treatment raise the risk of surface water contamination. The application of specific sewage markers to characterize contaminant sources is therefore essential for managing urban sanitation issues. In this study, we investigated the concentrations of eight sewage markers (acetaminophen, caffeine, carbamazepine, cotinine, sulfamethoxazole, sulfapyridine, atenolol, and acesulfame) in various water sources within urban area of the Galle City, Sri Lanka. The total concentration of the eight markers was in the order of hospital discharge > sewage treatment plant (STP) influent > surface drainage system. Among the eight selected markers, acetaminophen was dominant in hospital discharge (70.2–123.6 µg/L) while caffeine was the largest contributor to STP influent (16.2–68.7 µg/L) and surface drainage (0.95–21.73 µg/L). We then proposed and tested a set of criteria for evaluating the applicability of markers, including removal efficiency, concentration magnitude, excretion rate, and wastewater burden. The labile markers caffeine and acetaminophen were suitable for characterizing domestic gray and black wastewater, respectively. These results imply that the city’s drainage system receives both domestic graywater and human excretion, likely due to insufficient on-site sanitation systems. The conservative marker carbamazepine was useful for tracking hospital residues over long distances; these results imply that hospital wastewater treatment was not working properly, accounting for pharmaceutical residues reaching surface water via a hidden discharges connected to the drainage system.

Estimating substance use in Japan traditionally depends on police seizure records and national self‐reporting surveys, which face substantial challenges due to social stigma. This study applies wastewater‐based epidemiology to overcome these challenges of monitoring illicit drug and legal stimulant use in a Japanese metropolitan area serving ∼1.8 million residents. Influent wastewater samples collected over 4 weeks in 2021 were analyzed for 29 substances. Methamphetamine was the only illicit drug consistently detected (consumption at 17.0 ± 5.1 mg/day/1000 people), reflecting its prevalence in Japan's drug scene and aligning with patterns in other East Asian countries. Ephedrine and pseudoephedrine, known precursors of methamphetamine were detected at high levels, suggesting their common use in legal medicines. Nicotine and methamphetamine consumption remained stable across weekdays and weekends. Higher ephedrine consumption during the lockdown period likely resulted from increased use of Kampo medicines to manage COVID‐19 symptoms. This study provides the first objective evidence of population‐level methamphetamine use in a large urban catchment of Japan, which is relatively low compared to other countries. The findings demonstrate the feasibility of wastewater analysis as a complementary surveillance approach to the existing system, enabling more responsive and evidence‐based drug policy.

Diagram showing PFAS occurrence in tap water in Ho Chi Minh City and their contribution to cumulative human health risk, with PFOS, PFOA, and PFBS identified as dominant contributors. Per- and polyfluoroalkyl substances (PFAS) are persistent and bioaccumulative contaminants of emerging concern in drinking water, posing potential risks to human health. This study evaluated the occurrence, concentration levels, and health risks of 12 PFAS compounds in household tap water from 24 districts in Ho Chi Minh City (HCMC), Vietnam, along with influent water from three major water supply plants. Between May and August 2022, a total of 72 tap water and 12 influent samples were collected and analyzed using solid-phase extraction and UPLC-MS/MS. Eight PFAS compounds were detected, with PFOS, PFBS, and PFOA found in all tap water samples. Total PFAS concentrations ranged from 0.74 to 6.01 ng/L (mean: 1.79 ± 1.41 ng/L). In several cases, treated water showed higher PFAS levels than influent water, suggesting contamination during treatment or distribution. Estimated daily intake (EDI) and hazard index (HI) calculations indicated PFOS as the dominant contributor to health risk, though HI values were below 1. Descriptive HQi-based contribution analysis identified PFBS, PFOS, and PFOA as the major contributors to cumulative non-carcinogenic risk. This study emphasizes the need for continued monitoring, regulatory action, and improved treatment processes to reduce PFAS exposure through tap water in urban environments.