Under the guidance of the World Health Organization (WHO), 41 nations have devel- oped pandemic preparedness plans describing the role different organizations will play when confronted with an influenza pandemic [European Influenza Surveillance Scheme (EISS) 2007; Mounier-Jack et al. 2007]. The plans aim to maintain essential services, reduce disease transmission and the socioeconomic consequences of a pandemic, and minimize the number of infectious cases, hospitaliza- tions, and deaths (EISS 2007; Mounier-Jack et al. 2007). The WHO has strongly recommended the use of the antiviral Tamiflu, produced and distributed by F. Hoffmann-La Roche Ltd. (Basel, Switzerland), as the primary choice for combating an influenza pandemic (WHO 2006a). Tamiflu was recommended because a) there is low natural viral resistance (Aoki et al. 2007; Roberts 2001); b) it is easy to administer orally via capsule; c) it is systemi- cally active; and d) it is effective against char- acterized influenza A and B viruses (Ward et al. 2005; WHO 2006b). International stockpiles of influenza A antivirals have been growing rapidly since 2005 (Figure 1), and most countries are stockpiling sufficient quan- tities of antiviral to treat 25% of their popula- tion (Department of Health and Human Services 2006; Ferguson et al. 2006; Roche 2007). Stockpiles are anticipated to continue to increase toward a 50% coverage goal in some countries. In addition, stockpiles are likely to diversify, incorporating additional neuraminidase inhibitors (NAI) such as zanamivir (Relenza; GlaxoSmithKline, London, UK) (Ferraris et al. 2005) and peramivir (Biocryst Pharmaceuticals, Cary, NC, USA) (Smee and Sidwell 2002), as well as traditional antivirals such as amantadine and rimantadine (WHO 2007). The United Kingdom has stockpiled 14.6 million courses of Tamiflu, equating to nearly 11 metric tons of oseltamivir ethylester-phos- phate (OE-P), all of which is expected to be used for treatment during the 9- to 12-week period of a pandemic. OE-P use has been identified as a potentially unacceptable risk, and various potential effects and exposures are associated with oseltamivir carboxylate (OC) (Singer et al. 2007). The following cri- teria have been used to assess the risks posed by OE-P use during an influenza pandemic: Environmental Health Perspectives • VOLUME 116 | NUMBER 11 | November 2008 1563 Research Address correspondence to A.C. Singer, Centre for Ecology & Hydrology, Oxford Mansfield Rd., Oxford OX13SR, UK. Telephone: 44 (0)1865 281630. Fax: 44 (0)1865 281696. E-mail: acsi@ceh. ac.uk We thank the Environmental Knowledge Transfer Network, the Worshipful Company of Water Conservators, and the Chartered Institution of Water & Environmental Management for financial support of the workshop. Several authors (A.B., A.B.C., A.J., A.S., A.T., C.A., C.J.K., J.F., J.O., J.O.S., M.J.D., N.R., P.M., S.K., S.J., S.T., and T.H.) work for, have worked for, or have received money or in-kind support from phar- maceutical companies or other industries that sell products of direct relevance to the issues discussed in this article. The remaining authors declare they have no competing financial interests. The freedom to design, conduct, interpret, and publish this research was not compromised by any sponsor. Received 30 January 2008; accepted 30 May 2008. Meeting Report: Risk Assessment of Tamiflu Use Under Pandemic Conditions Andrew C. Singer, 1 Bruce M. Howard, 2 Andrew C. Johnson, 3 Chris J. Knowles, 2 Simon Jackman, 2 Cesare Accinelli, 4 Anna Barra Caracciolo, 5 Ian Bernard, 2 Stephen Bird, 6 Tatiana Boucard, 7 Alistair Boxall, 8 Jayne V. Brian, 9 Elise Cartmell, 10 Chris Chubb, 11 John Churchley, 12 Sandra Costigan, 13 Mark Crane, 14 Michael J. Dempsey, 15 Bob Dorrington, 16 Brian Ellor, 17 Jerker Fick, 18 John Holmes, 19 Tom Hutchinson, 20 Franz Karcher, 21 Samuel L. Kelleher, 15 Peter Marsden, 22 Gerald Noone, 23 Miles A. Nunn, 1 John Oxford, 24 Tony Rachwal, 25 Noel Roberts, 26 Mike Roberts, 27 Maria Ludovica Saccà, 4 Matthew Sanders, 28 Jürg Oliver Straub, 26 Adrian Terry, 29 Dean Thomas, 27 Stephen Toovey, 26 Rodney Townsend, 30 Nikolaos Voulvoulis, 31 and Chris Watts 14 1 Centre for Ecology & Hydrology, Oxford, United Kingdom; 2 Environmental Knowledge Transfer Network, University of Oxford, Oxford, United Kingdom; 3 Centre for Ecology & Hydrology, Wallingford, Oxfordshire, United Kingdom; 4 University of Bologna, Bologna, Italy; 5 Italian National Research Council, Rome, Italy; 6 South West Water, Exeter, United Kingdom; 7 Environment Agency, Wallingford, United Kingdom; 8 University of York, York, United Kingdom; 9 Brunel University, London, United Kingdom; 10 Cranfield University, Cranfield, United Kingdom; 11 Environment Agency, Bristol, United Kingdom; 12 Severn Trent Water, Coventry, United Kingdom; 13 UK Government Department of Health, London, United Kingdom; 14 WCA Environment Ltd., Faringdon, United Kingdom; 15 Manchester Metropolitan University, Manchester, United Kingdom; 16 Northumbrian Water Group (Essex & Suffolk Water), Chelmsford, United Kingdom; 17 United Utilities, Warrington, United Kingdom; 18 Umeå University, Umeå, Sweden; 19 University of Oxford, Oxford, United Kingdom; 20 AstraZeneca, Brixham, Devon, United Kingdom; 21 Health Threats Unit, European Commission, Luxembourg; 22 Drinking Water Inspectorate, London, United Kingdom; 23 Worshipful Company of Water Conservators, London, United Kingdom; 24 Retroscreen Ltd./Barts and The London, Queen Mary’s School of Medicine and Dentistry, London, United Kingdom; 25 Independent Consultant, West Molesey, Surrey, United Kingdom; 26 F. Hoffmann-La Roche Ltd, Basel, Switzerland; 27 UK Government Department for Environment, Food and Rural Affairs, London, United Kingdom; 28 Centre for Environment, Fisheries and Aquaculture Science, Weymouth, United Kingdom; 29 Cambridge Environmental Assessments, Cambridge, United Kingdom; 30 Royal Society of Chemistry, London, United Kingdom; 31 Imperial College London, London, United Kingdom On 3 October 2007, 40 participants with diverse expertise attended the workshop Tamiflu and the Environment: Implications of Use under Pandemic Conditions to assess the potential human health impact and environmental hazards associated with use of Tamiflu during an influenza pandemic. Based on the identification and risk-ranking of knowledge gaps, the consensus was that oseltamivir ethylester-phosphate (OE-P) and oseltamivir carboxylate (OC) were unlikely to pose an eco- toxicologic hazard to freshwater organisms. OC in river water might hasten the generation of OC- resistance in wildfowl, but this possibility seems less likely than the potential disruption that could be posed by OC and other pharmaceuticals to the operation of sewage treatment plants. The work- group members agreed on the following research priorities: a) available data on the ecotoxicology of OE-P and OC should be published; b) risk should be assessed for OC-contaminated river water gen- erating OC-resistant viruses in wildfowl; c) sewage treatment plant functioning due to microbial inhibition by neuraminidase inhibitors and other antimicrobials used during a pandemic should be investigated; and d) realistic worst-case exposure scenarios should be developed. Additional modeling would be useful to identify localized areas within river catchments that might be prone to high pharmaceutical concentrations in sewage treatment plant effluent. Ongoing seasonal use of Tamiflu in Japan offers opportunities for researchers to assess how much OC enters and persists in the aquatic environment. Key words: antiviral, drug, ecotoxicology, influenza, pandemic, pharmaceutical, pollution, sewage treatment plant, Tamiflu. Environ Health Perspect 116:1563–1567 (2008). doi:10.1289/ehp.11310 available via http://dx.doi.org/ [Online 30 May 2008]