MORTALITY OF WHITE SOUTH-AFRICAN GOLD MINERS

Objectives-This two part study aimed to determine whether there was an excess mortality generally or for some diseases among middle aged whi te South African gold miners on the Witwatersrand and whether the unde rground dust exposure of these miners contributed to the development o f lung cancer, chronic obstructive pulmonary disease (COPD), or ischae mic heart disease (IHD). Methods-A cohort of 4925 white miners in Sout h Africa, born between 1 January 1916 and 31 December 1930 who were al ive and working in the vicinity of Johannesburg on 1 January 1970, the n aged between 39 and 54, was followed up for 20 years by which time 2 032 had died. Most were gold miners (about 87% had worked 85% or more of their shifts in gold mines). Standardised mortality ratios (SMRs) w ere calculated as percentages of the number of deaths observed in the cohort for a condition as stated on the death certificate divided by t he number expected on the basis of concurrent mortality in the referen ce population (the total age specific white male population of South A frica). A case-control analysis was performed for three diseases (lung cancer, COPD, and IHD), the results of which are presented for those miners in the cohort who had spent at least 85% of their service on go ld mines and had worked at least 15% of their shifts underground. Resu lts-The SMR for all causes of death was 129.6%, raised because of exce ss mortality due to the following causes: lung cancer (SMR = 139.8%), IHD (124.1%), COPD (189%) and cirrhosis of the liver(155.3%). Smoking was confirmed to be the main risk factor for lung cancer and COPD alth ough cumulative dust exposure was found to increase the risk of COPD i n conjunction with smoking. No significant risk of lung cancer resulte d from exposure to dust. High blood pressure and smoking were found to increase the risk of IHD, but no association between IHD and the quet elet index (weight/height(2)) was found. Conclusions-The most signific ant and unexpected finding was the 30% increase in the SMR for all cau ses. Very little of this increase could be attributed to mining and th e main factor for this was probably the adoption of an unhealthy lifes tyle by these men (compared with other South African white men) partic ularly smoking (86% were smokers) and alcohol consumption.