BACKGROUND People who spend their entire lives in highly industrialized regions are in danger of accumulating trace elements by inhalation as a result of the increased amounts of factory-produced smoke. In order to test the environmentally accumulated trace elements in lungs, lung samples of patients who lived their entire lives in the industrial area of Duisburg were compared with those of patients from the less industrialized areas of Cologne and surroundings. METHODS Five patients were studied who lived in Duisburg and died at 50-68 years but not primarily as a result of lung diseases. From each patient five samples of the left lung were removed at autopsy. Lungs from 18 patients who died in Cologne were also examined. From each of the latter 2 samples were removed from the left lung. All samples were studied by means of neutron activation analysis and the following elements analysed: Co, Fe, Rb, Se, Cr, Cs, Sb, Sc, Zn and Al. The Al-concentration was analysed only in patients aged 50-68 years. RESULTS The values of the non-essential Sc, Al and Cs and of the essential trace elements Co were found to be appreciably higher in the samples from Duisburg than in those from Cologne. Sc in the samples from the highly industrialized area was increased up to a factor of 100, Cs, Al and Co to a factor of 10. In the lungs of adults in Duisburg, aged 50-68 years, the concentration of Sc was more than 1,000 times greater than in lungs of children in Cologne, aged 0-10 years. In all samples from Duisburg, the rare element Eu was detectable by means of neutron activation analysis but could not be detected in a sample from Cologne. CONCLUSIONS It is likely that the different uptakes of trace elements in the lungs depend on correspondingly different concentrations of the elements in the air. The extensive accumulation, especially of the non-essential elements, in the lungs should be an incentive to examine possible detrimental effects on human health in the future. The element Sc which was strikingly accumulated in the lungs and which can be easily measured by neutron activation analysis might be used as a standard for estimating the extent of environmental pollution.