Radioactive thorium wastes were found in April 1997 at the former industrial site of 'Orflam-Plast' in the commune of Pargny sur Saulx in the Northeast of France, where industrial activity began in 1934. On this site, between 1934 and 1970, cerium for lighter stones and thorium nitrate were extracted from imported monazite sand, a mineral containing elevated levels of natural radioactivity. We decided to study cancer mortality in the surrounding population. We found an excess of mortality due to lung and bladder cancer in the commune of Pargny sur Saulx and its neighbours, between 1968 and 1994. This excess did not seem to be linked to the river of Saulx which was a possible source of contamination. We conclude that a cancer incidence study of the former workers of this industrial site is necessary in order to investigate the role of natural radioactivity from monazite processing in the risk of cancer mortality among this workforce.