Comments on the increased cancer incidence in Denver, USA

The results of a study on the epidemiological evaluation of cancer incidence rates in Denver for the period 1969-1971 in areas of census tracts with measured concentrations of plutonium soil contamination downwind from the Rocky Flats nuclear weapons facility are reviewed. The study had claimed an increasing cancer incidence correlating with increasing concentrations of plutonium in the soil. However, three main aspects of the study had not been fully explored: the validity of the values used to characterise plutonium soil concentrations, the nature of the populations in each area and the typical variation of cancer incidence rates within urban and rural communities. Discussion of these three aspects led to the conclusion that the study did not constitute evidence of the influence of plutonium on cancer incidence rates in Denver. (U.K.)