Analyses of cancer incidence in black gold miners from Southern Africa (1964-79).

As an extension of an earlier study covering the 8-year period 1965-71 (t1), the incidence of cancer in black gold miners over a second 8-year period, 1972-79 (t2) has been investigated. The population again totalled 2.9 million man-years of employment, an average of 363,800 men per year. Of the 903 cancers found in t2, primary liver cancer accounted for 45.4%, oesophageal cancer 19.8%, cancer of the respiratory system 11.2% and bladder cancer 2.7%. Analysis of these 4 common cancers by country or region of origin of the miners confirms for the most part the patterns of incidence found in the earlier survey and consolidated rates are therefore presented for the full 16-year period, 1964-79 (t3). The spatial distribution of primary liver cancer within Mozambique and oesphageal cancer within Transkei have been investigated for the periods t1, t2 and t3 and temporal changes of rate have been examined by individual years from 1964 to 1979. The geographical gradient of incidence for cancer of the oesophagus in Transkei has become less marked during the second period of the survey and the crude incidence rate for primary liver cancer in gold miners from Mozambique has continued to drop throughout the period of the survey.