Epidemiological studies of lung cancer in Japanese mustard gas workers

Until the end of the Second World War, a poison gas manufacturing plant was operating on Okunojima, an island in the Seto Inland Sea. Of the gases produced there, mustard gas and Lewisite were found to be associated with various malignant tumors including lung cancer. The mortality rate for lung cancer in workers directly or indirectly involved in the production of poison gas was significantly higher than that of workers not involved in the production there. Lung cancer caused by poison gas was characterized by the following features: it was found as a central pulmonary carcinoma and was distributed from the upper airway to the hilar region. Squamous cell carcinoma and undifferentiated carcinoma predominated, whereas adenocarcinoma and other types were rare. Retired workers who had been engaged in the manufacture of mustard gas were found to have depressed immunological competence. We therefore started to enhance immunological competence with the use of Nocardia rubra cell wall skeleton (N-CWS) in order to prevent carcinogenesis. To date, no conclusion has been reached on its effectiveness in preventing carcinogenesis, however, we do expect it to be effective.