Investigation of acute toxicity of distillates from five species of wood for fathead minnows

Condensates prepared for Douglas-fir, red oak, eastern-white pine, southern yellow pine, and yellow-poplar by drying at 25O?F in a closed laboratory extraction system were tested for acute toxicity using the fathead minnow (Pimephales promelas) in a U.S. EPA-recommended test system. The purpose of testing was to expose minnows to “worst case” emissions that could be generated during wood drying, and to determine if such condensates posed a toxicity threat to fish. Condensates were mixed in two-fold concentrations (0.8% to 13% vol./vol.) with well water routinely used for the rearing of rainbow trout and Atlantic salmon. Testing of condensates from all five wood species over a 24-hour period revealed significant toxicity with positive dose-response relationships. In the case of Douglas-fir and southern yellow pine condensates, the concentration resulting in 50 percent mortality (LC50) was 9.2 percent. The LC50 for red oak condensate was 4.6 percent; for eastern white pine condensate, 2 percent; and for yellow-poplar condensate, 2.5 percent. For Douglas-fir and red oak condensates, a significant drop in the pH of the test solution to below 5.5 was likely responsible for mortalities observed. In the cases of eastern white pine, southern yellow pine, and yellow-poplar condensates, however, mortalities were observed at pH values between 5.5 and 7.2. These results suggest that condensates distilled from eastern white pine, southern yellow pine, and yellow-poplar contain components that are acutely toxic for fish at moderately acidic pH. In contrast, toxicity associated with Douglas-fir and red oak condensates was most likely a result of the acidity of the condensates themselves, rather than simply being an effect of one or more specific toxic components.

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