MICROBIOLOGICAL METHODS FOR THE DETECTION OF MUTAGENS AND CYTOTOXIC COMPONENTS IN WOOD DRYING CONDENSATES FROM DOUGLAS-FIR, RED OAK, SOUTHERN YELLOW PINE, YELLOW-POPLAR AND EASTERN WHITE-PINE

Three microbiological methods of testing for genotoxic chemicals in un characterized wood drying condensates were compared. A commercially su ccessful version of the SOS Chromotest, carried out in microtiter plat es, was compared with the original assay that was modified to be perfo rmed in soft agar overlays. While the microtiter plate version was qua ntitative and could be read by an automated microtiter plate reader, t he soft agar overlay adaptation was at least six times more sensitive with control chemicals, and was more easily carried out. Each version of the test was able to detect cytotoxic effects of wood drying conden sates, but neither test was sensitive enough to routinely detect unkno wn mutagenic components present in wood drying condensates. The Ames S almonella/microsome assay, while more laborious, revealed cytotoxic do se-response relationships with wood drying condensates from yellow pop lar, Douglas fir, white pine, and southern yellow pine; but none of th e condensates was mutagenic in the absence of metabolic activation by mammalian liver enzymes. In the presence of rat liver S-9 extracts, ye llow poplar condensate resulted in the highest single mutagenic respon se, yielding over 5,300 revertants/ml of condensate, but was mutagenic for only one of the four Ames test strains. Douglas fir and white pin e condensates were mutagenic for three of four Ames strains, and exhib ited significant cytotoxicity in the presence and absence of S-9 extra ct. Southern yellow pine condensate was mutagenic for two of the four Ames strains, but was far less mutagenic and cytotoxic than condensate s from Douglas fir or white pine. Condensate from red oak was cytotoxi c, but not mutagenic. The failure of the SOS Chromotest to detect muta genic components in wood drying condensates was unexpected since over 80% of all compounds tested thus far give similar results in both the Ames test and SOS Chromotest. It appears that mutagenic components pre sent in wood drying condensates are poor inducers of DNA repair, and a re not detected by the SOS Chromotest or similar tests that rely on SO S induction.