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REASSESSMENT OF CYANOTOXIN MIXTURES IN THE 2007 USEPA NATIONAL LAKES ASSESSMENT
Citation:
Loftin, K. A., J. L. Graham, E. D. HILBORN, J. Dietze, J. Dietze, S. Lehmann, M. T. Meyer, AND A. C. Ziegler. REASSESSMENT OF CYANOTOXIN MIXTURES IN THE 2007 USEPA NATIONAL LAKES ASSESSMENT. Presented at 8th National Water Quality Monitoring Conference, Portland, OR, April 30 - May 04, 2012.
Impact/Purpose:
Results indicate the wide range in concentrations and the possibility for co-occurrence of multiple toxin classes and variants in US water bodies. Therefore, routine monitoring for microcystins alone may be insufficient to adequately assess exposure to cyanotoxins
Description:
Microcystins have been the most frequently reported class of cyanotoxins historically. In the 2007 US EPA National Lake Assessment (2007 NLA), the USGS found that microcystins were detected in integrated photic zone samples of approximately 30% of sampled lakes (n= 1028). Based on World Health Organization (WHO) microcystin recreational guidelines, 1% of lakes were categorized as either moderate or high probable health risks based on detected microcystin concentrations. However, health risk assessment by chlorophyll and total cyanobacteria, two other metrics that can be used according to WHO recreational guidelines, gave a significantly different picture with approximately 42% and 27% of lakes being categorized as either moderate or high probable health risk. This demonstrates the difficulty of assessing human health risk based upon single sample results as analytes vary temporally and spatially. Review of the cyanobacteria data also demonstrated that cyanobacteria were present in the 2007 NLA samples capable of producing other classes of cyanotoxins. Frozen, archived 2007 NLA samples were reanalyzed for cylindrospermopsins and saxitoxins by enzyme-linked immunosorbent assay. Preliminary results from the subset analyzed to date show that cylindrospermopsins (n= 659) and saxitoxins (n=678) had a detection frequency of 5% and 8%, respectively. Maximum concentrations for cylindrospermopsins and saxitoxins to date have been 3.5 and 0.38 ug/L, respectively. Results indicate the wide range in concentrations and the possibility for co-occurrence of multiple toxin classes and variants in US water bodies. Therefore, routine monitoring for microcystins alone may be insufficient to adequately assess exposure to cyanotoxins. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.