Pharmaceutical products including antimicrobials, drugs and daily necessities, are collectively referred to as “Pharmaceuticals and Personal Care Products (PPCPs).” PPCPs may have physiological activity even at low concentration, causing concerns about effect on aquatic ecosystems. Regarding antimicrobials as a type of PPCPs, several studies have indicated the measurements of antimicrobial concentrations in the environment (e.g. sewage, treated wastewater, recycled water, environmental water, and sludge).
In some cases, a part of sewage sludge (biomass) that is generated from sewage treatment is reused as agricultural fertilizers through anaerobic digestion and composting. The extent to which PPCPs are degraded in the sewage treatment process or in the sewage sludge digestion process varies by the type of PPCPs. For example, among other antimicrobials, most sulfonamides are decomposed, while fluoroquinolones, such as ofloxacin and norfloxacin, reside in sludge at high concentrations without being degraded. The biodegradation process of PPCPs is affected by water temperature. The removability of PPCPs is affected by treatment conditions in the sewage treatment process, such as hydraulic retention time, the processing concentration and retention time of activated sludge. To further promote removal, research is in progress to improve the removability of antimicrobials using membrane bioreactor. Many research activities are also undertaken both in Japan and overseas to improve efficiency in removing antimicrobials, by introducing ozone and advanced oxidation process. It is required to identify the current status of discharge and developmental trends in Japan.
A study that measured the concentrations of antimicrobials detected in Japanese urban rivers, based on influent sewage at sewage treatment plants, reported that the actual measurements of ciprofloxacin and clarithromycin indicated certain similarity to concentrations expected from the volumes of shipment or sales of these antimicrobials, and pointed out that it may be possible to predict sewage concentrations of antimicrobials based on their volumes of shipment or sales. The study reported that, for example, ciprofloxacin and clarithromycin were contained in sewage at the respective concentrations of 51 to 442 ng/L and 886 to 1,866 ng/L. However, no research results have been reported that these antimicrobials in the environment are affecting the health of humans and other living things.
A research group funded by a Ministry of Health, Labour and Welfare research grant began work in the current fiscal year on a study entitled “Research to Establish Methods of Surveying Antimicrobial-resistant Bacteria and Antimicrobials in the Environment,” which will run from 2018 to 2020 and be led by Hajime Kanamori. One of the objectives of the study is to establish a method of evaluating antimicrobial resistance in environmental water and it will incorporate surveillance aimed at studying the true extent of antimicrobial-resistant bacteria and residual antimicrobials in environmental water in Japan. Hopes are high that this study will help to advance research in this area.