Investigation of potential toxicity and mutagenicity of distillates from the drying of five species of wood

The Ames test is frequently used to evaluate the potential for adverse human health effects that may be associated with uncharacterized chemical compounds or mixtures of compounds. In this research, the Ames test was used to evaluate aqueous condensates distilled from southern yellow pine, yellow- poplar, red oak, Douglas-fir, and eastern white pine dried at 250?F in a closed laboratory extraction system. The purpose of these tests was to mimic “worst case” conditions of emissions that could be generated during wood drying. Testing of all condensates under increasing concentrations revealed cytotoxic dose-response relationships; but none of the condensates was mutagenic in the absence of metabolic activation by mammalian liver enzymes. In the presence of rat liver microsomal enzymes, condensates from yellow-poplar, Douglas-fir, white pine, and southern yellow pine produced repeatable mutagenic dose-response relationships. Yellow-poplar condensate resulted in the highest single mutagenic response, yielding 5,340 revertants/ml of condensate, but was mutagenic for only 1 of the 4 strains of bacteria used for Ames testing. Douglas-fir and white pine condensates were significantly mutagenic for three of four Ames strains, and exhibited significant cytotoxicity in the presence and absence of rat liver microsomal extracts. Southern yellow pine condensate was mutagenic for two of the four Ames strains, but was far less mutagenic and cytotoxic than condensates from Douglas-fir or white pine. While these laboratory results show that wood-derived condensates contain only weak mutagens, further testing is being done using condensates from actual kiln-drying operations to determine if large volumes of condensate will offset their apparent weak mutagenicity. Further genotoxicity testing and acute and chronic toxicity testing with other species and with condensates taken from kiln-drying operations is needed prior to the formulation of any rational regulatory policy governing the disposition of condensate or vapor emissions.

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