1. Details have been given of the cancer mortality for twelve occupational groups of males in the City of Sheffield 1926–35 inclusive.
2. Of these groups six show a significantly greater cancer mortality than that experienced by clerks, business and professional men in the City. The six groups are:
(1) Engineers, machinists, cutlers, etc.
(2) Steel foundry and furnace workers, etc.
(3) Grinders and sandblasters.
(4) Workers in precious and non-ferrous metals.
(5) Workers in transport and communication.
(6) Coal miners.
3. The excessive cancer mortality in certain of the sites in the first three of these occupational groups is thought to be definitely associated with their occupation.
4. Cancer of the tonsil is particularly excessive among the steel workers both in the foundry and the shop.
5. Significantly excessive mortality from cancer of the respiratory tract is marked in engineers, foundry workers and grinders and is seen in no other occupational group.
6. Cancer of the alimentary tract is most excessive in foundry and furnace workers. It is suggested that the carcinogenic factor may be hydrocarbons ingested from smoke and fumes.
7. Cancer of the pancreas is excessive only in engineers, etc., and in workers in non-ferrous metals. The theory is advanced that excessive absorption of iron in engineers, and possibly copper in workers in non-ferrous metals, are the respective causes of the findings with regard to cancer of the pancreas in these two occupational groups.
8. Cancer of the skin is significantly excessive in both foundry, etc., workers and engineers, and this is believed to be a direct result of their occupational environment.
9. Tumours of the central nervous system showed no significant variation from the control in any occupational group.
10. The findings in this research indicate that there is a field for further investigation with regard to the carcinogenic properties of iron and copper, particularly with reference to cancer of the pancreas. Some further investigation is re uired with reference to the occupations exposed to the inhalation and ingestion of silica. Is the high cancer rate amongst grinders associated with the silica risk or with the inhalation and ingestion of iron dust from the article ground? On the preventive side the findings support the view that measures should be elaborated to improve the protection of workers from gases, fumes and dust in the iron and steel and allied industries.