2004 年 27 巻 11 号 p. 707-714
In recent years, antibiotics resident in sewage and in the water environment have become an emerging public concern in many developed countries. However, limited knowledge is available on the occurrence of antibiotics in sewage and discharge from wastewater treatment plants (WWTPs) in Japan. Moreover, little is known on the significance of their occurrence in the water environment from the viewpoints of biological adverse effects. The objectives of this research were, therefore, to determine the occurrence of selected antibiotics, namely levofloxacin (LVFX) and clarithromycin (CAM). That are commonly used in Japan, in discharge from WWTPs and then to evaluate their possible effects on algal growth. Therefore, we developed a novel analysis method for LVFX and CAM in wastewater by LC/MS/MS whose detection limits and recovery ratios are 2-3ng·l-1 and 53-87%, respectively. We also conducted algal growth inhibition tests using Pseudokirchneriella subcapitata, and results showed that the EC50s of LVFX and CAM are 1200μg·l-1 and 11μg·l-1, LOECs are 630μg·l-1 and 6.3μg·l-1, and NOECs are 310μg·l-1 and 3.1μg·l-1, respectively, LVFX and CAM concentrations in secondary effluent of five WWTPs that use the activated sludge process ranged from 152-323ng·l-1 and 303-567ng·l-1, respectively, which indicates that the PEC/PNEC ratio of LVFX is less than one but that of CAM exceeds two at the maximum secondary effluents if a safety factor of ten is considered. This suggests a possibility of algal growth inhibition due to CAM in WWTP discharge in the case of insufficient dilution of the receiving waters.