Sublethal Exposure from Microcystins to Renal Insufficiency Patients in Rio de Janeiro, Brazil Raquel M. Soares, 1 Moucun Yuan, 2 Jerome C. Servaites, 2 Alvimar Delgado, 3 Vale ´ ria F. Magalha ˜ es, 1 Elizabeth D. Hilborn, 4 Wayne W. Carmichael, 2 Sandra M. F. O. Azevedo 1 1 Laboratory of Ecophysiology and Toxicology of Cyanobacteria, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, CCS, Bl-G, Ilha do Funda ˜ o, 21949-900 Rio de Janeiro, Brazil 2 Department of Biological Sciences, Wright State University, Dayton, Ohio, USA 3 Clementino Fraga Filho University Hospital, Nephrology Division, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 4 United States Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Research Triangle Park, North Carolina, USA Received 29 September 2004; revised 3 August 2005; accepted 4 August 2005 ABSTRACT: In November 2001, a cyanobacterial bloom dominated by Microcystis and Anabaena occurred in the Funil Reservoir and the Guandu River, both of which supply drinking water to Rio de Janeiro, Brazil. Using ELISA, microcystins were detected at a concentration of 0.4 g/L in the drinking water, whereas a concentration of 0.32 g/L was detected in activated carbon column–treated water for use at the renal dialysis center of Clementino Fraga Filho Hospital (HUCFF) at the Federal University of Rio de Janeiro. A total of 44 hemodialysis patients who received care at this center were believed to be exposed. Initial ELISA analyses confirmed the presence of serum microcystin concentrations  0.16 ng/ mL in 90% of serum samples collected from these patients. Twelve patients were selected for continued monitoring over the following 2-month period. Serum microcystin concentrations ranged from <0.16 to 0.96 ng/mL during the 57 days after documented exposure. ELISA-positive samples were found through- out the monitoring period, with the highest values detected 1 month after initial exposure. ESI LC/MS analyses indicated microcystins in the serum; however, MS/MS fragmentation patterns typical of micro- cystins were not identified. LC/MS analyses of MMPB for control serum spiked with MCYST-LR. and patient sera revealed a peak at retention time of 8.4 min and a mass of 207 m/z. These peaks are equiva- lent to the peak observed in the MMPB standard analysis. Taken together ELISA, LC/MS, and MMPB Contract grant sponsor: Centers for Excellence Program, Pronex-MCT/ CNPq (to R.M.S.). Contract grant sponsor: Foundation for the Coordination of Higher Education and Graduate Training, CAPES (to R.M.S.). Contract grant sponsor: State Health Secretary of Rio de Janeiro (to R.M.S.). Contract grant sponsor: U.S. EPA, Office of Research and Develop- ment, National Health and Environmental Effects Research Laboratory, Research Triangle Park, NC (to W.W.C.). Contract grant number: 2D-5849-NAEX.  C 2006 Wiley Periodicals, Inc. 95 The views expressed in this report are those of the individual authors and do not necessarily reflect the views and policies of the U.S. Environ- mental Protection Agency. Mention of trade names or commercial prod- ucts does not constitute endorsement or recommendation for use. Correspondence to: R. M. Soares; e-mail: rmsoares@biof.ufrj.br Contract grant sponsor: Brazilian Council for Scientific and Techno- logical Development, CNPq (to R.M.S.). Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.20160  C 2006 Wiley Periodicals, Inc.