Masahiro Otaki

Alcohol consumption poses a significant public health risk but alcohol may also be used as an anti-anxiolytic by the public. Understanding the actual change in alcohol consumption behaviour is therefore important to formulate appropriate public health policies. This study, for the first time, employed wastewater-based epidemiology (WBE) to estimate alcohol consumption in a catchment of approximately 1.8 million inhabitants in the Kanto region, Japan. Twenty-four-hour composite wastewater samples were collected over four weeks from September to October 2021, during and after a COVID-19 lockdown period. Twenty-seven influent wastewater samples were analysed for ethyl sulfate (EtS), an alcohol biomarker, using the Liquid Chromatography-Tandem Mass Spectrometry (LC-MSMS) method and used to estimate alcohol consumption. EtS was detected in all samples, with concentrations ranging from 11.8 to 45.5 µg/L. The average estimated alcohol consumption in the study population was 52.9 ± 15.3 mL/day/person, which is higher than wastewater data from other countries. Alcohol consumption remained stable throughout the week. Additionally, consumption decreased after the lockdown (p < 0.001), and a strong positive correlation was observed between alcohol intake and daily reported COVID-19 cases (r = 0.735, p < 0.001), likely reflecting population mobility and behavioural responses to restrictions. Higher alcohol consumption during the lockdown was likely due to increased use in private settings rather than public spaces. This study provides the first objective evidence of alcohol consumption prevalence in Japan and warrants a broader wastewater monitoring program to inform policies reducing alcohol-related harm.

Pit latrines—the simplest on-site sanitation system—have been extensively used in developing countries in Asia for a long time. However, pit latrines are pollution and health risk hotspots that can cause widespread contamination. It is preferable to upgrade them to septic tanks, which are more advanced, effective, and simple alternatives. This study encourages the transition from pit latrines to septic tanks by making people aware of the health and environmental risks associated with the use of pit latrines. As decisions about sanitation technologies are mostly made by individual households, it is important to find communication tools for the average household to understand the basic information to make informed decisions. To this end, this study used augmented reality as a communication tool. A survey was conducted with Sri Lankan households that use pit latrines, and experiments were carried out in a university laboratory in Japan. The use of augmented reality increased people’s understanding of the environmental and health risks of pit latrines. This understanding was retained for some time because people found the use of augmented reality ‘enjoyable’. Hence, our findings contribute to the promotion of the transition from pit latrines to septic tanks in low- and middle-income countries.

Treatment with ultraviolet (UV) light has been shown to be effective for disinfection of pathogens. For pathogenic risk management, it would be effective to estimate the UV sensitivity of unknown pathogenic microorganisms from their nucleotide sequences. In this study, we designed and used synthetic DNA molecules, 100–150 bases in length, to investigate not only the DNA sequences but also the secondary structures of the DNA as determinants of UV sensitivity of microorganisms. We showed that dimer-forming DNA by UV irradiation was undetectable by quantitative polymerase chain reaction (qPCR) when performed on all DNA bases. The undetectability ratio of PCR after UV irradiation indicated that UV reactivity tends to increase with the number of consecutive thymine pairs within DNA. In addition, UV reactivity was not influenced by increasing the number of complementary bonds in the DNA and the estimated free energy, indicating that complementary bonds in the DNA have no influence on the UV reactivity. The results of this study provide important information about the necessary factors determining UV sensitivity of microorganisms such as the number of consecutive thymine pairs within the DNA, which was the main driver regardless of the presence of secondary structures.

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.

The disinfection efficiency of ozonation by ozonated water on human norovirus genogroup-II (HNoV-II) and MS2 as a surrogate was investigated using plaque assay and/or quantitative PCR (qPCR). The qPCR combining propidium monoazide (PMA) pretreatment was used to evaluate the damage to the viral capsids, which showed that the PMA pretreatment could be applied to HNoV-II but not to MS2 because PMA inhibited qPCR even in undamaged MS2. The ozonation reduced the viability of MS2 by more than 99.9999% (= 6 log; CT = 0.036 mgXmin/L) and the qPCR detection of HNoV-II by approximately 90–95%. However, it is assumed that significant damage to the HNoV-II capsid did not occur in all inactivated viruses.

This study investigated how chlorine inactivates and damages Escherichia coli cells. E. coli that had transformed to express enhanced green fluorescent protein (EGFP) at the cytoplasm was treated with chlorine. Damage to the cell membrane and cell wall was analyzed by measuring the fluorescence intensity of the leaked EGFP, then accounting for the fluorescence deterioration. At pH 7, E. coli was lethally damaged after treatment with chlorine, but significant leakage of EGFP was not observed. In contrast, significant leakage of EGFP was observed at pH 9, even though E. coli was not as inactivated as it was at pH 7. Flow cytometry was used to confirm the fluorescence intensity of the remaining EGFP inside the cells. No significant fluorescence loss was observed in the cells at pH 7. However, at pH 9, the fluorescence intensity in the cells decreased, indicating leakage of EGFP. These results suggest that hypochlorous acid inactivates E. coli without damaging its cell membrane and cell wall, whereas the hypochlorite ion inactivates E. coli by damaging its cell membrane and cell wall. It was possible to confirm the chlorine damage mechanism on E. coli by measuring the fluorescence intensity of the leaked EGFP.

In the area where household water use exceeds the capacity of the public water supply, rainwater is considered as one of the alternative water resources. Many researchers studied rainwater potential to cover the specific value of water demand in households having the average catchment area, so that the estimated potential expresses that of the average population. In this research, the possibility of rainwater use for toilets was investigated more realistically using the probability distributions of water demand and catchment area, and precipitation in case of Hanoi, Vietnam. Monte Carlo simulations were conducted throughout this simulation and the distribution of the possibility of rainwater use was estimated. The effect of household size and seasonal variations on the potential of rainwater utilization was also assessed. These results showed that our new approach exhibited that approximately 60% of the households failed to achieve the potential that was estimated using the conventional approach. Therefore, our new approach should be useful to understand the manner in which the potential of rainwater utilization differs in a given area, and it could be applied to other areas for consideration on the rainwater use potential and the suitable tank size when the distributions of variables and precipitation are clear.