Christian J. Wilson

Aquatic persistence of eight pharmaceuticals in a microcosm study

The persistence of eight pharmaceuticals from multiple classes was studied in aquatic outdoor field microcosms. A method was developed for the determination of a mixture of acetaminophen, atorvastatin, caffeine, carbamazepine, levofloxacin, sertraline, sulfamethoxazole, and trimethoprim at microg/L levels from surface water of the microcosms using solid phase extraction and high-performance liquid chromatography-ultraviolet (HPLC-UV) and liquid chromatography tandem mass spectrometry (LC-MS-MS). Half-lives in the field ranged from 1.5 to 82 d. Laboratory persistence tests were performed to determine the relative importance of possible loss processes in the microcosms over the course of the study. Results from dark control experiments suggest hydrolysis was not important in the loss of the compounds. No significant differences were observed between measured half-lives of the pharmaceuticals in sunlight-exposed pond water and autoclaved pond water, which suggests photodegradation was important in limiting their persistence, and biodegradation was not an important loss process in surface water over the duration of the study. Observed photoproducts of several of the pharmaceuticals remained photoreactive, which led to further degradation in irradiated surface waters.

Effects of pharmaceutical mixtures in aquatic microcosms.

Pharmaceuticals have a wide range of biological properties and are released into the environment in relatively large amounts, yet little information is available regarding their effects or potential ecological risks. We exposed outdoor aquatic microcosms to combinations of ibuprofen (a nonsteroidal anti-inflammatory drug), fluoxetine (a selective serotonin reuptake inhibitor), and ciprofloxacin (a DNA gyrase-inhibiting antibiotic) at concentrations of 6, 10, and 10 microg/L, respectively (low treatment [LT]); 60, 100, and 100 microg/L, respectively (medium treatment [MT]); and 600, 1,000, and 1,000 microg/L, respectively (high treatment [HT]). We maintained these concentrations for 35 d. Few responses were observed in the LT; however, effects were observed in the MT and HT. Fish mortality occurred in the MT (<35 d) and in the HT (<4 d). Phytoplankton increased in abundance and decreased in diversity (number of taxa) in the HT, with consistent trends being observed in the MT and LT. Zooplankton also showed increased abundance and decreases in diversity in the HT, with consistent trends being observed in the MT. Multivariate analyses for zooplankton and phytoplankton suggested interactions between these communities. Lemna gibba and Myriophyllum spp. showed mortality in the HT; growth of L. gibba was also reduced in the MT. Bacterial abundance did not change in the HT. All responses were observed at concentrations well below the equivalent pharmacologically active concentrations in mammals. Although the present data do not suggest that ibuprofen, fluoxetine, and ciprofloxacin are individually causing adverse effects in surface-water environments, questions remain about additive responses from mixtures.

Response of the zooplankton community and environmental fate of perfluorooctane sulfonic acid in aquatic microcosms

Little is known regarding perfluorooctane sulfonic acid (PFOS) toxicity to freshwater organisms. This field evaluation aims to assess the toxicological risk associated with exposure to PFOS across levels of biological organization. The analysis of variance study was conducted in replicate (n = 3) 12,000 L outdoor microcosms. Multivariate techniques were used to assess the response of zooplankton community structure and dynamics, as well as a floating macrophyte, Lemna gibba. The zooplankton community was significantly affected (p < 0.05) by the treatment regime given by the Monte Carlo permutations for all sampling times. A community-level no-observable-effect concentration ([NOEC]community) of 3.0 mg/L was determined for the 35-day study, however, longer term studies are recommended. The most sensitive taxonomic groups, Cladocera and Copepoda, were virtually eliminated in 30 mg/L treatments after 7 d. The 42-d 50% inhibition concentration (IC50) for L. gibba frond number was 19.1 mg/L and the NOEC was 0.2 mg/L. Furthermore, we investigated the persistence of PFOS over 285 d in microcosms under natural conditions. Perfluorooctane sulfonic acid concentration showed no drastic reduction in any treatment microcosm over the entire study period, confirming that this compound undergoes little degradation in aquatic systems. Presently, there appears to be little hazard to these freshwater organisms at reported environmental concentrations.