DNA-DAMAGE INDUCED BY WOOD PRESERVING WASTE EXTRACTS IN-VITRO WITHOUTMETABOLIC-ACTIVATION, AS ASSAYED BY P-32 POSTLABELING

Aqueous wood preserving waste (WPW) extracts were tested for their abi lity to damage DNA in vitro without metabolic activation. Two extracts were prepared from a surface tar and a surface clay soil sample of a WPW site. As assayed by P-32-post-labelling, incubation of DNA with th ese extracts gave rise to highly complex, extract-specific profiles of DNA adducts whose formation depended on the concentration of WPW mate rial. Most of the adducts appeared to be derived from polycyclic aroma tic hydrocarbons (PAHs). Three mg organic WPW residue gave rise to tot al adduct levels of 13.8 (extract 1) and 66.2 (extract 2) DNA modifica tions in 10(7) DNA nucleotides, corresponding to 13.9 and 26.9 modific ations, respectively, per 10 mg of soil. Thus, extract 2 was more acti ve, although the parent residue had a 1.4-times lower PAH content as d etermined by gas chromatography/mass spectrometry (GC/MS). DNA adduct formation presumably was a consequence of (i) free radical reactions, possibly involving semiquinones and oxygen free radicals, and (ii) rea ction of direct-acting electrophiles, derived from metabolism of WPW t oxicants by soil microorganisms. These reactions appeared to be more a ctive in sample 2. The results suggest that ground water at WPW sites contains DNA-reactive compounds posing a cancer hazard to humans. The in vitro DNA adduct assay represents a novel tool to readily assess th is type of hazard and the possible effects of remediation measures.