Mustard gas is known to have mutagenic and carcinogenic effects on animal and human cells. In this report, 1,632 male Japanese who worked in
poison gas factories at some time between the years 1927 and 1945 were studied to determine comparative risk for development of
cancer, the reference population being data on Japanese males overall. The standardized mortality ratio (SMR) for
lung cancer in workers directly and indirectly involved in the production of
mustard gas was significantly elevated. In addition, SMR for
lung cancer in worker who had worked for more than 5 years was also significantly elevated. Thus,
poison gas workers who had engaged in the production of
mustard gas or related work for more than 5 years are a high-risk group for
lung cancer. Under the
cancer preventive program, Nocardia rubra
cell-wall skeleton (
N-CWS) was administered to 146 former
poison gas workers. During a 4.5 year observation period, development of
cancers was found in 7 treated workers and 17 untreated controls. After elimination of the influence of smoking level, a significant suppression of development of
cancers was noted in the
N-CWS-treated workers as compared to the untreated controls. Although the molecular mechanisms of
carcinogenesis in former
poison gas workers remains unclear, our study proposes the possible effect of
biological response modifiers in the prevention of
cancer development in high-risk human subjects.