Acetaminophen (CAS 103-90-2) is one of the most used pharmaceuticals around the world. In Korea, it was produced 1,069 tons in 2003. This chemical is not eliminated in wastewater treatment plant and may flow into the ecosystem through various routes. Therefore, there is a possibility that it can make an adverse effect on aquatic organisms. To examine its ecological toxicity, we used three native Korean aquatic invertebrate species, Daphnia sp., Chironomus yoshimatsui, and Ephemera orientalis. The acute toxicity on Daphnia sp. was moderately high, and its 48 hour median immobilization concentration (EC50-immobilization) was 51.7 mg/L. On the other side, the reproductive toxicity was very high, and its EC50 of 25 day reproduction test was 0.005 mg/L. In E. orientalis egg hatching test, the median egg hatching inhibition concentration was 0.199 mg/L. C. yoshimatsui was most tolerant to acetaminophen, in which 48 hour median lethal concentration (LC50) was 400.0 mg/L and 45 day median emergence inhibition concentration (EC50-emergence) was 45.27 mg/L. From this results, we concluded that acetaminophen is hazardous to freshwater macroinvertebrates, especially to water flea. Therefore we need to study more about pharmaceuticals' ecotoxicology including acetaminophen and to assess their potential ecological risk.

Traditionally oxygen demands and concentrations of variable pollutant have been used for the assessment of lentic or lotic water quality. But there is a high probability that newly synthesized chemicals flow into the aquatic ecosystem, and it is very hard to investigate that many kinds of chemicals interact even though they exit at lower level than legal standards. As a consequence of limitation of chemical assessment for media, biological assessment techniques for accepters which are affected by pollutants or physicochemical properties have been developed. However, it still has several weak points because it does not have the ecological relevances using the internationally standard test species which do not inhabit Korea. Besides, the assessment using just one or two species may have a possibility of overestimation or underestimation because a certain species can be extremely sensitive or insensitive to a certain chemical or physicochemical property. Therefore, we used four kinds of indigenous aquatic invertebrates to assess the local stream quality and integrated their responses into a new index which ranges from 0(bad) to 1(good). We assessed four streams throughout Ansan and one stream in Gapyeong, and index values of two streams near residential and industrial area in Ansan were under 0.9 and the others were over 0.9.