An investigation into the acute and chronic toxicity of eleven pharmaceuticals (and their solvents) found in wastewater effluent on the cnidarian, Hydra attenuata Brian Quinn ⁎ , François Gagné, Christian Blaise St-Lawrence Centre, Environment Canada, 105 McGill, Montréal, Québec, Canada H2Y 2E7 ARTICLE INFO ABSTRACT Article history: Received 10 July 2007 Received in revised form 16 August 2007 Accepted 23 August 2007 Available online 10 October 2007 Summary: Pharmaceuticals previously identified in the effluent from the wastewater treatment plant (WWTP) in Montreal discharging into the St. Lawrence river, were tested for acute and chronic toxicity using the cnidarian Hydra attenuata. Acute toxicity was based on the established technique looking at morphological changes in the Hydra, while recently developed endpoints of feeding behaviour, attachment and growth (hydranth number) were used to measure chronic effects. The compounds under investigation (ibuprofen, naproxen, gemfibrozil, bezafibrate, carbamazepine, sulfamethoxazole, sulfapyridine, oxytetracycline, novobiocin, trimethoprim and caffeine) were tested individually in controlled laboratory exposures with LC 50 and EC 50 results calculated. All compounds tested had relatively high LC 50 values with gemfibrozil, ibuprofen and naproxen having the lowest at 22.36 mg/L and EC 50 values based on morphology of 1.18 to 2.62 mg/L (all concentrations are nominal). The EC 50 values based on feeding were similar to those based on morphology but with increased sensitivity for carbamazepine, bezafibrate and novobiocin. A trend of a reduction in feeding with deterioration in morphology was observed in the Hydra, with the exception of novobiocin, where a lower than expected EC 50 of 13.53 mg/L was found with no negative effect on morphology. Significant reductions in attachment and hydranth number were seen at concentrations of 1 and 5 mg/L for gemfibrozil and ibuprofen respectively. A toxicity threshold (TT) of 320 μg/L was calculated for ibuprofen, only a factor of 10 2 or 10 higher than the concentration found in the effluent in the present study (1.19 μg/L) and in other Canadian effluents studied (22 μg/L [Brun GL, Bernier M, Losier R, Doe K, Jackman P, Lee HB, Pharmaceutically active compounds in Atlantic Canadian sewage treatment plant effluents and receiving waters and potential for environmental effects as measured by acute and chronic aquatic toxicity. Environ Toxicol Chem 2006; 25(8): 2163–2176.] respectively. Using EU directive 93/67/EEC the pharmaceuticals under investigation can be classified as toxic (gemfibrozil, ibuprofen and naproxen), harmful (carbamazepine, bezafibrate, sulfapyridine, oxytetracycline and novobiocin) and non-toxic (sulfamethoxazole, trimethoprim and caffeine) and their potential toxicity for the aquatic environment is discussed. © 2007 Elsevier B.V. All rights reserved. Keywords: Hydra attenuata Pharmaceuticals Solvents Chronic effects Feeding SCIENCE OF THE TOTAL ENVIRONMENT 389 (2008) 306 – 314 ⁎ Corresponding author. Birches Lane, Blackrock, Dundalk, Co. Louth. Ireland. Tel.: +353 87 2860874; fax: +353 42 9323063. E-mail address: quinnbrian@gmail.com (B. Quinn). 0048-9697/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2007.08.038 available at www.sciencedirect.com www.elsevier.com/locate/scitotenv