Summary and Conclusions

A reconnaissance of pharmaceutical chemicals and metabolites in urban streams and an advanced wastewater treatment facility was conducted on the west side of the Portland, Oregon, metropolitan area during low-flow conditions in July of 2002. Filtered water samples were analyzed for 21 target analytes using a solid-phase-extraction procedure followed by high-performance liquid chromatography and mass spectrometric detection. Only 6 of the target compounds were detected in the 10 stream or river sites that were sampled. Among the urban stream sites, the only compounds detected were cotinine (a metabolite of nicotine), caffeine, and acetaminophen. The highest concentration in any stream or river sample was for caffeine in Fanno Creek at 0.314 µg/L, but the next highest concentration was almost an order of magnitude lower at 0.046 µg/L for carbamazepine in the Tualatin River downstream of two wastewater treatment facility outfalls. All compound concentrations measured in this study were consistent with the range of concentrations reported in a 1999–2000 national survey of pharmaceutical compounds in United States streams by USGS, but maximum concentrations in this study were about an order of magnitude or more lower. Although this study is only a reconnaissance for the occurrence and concentrations of selected pharmaceuticals in Tualatin River basin streams, it appears that few pharmaceuticals are present in these streams, and when present, their concentrations are low. Furthermore, limited literature data suggest that the dry-weather concentrations of some compounds detected in this study are not high enough to be of ecological concern. Insufficient information is available, however, to fully assess the true ecological risk, including those associated with storm-related conditions and potential spills or accidental releases.

Fifteen pharmaceuticals and metabolites were detected in untreated municipal wastewater, but most were efficiently removed through treatment. Only five compounds were detected in treated effluent from the Durham treatment facility (carbamazepine, cotinine, ibuprofen, metformin, and sulfamethoxazole), and two of those (ibuprofen and metformin) were detected in only one of two duplicate effluent samples. Of these compounds, only carbamazepine is somewhat resistant to removal through wastewater treatment, with an apparent removal of only 18 percent; all other detected compounds had at least a 77 percent estimated removal rate. The apparent removal rates determined in this study are consistent with some previous studies of pharmaceutical chemicals in wastewater treatment facilities, although published studies differ widely on the removal rates of carbamazepine and acetaminophen. Results indicate that wastewater treatment facilities are the primary sources of the low concentrations of carbamazepine and cotinine measured in Tualatin River samples. Published research indicates that the dry-weather concentrations of carbamazepine, acetaminophen, and sulfamethoxazole found in Tualatin River basin samples are unlikely to be toxic to the several plankton and freshwater snail species used as test organisms.

Several of the pharmaceutical chemicals and metabolites included in this study, either singly or in combination, show some potential to be useful tracers of human-related contamination of streams. Although caffeine and cotinine appear to be good indicators of a wide variety of sources that can occur in urban areas, they are not good indicators of any single sewage-related source, for example, unless that source is large enough to overcome the smaller background sources. If present along with caffeine, 1,7-dimethylxanthine (a caffeine metabolite) might indicate the presence of untreated wastewater; in contrast, the absence of the metabolite might help rule out a wastewater source, treated or untreated, because caffeine and 1,7-dimethylxanthine are effectively removed via wastewater treatment. Acetaminophen, carbamazepine, and sulfamethoxazole show some potential as tracers for specific types of contamination, either because of high concentrations in raw wastewater (acetaminophen) or because of incomplete removal by wastewater treatment (carbamazepine, sulfamethoxazole). Ibuprofen also has a high concentration in raw wastewater and potentially incomplete removal in wastewater treatment, but is not an ideal candidate because the analytical test method used in this study gave imprecise results for this compound. Additional research is needed to fully determine the potential value of these or other pharmaceutical chemicals and metabolites as tracers for stream contamination. Other potential tracers such as optical brighteners, fragrance compounds, and surfactants also merit further consideration.