We have used a generally applicable 32P-postlabeling assay to examine for the presence of DNA adducts in mussels experimentally exposed to known carcinogens and in mussels collected from sites impacted by wastewaters. Mussels exposed to seawater artificially polluted with 2-aminofluorene showed exclusively one adduct which was identified to be dG-C8-2-aminofluorene. Under the same experimental conditions, Diesel-2 oil did not induce any detectable adducts. When mussel digestive gland DNA was collected and analyzed from one unpolluted site, two moderately impacted sites, and one site heavily impacted by cannery wastewaters, mussel DNA from the unpolluted and only one moderately polluted site showed the presence of 6 to 10 adducts. This indicates they were not related to the pollution. This was further supported by the absence of dose-related adducts. Clear evidence for the presence of pollution-related DNA adducts was, however, found in juvenile mussels collected from an oil refinery site. One major and three minor adducts were detected in these mussels with no adducts detected in juvenile mussels from an unpolluted site.