Biol. Pharm. Bull. 29(1) 183—186 (2006)

tered in the database exceeds 20000000. Approximately 50000—70000 are usually utilized for the purpose of manufacturing pharmaceutical and personal care products (PPCP) and life related materials in Japan. In recent years, various pharmaceutical chemicals have been detected in river water, treated wastewater, and hospital wastewater in western countries, and together with endocrine disrupting compounds, have attracted attention as new environmental pollutants. Drugs prescribed in hospitals and pharmacies are excreted into feces and urine or discarded into toilets and transferred to sewage. Studies have shown that portions of these drugs are not eliminated in wastewater treatment plants and remain in the discharged water. A concern has arisen about their influences on aquatic organisms and humans due to the formation and acquisition of a tolerance of various pathogenic microorganisms to anti-microbial drugs, the mixture of pharmaceutical chemicals at negligible concentrations in raw water for water supply, and exposure to these chemicals. To solve these problems, there are the following two laws. Unlike the Law Concerning the Examination and Regulation of Manufacture, etc., of Chemical Substances for the purpose of preventing environmental pollution by chemical substances that harms conventional human health, the Pollutant Release and Transfer Register (PRTR) law was therefore recently enforced. This PRTR law attempts to maintain the environment by controlling chemical substances discharged into the environment, and also their harmfulness and biological effects. The authors have noticed the inhibition of the respiration testing method (No. 209) of activated sludge (AS) as the decomposer, which is one of the 10 kinds of biological-effect testing methods determined by preservation. We previously established the calculation method for the IC50 of chemical substances, and the IC50 of chemicals and marketed products have been calculated. Not only us, but also many other researchers have calculated the IC50 to evaluate the toxicity of chemical substances using AS, but the mechanism of the oxygen uptake rate (OUR) inhibition has remained unclear. As a basic study to clarify the mechanism of the OUR inhibition of AS by chemical substances, we previously evaluated the relationship between the so-called biosorption, which is the affinity of chemical substances to AS, and the OUR, and observed more a significant OUR inhibition by chemical substances that are more markedly biosorbed. It is important to analyze factors affecting the elimination of pharmaceutical chemicals by the AS method, which is the main wastewater treatment. Therefore, in this study, we evaluated the influences of representative pharmaceutical chemicals among PPCP on the OUR of AS in test tubes. As a result, a correlation was observed between the protein binding of pharmaceutical chemicals and the OUR of AS as well as biosorption, which provided useful information for the elimination of pharmaceutical chemicals from wastewater.