White blood cell DNA adducts were measured in coke workers, local controls and countryside controls using the 32P-postlabelling technique and immunoassay. The methods detected aromatic adducts, including those formed by polycyclic aromatic hydrocarbons. Coke workers are heavily exposed to aromatic compounds, which are also emitted in large amounts into the environment. The two techniques detected a large difference in adduct levels between the coke workers and the countryside controls. The adduct levels in the local controls were substantially higher than those in the countryside controls. As occupational exposure did not account for such a difference, the data suggest that the source of aromatic adducts in local controls is environmental pollution.