Potential toxicity concerns from chemical coagulation treatment of stormwater in the Tahoe basin, California, USA

Ecotoxicol Environ Saf. 2009 Oct;72(7):1933-41. doi: 10.1016/j.ecoenv.2009.04.004. Epub 2009 May 9.


Coagulant dosing of stormwater runoff with polyaluminum chlorides (PACs) is used in numerous waterbodies to improve water clarity, but the potential risks of PACs to aquatic organisms in Lake Tahoe, California are not fully understood. To assess these risks, the USEPA 3-species toxicity test and a non-standard fish test using Japanese medaka (Oryzias latipes) were used to determine the toxicity of PAC-treated and non-treated stormwater samples to aquatic species. Stormwater samples were collected from three sites representing runoff from different urbanized areas in May 2004; samples received coagulant dosing using three different coagulants (JC1720, PAX-XL9, Sumalchlor50) at levels optimized with jar testing. Raw stormwaters were toxic to algae and fathead minnows (mortality). Treatment with coagulants increased toxicity to zooplankton (reproduction) and had no consistent effects on the other toxicity metrics.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aluminum Hydroxide / toxicity*
  • Animals
  • California
  • Cyprinidae / growth & development
  • Environmental Monitoring / methods*
  • Eukaryota / drug effects
  • Eukaryota / growth & development
  • Fresh Water / analysis*
  • Oryzias / growth & development
  • Rain
  • Water Pollutants, Chemical / toxicity*
  • Water Purification / methods*
  • Zooplankton / drug effects
  • Zooplankton / growth & development


  • Water Pollutants, Chemical
  • aluminum oxychloride
  • Aluminum Hydroxide