Bull. Environ. Contam. Toxicol. (1995) 54:654-661 9 1995 Springer-Verlag New York Inc. Environmental ~Contamination aand Toxicology 32P-Postlabeling Determination of DNA Adducts in the Earthworm Lumbricus terrestris Exposed to PAH-Contaminated Soils P. Walsh, 1'2 C. El Adlouni, 1 M. J. Mukhopadhyay, ~ G. Viel, 3 D. Nadeau, 1 G. G. Poirier ~ 1Health and Environment Unit, Laval University Research Center (CHUL), 2705 Boul. Laurier, Sainte-Foy, Quebec, G1V 4G2, Canada 2Ministere de I'Environnement et de la Faune du Quebec, Direction du milieu atmosph&ique, 2360 chemin Sainte-Foy, Sainte-Foy, Quebec, G1V 4H2, Canada 3CreaLab, 360 chemin St-Rock Nord, Rock Forest, Quebec J1N 2T3, Canada Received: 27 May 1994/Accepted: 4 December 1994 The importance of the search for reliable biomarkers of DNA damage in environmental health assessment is well recognized by the scientific community and regulatory agencies (IARC 1988; Fowle and Sexton 1992). Among the major biomarkers of DNA damage is the measurement of DNA adducts in target cells or tissues. Up to now, DNA adduct determinations have been directed mostly toward human exposure to toxic substances from the workplace and environment (Hemminki et al. 1988; Talaska et al. 1992). Moreover, techniques for measuring DNA adducts, and in particular the 32p-postlabelling technique, presented also the possibility of determining DNA adduct levels in endogenous animal populations exposed to polluted environments as early warning monitors of ecotoxicity (Dunn et al. 1987; Varanasi et al. 1989; Liu et al. 1991). Soil contamination is becoming a major environmental issue. Therefore, numerous contaminated sites must now be remediated to protect human health and to permit new uses of these sites as agricultural, residential, or industrial areas. Fulfillment of this task requires standardized and sensitive bioassays to carry out site evaluations and to establish scientifically defensible soil quality criteria. To that effect, the earthworm appears to be one of the best organisms for use in soil toxicity evaluation (Bouch6 1992). Earthworms are probably the most relevant soil species, representing 60 to 80% of the total animal biomass in soil (Rida 1994). Present soil bioassays focus mostly on plant species with end points like seed germination, root elongation, seedling growth and seedling emergence, and on acute toxicity evaluation (re: LC 50) on the earthworm Eiseniafetida (OECD 1984; Keddy et al. 1992). As yet, a standardized soil invertebrate test for teratogenic or mutagenic end points has not been developed (Sheppard et al. 1992). In this paper, we report the feasibility of DNA adduct determination by 32p-postlabelling in the earthworm Lumbricus terrestris as a way to detect the presence of genotoxic substances in soils. Correspondence to." G. G. Poirier 654